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 mea suring biomagnetic fields produced by small animals. Using this system, we measured the magnetocardiogram (MCG) of rats. The specifications of our sys tem were as 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 mm between the pickup coil and the outside surface of the dewar. The field sensitivity was 100-fT/ root Hz in the white noise frequency. Five adult r ats, 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 magnetocardiogram signals was performed over 2000 cardiac cycles. Exiting sites of cardiac muscles were analyzed by minimum norm estimation o f MCG. Current sources coresponding to electric activities on the atrium an d ventricle of rats were estimated.