A device for introduction into a body vessel includes a main elongated element, a balloon positioned at the main elongated element distal end, a distal connecting element positioned at the distal end of the balloon to receive a guidewire during use, and a longitudinally movable sheath positioned external to the main elongated element, a position of the sheath distal end with respect to the balloon defining an exposed portion of the balloon that expands when fluid is delivered to the balloon through the inflation lumen.