We present a 45-year-old patient who had to undergo aortocoronary bypass surgery after acute posterior myocardial infarction. On day twelve, the patient suddenly developed the classic signs of cardiogenic shock including angina, tachycardia, and hypotension. ECG displayed significant ST-elevations and troponin T was positive. Echocardiograph, suspected relevant pericardial effussion. However, the typical clinical signs of acute pericardial tamponade (distension Of jugular veins, paradoxical pulse) were absent. Therefore, a computed tomography was carried out, which confirmed an isolated left ventricular tamponade resulting in severe diastolic and systolic dysfunction with profoundly impaired left ventricular filling. Immediate operative drainage was necessary since percutaneous pericardiocentesis was impossible given the untypical localization. This case demonstrates that clearcut signs of myocardial infarction can be misleading and may represent the untypical presentation of left ventricular tamponade, particularly in the setting after open-heart surgery.