Prospective evaluation of the quality and long-term stability of atrial signals in non-thoracotomy defibrillation electrodes:: Comparison of four different endocardial electrograms

Documentation of atrial signals in stored endocardial electrograms of modern implantable cardioverter-defibrillators (IGD) is a useful tool to classify the underlying arrhythmia leading to device therapy. Newest generations of ICD provide near- and far-field electrograms derived between various endocardial electrodes. The aim of this prospective study was to assess the quality and longterm stability of atrial signals in different far-field configurations including the active can housing. Methods and Results: A total of 300 real-time endocardial electrogram recordings in 60 consecutive patients with a modern ICD in subpectoral position were analysed at the time of implant, pre-hospital discharge, 1, 3 and 12 months follow-up. Four different configurations were evaluated: right ventricular coil to can housing, can housing to pace! sense ring, right ventricular coil to pace/sense tip, and pace/sense tip to pace/sense ring. The best visibility of p-waves at an EGG-resolution of 0.5 mV/mm was seen in the can to coil configuration (77% of the patients). In the can to pace/sense ring electrogram p-waves could be observed in 58% of the patients. No p-waves were visible to pace/sense tip to pace! sense ring. At a resolution of 1.0 mV/mm p-waves were only visible in 10% of all patients exclusively in the can housing to right ventricular coil configuration. The results were stable (100% of the patients) over a follow-up of one year. Conclusions: Endocardial far-field electrograms, derived from the can housing and the right ventricular coil provide a p-wave visibility in 77% of the patients and demonstrate a long-term stability over at least one year, provided that the EGG-resolution is set at 0.5 mV/mm. Since the electrogram resolution of stored electrograms depends on the EGM-range, and the EGG-resolution at an EGM-range of 15 mV would be 1 mV/mm, the EGM-range is recommended to be programmed to 7.5 mV to ensure an EGG-resolution of at least 0,5 mV/mm for stored electrograms.