title: Modeling and quantification of repolarization feature dependency on heart rate.
abstract: BACKGROUND
  This article is part of the Focus Theme of Methods of Information in Medicine on "Biosignal Interpretation: Advanced Methods for Studying Cardiovascular and Respiratory Systems".
  
  
  OBJECTIVE
  This work aims at providing an efficient method to estimate the parameters of a non linear model including memory, previously proposed to characterize rate adaptation of repolarization indices.
  
  
  METHODS
  The physiological restrictions on the model parameters have been included in the cost function in such a way that unconstrained optimization techniques such as descent optimization methods can be used for parameter estimation. The proposed method has been evaluated on electrocardiogram (ECG) recordings of healthy subjects performing a tilt test, where rate adaptation of QT and Tpeak-to-Tend (Tpe) intervals has been characterized.
  
  
  RESULTS
  The proposed strategy results in an efficient methodology to characterize rate adaptation of repolarization features, improving the convergence time with respect to previous strategies. Moreover, Tpe interval adapts faster to changes in heart rate than the QT interval.
  
  
  CONCLUSIONS
  In this work an efficient estimation of the parameters of a model aimed at characterizing rate adaptation of repolarization features has been proposed. The Tpe interval has been shown to be rate related and with a shorter memory lag than the QT interval.
authors: Ana Minchole, Department of Computer Science, University of Oxford, Wolfson Building, Parks Road, Oxford, OX1 3QD, United Kingdom, E-mail: ana.minchole@cs.ox.ac.uk.
authors: A
authors: A
authors: Minchole
authors: E
authors: E
authors: Zacur
authors: E
authors: E
authors: Pueyo
authors: P
authors: P
authors: Laguna
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology*; D017711:Nonlinear Dynamics; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D018667:Tilt-Table Test
keywords: QT interval; Rate adaptation; T-peak to T-end