Title

Bioprosthetic heart valve leaflet motion under simulated physiologic conditions

Date of Award

1999

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Ned H. C. Hwang, Committee Chair

Abstract

The application of current bioprosthetic heart valves is limited by the lack of valve durability. Valve failure is thought to be related to uneven stress distribution within the leaflet, which is associated with subtle aspects of leaflet motion, such as excessive bending and wrinkling, during valve opening and closing in a cardiac cycle. However, detailed descriptions of the valve motion, particularly leaflet deformation, are not available in the literature. To address this problem, new metrological methodology, based on optical imaging techniques, was developed to assess the leaflet motion of bioprosthetic heart valves under simulated physiologic conditions.To investigate the realistic leaflet motion, which is strongly linked to the fluid flow through the valve, a new hydrodynamic testing loop was built from modifications of an existing design. While the new loop retained the main characteristics of the old loop, which closely simulates physiologic conditions, the design of an optical window permitted visualization of the valve leaflet in dynamic motion. These sequences of leaflet motion obtained under such accurately simulated physiological waveforms, as depicted in this dissertation, have never been previously reported.By designing a unique triggering mechanism, dual-camera stereo photogrammetry was developed. Instead of using stereo photogrammetry to investigate static or quasi-static valve leaflet surface contours, dynamic sequences of the leaflet motion in a complete valve opening and closing cycle were retrieved. In addition, introduction of the double-pulse illumination technique took advantage of the field transfer mechanism of the CCD camera and captured two consecutive images within a short time. A sequence of leaflet deformation diagrams from this technique was reconstructed for the first time.Also, structured light photogrammetry, using the Fourier transform fringe analysis method, was developed. It featured nondestructive surface contour assessment and automatic image analysis. This technique was successfully applied to obtain a leaflet surface contour sequence from a complete valve opening and closing process.Combined with the finite element method, the new methodologies developed in this dissertation, as described, can be employed to construct hybrid experimental-numerical design tools for the next generation of bioprosthetic heart valves.

Keywords

Engineering, Biomedical; Engineering, Electronics and Electrical; Health Sciences, Radiology; Physics, Optics

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9961258