An implantable medical device system for delivering cardiac pacing, comprising: a first, sensing, device comprising a power transmitter , sensing circuitry , a control module , a first housing enclosing the power transmitter, the sensing circuitry and the control module, a plurality of sensing electrodes , and an extra-cardiovascular sensing extension extending from the first housing and carrying at least one of the plurality of sensing electrodes, the control module configured to: identify a first cardiac event by identifying a P-wave from a cardiac electrical signal received by the sensing circuitry via the plurality of sensing electrodes, identify a second cardiac event by identifying an R-wave; determine an interval between the P-wave and the R-wave; and set a first pacing interval to be less than the interval between the P-wave and the R-wave in response to identifying the cardiac event, and control the power transmitter to transmit power upon expiration of the first pacing interval; and a second, pacing pulse delivery, device comprising a pacing electrode pair , a second housing , and a power receiver enclosed by the second housing, the power receiver coupled to the first pacing electrode pair, the first pacing electrode pair carried by the second housing; wherein the power receiver is configured to receive the transmitted power and deliver at least a portion of the received power to a patient's heart via the first pacing electrode pair. a first, sensing, device comprising a power transmitter , sensing circuitry , a control module , a first housing enclosing the power transmitter, the sensing circuitry and the control module, a plurality of sensing electrodes , and an extra-cardiovascular sensing extension extending from the first housing and carrying at least one of the plurality of sensing electrodes, the control module configured to: identify a first cardiac event by identifying a P-wave from a cardiac electrical signal received by the sensing circuitry via the plurality of sensing electrodes, identify a second cardiac event by identifying an R-wave; identify a first cardiac event by identifying a P-wave from a cardiac electrical signal received by the sensing circuitry via the plurality of sensing electrodes, identify a second cardiac event by identifying an R-wave; determine an interval between the P-wave and the R-wave; and set a first pacing interval to be less than the interval between the P-wave and the R-wave in response to identifying the cardiac event, and control the power transmitter to transmit power upon expiration of the first pacing interval; and set a first pacing interval to be less than the interval between the P-wave and the R-wave in response to identifying the cardiac event, and control the power transmitter to transmit power upon expiration of the first pacing interval; and a second, pacing pulse delivery, device comprising a pacing electrode pair , a second housing , and a power receiver enclosed by the second housing, the power receiver coupled to the first pacing electrode pair, the first pacing electrode pair carried by the second housing; wherein the power receiver is configured to receive the transmitted power and deliver at least a portion of the received power to a patient's heart via the first pacing electrode pair. <EOS>