Severe Left Ventricular Dilation With Preserved Contractile Reserve in an Adolescent Elite Athlete

Distinguishing physiologic athletic remodeling from early cardiomyopathy is particularly challenging when structural abnormalities coexist with elite functional performance and electrical instability.

An 18-year-old competitive male basketball athlete presented with exertional palpitations and atrial fibrillation. Multimodality cardiovascular evaluation demonstrated severe left ventricular dilation (indexed end-diastolic volume: 156 mL/m²) with moderately reduced systolic function (left ventricular ejection fraction: 35% to 40%) and supraphysiologic tissue Doppler diastolic velocities. Cardiac magnetic resonance confirmed marked ventricular dilation without late gadolinium enhancement. Stress echocardiography demonstrated augmentation of ejection fraction to 65% to 70%, and cardiopulmonary exercise testing confirmed elite aerobic capacity (peak VO₂: 52.5 mL/kg/min) without inducible arrhythmias.

This case highlights the physiologic-pathologic overlap between athlete's heart and early nonischemic cardiomyopathy complicated by electrical instability.

Elite performance does not exclude cardiomyopathy. Return-to-play decisions in gray-zone phenotypes require shared decision-making, multidisciplinary input, and robust emergency action planning.