title: Preoperative nonlinear behavior in heart rate variability predicts morbidity and mortality after coronary artery bypass graft surgery.
abstract: BACKGROUND
  The aim was to demonstrate that a reduction in the nonlinear behavior of heart rate variability (HRV) in the preoperative period in patients undergoing coronary artery bypass graft (CABG) triggers higher morbidity and mortality rates in the postoperative stay.
  
  
  METHODS
  Seventy patients (59+/-10.3 years) were included. HRV was captured by a Polar Advanced S810 heart rate monitor and analyzed using the nonlinear variables detrended fluctuation analysis (DFA), autocorrelation (tau), Lyapunov exponent (LE), and the Poincaré plot (PP). Based on two scenarios, death vs. non-death (scenario 1) and events vs. their absence (scenario 2), the occurrence of neurological complications, infections, kidney failure, arrhythmia, and death were evaluated. Sensitivity, specificity, positive predictive value, negative predictive value, and odds ratio (95% CI) were recorded.
  
  
  RESULTS
  In scenario 1, significant differences were found for DFA, alpha-2, LE, PP[SD1], and PP[SD2], with p-values of 0.0172, 0.0343, 0.0159, 0.0069, and 0.0287, respectively. In scenario 2, differences were found for alpha-1, alfa-2, tau, LE, PP[SD1], and PP[SD2], with p-values of 0.0066, 0.0426, 0.0188, 0.0108, 0.0005, and 0.0158, respectively. The best areas under ROC curve were seen in scenario 1, with values of 0.72 (tau), 0.77 (LE), and 0.78 (PP[SD1]).
  
  
  CONCLUSIONS
  Analysis of HRV in the nonlinear domain in the preoperative period in patients undergoing elective CABG surgery may detect subgroups with a high risk for postoperative complications, at least with the assistance of some of the variables, and it can become a new prognostic tool for assessing patients scheduled to undergo other major surgeries.
authors.affiliation: Sao Jose do Rio Preto Medical School, FAMERP, Sao Jose do Rio Preto, Sao Paulo, Brazil.
authors.forename: Moacir Fernandes
authors.initials: MF
authors.lastname: de Godoy
authors.forename: Isabela Thomaz
authors.initials: IT
authors.lastname: Takakura
authors.forename: Paulo Rogério
authors.initials: PR
authors.lastname: Correa
authors.forename: Mauricio de Nassau
authors.initials: MN
authors.lastname: Machado
authors.forename: Rafael Carlos
authors.initials: RC
authors.lastname: Miranda
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Brandi
mesh_terms: D001026:Coronary Artery Bypass / Q000401:mortality*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D016017:Odds Ratio; D011184:Postoperative Period; D011237:Predictive Value of Tests; D011300:Preoperative Care / Q000401:mortality*