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Study Challenges Association Between Pulmonary Embolism and DVT
CHICAGO -- October 19, 2009 -- Few trauma patients who develop pulmonary embolism also have deep venous thrombosis, challenging commonly held beliefs about the association between the two conditions, according to a study published in the October issue of Archives of Surgery.
"For decades, it has been taught that pulmonary embolism is a sequel of deep venous thrombosis," the authors wrote. "Forming in the lower extremity or pelvic veins, clots break off and travel to the pulmonary circulation. Therefore, deep venous thrombosis and pulmonary embolism should coexist in most patients, because part of the clot embolises in the lung, and part remains attached to the vein."
George C. Velmahos, MD, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, and colleagues studied 247 trauma patients who underwent imaging scans of the lungs and the veins in the pelvis and legs between 2004 and 2006. Demographic information, as well as data on injury type and severity, imaging findings, hospital length of stay and death rates, was collected.
Among the 247 patients, 46 (19%) were diagnosed with pulmonary embolism and 18 (7%) had deep venous thrombosis. Seven patients with pulmonary embolism (15%) also had deep venous thrombosis. There were no differences between patients with pulmonary embolism who did and did not have deep venous thrombosis in any of the demographic or clinical variables assessed.
"Based on these data, there is little evidence that pulmonary embolism originates from deep venous thrombosis of peripheral veins," the authors concluded.
Among the potential explanations for the lack of association are that clots formed in the legs and pelvis completely dislodge when they travel to the lungs; therefore, no evidence of deep venous thrombosis would remain in patients with pulmonary embolism.
However, studies on cadavers have shown that typically only part of the clot breaks off and lodges elsewhere.
"We propose that many pulmonary embolisms form primarily in the lungs and that the risk-benefit ratio of vena cava filters should be reconsidered," they wrote. "As computed tomographic venography becomes more popular and accurate, this issue will be further explored, and it may be revealed that we have been preaching and practicing the wrong dogma for years."
SOURCE: Archives of Surgery
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