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Cardiologists are drifting away from blanket restrictions on exercise for people with the most prevalent genetic cardiomyopathy causing sudden cardiac death in the young -- hypertrophic cardiomyopathy (HCM). But how are patients and physicians now expected to make personalized and informed decisions?

Fears of HCM patients triggering a life-threatening arrhythmia during exercise stem from the presumed unstable myocardial substrate in these individuals. In the past, expert opinion on this resulted in patients being barred from vigorous exercise and most competitive sports, despite the known benefits of regular physical activity.

Now, evidence continues to mount that exercise poses a lower risk for sudden death in HCM than previously thought. Recent data suggest that the largest proportion of sudden death in athletes, as well as young people in general, occurs in people with normal hearts, with HCM accounting for less than 10% of cases. Reporting biases keep the exact number of HCM-related deaths unknown, however.

Also muddying the water are observations that athlete sudden deaths, even when HCM is involved, commonly occur outside exercise.

Rachel Lampert, MD, an electrophysiologist at Yale School of Medicine in New Haven, Connecticut, said that we simply don't have data yet on continuing sports for patients who do not have defibrillators.

Data suggest that once an implantable cardioverter-defibrillator (ICD) is placed, the patient's risk from exercise is very low. Lampert's group found in a that athletes fitted with ICDs had no instances of physical injury or failure to terminate the arrhythmia over 2 years.

The prospective observational study comparing outcomes of HCM patients who exercise moderately or vigorously versus staying sedentary has finished enrolling and hopefully will be analyzed by Lampert's group by the end of this year, she said.

Acknowledging the gaps in the literature on HCM patients without ICDs, the latest guidelines have become more relaxed in keeping moderate- to high-intensity sports participation an option for patients. In particular, guidelines stressed weighing different risks and benefits in discussions between patient and clinician.

"The prior approach, in my opinion, was more paternalistic, that 'in the absence of data, we need to be cautious, so we should restrict patients from doing sports.' Now the current approach is more based on shared decision-making, which means that our role is to help patients and give them the information they need to make the decision," said Lampert in an interview.

For a patient who doesn't have any risk factors suggesting elevated risk, the cardiologist needs to share the data available and help the patient consider their own approach to risk, she added. "Some say, 'If you can't say it's risk-free, I'm not doing it' ... There are other people that say, 'Risk is a part of life. I'm going to live my life, not let potential small risks put a limit to what I do.'"

Indeed, a comprehensive risk assessment is key to shared decision-making, according to preventive and sports cardiologist Elizabeth Dineen, DO, of the University of California Irvine.

"We start with a history and physical, especially focusing on any exercise-related symptoms past or present and family history, and ensure we have echocardiogram, Holter monitor, stress test, and cardiac MRI data to guide the assessment and next steps," she told 乌鸦传媒.

Factors that point to greater risk include young age, a history of unexplained syncope or nonsustained ventricular tachycardia, late gadolinium enhancement on cardiac MRI, a thicker left ventricular wall, and a family history of sudden cardiac death.

"For those asymptomatic and deemed low risk for sudden cardiac death from a cardiovascular standpoint, the data is moving in the direction of supporting their participation if it is deemed an acceptable risk from the athlete, based on their individual risk and the intensity of exercise they wish to engage in," Dineen said.

There is an understanding that some risk does exist, she said. The level and intensity of competition could indicate an emergency action plan and/or additional support.

But some say there are downsides to this new way of doing things. Case in point: a situation where athlete, cardiologist, and trainer disagree on the level of acceptable risk.

"Undoubtedly, balancing patient autonomy with respect for the common good in order to prevent catastrophic events in sport is a massive challenge," wrote sports medicine physician Jonathan Drezner, MD, of the University of Washington in Seattle, and colleagues, in a .

"Most young athletes do not consider themselves vulnerable to the risks of sport, catastrophic injury, or sudden death. In combination with the lure of fame and/or fortune or family pressure for economic gain, this raises an important ethical question: can young athletes truly make an unbiased and informed decision under duress?" the group asked.

What clinicians can all agree on is that placing an ICD for the sole purpose of a lower-risk HCM patient participating in sports is a bad idea.

"A defibrillator is a great device for people who are at significant risk of dying from cardiac arrest. However, if you don't need one, you don't want one. The risk of implantation is not zero, and there are long-term potential downsides," Lampert said.

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