Superior vena cava syndrome is an uncommon complication of open heart surgery. While both cardiac tamponade and superior vena cava syndrome may present as elevated central venous pressure accompanied by decreased mean arterial pressure and cardiac output, the presence of upper body cyanosis is unusual with tamponade. We report the diagnosis and successful emergency treatment of a patient with acute superior vena cava syndrome and dyspnea apparently caused by a pericardial hematoma developing after aortic valve replacement and coronary artery bypass grafting.