A 27-year-old man was hospitalized in severe condition 50 minutes after receiving a penetrating wound to the left side of the chest. Objectively the patient is in a stupor, his skin is pale and acrocyanotic. Pulse is 120/min., of poor volume, weak. Blood pressure is 80/40 mm Hg. Heart sounds are muffled, cardiac borders are markedly expanded. In the III intercostal area along the parasternal line on the left there is a stab-incised wound. Plain chest X-ray shows enlarged heart shadow with smoothed out waist of the heart, there is hemothorax on the left to the 5th rib. What contributes the most to the severity of the patient’s condition?