SG Worthley*, G Helft, AG Zaman, V Fuster, ZA Fayad, JT Fallon, JJ Badimon,

Cardiovascular Centre, Monash Medical Centre, Clayton, VIC, 3168, and the Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY, 10029-6574.

Atherosclerotic plaque composition is central in the pathogenesis of acute coronary syndromes. Thus, there is a need for accurate imaging and characterization of atherosclerotic lesions. We describe the results of ex vivo and in vivo atherosclerotic plaque imaging in porcine models of coronary and aortic atherosclerosis.

Complex coronary and aortic atherosclerotic lesions were induced by a combination of cholesterol feeding and balloon injury in Yucatan micro-swine (n=4). Ex vivo MR imaging was performed on the excised aortas and coronary arteries (left in situ on the heart). T1W, T2W and PDW images were obtained. MR imaging accurately identified the plaque components (including calcified, lipid rich, hematoma/thrombus and fibrous components) as compared with histopathology. Mean wall thickness for the coronary arteries (r=0.94, slope=0.81) and aortas (r=0.94, slope=0.81) was accurately determined by ex vivo MR imaging (p<0.0001).

In vivo MR imaging of coronary artery lesions was performed using a double inversion recovery fast spin echo sequence using short (< 25 seconds) breath-holds and cardiac gating in a Yorkshire albino swine (n=6) balloon angioplasty model. High resolution PDW and T2W images with an in-plane resolution of 390-470 microns were obtained. An excellent correlation (p<0.001) between matched in vivo images and histopathology sections (n=43) was observed for mean wall thickness. Intralesion thrombus/hematoma was readily identified from the fibrocellular components with MRI.(sensitivity 82%; 9 of 11: specificity 84%; 27 of 32.

Noninvasive characterization of coronary artery lesions with MR may allow the detection of vulnerable atherosclerotic lesions in humans.

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