Preload Sensitivity with TORVAD Counterpulse Support Prevents Suction and Overpumping.

Area of Science:

• Cardiovascular Engineering
• Biomedical Engineering
• Medical Devices

Background:

• Ventricular assist devices (VADs) are crucial for managing heart failure.
• Continuous flow (CF) VADs offer hemodynamic support but can have preload sensitivity issues.
• Counterpulsation VADs, like the toroidal VAD (TORVAD), aim to improve cardiac output while preserving native heart function.

Purpose of the Study:

• To compare the preload sensitivity of continuous flow (CF) VAD support against counterpulsation using the Windmill toroidal VAD (TORVAD).
• To evaluate the risk of overpumping and ventricular suction under varying preload conditions for both support types.

Main Methods:

• Utilized two lumped parameter models of the cardiovascular system: an open-loop model for ventricular function curves and a closed-loop model for physiological response.
• Assessed preload sensitivity by analyzing cardiac output versus left ventricular preload in the open-loop model.
• Evaluated the risk of left ventricular suction by monitoring end-systolic volume in the closed-loop model.

Main Results:

• At low preloads, CF support led to overpumping (4.7 L/min) compared to TORVAD (3.5 L/min).
• CF support exhibited significantly lower preload sensitivity (0.092 L/min/mmHg) than TORVAD (0.306 L/min/mmHg).
• In the closed-loop model, CF support caused ventricular suction events at elevated pulmonary vascular resistance, while TORVAD did not.

Conclusions:

• TORVAD counterpulsation preserves aortic valve flow and maintains physiological preload sensitivity.
• This approach effectively prevents overpumping and minimizes the risk of ventricular suction.
• TORVAD represents a potentially safer alternative for VAD support, particularly in managing preload variations.