On cardiac activity characterization from Implantable Cardioverter Defibrillator electrogram analysis: is far-field better?

The new generation of Implantable Cardioverter Defibrillators (ICDs) allows storage of intracardiac electrograms (EGMs) recorded immediately before the onset of malignant ventricular tachyarrhythmias (VTs) and during their course. Although all devices base most of diagnostic parameters on the bipolar EGMs, some of them allow two types of EGM recordings: bipolar (potential is obtained between two electrodes at the tip of the electrocatheter) and far-field (potential is recorded between the tip of the electrocatheter and the active can device). The main objective of this work is to study which differences can be observed from the analysis of bipolar or far-field EGMs when deterministic chaos methods are being applied to bipolar or far-field EGM recordings. For this analysis we considered 20 EGMs obtained from 6 patients with ICDs. Some of the EGMs contain VT episodes, other are collected in basal heart conditions. Within the limited set of EGM considered in this work, results indicate that far field recordings, monitoring the whole heart activity, allow better characterization of heart substrate, and they are more indicated when deterministic chaos analysis would be applied.