An implantable cardiac tissue excitation system includes an implantable pacing controller unit with a pulse generation circuit. The system also includes a lead with a lead body extending between a proximal lead end attachable to the pacing controller unit and a distal lead end configured to be implanted within a heart. A lead conductor extends within the lead body. The system also includes a transmitter assembly located near the distal lead end that is electrically connected to the pulse generation circuit through the lead conductor to wirelessly transmit pacing control information and pacing energy. The system also includes a leadless electrode assembly configured to be implanted within the heart that includes a receiver to receive the wireless transmission, a charge storage unit to store the charge energy, and an electrical stimulation circuit to deliver an electrical stimulus to cardiac tissue using the pacing control information and the charge energy.