A standardized aortic aneurysm model for the assessment of endovascular stent-graft technology

Reliable models of aortic aneurysms are required to test endovascular stent-graft technology prior to human use. We describe the creation of a standardized prosthetic aneurysm in an ovine model to assess endovascular technology. In an adult ovine model under general anesthesia, a polyester sphere measuring 6 cm across was sutured onto the infrarenal aorta following aortotomy. Two weeks later an endovascular stent-graft was deployed in the aorta. Exclusion was confirmed on monthly ultrasound duplex and during angiography at three months and under terminal anesthesia at six months. Autopsy along with histology of the specimen were then performed. A total of 10 sheep underwent aneurysm implantation. Nine received a straight tube endovascular stent-graft (Lombard Medical, Abingdon, Oxon, UK) and seven completed the study. Five prosthetic aneurysms shrank during serial imaging with duplex ultrasound and angiography. However, two remained the same size. One of these had a type I endoleak whereas the other had endotension (type I endoleak confirmed at autopsy). This animal model provides a reliable and reproducible method of creating prosthetic aneurysms for assessing endovascular stent-grafts. It was possible to assess aneurysm exclusion non-invasively using duplex ultrasound. Aneurysms effectively excluded from the circulation shrank whereas those with an endoleak did not.