Changes in first-pass interstitial kinetics of DTPA in myocardium submitted to low-flow ischemia.

Objectives: This study aimed to determine the changes during ischemia in the myocardial first-pass kinetics of DTPA, an extracellular tracer that is currently used for assessing myocardial perfusion with magnetic resonance imaging (Magnevist).

Materials And Methods: Using an indicator-dilution technique, first-pass kinetics of DTPA were compared between normoxia (n=11) and low-flow ischemia (n=11) in isolated rabbit hearts perfused with red blood cell-enhanced perfusate.

Results: There was no difference between ischemia and normoxia in the interstitial extraction and clearance rates of DTPA.

Low-flow ischaemia has no deleterious effect on the steady-state kinetics of 201Tl and 99mTc sestamibi within myocardial tissue.

Objectives: This study aimed to specifically analyse the impact of low-flow ischaemia on the ability of myocytes to trap and accumulate Tl and sestamibi (MIBI) within myocardial tissue.

Methods: In order to reach steady-state conditions for the interstitial/cellular concentration ratios (Ci/Cc) of the tracers and thereby simulate the conditions of cell cultures studies, Tl and MIBI were injected continuously during an 80 min period within the coronary circulation of isolated hearts submitted to normoxia (n=7) or low-flow ischaemia (n=7; >50% reduction in coronary flow). Ci was determined by using interstitial microdialysis and Cc was determined from Ci and myocardial retention values of the tracers.

(201)Tl and (99m)Tc-MIBI retention in an isolated heart model of low-flow ischemia and stunning: evidence of negligible impact of myocyte metabolism on tracer kinetics.

Unlabelled: It is not known whether cellular metabolic disorders play a role in the decreased tracer uptake that is documented by conventional SPECT during low-flow ischemia or stunning. This study sought to determine the impact of low-flow ischemia and stunning on the kinetics of (201)Tl and MIBI across the plasma membrane of myocytes.

Methods: The global myocardial retention (Rf) of (201)Tl and MIBI was determined in isolated working hearts from rabbits, perfused with red blood cell-enhanced solution.

201Tl SPECT abnormalities, documented at rest in dilated cardiomyopathy, are related to a lower than normal myocardial thickness but not to an excess in myocardial wall stress.

Unlabelled: This study was aimed at determining whether the (201)Tl SPECT abnormalities documented in patients with dilated cardiomyopathy are related to a local excess in wall stress, which might act against the diastolic perfusion of myocardium.

Methods: We included 6 healthy volunteers and 7 patients with idiopathic dilated cardiomyopathy who underwent (201)Tl SPECT at rest. On a 13-segment division of the left ventricle, indices of wall stress and tension were calculated at end-diastole by applying Laplace's law, with thickness and curvature radii being determined for each segment on 2 orthogonal MRI slices.