title: Increased myocardial vulnerability and autonomic nervous system imbalance in obstructive sleep apnea syndrome.
abstract: BACKGROUND
  Obstructive sleep apnea syndrome (OSAS) is characterized by the repeated episodes of upper airway obstruction during sleep, leading to significant hypoxia. Noninvasive evaluation of autonomic nervous system (ANS) and myocardial vulnerability may help determination of OSAS patients who are under high risk of malignant cardiac arrhythmias. The aim of this study was to show the effects of OSAS on predictors of arrhythmias by the evaluation of heart rate turbulence (HRT), heart rate variability (HRV) and QT dynamicity reflecting the ANS balance and myocardial vulnerability.
  
  
  METHODS
  After polysomnographic study, 80 patients with OSAS and 55 age matched OSAS (-) subjects were included in the study. Twenty-four-hour Holter monitoring was performed in all subjects. HRT, HRV and QT dynamicity parameters were calculated.
  
  
  RESULTS
  Turbulence slope was significantly decreased in OSAS patients whereas turbulence onset was increased (P<0.001). QT/RR slopes were significantly increased for QT end and QT apex (P<0.001). In HRV analysis, autonomic balance changed in favor of sympathetic system at night in OSAS patients. Furthermore, HRT and QT dynamicity parameters are found to be correlated with Apnea-Hypopnea Index (AHI).
  
  
  CONCLUSIONS
  OSAS is associated with a significant worsening in HRV, HRT, and QT dynamicity parameters. Our results may indicate that HRV and QT dynamicity parameters can be useful noninvasive methods that may detect autonomic nervous system activity and ventricular vulnerability in OSAS.
authors.affiliation: Department of Cardiology, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: Kudret
authors.initials: K
authors.lastname: Aytemir
authors.forename: Ali
authors.initials: A
authors.lastname: Deniz
authors.forename: Bunyamin
authors.initials: B
authors.lastname: Yavuz
authors.forename: Ahmet
authors.initials: A
authors.lastname: Ugur Demir
authors.forename: Levent
authors.initials: L
authors.lastname: Sahiner
authors.forename: Orcun
authors.initials: O
authors.lastname: Ciftci
authors.forename: Lale
authors.initials: L
authors.lastname: Tokgozoglu
authors.forename: Iknur
authors.initials: I
authors.lastname: Can
authors.forename: Altay
authors.initials: A
authors.lastname: Sahin
authors.forename: Ali
authors.initials: A
authors.lastname: Oto
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000209:etiology; D001341:Autonomic Nervous System / Q000503:physiopathology*; D002940:Circadian Rhythm; D015716:Electrocardiography, Ambulatory; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011379:Prognosis; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014463:Ultrasonography