Abstract 16534: Contrast Enhanced CT and MRI Measures of Extracellular Volume Fraction Confirm Presence of Peri-Infarct Edema in Acute Myocardial Infarction
INTRODUCTION: The presence of peri-infarct edema as a marker of the area at risk has been controversial since some gadolinium-enhanced studies do not seem to show expected enhancement of edema. Myocardial extracellular volume fraction (ECV) imaging by magnetic resonance imaging (MR) is feasible but would benefit from validation of ECV measures by an independent method like computed tomography (CT).
HYPOTHESES: Since most clinically approved gadolinium-based (MR) and iodinated (CT) contrast agents distribute into the extracellular space, measurements of ECV by CT and MR should agree. If the area at risk is edematous as suggested by T2 weighted images, then the ECV by CT and MR should be elevated relative to remote myocardium.
METHODS: Dogs (n=10) underwent coronary occlusion (2h) and reperfusion (2h), followed by CT scanning (320 channels) and 1.5T MR imaging with T1 mapping. CT and MR imaging measures before and after contrast (iopamidol or gadolinium-DTPA, respectively) both in tissue and in blood, corrected for hematocrit, were used to generate ECV images. ECV was measured in remote, salvaged, and infarcted myocardium.
RESULTS: Myocardial ECV by CT and MR correlated over a wide range of values (R2=0.80, p<0.001, Figure) and the mean difference between MR and CT was small (3±9%). ECV of the salvaged area at risk by CT agreed well with MR (42±8% vs 43±4%, p=0.71) and both were higher than remote myocardium (CT 25±5%, MR 27±4% both p≤0.001 vs salvaged).
CONCLUSIONS: Myocardial ECV imaging by MR and CT showed a good agreement and both methods support the conclusion that the extracellular volume is increased in the salvaged peri-infarct zone around acute myocardial infarction.FIGURE: Quantitative CT ECV and MR ECV images of the same short-axis slice through an acute anterior myocardial infarction, in grey scale and the same images in color scale. Note the intermediately increased ECV around the bright infarction.
- © 2011 by American Heart Association, Inc.