Cardiac muscle mass during vasodilation therapy of hypertension.

M-mode echocardiography has become a valuable tool in the evaluation of changes in left ventricular muscle mass during antihypertensive therapy. We evaluated the effects of treatment with the vasodilator trimazosin, alone and in combination with the diuretic polythiazide, on cardiac muscle mass in hypertensive subjects. Trimazosin alone was given to 11 subjects for 18 mo, and average supine blood pressure fell from 154/100 to 146/89 mm Hg. Heart rate and body weight did not change during therapy. Initially, a slight decrease (approximately 6%) was observed in left ventricular muscle mass, but left ventricular transverse dimension and left ventricular muscle mass returned to control levels during the last 6 mo of the 18-mo study. The combination of trimazosin and polythiazide was given to nine subjects and decreased blood pressure from 152/102 to 138/92 mm Hg. Heart rate increased and body weight decreased slightly. No changes in left ventricular muscle mass were observed during combination therapy. It is possible that increases in activity of the sympathetic nervous system during therapy with trimazosin alone, and the observed increase in renin activity during treatment with trimazosin and polythiazide, might have offset the effects of the reduction in blood pressure on left ventricular muscle mass.