In vivo magnetic resonance imaging of experimental thrombosis in a rabbit model

The process of atherosclerotic plaque disruption has been difficult to moni tor because of the lack of an animal model and the limited ability to direc tly visualize the plaque and overlying thrombus in vivo. Our aim was to val idate in vivo magnetic resonance imaging (MRI) of the thrombus formation af ter pharmacological triggering of plaque disruption in the modified Constan tinides animal model of plaque disruption. Atherosclerosis was induced in 9 New Zealand White male rabbits (3 kg) with aortic balloon endothelial inju ry followed by a high cholesterol (1%) diet for 8 weeks. After baseline (pr etrigger) MRI, the rabbits underwent pharmacological triggering with Russel l's viper venom and histamine, followed by another MRI 48 hours later. Cont iguous cross-sectional T2-weighted fast spin echo images of the abdominal a orta were compared by histopathology. In all animals, aortic wall thickenin g was present on the pretrigger MRI. On MRIs performed 48 hours after trigg ering, a histologically confirmed intraluminal thrombus was visualized in 6 (67%) of the 9 animals. MRI data correlated with the histopathology regard ing aortic wall thickness (R=0.77, P<0.0005), thrombus size (R=0.82, P<0.00 01), thrombus length (R=0.86, P<0.005), and anatomic location (R=0.98, P<0. 0001). In vivo, MRI reliably determines the presence, location, and size. o f the thrombus in this animal model of atherosclerosis and plaque disruptio n. The combination of in vivo MRI and the modified Constantinides animal mo del could be an important research tool for our understanding of the pathog enesis of acute coronary syndromes.