Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle (myocardium) becomes abnormally thick (hypertrophied). The thickened heart muscle can make it harder for the heart to pump blood.

Hypertrophic cardiomyopathy often goes undiagnosed because many people with the disease have few, if any, symptoms. In a small number of people with HCM, the thickened heart muscle can cause shortness of breath and problems in the heart's electrical system, resulting in life-threatening abnormal heart rhythms (arrhythmias).

Fortunately, people with hypertrophic cardiomyopathy often lead normal lives with no significant problems.

Signs and symptoms of hypertrophic cardiomyopathy include:

  • Shortness of breath, especially during exercise
  • Chest pain, especially during exercise
  • Fainting, especially during exercise or exertion
  • Dizziness
  • Fatigue
  • Sensation of rapid, fluttering or pounding heartbeats (palpitations)
  • Heart murmur, which a doctor might detect while listening to your heart

When to see a doctor

A number of conditions can cause shortness of breath and heart palpitations. It's important to get a prompt, accurate diagnosis and appropriate care. See your doctor if you experience any symptoms associated with hypertrophic cardiomyopathy.

Call 911 or your local emergency number if you experience any of the following symptoms for more than a few minutes:

  • Rapid or irregular heartbeat
  • Difficulty breathing
  • Chest pain

Hypertrophic cardiomyopathy is usually caused by abnormal genes (gene mutations) that cause the heart muscle to grow abnormally thick. People with hypertrophic cardiomyopathy also have an abnormal arrangement of heart muscle cells, a condition known as myofiber disarray. This disarray can contribute to arrhythmia in some people.

The severity of hypertrophic cardiomyopathy varies widely. Most people with hypertrophic cardiomyopathy have a form of the disease in which the wall (septum) between the two bottom chambers of the heart (ventricles) becomes enlarged and obstructs blood flow. This condition is sometimes called hypertrophic cardiomyopathy with obstruction or hypertrophic obstructive cardiomyopathy. About 70 percent of people with obstructive HCM experience symptoms.

Sometimes hypertrophic cardiomyopathy occurs without significant obstruction of blood flow. However, the heart's main pumping chamber (left ventricle) may become stiff, reducing the amount of blood the ventricle can hold and the amount pumped out to the body with each heartbeat. This condition is sometimes called hypertrophic cardiomyopathy without obstruction or nonobstructive hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy is usually inherited. There's a 50 percent chance that the children of a parent with hypertrophic cardiomyopathy will inherit the genetic mutation for the disease. Close relatives — parents, children or siblings — of a person with hypertrophic cardiomyopathy should ask their doctors about screening for the disease.

Many people with hypertrophic cardiomyopathy don't experience significant health problems. But some people experience complications, including:

  • Arrhythmias. Thickened heart muscle, as well as the abnormal structure of heart cells, can disrupt the normal functioning of the heart's electrical system, resulting in fast or irregular heartbeats. Atrial fibrillation, ventricular tachycardia and ventricular fibrillation are among the arrhythmias that may be caused by hypertrophic cardiomyopathy.
  • Obstructed blood flow. In many people, the thickened heart muscle obstructs the blood flow leaving the heart. Obstructed blood flow can cause shortness of breath with exertion, chest pain, dizziness and fainting spells.
  • Dilated cardiomyopathy. Over time, thickened heart muscle may become weak and ineffective. The ventricle becomes enlarged (dilated), and its pumping ability becomes less forceful.
  • Mitral valve problems. The thickened heart muscle can leave a smaller space for blood to flow, causing blood to rush through your heart valves more quickly and forcefully. This increased force can prevent the valve between your heart's left atrium and left ventricle (mitral valve) from closing properly. As a result, blood can leak backward into the left atrium (mitral valve regurgitation), possibly leading to arrhythmia or heart failure.
  • Heart failure. The thickened heart muscle can eventually become too stiff to effectively fill with blood. As a result, your heart can't pump enough blood to meet your body's needs.
  • Sudden cardiac death. Ventricular tachycardia and ventricular fibrillation can cause sudden cardiac death. Hypertrophic cardiomyopathy is the leading cause of heart-related sudden death in people under the age of 30, although such deaths are rare.

You may be referred to a doctor who specializes in the diagnosis and treatment of heart conditions (cardiologist). Here's some information to help you prepare for your appointment.

What you can do

  • Find out if you need to follow any pre-appointment restrictions, such as changing your activity level or your diet.
  • Write down your symptoms and how long you've had them.
  • Take a list of all your medications, vitamins or supplements.
  • Write down your key medical information, including other diagnosed conditions.
  • Write down key personal information, including any recent changes or stressors in your life.
  • Write down questions to ask your doctor.

Questions to ask your doctor

  • What's the most likely cause of my symptoms?
  • What kinds of tests do I need?
  • What treatments can help?
  • What risks does my heart condition create?
  • How often will I need follow-up appointments?
  • Do I need to restrict my activities?
  • Should my children or other close relatives be screened for this condition, and should I meet with a genetic counselor?
  • How will other conditions that I have or medications I take affect my heart problem?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may make time to go over points you want to spend more time on. You may be asked:

  • When did you first begin experiencing symptoms, and how severe are they?
  • Have your symptoms changed over time? If so, how?
  • Does exercise or physical exertion make your symptoms worse?
  • Have you ever fainted?
  • Do you have a family history of heart disease?

What you can do in the meantime

Before your appointment, ask your family members if any relatives have been diagnosed with hypertrophic cardiomyopathy or have experienced unexplained, sudden death. It will help your doctor to know as many details as possible about your family medical history.

If exercise makes your symptoms worse, avoid strenuous exercise until you have seen your doctor and received specific exercise recommendations.

Your doctor is likely to recommend echocardiography. This imaging test allows your doctor to see whether your heart muscle is abnormally thick, your blood flow is obstructed and your heart valves are moving normally.

Types of echocardiography include:

  • Transthoracic echocardiogram (ECG). Gel is spread on your chest, and a device (transducer) is pressed firmly against your skin. The transducer aims an ultrasound beam through your chest to your heart, producing moving images of the working of the heart.
  • Transesophageal echocardiogram. A flexible tube containing a transducer is guided down your throat and into the tube connecting your mouth and stomach (esophagus). From there, the transducer can obtain more-detailed images of your heart. Although rarely done, this test may be recommended if it's difficult to get a clear picture of your heart with a standard echocardiogram or if the doctor wants to further examine your mitral valve.

Additional tests might be done to look for other effects of hypertrophic cardiomyopathy and help determine appropriate treatment. These additional tests include:

  • Treadmill stress test. Your heart rhythm, blood pressure and breathing are monitored with echocardiography while you walk on a treadmill. Your doctor may recommend an exercise stress test if you have symptoms but standard echocardiogram doesn't show obstructed blood flow.
  • Holter monitor, a portable ECG that records your heart's activity continuously over one to two days.
  • Cardiac catheterization, which measures the pressure of blood flow inside your heart. A catheter is inserted into an artery, usually in your groin area. The catheter is then carefully threaded to your heart chambers under guidance of an X-ray machine. Dye is injected through the catheter, and the X-ray machine makes images (angiograms) of your heart and blood vessels.
  • Cardiac MRI, which uses magnetic fields and radio waves to create images of your heart. Cardiac MRI is often used in addition to echocardiography if the echocardiogram is inconclusive.

Family screening

If you have a first-degree relative — parent, sibling or child — with hypertrophic cardiomyopathy, doctors may recommend that you be screened for the condition. There are two types of screening:

  • Genetic testing. Genetic tests may not provide a definitive answer because the genetic causes of hypertrophic cardiomyopathy aren't fully understood. Only 50 to 60 percent of families with HCM have a currently detectable mutation. Insurance companies may not cover genetic testing. Talk with your doctor about whether genetic testing could be an option for you.
  • Echocardiography. If genetic testing is not done, or if the results are not helpful, then your doctor may recommend regular echocardiography. Adolescents and competitive athletes should be screened once a year. Adults who don't compete in athletics should be screened every five years.

The goal of treatment is to relieve symptoms and prevent sudden cardiac death in people at high risk. Specific treatment varies depending on the severity of your symptoms.

The options include:

  • Medication to relax the heart muscle and to slow the heartbeat rate so that the heart can pump more efficiently. Your doctor may recommend beta blockers, the calcium channel blockers verapamil or diltiazem, or the sodium blocker disopyramide (Norpace).
  • Septal myectomy, an open-heart procedure in which the surgeon removes part of the thickened, overgrown septum between the ventricles. Removing part of this overgrown muscle improves blood flow and reduces mitral regurgitation. Myectomy may be recommended if medications don't relieve symptoms. Most people who have myectomy have no further symptoms. Septal myectomy is available only in medical centers that specialize in the treatment of HCM.
  • Septal ablation in which a small portion of the thickened heart muscle is destroyed by injecting alcohol through a catheter into the artery supplying blood to that area. Possible complications with this procedure include heart block — a disruption of the heart's electrical system — which requires implantation of a pacemaker.
  • Implantable cardioverter-defibrillator (ICD), a pager-sized device implanted in your chest like a pacemaker. An ICD continuously monitors your heartbeat. If a life-threatening arrhythmia occurs, the ICD delivers precisely calibrated electrical shocks to restore a normal heart rhythm. ICD may be recommended for people with hypertrophic cardiomyopathy who are at high risk of sudden cardiac death because of abnormal heart rhythms.

Lifestyle changes can reduce your risk of complications related to hypertrophic cardiomyopathy. Your doctor may recommend changes in your:

  • Physical activity level. Competitive sports are generally unsafe for people with hypertrophic cardiomyopathy. Some people may be able to participate in low-intensity physical activities. Ask your doctor for guidance.
  • Diet. A healthy diet is an important part of maintaining your heart health.
  • Weight management. Maintaining a healthy weight will prevent excessive stress on your heart and reduce health risks associated with surgery or other procedures.
  • Alcohol use. Drinking too much alcohol can trigger irregular heart rhythms. If you drink alcohol, ask your doctor for guidance about safe levels of use.

Being diagnosed with hypertrophic cardiomyopathy can cause a range of difficult emotions. Like many people with this condition, you may experience feelings of grief, fear and anger. These responses are appropriate to the lifestyle changes that come with your diagnosis.

Talk with your doctor if you are feeling hopeless, panicked or unable to cope. It may help to talk with a therapist. In some cases, your doctor also may recommend medications that treat problems such as anxiety and depression.

Because hypertrophic cardiomyopathy is inherited, it can't be prevented. But it's important to identify the condition as early as possible to guide treatment and prevent complications.

Preventing sudden death

Implantation of a cardioverter-defibrillator has been shown to help prevent sudden cardiac death, which occurs in only about 1 percent of people with HCM. Unfortunately, because many people with hypertrophic cardiomyopathy don't realize they have it, there are instances where the first sign of a problem is sudden cardiac death. These cases can happen in seemingly healthy young people, including high school athletes and other young, active adults. News of these types of deaths generates understandable attention because they're so unexpected, but parents should be aware these deaths are quite rare.

Still, experts in heart abnormalities generally recommend that people with hypertrophic cardiomyopathy not participate in most competitive sports with the possible exception of some low-intensity sports. Discuss specific recommendations with your cardiologist. The use of an implantable cardioverter-defibrillator should not be viewed as a substitute for these recommendations.

Jul. 03, 2014