Atrial fibrillation and acute myocardial infarction: antithrombotic therapy and outcomes

Abstract

Background: Atrial fibrillation guidelines recommend long-term use of warfarin according to a patient's predicted risk of stroke. After acute myocardial infarction, however, combining warfarin and antiplatelet medications poses challenges.

Methods: By using data from more than 69,255 patients with acute myocardial infarction who were enrolled in the National Cardiovascular Data Registry's Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines at 309 hospitals from July 1, 2008, to September 30, 2009, we describe the characteristics and outcomes of the population with myocardial infarction with atrial fibrillation diagnosed within 2 weeks before index myocardial infarction admission (7.1%, N=4947). Use of discharge antithrombotic therapy is described overall and across levels of predicted stroke and bleeding risks.

Results: Compared with patients without atrial fibrillation, those with atrial fibrillation before their index myocardial infarction were older and had more comorbidities and worse in-hospital outcomes. Only 32.5% of patients with atrial fibrillation were taking warfarin before their myocardial infarction admission. In these patients, use of warfarin at discharge increased with higher Congestive heart failure, Hypertension, Age, Diabetes, Stroke [Doubled] (CHADS(2)) risk strata (28.5%, 34.6%, and 43.5% for CHADS(2) scores 0, 1, and ≥2; P<.001) and increased in patients at low, intermediate, and high risk of bleeding (25.4%, 42.3%, and 42.1%; P=.004). Triple therapy at discharge (aspirin plus clopidogrel plus warfarin) was used in a minority of this population (14.6%).

Conclusions: Use of warfarin at discharge in patients with atrial fibrillation is greater among those with higher stroke and bleeding risks, but despite higher-risk profiles, less than half received warfarin at discharge. These findings highlight that clarification is needed to guide choice of antithrombotic therapy for patients with both atrial fibrillation and acute myocardial infarction.