Developing a Cardiovascular Model

James ClearChase HoughtonMeghan Murphy

Problem Statement

• No all-purpose cardiovascular model is currently commercially available. – Models are made for testing of a particular device

exclusively– No in vitro model exists for physicians to learn and

visualize cardiac procedures• Current model exists from last semester but

has design flaws and performance shortcomings

Problem Statement: Current Devices

• Patented model for fatigue testing of prosthetic tricuspid valve replacements. Model applies pressure on valve to mimic in vivo forward and backflow gradients.

• Agar gel model with characteristics of biological tissue used to model left ventricular and aortic chambers. Ultrasound imaged flow dynamics through bicuspid valve.

• Model testing ventricle assist devices pumping performance and quantifying flow dynamics. Resistance comparable to native heart present.

• Patented teaching model for complex cardiac surgery including repair of congenital heart defects. Clay open system model with detachable colored tubes.

Previous Design

Design flaws to be addressed: Not easily drained, model leaks, heart itself is not anatomically correct, not portable, no flow gradient

Leaking joints

Anatomically incorrect heart

Size and weight of base- not portable

Emptied by lifting model

Primary Objective

It is the purpose of this team to use the previously established model as a foundation for developing a heart model of the inferior venous flow for testing intracardiac procedures including stent and catheter delivery.

Specific Device Objectives

• Our device has been designed to:• Demonstrate catheters used as optical scopes in the

heart– Proof of concept for this scope device for potential investors

• Demonstrate Swan-Ganz catheters used to measure blood pressure in the heart– Perform right heart catheterization- measure pressures in the

heart

• Demonstrate catheter delivery to intended site using sail on catheter tip– Illustrated in model by water flow under pump generated

pressure gradient

Solution Description: Adaptations to Current Design

• Remove upper half – decrease size, increase portability• Connect metering bellows pump to simulate blood

flow through veins – Flow rate: 1.6 L/min– Pressure gradient: .2 psi

• Acrylic tubing – can withstand high impact stress, high clarity

• Acrylic dichloroethylene glue – welding joints • Multiple catheter access points– for entry of catheter

and prevent back flow, collecting basin for any water loss

Adapting Current Model

Device Functions and Specs

• Visualize catheter movement through device – high clarity acrylic tubing

• Water tight venous system– acrylic dicholoethylene glue

• Anatomically correct venous flow– Metering bellows pump-:.2 psi, 1.6 L/min

• Anatomically correct heart– Casted with clear flexible urethane

• Fit inside carry on luggage– 22” x 14” x 9”

Model Design

www.cvcu.com.au/images/cv_torso.jpg

Progress & Future Direction

• Make final 180 degree turns

• Manufacture modular Y-shaped connector with O-rings

• Explore casting with polyester resin to improve clarity

• Attempt manufacturing bored acrylic 4in sphere

2.5 in bend diameter

4 in

Heart Model Directions

~4 in diameter sphere

v= ~90mlv= ~30ml

Bored Acrylic Sphere Concept: Casting Acrylic Mold Attempt:

Validation

• Performance will be assessed by how physicians interface with device and how realistically the device models cardiac procedures

• Conclusions will be drawn on how the design implements intended design features– Portable, Transparent, Pump, Water-tight

• Physician input will be considered for future design improvements and used to identify drawbacks

Physician Specific Validation

• Does the model visibly demonstrate optical scope catheter use into the heart?

• Does the model demonstrate Swan-Ganz catheter use in the heart?– Is it possible to measure pressures in the heart (perform

right heart catheterization)?

• When catheter delivery is demonstrated, is it clear to observers what structures the model replicates?

References

• Appartus for Testing Prosthetic Heart Valve Hinge Mechanism. More RB et al., inventors. United States Patent US5531094. http://www.freepatentsonline.com/5531094.pdf accessed 12 Nov 2009.

• Durand LG, Garcia D, Sakr F, et al. A New Flow Model for Doppler Ultrasound Study of Prosthetic Heart Valves. Journal of Heart Valve Disease. [Internet] 2006 Nov 4 [cited 12 November 2009]; 17. Available from: http://www.icr-heart.com/journal/.

• Hertzberg BS, Kliewer Ma, Delong DM et al. Sonographic Assessment of Lower Limb Vein Diameters: Implications for the Diagnosis and Characterization of Deep Venous Thrombosis. AJR. May 1997; 168:1253-1257.

• Pantalos GM, Koenig SC, Gillar KJ, Giridharan GA, Ewert DL. Characterization of an adult mock circulation for testing cardiac support devices. ASAIO. Feb 2004; 50(1):37-46.

• Pediatric congenital heart defect model. United States Patent US7083418. http://www.patentstorm.us/patents/7083418/description.html accessed 12 Nov 2009.

• Replogle RL, Meiselman HJ, Merrill EW et al. Clinical Implications of Blood Rheology Studies. Circulation 1967; 36:148-160.