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Sugimoto, Hiroatsu (2003) EFFECTS OF LEAFLET STIFFNESS ON THE DYNAMIC MOTION OF THE AORTIC HEART VALVE. Master's Thesis, University of Pittsburgh. (Unpublished)

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The effects of valve leaflet mechanical properties on the dynamic geometry and function of the aortic heart valve are, to date, not well understood. This is largely due to the complex anatomy and solid-fluid interactions inherent in valve function. In the present study, the effects of leaflet stiffness on the dynamic aortic valve leaflet 3D geometry were quantified using a novel, non-contacting imaging system over the complete cardiac cycle. The imaging system utilized a structured laser-light imaging method, incorporated into a physiological flow loop, to project a high density matrix of laser dots onto the leaflet surface. The resulting dot pattern defined the leaflet surface, and was imaged by a pair of borescopes equipped CCD cameras providing stereographic views. From the image pairs, 3D dot coordinates were recovered using the direct linear transformation method. Five native porcine aortic heart valves were imaged, and then mechanically stiffened using a 0.625% aqueous glutaraldehyde fixation for 24 hours while under 4 mmHg transvalvular pressure. The valve was then re-imaged under near-identical flow conditions. Area, dimensional, surface curvature, and measurements were performed. We observed that: 1) the native valve elongates in the radial direction by ~30% when fully opened, and exhibited small, high frequency shifts in shape; 2) the stiffened leaflet demonstrated a more stabile shape, as well as focal regions of prolonged, high curvature; 3) the stiffened leaflet opens and closes faster by ~10 ms compared to native leaflet; 4) for both native and stiffened states, the aortic valve opened from basal region leading to free edge 5) when closing, both the native and stiffened state valve close with both free edge and circumferential together. Clearly, valve leaflet undergo complex geometric changes during the cardiac cycle, and leaflet mechanical properties (mainly stiffness) have a profound affect on leaflet dynamic geometry.Overall, the primary findings of this study were the extensive radial distension in the native state, and that an increase in leaflet mechanical stiffness induces high bending areas. The physiological function and advantage of the radial distension is currently unknown, but may affect the local hemodynamic patterns during valve operations, especially in the sinus regions. Our findings for the stiffened tissue have implications to valve design. For example, the high bending observed in the stiffened state correlated with known locations of tissue deterioration previously reported in our laboratory. Thus, in order to minimize leaflet tissue damage, methods of chemical modification utilized in bioprosthetic heart valves that maintain leaflet flexibility are necessary to minimize the onset and progression of tissue damage.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Sugimoto, Hiroatsuhisst5@pitt.eduHISST5
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairSacks, Michael Smsacks@pitt.eduMSACKS
Committee MemberStetten, George
Committee MemberAntaki, James Fantakij@pitt.eduANTAKIJ
Date: 12 May 2003
Date Type: Completion
Defense Date: 14 April 2003
Approval Date: 12 May 2003
Submission Date: 18 April 2003
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: MSBeng - Master of Science in Bioengineering
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: aortic; curvature geometry; porcine; stereo-photography; stiffness; valve
Other ID:, etd-04182003-160510
Date Deposited: 10 Nov 2011 19:38
Last Modified: 15 Nov 2016 13:40


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