Hypertrophic cardiomyopathy--therapy with slow channel inhibiting agents.

Slow channel inhibiting agents, particularly verapamil, appear to produce beneficial effects in relieving symptoms of dyspnea, chest pain, and syncope or presyncope in over 70% of patients with hypertrophic cardiomyopathy. Symptomatic relief occurs in patients with and without left ventricular outflow obstruction. Exercise hemodynamics, exercise tolerance, and cardiac performance during exercise tend to improve. The mechanisms for this symptomatic improvement, however, are not fully explained. Relief of symptoms is observed irrespective of any changes in the resting or provocable left ventricular outflow gradient. Similarly, changes in left ventricular systolic function, which in general remains unaffected, cannot be the basis for the beneficial response. Slow channel inhibiting agents, however, appear to improve left ventricular diastolic function, the mechanism of which is yet to be elucidated. Nevertheless, improved left ventricular diastolic function may provide an explanation for the relief of some symptoms in patients with hypertrophic cardiomyopathy. The influence of therapy with slow channel inhibiting agents on arrhythmias, sudden death, and on long-term prognosis of patients with hypertrophic cardiomyopathy remains uncertain at the present time and should be the subject of future investigations.