Admission international normalized ratio levels, early treatment strategies, and major bleeding risk among non-ST-segment-elevation myocardial infarction patients on home warfarin therapy: insights from the National Cardiovascular Data Registry.

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.