Mechanical Evaluation of Polyvinyl Alcohol Cryogels for Covered Stents

Covered stents could reduce restenosis rates by preventing cellular migration with a physical barrier and may have reduced thrombotic complications if an appropriate material is selected Previous Dacron (TM) or poly(tetrafluoroethylene) (PTFE) covered stents have had mixed clinical results in part because they are too thick and too thrombogenic at small diameters Ideally the covering should be as thin as a stent strut mechanically able to expand as much as a stent and durable enough to withstand deployment As an alternative to PTFE thin polyvinyl alcohol (PVA) cryo gel membranes were tested for their ability to stretch with uniaxial tension tests and for puncture strength with a modified ASTM method Additionally PVA cryo gel covered stents were made by coating ex panded bare metal stents These covered stents were then hand crimped onto a balloon catheter and expanded PVA cryogel membranes were made as thin as 100 mu m thinner than some stent struts and stretched to approximately 3 0 times their original diameter (similar to a stent during deployment) PVA cryogel membranes resisted puncture well with an average push through displacement of 477 mm allowing for safe deployment in vessels of up to 9 mm in diameter Push through displacement did not depend on membrane thickness in the range tested a trait that could reduce went profile without in creased risk of puncture All the PVA cryogel covered stents tolerated the crimping and expansion process well and there was little to no visible membrane damage In conclusion based on the results of these mechanical tests PVA cryogels are mechanically suitable for covered stent membranes This work represents a first step toward the creation of a new class of covered stent which could prevent complications from both restenosis and thrombosis [DOI 10 1115/1 4001863]