Beat-to-beat variability of T-wave in multichannel magnetocardiogram and 12-lead electrocardiogram during physiological interventions

The autonomic nervous system regulates cardiac function by modulating heart rate and cardiac contractility. Changes in sympathetic and parasympathetic activity have effects on the amplitude and duration of the cardiac action potentials and conduction velocity. So far, no studies have been published on changes in MCG caused by rapid autonomic adaptation. For clinical applications of MCG it is important to clarify whether interventions involving changes in autonomic activity produce distinct changes in the MCG signal. Autonomic function tests cause fast adaptation in the cardiovascular system. Therefore, monitoring the change in the MCG signal beat by beat is essential in the analysis of the data recorded. In this study we test the feasibility of MCG recordings during several simple, non-invasive physiological interventions affecting cardiovascular autonomic function and thoracic geometry in different manners. We also present an analysis method for extracting magnetic field maps from each cardiac cycle of the raw data and quantifying their change. We apply the method in the MCG data recorded, and examine the dynamic changes in magnetic field maps. In stress studies, the T-wave inversion in MCG of healthy subjects, not detected in ECG, has been of great interest. Therefore, the analysis is focused on the T-wave.