A cardiac pacing system that includes an implantable pulse generator and electrical leads that include a lead body portion having a distal end and a proximal end, a connector configured to electrically connect the proximal end of the lead body to the pulse generator, and at least one electrode disposed at the distal end of the lead body for delivering electrical stimulation to a patient's heart, wherein the distal end of the lead body is configured to terminate within the mediastinum of the thoracic cavity of the patient, proximate to the heart.