Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle (myocardium) becomes abnormally thick (hypertrophic). Thickened heart muscle can make it harder for the heart to pump blood. Hypertrophic cardiomyopathy often goes undiagnosed because many people with the disease have few, if any, symptoms and can lead normal lives without significant problems. However, in a small number of people with HCM, thickened heart muscle causes shortness of breath,...