Document Detail

Occluder closing behavior: a key factor in mechanical heart valve cavitation.
MedLine Citation:
PMID:  8061868     Owner:  NLM     Status:  MEDLINE    
A laser sweeping technique developed in this laboratory was found to be capable of monitoring the leaflet closing motion with microsecond precision. The leaflet closing velocity was measured inside the last three degrees before impact. Mechanical heart valve (MHV) leaflets were observed to close with a three-phase motion; the approaching phase, the decelerating phase, and the rebound phase, all of which take place within one to two milliseconds. The leaflet closing behavior depends mainly on the leaflet design and the hinge mechanism. Bileaflet and monoleaflet types of mechanical heart valves were tested in the mitral position in a physiologic mock circulatory flow loop, which incorporated a computer-controlled magnetic drive and an adjustable afterload system. The test loop was tuned to produce physiologic ventricular and aortic pressure wave forms at 70-120 beats/min, with the maximum ventricular dp/dt varying between 1500-5600 mmHg/sec. The experiments were conducted by controlling the cardiac output at a constant level between 2.0-9.0 liters/min. The measured time-displacement curve of each tested MHV leaflet and its geometry were taken as the input for computation of the squeeze flow field in the narrow gap space between the approaching leaflet and the valve housing. The results indicated rapid build-up of both the pressure and velocity in the gap field within microsecs before the impact. The pressure build-up in the gap space is apparently responsible for the leaflet deceleration before the impact. When the concurrent water hammer pressure reduction at closure was combined with the high energy squeeze jet ejected from the gap space, there were strong indications of the environment which favors micro cavitation inceptions in certain types of MHV.
Z J Wu; Y Wang; N H Hwang
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of heart valve disease     Volume:  3 Suppl 1     ISSN:  0966-8519     ISO Abbreviation:  J. Heart Valve Dis.     Publication Date:  1994 Apr 
Date Detail:
Created Date:  1994-09-22     Completed Date:  1994-09-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9312096     Medline TA:  J Heart Valve Dis     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  S25-33; discussion S33-4     Citation Subset:  IM    
Department of Biomedical Engineering, University of Miami, Coral Gables, FL 33124.
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MeSH Terms
Heart Rate
Heart Valve Prosthesis*
Materials Testing
Mitral Valve*
Models, Cardiovascular
Prosthesis Design
Pulsatile Flow
Stress, Mechanical
Surface Properties
Reg. No./Substance:

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