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 STelevation 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. 2174-2049Document downloaded from http://www.elsevier.pt, day 01/07/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited. ST (p=0,003). Por sua vez, a FAp foi mais comum em doentes idosos (p=0,032), com diâmetro superior da aurícula esquerda (p=0,001) e ausência de doença coronária (p=0,034). Quanto à estratégia terapêutica, os doentes com FAn foram mais vezes submetidos a controlo de ritmo durante o internamento (p<0,001), mas menos hipocoagulados à alta (p=0,001). Quando comparada com a população sem FA, a FAn foi preditora de morte hospitalar na análise univariada (p<0,001) e multivariada (OR 2,67, p=0,047), enquanto a FAp não. Já no follow-up, a FAp associou-se a maior mortalidade (p=0,014), enquanto os doentes com FAn apresentaram apenas uma tendência para um pior prognóstico. Conclusões: O impacto prognóstico negativo da FA na fase aguda das SCA parece ocorrer apenas nos doentes que apresentam FAn e não naqueles com FAp. PALAVRAS-CHAVE

Age, LVEF ≤40% and LA diameter are independent predictors of new-onset AF during ACS. This arrhythmia is associated with higher overall mortality (in-hospital and in follow-up).

MSI was shown to be a valuable bedside tool which can rapidly identify high-risk STEMI patients at presentation.

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 STelevation 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. 2174-2049Document downloaded from http://www.elsevier.pt, day 01/07/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited. ST (p=0,003). Por sua vez, a FAp foi mais comum em doentes idosos (p=0,032), com diâmetro superior da aurícula esquerda (p=0,001) e ausência de doença coronária (p=0,034). Quanto à estratégia terapêutica, os doentes com FAn foram mais vezes submetidos a controlo de ritmo durante o internamento (p<0,001), mas menos hipocoagulados à alta (p=0,001). Quando comparada com a população sem FA, a FAn foi preditora de morte hospitalar na análise univariada (p<0,001) e multivariada (OR 2,67, p=0,047), enquanto a FAp não. Já no follow-up, a FAp associou-se a maior mortalidade (p=0,014), enquanto os doentes com FAn apresentaram apenas uma tendência para um pior prognóstico. Conclusões: O impacto prognóstico negativo da FA na fase aguda das SCA parece ocorrer apenas nos doentes que apresentam FAn e não naqueles com FAp. PALAVRAS-CHAVE

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