DEPENDENCE OF TEMPORAL VARIABILITY OF VENTRICULAR RECOVERY ON MYOCARDIAL FIBROSIS - ROLE OF MECHANOELECTRIC FEEDBACK

Objective: The study was aimed at establishing the effect of factors i nvolved in the expression of mechanoelectric feedback in the heart, su ch as R-R interval and connective tissue, on time dependent changes in ventricular recovery, as determined at the body surface by beat to be at variability of QRST integral maps (BBV-IM). Methods: We used 15 nor mal B-month-old Wistar rats. In each anesthetized animal, we performed a 3-minute continuous recording of 44 simultaneous chest ECGs. The si gnals 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 amou nt of myocardial fibrosis was morphometrically evaluated. Results: R-R interval was 149 ms +/- 4, R-R interval variability 0.008 +/- 0.001 a nd BBV-IM 30.7% +/- 4.4. Myocardial fibrosis expressed as % volume of left ventricular myocardium, numerical density of fibrotic foci and av erage cross-sectional area of the foci was 3.0% +/- 0.4, 3.8 +/- 0.6 a nd 4.4 mu m(2)/1000 +/- 0.1 respectively. BBV-IM was positively correl ated to the % volume of fibrosis (r = 0.81, P < 0.0003). Both measurem ents were positively correlated to R-R interval (BBV-IM: r = 0.83, P < 0.0001; % volume of fibrosis: r = 0.87, P < 0.0001) and negatively co rrelated to cardiac weights (BBV-IM: r = -0.79, P < 0.0005; % volume o f fibrosis: r = -0.75, P < 0.001). Conclusion: Beat to beat changes in ventricular repolarization attributable to mechanoelectric transducti on can be detected at the body surface by means of BBV-IM. (C) 1998 El sevier Science B.V.