A medical device is configured to sense a cardiac signal that includes far field ventricular event signals and determine a ventricular activity metric from the sensed cardiac signal. The ventricular activity metric may be representative of a ventricular rate or an atrioventricular time interval. The medical device is configured to determine an atrioventricular synchrony metric based on the ventricular activity metric and generate an output based on the atrioventricular synchrony metric. The device may include a memory configured to store data corresponding to the atrioventricular synchrony metric.