Mechanisms of cavitation and the formation of stable bubbles on the Björk-Shiley Monostrut prosthetic heart valve.
OBJECTIVE
Transcranial Doppler studies performed on patients with the Björk-Shiley Monostrut mechanical heart valve have detected signals typical of gaseous emboli.


METHODS
In this study, a high-speed digital imaging system was used to examine the closure event of the Björk-Shiley Monostrut valve in vitro.


RESULTS
Observations support the hypothesis that cavitation occurs before the formation of stable gas bubbles. Bubble cavitation occurs at the instant of valve closure and lasts on the order of 0.3 ms. The rebounding motion of the occluder initiates the development of a vortex which induces vortex cavitation. Vortex cavitation begins approximately 0.5 ms after impact of the occluder and the valve housing (approximately 0.2 ms after bubble cavitation has subsided), and lasts for approximately 1 ms. The formation of stable bubbles occurs later, along the center of the vortex that persists throughout much of the first rebound.


CONCLUSIONS
It is hypothesized that the low-pressure region at the center of the vortex contributes to the formation of stable bubbles by collecting expanded nuclei that arise from both bubble and vortex cavitation, and providing a low-pressure environment in which the nuclei combine and continue to grow.
Bachmann
Christopher
C
The Bioengineering Department, The Pennsylvania State University, University Park, USA.
Kini
Vinayak
V
Deutsch
Steven
S
Fontaine
Arnold A
AA
Tarbell
John M
JM
D001696:Biomechanical Phenomena; D004618:Embolism, Air / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology*; D006350:Heart Valve Prosthesis / Q000009:adverse effects*; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D011474:Prosthesis Design; D014463:Ultrasonography; D017725:Ventricular Pressure