GSM Cellular Phones Interference with Implantable Ventricular Defibrillators

Abstract

Implantable cardioverter defibrillators (ICD) are automatic arrhythmia management devices designed to detect ventricular tachycardia (VT), fast ventricular tachycardia (FVT) or ventricular fibrillation (VF) and, upon detection, deliver the programmed pacing cardioversion or defibrillation therapies. In addition these devices provide bradycardia pacing therapy. An ICD constantly monitors the cardiac rhythm for adequate short-term therapy delivery by means of one lead in the right ventricle and, only in dual chamber ICDs, another lead in the right atrium. When an event occurs, the ICD measures its amplitude. The sensitivity is automatically adjusted on the basis of the measured amplitude until a new event is sensed at the end of the absolute refractory period. Heart rhythm detection is usually based on the classification of R-R intervals into three classes: slow rhythm (SR), ventricular tachycardia and ventricular fibrillation. The ICD makes this classification by measuring the R-R interval and comparing it to programmable boundaries: VT and VF cycle length. Ventricular tachycardia detection occurs when the corresponding R-R interval is longer than the VF cycle length and shorter than or equal to the VT cycle length, and the cumulative number of VT detections are equal to a programmed parameter (N_VT). Ventricular fibrillation detection occurs when the corresponding R-R interval is shorter than or equal to the VF cycle length and the cumulative number of VF detections are equal to a programmed parameter (N_VF). Sinus rhythm detection occurs when the corresponding R-R interval is longer than the VT and VF cycle lengths. The treatment to apply in case of an SR detection or VF detection is unambiguous. However, a VT detection can indeed be: sinus tachycardia, supraventricular tachycardia (atrial fibrillation, flutter or atrial tachycardia) or ventricular tachycardia. In order to distinguish between them, single chamber ICDs adopt dedicated algorithms. If tachycardia is detected ICD delivers pulse burst or ramp for antitachycardia stimulation or cardioversion therapy via the combined pacing/sensing/shock electrode.