A system comprising an implantable medical device (IMD). The IMD comprises a ventricular heart signal sensing circuit to provide a ventricular heart signal, at least one sensor operable to provide an electrical signal representative of patient activity, a sensor interface circuit coupled to the at least one sensor to provide an activity signal, and a controller circuit coupled to the heart signal sensing circuit and the sensor interface circuit. The controller circuit is operable to determine whether ventricular ectopy occurs during recovery from exercise using the heart signal, and to set at least one warning indicator if ventricular ectopy occurs during the recovery from exercise.