An Animal Model of Abdominal Aortic Aneurysm Created with Peritoneal Patch: Technique and Initial Results

Abstract

The purpose of this study was to develop an abdominal aortic aneurysm model that more closely resembles the morphology of human aneurysms with potential for further growth of the sac. An infrarenal abdominal aortic aneurysm (AAA) model was created with a double-layered peritoneal patch in 27 domestic swine. The patch, measuring in average from 6 to 12 cm in length and from 2 to 3 cm in width, was sutured to the edge of an aortotomy. Pre- and postsurgical digital subtraction aortograms (DSA) were obtained to document the appearance and dimensions of the aneurysm. All animals were followed with DSA for up to 5 months. Laparoscopic examination enhanced by the use of laparoscopic ultrasound was also carried out in 2 animals to assess the aneurysm at 30 and 60 days following surgery. Histological examination was performed on 4 animals. All the animals that underwent the surgical creation of the AAA survived the surgical procedure. Postsurgical DSA demonstrated the presence of the AAA in all animals, defined as more than 50% increase in diameter. The aneurysmal mean diameter increased from the baseline of 10.27 +/- 1.24 to 16.69 +/- 2.29 mm immediately after surgery, to 27.6 +/- 6.59 mm at 14 days, 32.45 +/- 8.76 mm at 30 days (p < 0.01), and subsequently decreased to 25.98 +/- 3.75 mm at 60 days. A total of 15 animals died of aneurysmal rupture that occurred more frequently in the long aneurysms (> or =6 cm in length) than the short aneurysms (<6 cm in length) during the first 2 weeks after surgery (p <0.05). No rupture occurred beyond 16 days after surgery. Four animals survived and underwent 60-day angiographic follow-up. Laparoscopic follow-up showed strong pulses, a reddish external appearance and undetectable suture lines on the aneurysmal wall. On pathology, the patches were well incorporated into the aortic wall, the luminal wall appeared almost completely endothelialized, and cellular and matrix proliferation were noted in the aneurysmal wall. A reproducible technique for the creation of an infrarenal AAA model was developed using a peritoneal patch in swine. The aneurysm model proved to have potential for further growth of the sac and a tendency to rupture. Because of the growth potential, this might be a better model than those with a noncompliant aneurysmal wall for the preclinical evaluation of stent-graft devices.

An update on the etiology of abdominal aortic aneurysms: implications for future diagnostic testing

“…The anterior patch model was another successful physical model. In this technique, an oval patch made of a number of materials, jejunal patches [73], autologous patches [69,70] and peritoneal patches [71] have been tested and found to result in consistently sized aneurysms that preserved the collaterals. Many of the physical models have little physiological relevance to the molecular pathways involved in AAA development; however, they have provided a platform for the studying other pathways like biomechanics that drive progression and rupture.…”

“…The first physical model used a graft made of the inferior vena cava to replace a section of the infrarenal aorta in dogs, but the mortality rate was too high in the postoperative period to be a viable model [68][69][70][71]. To create an aneurysm that exhibited progressive sac growth, Whitbread et al used surgically interpositioned fusiform venous grafts into pig aortas [72].…”

A Canine Model of Proximal Descending Thoracic Aortic Aneurysm Created with an Autologous Pericardial Patch

“…The majority of these animal models are of aneurysms involving the abdominal aorta rather than the thoracic aorta. [11][12][13] Studies of creating animal models of thoracic aortic aneurysms were rare. Formichi et al created animal models of thoracic aortic aneurysms in mongrel dogs using polyester patches.…”

Experimental Models of Abdominal Aortic Aneurysms

“…More recently, Maynar et al described a version of the anterior patch model in swine where a 2-3mm wide segment of the aortic wall was resected following anterior aortotomy, and a double-layered oval peritoneal patch sutured to close the defect [99]. Aneurysm development in these animals was followed up with angiography as well as laparoscopic assessment and laparoscopic ultrasound and finally histological analyses.…”