Journal
CIRCULATION
Volume 105, Issue 2, Pages 224-229Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/hc0202.102016
Keywords
resonance imaging; contrast media; infarction; ischemia
Funding
- NHLBI NIH HHS [R29-HL53411, R01-HL63268] Funding Source: Medline
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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 50x100-mum 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.
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