Mechanical heart valves (MHVS) are widely used for the replacement of natural valves as well as in ventricular assist devices and artificial hearts. Valves can cause blood damage which may lead to hemolysis and thromboembolism. Hemodynamic stresses imposed on blood elements as they pass through the valve play a major role in blood damage. In addition, the formation and collapse of cavitation bubbles near mechanical heart valves at closure have been implicated in both blood element and valve material damage. A related problem is the generation of stable gas bubbles by MHVs which show up as emboli in the cranial circulation and are detected as high intensity transient signals (HITS) in transcranial Doppler diagnostics. In the next grant period we will focus on determining the detailed mechanisms which lead to stable gas bubble formation on current MHVs and measuring the fluid stresses and flow structures very close to the valve housings. This study will provide the basic science required to support the development of a new generation of MHVs with reduced thromboembolic potential.
The specific aims of the proposed research are: 1. To observe the formation of stable gas bubbles on MHVs using C02-supplemented test fluids and HSV. Valves with observation windows in their housings will be used to record the bubble formation process at framing rates up to 10000 I sec. An ultrasound Doppler system will be used to quantify stable bubble formation rates. Modified valves (occluder material and gap width) will also be studied and the bubble formation process will be related to the fluid mechanical structures observed under specific aim 2. In this way we will be able to test the hypothesis that vortex structures sustain bubble growth from nuclei generated by cavitation. 2. To determine the near-valve flow characteristics during and shortly after valve closure that are associated with the generation of Stable gas bubbles and elevated turbulent stresses. We will modify existing valves by cutting windows into the metal valve rings (housings) which will allow us to observe and quantify fluid flow structures and turbulence levels very close to the housing where cavitation and stable gas bubble formation are initiated. By retaining most of the valve housing intact, we will not alter the normal valve closing dynamics and energy transfer. We will use LDV and high resolution PIV to assess turbulent stresses and focal flow structures. To further enhance our understanding of mechanisms, we will alter closing dynamics and flow structures by using different disk materials (Delrin and pyrolytic carbon), which are known to alter cavitation potential, as well as valves of the same materials but with different gaps between the occluder housing which are expected to generate different vorticity structures.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL048652-10
Application #
6765272
Study Section
Surgery and Bioengineering Study Section (SB)
Program Officer
Baldwin, Tim
Project Start
1993-05-01
Project End
2006-06-30
Budget Start
2004-07-01
Budget End
2006-06-30
Support Year
10
Fiscal Year
2004
Total Cost
$247,137
Indirect Cost
Name
Pennsylvania State University
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
003403953
City
University Park
State
PA
Country
United States
Zip Code
16802
Herbertson, L H; Deutsch, S; Manning, K B (2011) Near valve flows and potential blood damage during closure of a bileaflet mechanical heart valve. J Biomech Eng 133:094507
Herbertson, Luke H; Deutsch, Steven; Manning, Keefe B (2008) Modifying a tilting disk mechanical heart valve design to improve closing dynamics. J Biomech Eng 130:054503
Herbertson, Luke H; Reddy, Varun; Manning, Keefe B et al. (2006) Wavelet transforms in the analysis of mechanical heart valve cavitation. J Biomech Eng 128:217-22
Manning, Keefe B; Przybysz, T Michael; Fontaine, Arnold A et al. (2005) Near field flow characteristics of the Bjork-Shiley Monostrut valve in a modified single shot valve chamber. ASAIO J 51:133-8
Sohn, Kwanghyun; Manning, Keefe B; Fontaine, Arnold A et al. (2005) Acoustic and visual characteristics of cavitation induced by mechanical heart valves. J Heart Valve Dis 14:551-8
Herbertson, Luke H; Manning, Keefe B; Reddy, Varun et al. (2005) The effect of dissolved carbon dioxide on cavitation intensity in mechanical heart valves. J Heart Valve Dis 14:835-42
Johansen, Peter; Manning, Keefe B; Tarbell, John M et al. (2003) A new method for evaluation of cavitation near mechanical heart valves. J Biomech Eng 125:663-70
Manning, Keefe B; Kini, Vinayak; Fontaine, Arnold A et al. (2003) Regurgitant flow field characteristics of the St. Jude bileaflet mechanical heart valve under physiologic pulsatile flow using particle image velocimetry. Artif Organs 27:840-6
Bachmann, Christopher; Kini, Vinayak; Deutsch, Steven et al. (2002) Mechanisms of cavitation and the formation of stable bubbles on the Bjork-Shiley Monostrut prosthetic heart valve. J Heart Valve Dis 11:105-13
Meyer, R S; Deutsch, S; Bachmann, C B et al. (2001) Laser Doppler velocimetry and flow visualization studies in the regurgitant leakage flow region of three mechanical mitral valves. Artif Organs 25:292-9

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