Purpose This study aimed to compare the prevalence of myocardial fibrosis and coronary calcification in individuals who have performed very high levels of strenuous endurance exercise (SEE; former male professional cyclists) and sex/age-matched controls. Methods We used a retrospective cohort study design, where cases were former finishers of =1 Grand Tour (Tour de France, Giro d` Italia or Vuelta a España) and controls were untrained individuals free of cardiovascular risk. All participants underwent cardiac magnetic resonance and cardiac computer tomography in the same center during years 2020-2021 to detect myocardial fibrosis (late gadolinium enhancement) and to quantify coronary calcium, respectively. Results Twenty-three cases (age, 46 ± 6 yr) and 59 controls (47 ± 7 yr) were studied. Fibrotic patches were evidenced only in the left ventricle, with a higher prevalence in cases (23% vs 2% in controls, P = 0.006). However, fibrotic tissue was nonischemic and of low extension (0.6% ± 0.4% of left ventricle mass), and no significant differences were found between cases and controls for native T1 or T2 values. No between-group differences were found for coronary calcium indicators, including Agatston or density scores. Subanalyses revealed no differences attending to whether cases were still performing regular SEE (n = 8) or not (n = 15) after professional retirement. Conclusions Although former professional cyclists seemed to show a greater prevalence of myocardial fibrosis, the extension of fibrotic tissue was minimal and no alterations were found in coronary calcification indicators. While keeping in mind the low sample size of the cases` group, our results do not support evidence for major cardiac maladaptations with long-term exposure to SEE, at least in middle-age adults.
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