Systems and methods for coordinating treatment of abnormal heart activity using multiple implanted devices. In one example, a method of operating a medical system may comprise determining, by a first one of a plurality of implantable medical devices, a presence of an arrhythmia, wherein the first one of a plurality of implantable medical devices uses a first discrimination method to determine the presence of an arrhythmia, determining, by a second one of the plurality of implantable medical devices, a presence of an arrhythmia, wherein the second one of a plurality of implantable medical devices uses a second discrimination method to determine the presence of an arrhythmia, and communicating, by the first one of the plurality of implantable medical devices to a second one of the plurality of implantable medical devices, a message that is indicative of a detected arrhythmia by the first one of a plurality of implantable medical devices.
