1. Noninvasive Stroke Prevention
BME Senior Design
Course Administrator: Paul H. King, Ph.D., P.E.
Advisor: J. Scott Williams, M.D., Ph.D.
Student Participant:Whit Miller
Noninvasive Stroke Prevention This is a BME senior design project developed under the direction of Dr. King of the BME department. Dr. Williams of Memphis serves as project advisor. My name is Whit Miller and I’m the student participant in this project.

2. Project Goals Lower stroke risk in patients Tailor therapy to carotid
Equal risk of surgery
Evaluate market
Evaluate the device safety
Plan for FDA approval

3. The Problem The Brain is most sensitive to decreased blood flow
500,000 Americans suffer a stroke every year
Carotid plaques responsible for over half

4. The Traditional Solution
Highly invasive surgery to remove a carotid plaque
Traditional drawbacks of surgery

5. The Alternative Stent Placement Outpatient or Overnight
No General Anesthesia
Same Results
Immobilization Vs Removal

6. Physical Characteristics
DIMENSIONS
5mm<length<80mm
5mm<diameter<30mm
GEOMETRIES
1) Collapsed (constrained) ~3mm (9F)
2) Expanded (unconstrained) achieved at deployment

7. Demands of the Carotid Stent must conform to contorted geometry
Device will be vulnerable
Imperative that plaque be immobilized

8. Meeting the Demands
Complex geometry, Vulnerability  use self-expanding stent
Plaque immobilizationuse a covered stent

9. Covered Stents Wrapped in a polymer such as Teflon®
Plaque is contained in a secure envelope
The struts of covered stents are wrapped in a polymer such as Teflon. The covering ensures that plaque at the deployment site cannot migrate back into the stent lumen by sealing it between the stent and the vessel wall.

10. Self-Expanding Stents
Excellent conformability
Extremely resilient
An alternative to balloon-deployed stents are self-expanding stents. Normally formed from a nickel-titanium alloy, these devices are sheathed on the catheter and expand passively. Their major advantage is their resistance to compression once deployed.

11. Ideal Stent Strut Design
Complete Apposition
High Visibility
Small, Predictable change in length

12. Optimal Covering Characteristics
An ideal covering will completely enclose the offending plaque
Porosity Vs. Restriction of expansion

13. Market Demand
Stents placed in 70% of the 750,000 angioplasty cases (US, 1999)
~$1500 per unit ($800 to >$5000)
Worldwide market > $2 billion in 1999

14. Device Safety
The clinical goals: reduced risk from diseased state, maintain flow, minimize possibility of emboli production
Ideally, risk (stenting) <= risk (surgical removal, endarterectomy)

15. FDA Approval
Currently, there are no FDA-approved stents designed for carotid applications.
A stent technology must be shown to be effective in animal models first
Likely to be approved for other applications
SAFETY and EFFICACY

16. Decision Tree
IWB