One embodiment of the present invention provides an implantable cardioverter-defibrillator for subcutaneous positioning between the third rib and the twelfth rib within a patient, the implantable cardioverter-defibrillator including a housing including a first electrode; a telescoping lead assembly including a second electrode, wherein the telescoping lead assembly is electrically and mechanically coupled to the housing; and an electrical circuit located within and electrically coupled to the housing.