Inappropriate shock delivery by implantable cardioverter defibrillator due to electrical leak from bathroom tap

Abstract

There are some case reports of electromagnetic interference (EMI) mimicking cardiac arrhythmias and causing inappropriate implantable cardioverter defibrillator (ICD) shocks. EMI can arise from appliances, such as slot machines, electric razors, hand held radiofrequency remote controls or abdominal muscle stimulator units, but it can also arise from alternating current leak from, for example, a washing machine, swimming pool, etc. [1–8]. Such interference is recognized easily in the stored intracardiac electrograms of ICDs because of the typical pattern of electrical noise. Here, we report a case who experienced inappropriate ICD shock, resulting from the ICD sensing alternating current (AC) from an unexpected external source (a bathroom tap). The patient is a 77-year-old male with depressed left ventricular function, who suffered from recurrent symptomatic ventricular tachycardia (VT). Electrocardiography documented monomorphic VT and cardiac electrophysiological study revealed inducible sustained monomorphic VT. A single chamber ICD (Maximo VR 7232, Medtronic Inc., Minneapolis, MN, USA) was implanted. The ICD lead was a Sprint Quattro RV/SVC model 6944 (Medtronic Inc., Minneapolis, MN, USA) with true bipolar sensing. He had five episodes of VT terminated by antitachycardia pacing or low energy cardioversion in January 2009. After hospitalization and intravenous amiodarone therapy, he had no further recurrence of ventricular arrhythmias. He experienced an ICD shock in January 2010. Device interrogation revealed typical EMI consistent with 50-Hz alternating current on the ventricular channel. A 15-J shock was delivered. Sensitivity was programmed to 0.3 mV. Pacing lead impedance was 816 X and shocking lead impedance was 53 X. There was no evidence of ICD system malfunction. He was preparing to wash his hands in the bathroom and touched the tap with his wet left hand shortly before the inappropriate shock. He felt the shock and then remained asymptomatic. Review of the intracardiac EGM (Fig. 1) reveals the onset of high-frequency noise detected by the ICD as VF, superimposed on normal R-waves marching through the noise. The tap of the bathroom was inspected by a licensed electrician and a small amount of current leak was detected. The electrician found that the leak originated from inappropriately earthed bathroom socket which was attached to the water pipe for grounding. The socket was regrounded properly and the patient was advised again about electrical appliances. This case is a typical example of potential environmental hazards to patients who have ICDs, particularly when electrical appliances and instruments are not sufficiently earthed. When household appliances are earthed improperly, the potential for electrical leak is the result. Detailed advice on handling electrical appliances by ICD recipients is of utmost importance. In patients who experience ICD shocks because of electrical leak, the history and examination of stored intracardiac electrograms are typical. The high-frequency noise of the leak was easily detected by the ICD. Because household appliances are not earthed in some rural parts of Turkey, the potential for electrical leak is very high like our patient. The noise on the stored intracardiac electrogram is typical of this type of EMI. It is recommended that checking for electrical leaks and grounding should be A. Camsari (&) D. C. Yilmaz T. Ozcan Department of Cardiology, Mersin University Medical Faculty, Mersin, Turkey e-mail: ahmetcamsari@yahoo.com