Systolic hypertension: occurrence and treatment in a defined community

Management of isolated systolic hypertension

Isolated systolic hypertension (ISH) [systolic blood pressure (SBP) > or = l60mm Hg with diastolic blood pressure (DBP) <90mm Hg] is the commonest form of hypertension in the elderly, and accounts for about 60% of all hypertensive conditions in the population aged over 65 years. It is associated with a significantly increased risk of cardiovascular and cerebrovascular morbidity and mortality. The landmark Systolic Hypertension in the Elderly Program (SHEP) study, published in 1991, has shown that lowering the SBP in elderly patients with ISH results in a significant reduction in cardiovascular events. These results have had a major impact on clinical practice in hypertension. On theoretical grounds, considering the pathophysiological mechanisms of ISH in the elderly, any drug which lowers total peripheral resistance and/or arterial stiffness should reduce SBP effectively in these patients. This effect has been observed in outcome studies and short term clinical trials using a variety of drugs from the 4 major antihypertensive classes: diuretics, beta(1)-blockers, calcium channel antagonists and ACE inhibitors. Other drugs, including alpha antagonists, may also be effective. In general, there is compelling evidence to support active treatment of any individual with an SBP > or = 160mm Hg. As in essential hypertension, the maximum benefit is gained by aggressive treatment of those individuals at highest risk because of coexisting cardiovascular risk factors. In these people, an SBP of 140 to 159mm Hg should be considered to be an indication for active management. Initial management should be by manipulation of lifestyle factors such as bodyweight, salt and alcohol intake and aerobic exercise. Drug therapy, generally well tolerated in low doses, should be considered if SBP remains > or = 160mm Hg, or > or = 140mm Hg in the presence of multiple risk factors. The choice of initial drug therapy should be influenced by the particular clinical situation. If there are no coexisting contraindications or co-indications for particular drugs, it is reasonable to begin treatment with a low dose of a thiazide-like diuretic, as used in the SHEP study. However, in short term treatment trials calcium channel antagonists and ACE inhibitors have been shown to lower SBP effectively and can be used in the appropriate clinical context. Beta-blockers appear to be less effective as monotherapy in ISH. Combination therapy is frequently required and can be effective and well tolerated if carefully chosen.

Systolic hypertension in the elderly

Historically diastolic blood pressure (BP) rather than systolic BP has been regarded clinically as the more important component related to subsequent hypertensive morbidity and mortality, and treatment has thus been directed towards lowering the diastolic BP. Observational studies across many different populations have related cerebrovascular disease and death more to the systolic BP, which appears selectively to increase as the population ages. Isolated systolic hypertension (ISH), therefore, may be more prevalent as westernized societies become older. Those affected with ISH suffer a two- to fivefold increase in rates of stroke and ischemic heart disease compared to normotensives. Currently no clinical trials data exist for ISH showing the efficacy of antihypertensive therapy upon final morbidity and mortality, but a large-scale multicenter clinical trial, the Systolic Hypertension in the Elderly Program (SHEP), is currently underway in the United States. Results are expected in the early 1990s. If the results of this trial confirm the efficacy of treating ISH, the therapeutic challenge of ISH will be to selectively decrease systolic BP without undue side effects.

Systolic Hypertension in the Elderly Program (SHEP): antihypertensive efficacy of chlorthalidone

The Systolic Hypertension in the Elderly Program (SHEP) is a randomized, blinded test of the efficacy of antihypertensive drug treatment. In a large feasibility trial, 551 men and women who had isolated systolic hypertension and were at least 60 years old received chlorthalidone (25 to 50 mg/day) or matching placebo as the step I drug. After 1 year, 83% of the chlorthalidone group and 80% of the placebo group were still taking SHEP medications. Of those still taking chlorthalidone, 88% had reached goal blood pressure (BP) without requiring a step II drug, and most had responded to the lower dose (25 mg/day). The BP response was similar in all age, sex and race subgroups, with an overall mean difference between randomized groups of 17 mm Hg for systolic BP (p less than 0.001) and 6 mm Hg for diastolic BP (p less than 0.001). The only common adverse effects were asymptomatic changes in the serum levels of potassium (0.5 mEq/liter lower in the chlorthalidone group, p less than 0.001), uric acid (0.9 mg/dl higher, p less than 0.001) and creatinine (0.08 mg/dl higher, p = 0.02). This study indicates that chlorthalidone is effective for lowering BP in elderly patients with systolic hypertension and sets the stage for a larger trial of the effects of such treatment on the incidence of cardiovascular disease.

Comparison of the effects of diuretic therapy and low sodium intake in isolated systolic hypertension

Of 103 patients with isolated systolic hypertension, 71 were treated with diuretics and another 32 with low-sodium diet. In the 71 who were treated with diuretics, body weight decreased from 69.48 +/- 1.47 to 68.60 +/- 1.45 kg (p less than 0.0005) and systolic blood pressure from 178 +/- to 152 +/- 2 mm Hg (p less than 0.0005). Plasma renin activity increased from 1.78 +/- 0.30 to 7.32 +/- 1.78 ng/ml per hour (p less than 0.005) and urinary aldosterone from 10 +/- 1 to 23 +/- 4 micrograms per 24 hours (p less than 0.005). The greatest decrease in systolic blood pressure occurred in patients in the low-renin group (-32 +/- 2 mm Hg), whereas it decreased by 24 +/- 2 mm Hg (p less than 0.04) in the normal-renin group; however, blood pressure did not change significantly in the high-renin group. In the 32 patients who were treated with low-sodium diet, the 24-hour urinary sodium excretion decreased from 143 +/- 10 to 48 +/- 5 meq (p less than 0.005), body weight decreased from 71.18 +/- 2.50 to 70.17 +/- 2.47 kg (p less than 0.005), systolic blood pressure decreased from 174 +/- 2 to 156 +/- 3 mm Hg (p less than 0.0005), and diastolic blood pressure decreased from 90 +/- 1 to 87 +/- 1 mm Hg (p less than 0.01). Plasma renin activity increased from 2.25 +/- 0.33 to 4.27 +/- 0.43 ng/ml per hour (p less than 0.005) and urinary aldosterone from 9 +/- 1 to 15 +/- 2 micrograms per 24 hours (p less than 0.005). The decrease in the systolic blood pressure was related to the pretreatment 24-hour urinary sodium excretion (r = 0.40, p less than 0.05). The smallest decrease in systolic blood pressure occurred in the patients with high renin values (-1 +/- 9 mm Hg, n = 5), whereas the decrease in systolic blood pressure in the low-renin (n = 12) and normal-renin groups (n = 15) was similar, -22 +/- 2 mm Hg and -21 +/- 3 mm Hg, respectively (p less than 0.005 compared with the high-renin group). These results indicate that both diuretic therapy and low-sodium diet are effective antihypertensive means in most patients with isolated systolic hypertension and low or normal plasma renin activity.

Renin dependency of blood pressure in isolated systolic hypertension

The role of the renin system in the maintenance of the elevated systolic blood pressure in isolated systolic hypertension was investigated in 31 patients who received long-term treatment with propranolol (120 mg daily) and in another group of 22 patients with isolated systolic hypertension who received a test dose of captopril (25 or 50 mg). The greatest systolic blood pressure decrease (35 +/- 5 mm Hg) by propranolol occurred in the high-renin group (n = 9), and the smallest decrease (3 +/- 2 mm Hg) in the low-renin group (n = 9), whereas in the normal-renin group (n = 13), systolic blood pressure was decreased by propranolol by 22 +/- 5 mm Hg. For all the propranolol-treated patients, the decrement in the systolic blood pressure by propranolol was related to the control plasma renin activity (r = 0.63, p less than 0.01) and to the concurrent change in plasma renin activity (r = 0.70, p less than 0.001). Captopril decreased the systolic blood pressure by 55 +/- 10 mm Hg in the high-renin group (n = 11) and by 17 +/- 5 mm Hg in the normal-renin group (n = 6), whereas the smallest decrease (12 +/- 5 mm Hg) in systolic blood pressure occurred in the low-renin group (n = 5). In all the captopril-tested patients (n = 22), the decrease in systolic blood pressure by captopril was related to the control plasma renin activity (r = 0.75, p less than 0.001). These results indicate that the plasma renin activity value indicates the participation of the renin-angiotensin system in the maintenance of the elevated systolic blood pressure in patients with isolated systolic hypertension.

Effects of diuretic therapy in low-, normal- and high-renin isolated systolic systemic hypertension

In 30 patients with isolated systolic systemic hypertension, diuretic therapy decreased body weight from 71.33 +/- 2.67 to 70.37 +/- 2.65 kg (p less than 0.0005) and the systolic blood pressure from 174 +/- 3 to 156 +/- 3 mm Hg (p less than 0.0005). Diastolic blood pressure and heart rate did not change significantly. Plasma renin activity increased from 2.25 +/- 0.33 to 4.27 +/- 0.43 ng/ml/hour (p less than 0.0005) and urinary aldosterone from 9 +/- 1 to 16 +/- 2 micrograms/24 hours (p less than 0.005). The antihypertensive effect of diuretics was significantly related only to the pretreatment plasma renin activity (r = -0.50, n = 30, p less than 0.05), and therefore the greatest decrease in systolic blood pressure occurred in the low-renin group, whereas the smallest occurred in the high-renin group (-22 +/- 2 vs -3 +/- 9 mm Hg, p less than 0.005). The diastolic blood pressure was significantly decreased only in the low-renin group (-7 +/- 2 mm Hg, p less than 0.005). There were no significant changes in blood pressure in 11 untreated control patients. These results indicate that diuretics are effective antihypertensive agents in most patients with low- and normal-renin isolated systolic systemic hypertension.

[Blood pressure in the aged]

The study, based on datas of an inquiry by the association for the study of problems of the elderly, shows the epidemiology of arterial hypertension in a population aged over 65 years. 46% of the 48o examined persons from Basel and Berne had diastolic blood pressure values greater than or equal to 95 mmHg. 40% of those hypertensives were treated under control, 12% treated without control, 13% not treated at all, and 35% unknown. The percentage of the unknown hypertensives suggests, that the recording of the increased blood pressure is improvable in this age group. The high prevalence of hypertension in the elderly population as well as the grave consequences complications caused by hypertension should call our attention to the recording and treatment of arterial hypertension in the elderly.

Hypertension in the elderly: the time has come to treat

Both pure systolic, and systolic plus diastolic hypertension are risk factors for cerebrovascular and cardiovascular disease in patients over 65 years old, but the efficacy of antihypertensive therapy in preventing the complications of hypertension in the elderly has been questioned. The risks associated with such therapy seem to have been overemphasized. Although the evidence is incomplete, elderly patients should be treated when the systolic blood pressure exceeds 160 mm Hg or the diastolic pressure exceeds 95 mm Hg, or both. A revised stepped-care approach, with use of vasodilating agents as the Step-2 drugs, is proposed.