Admission International Normalized Ratio Levels, Early Treatment Strategies, and Major Bleeding Risk Among Non–ST-Segment–Elevation Myocardial Infarction Patients on Home Warfarin Therapy

Abstract

Background— Non–ST-segment–elevation myocardial infarction patients on home warfarin pose treatment concerns because of their potential increased risk of bleeding. Expert opinion from the American College of Cardiology/American Heart Association guidelines suggest holding anticoagulants and initiating antiplatelet therapy among therapeutically anticoagulated non–ST-segment–elevation myocardial infarction patients. Yet, little is known about contemporary treatment patterns and bleeding risks in this population. Methods and Results— We stratified 5787 non–ST-segment–elevation myocardial infarction patients on home warfarin therapy using data from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network Registry–Get With the Guidelines by admission international normalized ratio (INR) levels: subtherapeutic (INR <2), therapeutic (INR, 2–3), and supratherapeutic (INR >3). Multivariable logistic generalized estimating equations models were constructed to examine the associations between admission INR level, early antithrombotic treatment and invasive therapy, and risk of in-hospital major bleeding. Among these patients, 46%, 35%, and 19% had subtherapeutic, therapeutic, and supratherapeutic admission INR levels, respectively. Risk of major bleeding was higher among patients with therapeutic (15%; adjusted odds ratio, 1.25; 95% confidence interval [CI], 1.03–1.50) and supratherapeutic (22%; odds ratio, 1.60; 95% CI, 1.30–1.97) anticoagulation compared with the subtherapeutic group (12%). Among patients with admission INR ≥2, 45% were treated with early (within 24 hours) heparin, 35% with early clopidogrel, 14% with early glycoprotein IIb/IIIa inhibitor, and 36% with early invasive strategy. Early antithrombotic treatment was associated with increased bleeding risk (odds ratio, 1.40 [95% CI, 1.14–1.72] for heparin; 1.50 [95% CI, 1.22–1.84] for clopidogrel; and 1.82 [95% CI, 1.43–2.32] for glycoprotein IIb/IIIa inhibitor); however, an early invasive strategy was not (odds ratio, 1.09; 95% CI, 0.86–1.37). No significant interactions were observed between INR level and use of each early treatment in its association with bleeding. Conclusions— National patterns of early antithrombotic treatment for non–ST-segment–elevation myocardial infarction patients on home warfarin diverge from expert opinion provided by current practice guidelines. Early antithrombotic treatment was associated with increased bleeding risk regardless of admission INR level.