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What is hypertrophic cardiomyopathy?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Hypertrophic cardiomyopathy (HCM or HCOM) is a disease that affects a person's heart muscle, making the muscle more thick and rigid than it should be. This can decrease the heart's ability to pump sufficient blood to the body and can alter the heart's normal rhythm. HCM is the number one cause of sudden cardiac death in people younger than 30. Luckily, most people with HCM experience no significant complications from the disease.

Abdul J. Tajik, MD
Cardiology (Cardiovascular Disease)
Hypertrophic cardiomyopathy (HCM) is a unique disorder that causes an abnormal increased thickness of the heart muscle. The disease presents itself in many different ways and, over the years, it has been given more than 75 different names. Despite the thickening of the muscle, the heart is often able to pump blood to the rest of the body quite well. Therefore, many people with hypertrophic cardiomyopathy are relatively asymptomatic (have no symptoms).
Hypertrophic cardiomyopathy (HCM), which is typically inherited from a parent, is a disease in which the muscle of the lower left chamber of the heart (the left ventricle) becomes abnormally thick and enlarged. This thickening typically affects some parts of the ventricle walls more than others (doctors call this “asymmetric thickening”). The most commonly affected area is the wall between the two bottom chambers known as the septum
HCM is a significant cause of both heart failure (for example, shortness of breath or fatigue) and sudden death. It is the most common cause of sudden cardiac death among athletes who were believed to be healthy.
Hypertrophic cardiomyopathy, in contrast to the congestive type, involves an enlargement or overgrowth of the heart muscle, usually that of the left ventricle, but sometimes the right chamber is also involved. In one form of hypertrophic disease, the septum (the wall between the two ventricles) becomes enlarged and obstructs the flow of blood from the left ventricle into the aorta. The mitral valve also may be distorted by the thickened septum, leading to mitral insufficiency. The major symptoms are shortness of breath, dizziness or fainting, chest pain, and cardiac arrhythmias.

About 1 in 500 people have hypertrophic cardiomyopathy, a thickening of the muscle on the left side of the heart. Watch this video with thoracic surgeon Dr. Hiroo Takayama to learn about typical symptoms – and why certain high-risk patients may be asymptomatic. 


Hypertrophic cardiomyopathy is an inherited heart defect that is a common cause of sudden cardiac death in young people. The condition, which affects an estimated one in 500 people, causes the muscle mass of the left ventricle to thicken abnormally, forcing the heart to work harder to pump blood.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.