Redesign of a distal protection filter for carotid artery stenting
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University of Pittsburgh Senior Design – BioE 1160/1161. Redesign of a Distal Protection Filter for Carotid Artery Stenting. Sandeep Devabhakthuni Chenara Johnson Daphne Kontos Perry Tiberio April 18, 2005 Mentor: Ender Finol, PhD. Arterial Stenosis.

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Redesign of a Distal Protection Filter for Carotid Artery Stenting

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Redesign of a distal protection filter for carotid artery stenting

University of Pittsburgh

Senior Design – BioE 1160/1161

Redesign of a Distal Protection Filter for Carotid Artery Stenting

Sandeep Devabhakthuni

Chenara Johnson

Daphne Kontos

Perry Tiberio

April 18, 2005

Mentor: Ender Finol, PhD


Arterial stenosis

Arterial Stenosis

  • Narrowing of carotid arterial walls due to plaque build-up

    • Considered 3rd leading cause of death - Stroke

  • New, less invasive treatment:

    • Carotid Artery Angioplasty and Stenting

    • Problem: Possible embolization to the brain resulting in a stroke.

    • Solution: Embolic Protection Devices


Background

Background


Filter properties

Filter Properties

  • Neuroprotection (distal protection) filter

  • Polyurethane material for the basket

  • Nitinol tubing

  • Nitinol

  • Stainless steel

  • 80-140µm pore size


Problem statement

Problem Statement

  • Predicate devices include the FilterWire EX, AccuNet and Angioguard

  • These filters are 80-90% efficient

  • The goal of our design is to maximize emboli capture efficiency

FilterWire EX

AccuNet

Angioguard


Design requirements

Design Requirements

  • 99% capture efficiency

  • Lay flush with vessel lumen

  • Biocompatible

  • Durable

  • Collapsible

    • For insertion and retrieval


Economic considerations and fda regulation

Economic Considerations and FDA Regulation

  • Market Size:

    • $752M worldwide

      http://www.menet.umn.edu/~shayden/Neuro_report.pdf

  • Distribution

    • Medical Supply Companies

  • FDA Classification

    • Class II – Cardiovascular Diagnostic Device


Quality system considerations

Quality System Considerations

  • Manufacturability

    • Simple Design

    • Materials already used for other medical purposes

  • Human Factors

    • Easy to use for trained interventional cardiologists

      • To be determined through survey

    • Biocompatible


Initial design considerations

Initial Design Considerations

  • Incorporate the best features/materials from all current designs into our filter

  • Implement a novel feature to improve design


Proposed solution

Proposed Solution

  • Ring

  • Three struts

  • Polyurethane basket

  • 70-80µm pore size

  • Skirt


Final design

Final Design

  • Ring

  • One Strut

    • Extra Struts don’t assist in securing filter

  • Stainless steel wire

  • Nylon filter basket

    • Nylon due to material restrictions

  • Polyimide tubing to enforce nitinol ring

  • Pore size of 70-80µm

    • Captures smaller particles

  • Nylon skirt


Prototype fabrication

Prototype Fabrication

Shape nitinol into ring and reinforce with polyimide tubing

Attach stainless steel wire guidewire


Prototype fabrication1

Prototype Fabrication

Dimensions of filter Basket

Outline filter on nylon sheet

Cut out pattern and put together with polycyanoacrylate


Final prototype

Final Prototype


Intended method of use

Intended Method of Use

  • Collapse filter by pulling strut

  • Insert percutaneously

  • Deploy filter by releasing strut

    • Pre-shaped to align 20° to vessel wall

  • After procedure, retrieve into retrieval sheath


Experimental methods used to test device performance

Experimental Methods Used to Test Device Performance

  • Glycerin-water solution (9:16) in flow loop

  • Insert filter into loop

  • Set peristaltic flow to 150 mL/min

  • Inject embolic beads

  • Run for 5 minutes

  • Weigh beads passed and collected by filter


Redesign of a distal protection filter for carotid artery stenting

Peristaltic Flow Pump

Reservoir

Glycerin/Water solution (9:16)

Inline filter

Point of Filter Deployment

Length = 20 cm

Insertion Point of particles

Schematic of Flow Loop

Insertion Point of Filter (one-way valve)


Data analysis

Data Analysis

  • Embolic capture efficiency determined by:

  • ezANOVA

    • Between- and In-group comparison

  • Student’s Paired t-test


Experimental results

Experimental Results

Trial 1: 98% capture efficiency!


Experimental results cont

Experimental Results (cont.)


Filter comparison chart

Filter Comparison Chart

*The modified capture efficiency data is presented here


Discussion

Discussion

  • Nitinol ring cracked during trial 2

  • Bottom of filter tore during trial 6

  • Filters are designed for one time use only

  • Poor results due to:

    • Placement of filter

    • Retrieval mechanism


Competitive analysis for prototype i

Competitive Analysis for Prototype I

  • Strengths

    • Reduced pore size

      • 74 microns compared to 80 – 120 micron range of filters currently on the market

    • Skirt

      • Assists in maximizing capture efficiency

    • Deeper basket

      • Prevent loss during retrieval of filter


Competitive analysis for prototype i1

Competitive Analysis for Prototype I

  • Weaknesses

    • Non-collapsible filter

    • Non functional delivery or retrieval method

    • Not a 1:1 scale


Future

Future

  • Redesign flow loop to include:

    • Pressure Transducers

    • Latex Tubing

  • Redesign a second prototype to include:

    • Develop a deployment/retrieval mechanism

    • Use polyurethane as the filter basket material

    • Use nitinol tubing


Acknowledgements

Acknowledgements

  • Dr. Ender Finol

  • Sanna Gaspard

  • Mark Gartner

  • Special thanks to Drs. Hal Wrigley and Linda Baker whose generous gift made this project work possible

  • University of Pittsburgh, Department of Bioengineering

  • Carnegie Mellon University


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