Abstract
Myocardial infarction (MI) remains a leading cause of heart failure, yet the relationship between functional decline and structural remodeling is not fully defined. This study evaluated how echocardiographic parameters correspond with stereological measures of myocardial tissue in a rabbit MI model. Sixteen male New Zealand White rabbits were initially enrolled (MI, n = 12; sham, n = 4). Following two perioperative deaths, fourteen animals completed the study (MI, n = 10; sham, n = 4). MI was induced by permanent ligation of the left circumflex artery. Echocardiography (B-mode, M-mode, Doppler) was performed at baseline, immediately after surgery, and at 3 and 6 weeks (sham animals at baseline and post-surgery only). After 6 weeks, stereological analysis quantified cardiomyocyte, connective tissue, and vascular volumes globally and within infarct regions. MI rabbits showed directional trends toward ventricular dilation, wall thinning, and reductions in ejection fraction and fractional shortening, with a significant decline in early transmitral filling velocity (E-wave, p < 0.05). Global stereological analysis revealed no significant differences between MI and sham groups, but regional assessment suggested trends toward localized fibrosis, cardiomyocyte loss, and microvascular rarefaction in infarcted areas. Echocardiography sensitively detects early post-infarction functional impairment, whereas global stereology may underestimate structural remodeling. Regional stereological evaluation provides additional insight, highlighting the value of combining functional imaging with quantitative tissue analysis in experimental MI.