Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle 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 and can lead normal lives with no significant problems. However, in a small number of people with HCM, the thickened heart muscle can cause shortness of breath, chest pain or problems in the heart's electrical system, resulting in life-threatening abnormal heart rhythms (arrhythmias) or sudden death.

Symptoms

Signs and symptoms of hypertrophic cardiomyopathy may include one or more of the following:

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

Causes

Hypertrophic cardiomyopathy is usually caused by abnormal genes (gene mutations) that cause the heart muscle to grow abnormally thick.

In most people with hypertrophic cardiomyopathy, the muscular wall (septum) between the two bottom chambers of the heart (ventricles) becomes thicker than normal. As a result, the thicker wall may block blood flow out of the heart. This is called obstructive hypertrophic cardiomyopathy.

If there's no significant blocking of blood flow, the condition is called nonobstructive hypertrophic cardiomyopathy. However, the heart's main pumping chamber (left ventricle) may become stiff. This makes it hard for the heart to relax and reduces the amount of blood the ventricle can hold and send to the body with each heartbeat.

People with hypertrophic cardiomyopathy also have an abnormal arrangement of heart muscle cells (myofiber disarray). This can trigger arrhythmias in some people.

Risk factors

Hypertrophic cardiomyopathy is usually passed down through families (inherited).

If you have a parent with hypertrophic cardiomyopathy, you have a 50% chance of having the genetic mutation for the disease.

Parents, children or siblings of a person with hypertrophic cardiomyopathy should ask their doctors about screening for the disease.

Complications

Many people with hypertrophic cardiomyopathy (HCM) don't have significant health problems. But complications of hypertrophic cardiomyopathy can include:

• Atrial fibrillation. Thickened heart muscle, as well as the abnormal structure of heart cells, can cause changes in the heart's electrical system, resulting in fast or irregular heartbeats. Atrial fibrillation can also increase your risk of developing blood clots, which can travel to your brain and cause a stroke.
• Blocked blood flow. In many people, the thickened heart muscle blocks the blood flow leaving the heart, causing shortness of breath with exertion, chest pain, dizziness and fainting spells.
• Mitral valve problems. If the thickened heart muscle blocks the blood flow leaving the heart, the valve between the left atrium and left ventricle (mitral valve) may not close properly. As a result, blood can leak backward into the left atrium (mitral valve regurgitation), possibly leading to worsening symptoms.
• Dilated cardiomyopathy. In a very small number of people with HCM, the thickened heart muscle may become weak and ineffective. The ventricle becomes enlarged (dilated), and its pumping ability becomes less forceful.
• Heart failure. The thickened heart muscle can eventually become too stiff to effectively fill the heart with blood. As a result, your heart can't pump enough blood to meet your body's needs.
• Sudden cardiac death. Rarely, hypertrophic cardiomyopathy can cause heart-related sudden death in people of all ages. Because many people with hypertrophic cardiomyopathy don't realize they have it, sudden cardiac death may be the first sign of a problem. It can happen in seemingly healthy young people, including high school athletes and other young, active adults.

Prevention

There is no known prevention for hypertrophic cardiomyopathy. But it's important to identify the condition as early as possible to guide treatment and prevent complications.

If you have a first-degree relative — a parent, sibling or child — with hypertrophic cardiomyopathy, doctors may recommend genetic testing to screen for the condition. However, not everyone with HCM has a currently detectable mutation. Also, some insurance companies may not cover genetic testing.

If genetic testing isn't done, or if the results aren't helpful, then your doctor may recommend echocardiograms on a regular basis if you have a family member with hypertrophic cardiomyopathy. Adolescents and competitive athletes should be screened once a year. Adults who don't compete in athletics should be screened every five years.