Patent ID: 7853318

Claim:
A method of determining a heart rate from a physiological electrical signal received in an implantable medical device, the method comprising: (i) receiving an input associated with the presence of an environment that tends to cause corruption of a physiological electrical signal; and (ii) initiating a mode of operation for reducing corruption of the physiological electrical signal, the mode of operation comprising (a) providing a high and a low bandwidth amplifier in an implantable medical device, wherein the high bandwidth amplifier has a bandwidth of at least 4 kHz and the low bandwidth amplifier has a bandwidth equal no greater than 1 kHz; (b) providing a switch configured to select between the high bandwidth and low bandwidth amplifiers, wherein the switch is switched to utilize the high bandwidth amplifier if corruption of the physiological electrical signal is detected; (c) amplifying the physiological electrical signal with the selected amplifier; (d) sampling the amplified physiological electrical signal at a sampling frequency of at least 8 kHz to obtain a first sequence of samples; (e) processing the first sequence of samples to identify a superposed signal artifact characteristic of MRI interference; (f) reducing the superposed signal artifact from the first sequence of samples to form a second sequence of samples; and (g) processing the second sequence of samples to identify the timing of heart contractions.