Implantation of a cardiac stimulus system using the intercostal veins. Superior, intercostal, and inferior access methods are discussed and disclosed. Superior access may be performed by entering the brachiocephalic vein from a jugular, subclavian, or other vein, and then accessing the internal thoracic vein, traversing a portion of the internal thoracic vein and then accessing an intercostal vein therefrom. Inferior access may be accomplished inferior to the lower rib margin via the superior epigastric vein, advancing superiorly into the internal thoracic vein and then accessing an intercostal vein therefrom. Intercostal access may include creating an opening in an intercostal space between two ribs and advancing a needle using ultrasound guidance to enter the intercostal vein directly.