Congenital heart disease in the adult - detailed technical article
- Classification and nomenclature
- Cyanosis: a multisystem disorder Valve and outflow tract lesions
- Atrial septal defects
- Ventricular septal defects
- Arterial disorders
- Systemic venous anomalies
- Pulmonary venous anomalies
- Transposition complexes
- Hearts with univentricular AV connection
- Hypoplastic left heart syndrome (HLHS)
- Pregnancy and contraception in congenital heart disease
- Bacterial endocarditis
- Further reading
Adults with congenital heart disease are a growing population, and now outnumber children with congenital heart disease in the UK. Many adult survivors have complex, surgically-altered hearts and circulations that reflect the surgical and interventional practices of the preceding two decades. For some, their long term outlook is unknown and they remain at lifelong risk of complications that may require further intervention. The organization of services to provide specialist care is key to their long term survival.
The classification and description of complex congenital heart disease can appear intimidating, but should be easily understood by using a simple physiological approach that takes into account whether a condition is cyanotic or acyanotic, whether there is a shunt, and the implications of the morphology for pulmonary blood flow.
The description of the congenitally malformed heart is aided by a sequential segmental analysis of the relationship of the three cardiac segments, which makes it possible to understand and describe how a complex heart is connected. The three segments to be considered are: (1) The atria; (2) The ventricles; (3) The great vessels. The next step is to describe each segment and its relation to the next segment:
- ◆ Situs solitus is the usual arrangement of the atria (and other asymmetrical structures)
- ◆ Atrial situs inversus is the mirror-image arrangement of the atria
- ◆ Isomerism describes abnormal symmetry of paired structures that usually show laterality – eg bilateral morphological left atria in left atrial isomerism.
- How the atria connect to the ventricles, ie the atrioventricular connections, and the morphology of the atrioventricular valves:
- ◆ Atrioventricular concordance, which is the normal arrangement, with the right atrium connecting to the right ventricle via a tricuspid valve, and the left atrium connecting to the left ventricle via a mitral valve
- ◆ Atrioventricular discordance, which is abnormal: the right atrium connects to the left ventricle via a mitral valve, and the left atrium connects to the right ventricle via a tricuspid valve
- How the ventricles connect to the great vessels, ie the ventriculo-arterial connections, and the morphology of the great arteries:
- ◆ Ventriculo-arterial concordance, which is the normal arrangement, with the right ventricle connecting to the pulmonary artery via a pulmonary valve, and the left ventricle connecting to the aorta via an aortic valve
- ◆ Ventriculo-arterial discordance, which is abnormal: the right ventricle connects to the aorta via an aortic valve, and the left ventricle connects to the pulmonary artery via a pulmonary valve.
The growing number of adult survivors of congenital heart disease will encounter medical staff from all areas of medicine and surgery. It is therefore important that all doctors have an understanding of the principles of congenital heart disease and enough knowledge to know when to refer such patients to a specialist centre.
As a result of advances in paediatric cardiac surgery and intervention, the outlook for the approximately 8 per 1000 babies born with congenital heart disease has changed dramatically in the last half century. Fifty years ago, 70% of children born with congenital heart disease died before their 10th birthday; now more than 80% survive to adulthood and there are more adults than children living in the United Kingdom with congenital heart disease.
Despite such advances, only those with the simplest conditions, e.g. isolated secundum atrial septal defect or anomalous pulmonary venous drainage successfully repaired in childhood, may be considered cured of their heart disease. Most patients need continued specialist follow-up since they have residual lesions that may progress over many years and require timely intervention.
Surgical techniques continually evolve, creating new populations with different, surgically modified conditions and long-term outcomes. Careful follow-up is therefore crucial, not only to provide high standards of clinical care, but also to provide feedback about late results in order to inform initial management in infancy. As a result of such long-term follow-up information, the operation of choice for transposition of the great arteries is now the arterial switch, because of the late problems encountered in patients who had undergone interatrial repair with the Senning or Mustard operations.
Surgical advances mean that patients with new surgically modified conditions are reaching adulthood. Their outlook and the complications they may face are not known, so lifelong specialist surveillance is important. Survivors of the hypoplastic left heart syndrome will be the largest such new group reaching the adult clinics in the next decade.
Classification and nomenclature
The classification and description of complex congenital heart disease can appear intimidating. Nonetheless, a grasp of the basic principles is important to understand the anatomy and pathophysiology of congenital cardiac conditions. A simple physiological approach to classifying congenital heart disease takes into account whether a condition is cyanotic or acyanotic, whether there is a shunt, and the implications of the morphology for pulmonary blood flow (Table 1).
|Table 1 Classification of congenital heart disease|
|No shunt||Left-to-right shunt||Eisenmenger syndrome||High pulmonary blood flow||Normal or low pulmonary blood flow|
|Level of lesion||Example of specific lesion||Level of shunt||Example of specific lesion||Level of shunt||Example of specific lesion||Level of shunt||Example of specific lesion||Level of shunt||Example of specific lesion|
|R inflow||Ebstein’s anomaly||Atrial||
||Atrial||Large ASD (uncommon cause)||Atrial||Large ASD||Atrial, with obstruction to pulmonary blood flow||
||Ventricular||VSD||Ventricular||Large VSD||Ventricular||Large VSD||
||Arterial||Large PDA Aortopulmonery window||Arterial||Large PDA Aortopulmonery window||Extra cardiac||Pulmonary AVM|
||Multiple||AVSD||Multiple||Large AVSD||Multiple||Large AVSD|
ASD, atrial septal defect; AVSD, atriventricular septal defect; LA, left atrium; PAPVD, partial anomalous pulmonary venous drainage; SVC, superior vena cava; VSD, ventricular septal defect.
The description of the congenitally malformed heart is aided by a segmental approach, which makes it possible to understand and describe how a complex heart is connected. Any heart can be described by considering it as three segments (the atrial chambers, the ventricular mass, and the great arteries) and describing in a sequential manner how each segment is arranged and connected to the next segment (Bullet list 1)
Bullet list 1 Segmental analysis
- ◆ The arrangement of the atria (situs) is described first—see text below for discussion of abnormal situs/isomerism
- ◆ The atrioventricular (AV) connections and the morphology of the AV valves are described:
- • AV concordance—normal; the RA connects to the RV via a tricuspid valve; the LA connects to the LV via a mitral valve
- • AV discordance—abnormal; the RA connects to the LV via a mitral valve; the LA connects to the RV via a tricuspid valve
- ◆ The ventriculoarterial (VA) connections and the morphology of the great arteries are described:
- • VA concordance—normal; the RV connects to the PA via a pulmonary valve, the LV connects to the aorta via an aortic valve
- • VA discordance—abnormal; the RV connects to the aorta via an aortic valve, the LV connects to the PA via a pulmonary valve
- ◆ Associated malformations are then described
Situs solitus is the usual arrangement of asymmetrical structures, i.e. morphological left atrium on the left and right atrium on the right; morphological left main bronchus on the left and right main bronchus on the right; stomach on the left, liver on the right. Situs inversus is the mirror image arrangement of these structures.
Isomerism describes abnormal symmetry of paired structures that usually show laterality, as shown in Table 2. The presence of isomerism of the atrial appendages should alert the physician to the coexistence of complex associated lesions, including a variety of abnormalities of venous connections that may cause technical difficulties at cardiac catheterization and permanent pacemaker insertion. Right isomerism is commoner in males and left isomerism in females. Survival to adulthood with right isomerism is uncommon because of associated asplenia and severe cyanotic heart disease, including obstructed anomalous pulmonary venous drainage (the pulmonary venous confluence is a left atrial structure). The lesions associated with left isomerism tend to produce left-to-right shunts and little if any cyanosis.
|Table 2 Diagnosis of atrial arrangement|
|Atrial situs solitus (normal)||Atrial situs inversus||Right isomerism||Left isomerism|
||Bilateral morphological RA, extensive pectinate muscles||Bilateral morphological LA, pectinate muscles confined to appendages|
||Mirror image||Bilateral broad based RA appendages||Bilateral long narrow LA appendages|
|Sinus node||Single, R-sided||Single, L-sided||Bilateral||Absent|
||Bilateral trilobed lungs||
||Mirror image||Bilateral short morphological R bronchi||Bilateral long morphological L bronchi|
||Normal or mirror image||
IVC, inferior vena cava; L, left; LA, left atrium; R right; RA, right atrium; SVC, superior vena cava.
a Readily identified on transoesophageal echocardiography.
b Since bronchopulmonary situs nearly always follows atrial situs, atrial situs can be inferred from the chest radiograph.
c Echocardiography shows the intra-abdominal relations of the great vessels. In left isomerism, there is usually interruption of the IVC, and the abdominal venous return connects to the heart via a (right-sided) azygos or (left-sided) hemiazygos vein. The hepatic veins can be identified draining separately into the atria.
Cyanosis: a multisystem disorder
Cyanosis occurs as a result of a right-to-left shunt. Cyanotic heart disease is a multisystem disorder; its manifestations are listed in Table 3.
|Table 3 Complications of cyanotic congenital heart disease|
||2° to paradoxical embolism|
||→High risk of iatrogenic renal failure|
|Bilirubin kinetics||↑ Haem breakdown||→Pigment gallstones|
|Digits and long bones||
|Dental||Gingival hypertrophy||→↑ Risk of endocarditis|
CVA, cardiovascular accident.
Chronic hypoxia is the stimulus to the increased red blood cell mass and high haematocrit found in cyanotic heart disease. This physiological response increases the oxygen-carrying capacity of the blood and may improve tissue oxygenation sufficiently to reach a new equilibrium at a higher haematocrit. However, adaptive failure occurs if the increase in blood viscosity brought about by the high haematocrit impairs oxygen delivery and negates the beneficial effects of erythrocytosis.
The secondary erythrocytosis of cyanotic heart disease is a physiological response, often associated with thrombocytopenia. It is fundamentally different from the generaliszed increase in all haemopoietic stem cell lines found in the malignant disease, polycythaemia rubra vera. Failure to differentiate between these two phenomena has contributed to the persistent mismanagement of erythrocytosis in cyanotic heart disease. Three misconceptions lead to inappropriate venesection in cyanotic heart disease:
- ◆ ‘Volume replacement is not necessary’—if venesection is performed without simultaneous volume replacement, the sudden fall in systemic blood flow, oxygen delivery and cerebral perfusion may result in cardiovascular collapse. Simultaneous infusion of an equal volume of 0.9% saline or colloid should be given.
- ◆ ‘Venesection is performed to reduce the risk of stroke’—the risk of stroke in adults with cyanotic heart disease does not relate to the haematocrit, but rather to microcytosis and iron deficiency brought on by injudicious venesection.
- ◆ ‘Venesection should be done routinely to keep the haematocrit below 65%’—the only indication for venesection is for the temporary relief of symptoms of hyperviscosity in hydrated, iron-replete individuals with haematocrit greater than 60 to 65% (Bullet list 2 and Table 4).
Bullet list 2 Symptoms of hyperviscosity
- ◆ Headache
- ◆ Faint, dizzy, light-headed
- ◆ Depressed mentation, sense of distance
- ◆ Blurred vision, amaurosis fugax
- ◆ Paraesthesiae
- ◆ Tinnitus
- ◆ Fatigue, lethargy
- ◆ Myalgia, muscle weakness
- ◆ Chest and abdominal pain
- ◆ Restless legs
Any dehydration should be corrected before assessing the need for venesection, and if the patient does not gain symptomatic improvement then further venesection is unlikely to be beneficial. Some patients reach a stable equilibrium with a haematocrit above 70%; venesection is not indicated if there are no symptoms of hyperviscosity, the only exception being the preoperative patient with thrombocytopenia and a high haematocrit, when venesection may cause a temporary rise in platelet count and a reduction in perioperative bleeding.
Microcytic, hypochromic iron-deficient erythrocytes require a higher haematocrit and therefore higher blood viscosity to achieve the same oxygen-carrying capacity as iron-replete cells. Iron deficiency also causes muscle weakness and myalgia, independent of its effect on blood viscosity. If standard doses of iron supplements are given, uncontrolled erythropoiesis occurs and the haematocrit rises rapidly, resulting in a cycle of excessive venesection and iron deficiency leaving the patient symptomatic from both haematocrit-induced and iron-deficiency-induced hyperviscosity. Low dose iron replacement (e.g. ferrous sulphate 200 mg/day) combined with close monitoring of the blood count so that iron therapy is withdrawn as soon as the haematocrit rises should allow the gradual recovery of iron stores and the avoidance of counterproductive venesection and further iron deficiency. Hydroxyurea is an antitumour agent that may have a role in suppressing the erythrocytotic response to iron therapy in patients with a high haematocrit, but it also causes thrombocytopenia and neutropenia and so should be used with caution.
Menorrhagia is common in women with cyanotic heart disease and may be sufficient to cause iron-deficiency anaemia. It may be difficult to manage, the combined oral contraceptive pill being contraindicated because of the prothrombotic effects of the oestrogen it contains, and tranexamic acid may similarly be associated with thrombosis. Norethisterone may provide short-term relief. Progestogen-only contraceptives have unpredictable effects on menstruation: a subdermal implant (e.g. Implanon) is safe and causes oligoamenorrhoea in some women. Mirena IUS is a progestogen-eluting intrauterine device that causes oligoamenorrhoea in most women, but it is not generally recommended in those with cyanotic heart disease or who have not undergone previous vaginal delivery because insertion may a vasovagal response and cardiovascular collapse. If menorrhagia is due to uterine fibroids, catheter embolization of the feeding uterine artery is safe and may be successful.
|Table 4 Guidelines for venesection in adults with cyanotic heart disease|
|Symptoms of hyperviscosity||Haematocrit and serum iron||Action|
|No||Any||Venesection not indicated|
||Isovolumic venesection (400–500 ml)|
|Yes||Hct <65%, iron deficient||
Disorders of coagulation and blood vessels
It is poorly understood why patients with cyanotic disease are at increased risk of haemorrhage and thrombosis. There is often a mild thrombocytopenia that may be due partly to shortened platelet survival time, and the large multimeric forms of von Willebrand factor and other clotting factors may be depleted. Coagulation testing may yield spurious results in patients with haematocrit over 55% unless the amount of citrate anticoagulant is reduced.
Bleeding may be minor and mucocutaneous, but major haemorrhage may occur during surgery, or from the lungs. Pulmonary artery thrombosis is discussed below (see ‘Eisenmenger syndrome: defects with secondary pulmonary vascular disease’, below). Interestingly, systemic arterial atherosclerosis is exceedingly rare in the cyanotic population, perhaps because of a combination of thrombocytopenia, upregulated nitric oxide, hyperbilirubinaemia, and hypocholesterolaemia.
Other complications of cyanotic heart disease
The risk of is increased in cyanotic heart disease, with independent risk factors being intravenous lines, arterial hypertension, atrial fibrillation, and the strongest risk factor, red cell microcytosis.
Right-to-left shunting creates a risk of paradoxical embolism causing stroke and cerebral abscess, as well as air emboli from venous lines not fitted with filters. Patients who require transvenous pacing should be anticoagulated with warfarin to prevent paradoxical thromboembolism from pacing leads.
Despite the high incidence of hyperuricaemia, attacks of acute gout are uncommon and asymptomatic hyperuricaemia does not require treatment. Acute attacks should be treated with colchicine, avoiding nonsteroidal anti-inflammatory agents (NSAIDs) because of their detrimental effects on haemostasis and renal function. As in primary hyperuricaemia, allopurinol is useful in preventing recurrence. The renal abnormalities outlined in Table 3 are frequently not associated with abnormal baseline renal function. However, renal failure may be precipitated by hypotension and dehydration, especially in combination with radiographic contrast media, NSAIDs or aminoglycoside antibiotics. Acne is a common complaint in adolescents and adults with cyanotic disease and may be widespread and psychologically debilitating. When severe it may also increase the risk of bacteraemia and endocarditis.
Digital clubbing is almost universal in cyanotic heart disease, and some degree of hypertrophic osteoarthropathy of the long bones may occur in up to one-third of patients. Symptoms include aching and tenderness of the long bones of the forearms and legs. There is oedema and cellular infiltration, causing lifting of the periosteum that is visible radiographically, with new bone formation and resorption. Localized activation of endothelial cells by an abnormal platelet population, with the ensuing release of fibroblast growth factors, may play a central role in the pathogenesis of both phenomena.
Cyanotic patients become more hypoxic during air travel as the partial pressure of oxygen in a pressurized aircraft is lower than that at sea level. However, such travel seems to be well tolerated and supplemental oxygen should not normally be necessary. Travellers should be warned to avoid dehydration and to plan their journeys to avoid having to carry baggage for long distances within large airports.
Eisenmenger syndrome: defects with secondary pulmonary vascular disease
Eisenmenger syndrome is a condition where there is pulmonary hypertension at systemic level. It occurs when a communication between the systemic and pulmonary circulations results in high pulmonary blood flow and the development of high pulmonary vascular resistance, which in turn results in a reversed or bidirectional shunt. The communication may be at atrial, ventricular or arterial levels.
Surgery in infancy should usually prevent the development of this irreversible syndrome, but when patients do present their management is dependent on a good understanding of their condition.
Symptoms of breathlessness relate to the degree of hypoxia; many patients feel worse in hot weather or after a hot bath because the resulting systemic vasodilatation is not accompanied by a reduction in pulmonary vascular resistance, so the right-to-left shunt is enhanced and they become more hypoxic. Exercise-induced syncope may occur, and is exacerbated by hot weather and dehydration. Haemoptysis is common and may be fatal.
Whatever the underlying defect, some examination findings are shared. Patients are cyanosed and clubbed and may be plethoric. There is a right ventricular heave and the pulmonary component of the second heart sound is palpable and loud. A pulmonary ejection click and pulmonary regurgitation may be audible. A soft systolic flow murmur may be heard from the dilated pulmonary artery. No systolic murmur can be heard from the lesion responsible for the pulmonary vascular disease since the chambers on both sides of the lesion are at equal pressure.
It is frequently possible to distinguish between the common lesions associated with the Eisenmenger syndrome on clinical grounds. The patient with an Eisenmenger duct has differential cyanosis and clubbing since fully saturated blood from the left ventricle supplies the aortic arch and its branches before mixing occurs with desaturated pulmonary arterial blood via the patent duct. The right hand may therefore be pink with no clubbing, the left may be slightly more cyanosed because of the origin of the left subclavian artery opposite the duct, and the toes are more deeply cyanosed and clubbed. The second heart sound may be closely or normally split. In contrast, cyanosis and clubbing is uniform when the right-to-left shunt occurs at atrial, ventricular or ascending aortic (as in truncus arteriosus or aortopulmonary window) levels. The second sound is single in ventricular septal defect (VSD), AV septal defect (AVSD), and truncus, but may be split in an atrial septal defect (ASD).
The chest radiograph shows a dilated pulmonary trunk because of high pulmonary blood flow in earlier life, but reduced blood flow as pulmonary vascular resistance rose means that the lung fields are oligaemic. Unless cardiac failure intervenes, the heart size is usually normal, the effects of volume overload having regressed as pulmonary vascular resistance increased and the left-to-right shunt diminished and disappeared.
The ECG shows P pulmonale and biventricular hypertrophy. The echocardiogram should establish the site of the shunt and allow an estimation of pulmonary arterial pressure and ventricular function.
Cardiopulmonary exercise testing may be used with caution: patients with Eisenmenger syndrome are among the most limited of those with congenital heart disease and maximal exercise testing may induce potentially fatal syncope. The less strenuous but still objective 6-min walk test is the preferable measure of exercise capacity in these patients.
Multislice CT scanning demonstrates the hypertensive pulmonary vasculature and any collateral vessels. It is also the investigation of choice to show in situ pulmonary thrombus and pulmonary artery aneurysms, and to demonstrate the site of any pulmonary haemorrhage. Care should be taken to avoid contrast-induced nephropathy by ensuring adequate hydration.
Cardiac catheterization is unnecessary and potentially dangerous for patients with established pulmonary vascular disease. The only indication is for those patients whose pulmonary vascular disease is suspected to be reversible and who would be considered for surgical repair if reversibility can be confirmed. This situation is rarely encountered in the adult population.
Histologically, pulmonary vascular disease progresses from medial hypertrophy through intimal proliferation with migration of smooth muscle cells, to progressive fibrosis and obliteration, dilatation, the development of angiomata and finally fibrinoid necrosis. Those who have developed fibrotic and obliterative changes are likely to have irreversible pulmonary vascular disease. Routine lung biopsy is not recommended; it carries a high risk in the pulmonary hypertensive adult and is unlikely to show reversible pathology. In addition, thoracotomy scars from open lung biopsy are a relative contraindication to heart–lung transplantation.
Outcome and complications
Survival into adulthood with Eisenmenger syndrome is common. Life expectancy may be around 20 years less than for the general population, but this is markedly better than for those with idiopathic pulmonary arterial hypertension. Markers of poorer prognosis include complex anatomy and physiology, decline in functional class, and the development of heart failure and clinical arrhythmia. Serum uric acid increases with disease progression and may also be used as a long term predictor of mortality.
The patient with Eisenmenger syndrome is prone to all the complications of cyanotic heart disease discussed above.
Haemoptysis is usually due to rupture of small hypertensive intrapulmonary vessels, or more rarely to thrombosis in situ and pulmonary infarction. All patients should be admitted to hospital and the systemic pressure kept low by bed rest and β-blockade; the pulmonary artery pressure being the same as that measured in the brachial artery. NSAIDs should be stopped and vasodilators should not be given. If the haemoptysis is massive, diamorphine should be administered, fresh frozen plasma or cryoprecipitate may be given, and consideration should be given to selectively intubating the nonbleeding lung. Bronchoscopy has no role and may worsen the haemorrhage.
In situ thrombosis in the dilated pulmonary arteries of adults with Eisenmenger syndrome is common (prevalence of 20–30%) and relates to the degree of cyanosis. It is best detected and quantified using multislice CT scanning. Anticoagulation of any sort has not been shown to resolve such thrombus, and patients are at risk of pulmonary embolic episodes. Warfarin may increase the risk of bleeding while failing to reduce the thrombus, and aspirin should be avoided as it may exacerbate haemorrhage associated with thrombocytopenia.
Right ventricular failure may be precipitated by atrial arrhythmia and usually occurs after the age of 30 years. Decline may be heralded by the onset of right ventricular failure, supraventricular arrhythmia and haemoptysis. Death may be sudden and due to arrhythmia or massive haemoptysis. In some patients death follows progressive hypoxia terminating in bradycardia and asystole from which they cannot be resuscitated.
Intercurrent illness and noncardiac surgery may pose major risks. The latter is particularly dangerous when carried out without the benefit of expert cardiology, anaesthetic and perioperative care. A sound understanding of the pathophysiology is vital (Bullet list 3
Bullet list 3 Checklist for patients at high riska of iatrogenic complications during the perioperative period or during intercurrent illness
- ◆ Maintain hydration—intravenous fluids (via air filter if cyanotic to avoid the risk of paradoxical embolism) when nil by mouth
- ◆ Maintain haemoglobin commensurate with degree of cyanosis to optimise oxygen carrying capacity
- ◆ Avoid vasodilator agents—especially at induction of anaesthesia
- ◆ Protect the kidneys—maintain hydration, avoid nephrotoxic agents (NSAIDs, aminoglycosides), use minimal volumes of contrast agents.
a Patients at high risk include those who are cyanotic and those with Eisenmenger syndrome or Fontan circulation.
Until recently, treatment has been palliative and symptom led, directed at avoiding iatrogenic and natural complications. Although this approach is still the mainstay of treatment, selective pulmonary vasodilators including phosphodiesterase inhibitors (eg sildenafil) and endothelin receptor antagonists may improve outcome. They have been shown to improve outcome in other forms of pulmonary hypertension, and data from initial short-term randomized controlled studies of bosentan suggests that it may be beneficial in Eisenmenger syndrome.
Pregnancy and contraception
Pregnancy carries a particularly high risk, 25–40% maternal mortality. Pregnancy and contraception in congenital heart disease are discussed below, and in heart disease in general in: Heart Disease in Pregnancy. All women with pulmonary hypertension of any cause should be counselled of the risks and given access to safe, effective contraception. If a woman with Eisenmenger syndrome does become pregnant and chooses not to have a termination, she should be referred to a specialist centre.
Valve and outflow tract lesions
Isolated pulmonary valve stenosis
Isolated pulmonary stenosis is common, occurring in up to 10% of patients with congenital heart disease. There is usually fusion of the valve cusps leading to a doming appearance. Syndromic associations are not unusual and include Noonan’s, Williams’s and Alagille’s syndromes.
Significant pulmonary stenosis results in right ventricular hypertrophy and high right-sided pressures; right-to-left shunting causing cyanosis may occur if there is a coexistent ASD or patent foramen ovale.
Pulmonary stenosis is a better-tolerated lesion than aortic stenosis, with an excellent survival. Severe pulmonary stenosis usually presents in childhood, either as an asymptomatic murmur, or with failure to thrive, chest pain, dyspnoea, or cyanosis.
Patients are acyanotic unless there is an interatrial communication, in which case cyanosis is severe. The venous pressure is raised only if the right ventricle has begun to fail and there is tricuspid regurgitation. There may be a right ventricular heave. The pulmonary component of the second heart sound is soft and there is a pulmonary ejection systolic murmur. An early diastolic murmur may also be present if there is coexistent pulmonary regurgitation.
The ECG may demonstrate right ventricular hypertrophy. This regresses after relief of the stenosis. The chest radiograph reveals poststenotic dilation of the proximal pulmonary artery, and the lung fields may be oligaemic if the pulmonary stenosis is severe.
Transthoracic echocardiography confirms the diagnosis and allows functional assessment of the severity of pulmonary stenosis and regurgitation as well as right ventricular hypertrophy, dilatation, and function.
Adults with trivial (<20 mmHg) pulmonary stenosis do not require regular follow-up, since progression is unlikely. Approximately 20% of adults with mild stenosis (<50 mmHg) may progress and ultimately require intervention, and most of those with a peak pulmonary valve gradient greater than 50mmHg require intervention.
Balloon pulmonary valvotomy is the treatment of choice, unless associated anomalies require a surgical approach. Valvotomy is usually successful and it is uncommon for stenosis to recur, however, the procedure invariably results in a degree of pulmonary regurgitation and so long-term follow-up is required.
Abnormally placed muscle bands cause either infundibular obstruction or—if placed more inferiorly—subinfundibular obstruction and a double-chambered right ventricle. The degree of obstruction may be mild in childhood, but progresses in adult life and causes symptoms as the right ventricle hypertrophies. A perimembranous VSD usually coexists and may close spontaneously. Treatment is by surgical resection of the obstructing muscle bands.
This rare, complex defect of the tricuspid valve occurs in 1 in 20 000 live births and affects both sexes equally. The risk may be increased by maternal exposure to lithium during the first trimester. Ebstein’s anomaly is characterized by a spectrum of features:
- ◆ Adherence of the tricuspid valve leaflets to the underlying myocardium due to failure of delamination in fetal life, resulting in apical displacement of the functional tricuspid valve tethering, redundancy, and fenestrations of the valve leaflets
- ◆ Apical displacement of the tricuspid valve annulus:
- • As a result of the failure of delamination the septal and posterior (mural) leaflets insert further into the body of the right ventricle than in the normal heart (in which the mitral and tricuspid valves are offset so that the tricuspid valve is displaced up to 1.5 cm towards the right ventricular apex).
- • the ‘atrialized’ portion of the right ventricle is often thinner walled than the functional right ventricle due to congenital partial absence of the myocardium
- • as a result the functional size of the right ventricle is reduced and of the right atrium increased
- ◆ Dilation of the functional right atrium
- ◆ Dilatation of the true tricuspid valve annulus at the AV junction
This combination of features usually results in tricuspid regurgitation (or very rarely stenosis) and right heart dilation, providing a substrate for atrial and ventricular arrhythmias.
A patent foramen ovale or ASD is present in most cases, and allows cyanosis to develop as the disease progresses and of right-to-left shunting occurs. Left heart abnormalities occur as a consequence of alterations in left ventricular geometry due to leftwards displacement of the interventricular septum; e.g. mitral valve prolapse may occur as result of relatively long chordae in a left ventricle of reduced cavity size. Coexistent Wolfe–Parkinson–White syndrome, usually with single or multiple right-sided pathways, occurs in 20% of patients.
Ebstein’s anomaly may also form part of other complex congenital lesions, including pulmonary stenosis and atresia and tetralogy of Fallot. When it coexists with congenitally corrected transposition of the great arteries, the tricuspid valve is the systemic AV valve.
Clinical presentation and course
There is a broad spectrum of severity, ranging from intrauterine or neonatal death to presentation in late adulthood. Mortality, both with and without surgery, is influenced by age at presentation, the condition of the tricuspid valve, the cardiac rhythm, and the functional capacity of the right ventricle, including the severity of right ventricular outflow tract obstruction and the size of the right atrium in relation to the other cardiac chambers.
Arrhythmia is the commonest mode of initial presentation in adult life; presentation earlier in life is usually associated with severe disease and additional cardiac lesions.
Cyanosis may develop in adulthood if there is an associated ASD or patent foramen ovale; as the right ventricular filling pressure increases there is a parallel rise in right atrial pressure, and a right-to-left interatrial shunt is established. These patients are at risk of paradoxical embolism, but the risk of endocarditis is low because the tricuspid regurgitant jet is of low velocity.
Heart failure may intervene as a result of the combination of severe tricuspid regurgitation and the onset of atrial fibrillation or flutter. These atrial arrhythmias may be particularly troublesome if a coexistent accessory pathway allows a rapid ventricular response rate. The onset of atrial fibrillation is a predictor of death within 5 years, and may account for the increased death rate in the fifth decade.
The patient may be acyanotic or cyanosed and clubbed. Even when tricuspid regurgitation is severe the jugular venous pressure may not be particularly high or the v wave prominent because of the capacity of the right atrium and thin-walled atrialized right ventricle to accommodate the low pressure regurgitant volume. Once right ventricular failure develops the jugular venous pressure rises further and the a and v waves become more prominent. In the uncommon situation of tricuspid stenosis, the a wave is increased and may be giant. The first heart sound is widely split with a delayed tricuspid component, due to the extra distance that the large anterior leaflet has to travel to reach the limit of its systolic excursion. The second heart sound may be single because low pressure in the right ventricular outflow tract renders the pulmonary component inaudible, or it may be widely split reflecting right bundle branch block. Third or fourth ventricular filling sounds may be present. The systolic murmur of tricuspid regurgitation varies from inaudible to loud enough to generate a thrill, but is classically decrescendo and scratchy. Once the right ventricle begins to fail and the venous pressure rises, hepatomegaly, ascites and peripheral oedema are common.
The chest radiograph is characteristic. The ECG typically shows a superior axis and right atrial enlargement, with or without right bundle branch block. The p wave may be peaked and the PR interval prolonged, reflecting the prolonged conduction in the large right atrium, or there may be evidence of pre-excitation. Right bundle branch block may occur due to abnormal activation and conduction in the atrialized right ventricle.
Echocardiography establishes the diagnosis, severity, and associated abnormalities of Ebstein anomaly. The atrialized and functional portions of the right ventricle can be identified, as can the precise attachments and degree of tethering of the anterior leaflet of the tricuspid valve. Echocardiography is the investigation of choice in planning surgical intervention, tethering and restricted motion of the anterior leaflet and a small right ventricle being strong predictors of the need for tricuspid valve replacement rather than repair. Cardiac catheterization is only necessary if specific haemodynamic questions remain after noninvasive assessment.
Cardiopulmonary exercise testing is invaluable in assessing functional capacity when planning timing of surgery.
Patients should be anticoagulated when atrial arrhythmias develop, particularly if there is an ASD. If re-entry tachycardias cannot be controlled with antiarrhythmic drugs, radiofrequency ablation of accessory pathways may be performed. However, ablation may be made difficult by the size and abnormal shape of the right atrium and abnormal position of the accessory pathway or pathways.
Symptomatic patients should be assessed for surgery. In addition, the asymptomatic patient with severe tricuspid regurgitation and normal cardiopulmonary exercise tolerance should be considered for repair if right ventricular function has begun to deteriorate. The timing of surgery may be difficult to decide in the adult patient, even in the few centres with reasonable experience. Once the patient has developed overt right heart failure with a raised venous pressure, hepatomegaly, ascites, and atrial fibrillation, ventricular function may have deteriorated such that repair of the valve is no longer possible and transplantation may need to be considered.
Successful repair of the ebsteinoid valve is difficult, as evidenced by the many techniques described. The aim is to achieve a competent native valve with its insertion at the true annulus and a reduction in right atrial size. Where possible, valve replacement should be avoided, since long term outcomes are better with repair. A maze procedure should also be considered to reduce the long-term risk of atrial flutter and fibrillation.
For high-risk patients in whom the right ventricle is thought to be unable to support the pulmonary circulation with a competent tricuspid valve, techniques to reduce its workload may be considered. The ‘1½’ ventricle repair combines tricuspid valve repair with a cavopulmonary anastomosis so that upper body systemic venous return is directly to the pulmonary arteries, thus offloading the right ventricle. A single ventricle repair may also be used, resulting in a Fontan circulation (see below).
Uhl’s anomaly and arrhythmogenic right ventricular cardiomyopathy are rare sporadic or familial conditions affecting the right ventricle. Table 5 list the key distinguishing features.
|Table 5 Right ventricular cardiomyopathy and Uhl’s anomaly|
|Arrhythmogenic right ventricular cardiomyopathy||
|Morphology||Patchy, localized fibro-fatty replacement of parietal myocardium mostly affecting outflow tract. Other parts of right and occasionally left ventricle may be involved||Congenital absence of parietal ventricular myocardium with direct apposition of endocardium and epicardium. Normal interventricular septum and left ventricle|
|Sex ratio||2:1 male:female||Equal|
Early diagnosis and the screening of family members of affected individuals is challenging and requires experience. MRI and multislice CT are useful tools, but early abnormalities are subtle and may be over interpreted.
Cor triatatrium and congenital mitral valve anomalies
This is a very rare defect in which one of the atria (nearly always the left) is partitioned by a fibromuscular membrane into an upper chamber that receives the pulmonary veins, and a lower chamber connecting with the atrial appendage and mitral valve. This is thought to occur due to a failure of the common pulmonary venous chamber to incorporate into the body of the left atrium early in fetal life. As a result, a persistent membrane inserts into the atrial septum at the fossa ovalis and into the posterolateral wall just above the mouth of the left atrial appendage. An ASD coexists in about 50% of cases, allowing communication between the right and left atria. The membrane may be intact, or pierced by one or more holes that are usually restrictive, causing supramitral stenosis.
If the membrane obstructs pulmonary venous inflow, presentation is early in life, and adult survivors will have undergone surgical resection. First presentation in adulthood is unusual unless the membrane is nonrestrictive or coexists with a large ASD. Patients may have signs of an ASD or mitral stenosis. New symptoms in adulthood may be due to fibrosis or calcification of the membrane so that it becomes restrictive, or from progressive mitral regurgitation.
The diagnosis is made by echocardiography. The chest radiograph may also be characteristic, showing signs of pulmonary venous congestion, but not the left atrial appendage enlargement that accompanies valvar mitral stenosis, since the appendage lies in the low pressure atrial chamber. The lateral chest radiograph may show enlargement of the pulmonary venous compartment of the left atrium.
Treatment is unnecessary if the membrane is unobstructive and there are no significant associated lesions. The results of surgical resection of obstructive membranes and the postoperative prognosis are good.
Congenital mitral valve anomalies
These are rare and frequently coexist with other lesions. A supramitral ring often coexists with congenital mitral stenosis. It differs from cor triatatrium in that the ring is sited inferiorly to the os of the appendage and lies immediately above the mitral valve.
Shone’s syndrome consists of four levels of left heart obstruction: supramitral ring, parachute mitral valve, subaortic stenosis, and coarctation of the aorta. Parachute mitral valve occurs when the two papillary muscles are fused or there is hypoplasia or absence of one papillary muscle; the valve and its apparatus are often additionally dysplastic. Obstruction occurs at the level of the abnormal papillary muscles. The parachute mitral valve may also be regurgitant if the chordae are elongated and not significantly fused.
Isolated cleft mitral valve differs from the ‘cleft’ seen in an AVSD in being in the anterior (aortic) leaflet, directed towards the aortic outflow tract, rather than being in the space between the bridging leaflets and pointing towards the septum. The isolated cleft can be readily repaired to resemble a competent normal mitral valve.
Left ventricular outflow tract obstruction
Bicuspid aortic valve
This is the commonest congenital cardiac anomaly, occurring in 1 to 2% of the population. Bicuspid aortic valve is four times more common in males than females. In 20% of cases it is associated with other lesions such as patent arterial duct and coarctation. There is also an association with aortic root dilatation and dissection. Symptoms occur late in young people with aortic valve disease, hence regular follow-up is particularly important. Exercise testing is useful in planning the timing of surgery in those with asymptomatic aortic stenosis and left ventricular hypertrophy: ST segment changes and a failure of blood pressure to rise appropriately in response to stress indicate that intervention should be considered. Aortic stenosis and regurgitation are discussed in the article on Heart valve disease.
Supravalvar aortic stenosis
In this least common form of left ventricular outflow tract obstruction there is a localized narrowing of the aorta immediately above the aortic sinuses. Fibromuscular thickening of the aortic wall at the site of obstruction may encroach into the coronary ostia or onto the aortic valve leaflets and adversely influence prognosis. Unlike other forms of left ventricular outflow obstruction, the coronary arteries lie proximal to the obstruction and so are exposed to high left ventricular pressures, resulting in premature atherosclerosis. The condition may be associated with Williams’ syndrome when the prognosis may be worse since there is diffuse arterial involvement that may also involve the pulmonary and renal arteries (see: Cardiac involvement in genetic disease).
Subaortic stenosis may be due to a discrete fibromuscular ridge or ring, or a long muscular tunnel. It may exist in isolation or as part of another lesion such as AVSD, where the aorta is ‘unwedged’; the left ventricular outflow tract elongated, and abnormal insertion of the left AV valve may all cause obstruction. Whether discrete or tunnel-like, subaortic stenosis tends to progress and may recur following surgical resection. It may result in functional disruption of the aortic valve and secondary aortic regurgitation, which can progress even after resection of subaortic stenosis.
Atrial septal defects
Interatrial communications are common both in congenital heart disease and in the general population. ASDs account for around 10% of congenital heart disease.
Patent foramen ovale
Patent foramen ovale (PFO) is a normal variant that occurs in 20 to 30% of the population. There is no deficiency of atrial septal tissue, but after birth—when left atrial (LA) pressure exceeds right atrial (RA) pressure and closes the PFO—the valve of the foramen ovale fails to fuse with the septum.
Interest has risen in PFO in recent years because of its potential to be a route for paradoxical embolism or for thrombosis in situ, especially if associated with an aneurysmal interatrial septum. PFO is associated with cryptogenic embolic stroke in young adults, with neurological decompression sickness in divers, and with migraine with aura. Device closure of a PFO appears to protect against recurrent stroke and decompression sickness. Whether closure of PFO will be beneficial for some sufferers of migraine is the subject of current research.
Careful consideration should be given to all risk factors in assessing a patient with an embolic stroke and a PFO for suitability for device closure of the PFO. If there are multiple risk factors for arterial disease, such as advanced age, smoking history, diabetes, hyperlipidaemia, hypertension, or proven existing atherosclerotic disease, then device closure of a PFO is unlikely to reduce the risk of a further embolic event. The same is true for patients with risk factors for left-sided intracardiac thrombosis, such as atrial fibrillation, mitral valve disease with a dilated left atrium, or left ventricular aneurysm. In contrast, patients with a PFO and previous embolic stroke who have risk factors for venous thrombosis, such as a thrombophilia or previous venous thomboembolism, may well be protected against further events by device closure.
Ostium secundum atrial septal defect
Secundum ASD accounts for 40% of left-to-right shunts in adults aged over 40 years. It is commoner in females, with a sex ratio of 2:1, and may be familial. It may occur as an isolated abnormality with autosomal dominant inheritance, be associated with Holt–Oram syndrome (autosomal dominant skeletal abnormalities and AV conduction defects due to TBX5 mutation), and is a common association with Down’s syndrome.
ASD may be an incidental finding in an elderly patient at autopsy, and diagnosis in life may be delayed well into adulthood because of the absence of symptoms and subtlety of clinical signs. However, the natural history of this lesion is not benign: historically only 50% with unoperated nonrestrictive (large) ASD survived to the age of 40 years, and 10% beyond 60 years of age.
Presentation in adulthood may be with symptoms of exertional dyspnoea or palpitation, or as a result of incidental clinical or radiographic findings. However, 20% may have developed atrial fibrillation by 40 years, with the figure rising to around 60% by the age of 60 years. Similarly, the volume-loaded right ventricle is well tolerated for many years, but may ultimately fail, usually after the fifth decade.
Contributing factors to progression of symptoms with age may be increased left-to-right shunting due to an age-related reduction in left ventricular compliance causing an increase in left ventricular end diastolic pressure and therefore left atrial pressure, and development of mitral regurgitation causing an increase in left atrial pressure. In addition, modest pulmonary arterial hypertension increases with age so the right ventricle is exposed to pressure as well as volume overload, precipitating right ventricular failure.
A left-to-right shunt at atrial level predisposes to paradoxical embolus since simple manoeuvres such as the Valsalva are sufficient to increase right atrial pressure and reverse the shunt. Patients with unoperated ASD are therefore at risk of embolic stroke, and should not dive because of the risk of paradoxical gas embolism.
Interactions with coexisting heart disease
Acquired disease may coexist and interact with congenital heart disease, especially in the ageing patient. Left ventricular dysfunction due to coronary artery disease and systemic hypertension may increase the left-to-right interatrial shunt, resulting in a more rapid clinical deterioration. Similarly, mitral regurgitation increases the effective interatrial shunt and mitral valve abnormalities may be acquired secondary to the effects of a secundum ASD. There may be distortion of the anterior mitral valve leaflet with fibrotic shortened chordae due to the abnormal position of the interventricular septum as a result of chronic right ventricular overload. Lutembacher’s syndrome is the association of mitral stenosis with secundum ASD.
Mitral valve disease is underestimated in the presence of an ASD because the LA is able to decompress through the ASD. If significant mitral stenosis or regurgitation is overlooked at the time of ASD repair, left atrial pressure will rise and the patient may decompensate dramatically. It is therefore vital to ensure thorough assessment of the mitral valve in any patient in whom ASD closure is planned. Since LV dysfunction may also be masked by an ASD, the defect serving to allow the LV to offload, ventricular function must also be assessed carefully prior to ASD closure, particularly in elderly patients.
Coexisting pulmonary stenosis may be overestimated in the presence of an ASD, since Doppler velocities are increased in the presence of a left-to-right shunt.
Pulmonary vascular disease and atrial septal defect
Mild pulmonary hypertension with ASD is a common finding with advancing age, but pulmonary vascular resistance is rarely >6 Wood units and advanced pulmonary hypertension is rare. Few ASDs develop a right-to-left shunt secondary to pulmonary vascular disease, and a causal relationship between ASD and the Eisenmenger reaction remains controversial. In ASD, unlike other lesions which may cause the Eisenmenger reaction such as large VSD, the pulmonary vasculature is not exposed to increased flow at systemic pressure.
ASD with a right-to-left shunt due to pulmonary vascular disease and pulmonary hypertension occurs most commonly in young women, and in some cases may be due to idiopathic pulmonary arterial hypertension with an incidental ASD. In this combination, the prognosis may be better than for idiopathic pulmonary arterial hypertension with intact atrial septum, the septal defect protecting the right heart from pressure overload by allowing right-to-left shunting. Persistence of the fetal pulmonary vascular pattern may be implicated in the development of pulmonary hypertension in some young patients with ASD. Patients living or born at high altitude have a higher incidence of pulmonary vascular disease.
If the defect is nonrestrictive the a and v waves of the jugular venous pulse tend to be equal. In older patients with reduced left ventricular compliance, the left and therefore right atrial pressure is raised, reflected by an elevated jugular venous pressure. A right ventricular heave may be felt at the left sternal border, and the dilated pulmonary artery may be palpable in the left second intercostal space. The first sound is loud because of increased diastolic flow across the tricuspid valve. If the left-to-right shunt is greater than approximately 2:1, the second heart sound is widely split and fixed, and there is loss of normal sinus arrhythmia. There may be a pulmonary flow murmur at the upper left sternal edge. Only if the ASD has a high gradient across it will it generate a murmur itself, usually a soft continuous murmur. This is the case if the defect is small and restrictive and the left atrial pressure high, e.g. if there is associated mitral stenosis. If the patient has pulmonary vascular disease, the signs will be the same as for pulmonary hypertension with right-to-left shunt (see above).
The ECG may show sinus node dysfunction, prolongation of the PR interval, right axis deviation, and QRS prolongation with rSr′ in lead V1—which does not represent incomplete right bundle branch block, but occurs since the last part of the myocardium to depolarize is the right ventricular outflow tract that is enlarged and thickened due to volume overload. Postoperatively the ECG may show sinus node dysfunction due to damage when the superior vena cava (SVC) is cannulated, and the PR interval returning to normal as right atrial size decreases. Macro re-entry circuits at the site of atrial surgery may result in postoperative ectopic atrial tachycardias.
The typical chest radiograph shows dilated proximal pulmonary arteries with a small aortic knuckle, plethoric lung fields, and cardiomegaly secondary to dilatation of the right atrium and ventricle.
Transthoracic echocardiography demonstrates the volume-overloaded right atrium and ventricle. The size of the shunt can be estimated and colour flow Doppler facilitates the detection of the site of the shunt. If transcatheter device closure is considered, a transoesophageal approach is necessary to define the site and size of the ASD precisely and to identify the pulmonary veins.
Cardiac catheterization is indicated only to calculate pulmonary vascular resistance if there is a suspicion of pulmonary hypertension, or to exclude coexisting congenital or acquired cardiac pathology such as coronary artery disease.
Indications for closure of atrial septal defect
Closure of an ASD is indicated if there is right heart volume overload, left-to-right shunt is 1.5:1 or more, and the ASD is at least 10 mm in diameter. Prevention of recurrent paradoxical embolism is an additional indication for closure. Contraindications to closure are significant pulmonary hypertension (which may be suggested by a right-to-left shunt on exercise or at rest) and severe left ventricular dysfunction. In addition, merely closing the ASD in the presence of significant mitral valve disease is contraindicated.
Irrespective of age, the benefits of device closure should be improved functional class, exercise capacity, and breathlessness. Repair of a large isolated secundum ASD by the third decade results in a normal life expectancy. Between the ages of 25 and 41 years it results in a good but shorter than normal life expectancy, but beyond the age of 41 years morbidity and mortality remain significantly higher than normal. Nonetheless, functional status and longevity are improved following repair over the age of 40 years, 5- and 10-year survival being estimated as 98% and 95% respectively for patients who underwent repair, and 93% and 84% for those treated medically. Repair in older patients does not reduce the risk of late atrial arrhythmia, particularly if there is right ventricular dysfunction, elevated pulmonary artery pressure or pre-existing atrial arrhythmia. Whether the incorporation of a modified maze procedure or cryoablation into the surgical repair of ASD will reduce the long-term incidence of existing or de novo atrial arrhythmia remains to be determined.
Secundum ASDs up to 4 cm stretched diameter may be closed by transcatheter devices so long as the surrounding rim of atrial septal tissue is sufficient. Criteria for device closure of secundum ASD are size less than 4 cm; a situation away from the AV valves, pulmonary, and caval veins; and normal pulmonary venous drainage. The risk of major complication during device closure is 1 to 2%. Following closure, antiplatelet or anticoagulant therapy is recommended for 3 to 6 months. Surgical repair carries also carries a low mortality and morbidity, but perioperative atrial fibrillation is common and recovery time is longer.
Other forms of atrial septal defect
Sinus venosus atrial septal defect
Sinus venosus defects account for 2 to 3% of ASDs and have an equal sex incidence. They are not truly defects of the atrial septum, but since they allow shunting at atrial level, they are included in the classification of ASDs. The inferior border of the more common SVC type of sinus venosus defect is made by the superior limbus of the fossa ovalis, and the upper border comprises the junction of the SVC with the atrial mass. The superior caval vein overrides the atrial septum, connecting to both atria, and the right upper pulmonary vein drains anomalously into the SVC. There may be an ectopic atrial pacemaker because the defect is located in the area of the sinoatrial node. This may be reflected by a leftwards p wave axis and an inverted p wave in lead III.
The sinus venosus defect may not be visualized with transthoracic echocardiography, and a transoesophageal approach is usually necessary to define the defect and is associated anomalous pulmonary venous drainage.
They are unsuitable for transcatheter device closure, both because there is no superior rim and because of anomalous drainage of one or more of the right pulmonary veins. The proximity of the sinus node to the SVC type of defect makes it vulnerable to damage during surgical repair; postoperative atrial pacing may be required.
Coronary sinus defect
The rarest form of ASD, this defect is at the site of entry of the coronary sinus to the right atrium. The unroofed coronary sinus is a variation of coronary sinus defect in which the partition between the coronary sinus and the left atrium is absent as the coronary sinus runs posteriorly along the floor of the left atrium. In this condition, a left SVC commonly connects directly to the left atrium, producing a right-to-left shunt and cyanosis.
Ostium primum atrial septal defect
This is a defect in the true atrial septum that exists as part of an AV septal defect and is discussed below.
Ventricular septal defects
With the exceptions of bicuspid aortic valve and mitral valve prolapse, ventricular septal defect (VSD) is the commonest congenital cardiac malformation, occurring in around 3 per 1000 live births. It occurs equally in both sexes. Defects may exist in isolation, in association with other lesions such as coarctation of the aorta, or as an integral part of lesions such as tetralogy of Fallot. This section deals with isolated VSDs.
Morphology and classification
An understanding of the basic anatomy of the ventricular septum is necessary to appreciate the various types of VSD. A VSD arises when there is failure of one of the components of the ventricular septum to develop correctly. The septum comprises four parts and is described as viewed from the right ventricle:
- ◆ Inlet septum—separates the mitral and tricuspid valves
- ◆ Muscular trabeculated septum—extends from the tricuspid valve leaflet attachments to the muscle separating the tricuspid and pulmonary valves (the crista supraventricularis)
- ◆ Outlet septum—extends from the crista to the pulmonary valve
- ◆ Perimembranous septum—small fibrous area bordered by the aortic and tricuspid valves
VSDs are classified by their location within the septum and by their borders, again viewed from the right ventricle. There are three types: muscular, perimembranous and doubly committed subarterial. The position of muscular and perimembranous VSDs may be inlet, trabecular or outlet, depending on which part of the right ventricle they open into. Perimembranous VSD is the commonest type of defect; only 5 to 7% of VSDs in Europe and North America are doubly committed subarterial defects, whereas they account for up to 30% of defects in Asian patients.
Clinical presentation and complications of unoperated VSD
The presentation of an isolated VSD depends on its size and haemodynamic effects (Table 6). Perimembranous and doubly committed subarterial VSDs may be associated with the development of aortic valve leaflet prolapse and aortic regurgitation, and the conduction tissue in these types of defects is vulnerable to damage at operation.
|Table 6 Grading of ventricular septal defects by size|
|Pulmonary artery pressure: systemic pressure ratio||<0.3||0.3–0.6||RV=LV pressure||RV≥LV pressure|
|Qp:Qs||<1.4: 1||1.4–2.2: 1||>2.2:1||<1.5: 1|
|Clinical grading||Negligible haemodynamic changes, normal LV||LA and LV enlargement and reversible pulmonary hypertension||Pulmonary vascular disease (Eisenmenger syndrome) will develop unless there is RVOTO|
|Restrictive (RV pressure < LV pressure in absence of RVOTO)||Non-restrictive (equal RV and LV pressures in absence of RVOTO)|
Qp, pulmonary blood flow; Qs, systemic blood flow; RVOTO, right ventricular outflow tract obstruction.
Adults with isolated unoperated restrictive VSDs are usually asymptomatic and acyanotic, with normal arterial and jugular venous pulses. There may be a thrill at the left sternal border, the left ventricular apex may be thrusting if the defect is large enough to cause volume overload, and a dilated pulmonary artery may be palpable. The second heart sound is usually normally split. There is a loud harsh pansystolic murmur at the left sternal edge, which is softer and shorter (early systolic) in very small defects.
Late complications of unoperated small VSDs include significant risk of endocarditis due to the high-velocity jet from left to right ventricle, particularly if the jet is directed onto tricuspid valve tissue; aortic regurgitation if the aortic valve forms part of the border of the VSD; atrial arrhythmia if there is left heart volume overload; and small increased risk of sudden death and ventricular arrhythmia.
Larger VSDs rarely present for repair in adulthood since the large left-to-right shunt is unlikely to allow unoperated survival unless pulmonary vascular disease has developed. Nonrestrictive defects are not associated with the classical VSD murmur since left and right ventricular pressures are equal.
Investigation should determine the type and number of VSDs, the size of the defect (restrictive or nonrestrictive), an estimation of the size of the shunt (Qp:Qs), pulmonary artery pressure and resistance, and assessment of left and right ventricular function and volume and pressure overload. Associated lesions that may alter management should be identified, especially aortic regurgitation, subaortic stenosis, and right ventricular outflow tract obstruction.
The chest radiograph is normal if the defect has been small from birth. If the VSD is (or has been) larger, the left ventricle, left atrium, and pulmonary trunk may be dilated and there may be increased pulmonary vascularity. The ECG shows a normal QRS axis unless there are multiple defects, when there may be left axis deviation. In the presence of a large left-to-right shunt the p wave may be broad and there may be evidence of left ventricular hypertrophy. Two-dimensional echocardiography identifies the number and site of defects as well as describing the morphology and associated defects. Doppler is used to estimate the size and direction of the shunt, and right ventricle to left ventricle pressure difference, but this may not be accurate if there is an obliquely lying muscular VSD. Cardiac catheterization is important to measure the size of shunt and pulmonary vascular resistance, with reversibility studies if baseline resistance is high.
Indications for repair and postoperative sequelae
Repair of a VSD is indicated in the presence of symptoms, if Qp:Qs is greater than 2:1, or if there is ventricular dysfunction with right ventricular pressure overload or left ventricular volume overload. Repair should also be undertaken if there are coexisting lesions such as significant right ventricular outflow tract obstruction, or more than mild aortic regurgitation or aortic valve prolapse in the presence of an outlet VSD. An episode of endocarditis may also be considered as an indication for VSD closure. If the pulmonary artery pressure is more than two-thirds systemic pressure, repair should only be considered if Qp:Qs exceeds 1.5:1 or if there is evidence of reversibility in response to pulmonary vasodilators such as oxygen and nitric oxide.
The surgical approach aims at avoiding damage to important structures such as the conducting tissues, which are especially vulnerable in perimembranous defects. Transatrial repair reduces the risk of postoperative ventricular arrhythmias by avoiding a right ventriculotomy. Transient postoperative complete heart block is associated with an increased risk of late high degree block, and permanent pacemaker implantation is indicated in the 1 to 2% of patients in whom complete heart block persists, even if they are asymptomatic, because there is a significant risk of late sudden death.
The prognosis after VSD repair in the early years of life is good, but if repair is delayed into late childhood left ventricular dilatation may persist and systolic function be impaired. Long-term postoperative survival depends on the presence of pulmonary hypertension, left ventricular dysfunction, and complications such as aortic regurgitation and endocarditis.
Transcatheter device closure of VSDs is possible providing that valvar apparatus can be avoided. Both muscular and selected perimembranous VSDs may be device closed, the latter requiring experienced hands to avoid damage to the aortic valve and heart block. This approach is particularly useful for defects that are difficult to access or close surgically, and a hybrid surgical/interventional technique may be used.
Atrioventricular septal defect (AVSD)
The key feature of an atrioventricular septal defect (AVSD) (previously termed endocardial cushion defect or AV canal) is a common atrioventricular (AV) junction and AV valve ring. The AV septum is absent and the AV valves share a common junction and fibrous ring, with a five-leaflet AV valve. Since they share common leaflets, the valves are not correctly called mitral and tricuspid valves, but left and right AV valves. As a consequence the normal offsetting of the right AV valve towards the right ventricular apex is absent. In addition, the aorta is ‘unwedged’ from its normal position between the left and right AV valves. The left ventricular outflow tract is therefore elongated (‘gooseneck’) and has the propensity to develop obstruction. ‘Cleft mitral valve’ refers to the commissure between the anterior and posterior bridging leaflets that renders the left AV valve potentially regurgitant. The left ventricular papillary muscles are abnormally placed anteriorly and posteriorly instead of in the normal anterolateral and posteromedial positions. Ostium primum defect describes the atrial component of an AVSD.
There are two types of AVSD, partial and complete. Both have a common AV junction, but in a partial AVSD the right and left AV valves have separate orifices and the VSD is usually small or absent, and in a complete AVSD there is a common AV valve and valve orifice, and the VSD is usually large.
AVSD occurs with equal sex incidence. The complete form of the defect is most commonly associated with Down’s syndrome. A single gene defect may be responsible for AVSD with normal chromosomes, when the recurrence risk is about 10% if the mother has an AVSD, less if the father is affected.
The physiological consequences of an AVSD are the same as for other conditions with left-to-right shunting at atrial or ventricular level, but may be complicated by left AV valve regurgitation or left ventricular outflow tract obstruction. Pulmonary vascular disease may develop if the VSD is large and nonrestrictive. Patients with Down’s syndrome are at particular risk of this complication, and coexisting upper airway obstruction and sleep apnoea, and abnormal pulmonary parenchyma may be contributory factors.
Investigations for AVSD
The ECG is distinctive, with a left and superior QRS axis and notching of S waves in the inferior leads. The chest radiograph appearances depend on the degree of interatrial shunting and left AV valve regurgitation, the former producing cardiomegaly due to left heart dilatation and the latter left atrial enlargement. There may be increased pulmonary vascularity, particularly in young patients with complete AVSD and high pulmonary blood flow.
Transthoracic echocardiography reveals the detailed anatomy of the defect and establishes the site and degree of shunting, the presence and nature of left ventricular outflow tract obstruction, and the function and anatomy of the AV valves.
The indications for cardiac catheterization are the same as for secundum ASD, namely to exclude inoperable pulmonary vascular disease. In addition useful information may be obtained regarding the severity of left AV valve regurgitation and left ventricular outflow tract obstruction.
Clinical course of AVSD
First presentation may occur in adulthood if the left-to-right shunt is small and the left AV valve is competent. Physical signs are the same as in other ASDs, and there may also be an apical pansystolic murmur. Paradoxical embolism is less common than in secundum ASD because the position of the primum defect low in the interatrial septum avoids the streaming of blood from the inferior vena cava that is most likely to carry emboli and is directed towards the midportion of the septum.
Most adult patients have undergone surgery to repair the defect and left AV valve: others have survived unoperated and may have developed pulmonary vascular disease.
Late complications after repair of AVSD include recurrent AV valve regurgitation, the severity of which may increase with age in response to changes in the left ventricle due to ageing, ischaemia, or systemic hypertension; residual ASD or VSD; residual or recurrent left ventricular outflow tract obstruction, which may be difficult to relieve surgically if it involves left AV valve tissue; complete heart block, related to the abnormally positioned AV node that is particularly vulnerable to intraoperative damage; atrial arrhythmia—it is vital to read the original operation note when planning ablation, since the mouth of the coronary sinus is often left opening into the left atrium making it inaccessible to the electrophysiologist; and endocarditis—relating largely to the left AV valve.
Coarctation of the aorta
Aortic coarctation is a narrowing of the aorta, usually sited near the ligamentum arteriosum. It is one of the commonest congenital cardiac lesions, occurring in 1 in 12 000 live births, with a male to female ratio of 3:1. There is considerable variation in anatomy and severity, ranging from a mild obstruction to interruption of the aorta, and from a discrete fibromuscular shelf to hypoplasia of the arch. Coarctation is most strongly associated with bicuspid aortic valve, which coexists in up to 80% of cases. Other associations are VSD, patent ductus arteriosus, subaortic ridge, and mitral valve abnormalities. It is a frequent finding in Turner’s syndrome and is also associated with congenital aneurysm of the circle of Willis.
Most patients present in infancy, but some survive into adulthood before being diagnosed at routine examination or during investigation for hypertension, leg claudication, angina, heart failure, or cerebral haemorrhage. More than 75% with unoperated coarctation die by age 50 years, from premature coronary disease, stroke, or aortic dissection.
Clinical findings include upper body hypertension: the leg blood pressure is lower, as is that in the left arm if the subclavian artery is involved in the coarctation. If there is a good collateral supply, femoral arteries may be easily palpable, but they are usually reduced, with radiofemoral delay. Intercostal collaterals may be both visible and palpable over the patient’s back. There is an ejection systolic murmur from the site of coarctation, and systolic collateral murmurs may be heard. Fundoscopy shows a typical corkscrew appearance of the retinal vessels and there may be evidence of hypertensive retinopathy.
There may be electrocardiographic evidence of left ventricular hypertrophy. The chest radiograph has a typical appearance.
Transthoracic echocardiography may show left ventricular hypertrophy, with the coarctation site visualized on two-dimensional imaging and its severity assessed using Doppler mode from the suprasternal notch. A peak gradient of over 20 mmHg is significant, especially if accompanied by a diastolic tail.
MRI provides definitive non-invasive haemodynamic data and two- and three-dimensional images of the coarctation site, collaterals and related vessels. It may obviate the need for angiography unless coronary disease is suspected. In the adult, diagnostic angiography is usually reserved for assessing coronary disease.
Repair of native coarctation
Surgical repair is the conventional approach in neonates and children, with a risk of less than 1% for those with simple coarctation. Extensive collateral vessels and nonelastic diseased aortic tissue make surgical repair of adult coarctation challenging, and this is associated with significant morbidity. The incidence of perioperative spinal cord ischaemia and paraplegia is up to 0.4%, those patients without an abundant collateral circulation probably being most at risk. Those with well-developed collaterals are at risk of significant intraoperative haemorrhage. Early postoperative hypertension is common and may be difficult to control, and postoperative intestinal ileus may persist for several days.
Transcatheter balloon dilatation and primary stenting of native coarctation in adults are alternatives to surgery. The use of primary stents, particularly covered stents, is likely to support the aorta following dilatation and to reduce the risk of aortic dissection or late aneurysm formation. However, this interventional approach is controversial and should only be performed in specialist centres; careful follow-up is required.
Follow-up after coarctation repair
Follow-up after repair of coarctation should be lifelong, since late complications are frequent: residual or recoarctation, aneurysm formation, persistent hypertension despite adequate repair, premature atherosclerotic disease, and progression of associated lesions such as bicuspid aortic valve. Older age at repair is the main risk factor influencing longevity. Late survival is 92% for patients repaired in infancy, 25-year survival is 75% for those repaired between ages and 40 years, but 15-year survival is only 50% for those repaired at age more than 40 years.
Recoarctation may be diagnosed when the resting arm–leg systolic blood pressure gradient is 20 mmHg at rest and 50 mmHg after exercise. This occurs most commonly following neonatal repair by end-to-end anastomosis, and the diagnosis should be sought when there is new or persisting hypertension. Blood pressure should be recorded in the both arms of all such patients; spuriously low readings may be obtained if one of the subclavian arteries (usually the left) is involved in the repair or recoarctation.
MRI is the investigation of choice for both recoarctation and aneurysm formation after coarctation repair. Multislice CT is used following stent repair of coarctation, since the artefact produced by the stent renders MRI unhelpful. Balloon angioplasty with or without stent insertion is used to relieve most recoarctations, but reoperation is required for some patients with complex anatomy.
The 14-year incidence of aneurysm formation at the site of repair is up to 27%; it occurs most commonly in adults and in those with Dacron patch repair. An aneurysm may rupture into the bronchial tree, hence any patient with a history of coarctation who presents with haemoptysis should undergo emergency noninvasive diagnostic imaging (MRI or CT) and surgical repair. Bronchoscopy and conventional angiography are contraindicated since they may cause further damage to the ruptured area.
Hypertension is a major risk factor for atherosclerotic disease and may persist despite an apparently good result from surgical repair. Continuing hypertension relates in part to older age at time of surgery. Nonetheless, even if repaired in adulthood, systolic hypertension becomes easier to control.
Patent arterial duct
The pathophysiological consequences of a patent arterial duct in adulthood depend on the size of the shunt. Small ducts are of no haemodynamic significance and are associated with a low risk of infective endarteritis. Moderate-sized ducts may cause left heart volume overload and late atrial fibrillation and ventricular dysfunction. A large nonrestrictive duct may cause pulmonary vascular disease (see ‘Eisenmenger syndrome’, above).
Duct closure is usually recommended if a duct is clinically detectable, i.e. there is a machinery murmur in the left subclavicular area, to avoid long-term haemodynamic complications. Ducts up to 14 mm in diameter are usually suitable for transcatheter device closure. Pulmonary vascular disease should be excluded before repair of large ducts is undertaken.
In this rare condition there is a direct communication between adjacent portions of the proximal ascending aorta and pulmonary artery. The communication is usually large and the physiological consequences are the same as for a patent arterial duct. Rare patients surviving unoperated into adulthood are likely to have developed the Eisenmenger reaction. If pulmonary vascular resistance is low at the time of childhood repair, long-term postoperative survival is good.
Truncus arteriosus/common arterial trunk
This condition accounts for 1 to 4% of all congenital heart disease. It may coexist with interrupted aortic arch, coarctation, coronary anomalies and DiGeorge syndrome. A single great artery arises from the heart and gives rise to the coronary arteries, aorta and pulmonary arteries. There is a single semilunar ‘truncal’ valve that has three or more leaflets, and a subtruncal VSD.
Most patients present in infancy with heart failure. If left unoperated, pulmonary vascular resistance rises, cyanosis becomes more marked, and the Eisenmenger reaction becomes established. Repair before pulmonary vascular disease develops involves closure of the VSD, detachment of the pulmonary arteries from the common arterial trunk, and placement of a valved right ventricular to pulmonary artery conduit. The truncal valve then functions as the aortic valve. Late complications following repair include truncal regurgitation, truncal (aortic root) dilation, ventricular dysfunction, and the need to replace stenotic conduits.
Sinus of Valsalva aneurysm
There is dilation of one of the aortic valve sinuses between the aortic valve annulus and sinotubular junction, and the aneurysm progressively dilates and ruptures. The right and noncoronary cusps are most often affected; rupture of the noncoronary sinus aneurysm is nearly always into the right atrium and of the right coronary sinus into the right ventricle or atrium. Involvement of the left coronary sinus is rare. Rupture usually occurs in early adulthood and may be precipitated by endocarditis. If sudden it is accompanied by tearing chest pain, breathlessness, and congestive cardiac failure with a loud continuous murmur. Small perforations may remain asymptomatic for many years. The diagnosis and site of the rupture is confirmed echocardiographically and/or angiographically before surgical or transcatheter repair.
Coronary artery anomalies
The importance of congenital coronary anomalies lies in their potential to impair myocardial blood flow and cause ischaemia and sudden death. Evidence of ischaemia is the main indication for repair.
Anomalous origin of the coronary arteries from an inappropriate aortic sinus
Ischaemia is particularly associated with an anomalous proximal coronary course between the aorta and pulmonary trunk, an intramural proximal segment of the coronary artery inside the aortic wall, and acute angulation between the origin of an anomalous coronary artery and the aortic wall.
Anomalous origin of the left coronary artery from the pulmonary artery
This rare condition usually presents in infancy with myocardial ischaemia and left ventricular failure when pulmonary vascular resistance decreases. However, 10 to 15% survive into adulthood because an adequate intercoronary collateral circulation is established. Adults may be asymptomatic or present with myocardial ischaemia or mitral regurgitation due to papillary muscle dysfunction. Survival following surgical repair depends on the amount of ischaemic myocardial damage and degree of mitral regurgitation.
Congenital coronary arteriovenous fistulae
The coronary arteries arise normally from their aortic sinuses, but a fistulous branch communicates directly with the right ventricle in 40% of cases, the right atrium in 25%, pulmonary artery in 15%, or rarely the SVC or pulmonary vein. Survival to adulthood is usual, but lifespan may be reduced, depending on the size of the fistulous connection and the presence of myocardial ischaemia resulting from any coronary steal phenomenon. Symptoms increase with age and there is a risk of endocarditis, heart failure, arrhythmia, myocardial ischaemia and infarction, and sudden death. Surgical repair is recommended unless there is a trivial isolated shunt. Some smaller fistulae are suitable for transcatheter device occlusion
Bullet list 4: Major types of coronary anomaly
- ◆ Anomalous origin from inappropriate aortic sinus or coronary vessel
- • LAD from right aortic sinus or RCA
- • Absent LMS (separate origins of LAD and Cx)
- • Cx from right aortic sinus or RCA or absent cx
- • RCA from left aortic sinus, posterior sinus or LAD
- • Single coronary artery from right or left aortic sinus
- ◆ Anomalous origin from other systemic artery (rare)
- • Innominate, subclavian, internal mammary, carotid, bronchial arteries, or descending aorta
- ◆ Anomalous origin from pulmonary artery
- ◆ Coronary arteriovenous fistulae
Cx, circumflex; LAD, left anterior descending; LMS, left main stem; RCA, right coronary artery.
Systemic venous anomalies
These anomalies frequently form part a more complex lesion, particularly atrial isomerism.
Superior caval vein anomalies
A persistent left-sided SVC occurs in 0.3% of the general population, approximately 3% of patients with congenital heart disease, and 15% with tetralogy of Fallot. The left SVC may be visible on the chest radiograph. It usually drains to the right atrium via the coronary sinus, which is seen to be dilated on two-dimensional echocardiography. A right-sided SVC is usually also present, but the two caval veins do not usually communicate via the brachiocephalic vein. This common anomaly should be sought routinely at cardiac catheterization; although it does not have any haemodynamic significance, it may cause technical difficulties during transvenous pacemaker insertion and cardiac surgery.
Other SVC anomalies are rare. An absent right SVC is associated with arrhythmias including AV block, sinus node dysfunction, and atrial fibrillation. The left, or rarely the right, SVC may connect directly to the left atrium, causing an obligatory right-to-left shunt and cyanosis. This may be associated with isomerism of the atrial appendages.
Inferior caval vein anomalies
Azygos continuation of the inferior vena cava (IVC) occurs in 0.6% of patients with congenital heart disease. The infrahepatic portion of the IVC is absent and continues to the SVC via an azygos vein; the hepatic veins drain directly into the right atrium. This is often associated with complex lesions, particularly left atrial isomerism. The chest radiograph reveals an absence of the IVC at the junction of the diaphragm with the right heart border and a dilated azygos vein. Direct connection of the IVC to the LA is rare: the patient is cyanosed, as in the SVC–LA connection.
Pulmonary venous anomalies
Total anomalous pulmonary venous drainage
Total anomalous pulmonary venous drainage occurs in 1 in 17 000 live births. All four pulmonary veins drain into the right atrium, either directly or via a common vein into a systemic vein. The anomalous veins may follow (1) a supracardiac course draining to the SVC, azygos, or brachiocephalic veins; (2) a cardiac course, draining to the right atrium directly or to the coronary sinus directly or via a persistent left SVC connection; or (3) an infradiaphragmatic course, draining to the portal vein or IVC.
The presence of pulmonary venous obstruction is the most important predictor of a poor outcome. Associated anomalies include an obligatory right-to-left shunt, nearly always at atrial level.
The condition presents in infancy, hence 98% of patients reaching the adolescent or adult clinic will have survived corrective surgery in early life. Unless there is residual pulmonary hypertension most such adults should be asymptomatic, have a normal cardiovascular examination, and an excellent prognosis. Patients who are still growing may develop obstruction of the redirected pulmonary venous pathway and present with dyspnoea, signs of pulmonary oedema, evidence of pulmonary venous congestion on the chest radiograph, and an obstructive echo Doppler flow signal at the site of the stenosis.
The rare patient who reaches adulthood unoperated is likely to have survived because of a large ASD and unobstructed pulmonary venous drainage. They will be cyanosed, have developed pulmonary vascular disease, and be at risk of atrial tachyarrhythmias and right heart failure. The chest radiograph has the appearance of a large ASD with a small aortic knuckle, cardiomegaly, and a dilated main pulmonary artery. In addition, the anomalous veins may cause an abnormal vascular shadow.
Partial anomalous pulmonary venous drainage
There is anomalous drainage of some of the pulmonary veins to the right atrium. In 90% of cases the anomalous pulmonary venous connection is between the right upper or middle pulmonary vein to the SVC or right atrium, usually in association with an ASD, 10 to 15% of all ASDs and 80 to 90% of SVC-type sinus venosus ASDs being associated with partial anomalous pulmonary venous connection.
Partial anomalous pulmonary venous drainage may present in adult life with signs of a left-to-right shunt at atrial level; the pathophysiological consequences are the same as for an ASD with an equivalent shunt.
The chest radiograph may reveal the abnormally draining pulmonary vein. Transthoracic echocardiography may be indicative of a shunt at atrial level, but in adults it may not be possible to image the pulmonary veins and a transoesophageal approach is likely to be necessary. The identification of all the pulmonary veins is crucial in assessing the suitability of a secundum ASD for transcatheter device closure, this technique being contraindicated in the presence of anomalous pulmonary veins (see ‘Atrial septal defects’, above).
The indications for surgical repair are the same as those for repair of an ASD. In the most common variant of right pulmonary venous connection to the SVC in association with a sinus venosus defect, the patch closing the ASD is placed to direct the anomalous vein into the left atrium.
Partial anomalous pulmonary venous drainage also occurs as part of the rare familial ‘scimitar syndrome’ in which part or all of the right pulmonary venous drainage is to the IVC below the diaphragm. The affected lung lobes are usually hypoplastic and are supplied with arterial blood from the descending aorta. Recurrent infection and bronchiectasis may develop in the hypoplastic lobes or lung. MRI demonstrates the abnormal arterial supply and venous drainage of the affected lung segment, and may obviate the need for diagnostic cardiac catheterization. Surgical repair may be complicated by difficulty in maintaining perfusion to the affected lung, and lobectomy may be required. In view of this it should be remembered that patients presenting with scimitar syndrome for the first time in adult life have a good unoperated prognosis, similar to that of a small ASD.
The nomenclature of the transposition complexes may cause confusion. There are two types:
- ◆ Complete transposition of the great arteries (TGA)—this condition is described as AV concordance, VA discordance, previously known as D-TGA. Without intervention this is not compatible with life once the arterial duct and foramen ovale have closed, because there is complete separation of the systemic and pulmonary circulations such that deoxygenated blood from the systemic veins recirculates to the aorta, and oxygenated blood from the pulmonary veins recirculates to the pulmonary artery.
- ◆ Congenitally corrected TGA (cTGA)—this condition is described as AV and VA discordance, previously known as L-TGA. cTGA is congenitally physiologically ‘corrected’: deoxygenated systemic venous blood reaches the pulmonary artery, albeit via the morphological left ventricle; oxygenated pulmonary venous blood reaches the aorta, but via the morphological right ventricle.
Complete transposition of the great arteries (TGA) (AV concordance, VA discordance)
This accounts for about 5% of congenital cardiac malformations and is four times more common in males than females. Associated anomalies such as VSD and pulmonary stenosis occur in approximately one-third of patients. As described above, unoperated survival after closure of the foramen ovale and arterial duct have closed is dependent upon the presence of other associated lesions, such as a VSD, which allow mixing of the two circulations. Without intervention, 30% die within the first week and only 10% survive their first year.
Immediate management in the neonatal period requires a prostaglandin infusion to maintain patency of the arterial duct until a balloon atrial septostomy is performed. The neonate remains cyanosed, but there is usually adequate mixing to allow it to thrive until definitive surgery. There are survivors of four operative approaches in adult clinics.
Interatrial repair: Mustard or Senning operations
This approach was first described in 1957 and can be used for those with TGA or TGA with VSD. Interatrial repair involves excision of the atrial septum and placement of a saddle-shaped patch (‘baffle’) to direct pulmonary venous blood into the right atrium and right ventricle and thence to the aorta. Systemic venous blood is directed into the left atrium, left ventricle, and pulmonary artery. The right ventricle and tricuspid valve therefore support the systemic circulation.
Clinical signs and complications after interatrial repair
The systemic right ventricle causes a parasternal heave. The aortic component of the second heart sound may be palpable and loud, and the second sound single, due to the anterior-lying aorta. The presence of cyanosis suggests a baffle leak allowing right-to-left shunting between the systemic and pulmonary venous atria. Systemic venous pathway obstruction may be associated with elevation of the jugular venous pressure and hepatomegaly.
Complications after interatrial repair include:
- ◆ Progressive bradycardias and sinus node disease, due to damage to the sinus node during repair
- ◆ Atrial flutter and interatrial re entry tachycardias, due to extensive atrial surgical scarring—these are often poorly tolerated, are associated with sudden death, and should be treated with urgent DC cardioversion rather than antiarrhythmic drugs, since the latter can precipitate cardiovascular collapse if there is underlying impaired ventricular function. After an episode of flutter, ablation should be performed.
- ◆ Systemic venous pathway obstruction, which usually only causes symptoms if both the IVC and SVC pathways are narrowed—if only one pathway is narrowed, the systemic venous blood flows along the azygos vein and drains to the heart via the unobstructed pathway; obstruction can usually be relieved by balloon dilation or stenting
- ◆ Pulmonary venous pathway obstruction such that flow into the atrium and systemic ventricle is obstructed—the patient will be breathless, but clinical signs are few; it is demonstrated by echocardiography or MRI; surgical repair is usually necessary; transcatheter intervention is usually unsatisfactory
- ◆ Baffle leak—holes along the baffle suture lines allow shunting which may be left to right, or right to left, causing cyanosis; an interventional approach sometimes allows successful closure of these interatrial communications
- ◆ Systemic AV valve regurgitation—the tricuspid valve is poorly designed to support systemic pressures and commonly becomes regurgitant; if right ventricular function is adequate, valve replacement should be performed because valve repair is rarely successful
- ◆ Systemic ventricular failure—the right ventricle may fail because it is inherently unsuitable to support the systemic circulation in the long term, because of long-standing tricuspid regurgitation, and because of poor ventricular filling from the surgically constructed atrial pathways
There has been much interest in whether placement of a pulmonary artery band to ‘retrain’ the left ventricle to enable it to support the systemic circulation will allow takedown of the Mustard operation and performance of an arterial switch operation. This approach only appears possible in young children, or in older patients with a degree of left ventricular outflow tract obstruction in whom the left ventricle has always retained near systemic pressures.
Arterial switch operation
As a result of the late complications of interatrial repair, a different surgical approach was developed that restored the left ventricle to the systemic circulation and avoided extensive atrial surgery: the arterial switch.
Since the 1980s anatomical correction by the arterial switch operation has superseded interatrial repair as the operation of choice for most patients with TGA. Blood is redirected at arterial level by switching the aorta and pulmonary arteries so that the left ventricle becomes the subaortic ventricle supporting the systemic circulation. The coronary arteries are reimplanted into the neo-aortic root.
Late follow-up appears good for these patients, but vigilance is required to detect late problems including myocardial ischaemia due to coronary anastomotic stenosis; neo-aortic or pulmonary valve regurgitation; neo-aortic root dilation; and pulmonary arterial stenosis.
This operation is performed for patients with TGA, VSD, and pulmonary stenosis. The VSD is closed so that the left ventricle carrying oxygenated blood empties into the aorta. The stenotic pulmonary artery is ligated and a conduit is placed between the right ventricle and pulmonary artery. The main advantage of this operation is that the left ventricle supports the systemic circulation, but it commits the patient to several further conduit replacement operations.
Congenitally corrected transposition of the great arteries (cTGA) (AV, VA discordance)
This rare condition accounts for less than 1% of all congenital heart disease. Both atrial and arterial connections to the ventricles are discordant, so pulmonary venous blood passes through the left atrium, through the right ventricle and into an anteriorly lying aorta. Similarly, systemic venous blood reaches the pulmonary trunk via the left ventricle. The circulation is therefore physiologically ‘corrected’, but the morphological right ventricle and tricuspid valve support the systemic circulation.
More than 95% of cases have associated anomalies, most commonly VSD and pulmonary stenosis, but also Ebstein anomaly of the systemic (tricuspid) AV valve, aortic stenosis, AVSD, abnormalities of situs, and coarctation. Congenital complete heart block occurs in around 5% of patients and may develop at any stage of life, particularly following surgery to the AV valve.
Presentation depends on associated lesions. Patients with isolated cTGA may remain asymptomatic and undiagnosed into old age, but failure of the systemic ventricle, systemic AV valve regurgitation, or the onset of complete heart block and atrial arrhythmias usually result in presentation with symptoms from the fourth decade onwards. Those with VSD and pulmonary stenosis may be cyanosed, and those with VSD alone may present with pulmonary hypertension.
A parasternal heave is usually palpable from the pressure-loaded anteriorly lying systemic right ventricle; this may be especially prominent if it is also volume-loaded by systemic (tricuspid) AV valve regurgitation. There may be a prominent aortic pulsation in the suprasternal notch and the aortic component of the second heart sound may be palpable and loud. The pulmonary component is soft or inaudible due to the posterior position of the pulmonary artery.
The ECG may show varying degrees of AV block or evidence of pre-excitation due to accessory pathways (associated with Ebstein-like anomalies of the systemic AV valve). There may be left axis deviation. The right and left bundles are inverted, so the initial septal activation is right-to-left, resulting in Q waves in V1–2 and an absent Q in V5–6; this pattern may be wrongly interpreted as a previous anterior myocardial infarction. The chest radiograph has a typical appearance. Echocardiography confirms the discordant relations and assesses ventricular and systemic (tricuspid) AV valve function as well as other associated lesions. Ebstein anomaly may be diagnosed if the tricuspid valve is apically displaced by more than 8 mm/m2. Cardiac catheterization is indicated to assess the haemodynamic importance of associated lesions.
Angiotensin converting enzyme (ACE) inhibitors may be useful when there is systemic ventricular dysfunction or AV valve regurgitation, but there are no trial data to support their use. Transvenous AV sequential pacing is indicated for complete heart block; active fixation ventricular leads are required because of the absence of coarse apical trabeculations in the morphologically left subpulmonary ventricle. If there are associated intracardiac shunts, patients should be formally anticoagulated to reduce the risk of paradoxical embolism, or epicardial pacing should be considered.
The conventional surgical approach to systemic AV valve regurgitation is tricuspid valve replacement (repair is rarely successful), but if systemic ventricular function is poor (ejection fraction <40%) transplantation may be the only option. Where there is coexistent VSD and pulmonary stenosis, classical repair involved closure of the VSD and insertion of a valved conduit between the left ventricle and pulmonary artery, with the right ventricle continuing to support the systemic circulation.
Anatomical repair, so that the morphological left ventricle supports the systemic ventricle, has had success in children with systemic AV valve regurgitation and systemic ventricular dysfunction. For patients with an associated non-restrictive VSD the left ventricle is at systemic pressure and therefore ‘pretrained’ to support the systemic circulation. If there is no pulmonary stenosis, a ‘double switch’ may be performed, combining an interatrial repair (usually a Senning operation) with an arterial switch operation. If there is also pulmonary stenosis, the Senning operation is combined with a Rastelli-type repair. The regurgitant tricuspid valve and right ventricle are therefore placed in the pulmonary circulation. For children with corrected transposition whose left ventricle is at low pressure, a period of left ventricular ‘training’ is required before a double switch operation can be performed, which is achieved by placing a pulmonary artery band to increase left ventricular pressure and induce hypertrophy. Pulmonary artery banding per se may improve symptoms, since the increased left ventricular pressure causes the interventricular septum to move towards the systemic ventricle, reducing systemic AV regurgitation.
The long-term outcome of these anatomical approaches to corrected transposition is not yet known; complications relating to the dysfunction of the retrained left ventricular, conduit replacement, neo-aortic valve regurgitation, and arrhythmia may become significant. There are reports of adults with VSD and pulmonary stenosis having successfully undergone Mustard–Rastelli repair, but it is probably not possible to adequately ‘train’ an adult left ventricle that has been at low pressure for many years.
Tetralogy of Fallot
Tetralogy of Fallot is the commonest cyanotic defect, occurring in 1 in 3600 live births; it affects males and females equally. Most patients reaching the adult clinics have undergone radical repair, but some natural and palliated survivors may present.
The fundamental abnormality in tetralogy of Fallot is anterocephalad deviation of the outlet septum which creates the four key features: subvalvar pulmonary stenosis, VSD, an aortic valve that overrides the VSD, and right ventricular hypertrophy. There is great anatomical variation, ranging from minimal aortic override to double outlet right ventricle (DORV), and from minimal pulmonary stenosis to pulmonary atresia. The VSD is perimembranous and there is usually additional pulmonary valvar stenosis.
Microdeletions of chromosome 22q11 may occur in association with tetralogy of Fallot, especially in its most severe form with pulmonary atresia and associated with a broad spectrum of phenotypic abnormalities in the velocardiofacial syndrome (which includes DiGeorge syndrome) with (1) other cardiac defects—Fallot with right aortic arch, truncus arteriosus, pulmonary atresia with VSD, interrupted aortic arch; (2) facial abnormalities—cleft palate, hare lip, hypertelorism, narrow eye fissures, puffy eyelids, a small mouth, deformed earlobes; (3) psychiatric disorders and learning difficulties; and (4) neonatal immune deficiency (thymic hypoplasia) and hypocalcaemia (parathyroid hypoplasia).
Cardiac defects associated with tetralogy of Fallot include a right-sided aortic arch in 16%, a left SVC in around 15%, additional VSDs in 5%, and a secundum ASD (‘pentalogy’ of Fallot) in 8%. The most important associated coronary anomaly is the crossing of the right ventricular outflow tract by a left anterior descending coronary artery arising anomalously from the right coronary sinus: this is vulnerable to damage during surgical repair.
Clinical course and management
Without surgical intervention, only 2% of patients survive to their fortieth year. Those that do survive may be a selected group in whom subpulmonary stenosis was not severe in early life, but progressed with advancing age. Unoperated patients are at risk of the complications of cyanosis, endocarditis, atrial and ventricular arrhythmias, progressive ascending aortic dilatation (without the high risk of dissection found in Marfan’s syndrome), aortic regurgitation—causing volume overload of both ventricles and subsequent biventricular failure, and systemic hypertension—adding additional pressure overload to the work of both ventricles and further contributing to the onset of biventricular failure.
There is cyanosis and clubbing, a right ventricular heave, and sometimes a thrill over the right ventricular outflow tract. A right-sided aorta may be palpable to the right of the sternum. The second heart sound is usually single, and there is a loud pulmonary ejection murmur. There may be aortic regurgitation.
The ECG shows right axis deviation and right ventricular hypertrophy, and the QRS duration may be prolonged in older patients. The classical cardiac silhouette is a ‘coeur en sabot’, i.e. a clog-shaped heart, but this is more likely to be seen in tetralogy with pulmonary atresia (see below). The heart size is usually normal and pulmonary vascularity reduced. There may be a right-sided aortic arch indenting the right of the trachea, and there may be a prominent dilated ascending aorta.
Two-dimensional echocardiography reveals infundibular stenosis with or without pulmonary valve stenosis, right ventricular hypertrophy, the typical VSD, and varying degrees of aortic override. There may be evidence of left ventricular volume overload, aortic root dilatation and aortic regurgitation.
Cardiac catheterization should be performed prior to radical repair in adults. The anatomy of the right ventricular outflow tract obstruction and pulmonary arteries is defined, and pulmonary vascular resistance assessed. Selective coronary angiography demonstrates any anomalous origin and course as well as acquired coronary disease. Aortography shows aortic root dilatation and any aortopulmonary collaterals. MRI may be performed instead of conventional cardiac catheterization, except that it does not provide pulmonary vascular resistance data.
Helen Taussig first suggested palliative surgery in 1943, and the first Blalock–Taussig shunt was performed in 1945 (Table 7). Nowadays, palliative shunts are usually performed as a staging procedure in small infants; however, occasional patients reach the adult clinic having had palliation without subsequent radical repair. They are cyanosed and clubbed and have a continuous murmur under the clavicle and over the scapula on the side of the shunt. In a classical Blalock–Taussig shunt the ipsilateral radial pulse is diminished or absent and the hand often small. Late complications of systemic to pulmonary artery shunts include infective endarteritis, acquired pulmonary atresia, aortic regurgitation, and biventricular failure, with increasing cyanosis and bronchopulmonary collateral development if the shunt blocks or is outgrown, and pulmonary vascular disease if the shunt is too big.
|Table 7 Systemic to pulmonary arterial shunts|
|Classical Blalock–Taussig shunt||Subclavian artery divided distally. Proximal subclavian artery anastomosed end-to-side to pulmonary artery|
|Modified Blalock–Taussig shunt||Prosthetic graft between subclavian and pulmonary arteries|
|Waterston shunta||Side-to-side anastomosis between ascending aorta and (right) pulmonary artery|
|Potts shunt*||Side-to-side anastomosis between descending aorta and (left) pulmonary artery|
|Other||Prosthetic graft between aorta and pulmonary artery|
a Now obsolete because not possible to adequately control the size of the shunt.
Radical repair involves patch closure of the VSD with infundibular resection with or wirhout pulmonary valvotomy or replacement: 86% of patients who undergo such surgery survive to 32 years of age, these being the majority of tetralogy patients seen in the adult clinic. However, they remain at risk of late complications including pulmonary regurgitation and stenosis, aortic regurgitation, ventricular dysfunction, endocarditis, arrhythmia, and sudden death. Those repaired in early childhood and by a transannular approach have a better long-term prognosis than those repaired later or by a transventricular approach.
In many patients repair involves placing a patch across the annulus of the pulmonary valve in order to create an unobstructed right ventricular outflow. As a result, most of these patients have free pulmonary regurgitation, which although well tolerated for many years may result in progressive right ventricular dilation and dysfunction, impaired exercise tolerance, and increased risk of atrial and ventricular arrhythmias. A widening of the QRS complex beyond 180 ms may be a marker for right ventricular dilation and dysfunction, these being risk factors for developing worsening functional class, sustained ventricular tachycardia and sudden death. Pulmonary valve replacement is indicated if there is impaired exercise tolerance, sustained arrhythmia, progressive right ventricular dilation or any evidence of right ventricular dysfunction.
Pulmonary regurgitation is worsened in the presence of pulmonary arterial stenosis that may occur at the site of a previous shunt. Right ventricular outflow tract obstruction may recur, especially if a valved right ventricular to pulmonary artery conduit was placed, this being due to excessive formation of neointima (peel) in the conduit or to calcification of the valve.
Most patients have right bundle branch block after repair due to surgical damage to the right bundle as it runs in the floor of the VSD. Bifasicular block and transient postoperative complete heart block carry a risk of developing late complete heart block. Atrial arrhythmias occur in 30% of long-term survivors and are a major cause of morbidity. Those with left-sided volume overload and left atrial dilatation secondary to residual VSD or previous shunts are at particular risk of atrial flutter and fibrillation. Rapidly conducted atrial flutter is particularly poorly tolerated and is likely to be responsible for a proportion of sudden deaths. Ventricular arrhythmias occur in up to 45% of patients. However, the incidence of late sudden death is only 1 to 5%, so nonsustained ventricular arrhythmias are not an independent risk factor. Sustained monomorphic ventricular tachycardia is likely to be a significant risk factor for sudden death, as are atrial arrhythmias and heart block.
Adverse right ventricular risk factors include dilatation and dysfunction, outflow tract obstruction, hypertrophy, aneurysm, impaired myocardial blood flow and pulmonary regurgitation. Surgical risk factor for late sudden death include transventricular versus transatrial repair, large ventriculotomy scar, residual VSD, previous complex or multiple operations, impaired left ventricular function, older age at operation, and length of follow-up.
Tetralogy of Fallot with absent pulmonary valve syndrome
This variation accounts for approximately 3% of cases of tetralogy. There is a ring-like, usually stenotic malformation, with failure of development of the pulmonary valve cusps. The central pulmonary arteries are usually hugely dilated or aneurysmal.
Double outlet right ventricle
In double outlet right ventricle (DORV) more than half the circumference of both great vessels arises from the morphological right ventricle. A complete or partial muscular infundibulum usually lies beneath each arterial valve. The anatomy and physiology are enormously varied, as are the surgical approaches to repair. The degree of pulmonary stenosis and the relation of the VSD to the great vessels determine the haemodynamics.
Most (80%) subaortic defects have pulmonary stenosis and Fallot-like physiology. The Taussig–Bing anomaly accounts for less than 10% of DORV and describes a subpulmonary defect without pulmonary stenosis. There is transposition-like physiology with cyanosis and high pulmonary blood flow. As the pulmonary vascular resistance rises, pulmonary blood flow falls and cyanosis increases. Unoperated survival to adulthood is uncommon, but occurs occasionally if the pulmonary vascular resistance establishes adequate but not excessive pulmonary blood flow. If such a survivor also has a patent arterial duct, there will be reversed differential cyanosis. Deoxygenated blood selectively enters the aorta to supply the arch vessels, whereas oxygenated blood enters the pulmonary artery and supplies the descending aorta via the duct; thus the fingers are more cyanosed and clubbed than the toes.
If the VSD is remote from the great vessels, a biventricular repair may not be possible and a single ventricle repair (Fontan) may be necessary.
Pulmonary atresia with ventricular septal defect
This is a complex and heterogeneous cyanotic condition. The intracardiac anatomy is the same as tetralogy of Fallot, but the right ventricular outflow tract is blind-ended (atretic). The pulmonary blood supply is derived entirely from three different types of systemic vessels: (1) a large muscular duct that resembles a collateral; (2) a diffuse plexus of small ‘bronchial’ arteries arising from mediastinal and intercostal arteries; and (3) large tortuous systemic arterial collaterals known as MAPCAs (major aortopulmonary collateral arteries), which arise directly from the descending aorta, from its major branches (usually the subclavian artery), or from bronchial arteries, and may connect with central pulmonary arteries or supply whole segments or lobes of lung independently, leading this variation to have been termed ‘complex pulmonary atresia’.
Prognosis and management depends largely on the pulmonary vasculature, in which there is considerable anatomical variation. Confluent pulmonary arteries with pulmonary vessels having a near normal arborization pattern to all segments of the lungs are associated with the best prognosis. Here radical repair, with recruitment of MAPCAs to the native pulmonary arteries, an RV to PA conduit, and closure of the VSD is likely to be possible, and the pulmonary vascular resistance is likely to be low. The 20-year survival after radical repair is about 75%. The outlook is worse if there are no native pulmonary arteries and multiple tortuous MAPCAs with poor arborization. Radical repair may be extremely challenging or impossible, and pulmonary vascular resistance likely to be high. Such patients may be suitable for no or only palliative surgery and will remain cyanosed. Following surgical palliation, 20-year survival is around 60%; unoperated survival is very poor, only about 8% reaching 10 years of age, and those that do reach adulthood have a mean age of death of 33 years.
Examination findings in the unoperated or palliated patient are similar to those of the unoperated Fallot without pulmonary atresia, except that there are continuous collateral murmurs and often a collapsing pulse.
The chest radiograph shows a right aortic arch in 25% of cases and has a typical appearance. The pulmonary collateral vessels may follow a bizarre pattern. Colour flow Doppler may identify collateral vessels, but conventional angiography is required to precisely delineate their origin, degree of ostial stenosis, and intrapulmonary course. Multislice CT and MRI are useful tools in imaging complex pulmonary vasculature.
Late complications in unoperated or palliated survivors include increasing cyanosis due either to the development of pulmonary vascular disease in lung segments perfused at systemic pressure through nonstenosed collaterals, or to the progressive stenosis of collateral vessels. In the latter, good symptomatic relief may be obtained from stenting. The aortic root may become markedly dilated and aortic regurgitation may develop, resulting in biventricular volume overload and failure. Aortic valve endocarditis is a particular risk.
Late complications after radical repair include those that follow repair of tetralogy of Fallot. In addition, patients face inevitable repeated conduit replacements, and right ventricular failure secondary to high pulmonary vascular resistance.
Hearts with univentricular AV connection
Also known as univentricular or single-ventricle hearts, these hearts are defined by the connection of both atria to one ventricle, or by the absence of one of the AV connections. There is one dominant ventricle, with a second rudimentary and incomplete ventricle. When the rudimentary ventricle is of right morphology, it nearly always lies anteriorly. Less commonly, there is a posteriorly lying morphologically left rudimentary ventricle, and rarely, there is solitary ventricle of indeterminate morphology.
The two most common variants are double inlet left ventricle (DILV) and tricuspid atresia which together account for around 4 to 5% of congenital heart disease. This section will consider these two conditions, a discussion of more complex variants being beyond the scope of this text.
Presentation depends largely on pulmonary blood flow, which in turn is dependent on the degree of pulmonary stenosis. Those with severe obstruction to pulmonary blood flow present as neonates with severe cyanosis. Neonates without pulmonary stenosis have excessively high pulmonary blood flow and present in congestive cardiac failure with breathlessness and only mild cyanosis. The presence of subaortic stenosis or other obstruction to systemic blood flow such as coarctation exacerbates heart failure and results in early presentation.
The outcome is most favourable for patients with left ventricular morphology, moderate pulmonary stenosis, and no subaortic stenosis, and for those with ‘balanced’ pulmonary and systemic blood flow, i.e. moderately severe pulmonary stenosis and no obstruction to systemic blood flow. Unoperated survival into adulthood is uncommon: 50% of patients with DILV die before 14 years, 50% with double inlet right ventricle die by 4 years of age. Nonetheless, rare patients with balanced circulation reach their sixth decade without surgical intervention.
There is cyanosis and clubbing. A giant a wave may be present in the jugular venous pulse in tricuspid atresia. An absent right ventricular impulse and prominent left ventricular impulse are characteristic of DILV and tricuspid atresia. There may be a precordial thrill from pulmonary stenosis, particularly if the pulmonary artery lies anteriorly. If there are discordant ventriculoarterial connections the aortic pulsation of the anteriorly lying aorta may be prominent in the suprasternal notch. The second heart sound is usually single.
If pulmonary vascular disease has developed there will be additional signs of pulmonary hypertension. Signs of congestive heart failure may be present in the ageing patient, particularly with the onset of atrial arrhythmia, such that the venous pressure is raised, with hepatomegaly and peripheral oedema.
The chest radiograph shows cardiomegaly due to chronic ventricular volume overload. If ventriculoarterial connections are discordant, there is a narrow pedicle and the ascending aorta forms a straight edge along the left heart border. Pulmonary vascularity reflects the pulmonary blood flow, the main pulmonary arteries being small where there is significant pulmonary stenosis, with large main pulmonary arteries indicating high pulmonary blood flow, either past or present.
In tricuspid atresia the ECG usually shows right atrial hypertrophy, normal PR interval, small or absent right ventricular forces, and left axis deviation. There are left axis deviation and large left ventricular forces in DILV. If the rudimentary chamber lies to the right the PR interval is usually normal, but if it lies to the left the PR interval may be prolonged or there may be complete heart block.
Two-dimensional echocardiography and colour flow Doppler allow detailed assessment of the anatomy and physiology, including ventricular morphology and pulmonary and sub-aortic stenosis. Cardiac catheterization is required to assess pulmonary artery anatomy and resistance.
Surgical management of univentricular hearts: the Fontan operation
Management requires a staged approach, the ultimate aim of which is to achieve a pink patient in whom the functionally single ventricle supports only the systemic circulation: the Fontan operation.
The first stage is to obtain control of pulmonary blood flow. In those with excessive flow a pulmonary artery band is placed to create supravalvar pulmonary artery stenosis and limit pulmonary flow. In neonates with severe pulmonary stenosis a systemic artery to pulmonary artery shunt is placed to augment pulmonary blood flow.
As the child grows and becomes more cyanosed the central shunt is replaced with a superior vena cava to pulmonary artery anastomosis (Glenn, or cavopulmonary anastomosis). This reduces cyanosis, perfuses the pulmonary arteries at low pressure, and reduces the volume load on the single ventricle. However, as the child grows, the relative contribution of the SVC to the circulation diminishes, resulting in progressive cyanosis.
The Fontan circulation is one of a chronic low cardiac output state, critically dependent upon adequate systemic venous filling pressure to drive forward flow across the pulmonary vascular bed. It is a fragile circulation in which small changes in haemodynamics can result in a serious, sometimes catastrophic, fall in cardiac output. Problems that can cause trouble include dehydration, stenosis at the site of connection of the right atrium or systemic veins to the pulmonary artery, pulmonary embolism from in situ right atrial thrombus, a rise in pulmonary vascular resistance, atrial flutter, mitral regurgitation, a rise in left ventricular end-diastolic pressure, aortic or subaortic stenosis, drug-induced vasodilatation (e.g. anaesthetic induction agents, nitrates), and positive pressure ventilation that reduces systemic venous return.Completion of the Fontan operation is usually performed by age 4 to 6 years. The principle of this approach is to separate the systemic and pulmonary circulations. This is achieved by using the single functional ventricle to support the systemic circulation and leaving the pulmonary circulation without a ventricle, i.e. with phasic rather than pulsatile flow. Since its first description in 1972 the atriopulmonary Fontan operation has evolved, so that now several variations exist. The favoured approach nowadays is the total cavopulmonary connection (TCPC), which avoids some of the late complications of the original approach. Nonetheless, all the variations result in the same basic physiology, the ‘Fontan circulation’.
Clinical features after the Fontan operation
Most patients are acyanotic: new or worsening cyanosis is cause for concern. The jugular venous pulse is usually slightly raised and the second heart sound single. No murmur arises from the Fontan connection. There may be a murmur of mitral regurgitation. It patients with VA discordance, a loud systolic murmur raises suspicion of subaortic stenosis (which may be at the level of the VSD). The liver edge is often palpable, but new or increasing hepatomegaly is a worrisome finding. Ascites often precedes peripheral oedema in young patients with complications post Fontan.
A combination of echocardiography and MRI provide anatomical and physiological data. Cardiac catheterization is needed to assess pulmonary vascular resistance. Cardiopulmonary exercise testing is a useful indicator early signs of decompensation.
Complications after the Fontan operation
Patient selection is important in ensuring a good outcome of Fontan surgery. Survival post Fontan ranges from 81% at 10 years for ‘perfect candidates’ to 60 to 70% for all patients. Preoperative risk factors for a poor outcome are pulmonary vascular resistance greater than 4 Wood units, mean pulmonary artery pressure more than 15 mmHg, ventricular hypertrophy, impaired systolic ventricular function, severe AV valve regurgitation, aortic outflow obstruction, and small or distorted pulmonary arteries. However, even patients with none of these risk factors are at risk of a great range of late complications which include intra-atrial reentry tachycardia (IART)/atrial flutter, sinus node dysfunction, progressive ventricular dysfunction, AV valve regurgitation, development of subaortic stenosis, pathway obstruction, right lower pulmonary vein compression by dilated right atrium, thromboembolism (all adult patients should be anticoagulated), recurrent effusions, ascites, peripheral oedema, cyanosis (due to development of venous collaterals to the left atrium or pulmonary arteriovenous fistulas), protein-losing enteropathy, and hepatic dysfunction.
A detailed discussion of these many complications is beyond the scope of this book, but atrial flutter/IART merits further discussion because it may be an acutely life-threatening complication. Flutter is common post Fontan, and, as discussed above, poorly tolerated. Time may be wasted once medical attention is sought because the ECG appearances are often atypical and may be misinterpreted as sinus tachycardia. If in doubt, intravenous adenosine will reveal flutter waves and confirm the diagnosis, but will not terminate the arrhythmia. Other intravenous antiarrhythmics should be avoided since they may precipitate cardiovascular collapse. The safest approach is DC cardioversion. Intravenous fluids should be given while the patient is nil by mouth to maintain systemic venous filling pressure. Care must be taken to avoid excessive systemic vasodilation at induction of anaesthesia, and allowance must be made for the fall in cardiac output that accompanies ventilation.
Hypoplastic left heart syndrome
Until very recently this condition was not discussed in adult texts, since there were no survivors to adulthood. With the introduction of the three-staged Norwood operation, resulting in a complex Fontan-type circulation, survivors are beginning to reach the adult clinic.
HLHS is a heterogeneous syndrome in which the left side of the heart is unable to support the systemic circulation because of hypoplasia, stenosis, or atresia at different levels of the left side of the circulation. The three-staged surgical approach to the condition involves: (1) Stage I (Norwood operation)—performed in the first few days of life; the right ventricle and main pulmonary artery are used to reconstruct the systemic outflow tract; pulmonary blood flow is provided by a systemic-pulmonary artery shunt or right ventricle to pulmonary artery conduit. (2) Stage II—this operation is performed at around 2 years; the systemic shunt or conduit to the pulmonary artery is taken down, and the superior vena cava anastomosed to the pulmonary artery (cavopulmonary or Glenn shunt). (3) Stage III—Fontan completion is performed at around 5 years, usually with an extracardiac conduit. In early series only about 50% survived the three operations, but survival now approaches 70%. Those who reach the adult clinic will face the complications of any Fontan circulation, and in addition they are at risk of complications from ascending aorta and coarctation repair sites, coronary arteries arising from the hypoplastic remnant of ascending aorta, left pulmonary artery stenosis at site of arch repair, and failure of the right ventricle and tricuspid valve as they support the systemic circulation.
Pregnancy and contraception in congenital heart disease
Cardiac disease is the leading cause of pregnancy-related death in the United Kingdom. All patients with congenital heart disease should be counselled from adolescence on their risk of pregnancy and their contraceptive options. Pregnancy and contraception in heart disease is discussed in detail in here: , but the risk of pregnancy in congenital heart disease ranges from being the same as that of the general population to a 50% risk of maternal death in pulmonary hypertension. Each patient requires specialist individual assessment before embarking on pregnancy. An outline of the risks associated with different conditions is shown in Table 8: it should be remembered that risks are additive, so a repaired septal defect with poor ventricular function moves from a low-risk to high-risk category.
|Table 8 Risk of maternal mortality in different cardiac conditions|
||High risk, pregnancy contraindicated (>10%)|
||Mechanical valve||Pulmonary hypertension|
|Most repaired septal defects||Systemic right ventricle||Impaired systemic ventricular function|
|Successfully repaired coarctation||Cyanosis without pulmonary hypertension||Aortic aneurysm|
|Repaired tetralogy of Fallot||Fontan circulation||Severe left-sided obstruction, e.g. mitral and aortic stenosis|
|Most regurgitant valvar lesions|
Two principles should be remembered when considering contraceptive options: efficacy of the method, and cardiovascular safety of the method. The risk of oestrogen-containing preparations (which include the combined oral contraceptive pill) relates to their thrombogenicity. Patients at risk of intracardiac or pulmonary thrombosis and those with right-to-left shunts should not use these preparations. Progestogen-only preparations are safe in cardiac disease, but the mode of delivery may carry risk. For example—as stated earlier in this chapter—insertion of a progestogen-eluting intrauterine device (Mirena) carries a risk of vasovagal syncope in nulliparous women, a reaction that can provoke cardiovascular collapse in cyanotic or post-Fontan patients. In addition, although the progestogen-only ‘minipill’ is safe, its efficacy is poor. The newer progestogen-only pill Cerazette combines cardiovascular safety with an efficacy equal to that of the combined pill. Other safe and effective methods useful for most women with cardiac disease are the subdermal implant Implanon and the injectable DepoProvera.
Endocarditis is discussed in this article: Endocarditis; the risks for specific congenital lesions are outlined in Table 9. However, it is noteworthy that UK guidelines on the use of antibiotic prophylaxis have been changed recently, such that this is no longer recommended for any procedure on an uninfected site. By contrast, North American guidelines recommend prophylaxis for those with congenital heart disease that are unrepaired, have shunts or conduits, have prosthetic materials placed within 6 months, or have residual defects at the site of prosthetic material. It is likely that good oral hygiene and regular dental checks are more important in preventing endocarditis than whether or not antibiotic prophylaxis is given.
|Table 9 Risks of infective endocarditis or endarteritis in congenital heart disease|
|Low risk: lesions with no or low velocity turbulence and no prosthetic material|
|Anomalous pulmonary venous drainage||Anomalous pulmonary venous drainage|
|Secundum ASD||Secundum ASD|
|Ebstein’s anomaly||Ebstein’s anomaly with repaired native valve|
|Mild pulmonary stenosis||VSD/tetralogy of Fallot without residual lesions|
|Isolated corrected transposition||Patent ductus arteriosus|
|Eisenmenger syndrome without valvar regurgitation||Fontan type procedures|
|Arterial switch for transposition without residual lesions|
|Systemic AV valve regurgitation||Residual regurgitation of repaired native aortic or systemic AV valve|
|Subaortic stenosis||Nonvalved conduits|
|Moderate—severe pulmonary stenosis|
|Tetralogy of Fallot|
|Double outlet right ventricle|
|Univentricular heart with pulmonary stenosis|
|Restrictive patent ductus arteriosus|
|Bicuspid aortic valve||Prosthetic valves|
|Aortic regurgitation secondary to VSD or subaortic stenosis||Aortopulmonary shunts e.g. Gore-Tex, modified Blalock–Taussig|
|Restrictive VSD||Valved conduits|
ASD, atrial septal defect; AV, atrioventricular; VSD, ventricular septal defect.