The most serious complication of a deep blood clot in the leg, is the clot breaking off, traveling to the lungs and causing a pulmonary embolism. A pulmonary embolism blocks the main artery of the lung and causes shortness of breath, chest pain, rapid breathing and in severe cases sudden death. A new study challenges the conventional wisdom that pulmonary emboli originate from blood clots in the legs. The study, published in the October issue of the Archives of Surgery, found that 85% of patients with pulmonary emboli, had no evidence of blood clots in their legs (deep vein thrombosis). The researchers evaluated the medical records of 247 trauma patients over a three year period. Forty-six patients were diagnosed with a pulmonary embolism, but only 7 patients with pulmonary emboli were also diagnosed with a deep vein thrombosis. The findings imply that pulmonary emboli may originate in the lungs and these findings could change the treatment protocol. Some experts remain skeptical and feel the study has several short comings, including the screening methods used to diagnose DVTs. They emphasize the need for further research.