In-vivo corrosion and local release of metallic ions from vascular stents into surrounding tissue.

OBJECTIVES

To evaluate retrieved bare metal vascular stents and surrounding tissue.

BACKGROUND

Limited information is available regarding the condition of stent surfaces and their interaction with vascular tissue following implantation. Corrosion of stents presents two main risks: release of metallic ions into tissue and deterioration of the mechanical properties of stents which may contribute to fracture. Release of heavy metal ions could alter the local tissue environment leading to up-regulation of inflammatory mediators and promote in-stent restenosis.

METHODS

Nineteen cases were collected from autopsy, heart explants for transplant, and vascular surgery (23 vessels containing 33 bare metal stents). A method was developed for optimal tissue dissolution and separation of the stent/tissue components without inducing stent corrosion. When available, chemical analysis was performed to assess metallic content in both the control and dissolved tissue solutions. Electron microscopy and digital optical microscopy imaging were used to evaluate stents.

RESULTS

Twelve of the 33 stents showed varying degrees of corrosion. Metallic levels in the tissue surrounding the corroded stents were significantly higher (0.5-3.0 mcg/cm² stent) than in control solutions (0-0.30 mcg/cm² stent) and in tissue surrounding stents that did not undergo corrosion (0- 0.20 mcg/cm² stent).

CONCLUSIONS

Corrosion of some retrieved stents is described which leads to transfer of heavy metal ions into surrounding tissue. The contribution of this metallic ion release to the mechanisms of in-stent restenosis as well as its effect on the mechanical properties of stents is unknown and requires further investigation.