An Unexpected Cause of Marathon Dyspnea: A Diagnostic Challenge in an Amateur Athlete

Challenging differential diagnosis Background:Above-average exercise capacity and a high threshold for symptoms such as dyspnea or chest pain in athletes can create false reassurance regarding the absence of clinically significant coronary artery disease (CAD).The aim of this report is to present the diagnostic reasoning and therapeutic management of an amateur endurance athlete who developed exertional dyspnea during a marathon run. Case Report:A 50-year-old man who was an amateur long-distance runner with a history of hypertension, hyperlipidemia reported recurrent exertional dyspnea with the onset approximately at the 20 th kilometer of a marathon run, forcing a short rest but not preventing completion.Cardiopulmonary exercise testing (CPET) showed normal exercise capacity (peak oxygen uptake of 34 ml/min/kg, 104% of the predicted value).No dyspnea or chest pain occurred during maximal exertion, although ECG showed 1-to 2-mm ST-segment depression and T-wave changes in leads II, III, aVF, V5, and V6.Coronary computed tomography angiography (CCTA) showed a circumferential non-calcified plaque in the left anterior descending (LAD) artery, suggesting spontaneous coronary artery dissection.Coronary angiography confirmed severe left anterior descending artery (LAD) disease with 80% stenosis in segment 6 and a critical lesion in segment 7. Two drug-eluting stents were implanted into the LAD during a single procedure. Conclusions:Firstly, supranormal exercise capacity and mildness of symptoms in endurance athletes can mask advanced CAD.Secondly, electrically positive CPET findings (1-2 mm ST-segment depression) warrant further anatomical assessment even in patients with low risk factor-weighted clinical likelihood.Finally, CCTA should be considered early in athletes with new-onset exertional symptoms, as it can reveal significant stenosis.