Myocardial Fibrosis in Endurance Athletes Raises Arrhythmia Concerns

A recent study published on July 17, 2025, in *Circulation: Cardiovascular Imaging* reveals that nearly half of long-term male endurance athletes exhibit signs of myocardial fibrosis, potentially increasing their risk for arrhythmias. Conducted by Dr. Wasim Javed of the Leeds Institute of Cardiovascular and Metabolic Medicine, this research analyzed a cohort of 106 asymptomatic male cyclists and triathletes over the age of 50, all of whom had trained for at least 10 hours per week for more than 15 years. The study aimed to explore the prevalence of myocardial fibrosis and its association with ventricular arrhythmia.

The findings indicate that 47.2% of the participants showed evidence of focal myocardial fibrosis, predominantly affecting the basal inferolateral segment of the left ventricle. This condition was linked to a nearly fivefold increase in the risk of developing ventricular arrhythmia (hazard ratio [HR], 4.7; 95% CI, 1.8-12.8; P = .002). During a median follow-up period of 720 days, 21.7% of athletes experienced episodes of ventricular arrhythmia, with 2.8% developing sustained ventricular tachycardia.

The methodology involved advanced cardiovascular assessments, including MRI and exercise testing, which revealed that athletes with myocardial fibrosis had significantly higher left ventricular end-diastolic volumes (113 ± 18 mL/m² vs. 106 ± 13 mL/m²; P = .04) and native T1 times (1252 ± 46 ms vs. 1241 ± 39 ms; P = .03). Furthermore, 71.4% of athletes with fibrosis exhibited premature ventricular contractions during exercise testing, compared to 42% without fibrosis (P = .003).

Dr. Javed emphasized, "Myocardial fibrosis on cardiovascular imaging was independently associated with the risk of ventricular arrhythmia in healthy, asymptomatic veteran male endurance athletes. Other predictors included left ventricular dilatation and exercise-induced premature ventricular contractions." The potential for these heart changes to lead to sudden cardiac arrest necessitates further investigation into the long-term implications for endurance athletes.

However, the researchers acknowledged several limitations, including the small sample size and the homogeneous nature of the cohort, which consisted solely of male participants. The findings may not apply to female or racially diverse athletes. Additionally, the study's reliance on single-lead implantable loop recorders limited the ability to precisely localize the origin of ventricular arrhythmias.

The implications of this study extend beyond athletic circles, as it raises crucial questions about cardiac health in endurance sports. As the popularity of endurance training continues to rise, further research is essential to explore the risks associated with long-term intense physical activity. The study was funded by the National Institute for Health and Care Research Leeds Biomedical Research Centre, the British Heart Foundation, and the Leeds Clinical Research Facility.

In conclusion, while endurance training can offer numerous health benefits, the potential cardiac risks highlighted by this study warrant attention from medical professionals and athletes alike. The identification of myocardial fibrosis as a significant risk factor for arrhythmia underscores the need for regular cardiovascular evaluations in veteran endurance athletes, especially those who may not exhibit any overt symptoms. Future research should aim to clarify the relationship between myocardial fibrosis and sudden cardiac events in this population, paving the way for improved screening and preventive strategies.