An implantable cardiac defibrillator (ICD) system includes an ICD implanted subcutaneously in a patient, a defibrillation lead having a proximal portion coupled to the ICD and a distal portion having a defibrillation electrode configured to deliver a defibrillation or cardioversion shock to a heart of the patient, and a pacing lead that includes a distal portion having one or more electrodes and a proximal portion coupled to the ICD. The distal portion of the pacing lead is implanted at least partially along a posterior side of a sternum of the patient within the anterior mediastinum. The ICD is configured to provide pacing pulses to the heart of the patient via the pacing lead and provide defibrillation shocks to the patient via the defibrillation lead. As such, the implantable cardiac system provides pacing from the substernal space for an extravascular ICD system.