Abstract 14246: Microstructural Remodeling in the Porcine Infarct Border Zone Measured by Diffusion Tensor and Late Gadolinium Enhancement MRI
Introduction - The infarct border zone (BZ) consists of a mixture of fibrotic scar and viable myocardium and is important in ventricular arrhythmogenesis. Late gadolinium enhanced (LGE) MRI can be used to identify infarct and BZ, but the magnitude of microstructural remodeling within the BZ is incompletely characterized. Diffusion tensor MRI (DT-MRI) evaluates microstructural remodeling by quantifying cellularity (increases with decreasing tensor trace), fibrosis (increases with decreasing fractional anisotropy, FA), and tissue mode (increase in fiber disarray with decreasing mode). Our objective was to quantify microstructural remodeling in the BZ using DT-MRI.
Methods - Porcine infarcts were made by balloon occlusion of the LCx (N1=4) or RCA (N2=1); or microbead obstruction of the LAD (N3=3). Gd-DTPA was injected (0.1mmol/kg) on week 8 and circulated for 15 minutes before sacrifice. Normal pigs (N=5) served as controls. Excised hearts were imaged with LGE MRI (0.33×0.33×0.33-0.50mm) and co-registered DT-MRI (1×1×3mm). Myocardium was segmented as remote, infarct, or BZ by LGE signal intensity thresholds. Medians and 95%-CIs of the DT measures were defined with bootstrapping. A bootstrapped analogue to repeated measures ANOVA was used to test for regional differences.
Results - Normal control and remote myocardium were not significantly different (Figure). The BZ significantly remodeled compared to both infarct and remote myocardium; and demonstrated a decrease in cellularity (trace↑), decrease in tissue organization (FA↓), and an increase in fiber disarray (mode↓) relative to remote myocardium (all p<0.01). Changes in the infarct were significantly larger (all p<0.01).
Conclusion - The BZ is characterized by significant microstructural remodeling that is distinct from both remote and infarcted myocardium. Further investigation of BZ remodeling may elucidate the microstructural requirements that foment ventricular arrhythmogenesis.
- © 2012 by American Heart Association, Inc.