What is the absolute risk reduction with apixaban for stroke or systemic embolism in subclinical atrial fibrillation (SCAF)? A reanalysis of the ARTESIA trial, presented at the ACC.26, suggests that the absolute risk reduction may be smaller when competing events are considered.

This was a secondary methodological analysis of a randomized controlled trial. The original ARTESIA trial evaluated apixaban versus aspirin in patients with SCAF lasting 6 minutes to 24 hours. The reanalysis reconstructed individual time-to-event and censoring data from published Kaplan-Meier curves. 

In the primary analysis, deaths and progression to ≥24-hour atrial fibrillation (AF) were treated as censoring events. In this framework, these events were reclassified as competing events. The Aalen-Johansen estimator was used to calculate cumulative incidence and absolute risk reduction (ARR).

At 6 years, ARR for stroke or systemic embolism was 2.09% (95% CI, −0.17 to 4.34) with the standard Kaplan-Meier approach. When competing events were incorporated, ARR was 1.68% (95% CI, 0.46 to 2.89). This represents a lower absolute effect estimate when accounting for competing risks.

These findings are relevant for interpreting anticoagulation benefit in SCAF, where competing clinical events are frequent. Apixaban was associated with a modest reduction in stroke or systemic embolism in SCAF, with a smaller absolute effect when competing risks were considered.