Interference of electronic apex locators with implantable cardioverter defibrillators

The purpose of this in vitro study was to evaluate the potential electromagnetic interference of electronic apex locators (EALs) on implantable cardioverter defibrillators (ICDs).

Four different EALs were tested for their ability to interfere with the correct function of 3 different ICDs. Each ICD was placed in a plastic container with 1.5 L physiological saline, and the EAL unit was placed at a distance of 2.5 cm from the ICD. The file electrode and lip clip were placed directly against the ICD. The EAL was turned on for 30 seconds while continuously showing the "APEX" mark. As a negative control, the ICD was tested without EAL for 30 seconds. An electrosurgical unit served as a positive control. During each test, the ICD output was monitored continuously by real-time telemetry, and after completion of the experiment, intracardiac electrocardiograms were printed. The tests were repeated 3 times for each device. The electrocardiograms were examined for interference on ICD ventricular activity.

All EALs tested and the negative control failed to produce electromagnetic interference in each of the ICDs tested. The electrosurgical unit induced interference in the ICDs, which were detected as episodes of ventricular tachycardia and led to the initiation of electrical shocks in all ICDs.

The 4 EALs tested did not interfere with the correct functioning of ICDs in vitro.