This finding could lead to fewer activity restrictions for people with this condition, which involves the heart muscle becoming thickened and enlarged.
HCM is an inherited disorder that affects about one in 500 people worldwide. It is associated with sudden cardiac death in young people.
Yet the U.S. National Institutes of Health-funded study found that those who exercised vigorously are no more likely to die or experience severe cardiac events than those who exercised moderately or not at all.
“Based on these data, we’re learning that we don’t need to universally restrict HCM patients from participating in vigorous exercise, something that’s so important to all of us,” said study co-author Dr. Rachel Lampert, a professor of medicine at Yale School of Medicine, in New Haven, Conn.
“Individuals with this condition should talk to a health care provider with expertise in HCM about getting back on the field, back in the pool and back on the court, if that’s what they want to do,” Lampert said in an institute news release. “Getting an expert evaluation is key to determining degree of risk for all HCM patients, and critical before going back to play.”
To study this, the researchers recruited 1,660 people with HCM or who carried the gene for it but had no signs of the condition. Patients ranged from ages 8 to 60, and were recruited from 42 high-volume HCM medical centers in the United States, United Kingdom, Canada, Australia and New Zealand.
People who could not exercise for established medical reasons, including those awaiting heart transplantation or with severe asthma, were excluded from the research.
About 15% of the participants reported they were sedentary. Another 43% said they did moderate exercise, such as brisk walking. About 42% said they exercised vigorously with activities including running or fast swimming.
The study followed the groups for about three years, looking for sudden deaths, resuscitated sudden cardiac arrests, appropriate implantable cardioverter-defibrillator (ICD) shocks, and something called arrhythmic syncope, which can include fainting or passing out.
Using a statistical formula, the researchers found that about 1.5% of participants a year who reported exercising vigorously died or had severe cardiac events. This was the same percentage as those who exercised moderately or described themselves as sedentary.
It was also similar to what was experienced by competitive exercisers (39% of the vigorous group), and for a subgroup of 42 young people who participated in interscholastic competitive sports such as baseball, track, soccer and basketball.
“This finding is significant and provides a measure of reassurance that exercise may be safe for persons with HCM,” said Dr. Patrice Desvigne-Nickens, a medical officer in the U.S. National Heart, Lung and Blood Institute’s division of cardiovascular sciences.
“However, we stress that individuals with the condition should not be exercising until they’ve first had an evaluation by a provider with expertise in HCM about their overall risk of sudden cardiac death. It is important to know that all patients with HCM could potentially be at risk for sudden death,” she added.
HCM makes it harder for the heart to pump blood because the thickened lower chambers of the heart are too stiff. Some patients may experience shortness of breath, chest pain, fatigue and a life-threatening irregular heartbeat, known as arrhythmia. Rarely, this causes sudden death.
People with this condition typically take medication or have a surgically implanted device, such as an ICD, to detect an arrhythmia.
In the past, recommendations to restrict all exercise have been based on caution, not on specific data, the researchers noted.
The study findings were published online May 17 in JAMA Cardiology.
The American Heart Association has more on hypertrophic cardiomyopathy.
SOURCE: U.S. National Institutes of Health, news release, May 17, 2023