title: T Wave Amplitude Correction of QT Interval Variability for Improved Repolarization Lability Measurement.
abstract: OBJECTIVE
  The inverse relationship between QT interval variability (QTV) and T wave amplitude potentially confounds QT variability assessment. We quantified the influence of the T wave amplitude on QTV in a comprehensive dataset and devised a correction formula.
  
  
  METHODS
  Three ECG datasets of healthy subjects were analyzed to model the relationship between T wave amplitude and QTV. To derive a generally valid correction formula, linear regression analysis was used. The proposed correction formula was applied to patients enrolled in the Evaluation of Defibrillator in Non-Ischemic Cardiomyopathy Treatment Evaluation trial (DEFINITE) to assess the prognostic significance of QTV for all-cause mortality in patients with non-ischemic dilated cardiomyopathy.
  
  
  RESULTS
  A strong inverse relationship between T wave amplitude and QTV was demonstrated, both in healthy subjects (R (2) = 0.68, p < 0.001) and DEFINITE patients (R (2) = 0.20, p < 0.001). Applying the T wave amplitude correction to QTV achieved 2.5-times better group discrimination between patients enrolled in the DEFINITE study and healthy subjects. Kaplan-Meier estimator analysis showed that T wave amplitude corrected QTVi is inversely related to survival (p < 0.01) and a significant predictor of all-cause mortality.
  
  
  CONCLUSIONS
  We have proposed a simple correction formula for improved QTV assessment. Using this correction, predictive value of QTV for all-cause mortality in patients with non-ischemic cardiomyopathy has been demonstrated.
authors.affiliation: Institute of Biomedical Engineering, Technische Universität Dresden Dresden, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: School of Electrical and Electronic Engineering, The University of Adelaide Adelaide, SA, Australia.
authors.forename: Mathias
authors.initials: M
authors.lastname: Baumert
authors.affiliation: Institute of Biomedical Engineering, Technische Universität Dresden Dresden, Germany.
authors.forename: Hagen
authors.initials: H
authors.lastname: Malberg
authors.affiliation: Institute of Biomedical Engineering, Technische Universität Dresden Dresden, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Zaunseder
keywords: DEFINITE; ECG; QT interval variability; T wave amplitude; risk stratification