Coherence measures of cardiac arrhythmias from intra-cardiac and epicardial leads

The magnitude-squared coherence (MSC) spectrum is introduced as a dimensionless frequency-domain measure of rhythm organization from pairs of intracardiac and/or epicardial leads. The MS spectrum is simply defined as the magnitude of the complex cross-power-spectrum normalized to the product of the two individual auto-power-spectra. In this way, two linearly related signals (in the absence of uncorrelated additive noise) will have MSC values of unity at all signal frequencies present in both signals in any amount. Mean MSC values are shown to discriminate fibrillatory from nonfibrillatory rhythms. Speed/accuracy tradeoffs in estimation of the MSC are considered