A 72-year-old male veteran amateur runner in apparent good health presented to our Center of Sports Cardiology for a medical checkup. He reported that his heart rate monitor detected sudden increases in heart rate during a regular, non-demanding running pace while also complaining of a general sense of fatigue. The athlete had previous medical examinations carried out for the eligibility to practice competitive athletics. He was taking antihypertensive drugs, including nebivolol, to control a form of uncomplicated arterial hypertension. The objective examination was regular, and so was the resting electrocardiogram (Figure 1). Then, the athlete proceeded to the cycle-ergometer exercise stress test. During the stress test, at the second step corresponding to 100 watts of external load, atrial fibrillation with high ventricular response started (Figure 2), which continued for over 20 minutes after stopping the stress test. The ECG showed clear signs of ventricular repolarization abnormalities, i.e., ST-segment depression by more than 2 mm with a horizontal and descending pattern on the inferior and precordial leads from V3 to V6. The athlete remained in an upright sitting position, hemodynamic stable (normal blood pressure) without chest pain or tachycardia symptoms. The athlete assumed 165 mg acetylsalicylic acid and 20 drops of Diazepam. After that, the athlete was accompanied in stable conditions walking autonomously to the emergency department for monitoring and cardiac examination. At the ED, the ECG resulted in the normal range, restoring normal sinus rhythm. The consultant cardiologist recommended only therapy with bisoprolol 2.5 mg (bis in die) plus Ramipril 5 mg per day and Xarelto 150 mg (bis in die). He also planned echo stress after a few months and suggested a consultation for transcatheter catheter ablation. However, the athlete moved on to the cath lab for coronary angiography, as we were sure of the coexistence of a critical multi-vessel coronary artery disease. Indeed, the coronary angiography showed a multi-vessel CAD(Figure 3) treated first with angioplasty for Ostial D1 significant stenosis. Also, the athlete underwent angioplasty plus DES implantation for the obstruction of the proximal CX coronary artery. Only moderate stenosis on the mid-IVA plus critical distal stenosis did not have any revascularization procedure. The athlete remained in good condition.