Separation of cardiac conduction system and atrial activities by spatial regression

Multiple channel magnetocardiography is potentially useful for the study of the cardiac conduction system. However, normal atrial repolarization occurs simultaneously and obscures the interpretation of the net signal. Magnetocardiographic data in four normal subjects at rest and mild exercise were found to exhibit high spatial correlation during atrial activation. Based on measured channel-to-channel covariances, the atrial repolarization signals as measured in channels in the null zone of conduction system activity were used to estimate atrial repolarization in all channels. A linear prediction method was used which based on the "kriging" estimator of geostatistical theory. Due to high spatial correlations in the limited thoracic region studied, predictions based on a single null channel were found to be adequate. Removal of the atrial component facilitates the beat-by-beat estimation of conduction system changes during rest and exercise using the multiple channel biomagnetometer.