Minimally InvasiveCompressional Assist Device

Advisor: Dr. Drew Gaffney, M.D.Professor of Medicine, VUMC

TRIDORE MEDICALErika Brown, Caryl Brzymialkiewicz, and Mark Carlson

Project Definition

To design a cardiac assist device, implantablewith minimally invasive surgery that aids inpumping, 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

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

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

Decision Matrix

Design Sim

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W TOTALAttached 2 Bladder System with fabric shell 10 5 0 3 10 5 9 4 10 4 10 3 8 4 7 2 9 4 6 3 7 3 8 5 367Adjustible 2 Bladder System with fabric shell 9 5 0 3 10 5 9 4 10 4 10 3 8 4 7 2 9 4 6 3 7 3 9 5 367Finger Bladder System with fabric shell 10 5 0 3 10 5 9 4 10 4 10 3 8 4 7 2 5 4 6 3 7 3 6 5 341Spiral Bladder System with fabric shell 10 5 0 3 10 5 9 4 10 4 10 3 8 4 7 2 8 4 6 3 7 3 3 5 338Adjustible 2 Bladder System with spring reinforced fabric shell 8 5 0 3 9 5 9 4 9 4 9 3 8 4 7 2 7 4 6 3 7 3 7 5 332Attached 2 Bladder System with spring reinforced fabric shell 9 5 0 3 9 5 9 4 9 4 9 3 8 4 7 2 6 4 6 3 7 3 6 5 328Adjustible 2 Bladder System with hard shell 7 5 0 3 8 5 9 4 7 4 6 3 8 4 6 2 8 4 6 3 7 3 8 5 312Attached 2 Bladder System with hard shell 8 5 0 3 8 5 9 4 7 4 6 3 8 4 6 2 7 4 6 3 7 3 7 5 308Finger Bladder System with hard shell 9 5 0 3 8 5 9 4 7 4 6 3 8 4 6 2 5 4 6 3 7 3 6 5 300Spiral Bladder System with hard shell 9 5 0 3 8 5 9 4 7 4 6 3 8 4 6 2 8 4 6 3 7 3 3 5 297Attached Multi-Bladder System with orange peel 6 5 0 3 9 5 9 4 6 4 6 3 4 4 7 2 5 4 6 3 7 3 7 5 277Wide Band Mechanical Design 10 5 0 3 6 5 7 4 5 4 8 3 5 4 8 2 10 4 4 3 5 3 3 5 270Mechanical Finger Design with pull string 6 5 0 3 6 5 7 4 5 4 8 3 3 4 5 2 5 4 4 3 5 3 5 5 226Roller Bar System 5 5 0 3 4 5 4 4 6 4 8 3 3 4 5 2 9 4 4 3 5 3 3 5 209Mechanical Finger Design with Driving Motor 5 5 0 3 5 5 5 4 5 4 8 3 3 4 5 2 5 4 4 3 5 3 5 5 208

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.