Hypertrophic Cardiomyopathy


Hypertrophic Cardiomyopathy (HCM) is a disease that affects the heart muscle, causing the muscle to enlarge, or "hypertrophy."

At Cleveland Clinic's Miller Family Heart, Vascular & Thoracic Institute, we have a special interest in treating Hypertrophic Cardiomyopathy (HCM). Since 1978, we have treated hundreds of patients and the numbers are increasing each year.

What is hypertrophic cardiomyopathy (HCM)?

Hypertrophic cardiomyopathy (HCM) is a complex type of heart disease that affects the heart muscle. It causes thickening of the heart muscle (especially the ventricles, or lower heart chambers), left ventricular stiffness, mitral valve changes and cellular changes.

Thickening of the heart muscle (myocardium) occurs most commonly at the septum. The septum is the muscular wall that separates the left and right side of the heart. Problems occur when the septum between the heart’s lower chambers, or ventricles, is thickened. The thickened septum may cause a narrowing that can block or reduce the blood flow from the left ventricle to the aorta - a condition called “outflow tract obstruction.” The ventricles must pump harder to overcome the narrowing or blockage. This type of hypertrophic cardiomyopathy may be called hypertrophic obstructive cardiomyopathy (HOCM).

HCM also may cause thickening in other parts of the heart muscle, such as the bottom of the heart called the apex, right ventricle, or throughout the entire left ventricle.

Anatomy of the heart

Normal Heart

Stiffness in the left ventricle occurs as a result of cellular changes that occur in the heart muscle when it thickens. The left ventricle is unable to relax normally and fill with blood. Since there is less blood at the end of filling, there is less oxygen-rich blood pumped to the organs and muscles. The stiffness in the left ventricle causes pressure to increase inside the heart and may lead to the symptoms described below.

Mitral valve changes: The narrowing of the left ventricular outflow tract disrupts the proper function of the mitral valve, resulting in outflow obstruction and increased pressure in the left ventricle.

The obstruction is the result of the mitral valve striking the septum. When this occurs, the mitral valve frequently leaks, causing the blood to go back into the left atrium.

Cellular changes, or changes in the cells of the heart muscle, occur with HCM. Through a microscope, the cells appear disorganized and irregular (called “disarray”) instead of being organized and parallel. This disarray may cause changes in the electrical signals traveling through the lower chambers of the heart and lead to ventricular arrhythmia (a type of abnormal heart rhythm).

Disorganized cell pattern

Disorganized Pattern

Normal Cell Pattern

Normal Cell Pattern

Who is affected by hypertrophic cardiomyopathy (HCM)?

Hypertrophic cardiomyopathy affects an estimated 600,000 to 1.5 million Americans, or one in 500 people. It is more prevalent than multiple sclerosis, which affects one in 700 people.

Symptoms and Causes

What causes hypertrophic cardiomyopathy (HCM)?

  • HCM can be inherited, caused by an abnormality in a gene that codes the characteristics for the heart muscle. There are many genes that can cause HCM. When a gene defect is present, the type of HCM that develops varies greatly within the family. In addition, some people who have the HCM gene may never develop the disease.
  • Hypertrophy may be acquired as a result of high blood pressure or aging.
  • In other instances, the cause of hypertrophy and HCM is unknown.

Because the cause of HCM varies, it is frequently difficult to identify a high-risk population.

What are the conditions associated with hypertrophic cardiomyopathy (HCM)?

Many people with HCM live a normal life and do not experience health-related problems.

Other people with HCM may develop heart conditions that shorten life or decrease the person’s quality of life, including:

  • Sudden cardiac arrest and sudden cardiac death: Sudden cardiac arrest is a sudden loss of heart function caused by a dangerously fast heart rhythm called ventricular tachycardia. Unless emergency treatments, including CPR and defibrillation, are initiated immediately after the onset of symptoms, sudden cardiac death can occur.

Most people with HCM have a low risk for sudden cardiac death. However, HCM is the most common cause of sudden cardiac death in people under age 30. HCM may be best known for its role in cardiac arrest and subsequent death in some young professional athletes.

  • Heart failure: A condition in which the heart’s pumping power is weaker than normal.

Associated Symptoms

Symptoms associated with the presence of ventricular tachycardia or heart failure include:

  • Chest pain or pressure that usually occurs with exercise or physical activity, but also may occur with rest or after meals.
  • Shortness of breath and fatigue, especially with exertion. These symptoms are more common in adults with hypertrophic cardiomyopathy and are most likely caused by a backup of pressure in the left atrium and lungs.
  • Syncope (fainting or passing out) may affect HCM patients. Syncope with HCM may be caused by irregular heart rhythms, abnormal responses of the blood vessels during exercise, or no cause may be found.
  • Palpitations (fluttering in the chest) due to abnormal heart rhythms (arrhythmias) such as atrial fibrillation or ventricular tachycardia. Atrial fibrillation occurs in about 25 percent of those with HCM, and increases the risk for blood clots and heart failure.

Diagnosis and Tests

How is hypertrophic cardiomyopathy (HCM) diagnosed?

The diagnosis of HCM is based on:

  • Medical history: Your doctor will ask you questions about your symptoms and family history.
  • Physical exam: Your doctor will listen to your heart and lungs. Patients with hypertrophic obstructive cardiomyopathy (HOCM) may have a heart murmur.
  • Tests: An echocardiogram is the most common test used to diagnose HCM, as the characteristic thickening of the heart walls is usually visible on the echo. Other tests may include blood tests, electrocardiogram, chest X-ray, exercise stress echo test, cardiac catheterization and magnetic resonance imaging (MRI).

Management and Treatment

The type of HCM treatment prescribed depends on:

  • Whether there is narrowing in the outflow tract (the path blood travels to leave the heart)
  • How the heart is functioning
  • The patient’s symptoms
  • The age and activity level of the patient
  • The presence of arrhythmias

Treatment is aimed at minimizing or preventing symptoms and reducing the risk of complications, such as heart failure and sudden cardiac death.

Treatment includes risk identification and regular follow-up, lifestyle changes, medications and procedures, as needed.

Screening and Risk Identification


Hypertrophic Cardiomyopathy (HCM) is a medical condition that may be passed on from generation to generation. It is important for you or your family members to have screening if you have a first-degree relative with the condition. First-degree relatives are your parents, siblings and children.

The first step is to have an electrocardiogram (ECG) and echocardiogram (echo) to check your heart.

If the test results show signs of Hypertrophic Cardiomyopathy, you will need to see a cardiologist who specializes in HCM. For a list of Cleveland Clinic doctors who treat patients with this condition, visit our Hypertrophic Cardiomyopathy Center.

If your test results are normal, we suggest a follow up echo and EKG every three years until you are 30 years old, and then every 5 years thereafter.

Risk For Sudden Cardiac Death

Most people with HCM have a low risk for sudden cardiac death. However, it is important to identify the small number of patients with HCM who do have a higher risk for sudden cardiac death, so preventive measures can be taken.

People with HCM who have a higher risk for sudden cardiac death include:

  • Patients who have a family history of sudden cardiac death
  • Young patients who have had several episodes of syncope (fainting)
  • Patients who experience an abnormal blood pressure response with exercise
  • Patients who have a history of arrhythmia with a fast heart rate
  • Patients with severe symptoms and poor heart function

Your doctor can discuss your personal risk. If you have two or more risk factors for sudden death, your doctor may prescribe preventive treatments such as antiarrhythmic medications or an implantable cardioverter defibrillator (ICD) to reduce your risk.


Medications are often prescribed to treat symptoms and prevent further complications. Medications such as beta-blockers and calcium channel blockers relax the heart muscle, allowing it to fill better and pump more effectively. Other medications may be prescribed as needed to control your heart rate or decrease the occurrence of arrhythmias.

You may be told to avoid certain medications, such as nitrates, because they lower blood pressure, or digoxin, because it increases the force of the heart’s contraction.

Antibiotic medications may be prescribed to reduce the risk of bacterial endocarditis, a potentially life-threatening condition (see other precautions listed on the next page).


Procedures for the treatment of hypertrophic obstructive cardiomyopathy include septal myectomy, ethanol ablation, implantable cardioverter defibrillator (ICD) and heart failure management, as needed.

Septal Myectomy

Septal Myectomy

During a septal myectomy, a surgical procedure, the surgeon removes a small amount of the thickened septal wall to widen the outflow tract (the path the blood takes) from the left ventricle to the aorta. Myectomy is considered when medications are not effective in treating HCM. This frequently eliminates the mitral valve regurgitation.

Ethanol Ablation

This procedure, also called septal ablation, is reserved for patients who are not eligible candidates for septal myectomy. The ablation procedure is performed in the cardiac catheterization laboratory.

First, the small coronary artery that supplies blood flow to the upper part of the septum is located during a cardiac catheterization procedure. A balloon catheter is inserted into the artery and inflated. A contrast agent is injected to locate the thickened septal wall that narrows the passageway from the left ventricle to the aorta.

When the bulge is located, a tiny amount of pure alcohol is injected through the catheter. The alcohol kills the cells on contact, causing the septum to shrink back to a more normal size over the following months, widening the passage for blood flow.

Implantable Cardioverter Defibrillator placement

Implantable Cardioverter Defibrillators (ICD)

ICDs are suggested for people at risk for life-threatening arrhythmias or sudden cardiac death. The ICD is a small device placed just under the skin and is connected to wire leads that are threaded through the vein to the heart. An ICD constantly monitors the heart rhythm. When it detects a very fast, abnormal heart rhythm, it delivers energy (a small but powerful shock) to the heart muscle to cause the heart to beat in a normal rhythm again. Your doctor will tell you if an ICD is recommended.

Lifestyle Changes

Certain lifestyle changes, as listed below, are essential for properly managing HCM.

  • Fluid and sodium restrictions may be necessary for some patients if heart failure symptoms are present. Ask your doctor for specific fluid and dietary guidelines, including information about alcoholic beverages and caffeinated products.
  • Exercise. Your doctor will discuss exercise guidelines with you. Most people with hypertrophic cardiomyopathy are able to participate in noncompetitive aerobic activities. Heavy weight lifting and many high-intensity sports are not recommended.
  • Regular Follow-Up Visits. Patients with HCM should follow up regularly with their cardiologist, as recommended, to monitor their condition.
  • Reducing the Risk of Infection. See below about precautions to take if you are at risk of developing infective endocarditis.

Infective Endocarditis Precautions

If you have HCM, you have an increased risk of developing bacterial or infective endocarditis.

Bacterial or infective endocarditis is an infection of the heart valves or the heart’s inner lining (endocardium). It occurs when germs (especially bacteria, but occasionally fungi and other microbes) enter the blood stream and attack the lining of the heart or the heart valves. Bacterial endocarditis causes growths or holes on the valves or scarring of the valve tissue, most often resulting in a leaky heart valve. Without treatment, bacterial endocarditis can be a fatal disease.

To Reduce Your Risk

  • Practice good oral hygiene habits every day. Take good care of your teeth and gums by seeking professional dental care every six months, regularly brushing and flossing your teeth, and making sure dentures fit properly.
  • Call your doctor if you have symptoms of an infection, including a fever over 100 degrees F; sweats or chills; skin rash; pain, tenderness, redness or swelling; wound or cut that won’t heal; red, warm or draining wound; sore throat, scratchy throat or pain when swallowing; sinus drainage, nasal congestion, headaches or tenderness along upper cheekbones; persistent dry or moist cough that lasts more than two days; white patches in your mouth or on your tongue; nausea, vomiting or diarrhea.
  • Don’t wait to seek treatment. Colds and the flu do not cause endocarditis, but infections, which may have the same symptoms, do cause endocarditis. To be safe, call your doctor.
  • Cleveland Clinic cardiologists believe it is important for patients with HCM to take preventive antibiotics before certain medical and dental procedures, in addition to following the steps above to reduce your risk. Please talk to your doctor about the type and amount of antibiotics you should take, and for what procedures you should take them.
  • A bacterial endocarditis identification card is available from the American Heart Association and should be carried with you. Ask your doctor for a card or go to www.americanheart.org and search for “bacterial endocarditis wallet card.”


How do I find a doctor if I have hypertrophic cardiomyopathy?

To find a doctor, make an appointment, or to learn more about treatment of Hypertrophic Cardiomyopathy at Cleveland Clinic, see the Hypertrophic Cardiomyopathy Center.

For Pediatrics, visit The Center for Pediatric and Congenital Heart Diseases web site.

The Hypertrophic Cardiomyopathy Association (HCMA)

The Hypertrophic Cardiomyopathy Association (HCMA) is dedicated to support and educate those with HCM, their families and other health care professionals. They may be contacted at:

P.O. Box 306,
Hibernia, NJ 07842

Phone: 973.983.7429
Email: [email protected]

Additional Resources

Hypertrophic Cardiomyopathy: For Patients, Their Families and Interested Physicians

A very helpful guide for those with hypertrophic cardiomyopathy. Books can be ordered at www.4hcm.org

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Reviewed by a Cleveland Clinic medical professional.

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