Aortic Valve Function Under Support of a Left Ventricular Assist Device: Continuous vs. Dynamic Speed Support.

Area of Science:

• Cardiovascular Engineering
• Biomedical Devices
• Hemodynamics

Background:

• Continuous flow left ventricular assist devices (CF-LVADs) provide constant hemodynamic support to failing hearts.
• CF-LVADs alter aortic valve loading conditions, potentially leading to aortic insufficiency with long-term use.

Purpose of the Study:

• To investigate the impact of varying speed continuous flow left ventricular assist device support on aortic valve function.
• To determine if optimizing pump flow timing can mitigate adverse effects on the aortic valve.

Main Methods:

• Utilized a mock circulatory system with a Medtronic freestyle valve and a Micromed DeBakey CF-LVAD.
• Tested CF-LVADs at constant speeds (7500-11,500 rpm) to establish baseline outputs.
• Simulated varying speed support by adjusting pump flow timing, applying peak flow during systole and mid-diastole.

Main Results:

• Aortic valve ejection duration was longest when peak pump flow was applied at mid-diastole.
• Mean aortic valve area over the cardiac cycle was maximized with mid-diastolic peak pump flow.
• Altering the phase of the pump flow signal influenced aortic valve closing behavior.

Conclusions:

• Varying the timing of pump flow in CF-LVADs can positively impact aortic valve function.
• Applying peak pump flow during mid-diastole appears beneficial for aortic valve area and ejection duration.
• Optimized flow phasing may reduce aortic valve complications without compromising overall device support.