A 43-year-old Caucasian German woman wearing a three-point seatbelt and holding her two-year-old boy in her arms in the front passenger seat of a car was involved in a head-on collision with a tree (Figure 1). When the emergency team arrived at the scene of the accident, the car cabin was slightly deformed, the driver and passenger had their seat belts on, and both airbags were not deployed. The driver had some minor injuries and was transported to another hospital; the patient and her son were transported to the emergency room at a level-1 trauma hospital secondary to complaints of thoracic pain and lower limb pain, respectively. No visible evidence of trauma including a seat belt sign was noted on the chest of the women or the child's head. 
They presented to the emergency department at our trauma hospital one hour and ten minutes after the accident. On admission, the mother was alert (Glasgow Coma Scale 15) and hemodynamically stable (blood pressure 120/70mmHg; 84 pulses/minute). The usual clinical examination was conducted following Advanced Trauma Life Support principles. The trauma surgeon performing the Focused Assessment with Sonography for Trauma did not detect any free intraperitoneal fluid. The initial radiological assessment (chest, pelvic and cervical spine X-ray) showed the clinically evident pectus excavatum, multiple rib fractures and a stable, not dislocated, pelvic fracture. Fifteen minutes after admission she was transported alert and in a cardiopulmonary stable state to the computed tomography (CT) scanner. The CT scan demonstrated a zygomatic fracture, three-cm pericardial effusion (Figure 2), fractures of the 2nd and 3rd ribs, and a pelvic type C fracture. 
Two hours after the trauma, the patient became hemodynamically unstable (blood pressure 70/40mmHg; 122 pulses/minute). Her hemoglobin level was 9.5g/dL (on admission 10.4g/dL) and the pH 7.27 (Additional file 1: Table S1). The trauma surgeon immediately performed a pericardiocentesis with insertion of a pigtail catheter to temporarily stabilize the patient and bridge the time until surgery. Intubation and central vein and artery catheterization followed immediately. The on-call cardiovascular surgeon began the surgery four hours after the trauma.
Intraoperatively, a combined one-cm laceration of the left atrium and right ventricle was noted (Figure 3). These were repaired with a running suture technique. The patient was successfully extubated seven days after surgery.