Medline ® Abstracts for References 38-40

BACKGROUND: Novel oral anticoagulants (NOACs) have been proposed as alternatives to vitamin K antagonists for the prevention of stroke and systemic embolism in patients with atrial fibrillation. Individually, NOACs were at least noninferior to vitamin K antagonists, but a clear superiority in overall and vascular mortality was not consistently proven.

METHODS AND RESULTS: We performed a meta-analysis of phase II and phase III randomized, controlled trials comparing NOACs with vitamin K antagonists in patients with atrial fibrillation. The MEDLINE and EMBASE databases, supplemented with conference abstract books and www.clinicaltrials.gov, were searched up to the first week of July 2012 with no language restriction. Two reviewers performed independent article review and study quality assessment. Data on overall and cardiovascular mortality, stroke or systemic embolism, ischemic stroke, major and intracranial bleeding, and myocardial infarction were collected. NOACs were pooled to perform a comparison with vitamin K antagonists, calculating pooled relative risks (RRs) and associated 95% confidence intervals (CIs). We retrieved 12 studies (3 administering dabigatran, 4 administering rivaroxaban, 2 administering apixaban, and 3 administering edoxaban) enrolling a total of 54 875 patients. NOACs significantly reduced total mortality (5.61% versus 6.02%; RR, 0.89; 95% CI, 0.83-0.96), cardiovascular mortality (3.45% versus 3.65%; RR, 0.89; 95% CI, 0.82-0.98), and stroke/systemic embolism (2.40% versus 3.13%; RR, 0.77; 95% CI, 0.70-0.86). There was a trend toward reduced major bleeding (RR, 0.86; 95% CI, 0.72-1.02) with a significant reduction of intracranial hemorrhage (RR, 0.46; 95% CI, 0.39-0.56). No difference in myocardial infarction was observed.

CONCLUSIONS: NOACs are associated with an overall clinical benefit compared with vitamin K antagonists. Additional research is required to confirm these findings outside the context of randomized trials.

BACKGROUND: New oral anticoagulants (NOACs), including direct thrombin inhibitors (DTIs) and factor Xa (FXa) inhibitors, are emerging alternatives for prophylaxis and treatment of atrial fibrillation (AF) and venous thromboembolism (VTE).

PURPOSE: To compare the benefits and harms of NOACs versus warfarin for AF and VTE.

DATA SOURCES: MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews from January 2001 through July 2012; U.S. Food and Drug Administration (FDA) database for adverse event reports.

STUDY SELECTION: English-language, randomized, controlled trials (RCTs) comparing NOACs with warfarin for management of AF or VTE and observational studies and FDA reports on adverse effects.

DATA EXTRACTION: Two independent reviewers abstracted data and rated study quality and strength of evidence.

DATA SYNTHESIS: Six good-quality RCTs compared NOACs (2 DTI studies, 4 FXa inhibitor studies) with warfarin. In AF, NOACs decreased all-cause mortality (risk ratio [RR], 0.88 [95% CI, 0.82 to 0.96]); in VTE, NOACs did not differ for mortality or VTE outcomes. Across indications, adverse effects of NOACs compared with warfarin were fatal bleeding (RR, 0.60 [CI, 0.46 to 0.77]), major bleeding (RR, 0.80 [CI, 0.63 to 1.01]), gastrointestinal bleeding (RR, 1.30 [CI, 0.97 to 1.73]), and discontinuation due to adverse events (RR, 1.23 [CI, 1.05 to 1.44]). Subgroup analyses suggest a higher risk for myocardial infarction with DTIs than with FXa inhibitors. Bleeding risk for NOACs may be increased in persons older than 75 years or those receiving warfarin who have good control.

LIMITATION: There were no head-to-head comparisons of NOACs and limited data on harms.

CONCLUSION: New oral anticoagulants are a viable option for patients receiving long-term anticoagulation. Treatment benefits compared with warfarin are small and vary depending on the control achieved by warfarin treatment.

PRIMARY FUNDING SOURCE: Department of Veterans Affairs.

BACKGROUND AND PURPOSE: To assess whether the combined analysis of all phase III trials of nonvitamin-K-antagonist (non-VKA) oral anticoagulants in patients with atrial fibrillation and previous stroke or transient ischemic attack shows a significant difference in efficacy or safety compared with warfarin.

METHODS: We searched PubMed until May 31, 2012, for randomized clinical trials using the following search items: atrial fibrillation, anticoagulation, warfarin, and previous stroke or transient ischemic attack. Studies had to be phase III trials in atrial fibrillation patients comparing warfarin with a non-VKA currently on the market or with the intention to be brought to the market in North America or Europe. Analysis was performed on intention-to-treat basis. A fixed-effects model was used as more appropriate than a random-effects model when combining a small number of studies.

RESULTS: Among 47 potentially eligible articles, 3 were included in the meta-analysis. In 14 527 patients, non-VKAs were associated with a significant reduction of stroke/systemic embolism (odds ratios, 0.85 [95% CI, 074-0.99]; relative risk reduction, 14%; absolute risk reduction, 0.7%; number needed to treat, 134 over 1.8-2.0 years) compared with warfarin. Non-VKAs were also associated with a significant reduction of major bleeding compared with warfarin (odds ratios, 0.86 [95% CI, 075-0.99]; relative risk reduction, 13%; absolute risk reduction, 0.8%; number needed to treat, 125), mainly driven by the significant reduction of hemorrhagic stroke (odds ratios, 0.44 [95% CI, 032-0.62]; relative risk reduction, 57.9%; absolute risk reduction, 0.7%; number needed to treat, 139).

CONCLUSIONS: In the context of the significant limitations of combining the results of disparate trials of different agents, non-VKAs seem to be associated with a significant reduction in rates of stroke or systemic embolism, hemorrhagic stroke, and major bleeding when compared with warfarin in patients with previous stroke or transient ischemic attack.