Discontinuation rates of warfarin vs. direct acting Oral anticoagulants in US clinical practice: Results from ORBIT-AF II (outcomes registry for better informed treatment of atrial fibrillation II)

Abstract Background While oral anticoagulation is a cornerstone of stroke prevention therapy in atrial fibrillation (AF), few studies have evaluated comparative discontinuation rates in clinical practice. The objective of this study is to evaluate discontinuation rates among patients on warfarin and direct oral anticoagulants (DOACs) in clinical practice. Methods The ORBIT-AF II Registry enrolled 10,005 total AF patients with a CHA2DS2VASc score of ≥2 on warfarin or DOACs from 235 clinical practices across the US from February 13, 2013 and July 12, 2017. Descriptive statistics and multivariable Cox regression modeling were used to describe baseline characteristics and predictors of discontinuation. Unadjusted and adjusted discontinuation rates and 95% confidence intervals (CI) were calculated using Cox proportional hazards models and propensity score adjustment, respectively. Results At baseline, 16.4% (N = 1642/10,005) were treated with warfarin, 83.6% (N = 8363/10,005) with DOACs and 1498/10,005 patients (15.0%) discontinued therapy [warfarin = 236/1642 (14.4%) vs. DOACs = 1262/8363 (15.1%)]. At 6 and 12 months respectively, among 7049 patients with a new diagnosis of AF within 6 months, adjusted discontinuation rates for warfarin vs. DOACs were as follows: [6 months: 7.9%, 95%CI (6.8%–9.0%) vs. 9.6% (8.4%–10.7%), P = .16]; [12 months: 12.7% (11.0%–14.3%) vs. 15.3% (13.6%–16.9%), P = .02)]. Patients who discontinued therapy with warfarin or DOACs had higher risk of adverse clinical outcomes including: all-cause mortality and cardiovascular death (CV) than those who continued treatment. Conclusion In a community based AF cohort, adjusted rates of discontinuation at 12-months were higher in DOAC-treated versus VKA-treated patients. Discontinuation of oral anticoagulation was associated with increased absolute risk of all-cause mortality and CV death. Clinical Trial Registration: URL: https://clinicaltrials.gov . Unique Identifier: NCT01701817