Images in Cardiology

A 75 year-old man with a Biotronik Lumax VR-T540 uncommitted implantable cardioverter-defibrillator (ICD) received a shock during general anesthesia for the resection of a basal cell carcinoma on the nose. The surgeon who was unaware of the ICD, used unipolar electrocautery during the procedure. No ICD parameters were reprogrammed preoperatively and the device remained programmed as follows: Low rate = 40 ppm, ventricular tachycardia — 1, rate = 167–222 bpm, antitachycardia pacing (ATP) followed by 40 J shocks, ventricular fibrillation (VF) zone 12/16 and > 222 bpm, ATP, followed by 40 J shocks. ATP in this device is only activated by tachycardia with relatively stable cycle lengths which was not the case in our patient because the interference from electrocautery produced sensed signals with marked irregularity of rate or detected intervals. Figure 1 shows how interference from electrocautery was detected as VF by the device which then initiated capacitor charging. ATP was not delivered. The capacitor charge was then aborted when the interference abated based on the uncommitted function of the ICD (Fig. 2). The subsequent recurrence of another bout of interference failed to produce enough “sinus” intervals between the aborted shock and VF redetection (interference) to fulfill detection of a normal termination (Fig. 2). Instead the ICD redetected or reconfirmed the presence of a continuing tachyarrhythmia. The ICD again began to charge its capacitor