An implantable cardiac stimulation device is equipped with an isolation system capable of attenuating or eliminating induction currents flowing through the stimulation device by eliminating induction loops. The isolation system comprises a magnetic insulator configured to shield selected components of the stimulation device from external magnetic fields or radio-frequency (RF) signals. The magnetic insulator comprises a plurality of sensors that are configured to detect the intensity of the external magnetic fields and/or RF signals, and a switch bank that electrically isolates certain components of the stimulation device to eliminate the induction loops. The isolation system further comprises an attenuation system comprised of at least one magnetoresistor disposed along potential induction loops to attenuate induction currents when subjected to undesirable external magnetic fields and/or RF signals.