Changing place, changing future: Repositioning a subcutaneous implantable cardioverter-defibrillator can resolve inappropriate shocks secondary to myopotential oversensing

Figures

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  Figure 1. A: Lateral chest radiograph after subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation. B: Electrogram of S-ICD shocks. Noise from myopotential signals (red arrows) with a similar amplitude to that of QRS complexes at a heart rate of ∼90 beats/min (green arrows) leads to the incorrect detection of tachycardia (asterisk) and an inappropriate shock (single circle) that triggers ventricular fibrillation (star), which is appropriately sensed and treated by means of a second S-ICD shock (double circle).

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  Figure 2. Device interrogation before system repositioning. The primary vector (1× gain) showed less oversensing but an unstable R-wave amplitude owing to postural movements (intermittently <1 mV). Maneuvers resembling the exercise that caused the inappropriate shock lead to intermittent oversensing (asterisks). Small R-wave amplitudes were also observed in alternate and secondary vectors.

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  Figure 3. A: Lateral chest radiograph after system repositioning (can relocation only). B: Device interrogation repeating the maneuvers in the primary vector (gain setting 2×) did not show oversensing; R-wave amplitude remained constantly >1 mV even with postural changes; and there was better 1:1 beat classification (a premature ventricular contraction was also correctly discarded; see the “•” marker).