Preliminary studies on intimal injury related to stent retrieval in a canine model.

OBJECTIVE: This pilot study aimed to observe intimal injuries related to stent retrieval in the iliac artery of a canine.

BACKGROUND: In-stent restenosis remains challenging owing to permanent stent implantation. A retrievable stent may be alternative for intervention without permanent residue.

METHODS: Five retrievable stents with point-to-point overlapped double-layer scaffolds were deployed into the iliac arteries and retrieved on days 14, 21, 28, 35, and 42 from five canines.

RESULTS: Arterial diameter decreased by 9-10% before retrieval and 15% on day 14 after retrieval. In the 14-day-stent, the stent surface was clean without visible fibrin. In the 28-day-stent, the overlay was mainly composed of fibrin and fibroblasts. The proliferation of smooth muscle cells has not yet been observed with α-smooth muscle actin staining. In the 42-day-stent, endothelial and smooth muscle cells decreased under the struts, and the internal elastic lamina was interrupted segmentally. Neointima formation involves fibroblasts and smooth muscle cells. Neointimal thickness was negatively correlated with strut space. Stent traces on the artery wall tended to be flat at a follow-up14 days after retrieval. The primary intima was completely covered by neointima. Two stents could not be retrieved because of in-stent thrombosis or capture loss.

CONCLUSIONS: The stent was covered mainly by depositional fibrin after 28 days and by typical neointima after 42 days. The stent retrieval procedure did not induce injury to vascular smooth muscle, and the intima repair was performed 14 days after stent retrieval.