In Vitro Experiments and Redesign of a Distal Protection Filter Used in Carotid Angioplasty Stenting Procedures Erdrin Azemi Heather Gray Emily Miner Project Advisor: Ender A. Finol, Ph.D. Project Director: Mark H. Wholey, M.D. Senior Design BioE1160

Overview Distal protection filters are used during angioplasty stenting procedures to reduce the risk of stroke Distal protection filters are used during angioplasty stenting procedures to reduce the risk of stroke These filters are used in high risk patients where angioplasty with stenting is the only viable solution These filters are used in high risk patients where angioplasty with stenting is the only viable solution

Objective and Goals To perform in vitro flow motion analysis of several distal protection filters currently available in the marketTo perform in vitro flow motion analysis of several distal protection filters currently available in the market Angioguard ™, Accunett™, and FilterWire EX™Angioguard ™, Accunett™, and FilterWire EX™ Redesign a filter based on the results obtained from the in vitro experimentsRedesign a filter based on the results obtained from the in vitro experiments

Background Stroke is the 3rd leading cause of death in the U.S.Stroke is the 3rd leading cause of death in the U.S. Dislodging of atheroscleroticDislodging of atherosclerotic plaque increases the risk of stroke Schematic of Plaque in the Carotid Artery CarotidArterySurgery_4.html

1 Stent and Balloon Atherosclerotic plaque Filter 2 Retrieval Sheath 3 Trapped Plaque Angioplasty Stenting Procedure CarotidArterySurgery_4.html

Current Filters Shorter basket Longer wire 8 Struts Deeper basket 4 Struts Nitinol Ring Deepest basket CarotidArterySurgery_4.html

Current Filters Problems with current designs Possibility of missing small particles (low efficiency)Possibility of missing small particles (low efficiency) Difficulties in crossing tight and/or tortuous lesions (high profile)Difficulties in crossing tight and/or tortuous lesions (high profile) Somewhat cumbersome procedure (need to keep the wire extremely stable during catheter exchange)Somewhat cumbersome procedure (need to keep the wire extremely stable during catheter exchange) Potential to cause spasmPotential to cause spasm

Methodology Experimentation In vitro flow loop was used to test the efficiency of the three filtersIn vitro flow loop was used to test the efficiency of the three filters Out- Reservoir In - Reservoir Pump and Controller Pressure Transducer Flow Transducer Hemostatic Valve Injection Point of Particles Split Point Insertion of Filter 5 mm ID tube In-line filter A-B

Experimental Design 10 cm Apex- Broad Tape Tape 8 cm Apex- Acute Tape Tape 10 cm Proximal - Broad Not to scale A general procedure protocol was decidedA general procedure protocol was decided based on literature and experience based 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: Apex-AcuteApex-Acute Apex-BroadApex-Broad Proximal-BroadProximal-Broad 15 experiments were performed for each filter15 experiments were performed for each filter

Experimental Results AngioguardAccuNettFilterWire Proximal- Broad 96.81± ± ±12.57 Apex-Broad 90.69± ± ±2.93 Apex-Acute 98.7± Efficiency of the three filters expressed in percent

AngioguardAccuNettFilterWire Proximal- Broad 79± ± ±5.11 Apex-Broad 62.99± ± ±10.41 Apex-Acute63.27±19.02*100* 84.72±19.67 Experimental Results Efficiency of the three filters after retrieval expressed in percent

Design Alternatives Redesign a device based on FilterWire EX™ from information in literatureRedesign a device based on FilterWire EX™ from information in literature Alternative design of deployment and retrieval sheathsAlternative design of deployment and retrieval sheaths The most efficient components of each filter were incorporated into our redesignThe most efficient components of each filter were incorporated into our redesign This approach was chosen based on extensive usage of each filter and the results of the in vitro experimentsThis approach was chosen based on extensive usage of each filter and the results of the in vitro experiments

Deeper, pointed sack 120 µm pore size Easier conformability Smooth transition Low profile The Redesign

Redesign: Features & Benefits Features Deeper basket: captures plaque more efficientlyDeeper basket: captures plaque more efficiently Shorter wire 190 cmShorter wire 190 cm Optimization of Nitinol ring diameter for use in mm vessel sizeOptimization of Nitinol ring diameter for use in mm vessel size Redesign of strutsRedesign of struts User Benefits Lowers the risk of strokeLowers the risk of stroke Easier to keep the wire stable, less cumbersome procedureEasier to keep the wire stable, less cumbersome procedure Reduces spasm and vessel damageReduces spasm and vessel damage Increases Nitinol ring stabilityIncreases Nitinol ring stability

Engineering Modeling SolidWorks TM modeling was used to develop our redesignSolidWorks TM modeling was used to develop our redesign PhotoWorks used to visualize appropriate materialsPhotoWorks used to visualize appropriate materials Technology

Competitive Analysis Competitors Currently, there are several distal protection filters on the market. In our research, we tested the three filters previously mentioned. We considered these filters to be our direct competitorsCurrently, there are several distal protection filters on the market. In our research, we tested the three filters previously mentioned. We considered these filters to be our direct competitorsStrengths Relative to other competitors, our redesign pieced together the most efficient components of each of the filters testedRelative to other competitors, our redesign pieced together the most efficient components of each of the filters testedWeaknesses No in vitro tests were performed to assure proper function or efficiency of redesign. The redesign is assumed to be effective based on predicate devices experimental resultsNo in vitro tests were performed to assure proper function or efficiency of redesign. The redesign is assumed to be effective based on predicate devices experimental results

Economics of Redesign Angioplasty stenting procedure with use of a distal protection filter shows 50% reduction in stroke rateAngioplasty stenting procedure with use of a distal protection filter shows 50% reduction in stroke rate By the year 2010 it is estimated that 270,000 angioplasty stenting procedures will be performed using distal protection filters in the U.S aloneBy the year 2010 it is estimated that 270,000 angioplasty stenting procedures will be performed using distal protection filters in the U.S alone

ConstraintsRegulatory Class II medical device intended for one time useClass II medical device intended for one time use Over 20 predicate devicesOver 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 following:Since predicate devices exist a 50 patient feasibility study would need to be performed to prove the following: Conformability to vesselConformability to vessel Ease of passageEase of passage Efficiency of filterEfficiency of filter

Quality System Considerations ManufacturabilityMaterials Nitinol ring and struts with dynamic sizing in the 3.5 to 5.5 mm rangeNitinol ring and struts with dynamic sizing in the 3.5 to 5.5 mm range Polyurethane filter membrane composed of 120 micron poresPolyurethane filter membrane composed of 120 micron pores 190 cm PTFE coated stainless steel wire 190 cm PTFE coated stainless steel wireMethods 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 Management Fall 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 Management Spring 2004 Goals Meet with advisors on regular basisMeet 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 Chores Erdrin A. Heather G. Emily M. “Quality Control Manager” “Surgeon” of experiments “Countess of Beads” Analyzed the data Solid Works Modeling Experimental document control IntroductionMethods Results and Discussion Survey handling and monitoring Updated Design History file Wrote PDS and 510(k) application Put together final presentation Put together final paper

Acknowledgements Thank You: Christine ScottiChristine Scotti Mark Wholey, MDMark Wholey, MD Ender Finol, PhDEnder Finol, PhD Mark GartnerMark Gartner Bioengineering Department, University of PittsburghBioengineering Department, University of Pittsburgh Carnegie Mellon UniversityCarnegie Mellon University