1. 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
Group Project Updates Pt 1
a lite version of your BioE 1160 final presentation (remind everyone of the problem, show the original schedule and goals) that now include an update of your progress including successes and problems. 15 minutes max.

2. 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

3. Background

4. Filter Properties Neuroprotection (distal protection) filter
Polyurethane material for the basket
Nitinol tubing
Nitinol
Stainless steel
80-140µm pore size

5. 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
ii. Clearly state the customer and the customer requirements; clearly state the proposed solution to the problem (10%) All relevant information is obtained and used to support design recommendations.
Briefly describe the product or service, the user problems it solves, and the audience for which it is intended.
Explicitly address what you designed or redesigned
AccuNet
Angioguard

6. Design Requirements 99% capture efficiency Lay flush with vessel lumen
Biocompatible
Durable
Collapsible
For insertion and retrieval
ii. Clearly state the customer and the customer requirements; clearly state the proposed solution to the problem (10%) All relevant information is obtained and used to support design recommendations.
Briefly describe the product or service, the user problems it solves, and the audience for which it is intended.
Explicitly address what you designed or redesigned

7. Economic Considerations and FDA Regulation
Market Size:
$752M worldwide
Distribution
Medical Supply Companies
FDA Classification
Class II – Cardiovascular Diagnostic Device

8. 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

9. Initial Design Considerations
Incorporate the best features/materials from all current designs into our filter
Implement a novel feature to improve design

10. Proposed Solution Ring Three struts Polyurethane basket
70-80µm pore size
Skirt

11. 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

12. Prototype Fabrication
Shape nitinol into ring and reinforce with polyimide tubing
Attach stainless steel wire guidewire

13. Prototype Fabrication
Dimensions of filter Basket
Outline filter on nylon sheet
Cut out pattern and put together with polycyanoacrylate

14. Final Prototype

15. 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

16. 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

17. Schematic of Flow Loop Reservoir Peristaltic Flow Pump
Length = 20 cm
Point of Filter Deployment
Glycerin/Water solution (9:16)
Inline filter
Insertion Point of particles
Insertion Point of Filter (one-way valve)

18. Data Analysis
Embolic capture efficiency determined by:
ezANOVA
Between- and In-group comparison
Student’s Paired t-test

19. Trial 1: 98% capture efficiency!
Experimental Results
Trial 1: 98% capture efficiency!

20. Experimental Results (cont.)

21. Filter Comparison Chart
AngioGuard
AccuNet
FilterWire
Our Filter
Capture Efficiency *
*The modified capture efficiency data is presented here

22. 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

23. 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

24. Competitive Analysis for Prototype I
Weaknesses
Non-collapsible filter
Non functional delivery or retrieval method
Not a 1:1 scale

25. 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

26. 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