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Determining Canine Myocardial Area at Risk with Manganese-enhanced MR Imaging¹

¹ From the Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, National Institutes of Health, U.S. Department of Health and Human Services, 10 Center Dr, MSC 1061, Bldg 10, Room B1D-416, Bethesda, MD 20892-1061 (A.N., A.H.A., L.Y.H., A.E.A.); and Mount Sinai School of Medicine, New York, NY (A.N.). Supported by the intramural program of the National Heart, Lung, and Blood Institute. A.N. supported by the Clinical Research Training Program, sponsored by Pfizer, at the National Institutes of Health. Received March 15, 2004; revision requested May 25; revision received November 1; accepted November 12. Address correspondence to A.E.A. (e-mail: araia{at}nih.gov).

PURPOSE: To test whether manganese-enhanced magnetic resonance (MR) imaging can safely depict the myocardial area at risk both during coronary artery occlusion and for at least 2 hours after reperfusion in dogs.

MATERIALS AND METHODS: All procedures were performed in accordance with the animal care and use committee of the National Institutes of Health. In eight dogs, the left anterior descending (LAD) coronary artery was occluded for 90 minutes, and 15 µmol of MnCl₂ per kilogram of body weight was intravenously infused for 12 minutes. Phase-sensitive inversion-recovery MR imaging of the LAD arterial territory was performed before occlusion, during MnCl₂ infusion, and for at least 2 hours after reperfusion. Hemodynamic responses were monitored continuously. Fluorescent microsphere enhancement was used as the reference standard for determining the area at risk ex vivo. Results are reported as percentages of left ventricular area. Correlation, Bland-Altman, and t test analyses were performed.

RESULTS: Significant differences in manganese-induced contrast enhancement of the area at risk, the normal myocardium, and the blood (P < .01) were measured during LAD artery occlusion and at least 2 hours after reperfusion. No significant changes in heart rate or blood pressure were detected during or after MnCl₂ infusion. Measurements of the area at risk obtained with manganese-enhanced MR imaging during LAD artery occlusion and 2 hours after reperfusion correlated well with the size of the at-risk area demarcated by the fluorescent microspheres (during occlusion: y = 0.81x, R = 0.90; during reperfusion: y = 0.83x, R = 0.89). Bland-Altman analysis revealed small systematic errors in measurements at both occlusion and reperfusion.

CONCLUSION: Manganese-enhanced MR imaging can depict the area at risk during LAD artery occlusion and at least 2 hours after reperfusion without hemodynamic compromise.

© RSNA, 2005