Estimating Vitamin K Antagonist Anticoagulation Benefit in People With Atrial Fibrillation Accounting for Competing...

Area of Science:

• Cardiology
• Clinical Trials
• Pharmacology

Background:

• Atrial fibrillation (AF) patients face high mortality, partly from non-vascular causes.
• The competing risk of death can diminish the perceived benefit of anticoagulation.
• Assessing anticoagulant efficacy requires accounting for competing risks.

Purpose of the Study:

• To evaluate if competing risks materially impact the estimated anticoagulant benefit in AF patients.
• To compare the guideline-endorsed CHA2DS2-VASc model with a competing risk model for estimating VKA benefit.

Main Methods:

• Secondary analysis of 12 randomized controlled trials involving AF patients treated with VKAs versus placebo or antiplatelets.
• Estimated absolute risk reduction (ARR) of VKAs for stroke/systemic embolism using CHA2DS2-VASc and a competing risk model.
• Compared benefit estimates based on varying life expectancies.

Main Results:

• The CHA2DS2-VASc model overestimated VKA's ARR compared to the competing risk model (median 3-year ARR: 6.9% vs. 5.2%).
• Benefit overestimation by CHA2DS2-VASc was more pronounced in patients with lower life expectancies.
• For lowest decile life expectancy, the 3-year ARR difference was 4.7%; for highest decile, it was -1.3%.

Conclusions:

• Vitamin K antagonist (VKA) anticoagulants are highly effective in reducing stroke risk in AF.
• The CHA2DS2-VASc model overestimates VKA benefits by not accounting for competing risks and nonlinear benefit.
• Benefit overestimation is greatest with shorter life expectancies and longer estimation horizons.