A vascular procedure includes sliding a constriction crossing mechanism over a wire guide having a tip positioned at a proximal side of a constriction, and rotating a sheath of the mechanism about an axis relative another sheath of the mechanism. The method further includes helically engaging the sheaths, and guiding an intraluminal treatment device into or past the vascular constriction. The mechanism includes a first sheath and a second sheath, and a tip coupled with the first sheath. The mechanism further includes a helical coupling between the first and second sheaths, which is configured to convert a torque on one of the sheaths to an axial force on the other of the sheaths for crossing a vascular constriction with the tip. An anchoring mechanism coupled with one of the sheaths includes a deployed state resisting displacement of the second sheath within a vascular structure of a patient.
