An implantable medical device (IMD) may be configured into a sensing only mode in which the IMD does not delivery therapy. For example, the IMD may be configured to operate in a sensing only mode to reduce the undesirable effects that may be caused by external fields, such as those generated by an MRI device. However, there may be instances, such as a change in the patients condition, in which it may be desirable to transition from the sensing only mode to a pacing mode to provide therapy. In accordance with the techniques described herein, the IMD monitors signals on one or more leads coupled to the medical device while operating in the sensing only mode and transitions to a pacing mode in response to not detecting a minimum number of signals on the one or more leads.
