A tether holder has a locking portion, for securing a proximal end of a tether, and a pin portion that may fit within a receptacle of a handle assembly of a tool. A distal member of an inner assembly of the tool engages an implantable medical device, from which the tether extends, through at least one lumen of the inner assembly and out through a proximal port of the handle assembly, which is located in proximity to the receptacle. An enlarged distal-most portion of a deployment tube of the tool contains the distal member and the device, and is moveable, relatively to the inner assembly and the device, to deploy the device out through a distal opening of the tool. The handle assembly may also include a flush lumen and a tether engaging conduit, both in fluid communication with the at least one lumen of the inner assembly.