Four randomised controlled trials and two evidence based clinical practice guidelines were identified comparing low molecular weight heparin (LMWH) with unfractionated heparin (UH) in the management of pulmonary embolism (PE).
The studies included the LMWHs tinzaparin sodium, reviparin sodium and Fragmin and assessed the following outcomes: death, recurrent venous thromboembolism, and risk of major bleeding.
None of the trials reported a significant difference between LMWH and UH for death and risk of major bleeding.
Only one trial reported an increased risk of recurrent venous thromboembolism for the UH group compared to the LMWH group. The other three trials found no significant differences.
Both guidelines recommend replacing UH with LMWH for treatment of pulmonary embolism.
We are unable to reach definitive conclusions regarding the effectiveness of different types of LMWHs.
The studies were of variable quality. One RCT was of very high quality, two were medium quality, and one study was of poor quality.