A stent for supporting part of a blood vessel includes a supporting portion around which or within which a part of an intact blood vessel other than a graft can be placed. The stent internally or externally supports that part of the blood vessel. The supporting portion of the stent is of a shape and/or orientation whereby flow within the vessel is caused to follow a non-planar curve. By maintaining a non-planar curvature in the vessel itself, favorable blood flow velocity patterns can be achieved through the generation therein of “swirl” flow. Failures in such vessels through diseases, such as thrombosis, atherosclerosis, intimal hyperplasia or through blockage, kinking or collaps, can be significantly reduced.