Abstract 19267: Time Dependency of Edema-based Assessment of Area-At-Risk in Reperfused Acute Myocardial Infarction: A Serial Assement with Cardiac Magnetic Resonance Imaging
Introduction: Relative edema volume, computed from Cardiac MR images, has been used to define the Area-At-Risk in myocardial infarction and subsequently in the determination of salvagable myocardium in patients. Edema occurs following infarction, however, the length of time over which edema develops is unknown and its persistence has a variable resolution in the literature.
Hypothesis: Cardiac MR was used to investigate the hypothesis that edema volume increases over the course of several days in the acute post-infarct period.
Methods Lad: instrumented canines (n=6) underwent three hours of no-flow ischemia followed by reperfusion and were studied by MR [Siemens 1.5 T Espree] at five time points (before and during ischemia and then 2, 5 and 7 days post-reperfusion). A validated T2-imaging approach was used to generate T2 maps. Late-enhancement imaging was performed to confirm an LAD infarction. From the T2 maps, areas of T2 greater than 2SD from remote territories were measured, and were used along with imaging slice thickness to compute edema volume. Percent volume of edema was computed relative to total myocardial volume. Measurements were averaged across all animals for each time point.
Results: Percent volume of edema (Area-At-Risk) - Pre-ischemia: 0.8 ± 0.5%; Ischemia: 1.7 ± 1.4%; Day 2: 14.2 ± 5.1%; Day 5: 32.2 ± 6.5%; Day7: 22.0 ± 8.0%, p<0.01 by ANOVA. Results are reported as mean ± SEM. There was a continuous rise in relative edema volume post reperfusion through day 2 and peaking at day 5. Edema volume decreased slightly by day 7, although it was still significantly elevated from pre-ischemic levels.
Conclusion: This data indicates that the time following ischemia-reperfusion injury, for investigation of edema using MRI, is a critical variable in the determination of both Area-at-Risk and the salvagable myocardium.
- © 2010 by American Heart Association, Inc.