Heart Health
Advances in managing hypertrophic cardiomyopathy
There's reassuring news about exercise as well as a new, first-in-class drug for people with this inherited heart muscle disease.
- Reviewed by Christopher P. Cannon, MD, Editor in Chief, Harvard Heart Letter; Editorial Advisory Board Member, Harvard Health Publishing
About one in 500 people has a condition that affects muscle cells in the heart, causing the walls of the heart to thicken and enlarge (see illustration). Called hypertrophic cardiomyopathy (HCM), it's often caused by genetic mutations and is the most common inherited form of heart disease, although many people have never heard of it. And among those who are familiar with HCM, misconceptions and unwarranted worry about the condition are common.
"Until recently, HCM was feared as the most common cause of sudden cardiac death in young athletes," says Dr. Carolyn Ho, medical director of the Cardiovascular Genetics Center at Harvard-affiliated Brigham and Women's Hospital. However, newer, more comprehensive research involving the general population, college athletes, and military recruits shows that while HCM remains an important underlying cause of sudden cardiac death in otherwise seemingly healthy individuals, it's not the most common one. The exact reasons for these rare but devastating events often remain a mystery, even after an autopsy.
Additionally, a large observational study published in 2022 in JAMA Cardiology (co-authored by Dr. Ho) suggests that even vigorous exercise appears to be safe for most people with HCM. The study followed 1,660 people with HCM, ages 8 to 60, for three years. While 15% reported being sedentary, 43% said they did moderate exercise and 42% said they did vigorous exercise. During the study period, 1.5% of those who reported exercising vigorously died or had a severe cardiac event — the same percentage as among those who described themselves as sedentary or who reported doing moderate exercise. "This study provides important evidence to encourage people with HCM to exercise, which provides the same health benefits as it does for everyone," says Dr. Ho.
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In hypertrophic cardiomyopathy, the heart's septum and left ventricle are thicker than normal, which can restrict blood flow. |
A wide variation in symptoms
Some people with HCM have no symptoms or very mild ones. But some people feel breathless, lightheaded, or have chest pain. These symptoms occur when the heart fails to relax and fill properly or when the thickened heart muscle obstructs the flow of blood leaving the heart. The resulting turbulence in the blood flow causes a murmur that a doctor can hear while listening to the heart. Changes in the structure of the heart cells, combined with the thickened muscle, can affect the heart's electrical system. This can lead to atrial fibrillation (a fast, irregular heartbeat that raises the risk of stroke) and in rare cases, ventricular fibrillation, which can cause sudden cardiac death.
The vast majority of HCM cases involve genes responsible for making sarcomeres, the basic units of muscle. Alterations in the genetic code (called mutations or variants) of these genes pass from one generation to the next in a dominant pattern. That means that parents, siblings, and children of an affected person have a 50% chance of having inherited the same variant. But even if you have the same variant as your mother, for example, your symptoms may be very different from hers, Dr. Ho explains.
Diagnosing HCM
Sometimes HCM is discovered by chance on a routine electrocardiogram (a test of the heart's electrical system) or when a doctor hears a murmur. Other people undergo testing after experiencing symptoms or after a family member is diagnosed.
"We refer everyone newly diagnosed with HCM for genetic counseling to consider genetic testing and to understand the implications for their family," says Dr. Ho. Many people feel anxious or confused after their diagnosis, but they should understand that with good medical care, most people with HCM can enjoy a good quality of life and that treatments are rapidly improving.
Living with HCM
For those with symptoms, many treatments — including medications and procedures — are available. Several common drugs can help the heart pump more effectively. In 2022, the FDA approved mavacamten (Camzyos), a first-in-class medication that targets the underlying cause of HCM by inhibiting a protein that helps power heart muscle contractions. A similar drug, aficamten, is in the final stages of clinical testing.
"It's great to have effective new medical options for people with HCM," says Dr. Ho. These medications are a welcome alternative to surgery or catheter-based procedures to thin the heart muscle, which until now were the only options when existing drugs didn't improve symptoms.
Image: © Alkov/Getty Images
About the Author
Julie Corliss, Executive Editor, Harvard Heart Letter
About the Reviewer
Christopher P. Cannon, MD, Editor in Chief, Harvard Heart Letter; Editorial Advisory Board Member, Harvard Health Publishing
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