Rupture of the right atrium secondary to blunt cardiac injury.

Occult cardiac injury following blunt trauma is underestimated in frequency of occurrence. Recent reports indicate that it rivals thoracic aortic transection as the cause of death following traffic fatalities. The most common mechanisms include rapid cardiac rotation while the great vessels remain fixed, transfer of hydraulic pressure from the abdomen or extremities, and direct myocardial compression by the sternum. Presentation can be diverse and findings can include jugular venous distention, upper extremity cyanosis, unexplained hypotension, and muffled heart sounds. An enlarged cardiac silhouette is occasionally seen on roentgenographic evaluation. A surprisingly large number of these patients are noted to have no significant signs of external thoracic trauma. Possible mechanisms include rapid rotation and deceleration of the heart with fixation of the great vessels, transmission of a large venous pressure wave to the heart following abdominal or extremity compression, and direct compression of the heart by the sternum. Following prompt diagnosis and rapid surgical intervention, a large number of these patients can be expected to survive this otherwise fatal injury.