Modeling the Cardiovascular Inferior Venous System

Jim Clear, Chase Houghton, Meghan MurphyBiomedical Engineering, Vanderbilt University, Nashville, TN 37235

OBJECTIVES

1. Functional Catheterization and System TransparencyVeins and IVC:

• Clear tubing considered: Tygon silicone, polycarbonate, acrylic• Acrylic tubing used due to strength, ease of sealing, and thermoplasticity

Heart: • Clear Casting compounds considered: flexible urethane (70A & 80D)• Machined acrylic block used due to ease in carving symmetric designs

2. Water Tight • Acrylic materials: Joints tightly sealed with acrylic cement & dichloroethylene

Creating a Closed Circuit• Bent ½” acrylic tubes 180° using heat gun

Preventing Leaking at Inferior Vena Cava Bifurcation• 2 Y-connectors sealed with double o-rings

Catheter Ports• Rubber stopper seal & one way catheter sheath inserted through stopper for catheter port

3. Generating Flow Throughout Model• Adjustable metering bellows pump in closed circuit (1.2 L/min max )• Flexible silicon tubing connecting pump to model circuit; connected with

clamps over tube fittings• Lengthy silicon tubing allowing pump to be placed within ~5 ft radius of

model

4. Making the Heart Anatomically Correct• IVC directly enter right atrium• Castings- lack of clarity, inability to release• Built as 4 machined acrylic blocks

5. Decrease Weight, Increase Portability• Inferior venous system only• Modular Design

• O-rings allow for disassembly• Push on pump tubing

• CESEI. Patient Simulators. <www.cesei.org/simulators.php>• DYNAMIC MED DEMO. Demonstration Devices for the Medical Industry. <http://www.dynamicdemo.net/anatomical.html>• 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. • Short N. Technical and Historical Perspectives of Remote Sensing. <http://www.fas.org/irp/imint/docs/rst/Intro/Part2_26d.html>

• Improve external heart geometry: plaster of paris casting of cadaver heart • Adding superior venous system: further visualization of air embolism• Expanding to arterial system: arterial catheterizations/stent delivery• Heart valves: anatomically representative transition between chambers

REFERENCES

ACKNOWLEDGEMENTS

FUTURE WORK

CONCLUSIONS

PurposeDevelop a model of the inferior venous cardiovascular system for visualizing catheterizations and testing new catheter technologiesMethodsModel constructed considering specifications presented by Vanderbilt University Cardiology Fellow Dr. Michael Barnett, the relevant technology available, the design flaws of a previous prototype, and machining constraints Results Model achieved objectives presented by Dr. Michael Barnett and functioned in the catheterizations identified as specific device objectivesConclusionModel constructed has commercial and instructional applications. Expansion of model possible for simulating arterial systems or following progression of air embolisms

Problem StatementCurrent need for model offering unobstructed view of in vitro catheterizations • Proof of concept experimentation and demonstration for novel catheter

technology• Clinical training and visualization for various catheters

Specific Device Functions• Demonstrate optical scope catheters in heart: proof of concept• Demonstrate Swan-Ganz catheters: measure blood pressure in heart

Currently Available Technology

ABSTRACT

BACKGROUND

Special thanks to Dr. King, John Fellenstein and the Machine Shop, Dr. Barnett, Dr. Merryman, Alex Makowski, Andrew Cross, Ray Booker and the Vanderbilt Simulation Center

METHODOLOGY

1. Clear visibility of catheter movement2. Water tight system3. Anatomically representative flow

4. Anatomically representative heart5. Meet size constraints of carry-on

luggage: 22” x 14” x 9”

Figure 3. Bifurcation of the inferior vena cava at 60°

Figure 2. Initial prototype established under Dr. Barnett

Figure 1. Mentice VIST (left) & Dynamic Med Demo Peripheral Showcase Interactive (Right)

Anatomically Representative Internal Heart Geometry

VERIFICATION

Figure 5. Left: Mid esophageal Echocardiogram Center: ProE design Right: Machined Heart

Model Body (Avg)Femoral Vein .5 in. ID ~0.41 in (11 mm) IVC 1 in. ID ~0.81 in (20mm)Length IVC 9 in. ~14 in (37cm) *includes SVCRA Volume 1.53 in3 ~2.37 in3 (39 ml)Ventricle Volume 2.82 in3 ~3.6 in3 (60 ml)

• Mentice VIST Simulator ($40,000)• Dynamic Med Demo- Heart Valve Replacement ($8,000) and Interactive

Peripheral Showcase ($4,000)• Various models for device specific testing

Design Flaws of Previous PrototypeMajor Flaws:1. Leaks2. No Flow3. Cubic Heart4. Large5. Messy

• Established functional model with venous flow gradient and anatomical accuracy at low cost yielding diverse commercial and instructional catheter applications

Anatomically Representative Vasculature

Low Cost DesignSolid Acrylic $240

Acrylic Tubing $20

Pump $175Labor $1,900Septum Gaskets $20

Total ~ $2300

< ≈60°

RESULTS

Achieving Objectives:

1. Catheter visualization2. Water tight3. Venous flow gradient4. Correct internal heart geometry5. Modular to 13’’x6’’x6’’

Exception: base size28’’x16’’x6.5’’

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2.

3.

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Internal Heart Geometry

Symmetrical between Left and Right

Separated by various gasket materials representing septum

Atria: R: .7” H: .75”

Ventricle: R: .75” H: 1.2”

Figure 4. Inferior vena cava entry to right atrium