Abstract 3013: Myocardium at Risk of Infarction during Acute Ischemia is Accurately Measured after Revascularization by MRI in Humans

Abstract

PURPOSE: The size of an infarct caused by coronary occlusion mainly depends on the duration of ischemia and the size of the ischemic myocardium, called myocardium at risk (MaR). T2-STIR imaging (visualizing oedema) has been shown to depict MaR in dogs. However, this has not been validated in humans. Therefore the purpose of this study was to validate the measurement of MaR by MRI against SPECT. METHODS: 7 patients (69±8 years, all male) with ST-elevation infarction treated by PCI were included. Technetium-labelled tetrofosmin was injected during ongoing ischemia before opening of the occluded vessel. SPECT was performed after concluded PCI and cardiac MRI after 3±3 days. MaR was measured as absent perfusion on SPECT and oedema on MRI, and expressed in percent of the left ventricular myocardium. The observer of the MRI data was blinded to the SPECT results. The localisation of transmural ischemia by the two methods was compared by visual assessment. RESULTS: The difference between SPECT and MRI for measurement of MaR was 0±9 % (mean±SD). The localization of transmural ischemia agreed between the two methods (Fig. 1 ) and expressed on vessel basis, MRI and SPECT showed 100 % concordant results. CONCLUSIONS: This study has showed for the first time in humans that T2-STIR accurately can determine myocardium at risk. This can be used in clinical research when studying new therapies for reducing infarct size. Fig 1 : Short axis slices of left ventricle showing inferior defect on SPECT (arrows, left panel) corresponding to the oedema signal on T2-STIR MRI (arrows, middle panel). For comparison, delayed enhancement in right panel shows subendocardial infarction (arrows).