Temperature-Based Cardiac Pacing Rate Control
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Solution Overview
Problem
Current cardiac pacemakers face challenges in accurately adjusting pacing rates based on activity levels, as they may misinterpret motion or fail to detect increases in activity without device vibration, and temperature-based responses are insufficient in adequately responding to changes in activity levels.
Innovation Solution
A cardiac rhythm management system that uses a temperature-based rate response method, involving a temperature sensor to produce relative and moving baseline temperature signals, which are then used to generate proportional, dip, and slope response signals to adjust pacing rates appropriately in response to changes in activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an accelerometer is used to adjust pacing rate, then the pacemaker can detect motion and increase heart rate in response to activity, but the pacemaker may misinterpret motion (such as riding in a car or on a bumpy road) as patient activity and inappropriately increase pacing rate
Solution Approach 1:
The patent combines temperature sensing with accelerometer sensing to create a hybrid system. The temperature sensor provides a physiological marker of activity that is less susceptible to false positives from non-activity related motion. By merging these two sensing modalities, the system can cross-validate activity detection and reduce inappropriate pacing rate adjustments.
Solution Approach 2:
The temperature sensor acts as an intermediary that provides an alternative physiological signal to confirm activity. Rather than relying solely on motion detection, the system uses temperature changes as a mediator to verify that detected motion corresponds to actual patient activity, thereby filtering out false positives.
2Productivity
If an accelerometer is used to adjust pacing rate, then the pacemaker can respond to patient activity, but the pacemaker may fail to detect increases in activity that are not accompanied by device vibration (such as when an individual rides a stationary bike)
Solution Approach 1:
The patent replaces reliance on mechanical vibration detection with thermal sensing. Instead of requiring the device to mechanically vibrate or be directly contacted by the patient, the temperature sensor detects physiological heat changes in the blood, providing a non-contact measurement of activity level that works regardless of device vibration.
Solution Approach 2:
The system changes the measurement parameter from mechanical vibration amplitude to temperature change magnitude. This parameter transformation allows detection of activity through thermal effects rather than mechanical effects, enabling the system to detect stationary bike riding and other activities that do not produce significant device vibration.
3Reliability
If a blood temperature sensor is used to adjust pacing rate, then the pacemaker can respond to core body temperature changes, but the pacemaker does not appropriately and/or sufficiently respond to changes in a person's activity level
Solution Approach 1:
The patent implements dynamic response characteristics by adjusting the pacing rate modification based on the rate of temperature change rather than absolute temperature values. The system responds more strongly to rapid temperature changes (indicating acute activity onset) and modulates the response magnitude based on the dynamic characteristics of the temperature signal, thereby enhancing responsiveness to activity changes.
Solution Approach 2:
The system detects the initial dip in temperature that occurs at the onset of activity and responds proactively by preemptively increasing the pacing rate before the full thermal effect of exercise develops. This preliminary detection and response allows the pacemaker to anticipate activity-related cardiac demands and adjust pacing rate in advance.
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 and proportional increase in pacing rate in response to exercise, effectively addressing the limitations of accelerometer-based systems and improving the responsiveness of temperature-based pacemakers.
Implementation Method 1
sensing a blood temperature signal indicative of a core body temperature of the patient
Data Source
AI summary
Described herein are implantable medical systems, and methods for use therewith, that provide a temperature based rate response for a patient within which the implantable medical system is implanted. Such a method can include sensing a blood temperature signal indicative of a core body temperature of the patient, and producing a relative temperature signal based on the blood temperature signal. The method can further include producing a moving baseline temperature signal based on the relative temperature signal, producing a proportional response signal based on the relative temperature signal and the moving baseline temperature signal, and producing a sensor indicated rate response signal based on the proportional response signal and a base rate. The sensor indicated rate response signal can also be based on a dip response signal and/or a slope response signal. Additionally, a pacing rate is controlled based on the sensor indicated rate response signal.