Endurance Athletes Face Elevated Heart Risk From Scar Tissue

New study links myocardial fibrosis to significant arrhythmia danger in veteran cyclists and triathletes

A concerning finding for the physically elite: nearly half of asymptomatic male endurance athletes studied showed signs of myocardial fibrosis, a form of heart scarring that dramatically increases the risk of dangerous heart rhythm disturbances.

Hidden Heart Damage Found in Elite Athletes

Researchers observed that 47.2% of veteran male endurance athletes, all free of known cardiovascular disease, presented with myocardial fibrosis. This scarring was not linked to blocked arteries but was predominantly found in the lower rear section of the left ventricle. This condition correlated with a near fivefold greater chance of developing ventricular arrhythmias.

Study Details Uncover Alarming Association

The prospective observational study tracked 106 male competitive cyclists and triathletes over 50 years old. These participants had committed to at least 10 hours of exercise weekly for over 15 years. Exclusions were made for anyone with a prior heart condition.

Participants underwent comprehensive cardiac evaluations, including MRI scans with contrast dye, stress tests, and the implantation of loop recorders to continuously monitor for heart rhythm abnormalities over a median follow-up period of two years. The primary concern was the occurrence of ventricular arrhythmias.

Scarring Linked to Serious Heart Rhythm Issues

The cardiac MRI results revealed that myocardial fibrosis was a significant independent predictor of ventricular arrhythmia. Even after accounting for the size of the left ventricle, the association remained strong (hazard ratio 4.7). Athletes experiencing arrhythmias also tended to have larger left ventricles and altered native T1 times, indicators of potential cardiac changes.

Furthermore, athletes with fibrosis were more likely to experience premature ventricular contractions during exercise tests, and these contractions often displayed more unusual characteristics compared to those without fibrosis.

Expert Insights and Future Implications

The study authors noted, In this prospective study, myocardial fibrosis on cardiovascular magnetic resonance imaging was independently associated with the risk of ventricular arrhythmia in healthy, asymptomatic veteran male endurance athletes. They added that other factors like left ventricular dilation and exercise-induced premature ventricular contractions also pointed to higher arrhythmia risk. The researchers suggest these findings may offer clues to predicting sudden cardiac arrest risk but emphasize the need for more research to confirm these links and explore whether fibrosis indicates an undetected form of cardiomyopathy.

Wasim Javed, PhD, from the Leeds Institute of Cardiovascular and Metabolic Medicine in the UK, led the study, which was published in *Circulation: Cardiovascular Imaging*.

Acknowledged Study Limitations

The research team recognized that the study’s findings might not be universally applicable due to its relatively small participant group and the highly specific nature of the athletes involved. The limited scope may affect generalizability to women or athletes of different ethnic backgrounds. Additionally, the single-lead nature of the recorders prevented pinpointing the exact origin of arrhythmias to correlate them definitively with fibrosis sites. The connection between ventricular arrhythmias and sudden cardiac death is indirect, requiring further investigation for direct clinical implications.

Contextualizing Athlete Heart Health

This study adds to a growing body of research examining the long-term cardiovascular effects of extreme endurance training. While exercise is widely beneficial, understanding potential risks for specific physiological changes is crucial for athlete well-being. For example, a 2023 report highlighted that while regular exercise is linked to a longer lifespan, excessive amounts could potentially increase risks for certain cardiac issues in predisposed individuals (Source: Mayo Clinic, various reports on exercise physiology).