Myocardial salvage by T2W-CMR: direct comparison to a non-destructive, high resolution, 3-dimensional ex-vivo assessment of the area at risk simultaneous with infarction
© Van Assche et al; licensee BioMed Central Ltd. 2013
Published: 30 January 2013
The amount of myocardial salvage is a critical determinant of prognosis in acute myocardial infarction (AMI). T2W-CMR in combination with DE-CMR is thought to be a promising method that could presumably measure salvage. However, direct comparisons with the appropriate reference standard are limited. Additionally, even if a pathology reference standard is present, co-registration with in-vivo imaging is problematic. We recently validated a new ex-vivo CMR protocol against the reference standard of microspheres and TTC that provides 3D, non-destructive, high-resolution maps of the AAR simultaneously with infarction. Because this map delineates both the AAR and infarction, salvage can be easily measured in a single image, rather than being calculated from 2 datasets. Additionally, the 3D map allows for direct matching of in-vivo DE to ex-vivo CMR and thereby further minimizing the potential for misregistration from in-vivo DE and more importantly in-vivo T2. Therefore, we sought to compare in-vivo calculated salvage to the directly measured salvage by ex-vivo CMR.
12 canines underwent variable coronary occlusion of the LAD (45-75min) followed by reperfusion to create a range of myocardial salvage. CMR was performed 5-days post-AMI. T2W-CMR was performed using an optimized DIR-TSE sequence with reduced inter-echo spacing and significantly improved image homogeneity . Following in-vivo imaging, the 3D ex-vivo protocol was performed delineating viable AAR (dark), infarcted AAR (bright) and normal myocardium (grey). Ex-vivo CMR slices were directly matched to in-vivo DE images. In-vivo salvage was calculated by subtracting infarct size by DE from T2-hyperintensity size by TSE and expressed as a percentage of T2-hyperintensity size. For ex-vivo CMR, salvage was directly measured on the matched slices and expressed as a percentage of the AAR.
In-vivo calculated salvage did not correspond with directly measured salvage on matched ex-vivo slices. Instead, there was a strong correlation between in-vivo T2 size and ex-vivo scar size.
Funded in part by 5R01HL064726-07.
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