Potential mechanisms of improvement after various treatments for hypertrophic obstructive cardiomyopathy

In sum, systolic dysfunction of the ventricle associated with left ventricular outlet obstruction and often with mitral valve regurgitation may be improved by myotomy, myomectomy, mitral valve replacement, and perhaps by the creation of left bundle branch block via DDD right ventricular pacing. Diastolic dysfunction of the ventricle may be improved by prolonging the diastolic filling period, shortening the isovolumic relaxation period with calcium channel blocking drugs, or perhaps by altering the atrioventricular activation time with a DDD pacemaker. The symptoms and complications of associated arrhythmias may be improved by medication, particularly with beta-blockers, which tend to stabilize the atrial rhythm and perhaps the ventricular rhythms. In treating patients with demonstrated ventricular arrhythmias, other antiarrhythmic agents may be helpful. (Table II summarizes the abnormalities, causes, and treatments of hypertrophic obstructive cardiomyopathy.) Epicardial coronary atherosclerosis is not rare in these patients, and arteriographic confirmation may lead to improvement by surgical bypass treatment. Since stroke volume is nearly fixed, cardiac output depends very much on heart rate. For this reason, each patient needs to receive the appropriate dosage of medications to achieve the optimal heart rate for his or her own physiologic state.