Hypertrophic cardiomyopathy 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 associated with certain gene mutations and can be passed down from parents to children.
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, as these can lead to life-threatening irregular heartbeats (arrhythmias) and, rarely, sudden cardiac death.
The most common genetic heart disease, HCM is usually inherited. It’s an autosomal dominant condition, meaning a person needs to inherit a mutated gene from only one parent to develop HCM. A person with HCM has a 50 percent chance of passing the condition to their children.
HCM can also be caused by high blood pressure and aging. In some people, the cause of HCM is not known. The incidence rate, or prevalence, of HCM is estimated to be 1 out of every 500 people. HCM is a chronic disease that can get worse over time, but early treatment and lifestyle changes can reduce the risk of complications.
When a cell divides, it passes its DNA along to the new cells — but sometimes, 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 genes in the new cells to make proteins that function improperly. Scientists have identified some genetic causes of HCM. However, there are hundreds of gene mutations associated with the condition. The significance of many of these mutations is not clear.
Genetic testing can identify variations (changes) in your genes. For example, genetic testing can help identify if you have one of the two most common gene mutations among people with HCM:
The overall purpose of genetic screening for HCM is to identify the specific gene causing the condition. Depending on your test results, your cardiologist may be able to predict potential disease progression and recommend treatments. Additionally, if the test reveals a known HCM-causing variant, it can indicate that family members may be at risk of developing HCM in the future.
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 genetic test results may show:
If the test results show that a person with HCM doesn’t have a known HCM-causing genetic mutation, there is no clinical reason for family members to get an HCM genetic test.
For people with HCM that’s genotype-positive — meaning they have a genetic mutation that may lead to disease — the American College of Cardiology recommends that all their first-degree relatives (e.g., parents, siblings, children) undergo screening to identify those who may be genetically at risk for developing HCM. Family members of any age can undergo this type of screening. Screening frequency is usually guided by family history.
Undiagnosed HCM is the most common cause of sudden cardiac death in young athletes. Therefore, if you have a family history of sudden cardiac death, or your child experiences symptoms such as shortness of breath or dizziness while exercising, you should discuss these 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 is insufficient.
Genetic testing for HCM generally includes:
The genetic counseling step is important to make sure that a person fully understands the benefits and potential harms of genetic testing. Genetic testing may be expensive, and insurance companies may not fully cover the costs. You can call your insurance company before testing to understand the costs.
People usually undergo additional genetic counseling after receiving their test results to ensure that they and their family members understand them. Depending on the results, your health care provider or cardiologist may recommend interventional approaches. For example, if your testing shows that you are genotype-positive for a mutation linked to HCM, your doctor may recommend additional testing. For example, an echocardiogram (ECG or EKG) is a noninvasive test that uses ultrasound to look at the structure of your heart to determine if its walls are thickened.
Treatments for HCM can include:
An implantable cardioverter defibrillator is a commonly used device that helps prevent sudden death in people with known heart diseases such as tachycardia (rapid heart rate) or fibrillation (quivering or irregular heart rhythm).
A major drawback of genetic testing is, 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 communicate any concerns to your cardiologist, as professional guidance will help you navigate detection and treatment options.
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