Abstract 17819: Implications of the Post-myocardial Infarction Bimodal Edematous Reaction for Quantifying Area at Risk, Infarct Size And Salvaged Myocardium by Cardiac Magnetic Resonance Imaging

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Background: Contrary to the accepted view, it has been recently demonstrated that myocardial edema after ischemia/reperfusion (I/R) follows a bimodal pattern during the first week. Purpose: To study the implications of the bimodal edema phenomenon on the cardiac magnetic resonance (CMR)-measured area at risk (AAR), infarct size and salvaged myocardium. Methods: Closed-chest 40min I/R was performed in 20 pigs. True anatomical AAR was assessed by arterial enhanced multidetector computed tomography (CT) performed during coronary occlusion. CMR with CINE, T2-weighted short-tau inversion recovery and late gadolinium-enhanced (LGE) sequences were performed at every follow-up (120 min, 24 hours, day 4 and day 7 after reperfusion) for the quantification of left ventricular mass, edema (CMR-AAR), and necrosis (infarct size). Salvaged myocardium was calculated by correcting infarct size for CMR-AAR extent. Results: A sharp increase in left ventricular mass due to huge swelling of the ischemic tissue was detected in early reperfusion (Figure 1A and 1E) leading to overestimation of CMR-AAR as compared to true AAR by CT at this time-point (Figure 1B and 1E). Due to reabsorption of initial edema and presence of significant hemorrhage, CMR-AAR was barely detectable at 24 hours while due to the progression of the deferred wave of edema, CMR-AAR accurately delineated true AAR at day 4 and day 7 (Figure 1B and 1E). A progressive decrease in infarct size was shown in LGE sequences (Figure 1C and 1E). As a consequence, salvaged myocardium dynamically varied within the first week after I/R (Figure 1D). Conclusions: The bimodal edematous reaction after I/R greatly impacts on the non-invasive quantification of CMR-AAR, infarct size and salvaged myocardium by CMR. The most appropriate day to perform CMR after reperfused infarction seems to be around day 7 coinciding with the peak of the deferred wave of edema.