High resolution magnetocardiography for the study of dynamic propagation of excitation sites in rat cardiac muscles

We have developed a multichannel high-resolution SQUID magnetometer for measuring biomagnetic fields produced by small animals. Using this system, we measured the magnetocardiogram (MCG) of rats. The specifications of our system were m follows: pickup coils 5 mm in diameter located on a 7.5-mm grid, a 15-mm gradiometer baseline, a one-turn pickup coil with a distance of 5 ram between the pickup coil and the outside surface of the dewar. The field sensitivity was 100-fT/ f Hz in the white noise frequency. Five adult rats, ranging in weight from 0.2 - 0.4 kg, were used in the study. Rats were anesthetized intraperitoneally with Nembutal ( 40mg / 1kg ). Averaging of the magnetocardiograin signals was performed over 2000 cardiac cycles. Exiting sites of cardiac muscles were analyzed by minimum norm estimation of MCG. Current sources coresponding to electric activities on the atrium and ventricle of rats were estimated,.