A Study in the Design of an Accelerated Wear Tester that is Compatible with a Particle Image Velocimetry and High Speed Camera Setup

Open Access
Author:
Brown, Edward Alexander
Graduate Program:
Bioengineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 17, 2015
Committee Members:
  • Keefe B Manning, Thesis Advisor
Keywords:
  • Accelerated Wear Tester
  • Heart Valve
  • Particle Image Velocimetry
  • AWT
  • PIV
  • Artificial Heart Valve
  • Fluid Dynamics
Abstract:
Cardiovascular disease (CVD) is the leading cause of death in the United States. A subset of CVD affects the valves of the heart (HVD). Due to the aging population's susceptibility to HVD, it is a growing concern. Heart valve replacement is often necessary if the valve is beyond repair. There are two main categories of artificial heart valves that can be used for a replacement, mechanical and bioprosthetic. Although there have been many advances in artificial heart valve technology, there are still many problems that need to be addressed. One major problem for bioprosthetic heart valves is deterioration . This study aims to design an accelerated wear tester (AWT) that is compatible with a particle image velocimetry and high speed camera set up so that bioprosthetic heart valve deterioration can be studied at an accelerated rate. By using SolidWorks, a single chamber AWT was designed and its materials were modeled to determine if it could withstand the stresses of testing a heart valve at an accelerated rate. The design of the AWT needed to be able to meet FDA requirements for in vitro bioprosthetic heart valve testing. Simulations were run to determine if the AWT could test a bioprosthetic heart valve over 200 million open and close cycles, having the valve fully open and close during each cycle, while maintaining a minimum average transvalvular pressure of 100 mmHg during valve closure. Based on the initial tests, the AWT’s acrylic walls underwent loading stresses of 0.99 MPa, which is much smaller than acrylic’s fatigue life of 38 MPa. This means that the flow chamber walls will not break or crack while testing the heart valve over the valve's entire life span. The pressures induced by the AWT’s piston motor during its down-stroke (~135 mmHg) and its up-stroke (~ -120 mmHg) were large enough to fully open and close the valve during each heart beat. The piston’s up-stroke created a transvalvular pressure drop of 120 mmHg during valve closure, proving that the AWT will be able to meet all the FDA requirements for testing bioprosthetic heart valves. Future studies will need to be carried out to physically building the AWT.