ASTM_F_3067_-_14.pdf

Designation:F306714Guide forRadial Loading of Balloon Expandable and Self ExpandingVascular Stents1This standard is issued under the fixed designation F3067;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This document provides guidance for developing invitro test methods for measuring the radial strength or collapsepressure of balloon-expandable vascular stents and chronicoutward force of self-expanding vascular stents.1.2 This guide is applicable to balloon-expandable andself-expanding stents of tubular geometry.It covers both stentand stent grafts.It does not cover bifurcated stents.It does notcover stents with non-circular cross-sections or tapered stents.1.3 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.1.4 This guide does not recommend any specific test methodor apparatus for measuring the radial strength,collapsepressure,or chronic outward force.Instead,this guide providesexamples of test methodologies and equipment that could beused and recommends the format for presenting test results.1.5 This guide covers only in vitro bench testing methods.In vivo behavior might be different.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:E4 Practices for Force Verification of Testing MachinesE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsF2079 Test Method for Measuring Intrinsic Elastic Recoil ofBalloon-Expandable StentsF2081 Guide for Characterization and Presentation of theDimensional Attributes of Vascular StentsF2477 Test Methods for in vitro Pulsatile Durability Testingof Vascular Stents3.Terminology3.1 Definitions(alphabetically listed):3.2 balloon-expandable stenta stent that is expanded atthe treatment site by a balloon catheter.The stent material isplastically deformed by the balloon expansion such that thestent remains expanded after deflation of the balloon.3.3 chronic outward forcethe minimum continued open-ing force of a self-expanding stent acting on the vessel wall ata specified diameter.The range of chronic outward force isdefined by the unloading curve at the maximum and minimumindicated use diameters.Additional loading force consider-ations for self-expanding stents are evaluated as load excur-sions and described in Appendix X2.Chronic outward force isnot defined for balloon-expandable stents.3.4 collapse pressurethe uniform radial load during test-ing with a hydraulic or pneumatic apparatus in which aballoon-expandable stent undergoes buckling over a specificregion or the entire stent length.3.5 loada normalized,scalar value of force applied by thestent to the vessel and,at equilibrium,the vessel upon the stent.Load should be normalized by length(newton or millinewtonper millimeter length)or by area(pascal or kilopascal).3.6 loading linefor balloon-expandable stents,the linederived from the substantially linear portion of the radialloading curve during initial compression.The term is notdefined for balloon-expandable stents tested using collapsepressure apparatus.3.7 radial forceoutput of radial loading that equals theradial pressure times the stent cylindrical area.The relationshipbetween radial force(FR)and radial pressure(P)is given in theequation:P 5FRAwhere:P=radial pressure,FR=radial force,and1This test method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.30 on Cardiovascular Standards.Current edition approved Oct.15,2014.Published March 2015.DOI:10.1520/F306714.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 A=instantaneous stent cylindrical area:A 5 DLwhere:D=instantaneous stent expanded outer diameter,andL=Lofor length change less than 10%and L=L(D)forlength change greater than 10%.L:L0is the expandedstent length for balloon-expandable stents and uncon-strained length for self-expanding stents.L(D)is theinstantaneous length of the stent as a function of thecurrent instantaneous diameter.L(D)may be eitherexperimentally determined or computationally derived.3.8 radial loadinga mechanical loading mode in whichthe load is directed perpendicular to the longitudinal axis of acylinder and applied to the outer cylindrical surface of thestent.The load is applied to the entire outer surface or to atleast three areas that are equally distributed around the outercircumference and extend over the entire cylinder lengt