All sealed endoleaks are not the same:: A treatment strategy based on an ex-vivo analysis

Purpose: factors contributing to pressure transmission through thrombosed or sealed endoleaks have not been elucidated. The purpose of this investigation was to create an ex-vivo model that mimics patent and sealed endoleaks and that can quantitatively analyse the effects of length, diameter and thrombus on pressure transmission to the interior of the aneurysm sac. Methods: in the ex-vivo model, endoleak channels (ELCs) of various lengths (2 cm, 6 cm, 10 cm) and diameters (0.6 cm, 1.0 cm, 1.4 cm) were constructed using polytetrafluoroethylene (PTFE) grafts and attached to an artificial aneurysm sac. These ELCs were incorporated within a mock circulation made of rubber tubing connected to a pulsatile pump. Peak systolic pressure (PSP) was recorded in the aneurysm sac, distal to each ELC. Subsequently the ELCs were filled with human thrombus, and the pressure measurements repeated (n=5). Data was evaluated by regression analysis. Results: peak systolic pressure in the artificial circulation was maintained at 150 mmHg. In the absence of thrombus pressure did not change across the ELC, regardless of its length or diameter. In the presence of organised thrombus, the pressure curves distal to the ELC were dampened, and the pressure reduction was directly proportional to the length and inversely proportional to the diameter of the ELC. Regression analysis indicated statistical significance. Conclusions: in the absence of thrombosis, pressure transmitted via an ELC to the aneurysm sac is unchanged regardless of its length or diameter. All sealed endoleaks also transmit pressure. However, when an endoleak has thrombosed, pressure reduction is directly proportional to the length and inversely proportional to the diameter of its channel. This ex-vivo model suggests that Type 2 endoleaks with longer channels and smaller diameters would derive a greater benefit from adjunctive manoeuvres (coil embolisation) that hasten thrombosis. On the other hand, thrombosis of endoleaks with short and wide channels (e.g. Type 1) may not result in substantial pressure reduction within the aneurysm sac and a successful outcome.