Abstract
A 47-year-old man presented with a recurrent refractory bloody pericardial effusion. Based on the preoperative imaging and pericardiocentesis results with negative cytology, we concluded that blood from a coronary fistula caused the repeated cardiac tamponade. However, pathological findings of the right atrial tissue confirmed primary cardiac angiosarcoma. In this report, we present a unique case as it involves a preoperatively or intraoperatively undetected tumour and a primary cardiac angiosarcoma that induced a fatal outcome, emphasizing the importance of early therapeutic intervention.