Effect of suboptimal anticoagulation treatment with antiplatelet therapy and warfarin on clinical outcomes in patients with nonvalvular atrial fibrillation: A population-wide cohort study

Esther W Chan, Wallis C Y Lau, Chung Wah Siu, Gregory Y H Lip, Wai K Leung, Shweta Anand, Kenneth K C Man, Ian C K Wong
Heart Rhythm: the Official Journal of the Heart Rhythm Society 2016, 13 (8): 1581-8

BACKGROUND: The actual consequence of suboptimal anticoagulation management in patients with nonvalvular atrial fibrillation (NVAF) is unclear in the real-life practice.

OBJECTIVE: The purpose of this study was to identify the prevalence of suboptimally anticoagulated patients with NVAF and compare the effectiveness and safety of antiplatelet drugs with warfarin.

METHODS: We performed a retrospective cohort study using a population-wide database managed by the Hong Kong Hospital Authority. Patients newly diagnosed with NVAF during 2010-2013 were included in the analysis. A Cox proportional hazards regression model with 1:1 propensity score matching was used to compare the risk of ischemic stroke, intracranial hemorrhage, gastrointestinal bleeding, and all-cause mortality between patients receiving antiplatelet drugs and those receiving warfarin stratified by level of international normalized ratio (INR) control.

RESULTS: Of the 35,551 patients with NVAF, 30,294 (85.2%) had a CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years [doubled], diabetes mellitus, age 65-74 years, prior stroke/transient ischemic attack [doubled], vascular disease, and sex category [female]) score of ≥2 (target group for anticoagulation). Of these, 7029 (23.2%) received oral anticoagulants and 18,508 (61.1%) received antiplatelet drugs alone. There were 1541 (67.7%) of warfarin users who had poor INR control (time in therapeutic range [2.0-3.0] <60%). Patients receiving warfarin had comparable risks of intracranial hemorrhage (hazard ratio [HR] 1.24; 95% confidence interval [CI] 0.65-2.34) and gastrointestinal bleeding (HR 1.23; 95% CI 0.84-1.81) and lower risk of ischemic stroke (HR 0.40; 95% CI 0.28-0.57) and all-cause mortality (HR 0.45; 95% CI 0.36-0.57) than did patients receiving antiplatelet drugs alone. Good INR control was associated with a reduced risk of ischemic stroke (HR 0.48; 95% CI 0.27-0.86) as compared with poor INR control. Modeling analyses suggested that ~40,000 stroke cases could be potentially prevented per year in the Chinese population if patients were optimally treated.

CONCLUSION: More than three-quarters of high-risk patients among this Chinese population with NVAF were not anticoagulated or had poor INR control. There is an urgent need to improve the optimization of anticoagulation for stroke prevention in patients with atrial fibrillation.

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