Reasons for warfarin discontinuation in the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF)

Abstract

Background: Warfarin reduces thromboembolic risks in atrial fibrillation (AF), but therapeutic durability remains a concern.

Methods: We used clinical data from ORBIT-AF, a nationwide outpatient AF registry conducted at 176 sites with follow-up data at 6 and 12 months, to examine longitudinal patterns of warfarin discontinuation. We estimated associations between patient and provider characteristics and report of any warfarin discontinuation using discrete time proportional odds models.

Results: Of 10,132 AF patients enrolled in ORBIT-AF from June 2010 to August 2011, 6,110 (60.3%) were prescribed warfarin, had follow-up data, and were not switched to an alternative oral anticoagulant enrolled from June 2010 to August 2011. Over 1 year, 617 patients (10.1% of baseline warfarin users) discontinued warfarin therapy. Among incident warfarin users (starting therapy within 1 year of baseline survey), warfarin discontinuation rates rose to 17.1%. The most commonly reported reasons for warfarin discontinuation were physician preference (47.7%), patient refusal/preference (21.1%), bleeding event (20.2%), frequent falls/frailty (10.8%), high bleeding risk (9.8%), and patient inability to adhere to/monitor therapy (4.7%). In multivariable analysis, the factors most strongly associated with warfarin discontinuation were bleeding hospitalization during follow-up (odds ratio 10.91, 95% CI 7.91-15.03), prior catheter ablation (1.83, 1.37-2.45), noncardiovascular/nonbleeding hospitalization (1.77, 1.40-2.24), cardiovascular hospitalization (1.64, 1.33-2.03), and permanent AF (0.25, 0.17-0.36).

Conclusions: Discontinuation of warfarin is common among patients with AF, particularly among incident users. Warfarin is most commonly discontinued because of physician preference, patient refusal, and bleeding events.