Various techniques for using an accelerometer to detect cardiac contractions are described. One example method described includes filtering a signal received by an electrical sensing channel of an implantable medical device (IMD) configured to detect electrical depolarizations of a heart of a patient, identifying a failure of the electrical sensing channel of the IMD based on the filtered signal and, in response to identifying the failure, initiating a mechanical sensing channel of the implantable medical device to identify mechanical cardiac contractions.
