title: Depressed sympathovagal balance predicts mortality in patients with subarachnoid hemorrhage.
abstract: OBJECTIVE
  The objective of this study is to investigate the role of sympathovagal balance in predicting inhospital mortality by assessing power spectral analysis of heart rate variability (HRV) among patients with nontraumatic subarachnoid hemorrhage (SAH) in an emergency department (ED).
  
  
  METHODS
  A cohort of 132 adult patients with spontaneous SAH in an ED was prospectively enrolled. A continuous 10-minute electrocardiography for off-line power spectral analysis of the HRV was recorded. Using the inhospital mortality, the patients were classified into 2 groups: nonsurvivors (n=38) and survivors (n=94). The HRV measures were compared between these 2 groups of patients.
  
  
  RESULTS
  Having compared the various measurements, the very low-frequency component, low-frequency component, normalized low-frequency component (LF%), and low-/high-frequency component ratio (LF/HF) were significantly lower, whereas the normalized high-frequency component was significantly higher among the nonsurvivors than among the survivors. A multiple logistic regression model identified LF/HF (odds ratio, 2.16; 95% confidence interval [CI], 1.18-3.97; P=.013) and LF% (odds ratio, 0.78; 95% CI, 0.69-0.88; P<.001) as independent variables that were able to predict inhospital mortality for patients with SAH in an ED. The receiver operating characteristic area for LF/HF in predicting inhospital mortality was 0.957 (95% CI, 0.914-1.000; P<.001), and the best cutoff points was 0.8 (sensitivity, 92.1%; specificity, 90.4%).
  
  
  CONCLUSIONS
  Power spectral analysis of the HRV is able to predict inhospital mortality for patients after SAH in an ED. A tilt in the sympathovagal balance toward depressed sympathovagal balance, as indicated by HRV analysis, might contribute to the poor outcome among these patients.
authors.affiliation: Department of Emergency Medicine, Chang Gung Memorial Hospital Linkou Branch, Chang Gung University College of Medicine, Tao-Yuan 333, Taiwan.
authors.forename: Te-Fa
authors.initials: TF
authors.lastname: Chiu
authors.forename: Chien-Cheng
authors.initials: CC
authors.lastname: Huang
authors.forename: Jiann-Hwa
authors.initials: JH
authors.lastname: Chen
authors.forename: Wei-Lung
authors.initials: WL
authors.lastname: Chen
mesh_terms: D004562:Electrocardiography; D004636:Emergency Service, Hospital; D005260:Female; D005583:Fourier Analysis; D006339:Heart Rate / Q000502:physiology*; D017052:Hospital Mortality; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D013345:Subarachnoid Hemorrhage / Q000401:mortality* / Q000503:physiopathology