Divergent cardiac response to exercise in essential hypertension vs. normotension and the effect of enalapril.

The aims of this study were to examine (1) the cardiac response to exercise in essential hypertension and (2) the effect of long-term enalapril treatment on cardiac reserve. Ten normotensive control subjects and 15 patients with moderate, essential hypertension underwent radionuclide ventriculography during graded, supine exercise (0 W-50 W-100 W). The hypertensive patients were studied during monotherapy using hydrochlorothiazide and 3 and 12 months after supplementation with enalapril 10-40 mg o.d. During exercise, the control subjects demonstrated a 17% increase in left ventricular ejection fraction (LVEF) mediated by a 30% decrease in end-systolic volume, a small increase in stroke volume and a minor biphasic (increase-decrease) change in end-diastolic volume. In the hypertensive patients, both the end-diastolic and the end-systolic volume increased substantially with no increase in LVEF, although stroke volume increased by 33%. Long-term therapy with enalapril induced only a minor change towards a more normal pattern of cardiac response to exercise. The hypertensive patients increased their stroke volume during exercise by recruiting preload reserve instead of increasing contractility. Long-term treatment with enalapril had little, if any, effect on this abnormal cardiac response.