PMC5587929_01
Note the high-frequency, repetitive electromagnetic (EMI) signal, exactly at 120 msec intervals. Underlying sinus rhythm and regular QRS complexes are clearly visible. The device inappropriately labeled the external AC signal as ventricular fibrillation and cardioverted with 30 J. Ab = atrial blanking period during postventricular atrial refractory period (PVARP); AP: atrial paced; AR: atrial refractory; AS: atrial sensed; CD: charge delivered; FS: (ventricular) fibrillation sensed; VP: ventricular paced; VS: ventricular sensed.
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fig1
Intracardiac electrograms revealed a repetitive, high-frequency artifact on the ventricular channel interwoven with regular atrial and ventricular sensing (Figure 1).
ICD histogram showing evidence of AC voltage current with a mean cycle length of 120 millisec requiring an electrical shock with resultant termination. This data lead to the diagnosis of alternating current (AC) interference by the ICD in proximity to the electrical generator, which was interpreted as a ventricular arrhythmia leading to inappropriate shock.
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fig2
Electrophysiologist reviewed the intracardiac recording and noted the signal was repetitive at exactly 120-millisecond intervals (Figure 2), raising high suspicions for alternating current from an external source.