Differences in outcomes between oral anticoagulation “new starters” and “switchers” in patients with nonvalvular atrial fibrillation: A pooled analysis of the AMADEUS and BOREALIS trials

Background: To explore differences in outcomes between dose-adjusted vitamin K antagonists (VKAs) “new starters” and “switchers” in patients with nonvalvular atrial fibrillation (AF). Methods: A post hoc analysis was performed to assess the outcome differences between VKA “new starters” and “switchers” in AF patients using pooled individual patient data of AMADEUS and BOREALIS trials. Results: A total of 4169 AF patients were included in the present analysis, which included 1383 “VKA new starters” and 2786 “VKA switchers”. VKA new starters had higher crude rates of all-cause mortality (P =.035) and cardiovascular death (P =.047) compared to switchers. On multivariable Cox regression analysis, both “new starters” and “switchers” showed nonsignificant trends for different risks of stroke/systemic thromboembolism (SE) (hazard ratio (HR): 1.66, 95%CI: 0.95-2.90, P =.08), major bleeding (HR: 1.25, 95% CI: 0.73-2.16, P =.42), and all-cause death (HR: 1.09, 95% CI: 0.75-1.57, P =.65). On Kaplan-Meier analysis, both groups had similar risks of stroke/systemic embolism (P =.09), major bleeding (P =.28), and all-cause death (P =.06). Conclusions: In this post hoc analysis of clinical trial patients with AF, “new starters” and “switchers” for VKA initiation had nonstatistically significant rates of trial-adjudicated thromboembolism, major bleeding, and all-cause mortality.