Hypertrophic cardiomyopathy (HCM) is a form of cardiomyopathy, a condition in which the heart muscle to become thick. The thickening makes it harder for the heart to work.

Hypertrophic cardiomyopathy is often asymmetrical, meaning one part of the heart is thicker than the other parts. The condition is usually passed down through families (inherited). It is believed to be a result of several problems (defects) with the genes that control heart muscle growth.

Because hypertrophic cardiomyopathy causes the size of one of the heart chambers (ventricular chamber) to shrink, the heart must work harder to pump blood. The thickening of the heart muscle may complete block the normal flow of blood out of the heart. It may also make it harder for the heart valves to work. Heart valves help control the direction of blood flow.

Younger people are likely to have a more severe form of hypertrophic cardiomyopathy. However, the condition is seen in people of all ages. In people over age 60, hypertrophic cardiomyopathy is often associated with mild hypertension (high blood pressure).

• Chest pain
• Fainting, especially during exercise
• Light-headedness, especially after activity or exercise
• Dizziness
• Sensation of feeling heart beat (palpitations)
• Shortness of breath

Additional symptoms that may occur are:

• Fatigue, reduced activity tolerance
• Shortness of breath when lying down

Some patients have no symptoms, and may not even realize they have the condition until it is found during a routine medical exam.

Unfortunately, the first symptom of hypertrophic cardiomyopathy among many young patients is sudden death, caused by severely abnormal heart rhythms (arrhythmias). Hypertrophic cardiomyopathy is a major cause of death in young athletes who seem completely healthy but die during heavy exercise.

The health care provider will perform a physical exam and listen to the heart and lungs with a stethoscope. Listening with a stethoscope may reveal abnormal heart sounds or a murmur, which may change intensity with different body positions. The pulse in your arms and neck will be checked. The doctor may feel an abnormal heart beat in the chest.

Most frequently, however, nothing is found during a physical exam, and the exam is considered normal.

Tests used to diagnose heart muscle thickness, problems with blood flow, or leaky heart valves ( mitral valve regurgitation ) may include:

• Echocardiography (the most common test) with Doppler ultrasound
• Transesophageal echocardiogram (TEE)
• Chest x-ray
• ECG
• 24-hour Holter monitor (heart monitor)
• Cardiac catheterization

Blood tests may be done to rule out other possible diseases.

If you are diagnosed with hypertrophic cardiomyopathy, your health care provider may recommend that your close blood relatives (family members) be screened for the condition.

The goal of treatment is to control symptoms and prevent complications. Some patients may need to stay in the hospital until the condition is under control (stabilized).

Medicines may be needed to help the heart contract and relax correctly. Drugs include beta-blockers and calcium channel blockers. These medicines reduce chest pain and pain during exercise.

When blood flow out of the heart is severely blocked, an operation called myotomy-myectomy is done. This procedure cuts and removes the thickened part of the heart. Patients who have this procedure often show significant improvement.

If the heart's mitral valve is leaking, surgery may be done to repair or replace the valve.

Some people with arrhythmias may need anti-arrhythmic medications. If the arrhythmia is atrial fibrillation, blood thinners will also be used to reduce the risk of blood clots.

In some cases, a patient may be given an injection of alcohol into the arteries that feed the thickened part of the heart. This procedure is called alcohol septal ablation. It helps decrease the blockage and helps blood flow out of the heart.

An implantable-cardioverter defibrillator (ICD) may be needed to prevent sudden death. ICDs are used in high-risk patients. High risks include severe heart muscle thickness, life-threatening heart rhythms, a history of fainting, or a family history of sudden cardiac death.

Some persons with hypertrophic cardiomyopathy may not have symptoms and live a normal life span. Others may get worse gradually or rapidly. The condition may develop into dilated cardiomyopathy in some patients.

Persons with hypertrophic cardiomyopathy are at higher risk for sudden death than the normal population. Sudden death can occur at a young age.

Hypertrophic cardiomyopathy is a well-known cause of sudden death in athletes. Almost half of deaths in hypertrophic cardiomyopathy happen during or just after the patient has done some type of physical activity.

If you have hypertrophic cardiomyopathy, you should always follow your doctor's advice concerning exercise and medical appointments. Strenuous exercise should be avoided.

• Severe injury from fainting
• Life-threatening heart rhythm problems (arrhythmias)
• Congestive heart failure
• Dilated cardiomyopathy

Call for an appointment with your health care provider if:

• You have any symptoms of hypertrophic cardiomyopathy
• Chest pain, palpitations, faintness or other new or unexplained symptoms develop

If you are diagnosed with hypertrophic cardiomyopathy, your health care provider may recommend that your close blood relatives (family members) be screened for the condition.

Some patients with mild forms of hypertrophic cardiomyopathy are only diagnosed by screening echocardiograms because of their known family history.

If you have high blood pressure, make sure you take your medication and follow your doctor's recommendations.

Maron BJ. Hypertrophic cardiomyopathy in childhood. Pediatr Clin North Am. 2004; 51(5): 1305-46.

Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed. St. Louis, Mo; WB Saunders; 2005:1659-1692.