We describe an acute myocardial infarction in a young athlete with non-obstructive hypertrophic cardiomyopathy (HCM) and normal coronary arteries. A 18 year old athlete came to our attention for dispnoea and chest pain during effort. Echocardiography showed non-obstructive HCM, with restrictive physiology. Cardiac catheterization and coronary angiography showed elevated pulmonary artery pressure and normal coronary arteries. He was discharged on sotalol and diuretics. Nine months later, he was resuscitated from a cardiac arrest during mild effort. The ECG revealed a high rate of atrial fibrillation with significant ST-T changes, and echocardiography an akinesia of interventricular septum. Cardiac enzymes were elevated. The coronary angiogram showed normal coronary arteries. This case is important as a reminder that acute myocardial infarction is not only due to coronary artery disease, and that atrial fibrillation may represent a trigger of serious cardiovascular events in patients with HCM.