Inappropriate ICD Therapy Due to Electrical Interference: External Alternating Current Leakage

Case Report

In a 70-year-old male with prior myocardial infarction and an ejection fraction of 25%, an ICD (Medtronic GEM DR 7275, Minneapolis, Minnesota) had been implanted due to spontaneous and inducible ventricular tachycardia while receiving amiodarone. In the ventricular channel, the mean cycle length of the noise was 120 ms (500 bpm). 

Discussion

Inappropriate ICD shock in a conscious patient, apart from being painful, can also cause proarrhythmia.² Inappropriate therapy occurs in 18-24% of patients with ICDs.³ Weber et al reported 39% of inappropriate therapy due to atrial fibrillation, 30% to sinus tachycardia, and 21% to ventricular oversensing.³ Potential causes of ventricular oversensing are ventricular lead fracture or isolation defect, sensing of T-wave (double counting), sensing of P-wave in atrial flutter or tachycardia (farfield sensing), myopotentials, insufficient contact of the ventricular lead with myocardium and to electromagnetic interference.⁴ Cases of electromagnetic interference have been previously described, caused by electronic anti-theft surveillance devices, slot machines, electrical razors, during showering or touching a washing machine and external alternating current leakage, as in our case.^5-9

Conclusion

In conclusion, electromagnetic interference due to external alternating current leakage was the cause of the inappropriate ICD shock in this patient.