A delivery system assembly facilitating deployment of an implantable medical device, the assembly comprising: an elongate outer tube forming a lumen that extends from a proximal opening thereof at a proximal end of the outer tube to a distal opening thereof at a distal end of the tube, the lumen being sized to contain an entirety of the medical device therein in proximity to the distal opening thereof; an elongate inner member extending within the lumen of the outer tube; characterized by the inner member including a proximal end and an enlarged distal end, the enlarged distal end of the inner member being configured to conform to a proximal end of the medical device; and an elongate deflectable shaft extending within the lumen of the outer tube and around the inner member, the deflectable shaft including a distal end located proximal to the distal end of the inner member; wherein the outer tube and the inner member are longitudinally moveable, with respect to the deflectable shaft, and the outer tube including an internal shoulder and a distal-most portion that has a length, along which the lumen of the outer tube extends from the internal shoulder to a distal opening of the lumen, and the lumen of the outer tube, along the length of the distal-most portion, being sized to contain both the enlarged distal end of the inner member and an entirety of the implantable medical device; and wherein, when the enlarged distal end of the inner member is contained within the lumen of the outer tube, along the length of the distal-most portion, and abuts the internal shoulder of the outer tube, and the outer tube is moved longitudinally in a distal direction, the inner member is also moved longitudinally in the distal direction with respect to the shaft. an elongate outer tube forming a lumen that extends from a proximal opening thereof at a proximal end of the outer tube to a distal opening thereof at a distal end of the tube, the lumen being sized to contain an entirety of the medical device therein in proximity to the distal opening thereof; an elongate inner member extending within the lumen of the outer tube; characterized by the inner member including a proximal end and an enlarged distal end, the enlarged distal end of the inner member being configured to conform to a proximal end of the medical device; and an elongate deflectable shaft extending within the lumen of the outer tube and around the inner member, the deflectable shaft including a distal end located proximal to the distal end of the inner member; wherein the outer tube and the inner member are longitudinally moveable, with respect to the deflectable shaft, and the outer tube including an internal shoulder and a distal-most portion that has a length, along which the lumen of the outer tube extends from the internal shoulder to a distal opening of the lumen, and the lumen of the outer tube, along the length of the distal-most portion, being sized to contain both the enlarged distal end of the inner member and an entirety of the implantable medical device; and wherein, when the enlarged distal end of the inner member is contained within the lumen of the outer tube, along the length of the distal-most portion, and abuts the internal shoulder of the outer tube, and the outer tube is moved longitudinally in a distal direction, the inner member is also moved longitudinally in the distal direction with respect to the shaft.