Abstract 13842: Association of CHADS2VASc Score and Warfarin Use With Thromboembolic Risk Among HIV-Infected Persons With Atrial Fibrillation

Abstract

Introduction: The prevalence of atrial fibrillation in the human immunodeficiency virus (HIV)-infected population is growing, but the association of the CHADS2VASc score with thromboembolic (TE) risk is unknown in this population. Objective: We evaluated the association of the CHADS2VASc score with TE events in HIV patients with atrial fibrillation, and the effectiveness of warfarin for TE prevention. Methods: Within the Veterans Affairs HIV Clinical Case Registry, 914 patients had an atrial fibrillation diagnosis between 1997-2011 with no prior TE events. We compared TE incidence by CHADS2VASc scores, overall and stratified by warfarin use. Using Cox proportional hazards regression, we modeled associations of CHADS2VASc scores and warfarin use with TE risk. Results: At baseline, the number of patients with CHADS2VASc scores of 0, 1, and 2+ were 208, 285, and 421 respectively; 36 patients developed TE events during a median of 3.8 years follow-up. Unadjusted event rates for CHADS2VASc score groups of 0, 1, and 2+ were 5.4, 10.0, and 8.7 per 1000 person years, respectively (hazard ratio [HR]=1.83 [95% confidence interval {CI} 0.71, 4.73] for CHADS2VASc score 1 versus 0, p =0.21; HR=1.43 [95% CI 0.55, 3.69] for CHADS2VASc score 2 or higher versus 0, p =0.46). Warfarin use was significantly associated with increased risk of TE events, even after adjusting for CHADS2VASc scores (HR=2.15 [95% CI 1.05, 4.41], p =0.037). Warfarin use per year of exposure among current users had a HR of 2.64 for TE events (95% CI 1.28, 5.45; p =0.0089). Time-updated warfarin use showed an even stronger association with increased risk of TE events (HR=6.07 [95% CI 2.95, 12.5], p <0.0001). Conclusions: In this national registry of HIV-infected veterans with atrial fibrillation, CHADS2VASc scores were only weakly associated with risk of TE events, and warfarin was not effective at preventing TE events and potentially harmful. These results should raise concerns about the optimal strategy for prevention of TE events among HIV-infected persons with atrial fibrillation.