Implantation of a cardiac stimulus system into the mediastinum using the ITV. Superior, intercostal, and inferior access methods are discussed and disclosed. Superior access may be performed using the brachiocephalic vein to access the ITV, with access to the brachiocephalic vein achieved using subclavian vein, using standard visualization techniques. Inferior access may be accomplished inferior to the lower rib margin via the superior epigastric vein. Intercostal access may include creating an opening in an intercostal space between two ribs and advancing a needle using ultrasound guidance.