Hypertrophic Cardiomyopathy

What is hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy is a genetic disease in which the heart muscle thickens abnormally. The thickened heart muscle can interfere with the heart's electrical system, increasing the risk for life-threatening abnormal heartbeats (arrhythmias) and, rarely, sudden death. In some cases, the enlarged heart muscle is unable to relax between heartbeats as it normally does, and the heart muscle itself does not get enough blood or oxygen. In rare cases, the thickened heart muscle reduces the heart's ability to pump blood effectively to the body.

See an illustration of a normal heart compared with a heart with hypertrophic cardiomyopathy.

What causes hypertrophic cardiomyopathy?

Researchers have identified defective genes that cause the heart muscle fibers to grow abnormally, resulting in hypertrophic cardiomyopathy. People with family members who have had hypertrophic cardiomyopathy are at an increased risk for developing this condition and, as a result, have a slightly higher risk of early death than the general population.

In about 50% of cases, people inherit hypertrophic cardiomyopathy from their parents. In most of the remaining cases, fetuses probably develop a gene mutation during the early stages of development before birth. This mutation causes abnormal growth of heart tissue.¹

What are the symptoms?

Even though hypertrophic cardiomyopathy can cause serious health problems and even sudden death, you may never have any symptoms of the disease. Many people with the disease live normal lives with very few problems. These people may never even be treated for hypertrophic cardiomyopathy.

Symptoms of hypertrophic cardiomyopathy may occur at any time of life. You may have had hypertrophic cardiomyopathy for a long time, but just recently started having symptoms. The most common symptoms are shortness of breath, chest pain (angina), heart palpitations, and fainting or near-fainting (syncope), especially with physical activity. Sometimes life-threatening abnormal heartbeats (arrhythmias) cause fainting and heart palpitations—these are symptoms that you should always report to your doctor because of your increased risk of sudden death.

In rare cases, the thickened heart muscle becomes unable to pump enough blood to meet the body's needs. This is called heart failure. Symptoms of heart failure include fluid buildup (edema), especially in the legs, ankles, and feet; shortness of breath and a dry, hacking cough, especially while lying down; increased urination at night; nausea; and abdominal swelling, tenderness, or pain.

How is hypertrophic cardiomyopathy diagnosed?

Your doctor will review your medical history, ask about any family history of heart disease or early and sudden death, and perform a thorough physical exam, including listening to your heart and lungs and checking your legs for fluid buildup. An electrocardiogram (ECG or EKG), chest X-ray, echocardiogram, routine blood tests, and other medical tests are usually needed to confirm a diagnosis.

If someone in your immediate family, such as a parent or sibling, has hypertrophic cardiomyopathy or died suddenly at a young age, you are at risk and should have routine echocardiograms and other medical tests to screen for the condition.² So far, routine genetic testing is not yet practical because there are so many possible abnormal genes that cause the disease.

How is it treated?

Many people with hypertrophic cardiomyopathy do not need treatment. But in some cases, having a thickened heart muscle can cause problems.

About one in four people with hypertrophic cardiomyopathy develop atrial fibrillation, an irregular and rapid heart rhythm.² Atrial fibrillation is usually treated with electrical cardioversion, which is an electrical shock to return the heart to its normal rhythm, and/or medicines to control the heart rate and rhythm. Doctors also often recommend anticoagulant medicines to slow blood clotting and prevent stroke in these people.

An estimated 5% to 10% of people with hypertrophic cardiomyopathy develop heart failure and progressive symptoms.¹ In these people, heart failure is treated with medicines to improve heart function. If heart failure becomes severe and does not improve with medicines, surgery to remove or reduce overgrown heart muscle may be recommended.

All people with hypertrophic cardiomyopathy—whether their symptoms are mild or severe—are at a higher risk for sudden death than the normal population and can die at a young age. While studies indicate that hypertrophic cardiomyopathy causes fewer deaths (1% per year of adults with hypertrophic cardiomyopathy) than once thought,³ most people with hypertrophic cardiomyopathy should be assessed by a cardiologist to determine their risk. For those in a high-risk category, an implantable cardioverter-defibrillator (ICD) appears to be the best way to prevent sudden death. An ICD is a small device like a pacemaker, used mainly to control life-threatening heart rhythms.

How can I live with hypertrophic cardiomyopathy?

Even though hypertrophic cardiomyopathy can cause serious health problems and even sudden death, you may never have any symptoms of the disease. Many adults diagnosed with hypertrophic cardiomyopathy do very well and survive to old age. It seems that children diagnosed with hypertrophic cardiomyopathy have the greatest risk for severe health problems as a result of this disease.

Because of the risk of sudden death, it is important for people with hypertrophic cardiomyopathy to avoid strenuous activity and intense exercise.

Getting moderate exercise under your doctor's supervision, eating a low-fat diet, and avoiding alcohol overuse are all ways to promote a healthy heart. Your doctor will recommend regular office visits to monitor this condition.

Frequently Asked Questions

Many people with hypertrophic cardiomyopathy do not have symptoms. However, if symptoms develop, initially they generally include:

• Shortness of breath (dyspnea), especially with exercise or exertion.
• Chest pain (angina).
• Fainting or near-fainting (syncope), especially with exertion.
• Heart palpitations, an uncomfortable awareness of the heart beating rapidly or irregularly.

Sudden death may occur from the onset of ventricular tachycardia (a type of rapid heart rate) or other dangerous arrhythmias. A genetic factor appears to influence which people with hypertrophic cardiomyopathy are more prone to sudden death. Other risk factors for sudden death include severe obstruction of the left ventricle, multiple fainting (syncope) episodes, recurring episodes of ventricular tachycardia, and an abnormal drop in blood pressure during exercise.⁴

Although it can occur in any age group, sudden death is most shocking when it happens to young adults or athletes. While these tragic deaths are often given prominence in the media, recent studies show that sudden death is more rare (1% per year) than once believed.⁵

Complications of hypertrophic cardiomyopathy

Atrial fibrillation is a common complication of hypertrophic cardiomyopathy. This abnormal heart rhythm interferes with the normal pumping of the heart. It can cause blood clots to develop in the heart, which can break off and travel through the bloodstream (systemic embolism). This may cause a stroke, heart attack, or blocked blood flow to an arm or leg.

Heart failure may develop if the disease progresses. In heart failure, the heart's lower chambers are not able to pump blood effectively enough to meet the body's needs for oxygen and nutrients. Common symptoms include fluid buildup (edema) in the legs, ankles, and feet; shortness of breath while lying down or exercising; and increased urination at night.

Athlete's heart syndrome

People who exercise regularly and vigorously often develop changes in their heart muscle that can be confused for hypertrophic cardiomyopathy. In such athletes, the heart muscle grows to adapt to the extra demands from physical activities. This condition is called athlete's heart syndrome. But unlike hypertrophic cardiomyopathy, athlete's heart syndrome does not cause life-threatening heart rhythms and sudden death. It is a benign, or harmless, condition. When an athlete stops training, the heart returns to a normal size unlike those with hypertrophic cardiomyopathy, in which the heart remains enlarged.

Hypertrophic cardiomyopathy can be difficult to diagnose because it may not always cause symptoms. The first step in diagnosing heart problems is a thorough medical history and physical exam.

Your doctor will ask you about any family history of hypertrophic cardiomyopathy or any heart disease. Your doctor will also want to know if any relatives died an early and sudden death. Sometimes when young people die of cardiac arrest from hypertrophic cardiomyopathy, the disorder is not discovered because autopsies are not always performed.

During the physical exam, your doctor will listen to your heart with a stethoscope. If any extra or unusual heart sounds (gallops or murmurs) are heard, it may mean the structure of the heart is abnormal.

You will usually have one or more of the following tests to help your doctor diagnose and treat your condition.

Electrocardiogram

An electrocardiogram (ECG or EKG) measures the electrical activity as it moves through the heart during contraction and relaxation. An abnormal electrocardiogram may be the first sign of hypertrophic cardiomyopathy in people who do not have any symptoms.

Echocardiogram

An echocardiogram (echo) is a type of ultrasound exam that uses high-pitched sound waves to create an image of the heart, which is seen on a television screen. An echo is the main tool used to help doctors diagnose hypertrophic cardiomyopathy and its severity.

Echocardiography can be used to:

• Estimate how well the lower left chamber of the heart (left ventricle) is able to fill when the heart expands and measure how much blood is pumped out as it contracts (ejection fraction).
• Determine if the heart valves are functioning normally.
• Measure overall heart size.
• Determine if the heart muscle (myocardium), including the wall that separates the left and right chambers of the heart, is unusually thick.
• Measure the degree that blood flow is reduced during contraction (systole) if the wall that separates the left and right chambers of the heart is abnormally thick.

Physical exam, electrocardiogram, and echocardiogram are the best ways to diagnose hypertrophic cardiomyopathy. People with a family history of sudden death, especially young athletes or those who are considering starting an exercise program, should talk to their doctor about being tested for hypertrophic cardiomyopathy. These tests may also help evaluate a person who faints during strenuous physical activity.

Patients who are considered to be low risk will not see their doctor as often as patients considered at high risk, usually around every 3 years. An echocardiogram is usually done again if your symptoms change or get worse.

Exercise test

Your doctor may have you run on a treadmill or pedal a stationary bike while he or she looks at how well your heart and lungs are working. An exercise test can give the doctor (and you) an idea of how hard and how long you can exercise.

The results of an exercise test may show that you have a higher risk for serious health problems due to hypertrophic cardiomyopathy. Some doctors recommend an exercise test before beginning any treatment for hypertrophic cardiomyopathy.

Chest X-ray

A chest X-ray produces a photographic image of the heart using rays of intense light energy that pass through the body and project an image on a film. An X-ray can show information about the heart's size and shape. In later stages of hypertrophic cardiomyopathy, an X-ray may reveal signs of pulmonary edema, which is fluid buildup in the lungs.

Cardiac catheterization (cardiac cath) or coronary angiography

During a cardiac catheterization or coronary angiogram, a long, thin tube (catheter) is threaded through an artery or vein in the arm or groin and into the heart to measure pressure in the heart chambers. Dye can be injected through the catheter to see whether the coronary arteries are blocked, how well the heart chambers are pumping, and whether heart valves are leaking.

Angiography may be done if the results of the echocardiogram are inadequate. Angiography may also be used to check if surgery would be an option for treatment of hypertrophic cardiomyopathy.

Genetic testing

Genetic testing can identify some genes that are related to this condition. Many people who have relatives with hypertrophic cardiomyopathy wonder if they or their children should have genetic testing. So far, routine genetic testing is not yet practical because there are so many possible abnormal genes that cause the disease. Genetic testing is presently used in a small number of cases when the specific genetic mutation in the affected relative has been identified.

Initial treatment

Many people with hypertrophic cardiomyopathy do not need treatment. But in some cases, having a thickened heart muscle can cause problems. If symptoms develop, treatment is usually recommended. Medicines cannot cure hypertrophic cardiomyopathy, but they may be used to treat complications, including atrial fibrillation and heart failure. These medicines include:

• Beta-blockers. Beta-blockers, such as propranolol (Inderal, for example) or atenolol (Tenormin), are often used to treat people who develop symptoms such as shortness of breath or chest pain. They lower blood pressure, slow heart rate, and improve blood flow, which helps decrease symptoms and improves your ability to exercise. They may even prevent or delay the progression of heart failure related to hypertrophic cardiomyopathy.
• Calcium channel blockers. If you do not improve after taking beta-blockers, your doctor will probably try a calcium channel blocker, such as verapamil (Calan or Isoptin, for example). These medicines also slow heart rate and lower blood pressure. Conversely, your doctor may first try a calcium channel blocker and switch to a beta-blocker if you don't get results. These medicines usually are not given at the same time.
• Disopyramide. The antiarrhythmic medicine disopyramide (Norpace) is sometimes used, especially if you have fainting or near-fainting episodes. This medicine can decrease the force with which the heart contracts and reduce the number of abnormal heart rhythms. It helps limit symptoms of heart failure.
• Amiodarone. This is a powerful antiarrhythmic medicine that sometimes is used to treat people with hypertrophic cardiomyopathy who have ventricular tachycardia or atrial fibrillation (two types of rapid heartbeat) or who are at high risk of sudden death. Research on amiodarone continues, but so far the drug has not been shown conclusively to prevent sudden death. In addition, long-term use of amiodarone may cause serious side effects in some people.⁴

Atrial fibrillation occurs in about one in four people with hypertrophic cardiomyopathy. In atrial fibrillation, abnormal electrical impulses cause the upper chambers of the heart (atria) to fibrillate, or quiver, resulting in irregular and rapid beating of the ventricles, the heart's main pump. For most people, this aspect of atrial fibrillation in itself is usually not life-threatening. However, for people who have hypertrophic cardiomyopathy, atrial fibrillation can increase your risk for other abnormal heart rhythms that can be life-threatening. It also increases your risk for heart failure and stroke. For these reasons, most doctors aggressively treat atrial fibrillation in people who have hypertrophic cardiomyopathy. Aggressive treatment usually means using medicines to control the heart rate or rhythm and/or electrical cardioversion to return the heart to its normal rhythm.² For more information, see the topic Atrial Fibrillation.

Anticoagulants often are prescribed for people who have atrial fibrillation. Anticoagulants help protect against blood clots that develop in the heart. Blood clots can be dangerous because they may break loose and travel through the bloodstream (thromboembolism), which may cause a stroke, heart attack, or blocked blood flow to an arm or leg.

Most people with hypertrophic cardiomyopathy should be assessed by a cardiologist to determine their risk for ventricular tachycardia, an abnormally fast heart rate that can result in sudden death. For those in a high-risk category, the implantable cardioverter-defibrillator (ICD) appears to be the most effective treatment for preventing sudden death. In a large study of people with hypertrophic cardiomyopathy who were at high risk of sudden death, ICDs identified ventricular tachycardia and successfully restored a normal heartbeat in some people who had this life-threatening arrhythmia.⁶

Because of the risk of sudden death, it is important for people with hypertrophic cardiomyopathy to avoid too much strenuous activity and intense exercise. About 50% of sudden deaths in people with hypertrophic cardiomyopathy occur during or just after strenuous physical activity.¹ Talk to your doctor about what level of exercise and what kinds of activities are safe. Prolonged activity in hot weather is not recommended, because dehydration can also worsen symptoms in people with hypertrophic cardiomyopathy.

Ongoing treatment

It is important for people with high-risk hypertrophic cardiomyopathy to have frequent check-ups with their doctor. People who are low risk may not see their doctor as often. But you may see the doctor more often if you have a change in your symptoms or your overall health. When symptoms appear or start to get worse, a check-up might include an echocardiogram (echo), electrocardiogram (ECG, EKG), or exercise test. Your doctor will talk about your symptoms and your health history. You may also talk about the health history of people in your family. These regular visits will help your doctor identify any risk factors you may have for sudden cardiac death and other serious medical conditions.

If symptoms develop, treatment is usually recommended. Medicines cannot cure hypertrophic cardiomyopathy, but they may be used to treat complications, including atrial fibrillation and heart failure. After medicines are started, most people need to take them for the rest of their lives.

Treatment if the condition gets worse

If you develop serious heart rhythm problems or are at high risk for sudden death, your doctor might recommend an implantable cardioverter-defibrillator (ICD).

Medicines for heart failure may be used if hypertrophic cardiomyopathy progresses to that advanced state. For more information, see the topic Heart Failure.

A surgery called a myectomy or myomectomy may be advised for some people when medicines do not help relieve severe symptoms of heart failure (NYHA class III and IV) due to hypertrophic cardiomyopathy. In this surgery, a portion of overgrown heart muscle is removed. Often the excess muscle tissue is found in the septum, which divides the left and right lower heart chambers (ventricles). An overgrown septum can interfere with the function of the left ventricle and limit blood flow out of the heart. Most people who have this surgery (about 70%) recover well and end up with fewer symptoms. After surgery, physical activity is easier too. These results have been seen for 5 years and longer.³

Another option for people with hypertrophic cardiomyopathy is nonsurgical septal reduction. When the area of the heart muscle that divides the right and left chambers (septum) becomes too thick, the lower left heart chamber (left ventricle) becomes obstructed, which hinders its ability to pump normally. The thickened septum is reduced in size by injecting alcohol into the coronary artery that supplies this area of the heart with blood. The alcohol destroys some of the heart muscle in the thickened septum, thereby reducing the obstruction and improving the left ventricle's pumping ability. Advantages of this procedure are that major surgery and lengthy recovery are avoided because the alcohol can be given through a catheter during a cardiac catheterization procedure. Placement of a permanent pacemaker is sometimes needed after this procedure.⁴

Studies show that this procedure decreases symptoms and increases quality of life over several years. However, long-term effects have not been well studied. Experts recommend that this complex procedure be performed in a large medical center where the staff has substantial experience with it.²

A pacemaker can be implanted surgically to improve the pumping action of the heart. This is done most commonly when there are complications from myectomy or septal reduction. Leads (wires) from the pacemaker are placed on both upper and lower heart chambers (atria and ventricles). Since the pacemaker controls both heart chambers, it is called dual-chamber pacing. Dual pacemakers may also benefit people older than 65 for whom surgery is not an option.² Dual-chamber pacing is not used often but it can be very helpful for a small number of people with hypertrophic cardiomyopathy.

A heart transplant is a treatment option available to a small number of people who have severe, end-stage hypertrophic cardiomyopathy. This procedure involves surgically removing the diseased heart and replacing it with a healthy heart donated by a person who has recently died. There are limited donor hearts available. In addition, the eligibility requirements for a transplant are very specific. For more information, see the topic Heart Failure.

Because of the risk of sudden death, it is important for people with hypertrophic cardiomyopathy to avoid too much strenuous activity and intense exercise. About 50% of sudden deaths in people with hypertrophic cardiomyopathy occur during or just after strenuous physical activity.¹ Talk to your doctor about what level of exercise and what kinds of activities are safe. Because dehydration can also worsen symptoms in people with hypertrophic cardiomyopathy, prolonged activity in hot weather is not recommended.

The following self-care recommendations are also important.

• Avoid drinking alcohol. Long-term overuse of alcohol appears to increase the risk of developing certain types of heart problems.
• Don't smoke. Tobacco use increases the risk of coronary heart disease, which can lead to a heart attack. For help quitting, see the topic Quitting Tobacco Use.
• Stay well hydrated (unless you have heart failure or another medical condition and need to limit your fluid intake).
• Weigh yourself daily. If fluid begins to build up rapidly, you will notice a sudden weight gain. Your doctor may tell you how much weight to watch for. But in general, call your doctor if you gain 3 lb (1.4 kg) or more in 2 to 3 days.

Follow your doctor's recommendations for regular exams to monitor your condition.

Because some people with hypertrophic cardiomyopathy may be at increased risk for sudden death, it is a good idea for family members to learn CPR (cardiopulmonary resuscitation).

For more information, see the topic Heart Failure.

Organizations

• Coronary Artery Disease
• Dilated Cardiomyopathy
• Heart Failure
• Restrictive Cardiomyopathy

Citations

1. Wynne J, Braunwald E (2004). The cardiomyopathies. In DP Zipes et al., eds., Braunwald's Heart Disease, 7th ed., pp. 1659–1696. Philadelphia: Elsevier Saunders.

2. Maron BJ, et al. (2003). American College of Cardiology/European Society of Cardiology clinical expert consensus document on hypertrophic cardiomyopathy. Journal of the American College of Cardiology, 42(9): 1–27.

3. Maron BJ (2002). Hypertrophic cardiomyopathy: A systematic review. JAMA, 287(10): 1312–1320.

4. Nishimura RA, et al. (2004). Hypertrophic cardiomyopathy. In V Fuster et al., eds., Hurst's the Heart, 11th ed., pp. 1909–1936. New York: McGraw-Hill Medical Publishing Division.

5. Maron BJ, et al. (1999). Clinical course of hypertrophic cardiomyopathy in a regional United States cohort. JAMA, 281(7): 650–655.

6. Maron BJ, et al. (2000). Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy. New England Journal of Medicine, 342(6): 365–373.

Other Works Consulted

• Maron BJ, et al. (1999). Assessment of permanent dual-chamber pacing as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy. Circulation, 99(22): 2927–2933.

• O'Rourke RA (1999). Cardiac pacing: An alternative treatment for selected patients with hypertrophic cardiomyopathy and adjunctive therapy for certain patients with dilated cardiomyopathy. Circulation, 100(8): 786–788.

• Roberts R, Sigwart U (2005). Current concepts of the pathogenesis and treatment of hypertrophic cardiomyopathy. Circulation, 112(2): 293–296.

• Spirito P, Maron BJ (1999). Perspectives on the role of new treatment strategies in hypertrophic obstructive cardiomyopathy. Journal of the American College of Cardiology, 33(4): 1071–1075.

• Watkins H (2000). Sudden death in hypertrophic cardiomyopathy. New England Journal of Medicine, 342(6): 422–423.

• Winakur S, Jessup M (2004). Heart failure. In DC Dale, DD Federman, eds., ACP Medicine, section 1, chap. 2. New York: WebMD.