INTERFERENCE WITH CARDIAC DEFIBRILLATORS BY DIGITAL AND ANALOGIC CELLULAR TELEPHONES

Background and objectives. Functional pacemaker interference by mobile telephones has been described with analogical systems and with possib le greater influence, digital systems, including inhibition and inadeq uate pacing. The influence of both systems has not been extensively st udied in patients with implantable cardioverter defibrillators (ICD). Patients and methods. We studied the influence of mobile phones, both digital and analogic network, on the performance of several models of defibrillators, in a standardised test set up designed to provide high sensitivity. The purpose of our study was to establish whether there are any influences on ICD functions, both in in vivo and in in vitro m odels. Several mobile phones, with different transmission powers, were moved towards the defibrillator and the electrode, under continuous d ocumentation of defibrillator sensing and interrogation afterwards. Th e experimental model was performed with the aid of an arrhythmia simul ator (Intersim(R)) and demo-defibrillators. The tests were repeated bo th in and out of a solution of saline water with an impedance within n ormal human Limits. Results. Partial loss of telemetry was found in 14 patients, 8 with analogical phones and 6 with digital phones. Fourtee n patients showed alterations only on the surface electrocardiogram ch annel and five on the intracavitary channel. The same results were rep roduced in the in vitro model. However, the in vitro test allowed us t o simulate multiple ventricular arrhythmias, and demonstrate the norma l sensing and functioning of the defibrillator during a ''spontaneous' ' arrhythmia. After testing, we demonstrate that no real oversensing/u ndersensing was documented in any device. There was no evidence of ICD reprogramming or pacing inhibition. In particular, no inadequate ther apies were delivered. Conclusions. a) in our series, we have not demon strated clinically significant electromagnetic interferences with mobi le phones of digital or analogical networks; b) the in vitro model all owed us to conclude that even if a spontaneous arrhythmia appears, the function of the defibrillator is not altered; c) the use of mobile ph ones seems to be safe for defibrillator patients, and d) however, some basic rules, such as to maintain the phone at least 15 cm away from t he defibrillator, are advised.