DESIGN OF A MOCK CIRCULATORY FLOW LOOP

TO TEST TISSUE ENGINEERED HEART VALVE PROSTHESES

BIOENGINEERING SENIOR DESIGN 2007

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Design Process

The final product design must meet the following requirements.

Requirements concerning the general function of the loop:

	Be able to run the loop for 1-2 hours.
	Flow is pulsatile with a variable frequency of 40-100 beats per minute (BPM).
	A flow rate of 4-8 L/min.
	Temperature control at 25-40 oC ± 1oC (Preferably 37 oC).
	Total blood analog volume should be 1.5±0.5 Liters.

The general design of the loop will largely imitate those that already exist in the Artificial Heart Lab (AHL) since considerable time has already been invested in developing this part of the system. An overview of basic loop components and function is available.

Requirements concerning the valve mounting apparatus:

Imaging techniques (PIV or LDV) must be possible to study fluid dynamics.

	Blood analog needs to be chosen to work with desired imaging technique.
	The refractive index of the blood analog and the acrylic structures needs to be equal.

The Sinuses of Valsalva should be modeled in the acrylic model following the aortic valve being studied to mimic the turbulent conditions immediately following the aortic valve.

The apparatus should not put undue stress on the valve tissue and should hold the valve in a physiological position in imitation of the aortic position.

The valve test chamber must hold both a bioprosthetic valve that has a manufacturer installed sewing cuff and a porcine valve that will be excised in-house.

There may be a need to utilize some different components to adapt the design to both valve conditions.

All materials used should be inert and biocompatible.

With these requirements in mind several designs were proposed.

	A mechanism similar to that of the cases plumber's Teflon tape or medical tape.
	Two rings that have interlocking teeth.
	Two rings that are smooth.

At this point more knowledge of the nature of the porcine valves was required.

Excising some porcine valves provided information about the size and material environment immediately surrounding the aortic valve.

After discussion within the team and with Dr. Manning the design shown below was developed.

SOLID WORKS model of the Valve Test Chamber. Part A) connects to the VAD chamber. The valve is inserted between A) and B). Part C) is bent to allow for optical access; it leads to the first compliance chamber.

View upstream of the bioprosthetic valve configuration (left) and side view of bioprosthetic valve in test chamber showcasing sinuses of valsalva (right).

Page design by Daniel Bowers

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Last updated: April 30, 2007