Abstract 271: Anti-coagulation and Ischemic Stroke Risk in Patients with Chronic Kidney Disease and Atrial Fibrillation: Insights from the Kaiser Permanente Colorado Atrial Fibrillation Registry

Abstract

Background: There is uncertainty about the benefits of anticoagulation therapy for stroke reduction in CKD patients with atrial fibrillation. Accordingly, we assessed the association between anticoagulation use and stroke risk in CKD patients with atrial fibrillation. Methods: The Kaiser Permanente Colorado Atrial Fibrillation Registry is comprised of patients with incident atrial fibrillation between January 1, 2006 and June 30, 2012 from Kaiser Permanente Colorado. Incident atrial fibrillation was defined by ICD-9 codes 427.31 (Atrial Fibrillation) or 427.32 (Atrial Flutter) and without a diagnosis in the prior year. Patients with mitral valve replacement, renal transplant, or use of anticoagulants other than warfarin were excluded. CKD status was determined by ICD-9 codes or by two consecutive outpatient laboratory results with estimated glomerular filtration rate < 60 ml/min/1.73m2 by the CKD-EPI equation. The primary outcome was ischemic stroke identified by ICD-9 codes and validated by chart review. We assessed the association between warfarin use and ischemic stroke in patients with and without CKD using Cox proportional hazards models adjusted for CHA2DS2-VASc score and an interaction for warfarin use and CKD. Results: Of 5,728 patients with incident atrial fibrillation, 2,070 (36.1%) had CKD. Patients with CKD were older, more likely to be female, had a higher CHA2DS2-VASc score, and were more likely to receive warfarin than those without CKD (see Table). During a mean follow up of 2.6 years (SD 1.8 years), stroke occurred in 49 (2.4%) patients with CKD and 83 (2.3%) patients without CKD. In multivariable analysis adjusting for CHA2DS2-VASc score, warfarin use was associated with lower hazard of stroke (HR 0.36; 95% CI 0.24 - 0.53). When stratified by CKD status, warfarin use remained associated with lower hazard of stroke in CKD (HR 0.35; 95% CI 0.18 - 0.66) and non CKD (HR 0.36; 95% CI 0.22 - 0.60) patients. Conclusion: 1 in 3 patients with atrial fibrillation have CKD. There were similar reductions in the risk of stroke associated with warfarin use for CKD and non-CKD patients. These findings reinforce current clinical practice guidelines, which recommend warfarin use based on thromboembolic risk without consideration for CKD status.