A vascular occluder (10) includes a tubular support element (12) and a sleeve (30) of occluding material disposed within the support element (12). The sleeve (30) is twisted in the support (12) creating a constriction (36) which closes the lumen (40) of the sleeve (30). The lumen (40) of the sleeve (30) can nevertheless be opened by a guide wire (54) or cannula (52) for over the wire delivery. Once the guide wire (54) or cannula (52) are withdrawn from the sleeve (30), the sleeve (30) will close again by the action of blood pressure thereon. Blood pressure will act to maintain closing pressure on the sleeve (30), thereby avoiding or reducing the risk of recanalization.
