Minimally InvasiveCompressional Assist Device

Erika Brown, Caryl Brzymialkiewicz, and Mark Carlson

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

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• Extracorporeal assist

devices• Heart transplants• Total Artificial Hearts• Ventricular Assist Devices • Batista’s wedge

resectioning surgery• Various drug treatments (ie

- digitalis)

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 mid-February• In vitro model design and testing through

mid-March• Evaluation of in vitro results and adaptation

into a prototype clinical design by end of the semester

What have we done so far?

• Web page is up and running• Patent search• Located pertinent cardiology and

instrumentation resources• Began in depth review of current technologies• Brainstormed wants and needs, possible

design options, potential problems

What are we currently doing?

• Continuing review of current technologies/devices

• Biomaterials research• Re-evaluating our problem and looking for

alternative solutions• Trying to set up viewing of cardiac surgery

Current questions...

• How much pressure should be applied to help the heart pump effectively?

• What is the most effective triggering mechanism?• Quantitatively, how much pressure is needed over

what length of time to help heal a hypertrophic heart?

• What are the anatomical constraints in implanting a device sub-xyphoidally?

What will we do next?

• Make a evaluation matrix of potential solutions

• Focus brainstorms on best solution and develop concepts for in vitro model

• Specify design parameters • Develop tests for in vitro model • Research Batista’s wedge resection surgery

Resources

• 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.