A wearable cardioverter defibrillator with a low false alarm rate

Figures

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  Figure 1. ASSURE® WCD System (A‐WCD) noise management. The A‐WCD employs three levels of protection to achieve a low false alarm rate due to noise. Level 1 (blue)—minimize noise; Level 2 (red)—detect and remove noise that does occur; and Level 3 (yellow)—allow time for remaining noise to subside before alarming

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  Figure 2. Electrocardiogram (ECG) sensing. (A) Five ECG electrodes are positioned circumferentially around the torso at the level of the subxiphoid process, labelled left front (LF), right front (RF), left back (LB), right back (RB), and right leg drive (RLD). Red arrows represent the four differential ECG vectors derived using RLD as a ground reference. (B) Garment interior depicting five embedded, cushioned ECG electrodes and defibrillation pads (two posterior and one anterior)

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  Figure 3. Matched filter training. The black line shows the filter kernel. The colored lines show detected complexes

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  Figure 4. ASSURE® WCD System (A‐WCD) segment with successful noise filtering. Example electrocardiogram segment from a 43‐year‐old female with dual‐chamber implantable cardioverter defibrillator (ICD) implanted for secondary prevention. ICD interrogation at the final 30‐day follow‐up revealed 3% atrial pacing and 99% ventricular pacing. (A) Signal contains baseline wander that is successfully removed by the algorithm filters. (B) Two channels were disqualified from segment analysis due to poor electrode contact (lead off). (C) This segment was categorized by the algorithm as normal sinus rhythm with a heart rate of 88 bpm and wide R‐wave. The episode was closed without a shock alarm event marker recorded

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  Figure 5. Initial detection and therapy timeline. The ASSURE® WCD System has two independently programmable therapy zones. Initial detection (gray) is the same for each zone (5/6 overlapping 4.8‐s segments of ventricular tachycardia [VT] or ventricular fibrillation [VF]). Confirmation (yellow) is dependent on zone; 2/2 segments for VF and 15/19 segments for VT. VT that is determined to be disorganized will be treated as slow VF requiring 2/2 segments for confirmation. Once VT or VF is confirmed, a shock alarm event marker is recorded, and the shock alarm sequence (red) is initiated. If 4/6 segments during the shock alarm period are VT or VF, a shock will be delivered. Four out of five non‐VT or VF segments will close an episode. After shock delivery, if an additional 3/5 VT or VF segments are detected, another shock will be delivered (up to five consecutive shocks) and the episode closed if 6/12 non‐VT or VF segments are detected. Electrocardiogram episode storage includes 2 min of onset before episode open, through confirmation and shock delivery and 1‐min post conversion. The shock alarm sequence consists of a triple‐sensory indicator: (1) a flashing red light and shock icon on the…