Hybrid Autothreshold Pacing Control for Implantable Cardiac Devices
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Solution Overview
Problem
Implantable medical devices (IMDs) face challenges in optimizing pacing stimulation energy for the heart, as excessive energy can cause stress and shorten battery life, while insufficient energy may fail to induce cardiac capture, and existing threshold test methods are inadequate when an independent sensing electrode is unavailable.
Innovation Solution
The system includes a therapy circuit for cardiac electrostimulation, a cardiac signal sensing circuit, and a control circuit that initiates normal pacing mode and selects between first and second threshold test modes based on electrode availability, using either shared or independent sensing electrodes to determine the optimum pacing energy for heart capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher pacing stimulation energy is delivered to ensure therapy delivery and cardiac capture, then reliability of capture is improved, but battery life is shortened and heart stress increases
Solution Approach 1:
The system dynamically changes the pacing stimulation energy parameter based on detected cardiac capture status. By delivering test pulses at varying energy levels and detecting whether capture occurs, the system identifies the minimum effective energy threshold and adjusts pacing parameters accordingly, ensuring reliable capture while minimizing energy consumption and preserving battery life.
2Loss of energy
If pacing stimulation energy is reduced to conserve battery life, then energy consumption is decreased, but cardiac capture may fail to occur
Solution Approach 1:
The system employs feedback mechanisms where cardiac activity signals are continuously monitored to detect whether pacing stimulation successfully induced cardiac capture. This feedback information is used to adjust subsequent pacing energy levels, allowing the system to conserve energy by reducing stimulation when capture is achieved while increasing energy when capture fails, thus maintaining reliability while optimizing energy conservation.
3Measurement precision
If a sensing electrode independent from pacing electrodes is used for threshold testing, then measurement precision of capture detection is improved, but device complexity increases
Solution Approach 1:
The system implements multi-functionality by enabling pacing electrodes to serve dual purposes: delivering pacing stimulation and sensing cardiac activity for capture detection. This allows the same electrode to function as both a stimulator and a sensor, eliminating the need for separate independent sensing electrodes during threshold testing, thereby maintaining measurement precision while reducing device complexity.
Solution Approach 2:
The pacing electrodes perform self-service by simultaneously executing their primary function of delivering stimulation and their secondary function of sensing cardiac responses. The electrode that delivers the pacing pulse also detects the resulting cardiac depolarization, allowing the system to determine capture status without requiring additional dedicated sensing electrodes, thus simplifying the overall device architecture.
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 allows for accurate determination of the minimum electrostimulation energy required for cardiac capture, optimizing therapy delivery while conserving battery life and ensuring reliable capture detection even when an independent sensing electrode is not available.
Implementation Method 1
provide cardiac electrostimulation energy to a heart chamber of a subject using a set of implantable pacing electrodes
Implementation Method 2
a cardiac signal sensing circuit configured to sense a cardiac activity signal
Data Source
AI summary
An apparatus comprises a control circuit that initiates a normal pacing mode for delivery of electrostimulation energy to the heart chamber. In response to an indication to initiate a threshold test, the control circuit determines an electrode configuration used to deliver the electrostimulation energy in the normal pacing mode, selects a first threshold test mode when a sensing electrode independent from the set of pacing electrodes is unavailable for the heart chamber, wherein a cardiac activity signal is sensed using a set of sensing electrodes that includes an electrode common to the set of pacing electrodes, and selects a second threshold test mode when a sensing electrode independent from the set of pacing electrodes is available for the heart chamber, wherein the cardiac activity signal is sensed using a set of sensing electrodes that excludes an electrode common to the set of pacing electrodes.