Hypertension in the elderly
Hypertension in the elderly, including isolated systolic hypertension
Hypertension in the elderly is very common. There is now convincing evidence from multiple controlled clinical trials that treatment of hypertension in the elderly has large beneficial effects on the progress of cardiovascular disease, including development of stroke, coronary heart disease, and congestive heart failure. Thiazide diuretics and calcium channel blockers reduce the risk of these adverse cardiovascular endpoints in the elderly [The Systolic Hypertension in the Elderly Program Cooperative Research Group 1993; Joint National Committee 1997; Staessen et al. 1997]. It may be prudent to initiate therapy with particularly low starting doses of these drugs in the elderly. Therapeutic goals (blood pressure < 140/90) should generally be the same as in younger patients. However, for some elderly patients it may be hemodynamically challenging to markedly lower elevated systolic blood pressure (see below for discussion of isolated systolic hypertension). In those patients, more modest goals for reduction of systolic hypertension may be more appropriate, such as decreases of systolic pressure to less than 160 mm Hg. The elderly may have impaired buffering capacity to control blood pressure in the upright position. As a consequence, drugs that are more likely to cause postural hypotension, such has high-dose diuretics, α1-adrenergic receptor antagonists, and drugs interfering with sympathetic nervous system function, should be avoided or used particularly cautiously in the elderly.
Systolic blood pressure is a better predictor of cardiovascular complications than is diastolic blood pressure. Systolic blood pressure may rise markedly with age. This is thought to predominantly relate to age-associated reduction in the compliance of the large arteries. Normally, ejection of the stroke volume from the left ventricle into the aorta stretches the aortic wall. During diastole, blood flows down the arterial tree as the large vessels contract. This windkessel effect is useful in distributing the cardiac output more evenly between systole and diastole. With loss of the windkessel effect, systolic pressure is raised, and diastolic pressure tends to fall, in part, because of the more rapid return to the aorta of the reflected pressure wave in the less compliant vasculature. In addition, augmented reflection contributes to pressure overload of the left ventricle and left ventricular hypertrophy.
In the absence of other complicating factors, the pulse pressure (systolic minus diastolic pressure) is a reasonable index of large artery compliance; the index widens with decreased compliance. The mean arterial pressure is a reasonable index of blood pressure=cardiac output × systemic vascular resistance irrespective of changes in aortic wall compliance . This concept of systemic hemodynamic change during aging accounts for the observed trends in blood pressure. Isolated systolic hypertension (systolic >160 and diastolic <90 mm Hg) is largely a disease of the elderly.
There is now strong evidence from randomized controlled clinical trials demonstrating the effectiveness of drug therapy for isolated systolic hypertension. The Systolic Hypertension in the Elderly Program study [Cooperative Research Group 1993] demonstrated that a diuretic combined with atenolol as second-step therapy, compared with placebo, significantly decreases stroke, acute myocardial infarction, heart failure, and death due to coronary artery disease. The therapeutic goal for systolic blood pressure in that study was less than 140 mm Hg. Furthermore, a European study of isolated systolic hypertension in the elderly demonstrated that the calcium-entry blocker nitrendipine causes a marked reduction in risk for stroke in the treated patients.
Although there was skepticism in the 1980s about the value of treating diastolic or isolated systolic hypertension in the elderly, randomized clinical trials have demonstrated that drug treatment of these problems in the elderly has a major impact on cardiovascular complications. As a consequence, treatment of these patients is strongly encouraged based on available evidence. On the other hand, relatively little is known about the capacity of various antihypertensive drugs, more often used to treat diastolic hypertension, to decrease blood pressure in patients with isolated systolic hypertension. Whether it is beneficial to lower blood pressure with isolated systolic hypertension with initial values of systolic pressure between 140 and 160 mm Hg is unknown.
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