Wolfgang G Rehwald1, David S. Fieno1, Enn-Ling Chen1, Raymond J. Kim1, Robert M. Judd1,2
1From the Northwestern University Medical School Feinberg Cardiovascular Research Institute (W.G.R., D.S.F., E.-L.C., R.J.K., R.M.J.), Departments of Medicine (R.J.K., R.M.J.) and Biomedical Engineering (W.G.R., D.S.F., R.M.J.), Chicago, Ill.
2LIPPINCOTT WILLIAMS & WILKINS
Tóm tắt
Background
—
Discrepant reports have been published recently regarding the relationship of contrast-enhanced magnetic resonance image intensities to reversible and irreversible ischemic injury. Unlike image intensities, contrast agent concentrations provide data independent of the MRI technique. We used electron probe x-ray microanalysis (EPXMA) to simultaneously examine concentrations of Gd, Na, P, S, Cl, K, and Ca over a range of myocardial injuries.
Methods and Results
—
Reversible and irreversible injury were studied in 38 rabbits divided into 4 groups defined by occlusion and reperfusion time, as well as time the animals were euthanized. Gd-DTPA was administered, and the hearts were excised and rapidly frozen, cryosectioned, freeze-dried, and examined by EPXMA in up to 3 regions: remote, infarcted, and at risk but not infarcted. Infarcted regions were defined by anti-myoglobin antibody or triphenyltetrazolium chloride staining. Regions at risk were defined by fluorescent microparticles administered during occlusion. Compared with remote regions, in acutely infarcted regions, Gd was increased (235±24%,
P
<0.005) in the same 50×100-μm areas in which Na was increased (154±5%,
P
<0.001) and K was decreased (52±8%,
P
<0.001). Similarly, in chronically infarcted regions, Gd was increased (472±78%,
P
<0.001) in areas in which Na was increased (332±28%,
P
<0.001) and K was decreased (47±5%,
P
<0.001). Also compared with remote regions, however, concentrations of Gd, Na, and K were not elevated after reperfusion in regions that were at risk but not infarcted (
P
=NS).
Conclusions—
Regional elevations in myocardial MRI contrast agent concentrations are exclusively associated with irreversible ischemic injury defined histologically and by regional electrolyte concentrations.
