Hypertrophic cardiomyopathy (HCM) is a medical condition in which the heart muscle becomes thicker than normal. In general, “hypertrophy” is the medical term used to describe the excessive development of any organ. HCM is linked to certain gene mutations (changes or variants) and can be passed down from parents to children. If you have this condition or a family history of HCM, genetic testing may help your cardiologist (heart doctor) determine if you have one of the genetic variants known to cause the condition.

HCM can cause shortness of breath or chest pain during exercise, dizziness, lightheadedness, fainting, and swelling in the ankles, feet, legs, or abdomen. However, many people living with HCM experience very few symptoms. HCM can be dangerous if it causes changes in the electrical signals in the heart, which can lead to life-threatening arrhythmias (irregular heartbeats) and, rarely, sudden cardiac death.

What Is Genetic Screening for Hypertrophic Cardiomyopathy?

HCM is often inherited and is the most common genetic heart disease. It’s an autosomal dominant condition, meaning a person needs to inherit a mutated gene from only one parent to develop it. A person with HCM has a 50 percent chance of passing the variant to their children, though this doesn’t necessarily mean those children will have HCM.

HCM is usually inherited and is the most common genetic heart disease.

In some people, the cause of HCM isn’t known. Researchers estimate that HCM affects 1 in 500 people. This chronic disease can get worse over time, but early treatment and lifestyle changes can reduce the risk of complications.

What Causes Gene Mutations?

When a cell divides, its DNA is passed along to the newly formed cells. Sometimes, however, the DNA doesn’t copy correctly, resulting in a genetic mutation. You could think of it as copying a list of instructions and accidentally inserting typos. The mutation can cause the new cells’ genes to make proteins that don’t function correctly. Scientists have identified some genetic causes of HCM, but hundreds of gene mutations are associated with the condition. The significance of many of these changes isn’t clear.

Genetic testing can identify variations in genes. For example, the results can reveal if you have one of the two most common gene mutations among people with HCM — MYH7 and MYBPC3.

What Are the Benefits of Screening for Hypertrophic Cardiomyopathy?

The overall purpose of genetic screening for HCM is to pinpoint the gene causing the condition. Depending on your test results, your cardiologist may be able to predict if and how the disease will progress over time and recommend treatments. If the test reveals a variant known to cause HCM, it can indicate that family members may also be at risk of developing HCM.

Who Should Be Screened and When?

The American College of Cardiology and American Heart Association guidelines recommend that a person who’s been clinically diagnosed with HCM undergo genetic testing. The results may show:

• No known mutation
• A variant of unknown significance
• A variant known to cause HCM

If the test results don’t show the presence of a variant known to cause HCM, there’s no clinical reason for family members to get an HCM genetic test. However, not all cases of HCM are genetic. If a family member has symptoms of HCM, they could still have the condition.

If the results show a variant of unknown significance (VUS), this means researchers don’t have enough information to know if the genetic mutation is linked to HCM. A genetic counselor can provide more information about next steps.

For people with genotype-positive HCM — they have a genetic mutation that may lead to disease — the American College of Cardiology recommends that all their first-degree relatives (parents, siblings, or children) get screened to figure out who may be at risk of HCM. Family members of any age can undergo this type of screening. First-degree relatives should also be offered genetic counseling and cardiac screening.

Undiagnosed HCM is a possible cause of sudden cardiac death in young athletes. If you have a family history of sudden cardiac death, or if your child experiences symptoms such as shortness of breath or dizziness while exercising, you should speak with your child’s doctor. They may recommend further assessment for adolescents who play competitive sports. The presence of symptoms also requires further clinical assessment. Genetic testing alone isn’t enough.

What Is the Hypertrophic Cardiomyopathy Screening Process?

Genetic testing for HCM generally includes:

• Pretest genetic counseling
• Collection of blood or saliva for lab analysis
• A follow-up appointment to discuss the genetic test results

The genetic counseling step is important to make sure that a person fully understands the benefits and potential harms of genetic testing. The tests may be expensive and not fully covered by insurance. You can call your insurance company before testing to understand the costs.

What Are the Next Steps After the Test?

People usually undergo additional genetic counseling to ensure that they and their family members understand their test results. Your healthcare provider or cardiologist may also recommend more tests.

For example, if your genetic test results show that you’re genotype-positive for a mutation associated with HCM, your doctor may recommend additional testing. They may do an echocardiogram, a noninvasive test that uses ultrasound to look at the structure of your heart and determine if its walls are thickened. They may also recommend an electrocardiogram (ECG), cardiac MRI scans, stress tests, or other diagnostic procedures.

Treatments for HCM can include:

• Risk identification and regular follow-up appointments
• Medications
• Procedures
• Lifestyle changes

Not everyone with HCM has a known mutation — scientists are still discovering which ones contribute to the condition.

An implantable cardioverter defibrillator is a commonly used device that helps prevent sudden death in people with known and life-threatening heart diseases such as tachycardia (rapid heart rate) or fibrillation (quivering or irregular heart rhythm).

Get Professional Guidance About Genetic Screening

A major drawback of genetic testing is that researchers still don’t fully understand the meaning of certain mutations. Not everyone with HCM has a known mutation — scientists are still discovering which ones contribute to the condition. Testing may detect mutations in some genes, but these don’t mean a person will develop HCM or any other medical problem.

In many instances, genetic screening may not provide helpful results, and routine echocardiograms may be necessary to check for HCM. Be sure to talk with your cardiologist about any concerns so that they can help you navigate diagnosis and treatment options.

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On MyHeartDiseaseTeam, people share their experiences with hypertrophic cardiomyopathy and other cardiovascular diseases, get advice, and find support from others who understand.

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