Role of Red Cell Distribution Width in the Relationship between Clinical Outcomes and Anticoagulation Response in Patients with Atrial Fibrillation.

Little is known as to why elevated red cell distribution width (RDW) is associated with adverse clinical outcomes in patients with atrial fibrillation (AF). We hypothesized that RDW value might predict the intensity of anticoagulation, resulting in higher adverse events in patients with AF taking warfarin. We analyzed 657 patients with non-valuvular AF who took warfarin. The intensity of anticoagulation was assessed as mean time in the therapeutic range (TTR) and defined TTR ≥60% as an optimal intensity. The primary end-point was the composite of stroke/systemic embolism and major bleeding. The secondary end-point was the composite of stroke/systemic embolism, major bleeding and death. The relationship between the baseline RDW with TTR and clinical outcomes was assessed using categorical variables as quartiles or dichotomous variables. The mean value of TTR decreased as an increment of the RDW (45.2% vs. 44.7% vs. 40.8% vs. 35.2%, p<0.001). Primary and secondary end-points were significantly increased when TTR was less than 60% and RDW was more than 13.6%. Ratio of patients achieving optimal anticoagulation were significantly decreased as an increment of RDW. A RDW of ≥13.6% was a significant predictor for poor anticoagulation control (adjusted Odds ratio [OR] 0.43, 95% confidence interval [CI] 0.23-0.82), stroke (adjusted hazard ratio [HR] 3.86, 95% CI 1.11-13.40), primary (adjusted HR 1.88, 95% CI 1.12-3.16) and secondary end-point (adjusted HR 2.46, 95% CI 1.26-4.81). RDW was negatively associated with TTR in patients with AF. Therefore, RDW might be a useful marker for the prediction of anticoagulation response and clinical outcomes in patients with AF.