A cardiac rhythm management apparatus includes a proximal housing, a distal housing and a lead. The proximal housing includes a first energy storage device. The distal module is implantable within a patient's heart, and includes a second energy storage device, at least one electrode, and a control module. The control module controls the delivery of at least one electrical stimulus from the second energy storage device to a location in communication with the patient's heart. The lead connects the proximal housing to the distal module and is configured to communicate one or more digital signals between the proximal housing and the distal module.