Distribution of sac pressure in an experimental aneurysm model after endovascular repair: The effect of endoleak types I and II

Purpose: To study in an experimental aneurysm model the differential distribution of strain/pressure (S/P) on the aneurysm wall before and after endograft exclusion and in the presence of individual type I and type II endoleaks. Methods: Two tapered elliptical Gore-Tex patches were sutured to an anterior and posterior longitudinal arteriotomy of an 8-mm Gore-Tex tube graft, thus creating a fusiform aneurysm. Two S/P transducers were placed at the proximal sac adjacent to the proximal neck, 2 at the site of the widest sac diameter, and 2 at the sac adjacent to the distal neck. The aneurysm, which was connected to a pulsatile pump system, was excluded using a 10-mm endograft. Type I and type II endoleaks were created and tested individually. S/P measurements were obtained at systemic systolic pressures (BP) of 80, 110, and 150 mmHg. Thrombosis of the sac contents was induced by injection of thrombin and calcium in the sac. Angiography was used to verify presence or absence of flow in the sac. Results: Aneurysm exclusion resulted in significant S/P reductions at all 3 BP levels versus prior to exclusion (p<0.05). Thrombus in the sac did not alter S/P in the excluded sac (p>0.05 for all 3 BP levels). In the presence of a proximal type I endoleak, S/P distribution was not uniform, and S/P at the proximal neck was close to S/P prior to exclusion (p>0.05 no graft versus type I endoleak for all 3 BP levels). This was also true in the presence of thrombus. With a type II endoleak, S/P was more evenly distributed and was not significantly elevated compared to the pressure without an endoleak (p>0.05, graft versus type II endoleak for all 3 BP levels). Thrombus had no effect on intrasac S/P with a type II endoleak. Intrasac S/P was significantly higher in the presence of a type I endoleak compared to a type II endoleak when BP=150 mmHg (p=0.008). Conclusions: Endovascular exclusion of an aneurysm results in uniform S/P reduction in the aneurysm sac. Type I endoleak, but not type II endoleak, results in significantly higher S/P in an area of the sac adjacent to the proximal neck. Thrombus does not result in significantly different S/P distribution in the aneurysm sac.