BODY-SURFACE POTENTIALS DURING DISCHARGE OF THE IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR

Body Surface Potentials During ICD Discharge. Introduction: Little is known about the hazard for persons in contact with patients experienci ng a high-voltage discharge of their implantable cardioverter defibril lator (ICD), Compared to epicardial systems, this risk may be increase d with transvenous electrode systems and particularly in active can co nfigurations, Methods and Results: In 23 patients with a transvenous a ctive can ICD system, body surface potentials V-s and current through an external resistance were measured during 35 discharges, V-s was det ected using skin electrodes positioned over the left subpectorally imp lanted pulse generator [C], apex of the heart [A], and the right pecto ral region [RP], Mean V-s during discharges without an external shunt resistance ranged between 13 and 63.8 V [C to A] and 12.5 to 47.3 V [C to RP] (ICD peak stored/output voltage V-cap = 183 to 606 V, n = 20), Mean current flow [C to A] was 8.2 to 46.8 mA (V-cap = 288 to 633 V, n = 10) and 42 to 120.7 mA (V-cap = 447 to 579 V, n = 5) across a resi stance of 1,696 and 797 Omega, respectively, Conclusion: During high-o utput shocks, a considerable potential difference is present on the bo dy surface of ICD patients that, according to the literature, may indu ce a single cardiac response in a bystander, Analogous to spontaneous extrasystoles, there is only a minimal chance of triggering a tachyarr hythmia by this stimulated extra beat, Direct induction of ventricular fibrillation is unlikely, since reported fibrillation threshold value s are much higher than the observed magnitudes of current and voltage.