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Electrophysiology Corner
Inappropriate ICD Therapy Due to Electrical Interference: External Alternating Current Leakage
June 2004
ICD treatment has been shown to be more effective than antiarrhythmic drugs in the prevention of sudden cardiac death, due to malignant ventricular arrhythmias.1 Despite recent advances in device technology, inappropriate therapy (antitachycardia pacing or shock) still remains an unsolved problem. Electromagnetic interference is a cause of inappropriate therapy and EGMs stored by the devices usually show a pattern of electrical noise.
Case Report. In a 70-year-old male patient with prior myocardial infarction and an ejection fraction of 25%, an ICD (Medtronic GEM DR 7275, Minneapolis, Minn.) had been implanted due to spontaneous and inducible ventricular tachycardia while receiving amiodarone.
He experienced the first ICD shock without any warning symptoms after switching the bathroom lights on at his vacation home six months later. The interrogation of the episode revealed that electrical noise was recorded in both atrial and ventricular channels before the discharge of the ICD (Figure 1). In the ventricular channel , the mean cycle length of the noise was 120 ms (500 bpm). The VF zone of the device was programmed at a cycle length
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 In conclusion, electromagnetic interference due to external alternating current leakage was the cause of the inappropriate ICD shock in this patient.
1. Zecowitz J, Armstrong P, Mc Alister F. Implantable cardioverter defibrillators in primary and secondary prevention: A systematic review of randomized, controlled trials. Ann Intern Med 2003;138:445–452.
2. Pinski S and Fahy G. The proarrhythmic potential of implantable cardioverter-defibrillator. Circulation 1995;92:1651–1664.
3. Weber M, Boecker D, Block M, et al. Inappropriate ICD therapies: Incidence, causes, risk factors and prevention. In: E. Adonarto (ed). Therapies for cardiac arrhythmias in 1996: Where are we going? Vol. I, Roma, Italy, Edizioni Luigi Pozzi,1996, pp183–194.
4. Grim W, Flores B, Marchilinski F. Electrocardiographically documented unnecessary, spontaneous shocks in 241 patients with implantable cardioverter-defibrillators. PACE 1992;15:1667–1673.
5. Mathew P, Lewis C, Neglia J, et al. Interaction between electronic article surveillance systems and implantable defibrillators: Insights from a fourth generation ICD. PACE 1997;20:2857–2859.
6. Madrid A, Sanchez A, Bosch E, et al. Dysfunction of implantable defibrillators caused by slot machines. PACE 1997;20:212–214.
7. Manolis AG, Katsivas AG, Vassilopoulos CV, Louvros NE. Implantable cardioverter defibrillator-an unusual case of inappropriate discharge during showering. J Interven Cardiol Electrophysiol 2000;4:265–268.
8. Sabate X, Moure C, Nicolas J, et al. Washing machine associated 50 Hz detected as ventricular fibrillation by an implanted cardioverter defibrillator. PACE 2001;24:1281–1283.
9. Garg A, Wanish M, Brown K, et al. Inappropriate implantable cardioverter defibrillator discharge from sensing of external alternating current leak. J Interv en Cardiol Electrophysiol 2002;7:181–184.
