title: Validation of ECG indices of ventricular repolarization heterogeneity: a computer simulation study.
abstract: BACKGROUND
  Repolarization heterogeneity (RH) is functionally linked to dispersion in refractoriness and to arrhythmogenicity. In the current study, we validate several proposed electrocardiogram (ECG) indices for RH: T-wave amplitude, -area, -complexity, and -symmetry ratio, QT dispersion, and the Tapex-end interval (the latter being an index of transmural dispersion of the repolarization (TDR)).
  
  
  RESULTS
  We used ECGSIM, a mathematical simulation model of ECG genesis in a human thorax, and varied global RH by increasing the standard deviation (SD) of the repolarization instants from 20 (default) to 70 msec in steps of 10 msec. T-wave amplitude, -area, -symmetry, and Tapex-end depended linearly on SD. T-wave amplitude increased from 275 +/- 173 to 881 +/- 456 muV, T-wave area from 34 x 10(3)+/- 21 x 10(3) to 141 x 10(3)+/- 58 x 10(3)muV msec, T-wave symmetry decreased from 1.55 +/- 0.11 to 1.06 +/- 0.23, and Tapex-end increased from 84 +/- 17 to 171 +/- 52 msec. T-wave complexity increased initially but saturated at SD = 50 msec. QT dispersion increased modestly until SD = 40 msec and more rapidly for higher values of SD. TDR increased linearly with SD. Tapex-end increased linearly with TDR, but overestimated it.
  
  
  CONCLUSIONS
  T-wave complexity did not discriminate between differences in larger RH values. QT dispersion had low sensitivity in the transitional zone between normal and abnormal RH. In conclusion, T-wave amplitude, -area, -symmetry, and, with some limitations, Tapex-end and T-wave complexity reliably reflect changes in RH.
authors.affiliation: Department of Cardiology, Leiden University Medical Center, The Netherlands.
authors.forename: Bart Hooft
authors.initials: BH
authors.lastname: Van Huysduynen
authors.forename: Cees A
authors.initials: CA
authors.lastname: Swenne
authors.forename: Harmen H M
authors.initials: HH
authors.lastname: Draisma
authors.forename: M Louisa
authors.initials: ML
authors.lastname: Antoni
authors.forename: Hedde
authors.initials: H
authors.lastname: Van De Vooren
authors.forename: Ernst E
authors.initials: EE
authors.lastname: Van Der Wall
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Schalij
mesh_terms: D003198:Computer Simulation; D004562:Electrocardiography; D006329:Heart Conduction System / Q000502:physiology* / Q000503:physiopathology; D006801:Humans; D008133:Long QT Syndrome / Q000503:physiopathology; D008955:Models, Cardiovascular; D016276:Ventricular Function