Author + information
- Matthias G. Friedrich, MD⁎ ( )()
- ↵⁎Montreal Heart Institute, Cardiology, 5000 Rue Belanger, Montreal, QC H1T 1C8, Canada
We thank Dr. Mewton and colleagues for their interest in our paper (1) and applaud them for raising an important point concerning the validity of current T2-weighted CMR imaging to visualize the area at risk in reperfused myocardial infarction (MI).
While technical issues with CMR imaging will be resolved by improved T2-weighted imaging protocols or novel T2 mapping techniques, the relationship of myocardial edema to the underlying pathophysiology deserves attention.
Recent animal data have confirmed an excellent agreement of findings in T2-weighted images with pathology in early reperfused MI (2). The amount of peri-infarct edema in clinical studies, however, varies significantly (3) and thus needs to be further studied. Specifically, there is a lack of validation data on the impact of potential confounders related to reperfusion. It is very likely that reperfusion injury with associated peri-infarct inflammation and microvascular dysfunction will modify the extent of myocardial edema. A recent study by Mewton et al. (4) indicates that reperfusion after a 40-min period of coronary occlusion may increase the extent of edema and thus apparent “myocardial salvage” within the first 90 min. Regarding late reperfusion, previous clinical studies showing edema adjacent to the necrotic zone in late reperfused myocardial infarction (3), which is unlikely to be related to actual salvage but more likely reflects an inflammatory response of adjacent tissue, is possibly related to reperfusion injury. Moreover, in several studies, the area at risk was consistently larger in the group with more severe injury as indicated by myocardial hemorrhage (5).
Because the histologic assessment of myocardial edema is challenging and virtually impossible in clinical models, experimental and clinical research will have to use CMR and careful study designs to scrutinize the impact of reperfusion and other, less important potential confounders on the extent of myocardial edema.
Despite these knowledge gaps, there is solid evidence that T2-weighted imaging is closely correlated with the area at risk in reperfused MI and, in combination with late Gd enhancement imaging, allows for the assessment of myocardial salvage. Before having a more clear understanding of confounders, it may be too early to claim a precision in the <10% range. Clearly, further studies are required to understand the impact of potential clinical confounders, yet there is little doubt that the available techniques provide unique invaluable in vivo data on myocardial injury in patients with reperfused MI.
- American College of Cardiology Foundation
- Friedrich M.G.,
- Kim H.W.,
- Kim R.J.
- Friedrich M.G.,
- Abdel-Aty H.,
- Taylor A.,
- Schulz-Menger J.,
- Messroghli D.,
- Dietz R.
- Mather A.N.,
- Fairbairn T.A.,
- Ball S.G.,
- Greenwood J.P.,
- Plein S.