3-DIMENSIONAL P-31 MAGNETIC-RESONANCE SPECTROSCOPIC IMAGING OF REGIONAL HIGH-ENERGY PHOSPHATE-METABOLISM IN INJURED RAT-HEART

The purpose of this study was to measure the spatially varying P-31 MR signals in global and regional ischemic injury in the isolated, perfu sed rat heart. Chronic myocardial infarcts were induced by occluding t he left anterior descending coronary artery eight weeks before the MR examination. The effects of acute global low-flow ischemia were observ ed by reducing the perfusate flow. Chemical shift imaging (CSI) with t hree spatial dimensions was used to obtain P-31 spectra in 54-mu l vox els. Multislice H-1 imaging with magnetization transfer contrast enhan cement provided anatomical information. In normal hearts (n = 8), a ho mogeneous distribution of high-energy phosphate metabolites (HEP) was found. In chronic myocardial infarction (n = 6), scar tissue contained negligible amounts of HEP, but their distribution in residual myocard ium was uniform. The size of the infarcted area could be measured from the metabolic images; the correlation of infarct sizes determined by histology and P-31 MR CSI was excellent (P < 0.006). In global low-flo w ischemia (n = 8), changes of HEP showed substantial regional heterog eneity. Three-dimensional P-31 MR CSI should yield new insights into t he regionally distinct metabolic consequences of various forms of myoc ardial injury.