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)