Functional similarity between electrograms recorded from an implantable cardioverter defibrillator emulator and the surface electrocardiogram

Clinical use of stored electrogram (EGM) configurations currently used in I CDs is limited. The hypothesis that EGMs recorded from electrodes on the IC D surface may improve diagnostic capabilities of the device was tested in t he present study, The Buttons on Active Can Emulator (BACE], an ICD-sized d evice containing four button electrodes, was temporarily placed into a subc utaneous or submuscular left pectoral pocket in 16 patients during ICD impl antation. Simultaneous recordings were obtained from the ECG lead II; bipol ar EGMs using RACE electrodes, and a bipolar atrial EGM during sinus rhythm ISR), ventricular pacing (VPI at cycle lengths of 500 and 400 ms, and VT. Visible P waves were present in all patients during SR (n = 15), in 5 (33%) of 15 patients during VP, and none of the patients during VT (n = 4) using RACE EGMs and lead II. P and QRS amplitudes and the P:QRS ratio during SR in RACE EGMs were significantly lower than those in lead n: BACE EGMs showe d prominent changes in QRS morphology and duration during VP and VT compare d to SR, and the magnitude of QRS prolongation during VP was similar to tha t in lead II. Measurements of PR, QRS, and QT duration during SR showed goo d agreement between RACE EGMs and lead II. In conclusion, EGMs recorded fro m electrodes embedded on the ICD housing may potentially improve visual dis crimination between supraventricular and ventricular arrhythmias. They also may be useful as a surrogate of the ECG for analysis and monitoring of dif ferent components of P-QRS-T complex.