occluder device fatigue testing · paper focuses on pulsatile and axial fatigue testing ......

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OccluderDeviceFatigueTestingStructuralheartoccludersandclosuredevicesareusedtotreatcongenitalheartdefectssuchasatrialseptaldefect,ventricularseptaldefect,patentductusarteriosusandpatentforamenovale.Whiletherearenospecificstandardsforoccluderdevicetesting,manyofthecardiovascularimplantstandardssuchasISO5840-1(2015)coveraspectsofoccludertesting.ExecutivesummarydocumentsontheUSFDAwebsite(www.fda.gov)fromoccludermanufacturersforproductssuchastheAMPLATZER™PatentForamenOvaleOccluderfromSt.JudeMedical(nowAbbott)andGOREHELEX™SeptalOccluderfromW.L.Gore&Associates,Inc.,mightalsobehelpfulinidentifyingrelevantbenchtesting.Testexampleslistedinthesedocumentsinclude:fatiguetesting,tensilestrength,stressrelaxation,finisheddevicepressure,nickelleachability,particulatetesting,andcorrosiontesting.Whileourlaboffersparticulatetesting,nickelleachability,corrosiontesting,andotheroccludertests,thispaperfocusesonpulsatileandaxialfatiguetestingprotocols.PulsatileFatigue ElementMinnetonkaexcelsatpulsatilefatiguetestingofcardiovascularmedicaldevicesandhasdevelopedspecializedfixturesforoccludersandotherclosuredevices.Theimageontherightshowsastentgrafttesterconfiguredtoaccommodateventricularseptaloccluderdeviceswithacustom-designedfixturethatspecificallyloadstheneck/stemofthedevice.Devicesinthetestshownweresubjecttopulsatileradialfatiguefor100Mcyclestosimulate2.5yearsofimplantation;typicaltestsrangefrom40Mto600Mcycles.Afrequencysweepisconductedpriortothetestingtodetermineastableandsafetestingfrequencytominimizepotentialartifacts(i.e.,diametricexcursions)observedusinglasermicrometer,strobelight,orhighspeedvideocamera.Thetestisacceleratedtoobtainresultsinashortertime-periodthanphysiologicalrateswouldallowandisconductedundersimulatedphysiologicalenvironment,insalineat37±2°C. DevicesweretestedtomeettherequirementsoftheFDARecognizedConsensusStandardASTMF2477andFDAGuidance1545(2010):Non-ClinicalEngineeringTestsandRecommendedLabelingforIntravascularDevicesandAssociatedDeliverySystems.

Theimageontheleftshowsastentgrafttesterconfiguredtoaccommodatetwoclosuredevicesperstationwithspecializedmountingrequirements.Theobjectiveofthistestistodemonstratedeviceintegrityundermechanicalfatiguefor400McyclestomeettherequirementsforinvitromechanicalfatiguetestingstatedinASTMF2477andISO25539-1AMENDMENT1.Targetstrainisderivedfromcustomer-providedFEAanalysisbasedonworst-caseclinicalloadingconditions.

5929BakerRoad,Suite430·Minnetonka,MN55345·P:952.933.1152·F:952.933.1186·E:info.minnetonka@element.com

AxialFatigue Thetwoimagesbelowareexamplesofcustom-designedfixturesforoccluderandclosuredevicetensilefatiguetesting.Theyarebothmulti-specimenfixturesandcanaccommodatedevicesofdifferentdiameters.Insomecases,oneortwowedgesareplacedbetweentheplatestosimulateworst-casescenarioswhereoneorbothdiscsareatananglewithrespecttothestem.

Theimageontherightshowsamulti-specimenbendingfatiguefixturedesignedforpatentforamenovaleclosuredevices.Akeyadvantageofthedesignisthatitallowsbothpositiveandnegativebendingthroughaninflectionpointforeitherunidirectionalorbidirectionalbendingfatiguetests.Customer-providedFEAdataareusedtodefinethedesiredangulardisplacements,andtestingcantypicallybeacceleratedupto40Hz.Inspections Inspectionsareakeycomponentofanywell-designedtestprotocol.Devicesaretypicallyinspectedpriortotesting,duringthetestatpre-determinedintervalsandpost-testing.Duetothebraideddesignofmanyoftheoccluderandclosuredevices,itisimportanttolookforsignsoffrettingcorrosionthatmayoccurparticularlyinregionsofdisctostemoverlappingmaterial.AdditionalTestingFatiguetestingisonetypeofrelevantbenchtestingforoccludersandclosuredevices.Corrosiontesting,particulatetesting,nickelleachabilityandothermechanicaltestsmayalsoberequireddependingonyourdevice.Ifyouwouldlikeassistancewithyourdevice’sbenchtesting,pleasefilloutourtestquestionnaireorcallusat952-933-1152todiscusshowwecanhelp. ElementMaterialsTechnologyoffersthebroadestscopeofmedicaldevicetesting,soifyouarelookingforservicessuchaspackagetesting,microbiologicaltesting,acceleratedshelflifetestingorEMC/EMItesting,contactustoconnectwiththerightlab.