Hypertrophic cardiomyopathy (HCM) is a disease in which the myocardium (heart muscle) is hypertrophic (thickened) without any obvious cause, creating functional impairment of the heart. It is the leading cause of sudden cardiac death in young athletes. The occurrence of hypertrophic cardiomyopathy is a significant cause of sudden cardiac death in any age group and a cause of disabling cardiac symptoms. HCM is frequently asymptomatic until sudden cardiac death, and for this reason some suggest routinely screening certain populations for this disease. In most patients, HCM is associated with little or no disability and normal life expectancy. Diagnosis is usually by echocardiogram. While there is no known prevention or cure, symptomatic patients may be treated effectively by medication, a catheter procedure or by surgery. With HCM, the myocytes (cardiac contractile cells) in the heart increase in size, which results in the thickening of the heart muscle. In addition, the normal alignment of muscle cells is disrupted, a phenomenon which is known as myocardial disarray.