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

BACKGROUND: 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.

OBJECTIVE: 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.

METHODS: 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.

RESULTS: 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).

CONCLUSIONS: 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.