Ventricular Assist Device Speed Control Algorithm for Aortic Valve Biomechanics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ventricular assist devices (VADs) cause altered aortic valve biomechanics, leading to complications like aortic insufficiency, stenosis, and thrombus formation due to continuous ventricular unloading, which existing approaches fail to address effectively, especially in long-term support, as they rely on minimal pump speeds that do not account for individual patient needs.
Innovation Solution
A control circuit for a continuous-flow VAD that operates in cycles, adjusting pump speed and flow rate to mimic natural heart function by reducing speed from a first to a second rate during a ramp-down period, maintaining the second rate for a period, and then increasing back to the first rate, ensuring periodic aortic valve opening and maintaining net positive antegrade flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the VAD operates at minimal pump speeds to aid aortic valve opening, then the aortic valve can open periodically, but perfusion is minimized and it does not account for specific patient requirements
Solution Approach 1:
The patent applies dynamics by transitioning from static minimal speed operation to dynamic cyclic speed variation. The control circuit implements alternating high and low speed periods, allowing the system to adapt between maximizing perfusion (high speed) and enabling valve opening (low speed), resolving the contradiction between these two competing requirements.
Solution Approach 2:
The patent implements periodic action through cyclic alternation between high speed mode (for adequate perfusion) and low speed mode (for aortic valve opening). This periodic switching allows both high perfusion and valve opening to occur at different times within each cycle, eliminating the need to choose one over the other permanently.
2Productivity
If the VAD operates continuously at high speed to maintain adequate perfusion, then perfusion is maintained, but the aortic valve remains closed leading to altered biomechanics and complications
Solution Approach 1:
The patent uses periodic action by implementing cyclic alternation between high speed operation (maintaining perfusion) and low speed operation (allowing valve opening). This ensures that the aortic valve opens periodically to maintain proper biomechanics while the high speed periods maintain adequate perfusion, resolving the contradiction between these two requirements.
Solution Approach 2:
The system transitions from static high-speed operation to dynamic cyclic speed variation. The control circuit manages transitions between high and low speed modes, allowing the system to adaptively balance perfusion requirements with valve function requirements, preventing complications while maintaining adequate blood flow.
3Reliability
If the pump speed is reduced to allow aortic valve opening, then valve opening is achieved, but flow rate decreases
Solution Approach 1:
The patent resolves this contradiction by implementing periodic alternation between high speed mode (maintaining high flow rate for perfusion) and low speed mode (allowing valve opening). The cyclic nature ensures that flow rate is maintained at high levels during portions of the cycle while valve opening occurs during low speed portions, achieving both goals over time rather than sacrificing flow rate permanently.
Data Source
AI summary
A ventricular assist device (“VAD”) includes a continuous-flow pump (2) implantable in fluid communication with a ventricle (V) and an artery (A) of a patient to assist blood flow from the ventricle to the artery. The VAD also includes a control circuit (12) connected to the pump, the control circuit being configured to direct the pump to operate in a series of cycles. Each cycle may include (i) pumping blood at a first speed (RPM1) and at a first flow rate during a first period (t1); then (ii) decreasing the speed of the pump from the first speed to a second speed (RPM2) during a ramp-down period (tRD); then (iii) pumping blood at the second speed and at a second flow rate during a second period (t2); and then (iv) increasing the speed of the pump from the second speed to the first speed during a ramp-up period (tRU).