Hypertrophic cardiomyopathy, or HCM, is a genetic disease that causes the heart muscle to become thicker, making it harder for the heart to pump blood. It's a condition that affects one in 200-500 people. HCM often goes undiagnosed but is usually discovered during cardiac testing.
In HCM, the patient will develop heart failure symptoms. Up to two-thirds of patients also develop an obstruction of the outlet of the heart, according to Omar Wever-Pinzon, MD, medical director of the Hypertrophic Cardiomyopathy Program at University of Utah Health. "We call that left ventricular outflow tract obstruction, and it too leads to symptoms of heart failure," he says. Those symptoms include:
- Chest pain
- Shortness of breath
- Peripheral edema
- Abdominal bloating
With obstructive HCM, chest pain and fainting are more prevalent, while with unobstructive HCM there is more fatigue and fluid retention.
Until recently, the only way to screen family members for HCM was through periodic echocardiograms. Today, genetic testing is the standard for families in which a genetic mutation is identified. Hypertrophic cardiomyopathy genetics is also fast evolving. If you had genetic testing more than five years ago and suspect HCM, Wever-Pinzon advises you to review the results with your doctor and potentially be tested again because new genes have been added to the panel.
Diagnosis and Prevalence
HCM is diagnosed through cardiac imaging. Normal thickness is 10 millimeters or less, but HCM occurs when the heart wall thickening is 13 to 15 millimeters. "When the ventricular wall gets to three centimeters or more, that's very concerning as it increases your risk for a dangerous heart rhythm that can lead to sudden death," Wever-Pinzon says. This affects one percent of HCM patients.
Clinicians assess several factors to determine risk:
- Family history
- Fainting without explanation
- Heart monitor findings
- Heart muscle measurements
- Amount of cardiac fibrosis
- Heart function status
- Presence of an apical aneurism
Wever-Pinzon says a risk factor for sudden death is if the patient has a special kind of hypertrophic cardiomyopathy where they develop an apical aneurysm, or an aneurysm of the tip of the heart.
Treatment and Management
Of the two types of HCM—with and without obstruction—hypertrophic obstructive cardiomyopathy is easier to manage with:
- Medications (beta blockers, calcium channel blockers, or disopyramide)
- Septal reductive therapies, which involve surgery (septal myectomy)
- Catheter-based procedure (alcohol septal ablation)
"Unobstructed HCM requires that we relax the heart, and there are no medications specifically for that," Wever-Pinzon clarifies.
That said, in April 2022, the FDA will review a new agent for hypertrophic cardiomyopathy treatment, a group of medications called cardiac myosin inhibitors. "We're part of those studies," which are "very promising," Wever-Pinzon says.
In the meantime, diuretics are prescribed to help reduce excessive fluid that comes with unobstructive HCM, plus medicine to control blood pressure. "In some patients, we're attempting apical and extended septal myectomies," Wever-Pinzon says. "The option of last resort is a heart transplant."
Tracking is also critical. An echocardiogram or a cardiac MRI is done initially, followed by an annual EKG. The cardiac MRI or echocardiogram is repeated every three to five years.
Children and the Future
Children are typically born with a normal looking heart, but thickening of the heart muscle can occur in the teenage years. Young athletes that die suddenly with strenuous exertion typically have hypertrophic cardiomyopathy, Wever-Pinzon says, which is why HCM patients are advised to avoid competitive sports. "Recreational and moderate exercise seems to be OK though, as long as it doesn't trigger symptoms," he says.
Hypertrophic cardiomyopathy is a disease that's managed, but not cured—at least not yet. "There are studies looking at gene therapy," Wever-Pinzon says. "If they prove successful, that would be something leading to a cure."