Equivalent generator properties of acute ischemic lesions in the isolated rabbit heart

Abstract

Equivalent generator properties of the electrical field produced by ischemic myocardium were studied in 25 isolated rabbit heart preparations. Electrocardiograms from 32 electrodes deployed about a spherical tank containing the isolated, perfused heart were recorded before and after suture ligation of the left anterior descending artery. The ligation was high (10 preparations) or low (10 preparations) along the interventricular septum. In a final five hearts, ligatures were placed sequentially in both positions. Signals were processed to quantitate the percentage of summed square (SSQ) potential attributable to a centric dipole (CD), to a four-element centric multiple series (CMS) and to a single moving dipole (SMD) during the S-T segment. Fifteen minutes after low ligation, 74 ± 12%, 98 ± 1%, and 96 ± 3% (mean ± 1 SD) of SSQ potential recorded 10 msec into the S-T segment could be accounted for by the CD, CMS, and SMD models, respectively. The compound was determined to be fixed in location and orientation throughout the S-T segment but to increase in magnitude from early to late S-T. Dipole moment directly correlated with the area of the epicardial lesion (r = 0.82). Results were quantitatively similar after high ligation and after each of the sequential occlusions. Tank surface isopotential maps during the S-T segment uniformly demonstrated a single maximum that was spatially aligned with the ischemic lesion, and with an intensity proportional to both computed dipole moment and epicardial lesion size (r=0.97). Thus, CMS and SMD cardiac models provide quantitatively accurate descriptions of the experimentally induced electrical fields.