Quantifying intracardiac organization by combined spectral and spatial phase analysis of the electrocardiogram

We hypothesized that ECGs exhibiting a predominant spectral peak reflect temporal regularity, and that waves that maintain their shape between axes reflect spatial regularity, in cardiac activation. We analyzed ECGs of 38 patients at electrophysiologic study (EPS). Atrial or ventricular activity was depicted as a series of correlation values of a template to the ECG over time. In regular supraventricular or ventricular arrhythmias at invasive EPS, temporal phase was maintained since ECG spectra showed peaks ≥ 6dB magnitude, and spatial phase was maintained between axes since correlation time-series, plotted for lead V5 vs aVF (XY), V5/V1 (XZ) and aVF/V1 (YZ), resulted in reproducible loops parallel to the lines of identity. Supraventricular or ventricular arrhythmias with non-uniform intracardiac spatial or temporal activation did not maintain temporal or spatial phase. Analysis was insensitive to the effects of simulated noise, baseline wander, altered gain and template selection.