Small diameter intravascular catheter with screw tip and limited torsional displacement

1. An intravascular catheter to be passed over a guidewire, the catheter comprising:

a rigid screw portion comprising a rigid hollow cylindrical shaft having a substantially constant diameter, the rigid hollow shaft defining a cylindrical lumen longitudinally therethrough and said screw portion having a rigid helical thread portion extending outwardly from an outer surface of the hollow shaft; and

a tubular portion formed from a substantially rigid material, having a length, joined substantially coaxially to the screw portion and defining a lumen that is continuous with the lumen of the screw portion, the tubular portion including at least two slits defined along at least some of the tubular portion, the two slits having a pattern geometry that limits torsional displacement of at least a portion of the catheter, the at least two slits having a first end and a second end, the first end and the second end being longitudinally displaced from one another along the length of the tubular portion, wherein the lumen of the screw portion and the lumen of the tubular portion are dimensioned to pass over a guidewire.

2. The catheter as claimed in claim 1 ,

in which the tubular portion has a first diameter and the hollow shaft of the screw portion has a second diameter and the first and second diameter are substantially equal;

the helical thread portion has a first handedness and the slits are generally helical and have a second handedness opposed to the first handedness;

the slits are generally helical and the generally helical slits further include sigmoid curves that repeat along the length of the tubular portion with a substantially regular periodicity;

the tubular portion has a diameter of about two French and further comprising an inner liner and an outer coating; and

a hub having a lumen joined substantially coaxially to the tubular portion.

3. The catheter as claimed in claim 1 , in which the helical thread portion has an outside diameter significantly larger than the second diameter of the hollow shaft.

4. The catheter as claimed in claim 3 , in which the first diameter of the helical thread portion is at least about one and one third times the second diameter of the hollow shaft.

5. The catheter as claimed in claim 1 , further comprising a torque device couplable to the tubular portion whereby torque can be applied to the tubular portion.

6. The catheter as claimed in claim 1 , in which the pattern geometry is such that torsional displacement is limited to a greater degree in a first rotational direction than in a second rotational direction.

7. A method of controlling flexibility and torsional displacement in an intravascular catheter, comprising:

forming a portion of the catheter from a unitary tubular substantially rigid structure having a wall and a length and defining a lumen;

piercing the wall with at least two continuous slits along a substantial portion of the length of the wall, each slit having a first end and a second end, the first end and the second end being longitudinally displaced from each other along the length of the tubular substantially rigid structure thereby imparting flexibility to the tubular substantially rigid structure; and

forming the slits with a pattern geometry that limits torsional displacement of at least a portion of the catheter.

8. The method as claimed in claim 7 , further comprising forming a helical thread portion at a distal end of the catheter that has a first handedness and forming the slits such that they are generally helical and have a second handedness opposed to the first handedness.

9. The method as claimed in claim 7 , further comprising forming the helical thread portion to have right handed pitch the slits have left handed pitch.

10. The method as claimed in claim 7 , further comprising forming the generally helical slits to further include sigmoid curves.

11. The method as claimed in claim 10 , further comprising forming the sigmoid curves to repeat along the length of the tubular portion with a substantially regular periodicity.

12. The method as claimed in claim 7 , further comprising constructing the pattern geometry such that torsional displacement is limited to a greater degree in a first rotational direction than in a second rotational direction.

13. The method as claimed in claim 7 , further comprising:

forming a helical thread portion at a distal end of the catheter that has a first handedness and forming the slits such that they are generally helical and have a second handedness opposed to the first handedness;

forming the generally helical slits to further include sigmoid curves;

forming the sigmoid curves to repeat along the length of the tubular portion with a substantially regular periodicity; and

constructing the pattern geometry such that torsional displacement is limited to a greater degree in a first rotational direction than in a second rotational direction.

14. An intravascular catheter to be passed over a guidewire, the catheter comprising:

a rigid screw portion comprising a rigid hollow cylindrical shaft having a substantially constant first diameter, the rigid shaft defining a hollow cylindrical lumen and said screw portion having a helical thread portion extending outwardly from an outer surface of the hollow shaft;

a tubular portion formed at least in part from a substantially rigid material, having a length, joined substantially coaxially to the screw portion and defining a lumen that is continuous with the lumen of the screw portion, the tubular portion having a second diameter substantially equal to the hollow shaft first diameter; and

a hub having a lumen joined substantially coaxially to the tubular portion.

15. The catheter as claimed in claim 14 , in which the tubular portion defines along a portion of its length at least two slits having a pattern geometry that limits torsional displacement of at least a portion of the catheter, the at least two slits having a first end and a second end, the first end and the second end being longitudinally displaced from each other along the length of the tubular substantially rigid structure.

16. The catheter as claimed in claim 15 , in which the helical thread portion has an outside diameter significantly larger than the first diameter of the hollow shaft.

17. The catheter as claimed in claim 14 , in which an outside diameter of the helical thread portion is at least about one and one third times the diameter of the first diameter of the hollow shaft.

18. The catheter as claimed in claim 15 , in which the helical thread portion has a first handedness and the slits are generally helical and have a second handedness opposed to the first handedness.

19. The catheter as claimed in claim 18 , in which the generally helical slits further include sigmoid curves that repeat along the length of the tubular portion with a substantially regular periodicity; and

further comprising a torque device couplable to the tubular portion whereby torque can be applied to the tubular portion; and

an inner liner and an outer coating.

20. The catheter as claimed in claim 14 , in which the tubular portion has a diameter of about two French.

21. The catheter as claimed in claim 15 , in which the pattern geometry is such that torsional displacement is limited to a greater degree in a first rotational direction than in a second rotational direction.

22. An intravascular catheter to be passed over a guidewire, comprising:

a screw portion comprising a hollow cylindrical shaft having a substantially constant first diameter, the shaft defining a hollow cylindrical lumen and said screw portion having a helical thread portion extending outwardly from an outer surface of the hollow shaft;

a tubular portion formed from a substantially rigid material, having a length, joined substantially coaxially to the screw portion and defining a lumen that is continuous with the lumen of the screw portion, the tubular portion having a second diameter substantially equal to the hollow shaft first diameter; and

a hub having a lumen joined substantially coaxially to the tubular portion;

in which the tubular portion defines along a portion of its length at least two slits having a pattern geometry that limits torsional displacement, the at least two slits having a first end and a second end, the first end and the second end being longitudinally displaced from each other along the length of the tubular portion;

in which the helical thread portion has an outside diameter significantly larger than the first diameter of the hollow shaft;

in which the helical thread portion has a first handedness and the slits are generally helical and have a second handedness opposed to the first handedness;

in which the generally helical slits further include sigmoid curves that repeat along the length of the tubular portion with a substantially regular periodicity;

in which the pattern geometry is such that torsional displacement is limited to a greater degree in a first rotational direction than in a second rotational direction;

in which the pattern geometry is such that torsional displacement is limited to a greater degree in a first rotational direction than in a second rotational direction; and

further comprising a torque device couplable to the tubular portion whereby torque can be applied to the tubular portion; and

an inner liner and an outer coating.