Blood-flow tubing

1. An intravascular stent comprising:

a tubular member having an internal surface and an external surface,

wherein the tubular member has an internal helical formation to induce spiral-flow therethrough, and wherein the internal helical formation is provided on a portion of the internal surface and the internal surface extends beyond said portion,

wherein the internal helical formation has a helix angle between 5 and 50 degrees relative to a longitudinal axis of the stent, and wherein the tubular member is selected from the group consisting of:

(a) a tubular mesh member;

(b) a tubular member formed from a wire; or

(c) a tubular member of a mesh material that is formed from expanded sheet.

2. The stent according to claim 1 , wherein the tubular member is expansible and is inserted by catheterization in collapsed form and which becomes expanded on release from the catheter, the internal helical formation being attached to the portion of the internal surface of the tubular member.

3. The stent according to claim 1 , wherein the tubular mesh member is formed from a wire and comprises crisscrossed wires extending helically around the periphery of the stent, and the internal helical formation comprises a helical vane member attached to such wires.

4. The stent according to claim 1 , wherein the tubular mesh member, the wire or the expanded sheet is made from metal.

5. The stent according to claim 1 , wherein the wire is a wire spring.

6. The intravascular stent according to claim 1 , wherein the helix angle is between 5 and 16 degrees relative to the longitudinal axis of the tubular member.

7. The intravascular stent according to claim 6 , wherein the helix angle is about 16 degrees relative to the longitudinal axis of the tubular member.

8. The intravascular stent according to claim 1 , wherein the helix angle of the internal helical formation is adjustable.

9. The intravascular stent according to claim 1 , wherein the internal helical formation is a ridge.