Determinants and outcomes of atrial fibrillation complicating myocardial infarction: the EURHOBOP study in Portugal

Abstract

Background: Atrial fibrillation (AF) is a common complication of acute myocardial infarction (AMI) associated with increased morbidity and mortality. This association is less well defined across the spectrum of acute coronary syndromes. We sought to study the incidence, predictors and prognosis of new-onset AF complicating ST-segment elevation AMI (STEMI) and non-ST-segment elevation AMI (NSTEMI). Methods: We studied 977 episodes of STEMI and 1357 of NSTEMI, within a sample of acute coronary syndrome cases from 10 Portuguese hospitals, consecutively discharged within each hospital, in 2009. The discharge notes and electronic/paper medical files were retrospectively reviewed by trained data extractors. Patients with unstable angina or AMI that could not be classified as STEMI vs NSTEMI (either due to left bundle branch block of unknown age or subacute presentation) were excluded from this analysis. We fitted logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Results: A total of 208 patients (8.9%) with AMI developed new-onset AF during the index hospitalization, with no difference between STEMI and NSTEMI (8.8% vs 9.0%, p=0.87). The incidence of AF increased with age in both STEMI (<60 years: 3.1%; ≥ 60 <80 years: 11.8%; ≥80 years: 17.0%, p<0.001) and NSTEMI (2.3%, 10.9% and 14.3%, respectively, p<0.001). In STEMI, left ventricular systolic dysfunction (LVSD), coronary anatomy, peak troponin and invasive treatment were not associated with AF. On other hand, in NSTEMI, revascularization procedures reduced the risk of AF by a half (age, sex and LVSD-adjusted OR 0.48; 95% CI 0.29-0.77). Among NSTEMI patients who underwent coronary angiography, increasing severity of coronary anatomy increased the risk of AF (1-, 2- and 3-vessel disease: 4.6%, 6.1%, 9.3%, respectively, p=0.15).New-onset AF resulted in adverse in-hospital outcomes defined by the composite endpoint clinical heart failure or death (16.1% vs 6.6%, p<0.001). This endpoint was significantly associated with new-onset AF, when adjusting for age, sex, LVSD and revascularization in both STEMI (OR 2.90; 95% CI 1.74-4.80) and NSTEMI (OR 1.69; 95% CI 1.11-2.58) patients. Conclusion: New-onset AF affected STEMI and NSTEMI with similar likelihood and similar consequences, with a 2-fold increase in death or heart failure. However, its predictors differed with type of AMI presentation. Our results suggest that myocardial ischemia may be explaining AF in NSTEMI.