Chapter

Diagnosis, assessment, and treatment of essential hypertension

Bryan Williams

in Oxford Textbook of Medicine

Fifth edition

Published on behalf of Oxford University Press

Published in print May 2010 | ISBN: 9780199204854
Published online May 2010 | e-ISBN: 9780199570973 | DOI: http://dx.doi.org/10.1093/med/9780199204854.003.161702

Series: Oxford Textbooks

Diagnosis, assessment, and treatment of essential hypertension

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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?

Diagnosis

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 Chapter 16.17.1.

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).

Management

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.

Chapter.  14941 words.  Illustrated.

Subjects: Cardiovascular Medicine

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