Hypertrophic cardiomyopathy (HCM)

Hypertrophic cardiomyopathy, also called HCM, is a condition that causes the heart's muscle wall to thicken and stiffen, making it harder for the heart to pump blood efficiently. It can affect people of all ages and sometimes runs in families. With early diagnosis and the right hypertrophic cardiomyopathy treatment, most people can manage their symptoms and lower their risk of complications.

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Medical diagram comparing a healthy heart and left ventricular hypertrophy.

Anatomy of the heart

Your heart relies on a strong, coordinated pumping action to move blood through its four chambers and out to the rest of your body. The wall between the heart's lower chambers, called the septum, plays an important role in this process by helping direct blood flow from the left ventricle to the aorta, the main artery that carries oxygen-rich blood throughout the body.

In hypertrophic cardiomyopathy, this wall becomes abnormally thick. Over time, the thickening can stiffen the heart muscle, make it harder for the ventricle to fill with blood and, in some cases, block blood flow to the aorta. This is known as obstructive hypertrophic cardiomyopathy, while cases without a blockage are called nonobstructive.

Overview

Symptoms

Hypertrophic cardiomyopathy can cause a range of symptoms, and some people have no noticeable symptoms at all. When symptoms do occur, they may include:

Chest pain or shortness of breath during exercise
Dizziness, lightheadedness or fainting after physical activity
Fatigue or weakness unrelated to exertion
A heart murmur detected during an exam
Fluttering, irregular or pounding heartbeats
Swelling in the legs, ankles or abdomen

Symptoms can stay mild for years or progress over time, so regular checkups with a cardiologist are important for monitoring changes.

Causes

Hypertrophic cardiomyopathy often develops because of an inherited genetic change that affects how the heart muscle grows. Common contributing factors include:

A family history of HCM, since the condition is frequently passed down from parent to child
Genetic mutations that affect the heart muscle, even without a known family history
Age-related changes in heart structure
High blood pressure, which can contribute to thickening of the heart wall

Not everyone who carries an HCM-related gene will develop noticeable heart changes or symptoms.

Risk factors

Certain factors can increase the likelihood of developing hypertrophic cardiomyopathy, though having one or more of these doesn't mean you'll develop this condition:

A parent, sibling or child with hypertrophic cardiomyopathy
A known genetic mutation linked to HCM
Older age
High blood pressure

Knowing your risk factors can help you and your care team decide whether screening or genetic testing makes sense for you.

Diagnosis

Diagnosing hypertrophic cardiomyopathy typically starts with a physical exam and a conversation about your symptoms and family history. An echocardiogram is the most common test used to confirm the diagnosis by creating images of the heart's structure and function. Your cardiologist may also recommend:

Electrocardiogram (EKG) to measure the heart's electrical activity
Genetic testing to check for inherited gene mutations
Magnetic resonance imaging (MRI) for detailed images of the heart muscle
Stress testing to see how your heart responds to physical activity
Cardiac catheterization to evaluate blood flow and pressure within the heart
A Holter monitor, which records your heart's activity over 24 to 48 hours

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