Defibrillator Shock Timing Using R-Wave and T-Wave Classification
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Solution Overview
Problem
Inappropriate defibrillation shocks, particularly during T-waves, can lead to pro-arrhythmia and reduce battery capacity, necessitating mitigation strategies to improve synchronization of defibrillation shocks.
Innovation Solution
A method and device for defibrillators that characterize cardiac electrical events as either R-waves or T-waves, adjusting shock delivery protocols based on this characterization to avoid delivering shocks during T-waves, including delay mechanisms and amplitude/interval analysis to differentiate between the two.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the defibrillator issues a synchronized therapy after detecting a cardiac cycle, then the shock delivery is timed to the cardiac rhythm, but the shock may be delivered during the T-wave causing pro-arrhythmia
Solution Approach 1:
The patent applies preliminary action by implementing a post-detection time interval (PDTI) that delays shock delivery until after the T-wave has passed. The system detects the R-wave, then waits for a predetermined interval before delivering the shock, ensuring the shock does not occur during the vulnerable T-wave period. This preliminary timing adjustment prevents pro-arrhythmia while maintaining synchronized shock delivery.
2Measurement precision
If the defibrillator detects both R-waves and T-waves as cardiac events, then the cardiac rate calculation may be twice the actual rate, but this leads to inappropriate shock delivery
Solution Approach 1:
The patent extracts and removes T-waves from the set of detectable cardiac events that trigger shock delivery. By implementing waveform characterization that identifies T-waves separately from R-waves, the system excludes T-waves from initiating the shock delivery sequence. This extraction prevents double-counting of cardiac events and ensures shocks are only delivered in response to appropriate R-wave detections.
3Use of energy by moving object
If the defibrillator delivers inappropriate shocks during T-waves, then battery capacity is reduced, but patient safety is compromised
Solution Approach 1:
The patent implements feedback by continuously monitoring the cardiac rhythm and waveform characteristics to determine the appropriate timing for shock delivery. The system uses real-time analysis of the ECG waveform to identify R-waves versus T-waves, and adjusts the shock delivery timing based on this feedback. This closed-loop control ensures shocks are delivered only at appropriate times, conserving battery capacity while preventing patient harm from inappropriate shocks.
Data Source
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AI summary
Wearable, automatic external, and implantable defibrillators, as well as methods of operation in such systems, are disclosed with shock delivery mitigations to avoid delivering a defibrillation shock on a T-wave. Prior to issuance of a defibrillation shock, one or more detected cardiac events are analyzed to characterize a detected event that is sensed for purposes of synchronizing the defibrillation shock. The detected event can be characterized as an R-wave or a T-wave, and the shock delivery protocol is then selected based on the characterization of the detected event to avoid shock-on-T and potential pro-arrhythmia.