An implantable medical system is configured to coordinate ventricular pacing with intrinsic depolarizations of another chamber. The implantable medical system includes a leadless pacing device implanted on or within the ventricle. Another implantable medical device is configured to sense an intrinsic depolarization the other chamber of the heart of the patient, and in response to the intrinsic depolarization of the other chamber, deliver an electrical pulse. The leadless pacing device is configured to detect the electrical pulse delivered by the other implantable medical device and, in response to detecting the electrical pulse delivered by the other implantable medical device, deliver a pacing pulse to the ventricle via at least a first electrode in coordination with the intrinsic depolarization of the other chamber.