Tissue edema does not change gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced T1 relaxation times of viable myocardium

Purpose: To determine whether tissue edema changes gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)enhanced T-1 relaxation times of the viable myocardium. Materials and Methods: A total of 16 isolated pig hearts were divided into four groups (N = 4/group) and perfused in a Langendorff apparatus. Gd-DTPA was injected into the aortic perfusion line. Tissue edema was then induced by two hours of simultaneous arterial/venous perfusion (SAVP). Myocardial water content and T-1 relaxation times were monitored throughout SAVP. The volumes of the extracellular and intracellular compartments were assessed using P-31 MRS-detectable markers, phenylphosphonic acid (PPA) and dimethyl methylphosphonate (DMMP). Results: Tissue water content in both viable and infarcted myocardium increased significantly during two-hour SAVP. However, Gd-DTPA-enhanced T-1 relaxation times of the viable myocardium remained relatively unchanged. Infarcted myocardium, on the other hand, exhibited significant T-1 shortening during SAVP. Furthermore, SAVP resulted in significant expansions of both extracellular and intracellular compartments, but the ratio of the volumes of the two compartments remained relatively constant. Conclusion: Tissue edema in the viable myocardiurn does not increase the relative distribution volume of the contrast agent. As a result, edema does not change Gd-DTPA-enhanced T-1 relaxation times of the viable myocardium.