Patent ID: 7076283

Claim:
A device adapted to perform a cardiac sensing-mode switch so to sense cardiac activity in the presence of magnetic resonance imaging (MRI) interference that exceeds a threshold of about 0.20 Tesla but not to perform said mode switch in the presence of electromagnetic interference (EMI) that does not exceed a threshold of about 0.20 Tesla, comprising: means for detecting a magnetic field consistent with the characteristics of an MRI scanning device and providing an MRI interference signal related to the detection of the magnetic field; and switching means coupled to the means for detecting, for switching from a first cardiac activity sensing mode that is relatively more affected by the MRI interference signal to a second cardiac activity sensing mode that is relatively less affected by the magnetic field in response to receipt of the MRI interference signal, wherein in the event that a detected EMI field strength falls below about 0.20 Tesla then no switching of the first cardiac activity sensing mode occurs; wherein the second cardiac activity sensing mode employs at least one of the following cardiac activity sensing circuitry disposed within an implantable medical device; a can-based accelerometer, a pressure sensor on a lead, an accelerometer on a lead, an accelerometer coupled to a connector block a flow sensor, a heart motion sensor based on time-of-flight, a temperature sensor, an impedance-based sensor, an oxygen sensor.