Authors present the case of little patient with the dissection, pseudoaneurysm and finally a rupture of the interventricular septum after the blunt thracic injury. The patient was smitten as a pedestrian by a car and during the whole period of her stay in the hospital she was showing signs of circulatory instability. Due to the current intraabdominal injuries this circulatory decompensation was first assigned to hemoperitoneum, for which the girl was operated on about 3 hours after admission. Nevertheless, even after the abdminal cavity check, after the treatment of supreficial liver lacerations and intensive volume resuscitation the patient showed signs of insufficiency. Diagnosis was finally determined on the base of the transthoracic echocardiography (TTE), which proved the traumatic rupture of interventricular septum. The operation followed correcting the defect, which was performed with a good result according to the TTE postoperatively. Nevertheless, 27 hours after the admission the patient died due to the electromechanical dissociation. In the discussion the authors then evoke a number of papers concerning the same topic.