Leakage current from transvenous and subcutaneous implantable cardioverter defibrillators (ICDs): A risk to the rescuer?

Abstract

Implantable cardioverter-defibrillators (ICDs) are a well-established therapy for patients at risk of life-threatening ventricular arrhythmias. With rising implant rates, the risk of a rescuer performing chest compressions during discharge is increasing, leading to concerns over rescuer safety from the resultant leakage current. More recently, subcutaneous ICDs (S-ICD) have been developed, which utilise a higher energy and more superficial electrodes compared with transvenous ICDs (T-ICD), raising safety concerns further. We measured the current a rescuer would potentially receive from T-ICDs and S-ICDs if they were in contact with the patient at the time of ICD discharge to assess its magnitude in relation to international safety standards. Surface voltages adjacent to ICD electrodes were measured on patients undergoing defibrillation threshold checks. Rescuer current was then calculated assuming a total rescuer circuit impedance of 1696 Ω. Twenty-five patients were recruited. Rescuer current from S-ICDs was significantly higher than those from T-ICDs (S-ICD: Median RMS 135 mA range 91 mA-164 mA, T-ICD: Median RMS 31 mA, range 9 mA-75 mA, P < 0.0001). Surface voltages (median RMS) to which the rescuer is likely to be exposed are higher when performing chest compressions from the patient's left side compared with the right (127 V vs 67 V respectively, 95% CI of difference -34 V to -67 V, P < 0.0001). Rescuers performing chest compressions on ICD patients are at risk from leakage current, particularly from S-ICDs. Chest compressions should be performed from the opposite side to the ICD to reduce rescuer risk.