Hypertrophic cardiomyopathy (HCM) is a condition in which the heart muscle becomes thick. The thickening makes it harder for blood to leave the heart, forcing the heart to work harder to pump blood.

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.

Younger people are likely to have a more severe form of hypertrophic cardiomyopathy. However, the condition is seen in people of all ages.

• Chest pain
• Dizziness
• Fainting, especially during exercise
• Heart failure (in some patients)
• High blood pressure (hypertension)
• Light-headedness, especially after activity or exercise
• Sensation of feeling the heart beat (palpitations)
• Shortness of breath

Other symptoms that may occur are:

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

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

The first symptom of hypertrophic cardiomyopathy among many young patients is sudden collapse and possible death. This is caused by very 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. These sounds may change with different body positions.

The pulse in your arms and neck will also be checked. The doctor may feel an abnormal heartbeat in the chest.

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

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

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).

If you have symptoms, you may need medication 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. Medications will often relieve symptoms so patients do not need more invasive treatments.

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

Some patients may have a permanent pacemaker placed. However, pacemakers are used less often today than they were in the past.

When blood flow out of the heart is severely blocked, an operation called surgical 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.

In some cases, patients may be given an injection of alcohol into the arteries that feed the thickened part of the heart (alcohol septal ablation).

An implantable-cardioverter defibrillator (ICD) may be needed to prevent sudden death. ICDs are used in high-risk patients. High risks include:

• Drop in blood pressure during exercise
• Family history of cardiac arrest
• History of cardiac arrest or ventricular tachycardia
• History of unexplained fainting
• Life-threatening heart rhythms on a Holter monitor
• Severe heart muscle thickness

Some people with hypertrophic cardiomyopathy may not have symptoms and live a normal lifespan. Others may get worse over time or rapidly. The condition may develop into dilated cardiomyopathy in some patients.

People 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, always follow your doctor's advice concerning exercise and medical appointments. Avoid strenuous exercise.

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

Call for an appointment with your health care provider if:

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

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. Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. St. Louis, Mo: WB Saunders; 2007: chap 65.