At the 36th Bethesda Conference in 2005, a panel of cardiology experts developed guidelines restricting exercise for people with hypertrophic cardiomyopathy with the aim of reducing sudden cardiac death. Now, more recent evidence indicates that these restrictions probably didn’t reduce death rates and may have caused secondary problems associated with inactivity.
If you have HCM and want to increase your activity level, it’s essential to talk with your cardiologist about the benefits and risks. Then, work together with your doctor to develop an individualized plan based on your current fitness level, HCM symptoms, and your individual risk of suffering a cardiac emergency.
The Latest Evidence in Favor of Exercise for Patients with HCM
Rachel Lampert, MD, of Yale University, was the lead author of the LIVE-HCM observational study, which was presented to delegates at the ACC/WCC conference in March 2023. This observational study included more than 1500 patients between 8 and 60 years of age who had inherited hypertrophic cardiomyopathy, making this the largest prospective observational study on HCM and vigorous exercise to date.
Of 1,534 study participants:
- Around 40% were female.
- Around 20% were younger than 25.
- 42% were classified as participating in vigorous exercise.
- 43% were classified as participating in moderate exercise.
- 16% were classified as leading a sedentary lifestyle.
In addition to these 1,534, a further 126 people were enrolled who had “a genetic variant for HCM but no left ventricular hypertrophy.” Every six months, the study subjects reported their activity levels and heart symptoms over a period of three years.
At the end of the study period, the researchers observed that:
- 77 study participants had experienced an “endpoint” during the study: mortality, resuscitated cardiac arrest, a ventricular arrhythmia that was shocked by an implantable cardioverter defibrillator, or fainting that was thought to be the result of arrhythmia.
- Of these participants, the likelihood of experiencing an endpoint was not statistically higher for those who exercised vigorously or who identified as competitive athletes as it was for those who were sedentary or exercised moderately.
- None of the participants with a genetic variant of HCM but without left ventricular hypertrophy experienced one of the endpoints listed above.
Taking these observations together, Lampert concluded that the data “do not support the universal restriction of vigorous exercise in patients with HCM.” Rather, she advises patients with hypertrophic cardiomyopathy to work together with an experienced cardiologist to:
- Assess the patient’s individual risk factors with a thorough evaluation
- Determine the most appropriate treatments
- Decide which level of exercise intensity to pursue
- Identify warning signs, which may include chest pain, heart palpitations, dizziness, fainting, and fatigue
- Develop plans for dealing with emergencies. This could mean carrying a portable defibrillator like the Philips HeartStart FRx or the LIFEPAK CR2.
Patients with HCM were also advised to talk with family members about the condition because the genetic variants that cause hypertrophic cardiomyopathy are often passed down through the family.
Why Were Patients with HCM Previously Advised to Avoid Competitive Sports?
Cardiologists traditionally advised patients with HCM to avoid competitive sports or not to exercise at all. There are several reasons for this:
- HCM is recognized as a cause of sudden cardiac death in young competitive athletes.
- HCM causes a thickening of the heart muscle, which can make it harder for the heart to pump blood around the body. Vigorous exercise was thought to put additional strain on the heart.
- Vigorous exercise was thought to create an unstable substrate in the heart and increase susceptibility to arrhythmias and sudden cardiac death.
- Many of the high-profile athlete deaths that were attributed to hypertrophic cardiomyopathy occurred when the patients were playing competitive sports.
When the clinical guidelines for HCM were established in 2005, evidence from large-scale prospective studies was not available to show whether vigorous exercise increased the likelihood of sudden cardiac arrest, once other factors (age, gender, weight, type of sport) were accounted for. In medicine, specialists prefer to err on the side of caution, especially when lives are at risk.
What Newer Research Reveals about Vigorous Exercise and HCM
Since 2005, there have been several studies (in addition to the study cited above) that examined the relative risk of suffering a heart arrhythmia during vigorous exercise or while playing competitive sports.
- A 2017 randomized clinical trial involving 136 patients with HCM found that a moderate-intensity structured exercise training program could increase the functional capacity (and hence the exercise capacity) of patients with this heart condition. The improvements were measured by peak oxygen consumption on cardiopulmonary exercise testing.The findings of this study are important because increased functional capacity could help to slow or prevent the progression of hypertrophic cardiomyopathy to heart failure, making exercise an important part of a long-term strategy for living with HCM.
- In a 2017 literature review published in the Journal of the American College of Cardiology, it was noted that:
- Most sudden deaths in young people with HCM don’t happen during physical exertion. According to research cited in the review, 30% of sudden deaths occur during or after exercise and 40% occur outside of the context of exercise. In a UK study, 43% of the deceased athletes with HCM died at rest.
- While the U.S. National Registry of Sudden Death in Athletes shows that most of the reported deaths happened during exertion, deaths that occurred at rest may be less likely to have been reported to the registry or commented on in the media.
- A 2018 literature review published in Circulation observed that:
- The overall occurrence of sudden cardiac death (SCD) in young competitive athletes is very low and is similar to the rate of SCD in the general population of young people: around 1 to 3 occurrences for every 100,000 person-years.
- HCM accounted for only 8% of all deaths registered by the US National Collegiate Athletic Association.
- A meta-analysis of registries, cohort studies, and autopsy series from 1990 to 2014 showed that more victims of sudden cardiac death had structurally normal hearts (26.7%) than hearts with thickened muscle due to HCM (10.3%).
- In a prospective population study in Australia and New Zealand, only 4% of sudden cardiac deaths in children and young adults were attributable to HCM and only 6 cases of SCD happened during or right after exercise.
- In the ICD Sports Safety Registry, shocks were just as common when the individuals weren’t exercising as they were during exercise.
The authors of the review conclude that hypertrophic cardiomyopathy exercise restrictions are unlikely to reduce the incidence of sudden cardiac death. However, they stress the importance of early screening, risk assessments, and surveillance for children and young adults with HCM—whether or not they participate in sports.
Moderate Exercise May Have a Protective Effect
According to a 2020 review published in the British Journal of Cardiology, only 45% of patients with HCM meet the minimum guidelines for exercise. However, the four-month study of 136 HCM patients cited earlier showed that moderate exercise could significantly increase oxygen capacity and improve quality-of-life physical functional capacity.
We also know that exercise addresses some of the other risk factors for sudden cardiac arrest. As just one example, athletes have a lower heart rate than people who don’t exercise. Physical activity can also help people maintain a healthy weight, which is one of the AHA’s Essential 8 for heart health. The risks of inactivity for HCM patients should always be balanced against the perceived risk of exercise-induced arrhythmias.
What To Do If You Have Heart Symptoms or a Family History of HCM
While the 2023 Lambert study shows that there’s no reason—statistically—to restrict exercise universally for HCM, all of the authors cited in this article agree that screening and medical supervision are essential. In many cases, athletes can play sports with a heart murmur, HCM, or another type of structural heart abnormality with the appropriate level of supervision and an onsite AED in case they need to be revived.
If someone in your family has experienced sudden cardiac arrest (and been revived), passed away from sudden cardiac death, or has a structural abnormality like hypertrophic cardiomyopathy, it’s essential to go for diagnostic testing. This may involve an echocardiogram and electrocardiogram (ECG or EKG), blood tests, and other tests as recommended by your doctor. Once you know what your individual risk factors are, you can work with your cardiologist to make a plan for commencing or resuming a structured exercise training program.
High-Level Exercise Might Be Okay – But Get the Go-Ahead from Your Doctor First
Recent research findings are challenging the long-held notion that patients with HCM need to avoid intensive exercise or be barred from playing competitive sports. Going simply by the numbers, HCM patients are just as likely to experience an arrhythmia outside of exercise as they are on the playing field, court, or track.
While these findings are great news for HCM patients who want to resume exercise training or take up a sport (both of which are great for overall health), they should develop an individualized return-to-exercise plan together with an experienced cardiologist and be prepared to recognize and respond to warning signs.
