Hypertrophic cardiomyopathy (HCM) is one of the most common genetic heart diseases. It is inherited in an autosomal dominant pattern and exhibits variable penetrance and expression. Its prevalence was initially thought to be 1:500 but could be as high as 1:200.

Hypertrophic cardiomyopathy is caused by an abnormality of heart muscle, usually caused by a genetic mutation of a sarcomeric protein, that results in disrupted myocardial alignment known as myocardial disarray. The result is regional hypertrophy with variable involvement of myocardium. Hypertrophy of the basal septum, adjacent to the left ventricular outflow tract (LVOT), may result in outflow obstruction.

Presenting symptoms are variable, and many patients remain asymptomatic for decades. When symptoms develop, they are often associated with LVOT obstruction and may include dyspnea, palpitations, syncope, or sudden cardiac death. HCM can be diagnosed at any stage of life. It is the most common cause of sudden cardiac death in young athletes.