1. Minimally Invasive Compressional Assist Device
TRIDORE MEDICAL Erika Brown, Caryl Brzymialkiewicz, and Mark Carlson
Advisor: Dr. Drew Gaffney, M.D.
Professor of Medicine, VUMC

2. Project Definition To design a cardiac assist device, implantable
with minimally invasive surgery that aids in
pumping, and in the case of a hypertrophic
heart, also improves function over time.

3. Cardiac Indications Systolic Ejection Fraction
Stroke volume _ End Diastolic Volume
Hypertrophic heart (e.g. Chagas disease)
sarcomeres expand and lose contraction efficiency
self-perpetuating positive feedback system
Frank-Starling Curve

4. What is currently available?
OPTIONS
Various drug treatments (ie - digitalis)(1776)
Intra-Aortic Balloon Pumping (1961)
Extracorporeal assist devices (1963)
Heart transplants (1967)
Total Artificial Hearts (1969-Cooley, 1982-DeVries)
Bridge-to-Transplant Implantable Ventricular Assist Devices (1978)
Batista’s wedge resectioning surgery (PLV) (1994)
PROBLEMS
Invasiveness
Cost
Mortality
Discomfort
Length of use
Aid in pumping or healing, but not both
Recipient limitations

5. Project Overview Brainstorming until end of January
Research until late February
In vitro model design and testing through mid-to-late March
Evaluation of in vitro results and adaptation into a prototype clinical design by end of the semester

6. What have we done so far? Password protected web page Patent search
Located pertinent cardiology and instrumentation resources
In-depth review of current technologies
Brainstormed wants and needs, possible design options, and potential problems to create a decision matrix
Developed rough sketch of design concept
Started brainstorming problems and solutions for various components of the design
Began biomaterials research
Began economic and safety analyses

7. Decision Matrix

8. What are we currently doing?
Working on a solid design for our in vitro model
Developing tests for the model
Trying to acquire components for testing and analysis
Finishing economic and safety analyses
Trying to set up viewing of cardiac surgery
MICAD Preliminary Design NOTE: Trigger, pumping, and power components are extracorporeal

9. Current questions...
What is the relationship between pressures applied on the outside of the heart and increased blood pressure?
How can we ensure a physiologically accurate inflation of the bladders?
Over a matter of weeks, how effective would a drawstring be in holding the device in place?
Are pericardial sutures a realistic option for increasing device stability?
What sorts of reciprocating pumps are currently available?
What fabric can offer the most support while retaining flexibility for implantation?

10. What will we do next? Research current pumping and triggering options
Acquire in vitro test and analysis equipment
Calculate necessary design parameters
Choose materials and actually construct an in vitro model
Research effects of applied pressures on healing hypertrophism

11. Resources
Committee to Evaluate the Artificial Heart Program of the NHLBI (1991) The Artificial Heart: Problems, Policies, and Patients. National Academy Press: Washington, DC.
Sherwood, L. (1997) Human Physiology: From Cells to Systems, 3rd Ed. Wadsworth Publishing Co.: Belmont, CA.
Quall, S.J., ed. (1993) Cardiac Mechanical Assistance Beyond Balloon Pumping. Mosby Year-Book, Inc.: St. Louis, MO.