RESUMEN
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.