Transient R-wave amplitude attenuation owing to air entrapment during extravascular implantable cardioverter-defibrillator implantation: Delayed reassessment as a potential bail-out strategy

Figures

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  Figure 1. Intraoperative fluoroscopy. A: The top of the cardiac silhouette, xiphisternal junction, and both parasternal borders were visualized using radiopaque tape on the skin surface. Anteroposterior fluoroscopic views show (B) the initial substernal lead position with the ring 1 and ring 2 electrodes highlighted (blue circles), (C) the substernal lead repositioned slightly rightward (red circles), and (D) the final position, where the R-wave amplitude remained below the success criteria despite securing the ring electrodes being near the initial position (blue circles). Ring 2 was located inferior to the level of the xiphisternal junction (white dashed line).

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  Figure 2. Device electrogram on the ring 1–ring 2 electrodes. A: At the initial sensing test, the device electrogram demonstrated an adequate R-wave amplitude on the ring 1–ring 2 vector (1.5–2.5 mV) without P-wave or myopotential oversensing. B: During implantation, the R-wave amplitude declined. C: At the final position, the R-wave amplitude was 0.6 mV despite the ring electrode replacement near the initial position. D: On postoperative day 2, the R-wave amplitude improved to 1.6 mV, meeting the success criteria. E: By postoperative day 7, amplitude further improved to 2.4 mV. F: At 1-month follow-up, the R-wave amplitude was 2.6 mV, with no inappropriate therapies observed.

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  Figure 3. Resolution of air entrapment around the substernal lead. Serial lateral fluoroscopic views show (A) at the initial position, (B) at the end of the index operation, (C) on postoperative day 2, and (D) 1 week after implantation. Entrapped air surrounding the ring 1 and ring 2 electrodes progressively decreased over time and resolved completely by 1 week. Radiolucent areas indicating entrapped air are highlighted with yellow arrows. Computed tomography (E) on postoperative day 2 demonstrated residual entrapped air surrounding the substernal lead, (F) whereas repeat imaging on postoperative day 7 confirmed complete resolution of the air entrapment.