An experimental aneurysm model: a training model for neurointerventionalists

Reproducible animal models not only facilitate the pre-clinical assessment of aneurysm therapy but can also help in training for interventional procedures. The objective of this study was to find an animal model that can be used to test different endovascular occlusion techniques. Aneurysms in the right common carotid artery were created in 35 NZW rabbits by distal ligation and intraluminal elastase infusion. A total of 27 aneurysms were occluded by endovascular embolization with GDC-Coils. The time needed for placement of the microcatheter into the aneurysm by a professional interventionalist, a semi-professional interventionalist and a trainee was measured. The percentage of occlusion (occlusion rate) of the aneurysms was determined angiographically after embolization and again three months later, followed by a histological examination. Aneurysms of 2-6 mm size were reliably created in all 35 animals; mean size was 3.0 mm in height and 5.5 mm in diameter. Occlusion was achieved in 27 animals. Five animals from the group of 35 were initially planned as a control group with no embolization. We added to the control group one animal whose aneurysm could not be occluded endovascularly because of partial thrombosis and small size of the aneurysm. The angiographically determined mean occlusion rate was 89.5% +/- 11.3% standard deviation. Histological evaluation of the six aneurysms of the control group showed that they remained patent. Aneurysms that underwent embolization showed organized thrombus formation with no signs of recanalization. Two animals died from anaesthesia related or embolic complications. The time needed by the professional did not significantly decrease, after a little practice the trainee was nearly as quick as the professional. The beginner showed extensive progress, reducing the time for catheter placement by more than 50%. This paper describes the angiographic and histopathologic findings and also demonstrates possible methods for training in interventional procedures. Animal models will play a vital part in the training of future interventionalists. This model has the capability of testing different embolization devices (GDC, Onyx(R))and methods. Histologic long-term prognosis and the physical effect of the coils can be evaluated with this model.