Although most patients suffering from a coronary artery fistula remain asymptomatic during childhood and adolescence, many of them develop complications in adulthood due to volume overload, endocarditis or ischemia. Here we present a young woman surviving a sudden cardiac death due to myocardial ischemia with subsequent ventricular fibrillation caused by thrombosis of a coronary artery fistula deriving from the left main coronary artery. Parts of the thrombus had been embolized into the circumflex artery causing posterior myocardial infarction. The thrombosis might have been initiated by local compression from a round extracardiac mass of 3 cm with liquid and solid content located between the vena cava superior and the ascending aorta. This structure was suspected to be a hematoma which had been caused by a blunt thoracic trauma while playing soccer 2 weeks before.