Risks of stroke and mortality associated with suboptimal anticoagulation in atrial fibrillation patients

Abstract

Atrial fibrillation (AF) carries an increased risk of ischaemic stroke, and oral anticoagulation with warfarin can reduce this risk. The objective of this study was to evaluate the association between time in therapeutic International Normalised Ratio (INR) range when receiving warfarin and the risk of stroke and mortality. The study cohort included AF patients aged 40 years and older included in the UK General Practice Research Database. For patients treated with warfarin we computed the percentage of follow-up time spent within therapeutic range. Cox regression was used to assess the association between INR and outcomes while controlling for patient demographics, health status and concomitant medication. The study population included 27,458 warfarin-treated (with at least 3 INR measurements) and 10,449 patients not treated with antithrombotic therapy. Overall the warfarin users spent 63% of their time within therapeutic range (TTR). This percentage did not vary substantially by age, sex and CHA2DS2-VASc score. Patients who spent at least 70% of time within therapeutic range had a 79% reduced risk of stroke compared to patients with ≤30% of time in range (adjusted relative rate of 0.21; 95% confidence interval 0.18-0.25). Mortality rates were also significantly lower with at least 70% of time spent within therapeutic range. In conclusion, good anticoagulation control was associated with a reduction in the risk of stroke.

The clinical effectiveness and cost-effectiveness of point-of-care tests (CoaguChek system, INRatio2 PT/INR monitor and ProTime Microcoagulation system) for the self-monitoring of the coagulation status of people receiving long-term vitamin K antagonist therapy, compared with standard UK practice: systematic review and economic evaluation

“…Furthermore, to assess the generalisability of the annual risks of stroke derived from RE-LY data, these were compared with those derived from a large cohort study of atrial fibrillation patients on warfarin in the UK. Gallagher and colleagues 103 analysed longitudinal data from the General Practice Research Database on 27,458 warfarin users with atrial fibrillation, and provided a Kaplan-Meier plot of the probability of being stroke free by different levels of TTR. Points on these plots were extracted using DigitizeIt software (DigitizeIt, Braunschweig, Germany: www.digitizeit.de), and used to estimate the annual risks of stroke by TTR groupings.…”

Selecting antithrombotic therapy for patients with atrial fibrillation

“…An INR of 2 to 3 offers maximum protection with minimal risk of bleeding. 37,38 Systematic follow-up of patients through anticoagulation clinics produces better compliance and control and is encouraged.…”

Prediction of unstable anticoagulation with acenocoumarol versus warfarin in atrial fibrillation

“…Although non-vitamin K antagonists have been introduced in therapy of AF, vitamin K antagonists (VKA) remained the only treatment with established safety in valvular AF [2]. Quality of anticoagulation with VKA, assessed by the time in therapeutic range (TTR), is closely associated with the risk of stroke [3,4]. Recently, several factors have been incorporated by Apostolakis et al [5] into a clinical prediction scheme with the acronym SAMe-TT 2 R 2 (sex female, age > 60 years, medical history [more than two comorbidities], treatment [interacting drugs, e.g.…”