LAUSR

Objective: Assessment of tissue salvage after myocardial infarction (MI) requires accurate quantification of the ischemic area at risk (AAR). Although the AAR is typically measured retrospectively within one week after reperfusion, dynamic changes in tissue composition may affect the precision of this approach. Given recent cardiac MRI data demonstrating a transient reduction in myocardial edema 24 hours after reperfused MI, we tested the hypothesis that this is an optimal timepoint for accurate retrospective AAR assessment. Methods: Swine (n=27) were subjected to a 1 hour LAD occlusion, during which the AAR was assessed by contrast enhanced CT-derived quantification of the myocardial perfusion defect. Phthalocyanine blue was administered at the end of occlusion (n=7) or during re-occlusion of the LAD 3 hours (n=5), 24 hours (n=5) or 7 days (n=10) after reperfusion for pathologic determination of the AAR. Serial echocardiography was performed in the 24 hour reperfusion group to assess end diastolic wall thickness (EDWT) as a surrogate index of post-MI edema. Results: When assessed before reperfusion, the AAR was similar by CT and postmortem pathology ( Table ). However, AAR measurements 3 hours, 24 hours, and 7 days after reperfusion overestimated CT AAR mass by 38±7 %, 31±10 %, and 37±5%, respectively. Echocardiography showed a marked increase in EDWT 1 and 3 hours after reperfusion, followed by a decrease at 24 hours that remained significantly higher than pre-ischemia values. Conclusion: Despite partial resolution of edema 24 hours after reperfusion, AAR measurement at this time does not provide an accurate assessment of the AAR obtained during the initial coronary occlusion.