Unzipping of small diameter stents: An in vitro study. Issue 2 (13th August 2014)

• Record Type: Journal Article
• Authors: Sathanandam, Shyam K.; Haddad, Lauren M.; Subramanian, Saradha; Wright, Dena; Philip, Ranjit; Waller, Benjamin Rush
• Is Part Of: Catheterization and cardiovascular interventions. Volume 85:Issue 2(2015:Feb. 01)
• Page Start: 249
• Page End: 258
• Publication Date: 2014-08-13
• Subjects: Heart -- Diseases -- Diagnosis -- Periodicals; Cardiac catheterization -- Periodicals; 616.1207572
• DOI: 10.1002/ccd.25596
• Languages: English
• ISSNs: 1522-1946

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="ccd25596-sec-0001" sec-type="section"> <title>Objective</title> <p>The purpose of this study was to determine if small‐diameter stents can be unzipped in vitro.</p> </sec> <sec id="ccd25596-sec-0002" sec-type="section"> <title>Background</title> <p>Small‐diameter stents can relieve stenosis in infant blood vessels. As the child grows, refractory stenosis may result. If an implanted stent can be intentionally fractured along its length‐"unzipped, " it can be redilated to the eventual adult vessel diameter.</p> </sec> <sec id="ccd25596-sec-0003" sec-type="section"> <title>Methods</title> <p>Stents of diameters ≤6 mm were dilated using angioplasty balloons until they fractured. The change in length‐diameter (dL/dD ratio), and the yield‐point‐force (<italic>σ</italic><sub>y</sub>) for each stent was calculated.</p> </sec> <sec id="ccd25596-sec-0004" sec-type="section"> <title>Results</title> <p>Thirty‐four coronary (CS), 11 biliary, and 10 nitinol peripheral stents (median diameter = 4, 5, and 6 mm; range = 2.75–4.5, 4–6, 6 mm, respectively) were tested. Stainless‐steel (SS) CS unzipped predictably at twice their nominal diameter with minimal shortening (<italic>n</italic> = 24, median dL/dD = 0.4). Nitinol stents fractured in a disorganized fashion. The remaining stents unzipped, had disorganized fractures, and shortened significantly (dL/dD>1). A dL/dD ratio of<1 had a strong, positive correlation with the ability to unzip (Pearson rho = 0.94). By multivariate regression analysis, SS alloy, and closed‐cell design were found to be significant predictors (<italic>P</italic> < 0.05) for unzipping. Optimal cut‐off points for stents to unzip included, strut‐thickness = 112 µm, alloy‐density = 7.7 g/cm<sup>3</sup>, dL/dD ratio = 0.12 and <italic>σ</italic><sub>y</sub> = 108Mpa (Youden's index = 0.8, 0.4, 0.8, and 0.5, respectively).</p> </sec> <sec id="ccd25596-sec-0005" sec-type="section"> <title>Conclusions</title> <p>Stainless‐steel, coronary stents of a closed‐cell design unzip at twice their nominal diameter without significant shortening when serially dilated. This study may encourage the implantation of small stents in infant blood vessels and aid in selection of appropriate stent type. © 2014 Wiley Periodicals, Inc.</p> </sec> </abstract>