Hypertrophic cardiomyopathy (HCM)

DEFINITION

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 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).

CAUSES

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 impedes blood flow out of the heart. This condition is sometimes called obstructive hypertrophic cardiomyopathy.

Sometimes hypertrophic cardiomyopathy occurs without significant blocking 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 nonobstructive hypertrophic cardiomyopathy.

SYMPTOMS

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

• Shortness of breath, especially during exercise
• Chest pain, especially during exercise
• Fainting, especially during or just after exercise or exertion
• 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 112 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