Hypertrophic Cardiomyopathy.

The degree of clinical expression of both obstructive and nonobstructive hypertrophic cardiomyopathy (HCM) is widely variable. Many patients with HCM are asymptomatic or minimally symptomatic. Most patients with mild or moderate HCM respond well to medical therapy, but medical therapy in patients with severe disease is only marginally beneficial. In some instances, medical therapy can even complicate management by producing significant conduction disturbances. Most symptomatic patients with a significant resting outflow tract gradient may respond to atrioventricular sequential electronic pacing. Most of these patients eventually become symptomatic again, however, because of progression of the disease process or other unknown factors. The outcome of myotomy-myectomy depends greatly on the surgeon's experience with this surgical procedure. In patients with very severe hypertrophy or evidence of left ventricular dilatation and systolic dysfunction, cardiac transplantation should be considered earlier than it would be on the basis of symptoms, functional capacity, and other factors.