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MR Imaging of Reperfused Myocardial Infarction: Comparison of Necrosis-Specific and Intravascular Contrast Agents in a Cat Model¹

¹ From the Departments of Radiology (S.S.L., H.W.G., S.B.P., J.B.S., T.H.L.) and Diagnostic Pathology (G.G.), Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, Korea; and Department of Radiology, Hanseo University, Seosan, Korea (C.H.L.). Received September 4, 2001; revision requested November 7; final revision received June 3, 2002; accepted July 16. Supported by a research grant (HMP-98-G-1-028) from the Korean Health and Welfare Ministry. Address correspondence to T.H.L. (e-mail: thlim@www.amc.seoul.kr).

View larger version (153K): [in a new window]   Figure 1a. MR images of the short axis of a cat heart at the midventricular level and the corresponding TTC-stained slice of reperfused myocardium. (a) Electrocardiographically-triggered turbo spin-echo T2-weighted MR image (1,400/82; echo train length, 33; matrix, 132 x 256; section thickness, 5 mm; no gap) shows the area of high signal intensity (arrows) in the territory of the LAD coronary artery. The mean size of the areas of abnormally high signal intensity on T2-weighted MR images was 45.3% of the left ventricular surface area. (b) Gadomer-17- and (c) bis-gadolinium mesoporphyrins-enhanced electrocardiographically-triggered turbo spin-echo T1-weighted MR images (700/25; matrix, 132 x 256; section thickness, 5 mm; no gap) also show increased signal intensity (arrows) in the territory of the LAD coronary artery. The mean sizes of the enhancing areas on Gadomer-17- and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images were 40.2% and 29.7% of the left ventricular surface area, respectively. In contrast to the transmural enhancement pattern seen on the Gadomer-17-enhanced T1-weighted MR image in b, the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c clearly depicts subendocardial infarction. (d) Macroscopic photograph of a TTC-stained myocardial specimen obtained at the same level as the MR images. The area of infarction corresponds to the nonstained area (*) seen in the territory of the LAD coronary artery. The mean size of infarcted myocardium at TTC staining was 28.5% of the left ventricular surface area. In this case, myocardial infarction was overestimated on the T2-weighted MR image in a and on the Gadomer-17-enhanced T1-weighted MR image in b by 16.8% and 11.7%, respectively. In contrast, the size of the enhancing area on the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c is nearly identical to the size of myocardial infarction at TTC staining in d.

View larger version (147K): [in a new window]   Figure 1b. MR images of the short axis of a cat heart at the midventricular level and the corresponding TTC-stained slice of reperfused myocardium. (a) Electrocardiographically-triggered turbo spin-echo T2-weighted MR image (1,400/82; echo train length, 33; matrix, 132 x 256; section thickness, 5 mm; no gap) shows the area of high signal intensity (arrows) in the territory of the LAD coronary artery. The mean size of the areas of abnormally high signal intensity on T2-weighted MR images was 45.3% of the left ventricular surface area. (b) Gadomer-17- and (c) bis-gadolinium mesoporphyrins-enhanced electrocardiographically-triggered turbo spin-echo T1-weighted MR images (700/25; matrix, 132 x 256; section thickness, 5 mm; no gap) also show increased signal intensity (arrows) in the territory of the LAD coronary artery. The mean sizes of the enhancing areas on Gadomer-17- and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images were 40.2% and 29.7% of the left ventricular surface area, respectively. In contrast to the transmural enhancement pattern seen on the Gadomer-17-enhanced T1-weighted MR image in b, the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c clearly depicts subendocardial infarction. (d) Macroscopic photograph of a TTC-stained myocardial specimen obtained at the same level as the MR images. The area of infarction corresponds to the nonstained area (*) seen in the territory of the LAD coronary artery. The mean size of infarcted myocardium at TTC staining was 28.5% of the left ventricular surface area. In this case, myocardial infarction was overestimated on the T2-weighted MR image in a and on the Gadomer-17-enhanced T1-weighted MR image in b by 16.8% and 11.7%, respectively. In contrast, the size of the enhancing area on the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c is nearly identical to the size of myocardial infarction at TTC staining in d.

View larger version (118K): [in a new window]   Figure 1c. MR images of the short axis of a cat heart at the midventricular level and the corresponding TTC-stained slice of reperfused myocardium. (a) Electrocardiographically-triggered turbo spin-echo T2-weighted MR image (1,400/82; echo train length, 33; matrix, 132 x 256; section thickness, 5 mm; no gap) shows the area of high signal intensity (arrows) in the territory of the LAD coronary artery. The mean size of the areas of abnormally high signal intensity on T2-weighted MR images was 45.3% of the left ventricular surface area. (b) Gadomer-17- and (c) bis-gadolinium mesoporphyrins-enhanced electrocardiographically-triggered turbo spin-echo T1-weighted MR images (700/25; matrix, 132 x 256; section thickness, 5 mm; no gap) also show increased signal intensity (arrows) in the territory of the LAD coronary artery. The mean sizes of the enhancing areas on Gadomer-17- and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images were 40.2% and 29.7% of the left ventricular surface area, respectively. In contrast to the transmural enhancement pattern seen on the Gadomer-17-enhanced T1-weighted MR image in b, the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c clearly depicts subendocardial infarction. (d) Macroscopic photograph of a TTC-stained myocardial specimen obtained at the same level as the MR images. The area of infarction corresponds to the nonstained area (*) seen in the territory of the LAD coronary artery. The mean size of infarcted myocardium at TTC staining was 28.5% of the left ventricular surface area. In this case, myocardial infarction was overestimated on the T2-weighted MR image in a and on the Gadomer-17-enhanced T1-weighted MR image in b by 16.8% and 11.7%, respectively. In contrast, the size of the enhancing area on the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c is nearly identical to the size of myocardial infarction at TTC staining in d.

View larger version (197K): [in a new window]   Figure 1d. MR images of the short axis of a cat heart at the midventricular level and the corresponding TTC-stained slice of reperfused myocardium. (a) Electrocardiographically-triggered turbo spin-echo T2-weighted MR image (1,400/82; echo train length, 33; matrix, 132 x 256; section thickness, 5 mm; no gap) shows the area of high signal intensity (arrows) in the territory of the LAD coronary artery. The mean size of the areas of abnormally high signal intensity on T2-weighted MR images was 45.3% of the left ventricular surface area. (b) Gadomer-17- and (c) bis-gadolinium mesoporphyrins-enhanced electrocardiographically-triggered turbo spin-echo T1-weighted MR images (700/25; matrix, 132 x 256; section thickness, 5 mm; no gap) also show increased signal intensity (arrows) in the territory of the LAD coronary artery. The mean sizes of the enhancing areas on Gadomer-17- and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images were 40.2% and 29.7% of the left ventricular surface area, respectively. In contrast to the transmural enhancement pattern seen on the Gadomer-17-enhanced T1-weighted MR image in b, the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c clearly depicts subendocardial infarction. (d) Macroscopic photograph of a TTC-stained myocardial specimen obtained at the same level as the MR images. The area of infarction corresponds to the nonstained area (*) seen in the territory of the LAD coronary artery. The mean size of infarcted myocardium at TTC staining was 28.5% of the left ventricular surface area. In this case, myocardial infarction was overestimated on the T2-weighted MR image in a and on the Gadomer-17-enhanced T1-weighted MR image in b by 16.8% and 11.7%, respectively. In contrast, the size of the enhancing area on the bis-gadolinium mesoporphyrins-enhanced T1-weighted MR image in c is nearly identical to the size of myocardial infarction at TTC staining in d.

View larger version (27K): [in a new window]   Figure 2a. Bland-Altman plots display average of surface area of infarcted myocardium at TTC staining and area of abnormally high signal intensity on MR images (x axes) versus the difference between them (y axes). The limits of agreement were (a) 18.1% ± 7.6 for nonenhanced T2-weighted MR imaging and TTC staining, (b) 12.0 ± 6.9 for Gadomer-17-enhanced MR imaging and TTC staining, and (c) 1.5% ± 5.1 for bis-gadolinium mesoporphyrins-enhanced MR imaging and TTC staining. The difference in the infarction size depicted at bis-gadolinium mesoporphyrins-enhanced MR imaging and that depicted at TTC staining showed close agreement, and Bland-Altman analysis disclosed no significant degree of systematic measurement bias.

View larger version (28K): [in a new window]   Figure 2b. Bland-Altman plots display average of surface area of infarcted myocardium at TTC staining and area of abnormally high signal intensity on MR images (x axes) versus the difference between them (y axes). The limits of agreement were (a) 18.1% ± 7.6 for nonenhanced T2-weighted MR imaging and TTC staining, (b) 12.0 ± 6.9 for Gadomer-17-enhanced MR imaging and TTC staining, and (c) 1.5% ± 5.1 for bis-gadolinium mesoporphyrins-enhanced MR imaging and TTC staining. The difference in the infarction size depicted at bis-gadolinium mesoporphyrins-enhanced MR imaging and that depicted at TTC staining showed close agreement, and Bland-Altman analysis disclosed no significant degree of systematic measurement bias.

View larger version (31K): [in a new window]   Figure 2c. Bland-Altman plots display average of surface area of infarcted myocardium at TTC staining and area of abnormally high signal intensity on MR images (x axes) versus the difference between them (y axes). The limits of agreement were (a) 18.1% ± 7.6 for nonenhanced T2-weighted MR imaging and TTC staining, (b) 12.0 ± 6.9 for Gadomer-17-enhanced MR imaging and TTC staining, and (c) 1.5% ± 5.1 for bis-gadolinium mesoporphyrins-enhanced MR imaging and TTC staining. The difference in the infarction size depicted at bis-gadolinium mesoporphyrins-enhanced MR imaging and that depicted at TTC staining showed close agreement, and Bland-Altman analysis disclosed no significant degree of systematic measurement bias.

View larger version (27K): [in a new window]   Figure 3. Line graph depicts the time course of signal intensity enhancement after administration of 0.05 mmol/kg Gadomer-17. Signal intensity of the enhancing area increased rapidly from the time immediately following contrast material injection to 40 minutes after. Maximum enhancement was detected from 10-40 minutes after contrast material administration (mean enhancement, 167% ± 14.8 of normal myocardium). After reaching maximum enhancement, the signal intensity of the area decreased gradually and returned to the precontrast state 5 hours after contrast material injection.

View larger version (23K): [in a new window]   Figure 4. Bar graph illustrates the measured sizes of the high-signal-intensity areas on T2-weighted MR images (T2), the enhancing areas on Gadomer-17-enhanced T1-weighted MR images, the enhancing areas on bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images (Gadophrin-2), and the areas of infarction seen at TTC staining. The high-signal-intensity areas on T2-weighted MR images were larger than the enhancing areas on Gadomer-17-enhanced T1-weighted MR images and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images. The enhancing areas seen on Gadomer-17-enhanced T1-weighted MR images were larger than the enhancing areas seen on bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images and the areas of myocardial infarction seen at TTC staining.

View larger version (162K): [in a new window]   Figure 5a. Photomicrographs show the ultrastructural features of cat myocardium after 90 minutes of ischemia followed by 90 minutes of reperfusion. (a) Ultrastructures of the infarct center. The mitochondria are swollen and contain electron-opaque, granular dense bodies (black arrows). Contraction bands (white arrows) are present. (TTC stain; original magnification, x4,000.) (b) Ultrastructures of periinfarct zone 1 (2 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrowheads). These findings are consistent with ultrastructural findings of reversibly damaged myocardium. However, some areas show swollen mitochondria and contraction bands (arrows), which represent ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (c) Ultrastructures of periinfarct zone 2 (4 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrows). Although the sarcoplasmic space has increased, the plasmalemma (arrowheads) of the sarcolemma is intact. These findings are consistent with the ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (d) Ultrastructures of periinfarct zone 3 (6 mm lateral from the margin of the infarct area). Myocardial cells are surrounded by an intact sarcolemma (arrowheads). Mitochondria (*) are abundant and I bands (arrows) appear normal. These findings are consistent with the ultrastructural changes of normal myocardium. (TTC stain; original magnification, x4,000.)

View larger version (147K): [in a new window]   Figure 5b. Photomicrographs show the ultrastructural features of cat myocardium after 90 minutes of ischemia followed by 90 minutes of reperfusion. (a) Ultrastructures of the infarct center. The mitochondria are swollen and contain electron-opaque, granular dense bodies (black arrows). Contraction bands (white arrows) are present. (TTC stain; original magnification, x4,000.) (b) Ultrastructures of periinfarct zone 1 (2 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrowheads). These findings are consistent with ultrastructural findings of reversibly damaged myocardium. However, some areas show swollen mitochondria and contraction bands (arrows), which represent ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (c) Ultrastructures of periinfarct zone 2 (4 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrows). Although the sarcoplasmic space has increased, the plasmalemma (arrowheads) of the sarcolemma is intact. These findings are consistent with the ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (d) Ultrastructures of periinfarct zone 3 (6 mm lateral from the margin of the infarct area). Myocardial cells are surrounded by an intact sarcolemma (arrowheads). Mitochondria (*) are abundant and I bands (arrows) appear normal. These findings are consistent with the ultrastructural changes of normal myocardium. (TTC stain; original magnification, x4,000.)

View larger version (167K): [in a new window]   Figure 5c. Photomicrographs show the ultrastructural features of cat myocardium after 90 minutes of ischemia followed by 90 minutes of reperfusion. (a) Ultrastructures of the infarct center. The mitochondria are swollen and contain electron-opaque, granular dense bodies (black arrows). Contraction bands (white arrows) are present. (TTC stain; original magnification, x4,000.) (b) Ultrastructures of periinfarct zone 1 (2 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrowheads). These findings are consistent with ultrastructural findings of reversibly damaged myocardium. However, some areas show swollen mitochondria and contraction bands (arrows), which represent ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (c) Ultrastructures of periinfarct zone 2 (4 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrows). Although the sarcoplasmic space has increased, the plasmalemma (arrowheads) of the sarcolemma is intact. These findings are consistent with the ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (d) Ultrastructures of periinfarct zone 3 (6 mm lateral from the margin of the infarct area). Myocardial cells are surrounded by an intact sarcolemma (arrowheads). Mitochondria (*) are abundant and I bands (arrows) appear normal. These findings are consistent with the ultrastructural changes of normal myocardium. (TTC stain; original magnification, x4,000.)

View larger version (158K): [in a new window]   Figure 5d. Photomicrographs show the ultrastructural features of cat myocardium after 90 minutes of ischemia followed by 90 minutes of reperfusion. (a) Ultrastructures of the infarct center. The mitochondria are swollen and contain electron-opaque, granular dense bodies (black arrows). Contraction bands (white arrows) are present. (TTC stain; original magnification, x4,000.) (b) Ultrastructures of periinfarct zone 1 (2 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrowheads). These findings are consistent with ultrastructural findings of reversibly damaged myocardium. However, some areas show swollen mitochondria and contraction bands (arrows), which represent ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (c) Ultrastructures of periinfarct zone 2 (4 mm lateral from the margin of the infarct area) show interfibrous edema and prominent I bands (arrows). Although the sarcoplasmic space has increased, the plasmalemma (arrowheads) of the sarcolemma is intact. These findings are consistent with the ultrastructural changes of irreversibly damaged myocardium. (TTC stain; original magnification, x4,000.) (d) Ultrastructures of periinfarct zone 3 (6 mm lateral from the margin of the infarct area). Myocardial cells are surrounded by an intact sarcolemma (arrowheads). Mitochondria (*) are abundant and I bands (arrows) appear normal. These findings are consistent with the ultrastructural changes of normal myocardium. (TTC stain; original magnification, x4,000.)