Abstract 217: Use of Magnetic Resonance Imaging Method For Quantification Of Myocardial Salvage In A Rat Model Of Ischemia-reperfusion Injury.

Abstract

Introduction: Quantification of myocardial “area-at-risk” (AAR) and infarct (MI) zone is critical for assessing novel therapies targeting myocardial ischemia-reperfusion (IR) injury. The current standard method involves perfusion with Evan’s Blue (EB), staining with TTC and manual slicing and analysis. We have developed an MRI method for quantifying MI and AAR in whole hearts which provides superior 3D resolution to the standard approach. Methods: Rats were given an IR injury, recovered for 24 hours then infused with Gd-DTPA via the tail vein. The coronary artery was then religated, and a solution containing both iron oxide microparticles and EB was infused. For comparison, hearts were then harvested and transversally sectioned for TTC staining. Some hearts were kept intact for MRI only analysis. Ex-vivo MRI T2* and T1 images were acquired on a 9.4T magnet. The AAR (red) was quantified by comparing the T2* signal loss in perfused regions (blue) and high T1-signal in infarcted zones (white) from Gd-DTPA retention. Results: MRI and EB/TTC measures on the same slice for both AAR and MI were highly correlated (r=0.92-0.94;p<0.05). 3D MRI acquisition and analysis of whole hearts reduced intra-observer variability, and automated segmentation and analysis further reduced inter-observer variation. Conclusion: This novel MRI technique allows precise assessment of infarct and AAR zones and is highly suited to automation of both analysis and acquisition. This method could remove the need for tissue slicing, and via a centralised MRI facility, could permit 3D digital analysis of hearts at high anatomical resolution, accessible for all laboratories already performing IR experiments.