Effect of stent-graft compliance on endotension after EVAR

Purpose: To investigate whether, and to which extent, the type of graft has influence on the pressure in the aneurysm sac. Methods: The study consisted of a dynamic and a static experiment. In the dynamic experiment, a latex aneurysm was inserted into an in-vitro circulation model, with variable (80-180 mmHg) systemic systolic pressure and a pulse pressure of 40 mmHg. Seven types of devices were used to exclude the aneurysm: a latex reference graft, 3 stentless grafts made of different fabrics, and 3 different types of commercially produced stented grafts used for endovascular aneurysm repair (EVAR). The systolic and diastolic intra-aneurysm pressures (IAP) were measured, along with the pulse pressure. The mean IAP and pulse pressures were compared for each category of graft (stented/stentless) and for each graft. In the static experiments, the compliance of each graft and the latex aneurysm were determined by measuring the change in volume necessary to obtain a change in pressure. Furthermore, the IAP with each graft was measured in a nonpulsatile situation under systolic pressures varying between 60 and 140 mmHg. Results: The experiments showed that, with increasing systemic pressures, there was a small pressure (<5 mmHg) increase in the aneurysm, but there was no significant difference among grafts in the dynamic or the static experiments (p=0.12 and p=0.17, respectively). With the 3 stented EVAR grafts, there was less pressure transmission than with the 3 stentless grafts, but this difference was not significant (p>0.05). Conclusion: This in-vitro study demonstrated that there is a clinically irrelevant pressure transmission through the graft wall and no significant difference in the pressure transmission between stented and stentless grafts.