LMW heparin effective for pulmonary embolus

Question Is low molecular weight heparin (LMWH) as effective as adjusted dose heparin in treating pulmonary embolism?

Synopsis Although LMWH is commonly used to treat deep vein thrombosis, some clinicians ask whether similar effectiveness has been shown for pulmonary embolism. The reviewers conducting this meta-analysis identified 12 studies including a total of 1951 patients by searching Medline, Embase, the Cochrane Library databases, and conference proceedings, and by contacting individual researchers and pharmaceutical companies. Two researchers independently reviewed the studies to determine their suitability for inclusion and extracted the data. They evaluated the studies for validity, finding that randomisation and allocation concealment were proper in all studies, with 90% or greater follow up in all the studies. There was homogeneity for all outcomes and no evidence of publication bias. The studies compared fixed dose, subcutaneously administered LMWH with intravenous, adjusted dose unfractionated heparin in patients with symptomatic or asymptomatic pulmonary embolism found in conjunction with a symptomatic deep vein thrombosis. Mortality due to any cause was similar in patients treated with either heparin, though the number of deaths was low (1.2% v 1.4%), which is good for patients but makes it difficult for us to find a difference if one truly exists. Symptomatic venous thromboembolism (pulmonary embolism or deep vein thrombosis) rates at the end of heparin treatment were similar: 1.4% v 2.4%, and there was no difference in the rates of venous thromboembolism in patients with symptomatic or with asymptomatic pulmonary embolism. At three months there also was no difference in thromboembolism rates. Rates of bleeding (major and minor bleeds) were similar with the two treatments. There was no evidence that any LMWH was better than any other in terms of efficacy or safety.

Bottom line Low molecular weight heparin is as effective as adjusted dose, unfractionated heparin in treating symptomatic or asymptomatic pulmonary embolism in patients with a symptomatic deep vein thrombosis. Rates of bleeding are similar.

Level of evidence 1a (www.infopoems.com/levels.html). Systematic reviews (with homogeneity) of randomised controlled trials.