title: The effect of obstructive sleep apnea on QRS complex morphology.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) has been reported to be associated with an increased risk of ventricular arrhythmias and conduction disturbances. The aim of this study was to analyze the QRS complex morphology potentially indicative of intraventricular conduction impairment in patients with mild to severe OSA.
  
  
  METHODS
  One hundred ninety-three consecutive patients, who underwent complete overnight polysomnography, were divided into four groups based on the OSA severity: (1) no OSA, (2) mild OSA, (3) moderate OSA and (4) severe OSA (apnea-hypopnea index <5, 5-15, 15-30, >30/h, respectively). Resting 12-lead ECG was recorded, the QRS parameters included QRS amplitude in individual leads, QRS spatial vector magnitude (QRSmax), electrical axis (EA), ECG criteria for left ventricular hypertrophy (ECG-LVH) and right ventricular hypertrophy (ECG-RVH), and occurrence of fragmented QRS (fQRS).
  
  
  RESULTS
  Severity of OSA was significantly associated with a gradual significant shift of the electrical axis to the left (45.5±22.5°; 34.8±17.1°; 32.9±18.2°; 29.8±10.0°; respectively), while the QRSmax values were low in all patient groups, with a significant difference between no OSA and severe OSA groups. The multivariate analysis showed that QRSmax was independently associated with age and the interaction between gender and OSA severity (p=0.001, and p=0.004, respectively; adjusted R(2)=0.178). The electrical axis was found to be independently associated with age and OSA severity (p=0.037, and p=0.026, respectively; R(2)=0.109). Changes of electrical axis and of QRSmax were reflected in corresponding changes in the amplitude of 12-lead ECG and in low occurrence of ECG-LVH and ECG-RVH criteria. The OSA groups had higher occurrence of fQRS.
  
  
  CONCLUSIONS
  OSA patients displayed a combination of changes in QRS complex morphology, the leftward shift of EA, low QRS voltage and fQRS, suggestive of depolarization sequence deterioration that might be indicative of considerable electrical remodeling.
authors.affiliation: International Laser Center, Bratislava, Slovakia; Institute of Pathological Physiology, Medical Faculty, Comenius University, Bratislava, Slovakia. Electronic address: bacharova@ilc.sk.
authors.forename: Ljuba
authors.initials: L
authors.lastname: Bacharova
authors.affiliation: Institute of Pathological Physiology, Medical Faculty, Comenius University, Bratislava, Slovakia.
authors.forename: Epameinondas
authors.initials: E
authors.lastname: Triantafyllou
authors.affiliation: Institute of Pathological Physiology, Medical Faculty, Comenius University, Bratislava, Slovakia.
authors.forename: Christos
authors.initials: C
authors.lastname: Vazaios
authors.affiliation: Department of Respiratory Medicine, Faculty of Medicine, P.J. Safarik University, Kosice, Slovakia; L. Pasteur University Hospital, Kosice, Slovakia.
authors.forename: Ivana
authors.initials: I
authors.lastname: Tomeckova
authors.affiliation: Department of Respiratory Medicine, Faculty of Medicine, P.J. Safarik University, Kosice, Slovakia.
authors.forename: Ivana
authors.initials: I
authors.lastname: Paranicova
authors.affiliation: Department of Respiratory Medicine, Faculty of Medicine, P.J. Safarik University, Kosice, Slovakia; L. Pasteur University Hospital, Kosice, Slovakia.
authors.forename: Ruzena
authors.initials: R
authors.lastname: Tkacova
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000002:abnormalities* / Q000503:physiopathology; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000209:etiology / Q000503:physiopathology; D017380:Hypertrophy, Right Ventricular / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000503:physiopathology
keywords: Electrical axis; Fragmented QRS complex; QRS complex; QRS voltage; Sleep apnea