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: Currently Available Technology

• 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.

Performance Criteria

– Cardiovascular Model Specifications• Water tight• Portable • Anatomically representative• Axial Pump for generating pressure gradient in venous

system• Aesthetically pleasing• Hingeable heart

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, and potentially interchangeable model of inferior arterial flow, which may be easily visualized and modulated.

Solution Description

Develop a cardiovascular model with the following requirements• Insert and visualize catheters, intracardiac devices

intended for septum, and deliver stents • Apply venous flow (10 mmHg) to improve anatomical

representation• Introduce medical professionals and students to

protocols and devices

Solution Description: Adaptations to Current Design

• Remove upper half – decrease size, increase portability

• Connect pump to simulate blood flow through veins

• Acrylic tubes – prevent leaking, withstand pressure created by pump, ability to see inside vessels

• Access points – various medical devices to be tested and displayed

Goals

• This model will:– Be a useful, anatomically accurate tool for

physicians and medical device companies• Preliminary tests for devices• Instructional use for physicians

– Be portable in order to transport

Factors

• Cost– Materials

• Pipes, connectors, valves, heart casing– Labor/Machining

• Quality– Design of the new model

• Size, portability, water tight, aesthetically pleasing

• Benefits– Layout and modularity/size of model

• Potential conversion of venous model to arterial

Performance Metrics

• Outcome measurements– Ability of devices to be effectively used on the

model• Catheter manipulation, stent delivery, intrarticular

device mobility– Ability to transport easily and set up quickly– Water retention– Anatomical accuracy

Synthesis—System and Environment

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

Model Heart

http://medical-dictionary.thefreedictionary.com/bioprosthetic+valve

Design• Dimensions

– Inferior Vena Cava – 1 in interior Diameter (avg. diameter 20 mm) – Femoral Vein- .5 in interior Diameter (avg. diameter 10 mm)

• Solid Acrylic tubing sealed with Chloroform• Axial Pump generating ~10mmHg pressure• Approximating geometry of the heart• Hinging of right atrium• Bioprosthetic tricuspid valve• Modular construction• Selfhealing polymer to model septum

Experiment Block DiagramImprovements to initial design

Determine Cardiac Procedures to test

General Model Requirements

Aesthetic

Easily Viewable

Portable and quickly assembled

Design features to implement functions

Test Model Functionality

Refine

No Leaks

FINAL DESIGN

Closed CircuitDetermine heart functions to mimic

Hinge Heart

Pump

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

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.