Implantable Device Stroke Volume Measurement via Ballistocardiogram
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Solution Overview
Problem
Current methods for determining stroke volume in implantable medical devices, such as heart pacemakers, face challenges due to high energy consumption, complexity, and reliability issues with thermal dilution, impedance-based methods, and heart sound analysis, which are not directly linked to the heart's pumping capacity.
Innovation Solution
An implantable medical device equipped with a 3-axis acceleration sensor connected to a BCG detection unit that processes acceleration signals to derive a ballistocardiogram (BCG), allowing for direct measurement of stroke volume through the amplitude difference of I and J waves, providing a direct measure of the heart's pumping capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal dilution methods are used to measure stroke volume, then measurement capability is achieved, but energy consumption becomes excessively high and continuous measurement is limited
Solution Approach 1:
The patent replaces thermal dilution methods (requiring temperature pulses and heat measurement) with a mechanical vibration-based approach using an acceleration sensor to detect ballistocardiogram signals. This substitution eliminates the need for thermal energy input and measurement, significantly reducing energy consumption while maintaining stroke volume measurement capability through detection of mechanical vibrations caused by blood ejection.
2Measurement precision
If blood flow measurement sensors are implanted, then continuous stroke volume measurement is possible, but device complexity and energy requirement increase significantly
Solution Approach 1:
The patent makes the acceleration sensor multi-functional by using it for both activity monitoring (existing function) and stroke volume measurement (new function). The same sensor detects both patient movement for activity classification and ballistocardiogram signals for cardiac output measurement, eliminating the need for separate blood flow sensors and reducing overall device complexity.
Solution Approach 2:
The patent utilizes signals that are already present in the system (acceleration signals from normal heart beating) rather than requiring additional dedicated measurement systems. The acceleration sensor naturally captures ballistocardiogram signals as a byproduct of its primary function, allowing the system to extract stroke volume information without adding separate measurement hardware.
3Measurement precision
If impedance-based methods are used to derive stroke volume parameters, then measurement is possible, but reliability decreases due to indirect connection and influence by other factors
Solution Approach 1:
The patent replaces electrical impedance-based indirect measurement with direct mechanical vibration detection. The acceleration sensor directly detects the physical vibrations caused by blood ejection from the left ventricle, providing a direct mechanical link to stroke volume that is not influenced by the indirect electrical conductivity changes and confounding factors affecting impedance methods.
4Measurement precision
If echocardiography is used to determine stroke volume, then accurate geometric measurement is achieved, but cost becomes prohibitive for implantable devices
Solution Approach 1:
The patent replaces expensive echocardiography equipment with a low-cost, miniaturized acceleration sensor that can be implanted. The sensor uses simple piezoelectric or capacitive technology to detect vibrations, eliminating the need for expensive ultrasound transducers, gels, and external imaging equipment, making accurate stroke volume measurement economically viable for implantable devices.
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
Enables efficient and reliable monitoring of the heart's pumping capacity and contractility, allowing for direct monitoring of the heart's pump power and status, with the potential for improved heart failure management and therapy optimization.
Implementation Method 1
The BCG detection unit (74) is connected to the acceleration sensor (72) and is designed to process an acceleration signal originating from the acceleration sensor (72) and to derive a ballistocardiogram (BCG) from the 3D accelerometer output signal
Data Source
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AI summary
Implantable medical device (10) comprises: an integrated or connected implantable acceleration sensor; a ballistocardiogram (BCG) detection unit, which is joined or to be connected to the acceleration sensor, which is designed to process a acceleration signal derived from the acceleration sensor and a ballistocardiogram derived from the acceleration sensor output signal; and BCG evaluation unit associated with the BCG detection unit and designed to evaluate a ballistocardiogram originating from the BCG detection unit. Implantable medical device (10) comprises: an integrated or connected implantable acceleration sensor; a ballistocardiogram (BCG) detection unit, which is joined or to be connected to the acceleration sensor, which is designed to process a acceleration signal derived from the acceleration sensor and a ballistocardiogram derived from the acceleration sensor output signal; and BCG evaluation unit associated with the BCG detection unit and designed to evaluate a ballistocardiogram originating from the BCG detection unit and the BCG evaluation unit provides a stroke volume representing a respective output signal.