An implantable medical device system is configured to deliver cardiac pacing by receiving a cardiac electrical signal by sensing circuitry of a first device via a plurality of sensing electrodes, identifying by a control module of the first device a first cardiac event from the cardiac electrical signal, setting a first pacing interval in response to identifying the first cardiac event, controlling a power transmitter of the first device to transmit power upon expiration of the first pacing interval, receiving the transmitted power by a power receiver of a second device; and delivering at least a portion of the received power to a patient's heart via a first pacing electrode pair of the second device coupled to the power receiver.