Dependence of temporal variability of ventricular recovery on myocardial fibrosis. role of mechanoelectric feedback?

• Published in: Cardiovascular research 1998, Vol.37 (1), p.58-65
• Main Authors: STILLI, D, AIMI, B, SGOIFO, A, CIARLINI, P, REGOLIOSI, G, LAGRASTA, C, OLIVETTI, G, MUSSO, E
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Biological and medical sciences; Electrocardiography. Vectocardiography; Electrodiagnosis. Electric activity recording; Electrophysiology; Endomyocardial Fibrosis - pathology; Endomyocardial Fibrosis - physiopathology; Feedback; Heart Rate; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Ovum; Rats; Rats, Wistar; Time Factors; Ventricular Function, Left - physiology
• ISSN: 0008-6363; 1755-3245
• DOI: 10.1016/S0008-6363(97)00221-6

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). 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. 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). Beat to beat changes in ventricular repolarization attributable to mechanoelectric transduction can be detected at the body surface by means of BBV-IM.