Hypertrophic cardiomyopathy (HCM) is a genetic heart disease that causes thickening of the walls of the heart’s left ventricle. This can make it more difficult for the heart to pump blood throughout the body and may limit the amount of blood that can be pushed out with each heartbeat.

HCM is one of the most common forms of inherited heart disease, affecting an estimated 750,000 people in the United States. However, HCM is a progressive disease, meaning the thickening of the heart wall typically worsens over time.

People with HCM may not develop or notice symptoms for many years. Some symptoms may be mild or not appear until later in adulthood. Others may not recognize them if they don’t impact their activity levels. As a result, only about 13% of people with HCM know they have the condition.

Clinical and genetic testing for HCM can help increase the number of people aware of their condition. This article looks at testing for HCM, including who should have it done and how it works.

Testing for HCM is typically recommended for people who have a first-degree relative who has been diagnosed with HCM. Because HCM is a genetic condition, you are more likely to develop HCM if you have a family member who is affected than those who do not have a family history of the disease.

Not all people will show signs or symptoms of HCM when they are first tested, but symptoms can appear later.

If someone has a first-degree relative with HCM but doesn’t show signs of disease immediately, their doctor may want to continue monitoring them. This is especially true if they are found to have a genetic marker known to be associated with HCM.

In other cases, you may be referred to a cardiologist if you have symptoms consistent with HCM. Some of the most common symptoms include:

  • shortness of breath with activity
  • chest pain
  • fainting or dizziness
  • fluttering or pounding heartbeats
  • exhaustion
  • swelling in the legs, ankles, feet, or abdomen

The American Heart Association and American College of Cardiology also recommend young athletes undergo a preparticipation physical exam, which includes a history and physical examination, to assess for underlying heart conditions.

Testing for HCM should be performed by a cardiologist, preferably one who practices in a center experienced with HCM care.

Everyone tested for HCM will have a physical examination and a cardiac evaluation. This will likely include a combination of an electrocardiogram (EKG), which measures electric signals from the heart, and imaging, such as an echocardiogram.

Additional tests may include:

  • continuous ECG monitoring for 24 to 48 hours to evaluate for arrhythmias
  • exercise stress testing
  • cardiac MRI

Cardiologists use these tests to look for changes in the heart’s structure and how it beats. Thickening of the left ventricle wall is a strong indicator of HCM. Other cardiac abnormalities can lead to heart pumping and filling problems, mitral regurgitation, and obstruction of blood flow from the heart.

Testing can also help determine whether your heart is beating in a typical rhythm. Changes to a usual heart rhythm are known as arrhythmia, which can affect the way blood flows through the heart.

These tests help cardiologists diagnose HCM and guide treatment decisions. Muscle strain and abnormal blood flow in the heart can lead to complications such as:

  • heart failure
  • blood clots
  • stroke
  • sudden cardiac death

By evaluating how your heart works, your healthcare team can develop the best treatment plan to help manage HCM and protect your health.

Genetic testing of a blood sample may also be recommended, particularly for people with a relative with HCM. This test can also tell your doctor whether your symptoms are caused by another heart disease other than HCM.

Many gene mutations cause HCM. Mutations in the sarcomere protein, a component of the heart’s muscle, are responsible for most cases of HCM.

About 60% of people with HCM have a family history of it. Even in those who have no family history of HCM, 30% will have a disease-causing mutation that can be found through genetic testing.

Your cardiologist and an experienced genetic counselor can help you decide whether genetic testing is right for you. They will also help you interpret your genetic results after testing to help with family planning and evaluating your risk for severe complications.

If testing reveals signs of HCM, your cardiologist will perform confirmatory testing and establish a treatment plan that includes regular monitoring.

Even if initial test results don’t reveal signs of HCM, you may still receive ongoing testing. Symptoms of HCM can develop over time, meaning that even if they aren’t present when you first test, they may occur later.

For people with a genetic marker known to increase the likelihood of developing HCM, your cardiologist may suggest testing every 1 to 2 years for children and adolescents and every 3 to 5 years for adults.

If you get genetic testing, or if you do and no known disease-causing mutation is found, testing may be repeated every 3 to 5 years.

HCM is a progressive disease, and symptoms can develop at any point. Because genetic mutations cause the condition, it’s more likely to appear in those who have a family history of the condition.

Regular testing and monitoring can help people more likely to develop HCM stay on top of their heart health. If a loved one is diagnosed with HCM, an experienced cardiologist can help you understand your risks and what kind of testing may be needed.