Comparison of efficacy and safety of low molecular weight heparins and unfractionated heparin in initial treatment of deep venous thrombosis: a meta-analysis.

OBJECTIVE

To compare the efficacy and safety of low molecular weight heparins and unfractionated heparin in the initial treatment of deep venous thrombosis for the reduction of recurrent thromboembolic events, death, extension of thrombus, and haemorrhages.

DESIGN

Meta-analysis of results from 16 randomised controlled clinical studies.

SUBJECTS

2045 patients with established deep venous thrombosis.

INTERVENTION

Treatment with low molecular weight heparins or unfractionated heparin.

MAIN OUTCOME MEASURES

Incidences of thromboembolic events (deep venous thrombosis or pulmonary embolism, or both); major haemorrhages; total mortality; and extension of thrombus.

RESULTS

A significant reduction in the incidence of thrombus extension (common odds ratio 0.51, 95% confidence interval 0.32 to 0.83; P = 0.006) in favour of low molecular weight heparin was observed. Non-significant trends also in favour of the low molecular weight heparins were observed for the recurrence of thromboembolic events (0.66, 0.41 to 1.07; P = 0.09), major haemorrhages (0.65, 0.36 to 1.16; P = 0.15), and total mortality (0.72, 0.46 to 1.4; P = 0.16).

CONCLUSIONS

Low molecular weight heparins seem to have a higher benefit to risk ratio than unfractionated heparin in the treatment of venous thrombosis. These results, however, remain to be confirmed by using clinical outcomes in suitably powered clinical trials.