In VitroIn Vitro Experiments and Redesign of a Experiments and Redesign of a Distal Protection Filter Used in Carotid Distal Protection Filter Used in Carotid

Angioplasty Stenting ProceduresAngioplasty Stenting Procedures

Erdrin AzemiErdrin AzemiHeather GrayHeather GrayEmily MinerEmily Miner

Project Advisor:Project Advisor: Ender A. Finol, Ph.D. Ender A. Finol, Ph.D.Project Director:Project Director: Mark H. Wholey, M.D. Mark H. Wholey, M.D.

Senior DesignSenior DesignBioE1160BioE1160

OverviewOverview

• Distal protection filters are used Distal protection filters are used during angioplasty stenting during angioplasty stenting procedures to reduce the risk of procedures to reduce the risk of strokestroke

• These filters are used in high risk These filters are used in high risk patients where angioplasty with patients where angioplasty with stenting is the only viable solutionstenting is the only viable solution

Objective and GoalsObjective and Goals

• To perform To perform in vitroin vitro flow motion flow motion analysis of several distal analysis of several distal protection filters currently protection filters currently available in the marketavailable in the market • Angioguard ™, Accunett™, and FilterWire EX™Angioguard ™, Accunett™, and FilterWire EX™

• Redesign a filter based on the Redesign a filter based on the results obtained from the results obtained from the in vitroin vitro experimentsexperiments

BackgroundBackground

•Stroke Stroke is the 3rd is the 3rd leading cause of leading cause of death in the U.S.death in the U.S.

•Dislodging ofDislodging of atherosclerotic atherosclerotic plaque plaque increases increases the risk of strokethe risk of stroke

Schematic of Plaque in the Carotid ArterySchematic of Plaque in the Carotid Artery

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11

Stent and Stent and BalloonBalloon

Atherosclerotic Atherosclerotic plaqueplaque

FilterFilter

22

Retrieval Retrieval SheathSheath 33

Trapped PlaqueTrapped Plaque

Angioplasty Stenting ProcedureAngioplasty Stenting Procedure

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Current Filters Current Filters

Shorter basket Shorter basket Longer wire Longer wire 8 Struts8 Struts

Deeper basket Deeper basket 4 Struts 4 Struts

Nitinol Ring Nitinol Ring Deepest basketDeepest basket

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Current Filters Current Filters Problems with current designsProblems with current designs

• Possibility of missing small particles Possibility of missing small particles (low efficiency)(low efficiency)

• Difficulties in crossing tight and/or Difficulties in crossing tight and/or tortuous lesions (high profile)tortuous lesions (high profile)

• Somewhat cumbersome procedure (need Somewhat cumbersome procedure (need to keep the wire extremely stable during to keep the wire extremely stable during catheter exchange)catheter exchange)

• Potential to cause spasm Potential to cause spasm

Methodology Methodology

ExperimentationExperimentation

• InIn vitrovitro flow loop was used to test flow loop was used to test the efficiency of the three filters the efficiency of the three filters

Out- ReservoirOut- Reservoir

In - ReservoirIn - Reservoir

Pump and ControllerPump and Controller

Pressure TransducerPressure Transducer

Flow TransducerFlow Transducer

Hemostatic ValveHemostatic Valve

Injection Point of ParticlesInjection Point of Particles

Split PointSplit Point Insertion of Filter5 mm ID tube5 mm ID tube

In-line filter In-line filter A-BA-B

Experimental DesignExperimental Design

10 cm10 cm

Apex- BroadApex- Broad

TapeTape  

TapeTape  

8 cm8 cm

Apex- AcuteApex- Acute

TapeTape  

TapeTape  

10 cm10 cm

Proximal - Proximal - BroadBroad

Not to scaleNot to scale

•A general procedure protocol was decided A general procedure protocol was decided based on literature and experiencebased on literature and experience•Blinded/Randomized ExperimentsBlinded/Randomized Experiments•To mimic the curvature of the carotid arteriesTo mimic the curvature of the carotid arteries

we used 3 different configurations:we used 3 different configurations:•Apex-AcuteApex-Acute•Apex-BroadApex-Broad•Proximal-BroadProximal-Broad•15 experiments were performed for each 15 experiments were performed for each filterfilter

Experimental ResultsExperimental Results

                 

 

AngioguardAngioguard AccuNettAccuNett FilterWireFilterWire

Proximal-Proximal-BroadBroad

96.8196.81±4.78±4.78 97.7397.73±3.94±3.94 90.8690.86±12.57±12.57

Apex-BroadApex-Broad 90.6990.69±12.15±12.15 99.299.2±1.09±1.09 98.6998.69±2.93±2.93

Apex-AcuteApex-Acute 98.798.7±2.24±2.24 100100 100100

Efficiency of the three filters expressed in percentEfficiency of the three filters expressed in percent

AngioguardAngioguard AccuNettAccuNett FilterWireFilterWire

Proximal-Proximal-BroadBroad

7979±14.79±14.79 76.32±28.8676.32±28.86 96.69±5.1196.69±5.11

Apex-BroadApex-Broad 62.9962.99±39.28±39.28 98.9498.94±1.54±1.54 90.77±10.4190.77±10.41

Apex-AcuteApex-Acute 63.27±19.0263.27±19.02

**

100100

**

84.7284.72±19.67±19.67

Experimental ResultsExperimental Results

Efficiency of the three filters after retrievalEfficiency of the three filters after retrievalexpressed in percentexpressed in percent

Design AlternativesDesign Alternatives

• Redesign a device based on FilterWire EX™ from Redesign a device based on FilterWire EX™ from information in literatureinformation in literature

• Alternative design of deployment and retrieval Alternative design of deployment and retrieval sheathssheaths

• The most efficient components of each filter were The most efficient components of each filter were incorporated into our redesignincorporated into our redesign

• This approach was chosen based on extensive usage of This approach was chosen based on extensive usage of each filter and the results of the each filter and the results of the in vitroin vitro experiments experiments

Deeper, Deeper, pointed sackpointed sack

120 120 µm pore sizeµm pore size

Easier Easier conformabilityconformability

Smooth transitionSmooth transition

Low profile Low profile

The RedesignThe Redesign

Redesign: Features & Benefits Redesign: Features & Benefits FeaturesFeatures

• Deeper basket: captures Deeper basket: captures plaque more efficiently plaque more efficiently

• Shorter wire 190 cmShorter wire 190 cm

• Optimization of Nitinol Optimization of Nitinol ring diameter for use in ring diameter for use in 3.5-5.5 mm vessel size3.5-5.5 mm vessel size

• Redesign of strutsRedesign of struts

User BenefitsUser Benefits

• Lowers the risk of strokeLowers the risk of stroke

• Easier to keep the wire Easier to keep the wire stable, less cumbersome stable, less cumbersome procedureprocedure

• Reduces spasm and Reduces spasm and vessel damagevessel damage

• Increases Nitinol ring Increases Nitinol ring stabilitystability

Engineering Modeling Engineering Modeling

•SolidWorksSolidWorksTMTM modeling was used modeling was used to develop our redesignto develop our redesign

•PhotoWorks used to visualize PhotoWorks used to visualize appropriate materialsappropriate materials

TechnologyTechnology

Competitive AnalysisCompetitive AnalysisCompetitors Competitors • Currently, there are several distal protection filters on the market. In Currently, there are several distal protection filters on the market. In

our research, we tested the three filters previously mentioned. We our research, we tested the three filters previously mentioned. We considered these filters to be our direct competitorsconsidered these filters to be our direct competitors

StrengthsStrengths• Relative to other competitors, our redesign pieced together the most Relative to other competitors, our redesign pieced together the most

efficient components of each of the filters testedefficient components of each of the filters tested

WeaknessesWeaknesses• No in vitro tests were performed to assure proper function or No in vitro tests were performed to assure proper function or

efficiency of redesign. The redesign is assumed to be effective based efficiency of redesign. The redesign is assumed to be effective based on predicate devices experimental resultson predicate devices experimental results

Economics of Redesign

•Angioplasty stenting procedure with Angioplasty stenting procedure with use of a distal protection filter shows use of a distal protection filter shows 50% reduction in stroke rate50% reduction in stroke rate

•By the year 2010 it is estimated that By the year 2010 it is estimated that 270,000 angioplasty stenting 270,000 angioplasty stenting procedures will be performed using procedures will be performed using distal protection filters in the U.S distal protection filters in the U.S alonealone

ConstraintsConstraintsRegulatoryRegulatory• Class II medical device intended for one time useClass II medical device intended for one time use

• Over 20 predicate devices Over 20 predicate devices

• To bring device to market:To bring device to market:• 510(k) required510(k) required

• PrototypePrototype

• Quality systems analysisQuality systems analysis

• Engineering analysisEngineering analysis

• Feasibility study in animalsFeasibility study in animals

• Since predicate devices exist a 50 patient feasibility study would need to be performed to prove the Since predicate devices exist a 50 patient feasibility study would need to be performed to prove the following:following:

• Conformability to vesselConformability to vessel• Ease of passage Ease of passage • Efficiency of filterEfficiency of filter

Quality System ConsiderationsQuality System ConsiderationsManufacturability Manufacturability

MaterialsMaterials

•Nitinol ring and struts with dynamic sizing in the 3.5 Nitinol ring and struts with dynamic sizing in the 3.5 to 5.5 mm rangeto 5.5 mm range

•Polyurethane filter membrane composed of 120 Polyurethane filter membrane composed of 120 micron poresmicron pores

• 190 cm PTFE coated stainless steel wire190 cm PTFE coated stainless steel wire

MethodsMethods

•Materials will be bought from suppliersMaterials will be bought from suppliers

•Assembly will occur in-houseAssembly will occur in-house

•Production will be in mass quantitiesProduction will be in mass quantities

Project ManagementProject ManagementFall 2003 GoalsFall 2003 Goals• Design History FileDesign History File

• Meet with advisorsMeet with advisors

• Literature ResearchLiterature Research

• Prepare PresentationPrepare Presentation

• Perform Preliminary TestsPerform Preliminary Tests

• Filter RedesignFilter Redesign

Project ManagementProject ManagementSpring 2004 GoalsSpring 2004 Goals• Meet with advisors on regular basis Meet with advisors on regular basis

• Perform experiments and analyze dataPerform experiments and analyze data

• Send out a Physician SurveySend out a Physician Survey

• Filter RedesignFilter Redesign

• Finish Design History FileFinish Design History File

• Final Paper and PresentationFinal Paper and Presentation

• Continue testing to finalize a manuscriptContinue testing to finalize a manuscript

Team ChoresTeam Chores

Erdrin A.Erdrin A. Heather G.Heather G. Emily M.Emily M.““Quality Control Quality Control Manager”Manager”

““Surgeon” of Surgeon” of experimentsexperiments

““Countess of Countess of Beads” Beads”

Analyzed the dataAnalyzed the data Solid Works Solid Works ModelingModeling

Experimental Experimental document control document control

IntroductionIntroduction MethodsMethods Results and Results and DiscussionDiscussion

Survey handling Survey handling and monitoringand monitoring

Updated Design Updated Design History fileHistory file

Wrote PDS and Wrote PDS and 510(k) application510(k) application

Put together final Put together final presentationpresentation

Put together final Put together final paperpaper

Put together final Put together final paperpaper

AcknowledgementsAcknowledgements

Thank You:Thank You:• Christine ScottiChristine Scotti

• Mark Wholey, MDMark Wholey, MD

• Ender Finol, PhDEnder Finol, PhD

• Mark GartnerMark Gartner

• Bioengineering Department, University Bioengineering Department, University of Pittsburgh of Pittsburgh

• Carnegie Mellon UniversityCarnegie Mellon University