Noninvasive Stroke Prevention BME Senior Design 2000-2001 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.

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

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

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

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

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

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

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

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.

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.

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

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

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

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

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

Decision Tree IWB