"CV Sports Chat" is an interview series that includes expert discussions relative to sports and exercise cardiology and the health care management of athletes.*

The LIVE-HCM (Lifestyle and Exercise in Hypertrophic Cardiomyopathy) study explored the hypothesized connection between intense exercise and life-threatening ventricular arrhythmias (VAs) in individuals with hypertrophic cardiomyopathy (HCM).¹ The study investigators concluded that there was no significant increase in arrhythmic events (4.6% vs. 4.7%) associated with vigorous exercise. In this interview with esteemed sports cardiologist Rachael Lampert, MD, FACC, we delve into "exercise prescription" in athletes with HCM.

Can you please tell me a little about the history of HCM, exercise-induced sudden cardiac death (SCD), and exercise restriction? Are there any data that vigorous exercise increases the risk of SCD in patients with HCM?

Historically, it was believed that individuals with HCM who engaged in physical activity were at a higher risk of experiencing VAs, resulting in sudden cardiac arrest or SCD. This belief was based on registries that retrospectively identified athletes who experienced SCD as having HCM and that these deaths most often occurred during exercise. However, these early reports were influenced by reporting biases from pathologists and the media. It is important to note that there were no previous prospective studies investigating whether exercise actually increased the occurrence of SCD in individuals with HCM.

Risk stratification for sudden death in HCM was derived in an all-comers population. Can you please describe your thoughts about extrapolating low, moderate, and high risk from these models to athletes? When do you consider exercise restriction here?

When assessing the potential risk of SCD in athletes, the approach is to utilize established algorithms, such as those laid out in guidelines, with ancillary tools, such as the European SCD risk calculator. These tools provide valuable information to make informed decisions regarding an athlete's risk. In cases in which an athlete is deemed at high risk, an implantable cardioverter-defibrillator (ICD) is the recommended course of action. The need for an ICD should be determined independently of an athlete's wish to compete. Our algorithms are not perfect, and there is a small chance of SCD for all patients with HCM, even in those without these described markers. However, our data highlight that vigorous exercise does not increase this small but not zero risk; thus, restriction is not indicated. Whether those with outflow tract obstruction need treatment to reduce risk is not known.

The consensus approach to HCM over the last few decades has led to an inadvertent promotion of a sedentary lifestyle. Given the RESET-HCM (Randomized Exploratory Study of Exercise Training in Hypertrophic Cardiomyopathy), ICD Sports Safety Registry, and LIVE-HCM findings, what do you think about creating an exercise prescription for athletes with HCM?

We need to think about two groups of patients—those who are sedentary and those who are competing. For the sedentary, we know from the RESET-HCM findings that we should be promoting and encouraging physical activity. For the athlete, the LIVE-HCM and ICD Sports Registry findings point us away from the concept of "exercise prescription" and toward collaborative decision making to help individuals meet their exercise objectives.^1,2

Can you please provide more detail about an HCM-specific exercise prescription with respect to dynamic and resistance training? What are the precautions that you would discuss with this athlete?

The LIVE-HCM study investigated arrhythmic risk and was not designed to determine the superiority or potential harm of exercise in general or of a particular type of training on the progression of cardiomyopathy. Although there is a theoretical concern that resistance training could exacerbate hypertrophy, more data are needed here. Therefore, I would not say there needs to be a particular precaution, but it is important to be mindful of any symptoms that may arise.

In the LIVE-HCM study, vigorous exercise was defined as an activity with METs ≥6 and exercising ≥60 hours per year. Is there an upper limit in the intensity and hours an athlete should train?

Many studies have shown that the level of exercise among the general population follows a "J-shaped" curve, indicating that those who engage in extreme exercise may be at a higher risk of experiencing adverse cardiac events. Although there was a wide range of exercise intensity in the LIVE-HCM study, whether there is an upper limit and where it falls for patients with HCM, as for the general population, are not yet determined, emphasizing the need for a collaborative decision regarding one's level of participation in sports or a specific activity.

Do you think there is a role for cardiopulmonary exercise testing (CPET) in defining the individualized exercise regimen for athletes with HCM?

For sedentary individuals now getting in shape, the RESET-HCM findings suggest that engaging in moderate-intensity exercise can enhance one's exercise capacity without any deleterious effects, and CPET may be beneficial in setting up the training regimen.³ As athletes are already exercising vigorously, a role for CPET might be for an athlete developing a change in exercise tolerance.

With these recent studies demonstrating the short-term safety of exercise in the setting of HCM, can individualized exercise discussions, in the absence of high-risk clinical markers, lead to more athletes safely returning to competition?

Our study findings show that the risks are similar, so they should not be restricted from participating in their sports. However, it is critical that risk overall be assessed by an HCM expert to determine the need for an ICD. Discussion with an HCM specialist is critical to understand how exercise fits into the overall risk of HCM. The LIVE-HCM study findings did not show that arrhythmias never occur with exercise; rather, they showed that engaging in vigorous exercise did not increase the overall risk of arrhythmias, which can occur at any time.

Finally, what does the future hold regarding exercise "prescription" and the role of shared decision making?

Our take-home message is about the athlete engaging in a thoughtful discussion regarding risk stratification with a qualified HCM specialist and jointly arriving at a decision. This approach aligns with the current direction of the medical field, which prioritizes collaborative decision making over a more paternalistic approach. Rather than simply "prescribing" a course of action, it is crucial to consider the athlete's values and preferences. By doing so, the focus shifts toward an approach of advocacy and cooperation rather than a one-size-fits-all solution.

References

1. Lampert R, Ackerman MJ, Marino BS, et al.; LIVE Consortium. Vigorous exercise in patients with hypertrophic cardiomyopathy. JAMA Cardiol 2023;8:595-605.
2. Lampert R. Sport participation in patients with implantable cardioverter-defibrillators. Curr Treat Options Cardiovasc Med 2019;21:66.
3. Saberi S, Wheeler M, Bragg-Gresham J, et al. Effect of moderate-intensity exercise training on peak oxygen consumption in patients with hypertrophic cardiomyopathy: a randomized clinical trial. JAMA 2017;317:1349-57.