Abstract 16686: Early Gadolinium Enhancement Represents Area at Risk Not Infarct Size: Timing and Kinetics Are Critical in Interpreting MRI of Acute Myocardial Infarction
Background: Recent papers have raised questions about whether gadolinium over-estimates infarct size and have indicated that early gadolinium enhancement (EGE) corresponds to the area at risk (AAR) rather than infarct size.Objective: To determine kinetics, timing, and size of early gadolinium enhancement as related to measurements of area at risk and infarct size in patients with acute myocardial infarction (MI).
Methods: MRI was performed on 35 patients within 7 days of acute MI. T2-weighted images were acquired with bright blood methods to measure AAR. EGE images were acquired 1, 3, 5, and 7 minutes post-contrast with single-shot phase sensitive inversion recovery (PSIR). Late gadolinium enhanced (LGE) images were obtained 10-20 minutes post-contrast using segmented PSIR. EGE images were evaluated semi-quantitatively using a 2-SD threshold and with manual planimetry. LGE Infarct size was measured with the previously validated FACT algorithm. Microvascular obstruction was included in the hyperenhanced zone for EGE and LGE.
Results: Of the 35 patients (26 were male, age 61±12 years old), 14 had subendocardial MI and 21 had transmural MI. For subendocardial MI, the correlation between EGE and T2-weighted AAR was only fair at 1 minute post contrast (r=0.68), but improved to (r=0.86-0.88) from 3 minutes to 7 minutes post-contrast administration. However, there was significant intersubject variability with regard to the optimal timing for EGE as a measure of AAR. For subendocardial MI, the best agreement between EGE and T2 weighted AAR occurred at 3 minutes in 4 subjects, 5 minutes in 4 subjects, and 7 minutes in 5 subjects. For transmural MI (n=21), the best agreement occurred at 7 minutes post-contrast. The maximal area of hyperenhancement on EGE correlated most closely with T2 AAR for subendocardial MI (r=0.91) and was significantly larger than MI size on LGE images (p<0.001 for all MI and for subendocardial MI).
Conclusion: Myocardial gadolinium enhancement kinetics influence the size of the hyperenhanced zone such that early gadolinium enhancement between 3-7 minutes closely correlates with area at risk, and thus can over-estimate infarct size for non-transmural MI. Timing is critical when quantifying acute infarct size with gadolinium enhanced MRI.
- © 2011 by American Heart Association, Inc.