Endovascular Aortic Aneurysm Repair with Stent-Grafts: Experimental Models Can Reproduce Endoleaks

https://doi.org/10.1097/01.RVI.0000130816.33038.EDGet rights and content

PURPOSE

To develop canine aneurysm models that can reproduce type II endoleaks after endovascular aneurysm repair (EVAR) with stent-grafts.

MATERIALS AND METHODS

A fusiform infrarenal abdominal aortic aneurysm model (AAA) was surgically created with a jugular vein patch, while preserving collateral vessels (n = 3). To allow comparative studies within the same animal, a bilateral iliac aneurysm model was also constructed with venous patches and surgical re-implantation of the sacroiliac trunk (n = 3). Stent-grafts were implanted by femoral approach at least 2 months later in both aortic and iliac models. Follow-up imaging was performed by Doppler ultrasound (US) and angiography until animals were killed 3 months after EVAR.

RESULTS

Angiography revealed immediate type II leaks in all cases. Leaks were still present at autopsy 3 months after EVAR in all cases, and were revealed at pre-death angiography in all but one case. At autopsy, leaks were characterized by the presence of large endothelialized channels that formed within the thrombus between the stent-graft and the aneurysmal wall.

CONCLUSION

As shown in this pilot study, persistent type II leaks after EVAR can be reproduced in aortic and iliac animal models. The iliac model can be created bilaterally in the same animal, thus allowing for comparative evaluation of different therapies. These models could be used to better understand the mechanisms of endoleak, and to assess future developments aimed to improve the outcomes after EVAR.

Section snippets

AAA model

All protocols for animal experimentation were approved by the institutional Animal Committee in accordance with guidelines of the Canadian Council on Animal Care. Mongrel dogs were sedated with subcutaneous injection of acepromazine (0.1 mg/kg; Atravet, Ayerst Veterinary Laboratories, Guelph, ON, Canada), glycopyrrolate (0.01 mg/kg; Sabex Inc., Boucherville, QC, Canada), and meperidine (4 mg/kg; Sabex Inc.), and anesthetized with intravenous propofol (4 mg/kg; Diprivan 1%, AstraZeneca Canada,

RESULTS

In the three animals surviving AAA surgery, infrarenal abdominal aortic aneurysms measuring 87 mm (±12 mm) in length and 20 mm (±2 mm) in diameter were created (Fig 1). Angiography and Doppler US showed the presence of type II endoleaks in these three dogs immediately after stentgraft implantation. Leaks persisted at 3-month angiography in two of three dogs (Fig 1). In the third dog, a leak was detected at angiography and US at 3 weeks but not at 3 months; however, evidence of a leak was found

DISCUSSION

The mechanisms leading to endoleaks after EVAR are poorly understood. The development of an AAA animal model reproducing endoleaks is an important step for the study of mechanisms and exploration of potential solutions to prevent endoleaks. Large animals are required to study clinically applicable endovascular tools and their modifications. Aneurysm models created by overdilatation with balloon inflation with/without elastase infusion, or by surgery with venous/arterial patch, have already been

Acknowledgments

The authors thank Jocelyne Lavoie (endovascular procedure and planification), Hélène Héon (veterinarian), and Cédric Schmitt (US image management) for their participation in the animal studies, Guylaine Gevry for her assistance with artwork, and Dr. Guy Allaire, Dr. Lydia Whady, and Robert Spenard, from the Department of pathology of CHUM, for access to histological equipment.

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    This project has been funded in part by the Plateforme Technologique du CHUM, Montreal, and by a structuring group grant from Valorisation Recherche Quebec. It now benefits from the CIRREF grant program.

    1

    G.S. is a consultant for Medtronic Canada Ltd. and has identified a potential conflict of interest. None of the other authors have identified a potential conflict of interest.

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