A novel cause of inappropriate subcutaneous implantable cardioverter-defibrillator therapies after a generator change

Figures

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  Figure 1. Subcutaneous implantable cardioverter-defibrillator electrograms of inappropriate shocks. A: The first inappropriate shock occurred while standing. The device was sensing in the “Alternate” vector with low-amplitude signals and oversensing that had occurred for greater than 15 minutes followed by a brief period of electrical noise artifact before the shock was delivered. B: The second inappropriate shock occurred while supine in the emergency department. The device was sensing in the “Alternate” vector with high-frequency noise that lasted for approximately 20 seconds prior to the shock.

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  Figure 2. Inspection of the subcutaneous implantable cardioverter-defibrillator at the time of device revision. A: Visual inspection of the device suggested that the lead was fully inserted in the header (arrow showing radiolucent marker). B: Cine fluoroscopy of the header suggested the lead was fully inserted in the header (arrow) when compared to panel C. C: Images showing the fluoroscopic appearance of fully (arrow showing radiolucent marker) and incompletely inserted leads (Courtesy of Boston Scientific, with permission).

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  Figure 3. Electrograms recorded during device revision. A: Noise similar to the clinical episodes was easily reproduced with manipulation of the lead within 5 centimeters of the header when sensing in the “Alternate” vector. B–D: After removing the lead from the header, cleaning it, and reinserting it fully, device and lead manipulation in the “Alternate” (B), “Secondary” (C), and “Primary” (D) vectors elicited no electrical noise artifact.