title: Dependence of temporal variability of ventricular recovery on myocardial fibrosis. Role of mechanoelectric feedback?
abstract: OBJECTIVE
  The study was aimed at establishing the effect of factors involved in the expression of mechanoelectric feedback in the heart, such as R-R interval and connective tissue, on time dependent changes in ventricular recovery, as determined at the body surface by beat to beat variability of QRST integral maps (BBV-IM).
  
  
  METHODS
  We used 15 normal 6-month-old Wistar rats. In each anesthetized animal, we performed a 3-minute continuous recording of 44. The simultaneous chest ECGs. The signals were interactively processed, 1) to determine mean R-R interval and R-R variability throughout the recording period and 2) to compute QRST integral maps from approximately 50 beats belonging to the end of expiration. Then BBV-IM was calculated and expressed as percentage of beats significantly differing from a template. At sacrifice, the amount of myocardial fibrosis was morphometrically evaluated.
  
  
  RESULTS
  R-R interval was 149 ms +/- 4, R-R interval variability 0.008 +/- 0.001 and BBV-IM 30.7% +/- 4.4. Myocardial fibrosis expressed as % volume of left ventricular myocardium, numerical density of fibrotic foci and average cross-sectional area of the foci was 3.0% +/- 0.4, 3.8 +/- 0.6 and 4.4 microns(2)/1000 +/- 0.1 respectively, BB-IM was positively correlated to the % volume of fibrosis (r = 0.83, P < 0.0003). Both measurements were positively correlated to R-R interval (BBV-IM: r = 0.83, P < 0.0001; % volume of fibrosis: r = 0.87, P < 0.001) and negatively correlated to cardiac weights (BBV-IM: r = -0.79, P < 0.0005; % volume of fibrosis: r = -0.75, P < 0.001).
  
  
  CONCLUSIONS
  Beat to beat changes in ventricular repolarization attributable to mechanoelectric transduction can be detected at the body surface by means of BBV-IM.
authors.affiliation: Dipartimento di Biologia Evolutiva e Funzionale-Sezione Fisiologia, Università degli Studi di Parma, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Stilli
authors.forename: B
authors.initials: B
authors.lastname: Aimi
authors.forename: A
authors.initials: A
authors.lastname: Sgoifo
authors.forename: P
authors.initials: P
authors.lastname: Ciarlini
authors.forename: G
authors.initials: G
authors.lastname: Regoliosi
authors.forename: C
authors.initials: C
authors.lastname: Lagrasta
authors.forename: G
authors.initials: G
authors.lastname: Olivetti
authors.forename: E
authors.initials: E
authors.lastname: Musso
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004594:Electrophysiology; D004719:Endomyocardial Fibrosis / Q000473:pathology / Q000503:physiopathology*; D005246:Feedback; D006339:Heart Rate; D008297:Male; D010063:Ovum; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology*