Systems and methods for switching modes in a multi-device medical system. In one example, a first leadless cardiac pacemaker (LCP) may be implantable at a ventricular site, and a second leadless cardiac pacemaker (LCP) may be implantable at an atrial site and configured to sensing atrial contractions. The first LCP and the second LCP may be configured to be communicatively coupled such that the first LCP and the second LCP can deliver pacing therapy to the ventricular site in a tracking mode. The first LCP and/or the second LCP may additionally be configured to deliver pacing therapy to the ventricular site in a non-tracking mode if an interval between atrial contractions sensed by the second LCP becomes shorter than a threshold duration.
