JOURNAL OF SURGICAL RESEARCH 50, 30-39 (1991) Effects of lschemia on Epicardial Segment Shortening’

To evaluate the effects of nontransmural ischemia on epicardial contractile function, we implanted sonomi-crometers in 15 open-chest, anesthetized (halothane) dogs. One cylindrical crystal (radiating ultrasound 360”) was used as a transmitter for three conventional flat plate crystals arrayed to measure epicardial seg-ment shortening along three different axes that were deviated 0 ” (parallel), 45 ” (oblique), and 90 ” (perpen-dicular) from surface fiber orientation in the anterior-apical or posterior-basal left ventricle. During baseline conditions, epicardial shortening was maximal parallel with fiber orientation. Shortening decreased in a non-linear manner as deviation from fiber orientation in-creased, but there were significant differences between the two left ventricular regions suggesting that more substantial lateral strain occurs in the anterior-apical than the posterior-basal area. During coronary inflow restriction, changes in epicardial segment shortening also varied greatly depending on location and align-ment. At levels of wall thickening impairment asso-ciated with normal subepicardial perfusion, changes in epicardial function were restricted to the segments aligned perpendicular to fiber orientation whereas the parallel and oblique segments displayed moderate dys-function or none at all. Thus, transmural tethering mod-ifies epicardial segmental motion during coronary in-flow restriction, but the severity of the influence de-pends on the alignment and location of the epicardial measurements. 0 1991 Academic Press, Inc