Wearable Defibrillator Dynamic Threshold Detection
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Solution Overview
Problem
Current wearable cardioverter defibrillator (WCD) systems face challenges in detecting and responding to tachycardic events, as heart rates during deteriorating heart conditions may decrease, potentially inhibiting timely detection and intervention.
Innovation Solution
A WCD system configured to dynamically adjust its decision threshold for administering shocks based on extracted heart rate values, with temporary lowering of the threshold in response to detected arrhythmias and intermediate shocks, to enhance detection of tachycardic events and prevent false negatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed decision threshold is used for shock administration, then the system maintains simplicity in operation, but detection reliability deteriorates when heart rate decreases during tachycardic events
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a fixed decision threshold to a dynamic, variable threshold that automatically adjusts based on detected heart rate values. When a tachycardic event is detected (heart rate exceeding the threshold), the system dynamically lowers the threshold for subsequent measurements, ensuring continued detection capability even as heart rate decreases during the event. This dynamic adaptation resolves the contradiction by maintaining detection reliability without requiring complex manual intervention.
Solution Approach 2:
The patent implements feedback by using the detected heart rate values to continuously adjust the decision threshold. The system monitors heart rate, compares it to the threshold, and based on whether the threshold is exceeded, automatically modifies the threshold level for subsequent detections. This closed-loop feedback mechanism ensures the system adapts to changing cardiac conditions, maintaining high detection reliability while operating autonomously without complex user intervention.
2Reliability
If the decision threshold is lowered to improve detection sensitivity, then false positives increase, but detection precision deteriorates
Solution Approach 1:
The patent applies dynamics by implementing a threshold that changes state based on detected events. The threshold remains at a higher level during normal conditions to maintain precision, but dynamically lowers only after a tachycardic event is confirmed, allowing sustained detection sensitivity during the event while avoiding premature false positives. This temporal dynamics resolves the contradiction between sensitivity and precision.
Solution Approach 2:
The patent applies preliminary action by requiring the heart rate to first exceed the initial threshold before the threshold lowering takes effect. This preliminary detection step ensures that the threshold is only lowered when a genuine tachycardic event has been identified, preventing false positives from triggering premature threshold reduction. This sequential approach maintains detection precision while enabling subsequent sensitivity during confirmed events.
Data Source
AI summary
A wearable cardioverter defibrillator (WCD) system according to embodiments is configured to be worn by an ambulatory patient, and to sense ECG signals of the patient. The WCD system includes a processor that extracts heart rate values from the ECG signals. If a heart rate value exceeds a decision threshold then, for subsequent heart rate values, the decision threshold may be lowered for administering a certain shock to the patient. In some embodiments the lowering is due to a cancel input being received, an intermediate shock having been administered, and so on. In some embodiments the decision threshold is lowered only temporarily. This may help with detecting a tachycardic event, and in particular with preventing the inhibiting of detecting such an event, as the patient's heart rate during such events may decrease while the heart's condition is deteriorating.