Impact of atrial fibrillation type during acute coronary syndromes: Clinical features and prognosis.

INTRODUCTION Atrial fibrillation (AF) is widely recognized as an adverse prognostic factor during acute myocardial infarction, although the impact of AF type - new-onset (nAF) or pre-existing (pAF) - is still controversial. OBJECTIVES To identify the clinical differences and prognosis of nAF and pAF during acute coronary syndromes (ACS). METHODS We performed a retrospective observational cohort study including 1373 consecutive patients (mean age 64 years, 77.3% male) admitted to a single center over a three-year period, with a six-month follow-up. RESULTS AF rhythm was identified in 14.5% patients, of whom 71.4% presented nAF and 28.6% pAF. When AF types were compared, patients with nAF more frequently presented with ST-elevation ACS (p=0.003). Patients with pAF, in turn, were older (p=0.032), had greater left atrial diameter (p=0.001) and were less likely to have significant coronary lesions (p=0.034). Regarding therapeutic strategy, nAF patients were more often treated by rhythm control during hospital stay (p<0.001) and were less often anticoagulated at discharge (p=0.001). Compared with the population without AF, nAF was a predictor of death during hospital stay in univariate (p<0.001) and multivariate analysis (OR 2.67, p=0.047), but pAF was not. During follow-up, pAF was associated with higher mortality (p=0.014), while nAF patients presented only a trend towards worse prognosis. CONCLUSIONS AF during the acute phase of ACS appears to have a negative prognostic impact only in patients with nAF and not in those with pAF.