Essential hypertension is almost invariably symptomless, and usually detected by routine screening or opportunistic measurement of blood pressure. Key questions to answer in the assessment of a person presenting with an elevated blood pressure are: (1) Do they have hypertension, i.e. is the blood pressure persistently elevated? (2) Are there any associated clinical features that might warrant further evaluation to exclude secondary causes of hypertension? (3) Are there factors that might be contributing to an elevated blood pressure, including lifestyle or dietary factors or concomitant medication? (4) Is there any associated target organ damage or comorbidity that influences the overall cardiovascular disease risk and subsequent treatment of the patient?
It is normal to find large variations in blood pressure measured in a single individual, hence it should be measured as accurately as possible using the British Hypertension Society protocol. All adults should have their blood pressure measured routinely at least every 5 years. Ambulatory blood pressure measurement (ABPM) recordings provide much more information than standard office blood pressure measurements with regard to diagnosis and efficacy of treatment of hypertension.
The appropriate thresholds for diagnosis of hypertension depending on the method of blood pressure measurement are (1) office or clinic—systolic blood pressure (SBP) 140 mmHg, diastolic blood pressure (DBP) 90 mmHg; (2) APPM 24 h—SBP 125 to 130 mmHg, DBP 80 mmHg; daytime—SBP 130 to 135 mmHg, DBP 85 mmHg; night-time—SBP 120 mmHg, DBP 70 mmHg; and (3) home measurements—SBP 130–135 mmHg, DBP 85 mmHg. The European Society of Hypertension classification of hypertension is described in the technical article on this page: Hypertension
Isolated office hypertension (‘white coat’ hypertension) should be diagnosed whenever office blood pressure is greater than or equal to 140/90 mmHg on at least three occasions, while 24-h mean and daytime blood pressures are within their normal range.
Clinical examination and investigation
Fundoscopy is the most convenient method of directly visualizing vascular pathology and provides important prognostic information: three grades are recognized: (1) mild—generalized and focal arteriolar narrowing, arteriolar wall opacification, and arteriovenous nipping; (2) moderate—as (1) plus flame-shaped blot haemorrhages and/or cotton wool spots and/or hard exudates and/or microaneurysms; and (3) severe—as (2) plus swelling of the optic disc.
Aside from measurement of blood pressure and fundal examination as detailed above, particular features to look for on examination are evidence of secondary effects of sustained hypertension on the heart, and features that might suggest the presence of a secondary cause of hypertension (coarctation—absent/delayed femoral pulses, cardiac murmur; and renovascular disease—renal bruit).
Patients with essential hypertension need only a limited number of routine investigations, which must include (1) urine strip test for protein and blood; (2) serum creatinine and electrolytes; (3) blood glucose—ideally fasted; (4) lipid profile—ideally fasted; and (5) electrocardiogram (ECG).
The treatment of hypertension is directed towards reducing risk rather than treating symptoms. There is international consensus that, for office blood pressure, an optimal treatment target should be less than 140/90 mmHg, with a lower target of less than 130/80 mmHg proposed for higher-risk patients, i.e. those with established cardiovascular or renal disease or diabetes. Although early studies focused primarily on diastolic blood pressure as the treatment target, systolic blood pressure is invariably more difficult to control and should be the main focus of treatment.
The most effective lifestyle interventions for reducing blood pressure are (1) modifications to diet to induce weight loss, (2) regular aerobic exercise, and (3) restrictions in alcohol and sodium intake. Many patients will require more than one drug to control blood pressure: monotherapy is rarely sufficient. The blood pressure response to an individual class of blood pressure-lowering medication is heterogeneous, hence there is no ‘perfect drug’ for every patient, but some trials have indicated that certain comorbidities or target organ damage provide compelling indications for inclusion of specific classes of drug therapy in the treatment regimen.
There is wide variation in the international guidelines with regard to the preferred initial therapy for essential hypertension: (1) the (American) Joint National Committee (JNC) VII guideline recommends low-dose thiazide-type diuretic therapy as initial therapy for all patients (unless contraindicated); (2) the recent European guideline suggests that all five main classes of blood pressure-lowering drugs (angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers, β-blockers, calcium channel blockers, and diuretics) are all suitable as initial therapy; (3) the British Hypertension Society/NICE guideline suggests that a calcium channel blocker (C) or alternatively a diuretic (D) are most likely to deliver the most effective initial blood pressure lowering in older people (i.e. ≥55 years), whereas an ACE inhibitor or an angiotensin receptor blocker (A) are preferred initial therapy for younger patients (<55 years), with the caveat that C or D would be the preferred therapy for people of black African origin at any age.
All guidelines recognize that combinations of blood pressure lowering drugs are often required to achieve recommended blood pressure goals, especially in those with high cardiovascular disease risk or comorbidities who are targeted to lower pressures. Only the British guideline provides explicit guidance on preferred combinations of treatment at step 2, i.e. A + C or A + D, and step 3, i.e. A + C + D.
Patients with hypertension and deemed to be at high cardiovascular risk (>20% over 10 years) should receive advice to adjust their lifestyles and be considered for treatment with statin therapy and low-dose aspirin to optimize their risk reduction.
Indications for specialist referral include uncertainty about the decision to treat, investigations to exclude secondary hypertension, severe and complicated hypertension, and resistant hypertension.
Essential hypertension is invariably symptomless and usually detected by routine screening or opportunistic measurement of blood pressure. However, once a patient has been labelled as ‘hypertensive’ it is not uncommon for them to associate preceding symptoms to their elevated blood pressure. Some patients will claim that they can recognize when their blood pressure is elevated, usually on the basis of symptoms such as plethoric features, palpitations, dizziness, or a feeling of tension. Screening surveys have demonstrated that these symptoms occur no more commonly in untreated hypertensive patients than they do in the normotensive population. However, there are two important caveats to the symptomless nature of essential hypertension: (1) symptoms may develop as a consequence of target organ damage, (2) headache may be a feature of severe hypertension.
Most headaches in hypertensive patients are tension headaches, not related to blood pressure at all, although they become more common when patients become aware of the diagnosis. The classic hypertensive headache is present on waking in the morning, situated in the occipital region, radiating to the frontal area, throbbing in quality, and wears off during the course of the day. It is more commonly associated with more severe hypertension. Effective treatment of hypertension reduces the incidence of such headaches. Morning headaches in obese hypertensive patients may be related to sleep apnoea.
Epistaxis is not associated with mild hypertension but is more common in moderate to severe hypertension. However, the associated anxiety can elevate blood pressure when patients present with bleeding, hence it is particularly important that patients are not automatically labelled as hypertensive, with care taken to dissociate hypertension as a cause of epistaxis from a pressor response to the epistaxis itself.
Patients rarely volunteer information about impotence, but there is an increased prevalence of erectile dysfunction in untreated hypertensive men. This is related to two factors: remodelling of small arteries and increased risk of atheroma, both of which vascular changes can reduce penile blood flow despite the elevation in blood pressure. Furthermore, erectile dysfunction can develop or worsen as a consequence of treatment, for the most part related to the reduction in blood pressure before any concomitant change in vascular structure.
This is common in people with untreated hypertension as a consequence of a reduction in urine-concentrating capacity. The symptoms usually improve with treatment.
Symptoms associated with target organ damage
If patients develop cardiac, vascular, cerebrovascular, and/or renal complications as a consequence of long-standing untreated or poorly treated hypertension, then symptoms related to these complications may be present. Target organ damage and associated symptoms are discussed in the technical article on this page: hypertension
Aims of assessment
There are several important issues that must be considered in the assessment of people presenting with an elevated blood pressure:
- ◆ Does the patient have hypertension, i.e. is the blood pressure persistently elevated?
- ◆ Are there any associated clinical features that might warrant further evaluation to exclude secondary causes of hypertension? (see below and the article on secondary hypertension
- ◆ Are there factors that might be contributing to an elevated blood pressure, including lifestyle or dietary factors or concomitant medication?
- ◆ Is there any associated target organ damage or comorbidity that influences the overall cardiovascular disease risk and subsequent treatment of the patient?
These factors, along with the age and ethnicity of the patient, will inform the decision to treat, the urgency of the need to treat, the need for further investigation, and the choice of treatment.
Blood pressure measurement
Large variations in blood pressure measured in a single individual are normal, hence it should be measured as accurately as possible using the British Hypertension Society (BHS) protocol (Bullet list 2). Blood pressure should initially be measured in both arms because there can be large inter-arm difference in blood pressure. The finding of a difference of greater than 10 mmHg may indicate the presence of underlying vascular disease, especially subclavian stenosis. When there is a significant inter-arm difference in blood pressure reading, the arm with the higher pressure should be used for all subsequent measurements.
All adults should have their blood pressure measured routinely at least every 5 years. Those with high-normal blood pressure (systolic blood pressure (SBP) 130–139 mmHg or diastolic blood pressure (DBP) 85–89 mmHg) and those who have had high blood pressure readings at any time previously should have their blood pressure re-measured annually. These measurements can be made in the clinic, in the home setting, or using ambulatory blood pressure monitoring (ABPM) (see below).
Seated blood pressure recordings are generally sufficient, with the patient seated and rested for a few minutes beforehand. At least two measurements should be taken, and if the first is >10 mmHg higher than the subsequent measurement, then it should be discarded and further reading taken. Standing blood pressure (after at least 2 min standing) should be measured in elderly or diabetic patients to exclude significant orthostatic hypotension.
The timing of blood pressure measurement should take account of the timing of medication. Treatment decisions should not be based on single blood pressure readings: the average of two readings at each of at least three visits (depending on severity) should be used to guide the decision to treat. The time between visits will vary according to the severity of the hypertension, ranging from days, weeks to months. In patients with severe hypertension, especially when there is unequivocal evidence of target organ damage, the decision to treat may be made at the time of first presentation.
Bullet list 1 British Hypertension Society protocol for blood pressure measurement
- ◆ Use a properly maintained, calibrated, and validated device
- ◆ Measure sitting blood pressure routinely: standing blood pressure should be recorded at the initial estimation in elderly and diabetic patients
- ◆ Remove light clothing, support arm at heart level, ensure hand relaxed and avoid talking during the measurement procedure
- ◆ Use cuff of appropriate size
- ◆ Lower mercury column slowly (2 mm/s)
- ◆ Read blood pressure to the nearest 2 mmHg
- ◆ Measure diastolic as disappearance of sounds (phase V)
- ◆ Take the mean of at least two readings. more recordings are needed if marked differences between initial measurements are found
- ◆ Do not treat on the basis of an isolated reading
Reprinted from Macmillan Publishers Ltd: Journal of Human Hypertension 18, 139–185 (2004).
When measuring blood pressure, the upper arm should be supported at heart level during recordings, and it is important that an appropriate cuff size is used, with the bladder encircling at least 80% of the upper arm. Using too large a cuff results in an underestimation of blood pressure and too small a cuff will lead to overestimation. If the auscultatory method is used to measure blood pressure, then Korotkoff phase I (first appearance of sound) and phase V sounds (disappearance of sound) should be taken for systolic and diastolic pressures, respectively. If phase V goes to zero, then phase IV (muffling of sound) should be recorded.
The beat-to-beat variability associated with atrial fibrillation can make blood pressure measurement difficult and semiautomatic or automated devices can be very inaccurate in such circumstances, in which case multiple readings of auscultatory measurements are recommended.
Blood pressure monitors
The sphygmomanometer has been the mainstay of blood pressure measurement for over 100 years, but its use is likely to decline as a consequence of the decommissioning of mercury-based devices and the emergence of automated and semiautomated devices for routine blood pressure measurement in the office and home and for ABPM.
It is important to note that there are different diagnostic thresholds for the diagnosis of hypertension dependent on the method of measurement, i.e. when using multiple home or ambulatory blood pressure values to measure an average blood pressure, then the average value used to define hypertension is lower than the equivalent office blood pressure threshold of 140/90 mmHg (Table 1 below) and it should be noted—as stated above—that automated devices are inaccurate in patients with atrial fibrillation. Detailed guidance on blood pressure measurement and a wide range of validated monitors is available from http://www.bhsoc.org.
Ambulatory blood pressure measurements (ABPM)
ABPM recordings provide much more information than standard office blood pressure measurements with regard to diagnosis and efficacy of treatment of hypertension. When compared to office blood pressure, there is a much steeper relationship between ABPM averages and target organ damage indices and cardiovascular events, no doubt reflecting that fact that more measurements are obtained and the ‘white coat effect (see below) is eliminated. Generally, ABPM devices are programmed to record blood pressure at 20 min intervals during the day and 30 min intervals at night. A diary is provided to record activity and sleep patterns. In addition to the 24-h blood pressure average, ABPM also provides information on blood pressure profiles, e.g. daytime and night time averages, the ‘dipper status’, i.e. the relationship between night time and day time blood pressure averages, blood pressure variability throughout the day, the morning surge in blood pressure, and—more recently indices—of aortic function via the ambulatory stiffness index. Each of these parameters adds value over and above the assessment of office blood pressure, hence such techniques are increasingly used for the assessment of people with hypertension. Clinical indications for the use of ABPM are shown in Bullet list 2.
|Table 1 Diagnostic thresholds for hypertension according to different methods of measurement|
|SBP (mmHg)||DBP (mmHg)|
|Office or clinic||140||90|
DBP, diastolic blood pressure; SBP, systolic blood pressure.
Home blood pressure measurements
The concept of patients measuring their own blood pressure at home is becoming increasingly popular and may improve adherence to treatment. Validated devices should be used, with an average of duplicate morning and evening home blood pressure measurements recorded daily for 7 days. The measurements should be recorded seated after 5 min rest, with those taken on the first day discarded, leaving at least 24 measurements to be averaged to obtain the home blood pressure average.
‘White coat’ or isolated office hypertension
In some patients office blood pressure is persistently elevated although their 24-h blood pressure or home blood pressure averages are within the normal range. This has been termed ‘white coat’ hypertension or isolated office hypertension. It is important to note that blood pressure will generally fall with repeated readings in all patients, hence it is the chronicity of the office blood pressure elevation that is important to establish the diagnosis.
White coat or isolated office hypertension should be diagnosed whenever office blood pressure is 140/90 mmHg or more on at least three occasions, while 24-h mean and daytime blood pressures are within their normal range. The diagnosis can also be based on home blood pressure values, i.e. average home readings below 135/85 mmHg and office values 140/90 mmHg or more.
Surveys suggest that white coat or isolated office hypertension may be present in as many as 15% of the general population and approximately one-third of all hypertensives. There is considerable debate about its prognostic significance: some studies report association with evidence of hypertensive target organ damage, but others do not. However, overall it appears that white coat hypertension is not benign, with the associated risk probably sitting between those with hypertension confirmed by office readings and ABPM, and those with definitively normal pressures by all methods of measurement. When white coat hypertension is diagnosed, the best advice is to monitor blood pressure and target organ damage via ABPM or home blood pressure averages and not treat unless these pressures are persistently elevated.
Bullet list 2 Possible indications for ambulatory blood pressure monitoring
- ◆ Unusual blood pressure variability
- ◆ Possible ‘white coat’ hypertension
- ◆ Informing equivocal treatment decisions
- ◆ Evaluation of nocturnal hypertension
- ◆ Evaluation of drug-resistant hypertension
- ◆ Determining the efficacy of drug treatment over 24 h
- ◆ Diagnoses and treatment of hypertension in pregnancy
- ◆ Evaluation of symptomatic hypotension
Less attention has been paid to masked hypertension, i.e. patients with a normal office blood pressure but elevated ABPM or home blood pressure averages, than to those with white coat hypertension. Estimates of prevalence range from 10 to 30% of the population, hence a normal office blood pressure does not exclude hypertension. Moreover, as home blood pressure measurement becomes more popular, the detection of masked hypertension will increase. These patients are more likely to have target organ damage and are at increased cardiovascular risk, perhaps more so than those with white coat hypertension. Masked hypertension should be considered in patients who have clinical evidence of hypertensive target organ damage, but in whom office blood pressure appears normal. Treatment should be offered to such patients, aimed at controlling the home blood pressure average.
Fundoscopy is the most convenient method of directly visualizing vascular pathology and provides important prognostic information. Signs of hypertensive retinopathy are frequently seen in adults 40 years and older, and are predictive of incident stroke, congestive heart failure, and cardiovascular mortality—independently of traditional risk factors.
The Keith Wagener classification of fundal appearances has been used for many years, but has serious shortcomings. This classification identified four grades of hypertensive retinopathy. Grade I and II changes, which result from arteriolar thickening, are often difficult to differentiate from each other, and the prognostic significance of the grade I and II subclassification is unclear. A more practical three-grade classification (i.e. mild, moderate, and severe) has been proposed (Table 2 below). The mild changes of generalized retinal–arteriolar narrowing and arteriovenous nipping are related to both the blood pressure at diagnosis and chronic exposure to an elevated blood pressure, hence they appear to be an index of the chronicity of blood pressure elevation. The changes of moderate hypertensive retinopathy are the changes of mild retinopathy plus flame-shaped or blot-shaped haemorrhages, cotton wool spots, hard exudates, microaneurysms, or a combination of all of these factors. Severe retinopathy (malignant or accelerated hypertension) is characterized by all of the aforementioned changes plus swelling of the optic disc. These moderate and severe fundal changes are more closely related to more recent elevation of blood pressure, suggesting they are the consequence of more transient and severe blood pressure elevation.
|Table 2 Modern classification of hypertensive retinopathy|
|Mild hypertensive retinopathy||Retinal arteriolar signs, such as generalized and focal arteriolar narrowing, arteriolar wall opacification, and arteriovenous nipping|
|Moderate hypertensive retinopathy||The signs above plus flame-shaped or blot-shaped haemorrhages, cotton-wool spots, hard exudates, microaneurysms, or a combination of all of these factors.|
|Severe hypertensive retinopathy||The signs above plus swelling of the optic disc|
Severe fundal changes are characterized by disc swelling (i.e. papilloedema) resulting from raised pressure in the disc head secondary to severe vascular damage and increased permeability. Venous distension is followed by increased vascularity of the optic disc, which has a pink appearance with blurring of the disc margins and loss of the optic cup. Raising of the optic disc with anterior displacement of the vessels occurs later. The surrounding retina often shows oedema, small radial haemorrhages, and cotton wool exudates. Moderate or severe fundal changes represent malignant or accelerated hypertension and carry the same adverse prognosis and should be treated as a medical emergency. The flame-shaped haemorrhages are superficial and shaped due to constraints imposed by nerve fibres. Dot and blot haemorrhages are deeper than the nerve fibres and thus are not so constrained. Haemorrhages usually disappear after a few weeks of effective blood pressure control. There are two types of exudates: hard or waxy exudates represent the end result of fluid leakage into the fibre layers of the retina from damaged vessels, with fluid reabsorption leaving a protein–lipid residue that is slowly removed by macrophages; soft exudates or cotton wool patches are usually larger than hard exudates and have a woolly, ill-defined edge, but they are not true exudates, rather nerve fibre infarcts caused by hypertensive vascular occlusion. Unlike hard exudates, these lesions disappear within a few weeks of establishing adequate antihypertensive therapy.
Other fundal changes associated with hypertension
Hypertension also predisposes to the development of a number of sight-threatening complications that can be detected by fundoscopy.
Retinal vein occlusion
This is characterized by dilated and tortuous retinal veins and the presence of retinal haemorrhages, cotton wool spots, and oedema of the macula and optic disc. In the case of central retinal vein occlusion, all four fundal quadrants are involved; only one fundal quadrant is involved if there is a branch vein occlusion. Central retinal vein occlusion can either be ischaemic or nonischaemic, patients with an ischaemic central retinal vein occlusion typically having poor visual acuity and a relative afferent pupillary defect. Ophthalmic follow-up is needed to diagnose and prevent the two main complications of retinal vein occlusion, namely neovascularization and macular oedema.
Retinal arteriolar embolization
Due to cholesterol crystals, platelet/fibrin clot, or calcium, this is twice as common in people with hypertension compared to those who are normotensive, with the risk further accentuated in cigarette smokers and those with diabetes.
Retinal artery occlusion
Also more common in people with hypertension, central retinal artery occlusion typically presents with a sudden, painless, unilateral loss of vision, associated with a cherry red spot. Branch retinal artery occlusion will present with a sudden, painless, visual field defect, and there may be only minimal impairment of central vision.
Retinal arterial macroaneurysms
These can be either fusiform or saccular. They are uncommon, but are usually only seen in patients with hypertension. When they occur, about 20% are bilateral and 10% are multiple. They are usually discovered by routine fundoscopy in asymptomatic hypertensive patients, but can present acutely, with visual loss secondary to haemorrhage or exudation.
Nonarteritic ischaemic optic neuropathy
This is also more common in people with hypertension, occurring (in one series) with a yearly incidence of 1 in 10 000. It presents with sudden unilateral visual loss and optic disc oedema. There is no effective treatment and prospects for visual recovery are poor.
All patients with hypertension should have a thorough physical examination (Bullet list 3). Aside from measurement of blood pressure and fundal examination as detailed above, particular features to look for are evidence of secondary effects of sustained hypertension on the heart, features that might suggest the presence of a secondary cause of hypertension, and evidence of other vascular pathology (absent pulses, arterial bruits).
Cardiac examination may reveal a sustained apex beat, or features of cardiac failure that might be secondary to hypertension. It is sometimes said that the second component of the aortic sound is loud in moderate or severe hypertension, but this is not a reliable finding.
In coarctation of the aorta the femoral pulses will be absent or diminished and delayed, and there may be various murmurs (usually as systolic murmur at the sternal border and a continuous murmur at the back of the chest), also visible or palpable collateral arteries on the back of the chest or in the axillae. Blood pressure measured in the legs will be lower than that in the arms.
Abdominal bruits are reported in 4 to 20% of normal people, most commonly in those aged less than 40 years, when it is typically systolic and audible only between the xiphisternum and the umbilicus. In patients with severe hypertension that is difficult to control, the finding of an abdominal bruit in both systole and diastole strongly supports the diagnosis of renovascular hypertension, but a bruit confined to systole is much less likely to be of significance.
Patients with essential hypertension need only a limited number of routine investigations, which must include:
- ◆ urine strip test for protein and blood
- ◆ serum creatinine and electrolytes
- ◆ blood glucose—ideally fasted
- ◆ lipid profile—ideally fasted
- ◆ ECG
Bullet list 3 Initial assessment of the patient with hypertension
- ◆ Causes of hypertension
- • Drugs (NSAIDs, oral contraceptive, steroids, liquorice, sympathomimetics, i.e. some cold cures)
- • Renal disease (present, past or family history, proteinuria and/or haematuria: palpable kidney(s)—polycystic, hydronephrosis, or neoplasm)
- • Renovascular disease (abdominal or loin bruit)
- • Phaeochromocytoma (paroxysmal symptoms)
- • Conn’s syndrome (tetany, muscle weakness, polyuria, hypokalemia)
- • Coarctation (radiofemoral delay or weak femoral pulses)
- • Cushings (general appearance)
- ◆ Contributory factors
- • Overweight
- • Excess alcohol (>3 units/day)
- • Excess salt intake
- • Lack of exercise
- • Environmental stress
- ◆ Complications of hypertension/target organ damage
- • Stroke, TIA, dementia, carotid bruits
- • LVH and/or LV strain on ECG, heart failure
- • Myocardial infarction, angina, CABG or angioplasty
- • Peripheral vascular disease
- • Fundal hemorrhages or exudates, papillodema
- • Proteinuria
- • Renal impairment (raised serum creatinine)
- ◆ Cardiovascular disease risk factors
- • Smoking
- • Diabetes
- • Total cholesterol:high-density lipoprotein-cholesterol ratio
- • Family history
- • Age
- • Sex
- ◆ Drug contraindications
CABG, coronary artery bypass graft; LVH, left ventricular hypertrophy; NSAIDs, nonsteroidal anti-inflammatory drugs; TIA, transient ischaemic attack.
These routine investigations help inform the assessment of target organ damage and cardiovascular disease risk. With regard to renal function, many laboratories now report an ‘estimated’ GFR (eGFR) calculated using an algorithm based on the serum creatinine measurement (see Chapters 21.4 and 21.6). If urinary stick testing for protein is positive, this should be followed by quantification on a spot urine sample of the urinary albumin/creatinine ratio (ACR). More sophisticated assessment tools are available, but the list above is sufficient for routine clinical practice. Note that only two of these routine investigations contribute to the detection of underlying causes of hypertension, namely urinalysis (renal causes) and serum creatinine and electrolytes (renal causes and mineralocorticoid excess), although the ECG may rarely show U waves as a clue to one of the hypokalaemic syndromes. Indications for further investigation for causes of secondary hypertension are given in this article: Secondary hypertension.
A chest radiograph and urine microscopy are not routinely required. Echocardiography is more sensitive at detecting left ventricular hypertrophy than an ECG, but is not required routinely, although it is valuable to confirm or refute the presence of left ventricular hypertrophy when the ECG shows voltage criteria suggestive of this.
Assessment of cardiovascular disease risk
The cardiovascular risk associated with hypertension is not eliminated by the treatment of blood pressure alone. This is because many patients have established cardiovascular damage which may not necessarily reverse with treatment of blood pressure, also lifestyle habits such as smoking and dietary factors that may not have changed since therapy was initiated. Other factors are also important: patients with high blood pressure often have associated disturbances in their metabolic profile (especially lipids and glucose tolerance) that also contributes to their risk, which has led many international guidelines to recommend that cardiovascular risk should be formally assessed in all patients with hypertension to determine whether they are at low, medium, or high risk.
Risk calculations based on the Framingham cohort have been used in the United States of America and the United Kingdom, and European guidelines have used a risk score based on mortality data from European countries. Pragmatism in risk assessment is important, with the risk factors cited in the guidelines being conventional markers that can easily be documented in a basic clinical setting, i.e. systolic blood pressure, age, gender, low-density lipoprotein (LDL) cholesterol, presence of diabetes, smoking history, and the presence or absence of structural damage, e.g. ECG evidence of left ventricular hypertrophy. Recent surveys suggest that >90% of population attributable risk for cardiovascular disease can be explained by these risk factors. The use of more sophisticated risk assessment by adding any of the recently advocated biomarkers, such as C-reactive protein, adds little to the conventional methods of cardiovascular risk estimation.
Cardiovascular disease risk thresholds for intervention currently define ‘high risk patients’ as having a 10-year Framingham-derived cardiovascular disease risk of 20% or more. The typical hypertensive male aged 55 years or more has this level of cardiovascular disease risk, and it is likely that even lower thresholds would be cost-effective for intervention. Formal cardiovascular disease risk estimation is not necessary for patients with hypertension and established cardiovascular disease, diabetes, or overt end organ damage: they are already at sufficient cardiovascular disease risk to benefit from multifactorial risk factor intervention.
Patients with hypertension and deemed to be at high risk should receive strong advice to adjust their lifestyles and be considered for treatment with statin therapy and low dose aspirin to optimize their risk reduction (see below).
Blood pressure is elevated sporadically in everybody. Key objectives in the assessment of essential hypertension are to establish whether blood pressure is persistently elevated; the level to which blood pressure is elevated, i.e. the severity of hypertension; and the presence or absence of hypertension-mediated target organ damage. The initial assessment is usually followed by a period of observation, the duration of which will be dependent on the severity of the hypertension and the associated cardiovascular disease risk and damage. Lifestyle advice should be provided during this observation period, with drug therapy initiated depending on the level of blood pressure and overall cardiovascular disease risk at the end of the observation period.
Establishing the diagnosis
Patients with essential hypertension usually present in one of three ways:
- ◆ As an asymptomatic individual whose blood pressure has been measured at routine examination for employment, insurance, or as a result of screening or preoperatively—the most common presentation
- ◆ As a patient whose blood pressure has been measured opportunistically when presenting with an unrelated disorder; or
- ◆ As a result of symptoms produced by hypertension, or by the acute or chronic complications of hypertension—the least common presentation
Repeated blood pressure measurements over a period of observation are usually necessary to establish the diagnosis. Exceptions to this are patients presenting with severe hypertension in whom fundal examination or other assessment of target organ damage (e.g. left ventricular hypertrophy or renal impairment) clearly reveals the presence of hypertension-mediated damage, indicative of the fact that the blood pressure needs treatment.
The period of observation required before initiating drug therapy is dependent on the severity of the hypertension and the presence or absence of cardiovascular disease, diabetes and/or target organ damage. Those with more severe hypertension and disease require emergency or urgent intervention with drug therapy to lower their blood pressure, whereas those with less severe hypertension and/or the absence of damage or disease can be monitored over a longer period—up to many months—before initiating drug therapy. This period of observation is important because it is used to repeat blood pressure measurements, confirm the presence of sustained hypertension, and get a more accurate appreciation of the associated risk, also to implement lifestyle interventions that may reduce blood pressure.
Diagnostic thresholds for therapeutic intervention and the observation period
The diagnostic thresholds for the levels of hypertension severity are shown in Table 1 above, and the recommended period of observation for different grades of hypertension are shown in Table 3 below. Although there is general consensus about the management of grade II (i.e ≥160/100 mmHg) or more severe hypertension, the British guidelines have traditionally been more cautious than other guidelines with regard to drug therapy for uncomplicated grade I hypertension (140–159/90–99 mmHg) (Table 3). Most other guidelines recommend treating all patients with a blood pressure sustained above 140/90 mmHg, whereas the British guidelines have recommended drug therapy for those with grade I hypertension only when there is associated cardiovascular disease or target organ damage, or a calculated risk of cardiovascular disease at least 20% over 10 years. There is genuine uncertainty about the cost-effectiveness of treating otherwise low risk people with grade I hypertension, but this must be balanced by recognition that the greatest burden of blood pressure attributable disease in populations is in those with grade I hypertension because it is so common. Moreover, blood pressure will invariably continue to rise in patients with grade I hypertension, and there is concern that the subtle vascular damage that is occurring while these patients remain untreated may not be reversible when treatment is eventually initiated at higher levels of pressure. Thus, while a prolonged period of observation and lifestyle intervention for uncomplicated, low risk, grade I hypertension is considered acceptable, it is inevitable that most of these patients will eventually (if not immediately) require drug treatment.
|Table 3 Typical observation periods for different grades of hypertension and associated cardiovascular disease, diabetes, and/or target organ damage|
|Grade of hypertension||Typical observation period|
|Accelerated (malignant) hypertension (papilloedema and/or fundal haemorrhages and exudates or with acute cardiovascular complications e.g. aortic dissection)||Immediate treatment—usually requiring acute hospital admission|
|BP ≥220/120 mmHg||Treat immediately—hospital admission not usually required|
||Confirm by repeated measurements over 1–2 weeks, then treat|
From Williams. B et al. (2004). BMJ, 328, 364–40
The treatment of hypertension is directed towards reducing risk rather than treating symptoms. It is imperative, therefore, to explain the significance of high blood pressure at the earliest opportunity. Many patients find difficulty in grasping the concept of blood pressure variability and are often alarmed by the inevitable occasional high reading. Discussion of the rationale for evaluation and treatment, together with an explanation of the nature of high blood pressure and its very high prevalence, reassures patients and may improve adherence to treatment. Further comprehensive advice for patients may be obtained from http://www.bpassoc.org.uk.
The evidence base identifying the optimal blood pressure treatment targets for hypertension is less substantial than it should be. There is international consensus that for office blood pressure an optimal treatment target should be <140/90 mmHg, and a lower target of <130/80 mmHg has been recommended for higher risk patients, i.e. those with established cardiovascular or renal disease or diabetes. Whether such targets are appropriate for very elderly individuals (i.e. >80 years) has been debated, with a recent study suggesting that at target blood pressure of <150/90 mmHg is appropriate for this age group. It is important to note that as people age, diastolic blood pressure generally falls and systolic blood pressure rises, hence the systolic blood pressure assumes the greatest importance with regard to the treatment target, although it is generally more difficult to control.
Blood pressure is strongly influenced by lifestyle factors such as diet and exercise and their consequences such as weight. Effective lifestyle modification for patients with grade I hypertension may lower blood pressure as much as a single blood pressure lowering drug, and combinations of two or more lifestyle modifications may be even more effective. Lifestyle interventions may reduce the need for drug therapy for people with mild hypertension, can enhance the antihypertensive effects of blood pressure lowering medication, and can favourably influence overall cardiovascular disease risk.
The most effective lifestyle interventions for reducing blood pressure in clinical trials are modifications to diet to induce weight loss, regular aerobic exercise, and restrictions in alcohol and sodium intake. The expected reduction in blood pressure with these lifestyle manoeuvres are shown in Table 4 below, and recommended lifestyle interventions to reduce blood pressure and/or cardiovascular disease risk are shown in Bullet list 4.
Patients are often enthusiastic to try lifestyle changes rather than take drug therapy. This is a reasonable initial option in patients with grade I hypertension who do not have associated target organ damage or high cardiovascular disease risk. In patients with more severe hypertension or those at high risk, lifestyle measures should be recommended alongside drug therapy. This is important because these measures may improve the effectiveness of drug therapy and also contribute to a reduction in overall cardiovascular risk. Note, however, that effective implementation of lifestyle measures requires enthusiasm, knowledge, patience, and considerable time spent with patients and other family members. It is best undertaken by well-trained health professionals, e.g. practice or clinic nurses, and should be supported by clear written information.
|Table 4 Blood pressure reductions associated with lifestyle interventions for patients with hypertension|
|Intervention||Recommendation||Expected SBP reduction (range)|
|Weight reduction||Maintain ideal BMI 20–25 kg/m2)||5–10 mmHg per 10 kg weight loss|
|DASH eating plan||Consume diet rich in fruit, vegetables, low fat dairy products with reduced content of saturated and total fat||8–14 mmHg|
|Dietary sodium restriction||Reduce dietary sodium intake to <100 mmol/day (<2.4 g sodium or <6 g sodium chloride)||2–8 mmHg|
|Physical activity||Engage in regular aerobic physical activity, e.g. brisk walking lor at least 30 min most days||4–9 mmHg|
|Alcohol moderation||Men ≤21 units/week||2–4 mmHg|
|Women ≤14 units/week|
BMI, body mass index; SBP, systolic blood pressure.