Heart Sound Template Matching for Bi-Ventricular Pacing Capture
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Solution Overview
Problem
Current ambulatory medical devices inaccurately estimate the effectiveness of bi-ventricular pacing therapy due to limitations in monitoring cardiac capture, especially during episodes of atrial fibrillation and the occurrence of fusion beats, which can lead to inaccurate counting of effective pacing pulses.
Innovation Solution
The implementation of a system that includes an implantable therapy circuit for bi-ventricular pacing, a heart sound signal sensing circuit to detect mechanical cardiac activity, and a comparison circuit to match sensed heart sound signals with pre-stored templates to determine the effectiveness of pacing therapy by identifying ventricles where capture was induced, providing a more accurate assessment of cardiac capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical pacing stimulation is delivered to induce cardiac depolarization, then cardiac capture is achieved, but accurate determination of pacing effectiveness becomes difficult during atrial fibrillation and fusion beats
Solution Approach 1:
The patent replaces electrical signal-based capture detection with mechanical heart sound detection. Instead of relying on electrical signals that become unreliable during atrial fibrillation and fusion beats, the system uses acoustic sensors to detect mechanical heart sounds, providing a more reliable indicator of true cardiac capture.
Solution Approach 2:
The patent introduces heart sound signals as an intermediary indicator to indirectly assess cardiac capture. Rather than directly measuring electrical capture which is ambiguous during atrial fibrillation, the system uses heart sounds as a mediator that reliably indicates whether pacing successfully induced mechanical contraction.
2Measurement precision
If heart sound signal sensing is implemented to detect mechanical cardiac activity, then capture determination accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the sensing circuit multi-functional by enabling it to detect both electrical cardiac signals and mechanical heart sounds using the same hardware infrastructure. This allows the device to switch between detection modes or combine both signals for enhanced capture determination without requiring entirely separate sensing systems.
Solution Approach 2:
The device uses its own existing sensing capabilities and processing resources to analyze heart sound signals for capture detection. The implantable device leverages its built-in computational resources to perform template matching and signal analysis, eliminating the need for external monitoring equipment.
3Reliability
If template comparison is used to identify ventricles with induced cardiac capture, then pacing therapy efficacy is accurately determined, but processing time and computational requirements increase
Solution Approach 1:
The patent performs preliminary actions by pre-storing heart sound templates representing different pacing scenarios (e.g., right ventricular capture, left ventricular capture, biventricular capture) before actual pacing therapy. During pacing, the system simply compares incoming signals against these pre-established templates, significantly reducing real-time processing requirements while maintaining high accuracy.
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
This approach provides a more accurate determination of the efficacy of cardiac pacing therapy by using heart sound signals to confirm capture, allowing for improved monitoring and optimization of pacing parameters, such as AV delay and stimulation amplitudes, thereby enhancing the effectiveness of the therapy.
Implementation Method 1
a heart sound signal sensing circuit to detect mechanical cardiac activity
Data Source
AI summary
An apparatus may include an implantable therapy circuit that provides bi-ventricular pacing to a subject, a heart sound signal sensing circuit that produces a sensed heart sound signal that is representative of at least one heart sound associated with mechanical cardiac activity, a memory circuit to store one or more heart sound templates of cardiac capture, and a comparison circuit that compares a segment of the sensed heart sound signal to the one or more heart sound templates of cardiac capture to identify ventricles in which cardiac capture was induced by the bi-ventricular pacing. In some situations, an indication of the ventricles in which cardiac capture was induced may be generated according to the comparison.