Transmural heterogeneity of left ventricular myocardium remodeling in postinfarct porcine model revealed by MR diffusion tensor imaging.

PURPOSE: To investigate the transmural heterogeneity of left ventricular myocardium structural remodeling.
MATERIALS AND METHODS: Ex vivo diffusion tensor imaging (DTI) was performed in six adult porcine heart samples with apical septum infarction collected 13 weeks after permanent left anterior descending coronary artery ligation and six age-matched intact controls. Alterations in diffusion indices and myocardial fiber orientation, including fractional anisotropy (FA), mean apparent diffusion coefficient (mean ADC), axial diffusivity (λ(∥) ), radial diffusivity (λ(⟂) ), and fiber helix angle were investigated at five transmural zones across myocardium wall in regions adjacent and remote to the infarct.
RESULTS: In both adjacent and remote regions of infarcted hearts, FA showed no significant alteration across transmural zones compared to controls. However, mean ADC, λ(∥) , and λ(⟂) exhibited significant decreases at endocardium zones but not epicardium zones. Moreover, myocardial fiber helix angle shifted towards left-handed orientation at all transmural zones, especially in regions adjacent to the infarct, becoming more aligned with the epicardium fiber orientation.
CONCLUSION: These experimental DTI findings indicate that the endocardium was more vulnerable to infarction, leading to more pronounced microstructural changes during remodeling. The current DTI approach reveals additional information in delineating postinfarct remodeling process, which may provide insights into cardiac mechanics and clinical assessment of cardiac diseases.