Anticoagulation Control in Older Atrial Fibrillation Patients Receiving Vitamin K Antagonist Therapy for Stroke Prevention

Abstract

Introduction. Efficacy and safety of vitamin K antagonists (VKAs) among atrial fibrillation (AF) patients are enhanced when the International Normalised Ratio (INR) is 2.0–3.0. Anticoagulation control among older patients is perceived to be lower and contributes to poorer initiation and uptake. Objective. To examine the quality of INR control, adverse clinical outcomes, and factors associated with bleeding in older AF patients (≥80 years). Methods. Anticoagulation control assessed by time in therapeutic range (TTR) (Rosendaal method) and percentage INRs in range (PINRR). Among the 205 patients aged ≥80 years, 58.5% were female, with mean (SD) CHA2DS2-VASc 4.4 (1.3) and HAS-BLED 1.8 (0.8) scores. Results. Mean (SD) TTR and PINRR were similar for those aged ≥80 vs. <80 years (66.7 (13.8) vs. 66.7 (13.1)) despite significantly lower INR monitoring intensity (51.2 (22.7) vs. 60.7 (25.8)) and shorter follow-up (4.4 (2.6–6.2) vs. 5.7 years (3.3–7.1)) in those ≥80 years of age. Good anticoagulation control (TTR and PINRR ≥70%) of 44% was seen in both age groups. No significant differences in composite major adverse clinical events were evident for those aged ≥80 vs. <80 years ( $p$  = 0.55). Cox regression analysis confirmed that age ≥80 years was associated with higher risk of bleeding (HR 1.90 (1.01–3.56); $p$  = 0.047). Conclusions. Suboptimal (TTR and PINRR <70%) anticoagulation control was evident in all patients. Risk of bleeding increased, but there was no difference in thromboembolic events and all-cause mortality in those aged ≥80 years. Improving TTR to ≥70% and enhancing anticoagulation monitoring of VKA use remain a clinical priority to prevent bleeding complications, particularly among those aged 80 years and above.