In-vitro wall shear measurements at aortic valve prostheses

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Fluid Dynamics

Background:

• Aortic valve prostheses are crucial for cardiovascular health.
• Understanding hemodynamic performance is key to reducing complications like blood trauma and thrombus formation.
• Previous studies suggest differences in blood trauma between mechanical valve types.

Purpose of the Study:

• To compare wall shear stress distributions in mechanical aortic valve prostheses (Starr-Edwards, Björk-Shiley, Lillehei-Kaster) during the cardiac cycle.
• To evaluate the influence of pulse rate on wall shear stress in disk valves.
• To correlate measured shear stresses with thresholds for shear-induced blood trauma and observed clinical outcomes.

Main Methods:

• Utilized hot film anemometry with flush-mounted wall shear probes in a pulsatile flow mock circuit.
• Measured wall shear stress distributions at the valve rings of different prosthetic aortic valves.
• Analyzed systolic and diastolic flow dynamics and their relationship to valve design.

Main Results:

• Systolic data indicated superior hemodynamic characteristics for disk valves (Björk-Shiley, Lillehei-Kaster) over ball valves (Starr-Edwards) concerning shear stress thresholds for blood trauma.
• Postoperative clinical studies confirmed lower lactate dehydrogenase (LDH) levels in patients with disk valves.
• High diastolic shear stresses were measured at the Björk-Shiley valve ring, linked to its non-overlapping closure mechanism.

Conclusions:

• Disk aortic valves demonstrate improved hemodynamic profiles and reduced blood trauma compared to ball valves.
• The Björk-Shiley valve's design may lead to increased risk of thrombus formation due to high diastolic shear stresses.
• Further investigation into valve design and flow dynamics is warranted to optimize prosthetic valve performance and minimize complications.