A vascular intervention device delivery system, such as for implanting a self expanding stent, includes a thumbwheel rotatably mounted in a handle. The thumbwheel includes a radially outward facing thumb surface and a radially inward facing ratchet surface of a ratchet. A catheter has a proximal end attached to the handle, and a distal carrier segment for mounting a vascular intervention device thereon. A retractable sheath is movable from a first position covering the distal carrier segment to a second position retracted proximally uncovering the distal carrier segment. A pull extends between the thumbwheel and the retractable sheath. A ratchet pawl is mounted in the handle and has a catch in contact with the ratchet surface. The ratchet holds the thumbwheel against rotation in a forward direction, and the retractable sheath moves responsive to rotation of the thumbwheel in a reverse direction.
