Puncture of stents implanted into veins and arteriovenous fistulas: an experimental study

Puncture of venous Wallstents and nitinol stents with dialysis needles was tested in an animal study.

In 15 sheep, divided into a group with prior surgical unilateral carotid-jugular shunt creation (9 sheep) and a second group without shunt creation (6 sheep), a self-expanding nitinol stent and/or a Wallstent were bilaterally placed into the jugular veins. After 1 month, 10 nitinol stents and 9 Wallstents were punctured weekly with a 15-gauge cannula over a period of 15 weeks. Stent patency was followed up by color-coded duplex ultrasound and angiography. After sacrifice, high resolution X-rays of the removed vessels were taken to assess stent deformation. From histological slices, neointimal thickness inside the stents was measured and analyzed statistically.

Puncturing of both the nitinol stent and the Wallstent was technically feasible. Stent deformations were not found. One stent stenosis, probably related to puncture, was observed. The pattern of intimal hyperplasia differed between the nitinol stent and the Wall-stent. Outward bulge of the vascular layers over the stent struts was greater in nitinol stents. In the relevant area in between the stent struts there was no significant difference in intimal thickness between the two types of stents. Intimal thickness was more pronounced in shunted than in nonshunted animals only in the Wall-stent subgroup (p = 0.025) and more pronounced in punctured than in nonpunctured stents only in the nitinol stent subgroup (p = 0.018).

Puncturing of stents was feasible without major short-term complications. Therefore, stent implantation into the punctured segment of a hemodialysis fistula may be indicated if there is no alternative treatment.