OXYGENATION IN THE RABBIT MYOCARDIUM - ASSESSMENT WITH SUSCEPTIBILITY-DEPENDENT MR-IMAGING

PURPOSE: To determine the feasibility of using hemoglobin (Kb) desaturation as an indicator of myocardial oxygenation. MATERIALS AND METHODS: High resolution gradient-echo nuclear magnetic resonance (MR) images of isolated, blood-perfused rabbit hearts were obtained at various blood oxygenation levels. The hearts were perfused at 37 degrees C with a Langendorff apparatus modified for nuclear MR imaging. The perfusate contained bovine red blood cells in a cardioplegic solution that eliminated motion artifacts and minimized arteriovenous oxygenation differences. Hb saturation was varied (7%-100%) randomly. Perfusion pressure was continuously monitored, and blood samples were obtained. RESULTS: There was a substantial correlation between image signal intensity in the myocardium and Hb saturation in the blood, believed to be due to susceptibility effects of the paramagnetic species deoxyhemoglobin. CONCLUSION: Direct and noninvasive determination of regional Kb saturation with susceptibility-dependent MR imaging may provide information regarding regional myocardial O-2 content.