View
217
Download
2
Category
Preview:
Citation preview
Redesign of a Distal Protection Filter for Carotid Artery Stenting
University of PittsburghSenior Design – BioE 1160/1161
Sandeep DevabhakthuniChenara JohnsonDaphne Kontos
Perry Tiberio
April 18, 2005
Mentor: Ender Finol, PhD
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
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
AccuNet
FilterWire EX
Angioguard
Design Requirements
• 99% capture efficiency
• Lay flush with vessel lumen
• Biocompatible
• Durable
• Collapsible
• For insertion and retrieval
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
• Incorporate the best features/materials from all current designs into our filter
• Implement a novel feature to improve design
Initial Design Considerations
• 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
Final Design
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
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
Insertion Point of Filter (one-
way valve)
Reservoir
Peristaltic Flow Pump
Length = 20 cmPoint of Filter Deployment
Glycerin/Water solution (9:16)
Inline filter
Insertion Point of particles
Data Analysis
• Embolic capture efficiency determined by:
• ezANOVA
• Between- and In-group comparison
• Student’s Paired t-test
100)___(
)1____(%
injectedparticlesmasstotal
filterinlineparticlesmassEfficiency
100)___(
)__(%
injectedparticlesmasstotal
filterparticlesmassEfficiency
Experimental Results
Particles Captured by Filter
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
0 2 4 6 8 10 12
Trials
Per
cen
t ca
ptu
red
Trial 1: 98% capture efficiency!
Experimental Results (cont.)
Modified Capture Efficiency
0.0
20.0
40.0
60.0
80.0
100.0
120.0
0 1 2 3 4 5 6
Trials
Per
cen
t ca
ptu
red
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
Recommended