Paced Depolarization Integral Tracking for Hypoglycemia Detection
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Solution Overview
Problem
Current techniques for detecting hypoglycemia in diabetic patients using implantable medical devices, such as pacemakers and ICDs, are inadequate, especially during paced beats and for predicting episodes of hypoglycemia, as they rely on ineffective methods that do not account for cardiac abnormalities and require surface electrodes.
Innovation Solution
The implementation of a system that tracks changes in the paced depolarization integral (PDI) of electrical cardiac signals to detect hypoglycemia, allowing for the generation of warning signals and automatic therapy adjustments, including insulin delivery suspension and defibrillation capacitor charging, without the need for surface electrodes, and predicts episodes based on trend analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If QT interval monitoring is used to detect hypoglycemia, then detection capability is improved, but the method requires surface electrodes and is ineffective during paced beats
Solution Approach 1:
The patent changes the detection parameter from QT interval to PDI (paced depolarization integral). The PDI is calculated by integrating the absolute value of the ventricular evoked response signal during the depolarization phase, providing a different electrical parameter that remains effective during paced beats where QT interval measurement fails.
Solution Approach 2:
The patent replaces the surface electrode-based ECG system with an implantable device that uses intracardiac electrograms. This substitution eliminates the need for surface electrodes and enables continuous monitoring, including during paced beats, by utilizing electrodes already present within the heart.
2Reliability
If implantable devices are used for continuous monitoring, then detection reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes the implantable device multi-functional by integrating both cardiac pacing/defibrillation functions and hypoglycemia detection functions into a single device. The same intracardiac electrodes used for cardiac therapy are also used for hypoglycemia detection, eliminating the need for separate sensors and reducing overall system complexity.
Solution Approach 2:
The device uses its own existing resources (intracardiac electrodes and processed electrical signals) for dual purposes: cardiac therapy delivery and hypoglycemia detection. The ventricular evoked responses, normally byproducts of pacing, are repurposed as the detection signal for hypoglycemia, making the system self-sufficient.
3Measurement precision
If PDI tracking is implemented, then hypoglycemia detection accuracy is improved, but computational requirements increase
Solution Approach 1:
The patent calculates PDI only during the ventricular depolarization phase (from pacing stimulus to peak of evoked response) rather than analyzing the entire cardiac cycle. This partial action approach focuses computational resources on the most informative portion of the signal where hypoglycemia-induced changes occur, reducing overall computational burden.
Solution Approach 2:
The device continuously tracks and stores PDI values over time, building up a historical database of depolarization integrals. This preliminary accumulation of data allows the system to detect hypoglycemia through trend analysis and threshold comparisons without requiring complex real-time calculations, as the computational work is distributed over time.
Data Source
AI summary
Techniques are provided for use with an implantable medical device such as a pacemaker or implantable cardioverter/defibrillator (ICD) for predicting and detecting hypoglycemia. In one example, the device tracks changes in a paced depolarization integral (PDI). A significant increase in PDI over a relatively short period of time indicates the onset of hypoglycemia (this can also be confirmed with QT changes). Upon detection of hypoglycemia, appropriate warning signals are generated to alert the patient. Certain therapies automatically provided by the implantable device may also be controlled in response to hypoglycemia. For example, if the patient is an insulin-dependent diabetic and the implantable device is equipped with an insulin pump capable of delivering insulin directly into the bloodstream, insulin delivery is automatically suspended until blood glucose levels return to acceptable levels. If the device is an ICD, it may be controlled to begin charging defibrillation capacitors upon detection of hypoglycemia so as to permit prompt delivery of a defibrillation shock, which may be needed if hypoglycemia triggers ventricular fibrillation. The detection techniques may be used in conjunction with other hypoglycemia detection techniques to improve detection specificity.