Verapamil therapy: a new approach to the pharmacologic treatment of hypertrophic cardiomyopathy. II. Effects on exercise capacity and symptomatic status.

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Abstract
Treadmill exercise capacity and symptomatic status were evaluated in 19 patients with hypertrophic cardiomyopathy while on placebo, low and high dosages of propranolol and low and high dosages of verapamil. Exercise duration on placebo was 6.1 .+-. 0.8 min. Verapamil administration improved exercise capacity by 26 .+-. 8% (1.6 .+-. 0.5 min; P < 0.005); propranolol improved exercise capacity by 21 .+-. 8% (1.3 .+-. 0.5 min; P < 0.025). Twelve patients on verapamil and 11 on propranolol improved their exercise duration by at least 15% compared with placebo. No patient on verapamil but 13 on propranolol had more than 15% deterioration in exercise capacity. Seven patients considered their symptomatic status best while on placebo, 9 while on verapamil, and only 3 while on propranolol. There was no correlation between the exercise or symptomatic response to oral verapamil and the reduction in left ventricular outflow tract obstruction with i.v. verapamil administration. Repeat exercise testing 3.5-6 mo. after completion of the study in 8 patients discharged on chronic verapamil therapy showed exercise capacity improved 45 .+-. 15% (P < 0.025) compared with placebo and 21 .+-. 5% (P < 0.005) above values obtained on verapamil in hospital. Of 15 patients discharged on verapamil, 11 reported symptomatic benefit and 6 improved their functional class by at least 1 grade. Verapamil can improve exercise capacity and symptomatic status in certain patients with hypertrophic cardiomyopathy, thereby providing physicians with a new therapeutic agent to treat this disorder.