Severity of blood flow reduction associated with detectable T2 enhancement in the area at risk of a reperfused canine model of acute myocardial infarction

Abstract

Background T2-weighted enhancement depicts the myocardial area at risk (AAR) associated with coronary occlusion. However, the severity of blood flow abnormality required to cause a detectable elevation in myocardial T2 is unknown. The aim of this study was to use microspheres to determine the severity of reduction in myocardial blood flow that results in visually detectable T2 weighted enhancement. Methods Surface coil intensity corrected T2 prepared SSFP at 1.5T was performed after 2 hours of coronary occlusion followed by 4 hours of reperfusion in a canine model. Myocardial blood flow during ischemia was determined by administering microspheres. A mid-ventricular short axis slice of the heart was divided into 16 transmural sectors for microsphere analysis. MR images were matched to the pathological slices at the sector level using papillary muscles and RV insertion as landmarks. ROIs delineated T2-enhanced and remote regions of the MR images and measurements were compared with microsphere blood flows. Results were reported as median (interquartile range [IQ]) and compared using the signed Wilcoxon rank test. Each T2-prepared sector was classified as bright (AAR) or normal (remote) by 2 independent readers and compared with absolute microsphere blood