Post-Infarction Remodelling of Cardiac Muscle Assessed by Diffusion-Weighted MR Imaging and Histological Methods

Abstract

Cardiac magnetic resonance (MR) is a non-invasive imaging method that can be used to assess important alterations in the structure and function of the ischemic heart muscle. In this study, we used a pre-clinical swine model of chronic infarction generated by an occlusion-reperfusion method. The hearts from six animals were explanted at ∼5 weeks post-infarction, and imaged on a 1.5T GE SignaExcite magnet using a high-resolution DW-MRI method (voxel size 75%) as well as intermediate collagen density (25-75%, where fibrotic zones intermingled with viable myocytes), with the CS areas and PI areas, respectively, identified in MR images. Furthermore, to evaluate the changes in electrical function in the heterogeneously remodelled areas, we employed light micrographs of connexin Cx43 (which is responsible for cell-to-cell electrical coupling) prepared using imunohistochemistry methods, as well as fluorescence micrographs of Cx43. The analysis of fluorescence images demonstrated a disturbed pattern of gap junctions and a reduction of Cx43 density in the PI areas compared to areas selected from healthy myocardial tissue. The structural and functional remodelling of the cardiac muscle in the post-infarction period often underlie malignant arrhythmic events; therefore, the localization (particularly deep in the myocardium) and characterization of the CS and PI areas by means of a non-distructive way (such as DW-MR imaging) is extremely valuable.