title: Short-term variability of repolarization predicts ventricular tachycardia and sudden cardiac death in patients with structural heart disease: a comparison with QT variability index.
abstract: BACKGROUND
  Monitoring arrhythmic risk may improve management of patients with implantable cardioverter-defibrillators (ICD) and prevent ICD shocks. Changes in repolarization duration between subsequent beats quantified as short-term variability (STV) is associated with ventricular arrhythmias in several animal models.
  
  
  OBJECTIVE
  We evaluated STV of QT from right ventricular intracardiac ICD electrograms in patients with structural heart disease and compared its predictive value with the QT variability index (QTVI).
  
  
  METHODS
  In 233 patients, STV over 60 beats for QT and RR intervals and their ratio was calculated (STV(QT), STV(RR), STV(Ratio), respectively). QTVI was derived from mean and SD of QT and heart rate. Follow-up duration was 26 ± 15 months. Predictive value was determined for sudden arrhythmic death (SAD) defined as sudden cardiac death or fast ventricular tachycardia/fibrillation [CL < 240 ms].
  
  
  RESULTS
  In univariate analysis, STV(Ratio), but not STV(QT) or STV(RR), was predictive of SAD. Hazard ratios for highest quartile STV(Ratio) and QTVI were comparable (STV(Ratio): 1.9, 95% confidence interval [CI] 1.1 to 3.3, P = .038, QTVI: 2.2, 95% CI 1.2 to 3.8, P = .010). In a multivariate model, highest quartile STV(Ratio) was predictive of SAD after adjustment for New York Heart Association class, history of ischemia, ICD indication, and use of class I antiarrhythmics (hazard ratio 1.8, 95% CI 1.0 to 3.4, P < .050). A combined criterion of highest quartile for both STV(Ratio) and QTVI identified patients at highest risk (hazard ratio 2.4, 95% CI 1.3 to 4.3, P = .005, positive predictive value 38%, negative predictive value 82%).
  
  
  CONCLUSIONS
  STV(Ratio) from ICD electrograms is predictive of SAD. Predictive value is similar for order-based STV(Ratio) and distribution-based QTVI, but the combination of both parameters can further improve results.
authors.affiliation: Medtronic Bakken Research Center, Maastricht, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Oosterhoff
authors.forename: Larisa G
authors.initials: LG
authors.lastname: Tereshchenko
authors.forename: Marcel A G
authors.initials: MA
authors.lastname: van der Heyden
authors.forename: Raja N
authors.initials: RN
authors.lastname: Ghanem
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Fetics
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
authors.forename: Marc A
authors.initials: MA
authors.lastname: Vos
mesh_terms: D016757:Death, Sudden, Cardiac / Q000209:etiology* / Q000517:prevention & control; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000150:complications* / Q000503:physiopathology* / Q000517:prevention & control