Influence of verapamil on diastolic left ventricular function in myocardial hypertrophy of different origin.

The effect of 0.1 mg/kg verapamil on left ventricular (LV) diastolic mechanics was evaluated in ten patients with hypertrophic cardiomyopathy and 13 patients with aortic stenosis. LV diastolic function was assessed from simultaneous M-mode echocardiograms and high-fidelity pressure measurements at rest and 10 to 15 min after intravenous administration of verapamil. The time constant of LV pressure decay (T), LV early and mean diastolic filling rate as well as diastolic pressure-diameter relations, were determined before and after verapamil administration. Heart rate, LV peak systolic pressure, maximum and minimum dP/dt remained unchanged in both groups after verapamil administration. LV end-diastolic pressure increased slightly although significantly from 15 to 17 mm Hg (P less than 0.02) in aortic stenosis but remained unchanged in hypertrophic cardiomyopathy. T decreased significantly from 79 to 60 ms (P less than 0.001) in hypertrophic cardiomyopathy but increased from 53 to 68 ms (P less than 0.025) in aortic stenosis. Parallel to the decrease in T, early and mean diastolic lengthening rate increased significantly in hypertrophic cardiomyopathy, but remained unchanged in aortic stenosis before and after verapamil. The diastolic pressure-diameter relation was not affected in both groups by verapamil administration. However, cycle efficiency improved significantly from 71% to 77% (P less than 0.02) in cardiomyopathy but remained unchanged in aortic stenosis (80% versus 80%). Thus, it is concluded that verapamil improves relaxation in hypertrophic cardiomyopathy but delays relaxation in aortic stenosis. The beneficial effect of verapamil in hypertrophic cardiomyopathy is related to improved relaxation and diastolic filling rather than to changes in passive elastic chamber properties.(ABSTRACT TRUNCATED AT 250 WORDS)