Elite endurance athletes had a markedly higher prevalence and incidence of atrial fibrillation (AFib) despite having a favorable cardiovascular risk factor profile compared with controls, according to a study published June 25 in the European Heart Journal. Data suggest that genetic susceptibility and exercise-induced cardiac remodeling contributed to AFib in these former world class rowers.

Michael Darragh Flannery, MBBCH, et al., compared former rowers aged 45-80 years old who competed at international championships with a control group from the UK Biobank (matched 1:100 for age and sex) over a four-year period to assess whether AFib in endurance athletes is due to exercise burden or genetic predisposition. The mean age of the 121 former elite rowers recruited was 62 years, 74% were men and all were White. Evaluation included 12-lead and Holter electrocardiograms, cardiac magnetic resonance imaging (CMR), and genetic analyses including rare variant evaluation and derivation of a validated [AFib] polygenic risk score ([AFib]-PRS).

The primary outcome was prevalence of AFib in both groups, and secondary outcomes were incident AFib, high AFib-PRS, prevalence of AFib risk factors and cardiac volumes on CMR.

Results showed the primary outcome was significantly higher among the former rowers than the controls (22% [26 of 121] vs. 3% [364 of 11,495]. However, the proportion of women with prevalent AFib was similar among the athletes and controls (3% and 4% respectively).

Incident AFib over a four-year follow-up was greater in athletes (6%) compared with controls (2%). Furthermore, athletes demonstrated greater structural and electrophysiological remodeling, had similar cardiovascular risk profiles, and a higher stroke prevalence compared with controls.

"...former endurance athletes represent a unique population in which the rate of [AFib] is comparable to other patient groups in which screening for [AFib] may be considered," write the authors. "Contrary to contemporary recommendations, genetic testing to identify variants associated with inherited cardiomyopathies appears to be of low yield. Our data suggest that background genetic variation may be a relatively more important determinant of [AFib] risk."