Direct thrombin inhibitors versus vitamin K antagonists for preventing cerebral or systemic embolism in people with non-valvular atrial fibrillation.

Abstract

BACKGROUND: Chronic anticoagulation with vitamin K antagonists (VKAs) prevents ischaemic stroke and systemic embolism in people with non-valvular atrial fibrillation (AF) but dose adjustment, coagulation monitoring and bleeding limits its use. Direct thrombin inhibitors (DTIs) are under investigation as potential alternatives.

OBJECTIVES: To assess (1) the comparative efficacy of long-term anticoagulation using DTIs versus VKAs on vascular deaths and ischaemic events in people with non-valvular AF, and (2) the comparative safety of chronic anticoagulation using DTIs versus VKAs on (a) fatal and non-fatal major bleeding events including haemorrhagic strokes, (b) adverse events other than bleeding and ischaemic events that lead to treatment discontinuation and (c) all-cause mortality in people with non-valvular AF.

SEARCH METHODS: We searched the Cochrane Stroke Group Trials Register (July 2013), the Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, May 2013), MEDLINE (1950 to July 2013), EMBASE (1980 to October 2013), LILACS (1982 to October 2013) and trials registers (September 2013). We also searched the websites of clinical trials and pharmaceutical companies and handsearched the reference lists of articles and conference proceedings.

SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing DTIs versus VKAs for prevention of stroke and systemic embolism in people with non-valvular AF.

DATA COLLECTION AND ANALYSIS: All three review authors independently performed data extraction and assessment of risk of bias. Primary analyses compared all DTIs combined versus warfarin. We performed post hoc analyses excluding ximelagatran because this drug was withdrawn from the market owing to safety concerns.

MAIN RESULTS: We included eight studies involving a total of 27,557 participants with non-valvular AF and one or more risk factors for stroke; 26,601 of them were assigned to standard doses groups and included in the primary analysis. The DTIs: dabigatran 110 mg twice daily and 150 mg twice daily (three studies, 12,355 participants), AZD0837 300 mg once per day (two studies, 233 participants) and ximelagatran 36 mg twice per day (three studies, 3726 participants) were compared with the VKA warfarin (10,287 participants). Overall risk of bias and statistical heterogeneity of the studies included were low.The odds of vascular death and ischaemic events were not significantly different between all DTIs and warfarin (odds ratio (OR) 0.94, 95% confidence interval (CI) 0.85 to 1.05). Sensitivity analysis by dose of dabigatran on reduction in ischaemic events and vascular mortality indicated that dabigatran 150 mg twice daily was superior to warfarin although the effect estimate was of borderline statistical significance (OR 0.86, 95% CI 0.75 to 0.99). Sensitivity analyses by other factors did not alter the results. Fatal and non-fatal major bleeding events, including haemorrhagic strokes, were less frequent with the DTIs (OR 0.87, 95% CI 0.78 to 0.97). Adverse events that led to discontinuation of treatment were significantly more frequent with the DTIs (OR 2.18, 95% CI 1.82 to 2.61). All-cause mortality was similar between DTIs and warfarin (OR 0.91, 95% CI 0.83 to 1.01).

AUTHORS' CONCLUSIONS: DTIs were as efficacious as VKAs for the composite outcome of vascular death and ischaemic events and only the dose of dabigatran 150 mg twice daily was found to be superior to warfarin. DTIs were associated with fewer major haemorrhagic events, including haemorrhagic strokes. Adverse events that led to discontinuation of treatment occurred more frequently with the DTIs. We detected no difference in death from all causes.