Myocardial Fibrosis in Athletes: Risk Marker or Physiological Adaptation?

Endurance exercise is widely recognized for its cardiovascular benefits, including improved longevity and metabolic health. However, excessive endurance training may lead to adverse cardiac adaptations, such as myocardial fibrosis, detected via late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR). This review examines the dual role of myocardial fibrosis in athletes-as a potential risk marker for life-threatening arrhythmias or a benign byproduct of physiological remodeling. While moderate exercise promotes beneficial cardiac hypertrophy, ultra-endurance athletes exhibit a 10-20% increase in ventricular size and mass, alongside elevated cardiac biomarkers post-exercise. Myocardial fibrosis, particularly in the left ventricle (LV), is associated with arrhythmias and sudden cardiac death, especially when presenting as a subepicardial/midmyocardial patchy pattern. Studies report that 22% of athletes with this pattern experienced malignant arrhythmias, underscoring its clinical significance. Conversely, fibrosis may also reflect adaptive remodeling in some cases, complicating its interpretation. The mechanisms underlying fibrosis in athletes remain unclear but may involve repeated cardiac stress, inflammation, or distinct atherosclerotic plaque dynamics. CMR is critical for detecting fibrosis, though differentiating pathological from physiological patterns requires careful clinical correlation. Risk stratification must consider LGE patterns, arrhythmia history, and symptoms. Despite concerns, elite athletes generally exhibit increased longevity, highlighting the complex interplay between exercise benefits and risks. Further research is needed to clarify fibrosis mechanisms, refine diagnostic criteria, and guide management strategies to ensure athlete safety while preserving the advantages of endurance training.