title: Importance of body surface potential field representation fidelity: analysis of beat-to-beat repolarization measurements.
abstract: OBJECTIVE
  According to previous studies, the complex substrate of malignant arrhythmias needs a detailed spatio-temporal noninvasive characterization of low-amplitude dynamic changes in beat-to-beat cardiac repolarization.
  
  
  METHODS
  Body surface potential map (BSPM) records were taken on 14 healthy male and female subjects (age 20-80 years) and on 6 ventricular arrhythmia patients, 4 of them with implanted cardioverter defibrillators (ICD). Records were taken continuously, for 5 minutes, in resting, supine position. Beat-to-beat QRST integral maps, Karhunen-Loéve coefficient time-series (KLi, i=1-12), RR and nondipolarity index (NDI) time-series were computed.
  
  
  RESULTS
  The first order statistical properties of the spatio-temporal variability of subsequent QRST integral maps were characterized by the box and whiskers plot of their KLi components. The SD2/M2 (KLi amplitude variance/mean signal energy) values of the QRST integral maps in the normal group ranged between 0.0057 and 0.008 (i.e. 0.075=or<SD/M=or<0.089). In ICD patients SD2/M2 values went up to 0.021-0.069 (i.e: 0.14=or<SD/M=or<0.26). Autocorrelation functions revealed that while in normal subjects only 5-20% of the total power had white noise character, the rest was bandwidth-limited noise. In ICD patients the weight of white noise component increased considerably. The higher the SD/M relative KL variability, the higher and more frequent NDI spikes were.
  
  
  CONCLUSIONS
  Beat-to-beat dynamics of white noise components of high resolution BSPMs are able to stratify arrhythmia vulnerability. The temporal distribution of extreme NDI spike formations is random; the frequency is associated with the relative KL component noise levels.
authors.affiliation: Department of Information Systems, University of Pannonia, Veszprém, Hungary. kozmann@irt.vein.hu
authors.forename: György
authors.initials: G
authors.lastname: Kozmann
authors.forename: Kristóf
authors.initials: K
authors.lastname: Haraszti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018780:Body Surface Potential Mapping; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D010507:Periodicity; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014693:Ventricular Fibrillation / Q000175:diagnosis* / Q000503:physiopathology