Verapamil therapy: A new approach to the pharmacologic treatment of hypertrophic cardiomyopathy: III. Effects of long-term administration

Abstract

To determine the efficacy of long-term therapy with verapamil in patients with hypertrophic cardiomyopathy, 78 patients began treatment with the drug in the hospital. Sixty-two patients (79 percent) were in New York Heart Association functional class III or IV despite treatment with beta receptor blocking drugs. Fifty-four percent of all patients evaluated (42 of 78) and 63 percent of those discharged from the hospital (42 of 68) experienced sustained symptomatic improvement 6 to 30 months (median 14 months) after initiation of verapamil therapy. Of these 42 patients in improved condition, 25 had improvement by at least one New York Heart Association functional class, 14 improved by less than one functional class, two felt better taking verapamil than propranolol, and in one patient verapamil controlled asymptomatic ventricular tachycardia. Of the 53 patients who had the obstructive form of the disorder and were considered operative candidates, 25 (47 percent) experienced sufficient improvement so as to forgo operation. In patients remaining on verapamil therapy, the duration of treadmill exercise performed 5 days after the start of verapamil therapy increased by 3.1 ± 0.6 minutes (53 ± 10 percent, p < 0.001) from the value obtained with no medication before verapamil. A further increase of 2.3 ± 0.6 minutes (25 ± 7 percent, p < 0.0025) over the initial value with verapamil was recorded on the patients' last vistt (median 12 months after the start of therapy). Echocardiographic measurements of wall thicknesses and left atrial dimension demonstrated no significant changes during 1 year of verapamil treatment in 31 patients. Administration of verapamil was associated with adverse hemodynamic effects in 9 patients (12 percent) and adverse electrophysiologic effects In 10 (13 percent): Three patients died (with pulmonary edema) and 6 had to have treatment terminated. These results indicate an important role for long-term verapamil therapy in the treatment of hypertrophic cardiomyopathy, but patients must be carefully selected and followed up closely for the development of important adverse hemodynamic or electrophysiologic effects.