Minimally InvasiveCompressional Assist Device TRIDORE MEDICALErika Brown, Caryl Brzymialkiewicz, and Mark Carlson Advisor: Dr. Drew Gaffney, M.D. Professor of Medicine, VUMC
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.
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
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 What is currently available?
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
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
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 DesignNOTE: Trigger, pumping, and power components are extracorporeal
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?
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
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.