Prevention of venous thromboembolism in internal medicine with unfractionated or low-molecular-weight heparins: A meta-analysis of randomised clinical trials

Background The prevention of venous thromboembolic disease is less studied in medical patients than in surgery. Methods. We performed a meta-analysis of randomised trials studying prophylactic unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) in internal medicine, excluding acute m yocardial infarction or ischaemic stroke. Deep vein thrombosis (DVT) system atically detected at the end of the treatment period, clinical pulmonary em bolism (PE), death and major bleeding were recorded. Results. Seven trials comparing a prophylactic heparin treatment to a control (15,095 patients) w ere selected. A significant decrease in DVT and in clinical PE were observe d with heparins as compared to control (risk reductions = 56% and 58% respe ctively, p <0.001 in both casts), without significant difference in the inc idence of major bleedings or deaths. Nine trials comparing LMWH to UFH ( 4, 669 patients) were also included. No significant effect was observed on eit her DVT, clinical PE or mortality. However LMWH reduced by 52% the risk of major haemorrhage (p = 0.049). Conclusions. This meta-analysis, based on th e pooling of data available for several heparins, shows that heparins are b eneficial in the prevention of venous thromboembolism in internal medicine.