Ventricular Assist Device Speed Modulation for Aortic Valve Control
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Solution Overview
Problem
Current rotary Ventricular Assist Devices (VADs) face challenges in dynamically adjusting speed to match changing patient conditions, leading to potential underperfusion or vessel collapse, and lack effective non-invasive monitoring to ensure optimal cardiac support and valve functionality.
Innovation Solution
Implementing a speed modulation method where the rotary blood pump's rotational speed is periodically changed between two values, with feedback signals measured to determine the native heart's response, allowing for automatic adjustment of the mean speed to ensure the aortic valve opens during contractions, thereby improving monitoring and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the VAD operates at a low speed, then energy consumption is reduced, but underperfusion of the circulatory system occurs
Solution Approach 1:
The VAD speed is changed from constant operation to dynamic modulation, where the rotational speed varies periodically around a mean value. This dynamic operation allows the system to maintain adequate perfusion through speed variation while operating at a lower mean speed, reducing overall energy consumption compared to maintaining a constantly high speed.
Solution Approach 2:
The invention implements periodic speed modulation where the VAD operates at alternating higher and lower speeds within a cardiac cycle. This periodic action ensures that during the higher speed phases, adequate perfusion is maintained, while the overall mean speed remains lower, balancing perfusion requirements with energy conservation.
2Productivity
If the VAD operates at a high speed, then perfusion is improved, but vessel collapse and suction events occur
Solution Approach 1:
By dynamically modulating the speed rather than maintaining a constantly high speed, the system achieves adequate perfusion during high-speed phases while limiting the duration and extent of high-speed operation, thereby preventing sustained vessel collapse and suction events that would occur with continuous high-speed operation.
Solution Approach 2:
The VAD operates at excessively high speeds only partially during specific phases of the modulation cycle, sufficient to achieve the required perfusion, but not continuously. This partial excessive action provides the necessary perfusion boost without sustaining the harmful conditions of vessel collapse and suction.
3Ease of operation
If fixed speed control is used, then device operation is simple, but the system cannot adapt to changing patient conditions
Solution Approach 1:
The invention incorporates feedback from physiological measurements (such as aortic valve status, pressure, or flow) to automatically adjust the VAD speed modulation parameters. This feedback mechanism enables the system to adapt to changing patient conditions while maintaining a relatively simple operational interface, as the adaptation occurs automatically based on measured physiological parameters.
Solution Approach 2:
The VAD system performs self-adjustment of its speed based on intrinsic physiological feedback, reducing the need for continuous manual intervention. The device monitors its own operation and the patient's physiological state, automatically modulating speed to maintain optimal performance as conditions change.
4Measurement precision
If invasive monitoring methods are used, then accurate physiological data is obtained, but patient comfort is reduced and procedural complexity increases
Solution Approach 1:
The invention uses the VAD's existing motor currents and voltages as an intermediary to indirectly measure physiological parameters such as pump head pressure, flow, and aortic valve status. This approach obtains accurate physiological data without requiring separate invasive sensors, as the electrical signals from the motor provide information about the mechanical and physiological state of the system.
Solution Approach 2:
The VAD uses its own operational signals (motor currents, voltages, and power consumption) to derive physiological information about the patient's condition. This self-service approach eliminates the need for additional invasive monitoring equipment, reducing both patient burden and system complexity while maintaining measurement accuracy.
Data Source
AI summary
The invention relates to a method of controlling the speed of a ventricular assist device, in particular the rotational speed of a rotary blood pump, wherein at least temporarily the speed of the device is modulated around a mean speed and a response of the native heart to this modulation is measured to determine the ventricular function/contractile state of the heart, in particular to determine whether the aortic valve opens and closes at the instant mean speed, and the mean speed is set, in particular a new mean speed is set in dependence of the measured response. The invention furthermore relates to a device performing the method.