Recent articles have brought to light a concerning issue known as stent-adjacent stenosis (SAS) in cases where iliac veins are stented. SAS refers to the narrowing of the non-stented vein next to a stent, which was not present before the stent placement. This narrowing is a biomechanical consequence of the Poisson effect. SAS is problematic because it reduces the diameter of the inflow vein, and this reduction is particularly crucial as venous inflow is a key predictor of patient outcomes. Additionally, SAS results in larger areas of low shear rate within the stented segment, a flow parameter strongly linked to in-stent restenosis and the need for further intervention.
The auxetic venous stent (not FDA approved) is a nitinol, self-expanding stent that elongates during radial expansion. This unique design generates both radial and longitudinal/axial forces on the vein wall tissue, in contrast to all previous stents that exert only radial force. This bidirectional application of force on the vein wall has the biomechanical result of mitigating the Poisson effect. Consequently, the auxetic venous stent is designed to achieve luminal gain in the stented segment without causing SAS, thereby preserving inflow and optimizing shear rate.