title: Gender differences and risk of ventricular tachycardia or ventricular fibrillation.
abstract: BACKGROUND
  Healthy women have longer QT intervals and more drug-induced proarrhythmia compared to men, yet those given implantable cardioverter-difibrillators (ICDs) for ischemic cardiomyopathy have fewer episodes of ventricular tachycardia/ventricular fibrillation (VT/VF) than men. The role of repolarization duration and stability in arrhythmogenesis in men and women with structural heart disease has not been explored.
  
  
  OBJECTIVE
  The purpose of this study was to analyze repolarization differences between men and women and their relation to the risk of VT/VF.
  
  
  METHODS
  Multicenter Automatic Defibrillator Trial II study patients underwent 10-minute, resting digitized recordings at study entry. QT and heart rate were measured for each beat with a semiautomated method. QT variance was normalized for mean QT (QTVN) or for heart rate variance (QTVI). Spectral analysis of heart rate and QT time series was performed; coherence was indexed to quantify consistency of heart rate and QT power spectra. The incidence of VT/VF was determined by ICD interrogation.
  
  
  RESULTS
  There were 805 usable recordings (142 females); 463 received ICDs (86 females). There was no gender difference in mean or median QT, QTc, or heart rate. QTVN and QTVI were slightly (but significantly) higher, and the mean coherence was lower in women. In a Cox multivariate analysis, increased QTVN or QTVI (top quartile) was associated with a significantly higher risk for VT/VF in men (QTVN hazard ratio (HR) 2.2; confidence interval [CI] 1.4-3.4; P = .001; QTVI HR 1.9; CI 1.2-3.0; P = .006) but not in women, while reduced coherence (bottom quartile) predicted VT/VF in women (HR 3.3; CI 1.2-9.0; P = .021) but not in men.
  
  
  CONCLUSIONS
  In post-myocardial infarcation patients with depressed ejection fraction, both women and men manifest increased temporal variability in the QT interval. In men, QT variability by itself raised arrhythmic risk. In women, however, QT variability dissociated from HR variability (low coherence) appeared to be a uniquely significant predictor of arrhythmic events.
authors.affiliation: Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA. MCPH@aol.com
authors.forename: Mark C
authors.initials: MC
authors.lastname: Haigney
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Javed M
authors.initials: JM
authors.lastname: Nasir
authors.forename: Scott
authors.initials: S
authors.lastname: McNitt
authors.forename: Douglas
authors.initials: D
authors.lastname: McAdams
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Gentlesk
authors.forename: Robert E
authors.initials: RE
authors.lastname: Goldstein
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
mesh_terms: D000368:Aged; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D017180:Tachycardia, Ventricular / Q000503:physiopathology*; D014693:Ventricular Fibrillation / Q000503:physiopathology*