Relationship of T2-Weighted MRI Myocardial Hyperintensity and the Ischemic Area-At-Risk
Rationale: Following acute myocardial infarction (MI), delineating the 'area-at-risk' (AAR) is crucial for measuring how much, if any, ischemic myocardium has been salvaged. T2-weighted-MRI is promoted as an excellent method to delineate the AAR. However, the evidence supporting the validity of this method to measure the AAR is indirect, and it has never been validated with direct anatomic measurements.
Objective: To determine if T2-weighted-MRI delineates the AAR.
Methods and Results: Twenty-one canines and twenty-four patients with acute MI were studied. We compared bright-blood and black-blood T2-weighted-MRI with images of the AAR and MI by histopathology in canines and with MI by in vivo delayed-enhancement-MRI in canines and patients. Abnormal regions on MRI and pathology were compared by (a) quantitative measurement of the transmural-extent of the abnormality and (b) picture matching of contours. We found no relationship between the transmural-extent of T2-hyperintense regions and that of the AAR (bright-blood-T2: r=0.06, p=0.69; black-blood-T2: r=0.01, p=0.97). Instead, there was a strong correlation with that of infarction (bright-blood-T2: r=0.94, p<0.0001; black-blood-T2: r=0.95, p<0.0001). Additionally, contour analysis demonstrated a 'fingerprint match' of T2-hyperintense regions with the intricate contour of infarcted regions by delayed-enhancement-MRI. Similarly, in patients there was a close correspondence between contours of T2-hyperintense and infarcted regions, and the transmural-extent of these regions were highly correlated (bright-blood-T2: r=0.82, p<0.0001; black-blood-T2: r=0.83, p<0.0001).
Conclusions: T2-weighted-MRI does not depict the area-at-risk. Accordingly, T2-weighted-MRI should not be used to measure myocardial salvage, either to inform patient management decisions or to evaluate novel therapies for acute MI.
- Received January 16, 2015.
- Revision received April 17, 2015.
- Accepted May 13, 2015.
Circulation Research is published on behalf of the American Heart Association, Inc., by Wolters Kluwer. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial-NoDervis License (http://creativecommons.org/licenses/by-nc-nd/3.0/), which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited, the use is noncommercial, and no modifications or adaptations are made.