An implantable cardiac monitor (ICM) may be configured to be deployed subcutaneous, submuscular, or substernal at a position that enables the ICM to detect cardiac activity. In some cases, the ICM includes a housing that includes a body portion and a tail portion. A first electrode may be disposed adjacent a first end of the body portion, a second electrode may be disposed adjacent a second end of the body portion and a third electrode may be disposed adjacent a tail end of the tail portion. A controller may be disposed within the housing and may be operably coupled to the first electrode, the second electrode and the third electrode. The controller may be configured to select a pair of the first electrode, the second electrode and the third electrode to use for sensing cardiac electrical activity and to communicate information about the sensed activity to a second medical device.