Safety and effectiveness of antithrombotic strategies in older adult patients with atrial fibrillation and non-ST elevation myocardial infarction

Background: We aimed to study the comparative safety and effectiveness of various antithrombotic treatment strategies among older adults with non-ST elevation myocardial infarction (NSTEMI) and atrial fibrillation (AF). Methods: Using the CRUSADE registry linked to longitudinal Medicare claims data, we examined NSTEMI patients aged ≥ 65 years with a concomitant diagnosis of AF. Multivariable Cox analysis was used to compare risk of rehospitalization for bleeding and a major cardiac composite end point of death, readmission for myocardial infarction, or stroke, according to discharge antithrombotic strategy. Results: Among 7619 NSTEMI patients with AF, 29% were discharged on aspirin alone; 37%, on aspirin + clopidogrel; 7%, on warfarin alone; 17%, on aspirin + warfarin; and 10%, on warfarin + aspirin + clopidogrel. There was no difference in predicted stroke risk between groups. By 1 year, 12.2% of patients were rehospitalized for bleeding, and 33.1% had a major cardiac event. Relative to aspirin alone, antithrombotic intensification was associated with increased bleeding risk (aspirin + clopidogrel adjusted HR 1.22, 95% CI 1.03-1.46 and warfarin + aspirin HR 1.46, 95% CI 1.21-1.80). Patients treated with aspirin + clopidogrel + warfarin had the highest observed bleeding risk (HR 1.65, 95% CI 1.30-2.10). One-year risk of the major cardiac end point was similar between groups, although, relative to aspirin only, there was a trend toward lower risk for the warfarin + aspirin group (HR 0.88, 95% CI 0.78-1.00). Conclusions: Older NSTEMI patients with AF are at high risk for subsequent bleeding and major cardiac events. Increased antithrombotic management was associated with increased bleeding risk. Further investigation is needed to clarify whether these risks are counterbalanced by reduced thromboembolic events in this population.