Long-term hemodynamic effects of antihypertensive treatment.

The cardinal hemodynamic disorder in established essential hypertension is increased total peripheral resistance. During exercise, the increase in stroke volume of the heart is abnormal. A 20-year follow-up study of the hemodynamics in essential hypertension demonstrated a progressive increase in total peripheral resistance and deterioration of the heart pump function. Long-term treatment with antihypertensive agents modifies the circulatory system in different ways. Vasodilators (angiotensin converting enzyme inhibitors, alpha 1-blockers, and calcium antagonists) all reduce total peripheral resistance, and in general, cardiac output, heart rate, and stroke volume remain unchanged. Calcium antagonists like verapamil and diltiazem reduce the heart rate approximately 10% during exercise, but since stroke volume increases, cardiac output is unchanged. Chronic treatment with conventional beta-blockers induces a permanent reduction in cardiac output and heart rate during exercise. In contrast, carvedilol--a beta 1,beta 2-blocker with alpha 1-blocking activity--prevents the immediate increase in total peripheral resistance during acute beta-blockade. In 19 patients followed by hemodynamic measurements over 6-9 months, blood pressure was well controlled by carvedilol. During exercise, total peripheral resistance decreased 6% (P less than 0.05), and the reductions in heart rate and cardiac index were less than on conventional beta-blockade. Echo-Doppler studies showed a significant reduction in the intraventricular septum of 13%.