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Hypertrophic Cardiomyopathy
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Hypertrophic Cardiomyopathy
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Hypertrophic cardiomyopathy (HCM) is an inherited disease that directly affects the heart muscle. Because of several high-profile cases of young athletes dying suddenly of HCM, people think it is a disease that affects only athletes. But this disease can make anyone sick—men, women, and children of all ages—no matter how physically fit he or she is.

HCM is the second most common form of cardiomyopathy. If you have HCM, it means that the walls of your heart are thicker than they should be. Some thickening is normal for healthy people who exercise or who play competitive sports. But with HCM, the thickening becomes extreme.

In time, the thickening of the heart muscle can cause the heart to get bigger, or enlarge. This is called cardiomegaly. Doctors can usually tell if cardiomegaly is present by measuring the size of the heart. Cardiomegaly is present if the diameter of the heart is more than 50% of the inner diameter of the ribcage (the cardiothoracic ratio).

In most patients with HCM, the septum, which separates the left and right sides of the heart, bulges into the lower left chamber of the heart (the left ventricle). The muscles in both of the lower chambers often become larger. These thickened muscle walls may partly block the flow of blood through the aortic valve or prevent the heart from relaxing between beats and filling with blood. In a small number of HCM patients, the mitral valve, which separates the upper left chamber (left atrium) and lower left chamber (left ventricle), may also be damaged. Or the mitral valve may stick to the septum, which blocks the blood flow through the valve.

What are the symptoms?

Fainting during strenuous exercise is often the first and most dramatic symptom of this condition. If you have other symptoms, you may feel short of breath, tired, and have chest pain. People who notice these warning signs should see a doctor right away.

Young athletic adults who die of HCM usually do so without knowing they have the condition. HCM is also harder to diagnose in athletes because it is similar to a harmless condition called left ventricular hypertrophy, where the left ventricle of the heart gets larger because of physical conditioning. Anyone—young or old—who wants to take part in very active athletic competition should see a doctor and have a thorough physical exam that includes an electrocardiogram (ECG or EKG) and chest x-ray.

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What causes HCM?

Researchers think that this form of cardiomyopathy is passed down through family members. In more than half of the cases, people affected by hypertrophic cardiomyopathy have close relatives who also have enlarged septums.

Luckily, there is a test that can determine who may be at risk for HCM. Using the results of this test, doctors can warn children at risk about exercising too hard and taking part in certain competitive sports.

Other cases of HCM have been traced to high blood pressure and heart valve disease.

How is HCM diagnosed?

  • A chest x-ray can show if your heart is enlarged.
  • An electrocardiogram (ECG or EKG) can indicate if the chambers of your heart are hypertrophied or enlarged.
  • Echocardiography can be used to show the size of your heart and how much muscle damage there is.
  • Angiography, a cardiac catheterization procedure, can give a detailed view of how well your heart's arteries, chambers, and valves are working.
  • Radionuclide studies can give information on how well the heart is pumping blood.
  • Genetic testing may play an important role in helping doctors rule out other diagnoses—for example, patients who have a small increase in wall thickness (like trained athletes with ventricular hypertrophy) and some patients with constant high blood pressure who are thought to have HCM.

How is HCM treated?

Often the treatments for this condition are used to ease the symptoms rather than treat the condition itself. Treatments include lifestyle changes, medicines, and surgery.

Lifestyle changes

Patients with serious HCM must stay less physically active. Children and young adults who have had the gene testing and are thought to be at risk for HCM should avoid exercising too much and avoid taking part in certain types of athletic competition.


For patients with mild to moderate symptoms, medicines are often the treatment of choice.

Medicines do not work in all cases, especially in patients with more severe symptoms. Medicines can also have side effects that may include fluid in the lungs and low blood pressure. In some cases, certain medicines may cause sudden death.


Doctors may suggest surgery for HCM patients with severe heart damage.

  • Surgeons may remove part of the thickened septum (the muscle wall separating the chambers) that is blocking the blood flow. This procedure, called the Morrow operation, eases symptoms in about 70% of patients.
  • In patients who have mitral valve damage or where the septum wall is too thin for safe removal of tissue, surgeons may replace the mitral valve.

Non-Surgical Treatment

Alcohol ablation is a non-surgical treatment that involves injecting alcohol down a small branch of one of the heart's arteries and into the extra heart muscle. The alcohol destroys the extra heart muscle without having to cut it out surgically.

Alcohol ablation is performed in the cardiac catheterization laboratory (cath lab). Doctors will first perform a cardiac catheterization to find the coronary artery that supplies the thickened area of heart muscle. A special dye is injected through a catheter to locate the exact area of thickened muscle. When the area is located, doctors then inject tiny amounts of pure alcohol (ethanol) through the catheter. The alcohol destroys the area of extra heart muscle, causing a "controlled" heart attack. Over the next few months, the thickened muscle shrinks to a more normal size, allowing more blood to flow through the heart.

Sometimes, when the alcohol destroys the heart muscle, it also injures the heart's electrical system (which regulates the heartbeat). Doctors will insert a temporary pacemaker to help regulate your heartbeat after the procedure. If you do not have any heart-rhythm problems, this pacemaker is removed after 24 hours. Patients who continue to have heart-rhythm problems will need to have a permanent pacemaker inserted.

You can expect to stay in the hospital for 3 to 5 days after the procedure.

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Hypertrophic cardiomyopathy

Updated July 2015

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