An investigation into the cause of distal endoleaks: role of displacement force on the distal end of a stent-graft.

Objective: To investigate if the forces developed by pulsatile flow on a stent-graft and dimensional changes of the graft material might contribute to distal endoleak and stent-graft kinking.

Methods: An in vitro experimental model was used to measure the peak displacement force developed by pulsatile flow pressure on the distal end of a stent-graft. Polytetrafluoroethylene (PTFE) graft material (110 mm long, 22 mm in diameter) was evaluated in a flow circuit, with water as the circulating liquid. In addition, the effect of internal pressure on PTFE graft dimensions was measured under nonpulsatile conditions in 3 configurations (1 bifurcated and 2 straight).

Results: Pressure in the PTFE graft did not cause a change in graft diameter but did increase the length of the graft. The mean load required to prevent retrograde displacement was 208.5+/-2.5 g. Peak retrograde displacement force developed on the distal end of the stent-graft by the pressure of pulsatile flow was strongly associated with the systolic phase of the cardiac cycle.

Conclusions: The distal end of the stent-graft is subject to a retrograde displacement force by the pressure of pulsatile arterial flow. In addition, pressure inside the PTFE graft causes its length to increase. Both of these factors may be important in the development of late complications of stent-grafting.