Clinical features and in-hospital mortality associated with different types of atrial fibrillation in patients with acute coronary syndrome with and without ST elevation

Abstract Background In patients with an acute coronary syndrome (ACS), no conclusive agreement has been reached to date regarding the association between the different types of atrial fibrillation (AF) and the in-hospital mortality risk. We conducted a retrospective cohort study in patients with ACS to determine the prognostic implications of the different types of AF. Methods We analyzed 6705 consecutive patients with ACS admitted to a coronary care unit (CCU), including 3094 with ST segment elevation myocardial infarction (STEMI) and 3611 with non-ST-elevation acute coronary syndrome (NSTE-ACS). We identified the patients with pre-existing AF, new-onset AF at admission, and new-onset AF at the CCU. Results The overall incidence of AF was documented in 360 (5.4%) of the patients (STEMI, 5%; NSTE-ACS, 5.6%), 140 (2.1%) of whom had pre-existing AF, and 220 (3.2%) of whom had new-onset AF (AF at admission, 1.3%; AF at the CCU, 1.9%). The patients with AF had high-risk clinical characteristics and developed major adverse events more frequently than did the patients without AF. The unadjusted in-hospital mortality risk was significantly higher in the patients with pre-existing AF (STEMI, 3.79-fold; NSTE-ACS, 3.4-fold) and AF at the CCU (STEMI, 2.02-fold; NSTE-ACS, 8.09-fold). After adjusting for the multivariate analysis, only the AF at the CCU in the NSTE-ACS group was associated with a 4.40-fold increase in the in-hospital mortality risk (odds ratio 4.40, CI 1.82–10.60, p  = 0.001). In the STEMI group, the presence of any type of AF was not associated with an increased risk of mortality. Conclusion Among the different types of AF in patients with ACS, only the new-onset AF that developed during the CCU stay in patients with NSTE-ACS was associated with a 4.40-fold increase in the in-hospital mortality risk.