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.

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

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

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

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

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

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

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 Shape nitinol into ring and reinforce with polyimide tubing Attach stainless steel wire guidewire

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

Final Prototype

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 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

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)

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

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

Experimental Results (cont.)

Filter Comparison Chart AngioGuard AccuNet FilterWire Our Filter Capture Efficiency 96.8 + 4.8 97.7 + 3.9 90.9 + 12.6 82.8 + 14.5* *The modified capture efficiency data is presented here

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 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 I Weaknesses Non-collapsible filter Non functional delivery or retrieval method Not a 1:1 scale

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 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