A Case of VF Misclassification Corrected by VF Therapy Assurance: Implications for ICD Programming

Figures

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  FIGURE 1. (A) Electrogram of atrial fibrillation (AF). The VS markers within the dotted line indicate 4 beats (A‐(1) and A‐(2)), which do not fulfill the criteria for tachycardia episode termination. (B) Anti‐tachycardia pacing (ATP) therapy was delivered due to misclassification of AF as ventricular fibrillation (B‐(3)). AR, Accelerated Rhythm; ATP, anti‐tachycardia pacing; F, ventricular interval within ventricular fibrillation zone; R, reconfirmed interval; STIM, stimulus of anti‐tachycardia pacing; T, ventricular interval within ventricular tachycardia zone; VS, Ventricular Sensed event; VS2, low‐amplitude R‐wave signal detected by the coil‐to‐can sensing channel (discrimination channel).

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  FIGURE 2. (A) A shock was delivered to treat ventricular fibrillation (VF); however, VF was not terminated successfully. Subsequently, undersensing occurred, resulting in the detection of only 3 consecutive VS markers, causing the episode to be incorrectly classified as terminated (A‐(1)). Shortly thereafter, 2 consecutive VS2 markers were detected in the discrimination channel, triggering ventricular fibrillation therapy assurance (VFTA) (A‐(2)). After VFTA activation, 6 F markers were detected, confirming VF (A‐(3) and B). (B) Charging was initiated to prepare for shock delivery. (C) The shock therapy successfully restored sinus rhythm. HV, high‐voltage shock therapy; VVI, ventricular pacing, ventricular sensing, inhibited response; other abbreviations are as defined above.

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  FIGURE 3. (A–E) Simulated electrogram illustrating the scenario in which ventricular fibrillation therapy assurance (VFTA) was turned off. Markers were recalculated using the binning method, incorporating Interval Average (IA) and Current Interval (CI). (A and B) Ventricular fibrillation (VF) persisted even after shock therapy. If the VFTA had been off, the VS markers (within the dotted line) would have reached 5, meeting the tachycardia episode termination criteria. (C–E) By the time the second shock was delivered with the VFTA function on, only 6 F markers had been detected in this simulation, which likely failed to meet the NID30 requirement, resulting in failure to detect VF. IA (Mean of CI and the preceding three beats) is displayed in the upper row. CI (Mean of the preceding two beats) is displayed in the lower row. CI, Current Interval; IA, Interval Average; Other abbreviations are as defined above.