OBJECTIVES: To estimate clinical outcomes, healthcare utilization and cost burden of patients who suffered a myocardial infarction during the 180 days after diagnosis of non-valvular atrial fibrillation (NVAF) and compare it with patients who did not suffer a myocardial infarction. METHODS: Based on 2005-2007 U.S. Medicare advantage insurance claim files, patients aged 65 years and older who have had two or more primary diagnoses for NVAF occurring within 30 days of one another were selected. The 180-day follow-up event rates, healthcare facility use and costs for patients with a myocardial infarction and those without were compared. Risk adjustment was performed using the propensity score matching method with the ProbChoice™ algorithm. RESULTS: In patients who were identified with NVAF (n=18,575), 258 (1.39%) suffered a myocardial infarction during the 180 days after NVAF diagnosis. Patients were not significantly different in terms of gender, region, and baseline comorbid conditions. After risk-adjustment for pre-specified covariates, mortality (10.08% vs. 0.39% p<0.0001), outpatient emergency room (ER) visits (82.56% vs. 48.06% p<0.0001), acute coronary syndrome (63 vs. 2/100 person years), ischemic stroke (31 vs. 4/100 person years), major bleeding (10 vs. 1/100 person years) and non-major clinical relevant bleeding (24 vs. 6/100 person years) were all higher for patients who suffered a myocardial infarction compared to those who did not.  Besides inpatient costs ($26,646 vs. $9,393), risk-adjusted outpatient ER costs ($1,176 vs. $863) were also higher for myocardial infarction patients. The overall risk-adjusted difference in health care costs is significant ($36,584 vs. $10,366 p<0.0001). CONCLUSIONS: Most of the adverse events analyzed were higher for patients who suffered a myocardial infarction after NVAF relative to patients who did not. Total health care utilization and costs were also significantly increased.