Pacing Safety Margin Calculation for Cardiac Capture Reliability
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Solution Overview
Problem
Existing implantable medical devices (IMDs) face challenges in optimizing pacing stimulation energy to ensure effective heart therapy while minimizing stress on the heart and conserving battery life, as current methods either deliver excessive energy or insufficient energy, leading to inefficient capture of cardiac depolarization.
Innovation Solution
The system includes a cardiac signal sensing circuit, a therapy circuit, and a controller circuit that detects cardiac capture by adjusting pacing stimulation energy levels and calculates a safety margin using evoked response parameters, ensuring optimal energy delivery by identifying the minimum energy required for consistent capture and incorporating a safety margin to prevent loss of capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pacing stimulation energy is increased to ensure effective heart therapy, then capture reliability is improved, but heart stress increases and battery life decreases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pacing stimulation energy level based on measured evoked response parameters. The system modifies the stimulation energy parameter in response to real-time measurements of evoked response amplitude and morphology, transitioning from fixed energy delivery to adaptive energy adjustment. This resolves the contradiction by finding the minimum energy level that maintains reliable capture while reducing excessive heart stress.
Solution Approach 2:
The patent implements feedback by measuring evoked response parameters following each pacing stimulus and using these measurements to adjust subsequent stimulation energy levels. The system creates a closed-loop control where the evoked response serves as feedback signal, allowing the device to optimize pacing energy delivery. This feedback mechanism enables maintaining capture reliability while minimizing heart stress by delivering only the necessary energy.
2Reliability
If pacing stimulation energy is increased to ensure effective heart therapy, then capture reliability is improved, but battery life is reduced
Solution Approach 1:
The patent changes the stimulation energy parameter dynamically based on measured evoked response characteristics. By adjusting the energy parameter in response to real-time measurements, the system delivers minimum necessary energy rather than excessive fixed energy, thereby extending battery life while maintaining capture reliability.
Solution Approach 2:
The feedback mechanism measures evoked response parameters and uses this information to optimize pacing energy delivery. This closed-loop control prevents wasteful energy consumption by delivering only the minimum energy required for reliable capture, directly extending battery life while maintaining therapeutic effectiveness.
3Object-affected harmful factors
If pacing stimulation energy is reduced to minimize heart stress, then heart stress is reduced, but capture reliability deteriorates
Solution Approach 1:
The system dynamically adjusts the stimulation energy parameter based on measured evoked response parameters. By continuously monitoring the evoked response and adapting the energy level, the system maintains reliable capture at lower energy levels than fixed high-energy pacing, thereby reducing heart stress while preserving capture reliability.
Solution Approach 2:
The patent transitions from static fixed-energy pacing to dynamic adaptive pacing where the stimulation energy varies in response to real-time physiological feedback. This dynamic adjustment allows the system to optimize the balance between capture reliability and heart stress reduction, delivering energy levels matched to the patient's instantaneous cardiac excitability.
4Duration of action of stationary object
If pacing stimulation energy is reduced to extend battery life, then battery life is extended, but capture reliability deteriorates
Solution Approach 1:
The patent dynamically changes the stimulation energy parameter based on measured evoked response characteristics. This adaptive parameter adjustment enables the system to extend battery life by reducing unnecessary energy delivery while maintaining capture reliability through real-time optimization based on physiological feedback.
Solution Approach 2:
The feedback mechanism enables the system to extend battery life by using evoked response measurements to optimize energy delivery. The closed-loop control ensures that energy is reduced only when physiological conditions permit, maintaining capture reliability while minimizing energy consumption for extended battery operation.
Data Source
AI summary
An apparatus comprises a cardiac signal sensing circuit, a pacing therapy circuit, and a controller circuit. The controller circuit includes a safety margin calculation circuit. The controller circuit initiates delivery of pacing stimulation energy to the heart using a first energy level, changes the energy level by at least one of: a) increasing the energy from the first energy level until detecting that the pacing stimulation energy induces stable capture, or b) reducing the energy from the first energy level until detecting that the stimulation energy fails to induce capture, and continues changing the stimulation energy level until confirming stable capture or the failure of capture. The safety margin calculation circuit calculates a safety margin of pacing stimulation energy using at least one of a determined stability of a parameter associated with evoked response and a determined range of energy levels corresponding to stable capture or intermittent failure of capture.