Introduction: An association between higher exercise volume and the presence of myocardial fibrosis has been reported, adding to speculation that endurance sport may promote an arrythmogenic substrate and adverse cardiac outcomes. While recent data suggest no association between lifelong exercise and focal cardiac fibrosis using late gadolinium enhancement (LGE) MRI, the presence of diffuse fibrosis in older athletes is unclear. This study sought to examine the associations among myocardial T1, extracellular volume fraction (ECV) and lifelong exercise in athletes.
Hypothesis: A greater lifetime hours of vigorous exercise would be associated with higher T1 values and ECV fraction in athletes.
Methods: Healthy adults (>10 years of physical activity) completed a graded exercise test, physical activity questionnaire, and cardiac MRI protocol (3.0T scanner with gadolinium contrast MOLLI for T1 mapping). Myocardial T1 and extracellular volume (ECV) were measured by a single reader blinded to clinical data using commercially-available software (CVi42).
Results: Demographics, cardiac morphology, and T1 mapping data are summarized (Table 1). Among all participants, lifetime hours of vigorous exercise (r=0.15, p=0.36) and VO2max (r=0.18, p=0.28) were not associated with ECV fraction, while a higher VO2max was associated with a lower T1 native value (r=-0.45, p<0.005). These data were supported by low intra-reliability ECV measurement bias (n=15, mean bias with CI: -0.4[-3.6,2.8], p=0.34) and strong correlation (r=0.99, p<0.0001).
Conclusions: These data do not support a direct link between exercise volume and diffuse fibrosis in athletes. The higher post-contrast T1 values in athletes may reflect different remodeling patterns and warrants investigation. T1 mapping should be explored further in athletes with cardiac remodeling as a method for distinguishing between physiological adaptation and pathology where differentiation remains inconclusive.