NONINVASIVE
IN VIVO MRI DOCUMENTS ARTERIAL
REMODELING IN A NOVEL WHHL RABBIT MODEL. SG Worthley*, AG Zaman, G Helft, 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. Noninvasive MRI has the
potential for serial monitoring of atherosclerosis progression. The WHHL rabbit
is biologically preferable to cholesterol fed rabbit models of atherosclerosis
as it more closely approximates humans. We studied an abdominal aortic balloon
injury in the WHHL rabbit and undertook MRI before and 6 months post-injury. WHHL rabbits (age 3 months,
n=12), underwent MRI of the abdominal aorta in a clinical 1.5T system. Fast
spin echo sequences were obtained with in-plane resolution of 350m and slice thickness 3mm.
T2W (TR/TE 2300/60 msec) and PDW (TR/TE 2300/15) were acquired. Sequential MRI
studies were performed at baseline and 6 months later. After the baseline MRI
balloon denudation was performed. The MR images of the same aortic sections
(n=10 per rabbit) were compared at the two time points. A subgroup of rabbits
(n=3) were sacrificed for histopathological correlation with MRI at this 6
month time point. High quality MR images were
obtained. The mean vessel wall area for all MR images of aortic segments
significantly increased (p<0.0001 paired students t-test) from 3.61±0.68mm2 to 5.57±0.86mm2. Analysis of the
luminal area showed that despite the increase in atherosclerotic burden over
time, there was a slight but significant (p=0.006) increase in the mean lumen
area, from 4.36±1.46mm2 to 4.89±1.09mm2. A significant
(p<0.0001) outward remodeling was thus observed as evidenced by the large
increase in the outer vessel wall area from 7.96±1.79mm2 to 10.46±1.81mm2. In vivo MRI can serially and
noninvasively document changes in atherosclerotic burden and arterial
remodeling in this novel rabbit model.
