Implantation of Human-Sized Coronary Stents into Rat Abdominal Aorta Using a Trans-Femoral Access

This protocol uses an animal model to establish an accessible method for characterizing the effects of human coronary stents on vascular pathology. The main advantages of our model are that is minimally invasive, highly reproducible, and easily performed even by researchers with little operative experience. Demonstrating the the procedure will be Roberta Florescu, a physician from our laboratory.

Following this procedure, other clinical and pathology diagnostic tools can be used, such as optical coherence tomography or histological analysis. After confirming a lack of response to pedal reflex in an anesthetized adult rat, place the rat on a heating pad in the supine position with the right hind limb fully extended and in line with the spine, and fix the upper and lower limbs with medical tape. Apply ointment to the animal's eyes and shave the fur from the groin and lower abdomen.

Then sterilize the exposed skin with a povidone iodine solution. For implantation of the stent, make a 0.5 to one centimeter medial incision in the right groin to open the skin and underlying fascia, and bluntly dissect and probe the tissue until the pulsating left femoral artery is located. Using very fine forceps, gently remove the connective tissue surrounding the artery and carefully insert the top of the forceps under the vessel.

Thread pieces of 4-0 silk suture under the distal and proximal parts of the artery to form slings and clamp the ends of each of the two threads slings between the branches of a surgical clamp. Use the surgical clamps to control the artery and gently stretch and lift the artery to temporarily interrupt the blood flow. Using sharp micro-scissors, quickly perform in arteriotomy in the middle of the femoral artery and introduce a guide wire into the arteriotomy.

When the proximal thread sling is reached, move the surgical clamp to release the tension of the thread and advance the guide wire toward the abdominal aorta. Introduce a 2.25 by eight millimeter crimped and balloon-mounted coronary stent over the guide wire into the femoral artery. Advance the stent to the abdominal aorta until it is just above the aortic bifurcation, but below the renal arteries.

When the stent is in place, use an inflation syringe system to inflate the balloon catheter to its nominal pressure. After 15 seconds, deflate the balloon catheter and maintain negative pressure according to the manufacturer's recommendations for the stent in use. Next, slowly withdraw the deflated catheter while leaving the stent in place.

Just before removing the guide wire, use the surgical clamp to create tension on the threaded loop above the incision to interrupt the blood flow and remove the guide wire. Directly ligate the vessel proximally and tie the proximal and distal thread loops to ligate the femoral artery. Then confirm adequate hemostasis of the arteriotomy and use 6-O non-resorbable sutures to close the muscle overlying the artery and the skin incision.

In this representative analysis, human-sized coronary stents were successfully deployed with no sign of malapposition or vessel injury. Homozygous apolipoprotein E knockout rats developed markedly elevated neointimal hyperplasia and in-stent restenosis compared to wild type rats. Although the apolipoprotein E knockout background renders animals more susceptible to atherosclerosis, no antecedent atherosclerotic plaques were observed in these rats.

Selecting the proper stent size for each animal and using rats weighing over 500 grams for the human coronary stent implantation are critical to the success of the procedure.