Quality of Wafarin Control Affects the Incidence of Stroke in Elderly Patients with Atrial Fibrillation

Abstract

Objective Adjusted-dose warfarin therapy can prevent stroke in patients with atrial fibrillation. However, the quality of the warfarin control may be considered to be important for elderly patients. Methods We followed 188 patients (age 70 years) with atrial fibrillation (warfarin, 120 patients; nonwarfarin, 68 patients) for 2 years. Their warfarin control was assessed by time in therapeutic range (TTR) for an international normalized ratio of prothrombin time of 1.6-2.6, based on the Japanese guidelines of anticoagulation for elderly patients with atrial fibrillation. Results Stroke occurred in 23 patients (12.2%). In warfarin-treated patients, receiver-operator characteristic (ROC) curves suggested that patients with TTR >68% had anticoagulation benefit. In the ROC curves for prediction of stroke, the area under the curve of TTR was 0.709 (95% confidence interval, 0.585 to 0.834; p= 0.02). The sensitivity and specificity of TTR 68% were 91.7% and 54.0%, respectively. Kaplan-Meier curves showed that the event-free ratio of stroke was significantly higher in patients who achieved this cut-off of TTR. Conclusion The results suggest that the quality of warfarin control is directly associated with the incidence of stroke in elderly patients.

Time in Therapeutic Range and Disease Outcomes in Elderly Japanese Patients With Nonvalvular Atrial Fibrillation

“…7,18 In addition to the INR value itself, it has been reported that the TTR (which is an index of the quality of INR control) needs to be maintained above 60-75% for a significant reduction in stroke and systemic embolism. [9][10][11][12][13][14] Masaki et al 11 determined the relationship between TTR and the incidence of stroke in 188 elderly Japanese patients with AF. As in the present study, the target INR values in that study were set at 1.6-2.6.…”

“…14 In Japan, this kind of analysis is still limited. 11,15 Therefore, in the present study we analyzed the association between TTR and disease outcomes to determine a critical TTR for effective prevention of thromboembolic events without increasing hemorrhagic events in elderly patients with NVAF using the J-RHYTHM Registry dataset. 16,17 Patients aged <70 years were excluded from the present subanalysis, because approximately 60% of these patients had baseline INR values lower than those recommended by the Japanese guidelines, 7 thereby resulting in unpredictably lower TTR in patients aged <70 years.…”

Time in the Therapeutic Range During Warfarin Therapy in Japanese Patients With Non-Valvular Atrial Fibrillation - A Multicenter Study of Its Status and Influential Factors -

“…Masaki et al retrospectively analyzed 120 Japanese patients with AF and aged ≥70 years who were treated with warfarin according to the Japanese Guideline, and showed that TTR >68% was associated with reduced risk of stroke compared with ≤68%. 20 They also showed that the average PT-INR was not an effective measure for risk stratification.…”

Stroke and Bleeding Risk Associated With Antithrombotic Therapy for Patients With Nonvalvular Atrial Fibrillation in Clinical Practice

“…Over‐the‐counter aspirin use is usually missing in an observational data set, and the outcomes associated with TTR levels in clinical practice have not been extensively studied. Several analyses of randomized controlled trials and some observational studies have examined the relationship between TTR and clinical events. In general, these studies demonstrated the decreased stroke rates in higher TTR, whereas the relationship between the higher TTR and bleeding risk has been more variable …”