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 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 μm²/1000±0.1 respectively. BBV-IM was positively correlated to the % volume of fibrosis (r = 0.81, Pr = 0.83, Pr = 0.87, Pr = −0.79, Pr = −0.75, PConclusion: Beat to beat changes in ventricular repolarization attributable to mechanoelectric transduction can be detected at the body surface by means of BBV-IM.