What is hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy is a genetic disease in which the heart muscle thickens abnormally. The thickened heart muscle can interfere with the heart's electrical system, increasing the risk for life-threatening abnormal heartbeats (arrhythmias) and, rarely, sudden death. In some cases, the enlarged heart muscle is unable to relax between heartbeats as it normally does, and the heart muscle itself does not get enough blood or oxygen. In rare cases, the thickened heart muscle reduces the heart's ability to pump blood effectively to the body.

See an illustration of a normal heart compared with a heart with hypertrophic cardiomyopathy.

What causes hypertrophic cardiomyopathy?

Researchers have identified defective genes that cause the heart muscle fibers to grow abnormally, resulting in hypertrophic cardiomyopathy. People with family members who have had hypertrophic cardiomyopathy are at an increased risk for developing this condition and, as a result, have a slightly higher risk of early death than the general population.

In about 50% of cases, people inherit hypertrophic cardiomyopathy from their parents. In most of the remaining cases, fetuses probably develop a gene mutation during the early stages of development before birth. This mutation causes abnormal growth of heart tissue.¹

What are the symptoms?

Even though hypertrophic cardiomyopathy can cause serious health problems and even sudden death, you may never have any symptoms of the disease. Many people with the disease live normal lives with very few problems. These people may never even be treated for hypertrophic cardiomyopathy.

Symptoms of hypertrophic cardiomyopathy may occur at any time of life. You may have had hypertrophic cardiomyopathy for a long time, but just recently started having symptoms. The most common symptoms are shortness of breath, chest pain (angina), heart palpitations, and fainting or near-fainting (syncope), especially with physical activity. Sometimes life-threatening abnormal heartbeats (arrhythmias) cause fainting and heart palpitations-these are symptoms that you should always report to your doctor because of your increased risk of sudden death.

In rare cases, the thickened heart muscle becomes unable to pump enough blood to meet the body's needs. This is called heart failure. Symptoms of heart failure include fluid buildup (edema), especially in the legs, ankles, and feet; shortness of breath and a dry, hacking cough, especially while lying down; increased urination at night; nausea; and abdominal swelling, tenderness, or pain.

How is hypertrophic cardiomyopathy diagnosed?

Your doctor will review your medical history, ask about any family history of heart disease or early and sudden death, and perform a thorough physical exam, including listening to your heart and lungs and checking your legs for fluid buildup. An electrocardiogram (ECG or EKG), chest X-ray, echocardiogram, routine blood tests, and other medical tests are usually needed to confirm a diagnosis.