What is the clinical evidence from this study?

Study design: Meta-Analysis. Population: Non-valvular atrial fibrillation (n=963). Intervention: Aspirin vs. Low-intensity anticoagulation (Vitamin K antagonists). Primary outcome: Combination of ischemic stroke or systemic embolism (OR 0.94, 95% CI 0.57-1.56).

What does this research mean for the field?

In patients with non-valvular atrial fibrillation, aspirin does not reduce the incidence of ischemic stroke or systemic embolism compared to low-intensity anticoagulation, but significantly increases all-cause mortality. Novelty: ClaimNovelty.SYNTHESIS. Consensus alignment: ConsensusAlignment.SUPPORTS_CONSENSUS.

November 12, 2015Open Access

Aspirin Compared to Low Intensity Anticoagulation in Patients with Non-Valvular Atrial Fibrillation. A Systematic Review and Meta-Analysis

Key Result

In patients with non-valvular atrial fibrillation, aspirin did not reduce the incidence of ischemic stroke or systemic embolism compared to low-intensity anticoagulation (OR 0.94), but significantly increased all-cause mortality.

Study Design

Type

Meta-Analysis (n=963)

Blinding

Open-label

Multicenter

Yes

Structured PICO

Does aspirin reduce ischemic stroke or systemic embolism in patients with non-valvular atrial fibrillation compared to low-intensity anticoagulation?

Population

Patients with non-valvular atrial fibrillation (pooled from 3 RCTs)

Intervention

Aspirin

Comparator

Low-intensity anticoagulation with Vitamin K antagonists

Outcome

Combination of ischemic stroke or systemic embolismcomposite

In patients with non-valvular atrial fibrillation, aspirin provides no benefit over low-intensity anticoagulation for stroke prevention and is associated with increased all-cause mortality.

Main Result

Effect estimate: OR 0.94 (95% CI 0.57-1.56)

Limitations

Most of the studies included were terminated before completion, reducing power to detect meaningful differences.
Most of the studies included a low risk population with non-valvular atrial fibrillation.
All but one of the studies were conducted more than 20 years ago.
Could not investigate in depth the reasons for the difference in all-cause mortality due to unknown causes of death in a significant portion of patients.

Abstract

BACKGROUND: Despite its lack of efficacy, aspirin is commonly used for stroke prevention in atrial fibrillation. Since prior studies have suggested a benefit of low-intensity anticoagulation over aspirin in the prevention of vascular events, the aim of this systematic review was to compare the outcomes of patients with non-valvular atrial fibrillation treated with low-intensity anticoagulation with Vitamin K antagonists or aspirin. METHODS: We conducted a systematic review searching Ovid MEDLINE, Embase and the Cochrane Central Register of Controlled Trials, from 1946 to October 14th, 2015. Randomized controlled trials were included if they reported the outcomes of patients with non-valvular atrial fibrillation treated with a low-intensity anticoagulation compared to patients treated with aspirin. The primary outcome was a combination of ischemic stroke or systemic embolism. The random-effects model odds ratio was used as the outcome measure. RESULTS: Our initial search identified 6309relevant articles of which three satisfied our inclusion criteria and were included. Compared to low-intensity anticoagulation, aspirin alone did not reduce the incidence of ischemic stroke or systemic embolism OR 0.94 (95% CI 0.57-1.56), major bleeding OR 1.06 (95% CI 0.42-2.62) or vascular death OR 1.04 (95% CI 0.61-1.75). The use of aspirin was associated with a significant increase in all-cause mortality OR 1.66 (95% CI 1.12-2.48). CONCLUSION: In patients with non-valvular atrial fibrillation, aspirin provides no benefits over low-intensity anticoagulation. Furthermore, the use of aspirin appears to be associated with an increased risk in all-cause mortality. Our study provides more evidence against the use aspirin in patients with non-valvular atrial fibrillation.

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