Imaging of atherosclerosis in WHHL rabbits using high-resolution ultrasound.

Watanabe heritable hyperlipidemic (WHHL) rabbits provide an animal model of hypercholesterolemia and atherosclerotic progression. However, a large individual variation in plaque progression rate calls for serial investigations, as do treatment studies. In contrast to histopathology, transthoracic ultrasound imaging of the aortic arch is a noninvasive technique suitable for repeated investigations. We studied 34 WHHL rabbits by both techniques. Ultrasound correctly interpreted plaque morphology compared with histopathology of the same spot (location verified by needle puncture). Intima media thickness (IMT) measured by the two methods agreed well. Ultrasonic values were similar to the histopathologic average circumferential values when these were corrected for postmortem shrinkage. Finally, the transthoracic ultrasound technique demonstrated a significant increase in IMT over a 15-week period (p = 0.0002). We conclude that transthoracic ultrasound of aortic arch IMT in WHHL rabbits is a reliable and feasible technique for studies of plaque progression and the evaluation of interventions.