Chest trauma can be complicated, among others, with cardiac tamponade. This life-threatening condition should be treated promptly and adequately to assure a positive outcome. During the rapid events that take place in the emergency room with the arrival of a polytrauma patient, anamnestic data are not always available, especially if dealing with a non-cooperative, unaccompained traumatized patient. The following case report describes our experience with a chest trauma patient after a vehicle accident, who was admitted to our ward exhibiting a constellation of signs compatible with a cardiac tamponade. The only demonstrable objective signs included distended mediastinum and heart shadow on the chest X ray and muffled heart sounds. However, despite the impressive clinical picture, the patient continued to exhibit constant, though low blood pressure measurements and after a short period of observation, given the homodynamic stability, it was decided against pericardiocenthesis. The "secret" of our patient was finally discovered at angiography, when a left subclavian steal was diagnosed. The literature in this matter is discussed, stressing the importance of anamnestic data in the trauma patient. Most importantly, we address the significance of relying on hard clinical data (homodynamic stability) rather than on isolated signs (widened mediastinum/heart shadow) to reach as accurate a diagnosis as possible before pursuing invasive, usually not-innocuous procedures (pericardiocenthesis).