Download Oral Presentation 4 - Research

Pulmonary Flow
Resistive Device
Taya Furmanski
Albert Attia
Advisor: Thomas Doyle, M.D.
April 9, 2003
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
The Problem
Inadequate systemic
blood flow
Amount of O2
delivered to the
organs decreases
significantly
“Blue Baby”
Flow schematic
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
Duration of implantation
in heart = 6-8 months
Schematic of Flow with and
without Device Implanted
<1 L/min
1-3 L/min
Systemic
Artery
2-3 L/min
Systemic
Artery
2-3 L/min
Pulmonary
Artery
Pulmonary
Artery
3-5 L/min
Right
Ventricle
WITHOUT DEVICE
1 L/min
1 L/min
Pulmonary
Artery
Pulmonary
Artery
3-5 L/min
Right
Ventricle
WITH DEVICE
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


Pressure drop across nozzle
required
Will conduct pressure tests to
solve for this unknown
Pulmonary artery pressure
~20 mmHg
Alternate Solutions
Place nozzle inside
stent
Use bow-tie shaped
stent (see figure)
Placing a mesh-like
device in the
pulmonary arteries
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)
What We Need
- Modeling Prototype can be tested through model
to determine effectiveness
In vitro model to simulate flow through
blood vessels
Computer model would allow variables
to be altered easily to determine the
optimal dimensions of the device
What We Need
- Materials & Assistance Use Vanderbilt shop to mold conical device
Use NCIIA to produce working prototype

Possibly have a company produce Nitinol prototype
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 calculations
Find experienced programmer to develop
computer modeling system or use one currently in
existence
Why Nitinol?
Biocompatible
Memory wire—can
be molded to
desirable shape
Can be elongated to
fit into catheter,
enabling insertion
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
Obtained materials necessary to test physical
model
What We Have Yet to
Do…
Produce prototype of device
Test prototype
Use Mechanical Engineering Energetics
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
Conclusions
Device will decrease blood flow to pulmonary
arteries,


Increase systemic bloodflow
Bypass first two reconstructive (Norwood)
surgeries
Nitinol is an adequate material for this device
Problem more complex than initially
anticipated



Fluid dynamics calculations
Unmeasured pressure difference
Device never created before
Recommendations
Continue pressure testing
In vivo testing

i.e. pigs, sheep
Human clinical testing
IRB approval
 FDA approval

References
1.
2.
3.
4.
5.
6.
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;
date accessed: February 25, 2003.
http://www.academicradiology.com/AR_2001/Jun01/5c
060100484p.PDF; date accessed: April 8, 2003.