Net clinical benefit of adding aspirin to warfarin in patients with atrial fibrillation: Insights from the J-RHYTHM Registry

Background Concomitant use of vitamin K antagonist (VKA) and aspirin (ASA) is becoming increasingly prevalent among atrial fibrillation (AF) patients. We quantified the net clinical benefit of adding ASA to a VKA using nationwide prospective AF registry data. Methods We studied 6074 patients (VKA monotherapy: 83% and VKA + ASA: 17%) between January 2009 and July 2009, and followed them for a mean follow-up period of 2 years. The risk of strokes and bleeding was calculated by the CHA₂DS₂-VASc and HAS-BLED scores. The net clinical benefit was defined as the annual rate of ischemic strokes and systemic emboli prevented by VKAs minus intracranial hemorrhages attributable to the VKA + ASA, multiplied by an impact weight of 1.5. Results Patients on a VKA + ASA were older with more medical comorbidities than those on VKA alone. Using VKA monotherapy as a reference, higher major bleeding rates and all-cause death were evident in those on VKA + ASA. The net clinical benefit of VKA + ASA for the overall cohort was - 0.1%/year (95% confidence interval, - 0.74% to 0.46%). There was a trend toward a negative net clinical benefit from VKA + ASA in patients with a CHA₂DS₂-VASc ≥ 2 and HAS-BLED ≤ 2 (- 1.17%/year). The VKA + ASA yielded a positive net clinical benefit in patients with a CHA₂DS₂-VASc ≥ 2 and HAS-BLED ≥ 3 (1.16%/year). The result patterns were relatively constant using impact weight of 1.0 and 2.0. Conclusions Our estimates of the net clinical benefit can provide a useful anchoring point for adding ASA to VKA in patients with AF.