Older male endurance athletes may be at a higher risk for cardiac arrhythmias while exercising if they have scarring in their hearts, according to a study published in the European Journal of Preventive Cardiology.

Peter Swoboda, PhD, a cardiologist at the University of Leeds in Leeds, England, and his colleagues had previously found that many older male endurance athletes had myocardial fibrosis, although it is unclear if long-term high-level training is to blame. The researchers wanted to see if this fibrosis was linked to heart problems, which could help determine whether, or how, athletes should modify their exercise regimes.

“We spend a lot of clinical time telling people who exercise that maybe they should cut back, but that’s not really based on evidence,” Swoboda told Medscape Medical News.

Ventricular Tachycardia and Fibrosis

The study involved 106 male cyclists and triathletes over the age of 50 who had been training at a high level for many years — at least 10 hours a week for 15 years. The cohort included amateur athletes as well as some ex-professionals and at least one former Olympian, said the study’s lead author, Wasim Javed, PhD, who is also from the University of Leeds.

Participants underwent cardiac MRIs to detect fibrosis and had implantable loop recorders installed to monitor arrhythmias. The researchers tracked daily exercise using digital activity monitoring devices.

Over 2 years of follow-up, 55 ventricular arrhythmia events occurred in 25 participants during or just after exercise. Most were non-sustained ventricular tachycardia, but three were longer and potentially more serious events. All three occurred during exercise.

Arrhythmias were much more common in athletes with cardiac fibrosis — 76% of all events, including all three sustained events, occurred in those participants. There were no training differences between athletes with and without arrhythmias.

“The presence of scarring was the strongest indicator of risk for arrhythmias,” Javed said in an interview.

This study focused on men because they are at a much higher risk — 9 in 10 cardiac deaths during sports activities are in older men — and the loop recorders used in the study are an expensive piece of equipment. The team now has funding to replicate the experiment in women as well, Swoboda said.

Exercise Still Safe

Jack Goodman, PhD, who studies the cardiac consequences of endurance exercise at the University of Toronto in Toronto, Ontario, Canada, said that while the study does not prove a causal link between scarring and arrhythmias, the findings are “eyebrow-raising,” especially given the high-quality long-term data from the loop recorders.

“This is probably the best study so far in terms of rigor; we just don’t know yet if the fibrosis is pathological or not,” he said.

Goodman, who was not involved with the study, said the results can help guide healthcare providers in their care of patients who experience arrhythmias during exercise. 

“Ventricular tachycardia in athletes is a reason for concern, and if you add evidence of fibrosis, it’s worth further investigation to rule out a known pathology,” he said. “But it would be premature to suggest curtailing exercise.”

The study authors agreed that the results should not be seen as cautioning against exercise. “We don’t want to spread the message that exercise is harmful; that’s not how we interpret these results,” said Swoboda. “A lot of this can be dealt with if you act on the symptoms early.”

Swoboda, Javed, and Goodman reported no relevant financial relationships.

Brian Owens is a freelance journalist based in New Brunswick, Canada.