Na Chemical Shift Imaging of myocardial edema

Introduction – Distinction between viable and non-viable myocardium is essential for diagnosis and treatment of patients with coronary artery disease. Delayed contrast-enhanced (DCE) MRI has become the gold standard to determine the size of chronic infarcts. However, although T2-weigthed MRI shows great promise to delineate the area at risk after the event related to the formation of edema, the accuracy of DCE-MRI to determine the size of acute infarcts has been questioned because of that same edema. As an alternative approach we would like to propose Na Chemical Shift Imaging (CSI) with the aid of a shift reagent. In edematous, but viable tissue we expect the extracellular Na signal (Nae) to be increased but little change in the intracellular Na signal (Nai). In acute infarcts with cell membranes still intact, we expect Nai to be very high, whereas in chronic infarcts Nae should be very high and Nai should be absent. To further explore this methodology, we have created an isolated, perfused heart model of extracellular edema based on different perfusion pressures, which has been characterized using P MRS. Subsequently, we have characterized the formation of edema by both DCE H MRI and Na CSI.