Abstract
BACKGROUND: Differentiating arrhythmogenic cardiomyopathy (ACM) from healed viral myocarditis in competitive athletes is challenging, particularly as advanced imaging increasingly detects myocardial abnormalities in asymptomatic individuals. CASE SUMMARY: A 26-year-old professional football player was found to have lateral and inferior T-wave inversions during preseason screening. He was asymptomatic with normal biomarkers and excellent exercise capacity. Cardiac magnetic resonance demonstrated left ventricular enlargement with mildly reduced systolic function and 2 discrete regions of nonischemic replacement fibrosis without active inflammation. Ambulatory monitoring showed a very low ectopic burden without ventricular arrhythmias, and comprehensive cardiomyopathy genetic testing was negative. Multidisciplinary shared decision-making supported conditional clearance with ongoing surveillance and emergency preparedness. DISCUSSION: This case highlights diagnostic uncertainty between ACM and postinflammatory scar, underscoring the necessity of contextual imaging interpretation and nuanced multimodal evaluation. TAKE-HOME MESSAGES: Distinguishing healed myocarditis from ACM in competitive athletes remains a significant diagnostic challenge, particularly when cardiac magnetic resonance demonstrates nonischemic myocardial fibrosis in otherwise asymptomatic individuals. Multimodality evaluation, longitudinal follow-up, and shared decision-making are essential to establish the correct diagnosis, guide risk stratification, and inform safe return-to-play decisions.