Closed-chest animal model of chronic coronary artery stenosis. Assessment with magnetic resonance imaging

Abstract

To evaluate the consequences of chronic non-occlusive coronary artery (CA) stenosis on myocardial function, perfusion and viability, we developed a closed-chest, closed-pericardium pig model, using magnetic resonance imaging (MRI) as quantitative imaging tool. Pigs underwent a percutaneous copper-coated stent implantation in the left circumflex CA (n = 19) or sham operation (n = 5). To evaluate the occurrence of myocardial infarction, cardiac troponin I (cTnI) levels were repetitively measured. At week 6, CA stenosis severity was quantified with angiography and cine, first-pass and contrast-enhanced MRI were performed to evaluate cardiac function, perfusion and viability. In the stenting group, cTnI values significantly increased at day 3 and day 5 (P = 0.01), and normalized at day 12. At angiography, 13/19 stented pigs had a stenosis >75%. Mean degree of CA stenosis was 91 +/- 4%, range 83-98%. At contrast-enhanced MRI, mean infarct size was 7 +/- 6%, range 0.7-18.4%. Five of the 6 pigs with stenosis <75% had no infarction. Stented pigs showed significantly higher Left-ventricular volumes and normalized mass (P < 0.05), and lower ejection fraction (P = 0.03) than the sham pigs. Both wall thickening and myocardial perfusion were significantly lower in animals with at least one segment >50% infarct (23 +/- 8%; 0.05 +/- 0.01 a.u./s) and animals with only <50% infarct segments (29% +/- 12%; 0.07 +/- 0.02 a.u./s), than sham pigs (52 +/- 6%; 0.10 +/- 0.03 a.u./s) (P < 0.001; P < 0.05). This minimally-invasive animal model of chronic, non-occlusive CA stenosis, presenting a mixture of perfusion and functional impairment and a variable degree of myocardial necrosis, can be used as substitute to study chronic myocardial hypoperfusion.