Vitamin K antagonists or low-molecular-weight heparin for the long term treatment of symptomatic venous thromboembolism.
BACKGROUND
People with venous thromboembolism (VTE) are generally treated for five days with intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin (LMWH) followed by three months of vitamin K antagonist treatment. Treatment with vitamin K antagonists requires regular laboratory measurements and some patients have contraindications to treatment. This is an update of a review first published in 2000 and updated in 2002.


OBJECTIVE
To evaluate the efficacy and safety of long term treatment of VTE with LMWH compared to vitamin K antagonists.


METHODS
For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched their Specialised Register (last searched February 2012) and CENTRAL (2012, Issue 1).


METHODS
Two authors evaluated trials independently for methodological quality.


METHODS
The review authors extracted data independently. Primary analysis included all trial participants randomised to the allocated treatment groups. Separate analyses were performed according to the quality of the trials and for subgroups such as trials initially using similar treatments in both trial arms and those that did not, trials concerning deep vein thrombosis (DVT) and pulmonary embolism (PE) and the different periods of follow-up.


RESULTS
All 15 trials, with a combined total of 3197 patients, fulfilling our criteria were combined in a meta-analysis. We found a non-statistically significant reduction in the risk of recurrent VTE between the two treatments (odds ratio (OR) 0.82, 95% CI 0.59 to 1.13). Analysis of pooled data for category I trials (those with a high methodological quality) showed a non-significant reduction in the odds of recurrent VTE favouring LMWH treatment (OR 0.80, 95% CI 0.54 to 1.18).For all trials combined, the difference in bleeding significantly favoured treatment with LMWH (OR 0.50, 95% CI 0.31 to 0.79). Considering only category I trials, a non-significant trend favouring LMWH remained (OR 0.62, 95% CI 0.36 to 1.07). No difference was observed in mortality (OR 1.06, 95% CI 0.74 to 1.54).


CONCLUSIONS
LMWHs are possibly as effective as vitamin K antagonists in preventing symptomatic VTE after an episode of symptomatic deep venous thrombosis, but are much more expensive. Treatment with LMWH is significantly safer than treatment with vitamin K antagonists. LMWH may result in fewer episodes of bleeding and is possibly a safe alternative in some patients, especially those in geographically inaccessible areas, are reluctant to visit the thrombosis service regularly, or with contraindications to vitamin K antagonists. However, treatment with vitamin K antagonists remains the treatment of choice for the majority of patients.
Department of Vascular Surgery, Freeman Hospital, Newcastle upon Tyne, UK. alinaro@hotmail.com.
Alina
A
Andras
Adriano
A
Sala Tenna
Fay
F
Crawford
D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use*; D006470:Hemorrhage / Q000139:chemically induced; D006495:Heparin, Low-Molecular-Weight / Q000009:adverse effects / Q000627:therapeutic use*; D006801:Humans; D016017:Odds Ratio; D016032:Randomized Controlled Trials as Topic; D054556:Venous Thromboembolism / Q000188:drug therapy* / Q000401:mortality; D020246:Venous Thrombosis / Q000188:drug therapy; D014812:Vitamin K / Q000037:antagonists & inhibitors*
D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight; D014812:Vitamin K