Developing a Cardiovascular Model

1. Developing a Cardiovascular Model James Clear Chase Houghton Meghan Murphy

2. 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

3. Previous Design Design flaws to be addressed: Model leaks, not portable, no flow gradient, not easily drained

4. 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.

5. Performance Criteria • Cardiovascular Model Specifications • Water tight • Portable • Anatomically representative • Pulsatile flow • Aesthetically pleasing

6. 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 flowfor testing intracardiac procedures including stent and catheter delivery.

7. 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, .19 psi) to improve anatomical representation • Introduce medical professionals and students to protocols and devices

8. 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 • Polycarbonate tubing – can withstand high impact stress, high clarity • Polycarbonate glue – seal polycarbonate joints • Trocar at catheter access point– for entry of catheter and prevent back flow, collecting basin for any water loss

9. 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

10. 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

11. 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

12. Portable and quickly assembled Easily Viewable Aesthetic Experiment Block Diagram Test Model Functionality Refine Design features to implement functions Closed Circuit FINAL DESIGN Hinge Heart Pump No Leaks Determine heart functions to mimic

13. Design • Dimensions • Inferior Vena Cava – 1 in interior Diameter (avg. diameter 20 mm) • Femoral Vein- .5 in interior Diameter (avg. diameter 10 mm) • Solid polycarbonate tubing sealed with lexane polycarbonate glue • Metering bellows pump • Approximate geometry of the heart • Self healing polymer for model septum • Fit inside carry on luggage • 22” x 14” x 9”

14. Synthesis—System and Environment www.cvcu.com.au/images/cv_torso.jpg

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

16. Device Functions and Specs • Visualize catheter movement through device • high clarity polycarbonate tubing • Water tight venous system • Polycarbonate glue • Anatomically correct venous flow • Metering bellows pump- .2 psi, 1.6 l/min • Anatomically correct heart • Casted with clear flexible urethane

17. Design Specs • Polycarbonate tubing • Ober-Read SP80-30 bellows metering pump • Max 2.1 L/min flow rate • Weld-On 58 polycarbonate glue • 2900 psi bond strength after one week • Trocar – for inserting devices into pressurized model

18. 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

19. 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.