Millimetre-scale magnetocardiography of living rats with thoracotomy

Magnetocardiography is a contactless imaging modality for electric current propagation in the cardiovascular system. Although conventional sensors provide sufficiently high sensitivity, their spatial resolution is limited to a centimetre-scale, which is inadequate for revealing the intra-cardiac electrodynamics such as rotational waves associated with ventricular arrhythmias. Here, we demonstrate invasive magnetocardiography of living rats at a millimetre-scale using a quantum sensor based on nitrogen-vacancy centres in diamond. The acquired magnetic images indicate that the cardiac signal source is well explained by vertically distributed current dipoles, pointing from the right atrium base via the Purkinje fibre bundle to the left ventricular apex. We also find that this observation is consistent with and complementary to an alternative picture of electric current density distribution calculated with a stream function method. Our technique will enable the study of the origin and progression of various cardiac arrhythmias, including flutter, fibrillation, and tachycardia. Causes of heart failure can be investigated by tracing imperfections in electrical current propagation on the millimetre scale; however, the spatial resolution of current magnetocardiograph methods are limited to the centimetre-scale. Here, the authors report a millimetre-scale nitrogen vacancy-based quantum sensing to measure the magnetic field generated by the heart of a living rat, from which the cardiac electrical currents can be extrapolated.