Abstract 4580: Proteinuria and Reduced Glomerular Filtration Rate Independently Increase Risk of Thromboembolism in Atrial Fibrillation: The ATRIA Study
Atrial fibrillation (AF) substantially increases the risk of ischemic stroke but this risk varies among patients with AF. Existing stroke risk stratification schemes have limited predictive ability. Chronic kidney disease is a major cardiovascular risk factor, but whether it independently increases the risk for stroke in AF is unknown. In a large, diverse cohort of adults with nonvalvular atrial fibrillation, we examined how chronic kidney disease (i.e., reduced glomerular filtration rate or proteinuria) affects risk of thromboembolism off anticoagulation in patients with AF. We estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease equation and proteinuria from urine dipstick results found in laboratory databases. Data on patient characteristics, stroke risk factors, longitudinal use of warfarin therapy, and thromboembolic events between 1996 –2003 were ascertained from validated clinical databases. Thromboembolic events (ischemic stroke and other systemic embolism) were confirmed by chart review. We used multivariable Poisson regression to evaluate the independent association between reduced eGFR and documented proteinuria with risk of thromboembolic events off warfarin therapy. During 33,165 person-years off anticoagulation among 13,535 patients with AF and no prior dialysis or renal transplant, we observed 676 incident thromboembolic events. After adjustment for known risk factors for stroke and level of eGFR, proteinuria increased the risk of thromboembolism by 54% (adjusted relative risk [RR] 1.54, 1.28 to 1.84). Independent of proteinuria and other confounders, there was a graded, increased risk of stroke associated with progressively lower eGFR compared with eGFR ≥60 (in units of ml/min/1.73 m2): adjusted RR 1.16 (95% CI: 0.95 to 1.40) for eGFR 45– 59, and RR 1.39 (1.12 to 1.71) for eGFR <45 (P=0.001 for trend). Chronic kidney disease increases the risk of thromboembolism in AF independent of other stroke risk factors. Knowing the level of kidney function and presence of proteinuria can potentially improve risk stratification for decision-making about the use of antithrombotic therapy for stroke prevention in AF.