Elsevier

American Heart Journal

Volume 226, August 2020, Pages 206-213
American Heart Journal

Clinical Investigation
High-intensity endurance training is associated with left atrial fibrosis

https://doi.org/10.1016/j.ahj.2020.05.015Get rights and content

Introduction

Endurance athletes are at higher risk for developing atrial fibrillation as compared to the general population. The exact mechanism to explain this observation is incompletely understood. Our study aimed to determine whether degree of left atrial fibrosis detected by late gadolinium-enhancement magnetic resonance imaging (LGE-MRI) differed between Masters athletes and non-athlete controls.

Methods

We recruited 20 endurance healthy Masters athletes and 20 healthy control subjects who underwent cardiac MRI. Healthy controls were recruited during screening colonoscopies and Masters athletes were recruited through word of mouth and at competitions. The two groups were age and gender matched. None of the participants were known to have an arrhythmia. Fibrosis, as measured by late gadolinium-enhancement, was measured in each participant by blinded readers. The degree of left atrial fibrosis was compared between the two groups. All participants were recruited from the Salt Lake City region and scanned at the University of Utah healthcare complex.

Results

Left ventricular function was normal in all study participants. Left atrial volumes were significantly larger in the athletes (74.2 ml ± 14.4) as compared to the healthy control subjects (60.8 mL ± 21.4) (P = .02). Mean left atrial fibrosis score, reported as a percentage of the LA, was 15.5% ± 5.9 in the athlete cohort compared to 9.6% ± 4.9 in the controls (P = .002).

Conclusions

To our knowledge this is the first study that describes, characterizes and specifically quantifies fibrotic changes within the left atrium of highly trained endurance athletes. Increased atrial fibrosis seen in this population may be an early indicator for endurance athletes at risk of developing atrial arrhythmias.

Section snippets

Study population

We recruited 20 endurance Masters athletes >35 years old who have participated in at least 10 years of competitive endurance sports and actively train for ≥10 hours weekly.14 Endurance activities included those that were highly dynamic with low static component: running, cycling, ski mountaineering, and Nordic skiing (Table1). For the athlete cohort, recruitment was done through word of mouth at training clubs and at competitions. Efforts were focused specifically on top finishers in local

Results

Overall, the 2 cohorts were very closely matched with few comorbidities. Athletes had significantly lower BSA. The athletes also weighed significantly less and had a lower body-mass index (BMI) (Table I). Participants in the athlete cohort reported training regularly for an average of 28.98 ± 8.65 years and a mean of 15.53 ± 6.9 hours each week (Table II). The majority of that time was spent training in endurance activities (12.48 ± 5.84 h/wk). Most athletes train in more than one sport but of

Discussion

To our knowledge, this is the first study which demonstrated an increased level of atrial fibrosis in Masters endurance athletes as compared to healthy non-athletic controls. The cardiovascular benefits of daily exercise are well recognized. However, endurance athletes appear to develop atrial arrhythmias at higher rates compared to the general population, with an estimated 5–10 fold increase the prevalence of AF amongst endurance athletes.9., 10., 11., 12.,17 While there are speculations

Conclusion

Our study describes and characterizes fibrotic changes within the LA of highly trained endurance athletes. We have shown that in otherwise healthy participants, with no history of arrhythmia, endurance training is associated with a higher level of atrial fibrosis as compared to age and gender matched controls. Atrial fibrosis seen in this population could be an early indicator for those athletes at highest risk for arrhythmia development. Future longitudinal studies should focus on

Acknowledgements

We wish to thank the additional members of the Comprehensive Arrhythmia Research & Management Center (CARMA) at the University of Utah for their support and expertise in performing and analyzing each research scan.

Funding

Comprehensive Arrhythmia Research & Management Center (CARMA) at the University of Utah Cardiology Department, Salt Lake City, Utah.

Declaration of competing interest

There are no pertinent relationships with industry.

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