title: The effect of sleep apnea on QT interval, QT dispersion, and arrhythmias.
abstract: BACKGROUND
  QT interval (QT) and QT dispersion (QTd) are electrocardiograph (ECG) parameters for the evaluation of myocardial repolarization. The inhomogeneity of ventricular repolarization is associated with ventricular arrhythmias. An increased QT, QTd, and increased incidence of nocturnal cardiac rhythm disturbances have been described in patients with obstructive sleep apnea (OSA), while other investigators did not find a relationship between ventricular arrhythmias and OSA.
  
  
  OBJECTIVE
  The aim of this study was to examine the occurrence of ventricular arrhythmias and to measure QT parameters in patients with untreated OSA using an ambulatory Holter-ECG.
  
  
  METHODS
  A total of 25 patients with untreated OSA were studied. After routine biochemical investigation and 2-dimensional, M-mode echocardiography, a 24-hour Holter-ECG was recorded to detect cardiac arrhythmias and QT parameters. QT parameters were measured by the QT Guard system.
  
  
  RESULTS
  Only the QT interval increased significantly during the nighttime period (nocturnal QT interval: 423.1 +/- 34.6 ms, daytime QT interval: 381.6 +/- 33.8 ms, 24-hour QT interval: 394.7 +/- 31.1 ms). However, during the nighttime QT interval (422.8 +/- 14.9 ms), QTd (31.2 +/- 11.0 ms) and QT dispersion (30.5 +/- 10.2 ms) did not show any change compared to 24-hour (QTc interval: 423.7 +/- 14.2 ms, QTd: 28.8 +/- 9.4 ms, QTcd: 30.5 +/- 9.43 ms) and daytime levels (QTc interval: 423.9 +/- 14.3 ms, QTd: 27.3 +/- 10.7 ms, QTcd: 29.9 +/- 11.1 ms). None of the patients had ventricular arrhythmias.
  
  
  CONCLUSIONS
  QTd and QTcd did not increase during the nighttime period. Our study did not show an increased risk of ventricular arrhythmias in this population during the monitoring period.
authors.affiliation: First Department of Internal Medicine, Medical and Health Science Center, University of Debrecen, Hungary. bartakitti@gmail.com
authors.forename: Kitti
authors.initials: K
authors.lastname: Barta
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szabó
authors.forename: Csaba
authors.initials: C
authors.lastname: Kun
authors.forename: Csaba
authors.initials: C
authors.lastname: Munkácsy
authors.forename: Orsolya
authors.initials: O
authors.lastname: Bene
authors.forename: Mária Tünde
authors.initials: MT
authors.lastname: Magyar
authors.forename: László
authors.initials: L
authors.lastname: Csiba
authors.forename: István
authors.initials: I
authors.lastname: Lörincz
mesh_terms: D000200:Action Potentials; D000328:Adult; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D002940:Circadian Rhythm; D004452:Echocardiography; D015716:Electrocardiography, Ambulatory; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D018570:Risk Assessment; D012307:Risk Factors; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology