Reliable animal models for giant aneurysms are rare. However, these models are extremely important for the development of new endovascular devices to treat these aneurysms safely. The advantages of this technique are true bifurcation design for giant aneurysms, minimal morbidity, and high aneurysm patency rates with high comparability to humans.
Giant aneurysms are challenging lesions to treat in humans. This protocol focuses on the creation of these aneurysms and offers the possibility for testing of new endovascular devices. Demonstrating the procedure will be Camillo Sherif.
He's the senior research leader of our study group and has extensive experience with rabbit aneurysm models. After anesthetizing the rabbit, intubate the animal using a tube having four millimeter diameter and 18 millimeter length. Monitor the depth of anesthesia with a toe pinch every 15 minutes and adjust if necessary.
Using clippers, shave the area from the angle of the jaw down to the animal's thorax and disinfect the shaved surgical area. For microsurgical creation of bifurcation aneurysms, incise the skin along the midline from the angle of the jaw down to the manubrium sterni of the animal using a scalpel. Perform blunt dissection in the subcutis.
Next, under a surgical microscope, dissect a two to three centimeters long branchless segment of the left external jugular vein. Dropwise, apply 4%propiverine repeatedly on the vessels to prevent vasospasm, and five milligrams per milliliter of neomycin sulfate for infection control. Perform proximal and distal ligation on the vein using 6-0 non-resorbable sutures.
Measure the vein length, harvest the vein segment, and place it in a heparinized saline solution. Prepare both common carotid arteries or CCAs by dissecting them from the carotid bifurcation to their origin. Watch carefully for the medial arterial branches which supply the laryngeal, tracheal, and neural structures.
Apply a temporal microsurgical clip at the distal end of the right CCA. Using polyfilament 6-0 non-resorbable sutures, ligate the right CCA proximally directly above the brachiocephalic trunk and cut it. With the help of anatomic microforceps and microscissors, remove the adventitia at the anastomosis site of both vessels.
Then clip the anastomosis site of the left CCA distally and proximally. Make an arteriotomy at the left CCA according to the size of the planned anastomosis with the right CCA and the venous pouch. Determine the length of the arteriotomy by the diameter of the contralateral carotid artery which is about two millimeters and the planned aneurysm neck size.
The size should be between 3 and 15 millimeters considering the possible aneurysm and neck sizes of this model. Clean the aneurysm site with five milliliters of heparinized saline. Use four to five non-resorbable 10-0 monofilament sutures to suture the posterior circumference of the right CCA stump with the previously described arteriotomy of the left CCA.
Cut the stump of the right CCA longitudinally to a length of 1 to 1.5 centimeters. Anastomose the posterior part of the venous pouch with the arteriotomy of the left CCA using 10-0 sutures. Then suture the rear side of the venous pouch with the posterior wall of the right CCA with three to four sutures.
Suture the anterior anastomosis in the same sequence as demonstrated before. Release the temporal clip on the right CCA. Usually anastomosis leaks.
Use this to wash air and blood clots out. Then seal the anastomosis with fat derived from the subcutaneous tissue of the surgical approach and fibrin glue. After the surgery, intravenously administer acetylsalicylic acid maintaining a dosage of 10 milligrams per kilogram of body weight.
Apply transdermal fentanyl patch on the shaved region for three days to achieve postoperative analgesia. Subcutaneously administer low molecular heparin daily for two weeks to achieve postoperative anticoagulation. With the demonstrated regime, it was possible to achieve 0%mortality and patency in 11 out of 12 aneurysms.
The aneurysm lengths varied between 21.5 to 25.6 millimeters with neck widths ranging from 7.3 to 9.8 millimeters. An image of stent-assisted embolized giant aneurysm that was captured after the aneurysm retrieval is shown here. For giant aneurysms, it is important to begin the anastomosis on the rear side.
This gives better sight and control for the most challenging sutures of the procedure. Endovascular devices can be implanted and used for research on occlusion rates and device behavior. Afterwards, histopathological examination can show endothelization of devices and lesion pathology.
Examining the aneurysm wall using MR imaging followed by histopathological correlation could enhance the understanding of MR wall imaging in humans.
