Acute intravenous versus chronic oral drug effects of verapamil on left ventricular diastolic function in patients with hypertrophic cardiomyopathy.

The effects of acute intravenous (i.v.) versus long-term oral (p.o.) verapamil administration on diastolic function were studied in 20 patients with hypertrophic cardiomyopathy (HCM). We used a tip manometer catheter to record left ventricular pressure (LVP) tracings and a nuclear probe to measure LV volume changes. Infusion of verapamil resulted in an increase in time constant of relaxation (+15%, p < 0.001); LV peak filling rate, heart rate (HR), and stiffness constant of the diastolic pressure-volume relation were unchanged. During 18-week p.o. verapamil treatment, HR decreased (-16%, p < 0.0005) and the atrial contribution to LV filling decreased (-27%, p < 0.05); other parameters differed significantly from baseline values. Results demonstrate that acute i.v. versus long-term p.o. verapamil administration have different effects on diastolic function in HCM.