Analysis of the Geometry of Myocardial Infarct Size Reduction with Hyaluronidase

Abstract

Although several drugs have been shown to reduce myocardial infarct size the exact location where myocardial salvage occurs remains controversial. In order to study this problem, anesthetized open-chest dogs were randomized into 10 control and 8 treated animals which received hyaluronidase (500 N F unitslkg, iv) 15 min, 2 hr, and 24 hr after occlusion of the left anterior descending coronary artery. Twenty-one days after occlusion, the hearts were excised, divided into 1-cm-thick slices, and incubated in triphenyl tetrazolium chloride, and scar size was determined by planimetry. The distance along the circumference (DAC) of the endocardium, midmyocardium, and epicardium which was composed of scar tissue was measured in each slice below the site of occlusion and mean DACs were calculated for each dog, In untreated dogs DACs were composed of scar along the endo-, mid-, and epicardium which were 2.6 * 0.3, 3.1. * 0.4, and 3.6 * 0.5 cm, respectively, compared to hyaluronidase-treated dogs in which the DACs along the endo-, mid-, and epicardium were 1.3 ? 0.3 cm (P < 0.02) compared to control; 1.6 ? 0.4 cm (P < 0.02); and 0.8 2 0.4 cm (P < 0.001), respectively. Hence, although the infarct reduction was greatest in the epicardial region, there was also reduction in the endocardial and midmyocardial regions. Thus, scar size reduction with hyaluronidase occurs in both lateral and epicardial directions. 141 0037-9727/80/090 14 1-06$0 1 .OO/O