What is hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a genetic disease that causes thickening (hypertrophy) of the heart muscle. The heart muscle cells enlarge more than they should, and scarring often develops between the cells.

The left and right ventricles are the 2 lower chambers of the heart. A muscular wall called the septum separates these 2 ventricles. With HCM, the walls of the ventricles and septum may thicken abnormally.

The thickened septum may bulge into the left ventricle and partially block the blood flow out to the body. This is called obstructive hypertrophic cardiomyopathy (HOCM). When this happens, the heart must work harder to get the blood out to the body.

Because of thickened heart muscle, the inside of the left ventricle is smaller, so it holds less blood than normal. The ventricle can also become very stiff. As a result, it's less able to relax and fill with blood.

HCM can also affect how the mitral valve works, which can increase pressure in the ventricles. This can cause fluid to build up in the lungs. The abnormal heart cells in HCM can also set off abnormal heart rhythms.

HCM is one of the more common genetic conditions that can affect the heart. In most cases, the symptoms first appear during adolescence or young adulthood.

What causes hypertrophic cardiomyopathy?

HCM is a genetic problem that you most often inherit from your parents. Or it can happen when a gene mutates. It leads to the thickening of the left ventricle. How exactly this happens is not yet clear.

HCM is autosomal dominant. This means you need an abnormal gene from only 1 of your parents to have it. But even if you have an abnormal gene, you might not develop HCM. Researchers are still trying to understand what other factors increase the chances of having the disease.

Who is at risk for hypertrophic cardiomyopathy?

Having a parent, brother, sister, or child (first-degree relative) with HCM puts you at risk for the disease. A parent with an abnormal gene for this condition has a 1-in-2 chance of giving that gene to a child. If someone in your immediate family has HCM, you should be screened for the condition. Screening typically includes a healthcare provider asking you about your past health and giving you a physical exam. You may also have an electrocardiogram and an echocardiogram. Genetic testing with a blood test can also be used for screening and diagnosis.

What are the symptoms of hypertrophic cardiomyopathy?

Most people with HCM have few or no symptoms at first. Symptoms most often start during adolescence or young adulthood. The onset and severity of symptoms varies among people with the condition. They may include:

• Shortness of breath with activity

• Shortness of breath when lying flat

• Chest pain, especially with activity

• Fainting or near fainting

• Unpleasant awareness of the heartbeat (palpitations)

• Tiredness (fatigue) or lack of energy

• Swelling in the legs and feet

• Abnormal heart rhythms

How is hypertrophic cardiomyopathy diagnosed?

Your healthcare provider will take your health history and do a physical exam, noting any heart murmurs. Several tests may also help in the diagnosis. These tests include:

• Electrocardiogram (ECG). This test is done to look for abnormalities in heart rhythm.

• Echocardiogram (echo). This test can confirm the diagnosis. An echo will provide more detailed information about the heart’s structure and function.

• Stress echo. This test involves exercising on a treadmill or stationary bike during an echo. This test looks at how the heart responds to stress.

• Continuous portable electrocardiogram monitoring. This is a portable ECG that can record abnormal heart rhythms throughout the day.

• Cardiovascular MRI. This imaging test uses magnets to make detailed images of the heart. It is one of the best tests to diagnose HCM.

• Other tests. These may include cardiac catheterization and coronary angiography (less common).

• Genetic testing. This includes collecting a blood sample.

If a person has HCM, other members of the family should be tested. This includes all the siblings, parents, and children of the person diagnosed with the disease.

How is hypertrophic cardiomyopathy treated?

Treatment for HCM aims to decrease symptoms and the chance of complications. The best treatment for you will depend on your specific symptoms. Some general types of treatment include:

• Activity limits. Talk with your healthcare provider about what kinds of exercise you can do. You may need to stop most competitive sports. You may also need to skip doing isometric exercises, such as weightlifting, and burst exercises, such as sprinting.

• Preventing dehydration. This includes maintaining a steady fluid balance.

• Medicines to treat shortness of breath and chest pain. Some examples include beta-blockers and calcium-channel blockers. These medicines help to relax the heart and decrease the heart’s need for oxygen. They will improve the heart’s ability to fill with blood and decrease the obstruction of blood flow to the body.

• Medicines to help prevent abnormal heart rhythms. These help change the electrical activity in the heart.

• Anticoagulants. These are also called blood thinners. They include medicines such as warfarin. These are used if you have certain abnormal heart rhythms. This reduces the risk for stroke.

• Septal myectomy. This is surgery to remove a portion of the septal wall so more blood can fill the ventricle and be pumped out to the body.

• Alcohol septal ablation. In this procedure, pure alcohol is injected into certain blood vessels to destroy the segment of muscle that is blocking blood flow out of the heart.

• Implantable cardioverter defibrillator (ICD). This implanted device monitors for dangerous heart rhythms and can restore normal rhythm with an energy shock. It's placed in people who are at a very high risk of a dangerous heart rhythm and cardiac arrest.

Septal myectomy and alcohol septal ablation may be done in people with severe symptoms or complications that don't improve with medicines. Both procedures help blood exit the left ventricle more easily.

What are possible complications of hypertrophic cardiomyopathy?

Most people with HCM don't have complications. But some do, especially if their disease is more severe. These complications may include:

• Heart failure

• Stroke

• Abnormal heart rhythms

• Infection of the heart valves (endocarditis)

• Increased risk of complications during pregnancy

• Sudden cardiac death (from a dangerous heart rhythm)

Sudden death is rare in people with HCM. If you are at risk for sudden death, your healthcare provider may advise an ICD.

How do I manage hypertrophic cardiomyopathy?

Your healthcare provider may give you additional instructions about how to manage your HCM.

• You may need to stay away from certain medicines that can make your HCM worse. These include medicines for erectile dysfunction.

• You should work closely with your healthcare provider if you are planning to get pregnant.

• Your provider may want to treat you for other heart conditions. This might include medicines for high cholesterol.

• Your provider might advise other lifestyle changes, like losing weight, quitting smoking, reducing stress, or improving your diet.

• You may need to reduce your intake of alcohol or caffeine. These increase the risk of abnormal heart rhythms.