title: [Incidence of atrial fibrillation after cardiac surgery: Influence of the type of surgery, cardiopulmonary bypass and preoperative and perioperative predictive factors].
abstract: BACKGROUND
  Atrial fibrillation (AF) is the arrhythmia with higher incidence in postoperative period after cardiac surgery. In individuals undergoing valve replacement surgeries (VRS) it occurs in about 64% and in individuals undergoing coronary artery bypass grafting (CABG) it can occurs in about 30-40%. Its incidence in postoperative period can still be influenced by pre and perioperative risk factors.
  
  
  OBJECTIVE
  To study the incidence of AF after cardiac surgery, its association with the type of surgery, cardiopulmonary bypass (CPB), and with the main pre and perioperative risk/predictive factors.
  
  
  METHODS
  Longitudinal retrospective observational study of individuals undergoing CABG and VRS in 2014, in a central hospital in the northern region. Cardiac rhythm was evaluated in four moments of postoperative period (end of CPB, Intensive Care Unit (ICU)/hospitalization, pre-hospital discharge, follow-up). The association of cardiac rhythm and preoperative risk/predictive factors (size of the atria, cardiomegaly, left ventricular hypertrophy (LVH)) and intraoperative risk factors (type of surgery, duration of CPB, aortic clamping time and cardioplegia administration) were explored through Odds ratio (OR).
  
  
  RESULTS
  We studied 416 individuals, 73.6 % male, mean age 66.8±10.5 years old. VRS showed incidence values of AF in all evaluation moments, and CABG only in ICU/internment and pre-hospital discharge. The incidence of AF was higher in ICU/internment in all types of surgery, ranging from 3.7% (CABG with CPB) to 71.4% (mitral VRS). Preoperative predictive factors with an OR>1 were age upper 65 years old (2.51 end of CPB, 10.62 pre-hospital discharge), dilation of the right atrium (RA) (1.08 follow-up, 3.41 pre-hospital discharge), and LVH (1.68 end of CPB, 2.78 pre-hospital discharge). Perioperative predictive factors with an OR>1 were CPB (2.74 ICU/interment, 3.37 pre-hospital discharge), and cardioplegia (2.93 ICU/internment, 5.40 pre-hospital discharge).
  
  
  CONCLUSIONS
  VRS were the type of surgery with higher incidence of AF. CABG had a higher incidence of AF in surgeries without CPB. Age upper 65 years old, RA dilation and LVH were the preoperative predictive factors with positive association with AF incidence in all evaluation moments.
authors.affiliation: Escola Superior de Tecnologia da Saúde do Porto, Centro Hospitalar de Vila Nova de Gaia/Espinho, CUF Porto, Instituto e Hospital e CINTESIS (Centre for Health Technology and Services Research), Portugal.
authors.forename: Soraia
authors.initials: S
authors.lastname: Moreira
authors.forename: Nelson
authors.initials: N
authors.lastname: Paulo
authors.forename: Luís
authors.initials: L
authors.lastname: Vouga
authors.forename: Tiago
authors.initials: T
authors.lastname: Jacinto
authors.forename: Cristina
authors.initials: C
authors.lastname: Baeta