Use of nuclear magnetic resonance imaging angiography to follow-up arterial remodeling in an animal model

Atherosclerosis imaging and heart failure

Coronary atherosclerosis is the most important primary etiologic factor predisposing to the development of heart failure. The mechanisms by which coronary atherosclerosis lead to heart failure likely involve the initial development of regional myocardial dysfunction, later progressing to global ventricular failure and symptomatic congestive disease. A variety of imaging strategies have been investigated for their value in identifying and characterizing markers of atherosclerosis in the effort to detect early cardiac disease. Non-invasive imaging techniques for assessing anatomic or functional manifestations of atherosclerosis include carotid ultrasonography, coronary computed tomography, cardiovascular magnetic resonance imaging, brachial artery reactivity testing, and the ankle-brachial index. Many of these imaging methods are shown to have accuracy, reliability, and the potential to add value to an office-based cardiovascular risk assessment. Further development of such imaging methods could facilitate early intervention in the development of myocardial dysfunction while enhancing our understanding of the natural course of atherosclerotic disease.

Mophometric study of the aortic arch and its major branches in rat fetuses on the 21st day of gestation

The anatomy and embryology of the aortic arch and its branching tributaries (brachiocephalic trunk, left common carotid artery and left subclavian artery) in man and animals are well substantiated. However, the anatomical variations and morphometry of the aortic arch and its branching tributaries in rat fetus at the 21st gestation day have not been studied. Pregnant rats were hysterectomized and the arterial systems of 114 fetuses were injected with a polymerisable resin through the umbilical artery. After maceration, the vascular casts were dissected out and prepared for observations under a scanning electron microscope (SEM). The resulting SEM pictures were studied with a picture analyser and different vessel parameters (diameters, lengths and angles) were measured. The success rate of the microvascular cast injection was 46.5%. Out of the 53 observed aortic arch casts, 98.1% showed the classical branching pattern and one (1.9%) had no brachiocephalic trunk. Morphological analysis showed many differences, which were not linked to the litter. The statistical processing of the measurements enabled us to determine that the aorta diameter after the branching of the left subclavian artery was the most replicable parameter. Moreover, the results revealed some strong correlations between different parameters. There are probably no discrete categories among the various observed parameters as diameters and angles. Some parameters show very little variability and can thus be used as reference points for further studies such as the comparison of a control population with a population treated with a relevant xenobiotic.

Repeated Three-Dimensional Magnetic Resonance Imaging of Atherosclerosis Development in Innominate Arteries of Low-Density Lipoprotein Receptor-Knockout Mice

Background— In vivo methods to evaluate the size and composition of atherosclerotic lesions in animal models of atherosclerosis would assist in the testing of antiatherosclerotic drugs. We have developed an MRI method of detecting atherosclerotic plaque in the major vessels at the base of the heart in low-density lipoprotein (LDL) receptor-knockout (LDLR −/− ) mice on a high-fat diet.

Methods and Results— Three-dimensional fast spin-echo magnetic resonance images were acquired at 7 T by use of cardiac and respiratory triggering, with ≈140-μm isotropic resolution, over 30 minutes. Comparison of normal and fat-suppressed images from female LDLR −/− mice 1 week before and 8 and 12 weeks after the transfer to a high-fat diet allowed visualization and quantification of plaque development in the innominate artery in vivo. Plaque mean cross-sectional area was significantly greater at week 12 in the LDLR −/− mice (0.14±0.086 mm 2 [mean±SD]) than in wild-type control mice on a normal diet (0.017±0.031 mm 2 , P <0.01). In the LDLR −/− mice, but not control mice, increase in plaque burden at week 12 relative to week 1 was also highly significant ( P =0.001). Lumen cross section was not significantly different between time points or groups. MRI and histological assessments of plaque size were closely correlated ( R =0.8). The lumen of proximal coronary arteries could also be visualized.

Conclusions— This is the first report of in vivo detection of aortic arch atherosclerosis in any animal model. The method could significantly assist rapid evaluation of experimental antiatherosclerotic therapies.