Hypertrophic cardiomyopathy is a genetic disease in which the heart muscle grows abnormally, making the heart muscle thicken. The thickened heart muscle can interfere with the heart's electrical system, which increases the risk for life-threatening abnormal heartbeats (arrhythmias) and, rarely, sudden death.
Symptoms, such as shortness of breath and chest pain, may occur at any time of life. But some people never have symptoms, even though the condition may have been present for some time. In some cases, the thickened heart muscle is unable to relax between heartbeats, and the heart muscle itself does not get enough blood or oxygen, which causes chest pain. In rare cases, the thickened heart muscle becomes unable to pump enough blood to meet the body's needs, resulting in heart failure.
WebMD Medical Reference from Healthwise