MR study of the effect of infarct size and location on left ventricular functional and microstructural alterations in porcine models.

Purpose: To investigate the effect of Infarct size and location on left ventricular (LV) functional and microstructural alterations in well-established porcine models. Materials and Methods: Myocardium infarction was induced in mini-pigs at apical septum (Group 1, n = 6) or basal lateral wall (Group 2, n = 6) by permanent occlusion of the left anterior descending or left circumflex coronary artery, respectively. In vivo cardiac magnetic resonance (CMR) was performed 4 and 13 weeks later. Hearts were then excised and examined by ex vivo diffusion tensor imaging (DTI) for myocardium structural changes in infarct, adjacent and remote regions. Results: LV ejection fractions correlated negatively with infarct sizes. Between week 4 and 13, Group I exhibited more changes in end-systolic volume, LV mass, and ejection fraction, although It showed a smaller infarct volume percentage. Ex vivo results revealed the decreased water diffusion fractional anisotropy and increased diffusivities in infarct region in correlation with infarct size, but with no significant difference between the two groups. However, LV myocardial double-helical fiber architecture was found to alter in Group 1, shifting more towards left-handed direction as compared to controls. Conclusion: Postinfarct LV functional and structural remodeling is affected by both Infarct size and location.