Endotension as a result of pressure transmission through the graft following endovascular aneurysm repair - An in vitro study

Background: endovascular aneurysm repair (EVAR) significantly reduces, but does not abolish aneurysm sac pressure, possibly because of trans-fabric transmission. Objective: to investigate how blood pressure is transmitted through different types of grafts into the aneurysm sac. Design: experimental study, in vitro. Methods: a latex aneurysm was inserted into an in vitro circulation model. The systemic mean pressure (SPmean) was varied from 50 to 120 mmHg. The grafts used for aneurysm exclusion were: thin wall polyethylene (PE), thick wall polyethylene (PE) and thin wall ePTFE. Mean aneurysm sac pressure (ASP(mean)) was measured, as was pulse pressure (ASP(pulse)). Results: at an SPmean of 70 mmHg, the ASP(mean) was 34 +/- 0.8 mmHg (polyethylene knitted, thick wall), 30 +/- 1.0 mmHg (polyethylene woven, thin wall), and 17 +/- 0.6 mmHg (thin wall ePTFE). The ASP(mean) increased with SPmean, the relationship depending on the graft material. Stiffer grafts were associated with lower ASP(mean) and ASP(pulse) (P < 0.001). Conclusions: the relationship between aneurysm sac mean pressure and systemic pressure (SP) depends on the graft material. These data highlights the need for further studies regarding endotension.