Cardiac Pump Speed Modulation for Ventricular Unloading
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Solution Overview
Problem
Existing ventricular assist devices struggle to effectively unload a weakened ventricle during the systolic phase, leading to increased ventricular resistance and suction risks due to flow inertia and inappropriate pump speed control.
Innovation Solution
A ventricular assist device with a motor controller that adjusts impeller speed variably throughout the cardiac cycle, ramping up during diastole to reduce ventricular load and ramping down during systole to prevent collapse, using a combination of variable speed and constant current modes to adapt to the patient's physiological state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump speed is increased to maximize ventricular unloading, then the pump flow is increased, but the ventricle contraction remains isometric at the beginning of systole due to flow inertia
Solution Approach 1:
The pump speed is increased before the systolic phase begins, during the late diastolic phase. This preliminary action allows the pump to capture blood and reduce ventricular pressure before contraction starts, eliminating the isometric contraction problem while maintaining high pump flow during systole.
2Productivity
If the pump speed is increased to maximize ventricular unloading, then the pump flow is increased, but the risk of ventricular suction increases at the end of systole
Solution Approach 1:
The pump speed is varied periodically in sync with the cardiac cycle: increased during diastole to unload the ventricle, then decreased during systole to prevent suction. This periodic modulation of pump speed allows the system to achieve maximum unloading while avoiding the harmful effect of ventricular suction at the end of systole.
3Ease of operation
If the pump speed is varied within the cardiac cycle to mimic natural heart action, then the pump speed is increased during systole and decreased during diastole, but the ventricle unloading is reduced
Solution Approach 1:
The pump speed control is inverted from conventional pulsatile pumping. Instead of increasing speed during systole and decreasing during diastole, the system increases speed during diastole and decreases speed during systole. This inversion enables maximum ventricular unloading while maintaining physiologic responsiveness through synchronization with the cardiac cycle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device enhances ventricular contraction by reducing resistance and preventing suction, providing effective unloading and a more natural physiologic response as the patient recovers.
Implementation Method 1
A ventricular assist device with a motor controller that adjusts impeller speed variably throughout the cardiac cycle, ramping up during diastole to reduce ventricular load and ramping down during systole to prevent collapse
Implementation Method 2
a centrifugal pump with a magnetically levitated impeller to pump blood from the left ventricle to the aorta
Implementation Method 3
a centrifugal pump with a magnetically levitated impeller to pump blood from the left ventricle to the aorta
Implementation Method 4
The impeller can act as a rotor of an electric motor in which a rotating magnetic field from a multiphase stator couples with the impeller and is rotated at a speed appropriate to obtain the desired blood flow through the pump
Data Source
AI summary
A blood pump system is implantable in a patient for ventricular support. A pumping chamber has an inlet for receiving blood from a ventricle of the patient. An impeller is received in the pumping chamber. A motor is coupled to the impeller for driving rotation of the impeller. A motor controller is provided for tracking systolic and diastolic phases of a cardiac cycle of the patient and supplying a variable voltage signal to the motor in a variable speed mode to produce a variable impeller speed linked to the cardiac cycle. The impeller speed comprises a ramping up to an elevated speed during the diastolic phase in order to reduce a load on the ventricle at the beginning of the systolic phase.