Endovascular repair is a recently popularized technique for treatment of aortic aneurysms - a focal growth of human aorta that will eventually rupture if left untreated. In endovascular repair, the endovascular graft (EVG) - a vascular graft covered by stents - is passed through a femoral artery to the aneurysm. Here the EVG is deployed, so that it expands and pushes against the aortic wall, forming a blood-tight seal. Many commercial EVGs are equipped with barbs (protruding needle-like pins) at their proximal attachment site. The purpose of barbs is to penetrate the aortic wall during deployment and provide structural support against distal migration of the EVG. Distal migration of the proximal portion of the EVG causes endoleaks that may return the risk of aneurysm rupture to pre-repair levels. Although there have been many studies comparing commercial EVGs, there have seldom been controlled research studies that have assessed specific design variables of the EVG toward optimizing them. The result is that a significant number of EVGs tend to migrate distally over the first few years post-implantation increasing risk of post operative failure. Further, there are a wide variety of commercial EVG designs in the market and their relative merits are unclear, which forces the physician to make choices on devices and patient selection using questionable criteria. ? ? In this project, we propose to perform controlled in vitro studies to elucidate the effect of two key EVG design variables on the attachment strength of the graft-aortic wall interface. The design variables of interest are graft oversizing and barb length, both shown to be key determinants of graft migration risks. We shall custom-fabricate multiple EVGs with controlled variations in each of the design variables and deploy them in an in vitro system that simulates human endovascular repair. Subsequently, we shall explant the aorta-graft complex, perform imaging to study barb penetration characteristics and then determine the force required to separate the graft from the aortic wall. The overall objective is to identify the optimal combination of graft oversizing and barb length that maximizes graft attachment strength post-implant. We will further assess the interrelationship between design variables, penetration characteristics and attachment strength toward understanding the precise mechanisms by which the two design variables affect outcome. The findings from this study will aid physicians in making prudent, educated decisions on graft oversizing. It will also aid device manufacturers in designing EVG barbs that minimize migration risk. The proposed study is aimed at improving the design and hence performance of an implant that is used to treat patients with a major disease of the artery, namely aortic aneurysms. Over 3000 patients get this implant (called an endovascular graft) each year. Improvements in implant design will significantly improve post-operative quality of life for patients in the US and world-wide. ? ? ?
| Lin, Kathleen K; Kratzberg, Jarin A; Raghavan, Madhavan L (2012) Role of aortic stent graft oversizing and barb characteristics on folding. J Vasc Surg 55:1401-9 |
| Kratzberg, Jarin A; Golzarian, Jafar; Raghavan, Madhavan L (2009) Role of graft oversizing in the fixation strength of barbed endovascular grafts. J Vasc Surg 49:1543-53 |
