Pulmonary Flow Resistive Device

1. Pulmonary Flow Resistive Device Taya Furmanski Albert Attia Advisor: Thomas Doyle, M.D. March 17, 2003

2. Background • Hypoplastic Left Heart Syndrome (HLHS) is a condition in which the patient is missing his/her left ventricle • 1440 babies are born each year with HLHS • Approximately 75% 3-year survival rate • No medical treatment for HLHS • Only options are operation (reconstruction) or transplantation • 300 patients with HLHS are seen at VUMC per year

3. The Problem • Inadequate systemic blood flow • Amount of O2 delivered to the organs decreases significantly • “Blue Baby” • Flow schematic

4. How to Solve the Problem • Place nozzle in pulmonary arteries (see figure for location) • Device will act as resistor • Decrease in pulmonary blood flow will cause increase in systemic blood flow • Eliminates first two steps of reconstructive surgery • Length of duration in heart = 6-8 months

5. 1-3 L/min Systemic Artery <1 L/min Systemic Artery 1 L/min Pulmonary Artery 2-3 L/min Pulmonary Artery 1 L/min Pulmonary Artery 2-3 L/min Pulmonary Artery 3-5 L/min Right Ventricle 3-5 L/min Right Ventricle Schematic of Flow with and without Device Implanted WITHOUT DEVICE WITH DEVICE

6. Dimensions of the Nozzle • Calculations by Craig Russell (ME student) • Theories required to solve problem • Conservation of mass • Conservation of momentum • Dimension of end of nozzle still to be determined • Pulmonary artery pressure ~20 mmHg 6-10 mm

7. Alternate Solutions • Place nozzle inside stent • Use bow-tie shaped stent (see figure) • Placing a mesh-like device in the pulmonary arteries

8. Problems With Alternate Solutions • Extremely difficult to place in the artery • Placement also a problem • Would cause hemolysis (tiny holes would damage red blood cells)

9. What We Need- Modeling - • In vitro model to simulate the blood vessels • Prototype can be tested through model to determine effectiveness • Computer model would allow variables to be altered easily to determine the optimal dimensions of the device

10. What We Need- Materials & Assistance - • Use Vanderbilt shop to mold conical device • Use materials to create physical model that accurately portrays operation of device • Assistance of mechanical engineering students (Craig Russell and Chris Owen) and professor (Dr. Mark Stremler) for fluid dynamics • Find experienced programmer to develop computer modeling system or use one currently in existence

11. Why Nitinol? • Biocompatible • Memory wire—can be molded to desirable shape • Can be elongated to fit into catheter, enabling insertion

12. What We Have Accomplished Thus Far… • In-depth research of HLHS • Several meetings with Dr. Doyle to discuss the problem and possible solutions • Finalizing a design plan • Create a plan of attack: start simple and increase complexity • Ordered and received nitinol wire • Calculations of fluid dynamics • Finalized method of implantation

13. What We Have Yet to Do… • Produce prototype of device • Test prototype • Use Mechanical Engineering lab to test pressure drop across device • Pressure drop calculations will allow proper calculation of dimension of the nozzle • Create or find computer model simulation of cardiovascular system

14. References • Barber, Gerald. Hypoplastic Left Heart Syndrome. Structural Congenital Defects, section 3. • www.ucch.org/sections/cardio/new/hlhs.html; date accessed: January 30, 2003. • web1.tch.harvard.edu/chnews/03-15-02/fetalcath.html; date accessed: February 10, 2003. • Dr. Thomas Doyle; Vanderbilt University Medical Center. • http://www.nemours.org/no/ncc/cardiac/crd1524.html