title: A study on stability analysis of atrial repolarization variability using ARX model in sinus rhythm and atrial tachycardia ECGs.
abstract: BACKGROUND
  The interaction between the PTa and PP interval dynamics from the surface ECG is seldom explained. Mathematical modeling of these intervals is of interest in finding the relationship between the heart rate and repolarization variability.
  
  
  OBJECTIVE
  The goal of this paper is to assess the bounded input bounded output (BIBO) stability in PTa interval (PTaI) dynamics using autoregressive exogenous (ARX) model and to investigate the reason for causing instability in the atrial repolarization process.
  
  
  METHODS
  Twenty-five male subjects in normal sinus rhythm (NSR) and ten male subjects experiencing atrial tachycardia (AT) were included in this study. Five minute long, modified limb lead (MLL) ECGs were recorded with an EDAN SE-1010 PC ECG system. The number of minute ECGs with unstable segments (Nus) and the frequency of premature activation (PA) (i.e. atrial activation) were counted for each ECG recording and compared between AT and NSR subjects.
  
  
  RESULTS
  The instability in PTaI dynamics was quantified by measuring the numbers of unstable segments in ECG data for each subject. The unstable segments in the PTaI dynamics were associated with the frequency of PA. The presence of PA is not the only factor causing the instability in PTaI dynamics in NSR subjects, and it is found that the cause of instability is mainly due to the heart rate variability (HRV).
  
  
  CONCLUSIONS
  The ARX model showed better prediction of PTa interval dynamics in both groups. The frequency of PA is significantly higher in AT patients than NSR subjects. A more complex model is needed to better identify and characterize healthy heart dynamics.
authors.affiliation: Department of Biomedical Engineering, Vel Tech MultiTech, Chennai, India. Electronic address: mountshiva@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Sivaraman
authors.affiliation: Department of Instrumentation and Control Engineering, National Institute of Technology, Tiruchirappalli, India.
authors.forename: G
authors.initials: G
authors.lastname: Uma
authors.affiliation: School of Engineering, University of Hull, Hull, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Langley
authors.affiliation: Department of Instrumentation and Control Engineering, National Institute of Technology, Tiruchirappalli, India.
authors.forename: M
authors.initials: M
authors.lastname: Umapathy
authors.affiliation: Department of Cardiology, Madras Medical College, Rajiv Gandhi Government General Hospital, Chennai, India.
authors.forename: S
authors.initials: S
authors.lastname: Venkatesan
authors.affiliation: Department of Instrumentation and Control Engineering, National Institute of Technology, Tiruchirappalli, India.
authors.forename: G
authors.initials: G
authors.lastname: Palanikumar
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004562:Electrocardiography; D006325:Heart Atria; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D013610:Tachycardia / Q000503:physiopathology*; D055815:Young Adult
keywords: Atrial repolarization dynamics; BIBO stability; Heart rate variability; PTa interval (PTaI); Premature activation