title: Prediction of early secondary complications in patients with spontaneous subarachnoid hemorrhage based on accelerated sympathovagal ratios.
abstract: OBJECTIVE
  The development of secondary complications following spontaneous subarachnoid hemorrhage (SAH) largely depends on sympathetic overexcitation. The roles of vagal activities, however, are poorly defined. Because both components of the autonomic nervous system can be explored in the frequency domain of heart rate variability (HRV), the present study aimed to determine the dynamic evolution of autonomic activities and to identify patients at high risk for complications following hemorrhage.
  
  
  METHODS
  Thirty patients with SAH were enrolled in our study. Those who suffered from symptomatic vasospasm, cerebral infarction, neurogenic pulmonary edema, or early mortality within 1 week of ictus were categorized into the complication group. Spectral analysis of HRV explored three important indices of sympathetic and vagal modulations: low-frequency (LF), high-frequency (HF), and LF/HF ratios. Patterns of HRV dynamics within the first 3 days were compared between complication and non-complication groups. The group trends, estimated by the slopes of HRV changes, were determined for further univariate and multivariate analysis.
  
  
  RESULTS
  Our study showed that daily HRV in the complication group exhibited an approximately 2.7-fold increase of sympathovagal ratio (denoted by LF/HF). This resulted from reciprocal changes of sympathoexcitation (LF) and vagal withdrawal (HF). Multivariate analysis revealed that LF/HF slope, an indicator of the trend of sympathovagal change, was an independent variable significantly associated with the development of complications.
  
  
  CONCLUSIONS
  This study confirmed that during early SAH period, patients with and without complications presented different patterns of sympathovagal changes. LF/HF slope during the first 3 days was a significant predictor of secondary complications after SAH.
authors.affiliation: Department of Surgery, Cathay General Hospital, Taipei, Taiwan.
authors.forename: I-Chang
authors.initials: IC
authors.lastname: Su
authors.forename: Chien-Hsun
authors.initials: CH
authors.lastname: Li
authors.forename: Kuo-Chuan
authors.initials: KC
authors.lastname: Wang
authors.forename: Dar-Ming
authors.initials: DM
authors.lastname: Lai
authors.forename: Sheng-Jean
authors.initials: SJ
authors.lastname: Huang
authors.forename: Jiann-Shing
authors.initials: JS
authors.lastname: Shieh
authors.forename: Yong-Kwang
authors.initials: YK
authors.lastname: Tu
mesh_terms: D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology*; D001342:Autonomic Nervous System Diseases / Q000175:diagnosis / Q000209:etiology; D002544:Cerebral Infarction / Q000150:complications; D006321:Heart / Q000294:innervation / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D011237:Predictive Value of Tests; D011654:Pulmonary Edema / Q000150:complications; D013345:Subarachnoid Hemorrhage / Q000150:complications*; D020421:Vagus Nerve Diseases / Q000175:diagnosis / Q000209:etiology; D020301:Vasospasm, Intracranial / Q000150:complications