General Cardiology Part 5
There are no large randomized clinical trials available to evaluate different drug therapy in symptomatic patients with HOCM. Since most symptoms from HOCM are related to left ventricular outflow tract obstruction which occurs during systole, medical therapy is aimed at lowering the heart rate to allow better diastolic filling and using negative inotropic agents to decrease the force of contractility.
Non-dihydropyridine calcium channel blockers such as verapamil are commonly used. These drugs slow the heart rate and decrease the inotropic force of LV contraction relieving the symptoms of HCOM.
Beta-blockers act similar to the above in mechanism in HOCM patients.
Disopyramide is the historical treatment for HOCM. This drug has significant negative inotropic effects, however is considered an antiarrhythmic drug. It is currently recommended only for persistent symptoms if non-dihydropyridine calcium channel blockers and beta-blockers fail. Patients on disopyramide should also take one of the above concomitantly since disopyramide enhances AV nodal conduction and should atrial fibrillation/flutter develop, it will very rapidly conduct to the ventricles. Disopyramide can prolong the QT interval resulting in polymorphic ventricular tachycardia in some patients. There are significant anticholinergic side effects including xerostomia (dry mouth), urinary retention, visual disturbances and decreased perspiration.