BackgroundAtrial fibrillation (AF) is associated with increased cardiovascular mortality. Data regarding the relationship between coronary artery disease (CAD) and AF is mixed. It is uncertain if AF directly increases the risk for future coronary events and if such patients are appropriately evaluated for CAD.MethodsThis is a cross-sectional study performed on hospitalized patients with AMI and concurrent AF in 2019 using National Inpatient Sample from HCUP. Patients with missing information and type II non-ST elevation myocardial infarction (NSTEMI) were excluded. Using STATA 18, In-hospital mortality, ischemic evaluation, percutaneous treatment, rates of ventricular tachycardiac (VT), ventricular fibrillation (VF), cardiogenic shock, cardiac arrest, average length of stay (LOS), and total hospitalization charges were studied. Regression models were used for data analyses.ResultsA total of 600,645 patients met inclusion criteria (219,660 females [36.5%], 428,755 Caucasian [71%], 65,870 African American [10.9%], 51,155 Hispanic [8.5%]; mean [SD] age, 66.7 [0.5] years), including 166,680 (28%) STEMI and 433,965 (72%) NSTEMI patients. 109,520 (18%) patients with AMI had AF. For patients with AMI and AF, the adjusted odds of mortality increased by 23% (adjusted Odds ratio [aOR], 1.23; CI, 1.15-1.32; p<0.001). AF patients were less likely to undergo ischemic evaluation (aOR, 0.77; CI, 0.74-0.80; p<0.001) and ischemic intervention (aOR, 0.64; CI, 0.62-0.66; p<0.001). AF patients had higher odds of VT (aOR, 1.41; CI, 1.33-1.49; p<0.001), VF (aOR, 1.44; CI, 1.33-1.57; p<0.001), cardiogenic shock (aOR, 1.43; CI, 1.35-1.52; p<0.001), and cardiac arrest (aOR, 1.35; CI, 1.24-1.47; p<0.001). AF patients had longer LOS (mean, 1.39; SCD, 1.29-1.48; p<0.001) and higher total hospital charges (mean $22,188; 19,311-25,064, p<0.001).ConclusionAF was independently associated with increased mortality in patients admitted with AMI. AF was associated with higher rates of cardiac complications. Patients with AF were less likely to receive ischemic evaluation or percutaneous intervention and had overall higher healthcare resource utilization. This study encourages AF to be viewed as an independent risk factor for CAD and suggests more efforts to diagnose CAD in such patients.Clinical PerspectiveWhat is newPatients with acute myocardial infarction and atrial fibrillation have higher odds of mortality.AMI patients with AF are subjected to lesser odds of undergoing ischemic evaluation and intervention.Healthcare resource utilization is higher in this cohort.What are the clinical implicationsAF should be considered as an independent risk factor for increased mortality in AMI.Early ischemic evaluation should be considered to diagnose coronary artery disease in this cohort.Increased awareness to recognize all risk factors of coronary artery disease.