Effects of early and later reperfusion on healing speed of experimental myocardial infarct
Miura, T.; Shizukuda, Y.; Ogawa, S.; Ishimoto, R.; IImura, O.
Canadian Journal of Cardiology 7(3): 146-154
1991
ISSN/ISBN: 0828-282X PMID: 2044018 Document Number: 373953
The effects of reperfusion on myocardial infarct healing in the rabbit were analyzed using two morphometric indexes: the ratio of the volume of the organized portion of infarct to the volume of the whole infarct (%O/I), and the ratio of the minimal thickness of the infarct zone to the normal zone thickness (thinning ratio). In the nonreperfused infarcts, %O/I increased from 43.8 .+-. 3.1% (mean .+-. SEM) at 48 h to 85.7 .+-. 2.5% at seven days, which supported the validity of this index. The thinning ratio was 0.50 .+-. 0.03 at 48 h and did not change during the following five days. In other groups of rabbits, the coronary artery was temporarily occluded for 30 mins (early reperfusion) or 60 mins (late reperfusion), and the hearts were analyzed at 72 h or seven days. Early reperfusion limited infarct size as a percentage of the area at risk (%I/AAR) by approximately 50%, but late reperfusion did not. In both nonreperfused and reperfused infarcts, %O/I correlated significantly with absolute infarct size. Furthermore, the regression lines of the relationship of infarct size to %O/I of early and late reperfused infarcts shifted towards higher %O/I values compared with that of nonreperfused infarcts at seven days, which suggested accelerated organization. However, such a regression line shift by reperfusion was not detected at 72 h after infarction. The thinning ratio was higher in early reperfused infarcts compared to nonreperfused or late reperfused infarcts, and there was a weak inverse correlation between thinning ratio and %I/AAR when the data of reperfused and nonreperfused infarcts were pooled. Thus, both early and late reperfusion accelerate infarct organization independent of their effects on infarct size. However, thinning of the infarcted wall was attenuated only by reperfusion early enough to salvage a substantial mass of ischemic myocardium.