An apparatus comprises an implantable cardiac signal sensing circuit that provides an electrical cardiac signal representative of cardiac activity of a subject, an implantable therapy circuit that delivers electrical pacing stimulation energy to a heart of a subject, and a controller circuit. The controller circuit includes a chronotropic incompetence detection circuit that initiates pacing of an atrium of the subject at a rate higher than a device-indicated rate or a sensed intrinsic rate, monitor the AV interval, initiates an increase in the pacing rate while continuing the monitoring of the AV interval, calculates a change in AV intervals between a highest paced rate used in the monitoring and a lowest paced rate used in the monitoring, and indicates that the AV intervals are evidence of chronotropic incompetence when the calculated change in the AV intervals exceeds a specified threshold AV interval change value.