Early Versus Late New-Onset Atrial Fibrillation in Acute Myocardial Infarction: Differences in Clinical Characteristics and Predictors

New-onset atrial fibrillation (NOAF) during acute myocardial infarction (AMI) has significant consequences but is often misdiagnosed. The aim of the study was to evaluate predictors of NOAF throughout different phases of AMI. Patients with AMI admitted to a tertiary medical center were analyzed. Exclusion criteria were preexisting AF, AMI onset ≥24 hours prior to admission, in-hospital death, significant valvular disease, and in-hospital coronary artery bypass graft. Study population were AMI without-NOAF, early-AF (AF terminated within 24 hours of admission), and late-AF (beyond the first 24 hours). Overall 5946 patients were included, age: 64.8 ±14.8 years; 30% women. The incidence of NOAF was 4.6%: 1.6% early-AF, and 3% late-AF. Patients with NOAF comprised greater rate of women, cardiovascular risk-factors burden, severe left ventricular-dysfunction, pulmonary hypertension, valvular disorders, and left atrial enlargement compared with patients without-NOAF. Non-ST-elevation myocardial infarction and inferior-ST-elevation myocardial infarction (STEMI) were significantly more prevalent among early-AF group, while anterior-STEMI, in late-AF. The final multivariate models showed c-statistics of 0.73 and 0.76 for the prediction of new-onset early-AF and late-AF, respectively. In conclusion, there are different clinical predictors of early- versus late-NOAF. The study points out “high risk” AMI population for more meticulous heart rate monitoring for NOAF.