Characterization of explanted endovascular stents: A study of in-vivo corrosion and the role of vascular calcification in stent fracture.

摘要

The electrochemical and mechanical stability of endovascular stents in-vivo is essential for their biocompatibility. Limited information is available regarding the condition of stents following interaction with vascular tissue, as a result, twenty seven stented vessels containing 45 stents (33 bare metal and 12 drug eluting) were retrieved during autopsy and vascular surgery. The stent/tissue components were carefully separated using a rigorous tissue dissolution protocol. Stent surfaces were characterized using 3D digital optical and scanning electron microscopy. Transferred metallic elements in dissolved tissue were measured using mass spectroscopy. Histopathologic assessment of stented tissue, when available, was also performed. Fifteen out of the 33 bare metal stents underwent in-vivo corrosion (n=12) and fractures (n=3). Seven out of the 12 drug eluting stents had fractures. Microscopy images revealed mainly pitting and galvanic corrosion. Mechanical damage such as fretting of stents either overlapping other stents or vascular calcification was also observed. Tissue surrounding corroded stents contained a higher level of transferred metallic elements when compared to control and non-corroded samples. Multiple strut fracture occurred in stents placed in an overlapping configuration and/or under the presence of diffuse calcification. Fracture surfaces were consistent with a fatigue mechanism. Deposition of calcified matter on the stent struts was found to be a pattern in fractured cases. Tissue sections, at or near fracture sites, revealed development of in-stent restenosis and/or thrombosis. Electrochemical and mechanically-induced corrosion was observed on explanted stents. Heavy calcification appeared to contribute to stent fatigue and fracture. Both corrosion and fracture may impact the structural integrity of stents and influence local tissue responses.