Occluder closing behavior: a key factor in mechanical heart valve cavitation

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Fluid Dynamics

Background:

• Mechanical heart valves (MHVs) are crucial for patients with heart valve disease.
• Understanding leaflet dynamics is essential for optimizing MHV design and performance.
• Previous methods lacked the precision to capture rapid leaflet closing events.

Purpose of the Study:

• To precisely monitor and analyze the closing motion of mechanical heart valve leaflets.
• To investigate the influence of leaflet design and hinge mechanisms on closing dynamics.
• To explore the fluid dynamics within the valve gap during leaflet closure and assess cavitation risk.

Main Methods:

• Developed a laser sweeping technique for microsecond-precision monitoring of leaflet closing velocity.
• Utilized a physiologic mock circulatory flow loop with a computer-controlled magnetic drive.
• Computed the squeeze flow field using measured leaflet time-displacement curves and geometry.

Main Results:

• MHV leaflets exhibit a three-phase closing motion (approaching, decelerating, rebound) within 1-2 milliseconds.
• Leaflet closing behavior is significantly influenced by leaflet design and hinge mechanism.
• High pressure and velocity build-up in the valve gap precede impact, causing leaflet deceleration and indicating potential for micro cavitation.

Conclusions:

• The laser sweeping technique provides unprecedented precision in analyzing MHV leaflet dynamics.
• Understanding the three-phase closing motion and gap fluid dynamics is key to MHV development.
• Specific MHV designs may create conditions conducive to micro cavitation due to pressure dynamics during closure.