Myocardium at Risk in ST-Segment Elevation Myocardial Infarction : Comparison of T2-Weighted Edema Imaging With the MR-Assessed Endocardial Surface Area and Validation Against Angiographic Scoring

ObjectivesThe objective of this study was to assess the area at risk (AAR) in ST-segment elevation myocardial infarction with 2 different cardiac magnetic resonance (CMR) imaging methods and to compare them with the validated angiographic Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease Score (APPROACH-score) in a large consecutive patient cohort.BackgroundEdema imaging with T2-weighted CMR and the endocardial surface area (ESA) assessed by late gadolinium enhancement have been introduced as relatively new methods for AAR assessment in ST-segment elevation myocardial infarction. However, data on the utility and validation of these techniques are limited.MethodsA total of 197 patients undergoing primary percutaneous coronary intervention in acute ST-segment elevation myocardial infarction were included. AAR (assessed with T2-weighted edema imaging and the ESA method), infarct size, and myocardial salvage (AAR minus infarct size) were determined by CMR 2 to 4 days after primary angioplasty. Angiographic AAR scoring was performed by use of the APPROACH-score. All measurements were done offline by blinded observers.ResultsThe AAR assessed by T2-weighted imaging showed good correlation with the angiographic AAR (r = 0.87; p < 0.001), whereas the ESA showed only a moderate correlation either to T2-weighted imaging (r = 0.56; p < 0.001) or the APPROACH-score (r = 0.44; p < 0.001). Mean AAR by ESA (20.0 ± 11.7% of left ventricular mass) was significantly (p < 0.001) smaller than the AAR assessed by T2-weighted imaging (35.6 ± 10.9% of left ventricular mass) or the APPROACH-score (27.9 ± 10.5% of left ventricular mass) and showed a significant negative dependence on myocardial salvage index. In contrast, no dependence of T2-weighted edema imaging or the APPROACH-score on myocardial salvage index was seen.ConclusionsThe AAR can be reliably assessed by T2-weighted CMR, whereas assessment of the AAR by ESA seems to be dependent on the degree of myocardial salvage, thereby underestimating the AAR in patients with high myocardial salvage such as aborted infarction. Thus, assessment of the AAR with the ESA method cannot be recommended. (Myocardial Salvage and Contrast Dye Induced Nephropathy Reduction by N-Acetylcystein [LIPSIA-N-ACC]; NCT00463749)