1、Designation: F3036 13Standard Guide forTesting Absorbable Stents1This standard is issued under the fixed designation F3036; 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 indicate
2、s the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This Guide covers select physical and mechanical char-acterizations of vascular stents with one or more absorbablecomponents. Such absorbable stents (also referred t
3、o as vas-cular scaffolds) are used to provide temporary luminal supportof the coronary and peripheral vasculature following interven-tional revascularization procedures. This Guide covers devicesthat are fabricated from one or more degradable polymersand/or metals (from this point on referred to as
4、“absorbable”).This Guide provides a framework for evaluating the change inselect physical and mechanical characteristics of absorbablestents from manufacture through their intended degradation invivo. Specific testing recommendations are limited to existingASTM standards for stent evaluation.1.2 Rec
5、ommendations specific to non-absorbable stentswith absorbable coatings are not within scope.1.3 Recommendations specific to testing absorbable stentgrafts are not provided here, however this standard has manyelements applicable to testing absorbable stent grafts.1.4 Clinical need dictates that absor
6、bable stents initiallypossess the same general dimensions and mechanical functionas their non-absorbable counterparts. Thus, utilization of al-ready established mechanical stent evaluation methods ispossible when absorbable test specimens are previously con-ditioned under physiologically relevant te
7、mperature and hu-midity. As a result, this standard addresses absorbable-specifictesting issues related to the mechanical and physical evaluationof these devices. This standard is limited to providingabsorbable-specific testing recommendations for evaluationswhere an ASTM method for durable (i.e., n
8、on-absorbable)stents is already available. Specifically, this standard providestesting recommendations for adapting the elastic recoil (ASTMF2079), securement/dislodgement (ASTM F2394), and three-point bending (ASTM F2606) tests to fully absorbable devices.This guide generally describes specimen con
9、ditioning, asappropriate, for absorbable devices, which can range fromnone to extensive depending on the measured attribute andrelevant clinical exposure conditions, including time in thein-use environment. There are additional stent evaluationmethods that are not addressed explicitly in this guide,
10、 e.g.,chronic durability, that may require absorbable-specific provi-sions. The user should justify the appropriate testing for thespecific polymer and device.1.4.1 While the primary purpose of this guide is to addressabsorbable stent-related issues specific to the tests described inSection 1.3, add
11、itional testing (e.g., radial strength) will likelyalso be needed. Thus, aspects of what is presented herein maybe applicable to additional relevant device attributes, such asthose described in ISO 25539-1 and/or 25539-2.1.5 This Guide may not be appropriate for all absorbabledevices, for example th
12、ose that possess limited hydrolytic orcorrosion susceptibility and degrade in vivo primarily throughenzymatic action. The user is cautioned to consider theappropriateness of the standard in view of the particularabsorbable device and its potential application.1.6 This Guide does not address the meth
13、ods necessary tocharacterize the chemical degradation of the absorbable stent(e.g., changes in mass, molecular weight, or degradants).However, this type of characterization does represent animportant component of the degradation profile and mecha-nism of the device. These characterizations are addre
14、ssed inASTM F1635.1.7 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.8 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
15、 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:2D618 Practice for Conditioning Plastics for TestingE6 Terminology Relating to Methods of Mechanical Testing1This test method is un
16、der the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.30 on Cardiovascular Standards.Current edition approved Nov. 1, 2013. Published December 2013. DOI:10.1520/F3036-13.2For referenced ASTM standards, visit the AS
17、TM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unite
18、d States1E122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or ProcessE1823 Terminology Relating to Fatigue and Fracture TestingF1635 Test Method forin vitro Degradation Testing of Hy-drolytically Degradable Polymer Resins and Fab
19、ricatedForms for Surgical ImplantsF2079 Test Method for Measuring Intrinsic Elastic Recoil ofBalloon-Expandable StentsF2394 Guide for Measuring Securement of Balloon Expand-able Vascular Stent Mounted on Delivery SystemF2477 Test Methods forin vitro Pulsatile Durability Testingof Vascular StentsF260
20、6 Guide for Three-Point Bending of Balloon Expand-able Vascular Stents and Stent SystemsF2914 Guide for Identification of Shelf-life Test Attributesfor Endovascular Devices2.2 Other Standards:3ISO 14630 Non-Active Surgical ImplantsGeneral Re-quirementsISO 25539-1 Cardiovascular implantsEndovasculard
21、evicesPart 1: Endovascular prosthesesISO 25539-2 Cardiovascular implantsEndovasculardevicesPart 2: Vascular stentsISO 10993-1 Biological evaluation of medical devicesPart1: Evaluation and testing within a risk managementprocessISO 10993-9 Biological evaluation of medical devicesPart9: Framework for
22、identification and quantification ofpotential degradation productsISO 10993-13 Biological evaluation of medical devicesPart 13: Identification and quantification of degradationproducts from polymeric medical deviceISO 10993-15 Biological evaluation of medical devicesPart 15: Identification and quant
23、ification of degradationproducts from metals and alloys3. Terminology3.1 Definitions:3.1.1 Unless otherwise defined in this standard, the termi-nology related to mechanical testing that is used in these testmethods will be in accordance with the definitions of Termi-nologies ASTM E6 and ASTM E1823,
24、and the respectivestandards described in the annexes of this document.3.1.2 absorbable, adjin the body, referring to an initiallydistinct foreign material or substance that either directly orthrough intended degradation can be excreted, metabolized orassimilated by cells and/or tissue.3.1.3 stent, v
25、ascular, na structure implanted in the nativeor grafted vasculature that is intended to provide mechanicalradial support to enhance vessel patency.3.1.4 conditioning, vpreparation of the device prior tomechanical testing to include elements that (1) affect theattribute to be tested, and (2) are impo
26、sed on device per clinicaland/or degradation timeline up to points of interest for theattribute.4. Significance and Use4.1 Absorbable cardiovascular stents provide temporarysupport to the vasculature and are intended to degrade andabsorb over time after being implanted into the vasculature.4.2 The t
27、est methods used to evaluate the mechanicalperformance of absorbable devices are similar to those used toevaluate permanent (non-absorbable) cardiovascular devices.The absorbable-specific pre-test conditioning requirements,handling requirements before and during the test, and time-dependent mechanic
28、al property evaluations for absorbabledevices are addressed here.4.3 As the absorbable implant degrades, the mechanicalperformance of the device also deteriorates. The key toachieving effective revascularization with absorbable devicesis to provide an adequate level of luminal support for the timefr
29、ame needed for vessel stabilization.5. Materials and Manufacture5.1 The manufacturer should ensure that materials used tomanufacture absorbable implants are suitable for implantinginto the body. General requirements regarding a materialssuitability for use as an implant are described in ISO 14630.Me
30、thods and guidance for assessment of biocompatibility canbe found in ISO 10993. There may be additional issues relatedto the biocompatibility of absorbable materials that are notcovered in ISO 10993.6. General Requirements and PerformanceConsiderations6.1 Absorbable StentsThe following consideration
31、s maybe important when determining the suitability of a stent for aparticular application. However, the test methods referenced asin the Annexes may not be appropriate for all types of implantapplications. The user is cautioned to consider the appropriate-ness of the test methods in view of the devi
32、ces being tested andtheir potential application.6.1.1 Performance Considerations:6.1.1.1 To better characterize the degradation and degrada-tion products of the absorbable stent, significant effort shouldbe undertaken toward developing an in vitro model for theanticipated in vivo degradation mechani
33、sm (e.g., corrosion,hydrolysis, etc.). Such a model would reflect the implantscomposition and any related interaction(s) with the physiologi-cally relevant aqueous solution, including as appropriate consideration of the influence of additives (e.g., anti-microbials), temperature, ionic composition a
34、nd strength, pH,and fluid flow conditions. This in vitro model might also beused to assess subsequent changes to the absorbable stent inlieu of animal experimentation.6.1.1.2 Composition/chemical properties in the finished,sterilized state and during degradation.6.1.1.3 Mechanical behavior of the fi
35、nished, sterilized de-vice and during degradation. Mechanical evaluation should becompleted for relevant device attributes including, but not3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.F3036 132limited to bending (e.g
36、., bending stiffness). Additional me-chanical characteristics may need to be evaluated to determinethe degree of vascular support and resistance to non-radialvessel deformation.6.1.1.4 While chronic durability should be assessed forabsorbable stents, this Guide does not specify methods toperform thi
37、s characterization. The user should justify theappropriate durability testing for the specific absorbable stent,including structural integrity and the potential for deviceembolization.6.1.2 Aging and Shelf Life Requirements:6.1.2.1 The user should establish the labeled shelf-life of theabsorbable de
38、vice through appropriate real-time studies ac-cording to ASTM F2914. A justification for attributes coveredin this guide not addressed as part of real-time studies shouldbe provided. Accelerated testing may be performed withappropriate justification.7. General Sampling, Conditioning, and TestingCons
39、iderations7.1 Apparatus, Equipment, and MaterialsThe test equip-ment should be maintained to the necessary precision andaccuracy, as appropriate for the specific device and functionaloutput being tested.7.1.1 Specimen ContainerA glass or plastic containercapable of holding the test specimen and the
40、conditioningsolution should be used. The container should be sealable toprevent solution loss due to evaporation, as appropriate.Multiple specimens may be stored in the same container,provided (1) suitable specimen separation is maintained toallow fluid access to each specimen surface (2) specimen-t
41、o-specimen contact is precluded, and (3) the environment isidentical.7.1.2 Conditioning/Soaking Solution:7.1.2.1 For absorbable stents manufactured from hydrolyti-cally degradable polymers, a physiologically relevant aqueoussolution should be used. (For more detail seeASTM F1635 andReferences contai
42、ned in Section X1.2)7.1.2.2 For absorbable stents fabricated from degradable(corrodible) metals, a physiologically relevant aqueous solu-tion with appropriate pH, buffer capacity, isotonicity, and ionconcentration should be used (e.g., artificial plasma: ISO10993-15). The user is cautioned that the
43、ions present in thesoaking solution (and in blood) may carry potential to chemi-cally react with the released metallic ions.7.1.2.3 If accelerated degradation is desired, changes intemperature, pH, or composition of solution may be used withappropriate justification.7.1.3 Constant Temperature Bath o
44、r Oven:7.1.3.1 An aqueous bath or oven capable of maintaining thespecimens at a physiologic temperature (37 6 2C) for thespecified testing periods should be used.7.1.3.2 The fluid environment should be well-mixed duringconditioning and mechanical testing.7.1.4 pH Meter:7.1.4.1 ApH metering device wi
45、th appropriate accuracy andprecision in the physiological range (pH 6 to pH 8) should beused.7.2 Specimen Acquisition however, the durations of each phase will vary depending onthe device material and design.7.3.1.1 The conditioning performed prior to evaluation of aspecific attribute should include
46、 all relevant exposures up to thefinal time point for the attribute (see 7.3.2). Relevant exposuresmay include humidity, flow, radial and non-radial cyclicdeformation, all of which need to be conducted under relevantthermal conditions.7.3.1.2 It may be necessary to measure additional functionalattri
47、butes of the device as dictated by the indications for useand/or failure mode.7.3.2 Upon introduction to the physiologically relevantaqueous solution, polymeric absorbable materials will uptakefluid prior to hydrolysis, which may affect some attributes. Forexample, stent radial strength may increase
48、 with fluid uptakeprior to a significant change in molecular weight. The usershould consider characterizing these dynamic attributes upondeployment of the device and during hydration, prior to asignificant decline in molecular weight. Such attributes shouldalso be monitored at multiple time points t
49、hroughout degrada-tion in order to characterize their change over time.7.3.2.1 If the time frame for fluid uptake is very short, itmay not be possible to measure some device functionalattributes after stable hydration and before onset of degrada-tion. In these instances, evaluation of device functional attri-butes at deployment as well as interim points at multiple timepoints during degradation may be adequate.7.3.2.2 The time required for the specimen to reach a stabletemperature and/or hydration state may extend longer than thetime frame for a particular attr
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