Catheter atherotome

• US 5,071,424 A
• Filed: 02/27/1991
• Issued: 12/10/1991
• Est. Priority Date: 08/18/1989
• Status: Expired due to Fees

• Current Assignee: Synectic Ventures III LLC (Synectic Asset Management, Inc.), Synectic Ventures II LLC (Synectic Asset Management, Inc.), Synectic Ventures I LLC (Synectic Asset Management, Inc.)
• Original Assignee: Evi Corp.
• Inventors: Reger, Vincent A.
• Primary Examiner(s): Thaler, Michael H.
• Application Number:
  US07/660,918
• Time in Patent Office: 286 Days
• Field of Search: 606/159, 606/160, 606/170, 606/161, 606/200, 128/751, 15/104.19, 604/22
• US Class Current: 606/159
• CPC Class Codes: A61B 17/00008 Vein tendon strippers tube strippers A61M1/83
• CPC Class Codes: A61B 17/064 Surgical staples, i.e. penetrating the tissue
• CPC Class Codes: A61B 17/32075 Pullback cutting; combined forward and pullback cutting, e.g. with cutters at both sides of the plaque
• CPC Class Codes: A61B 2017/22051 with an inflatable part, e.g. balloon, for positioning, blocking, or immobilisation A61B2017/22048, A61B2017/3486 take precedence
• CPC Class Codes: A61B 2017/320741 for stripping the intima or the internal plaque from a blood vessel, e.g. for endarterectomy
• CPC Class Codes: A61B 2090/062 penetration depth
• CPC Class Codes: A61M 2025/09183 having tools at the distal tip

Abstract

A catheter atherotome and method for its use for performing partial atherectomy in an artery and thereby enlarging the lumen effectively available for blood flow through the artery. Several blades are mounted at a distal end of a catheter, in a helical basket configuration and spaced angularly apart from one another about the associated ends of two concentric sheaths in such a way that longitudinal and rotary relative movement of the sheaths selectively bows the blades arcuately outwardly into a cutting position or draws the blades flat into alignment with the sheaths. The blades have sharpened cutting edges extending helically and directed toward the catheter'"'"'s proximal end when the blades are bowed. Partial removal of an atheroma is effected by manually pulling the basket knife past an atheroma with the basket blades in their outwardly bowed cutting positions, with the speed, force, and amount of expansion of the blades determined by the operator. Removal of cut-away pieces of atherosclerotic plaque material is accomplished either by pull-back of a balloon embolectomy catheter or by use of a latex membrane enshrouding the spiral wire blades to trap the shavings within the membrane.

Claims

1. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said blades into a radially outwardly bowed arcuate configuration; and

(e) at least some of said blades defining respective sharp edges, at least a portion of each said sharp edge extending alongside said inner member and facing generally more toward said proximal ends than toward said distal ends of said outer sheath and said inner member, the ones of said blades arranged over approximately one-half the circumference of said outer sheath and inner member including said sharp edges while the remainder of said blades are free from said sharp edges.

2. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said blades into a radially outwardly bowed arcuate configuration; and

(e) at least some of said blades defining respective knife-like sharpened edges, at least a portion of each said knife-like sharpened edge extending alongside said inner member and being oriented more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said blades are in said outwardly bowed arcuate configuration, so as to engage plaque associated with an inner wall of an artery cuttingly as said catheter atherotome is moved within said artery in a proximal direction, without engaging said interior wall of said artery cuttingly as said catheter atherotome is moved within said artery in a distal direction, each of said blades defining a knife-like sharpened edge including a middle portion defining said knife-like sharpened edge and a pair of intermediate portions adjacent said middle portion, said intermediate portions being sufficiently more flexible than said middle portion that said middle portion substantially retains its original shape during flexing of said blades into said radially outwardly bowed arcuate configuration.

3. The catheter atherotome of claim 2 wherein said inner member defines lumen means for receiving a guide wire extending through said inner member for guiding said catheter atherotome within said artery.

4. The catheter atherotome of claim 2 wherein said means for moving said inner member includes lever-operated means for moving said inner member longitudinally with respect to said outer sheath and means associated with said inner member for rotating said inner member with respect to said outer sheath.

5. The catheter atherotome of claim 2 wherein each of said elongate blades includes flexible portions thereof which do not define an edge thereof.

6. The catheter atherotome of claim 2 wherein said inner member defines a central longitudinal axis, and including means for preventing at least one of said ends of each of said blades from rotating with respect to said outer sheath and said inner member about an axis extending generally parallel with said central longitudinal axis, while permitting a terminal portion of each of said blades to rotate about an axis extending substantially perpendicular to said central longitudinal axis, between a position in which said terminal portion extends generally parallel with said longitudinal axis and a position in which said terminal portion extends away from said longitudinal axis at an acute angle and said middle portion of said blade is displaced radially away from said longitudinal axis.

7. The catheter atherotome of claim 6 wherein at least one said terminal portion of each of said blades includes fin means for defining a bore, said bore defining an axis of rotation of said at least one terminal portion relative to a respective one of said inner member and said outer sheath to which said at least one end is attached.

8. The catheter atherotome of claim 2 wherein each of said knife-like sharpened edges of said blades is located in a cutting position exposed toward said proximal end of said outer sheath and extending generally circumferentially about said inner member when said distal end of said inner member is retracted toward said distal end of said outer sheath and said blades are in said outwardly bowed arcuate configuration.

9. The catheter atherotome of claim 2 wherein said inner member is tubular, further including balloon-tipped catheter means, disposed within and extending through said inner member and having an inflatable balloon tip located distally beyond said distal end of said inner member and blades, for retaining and retrieving pieces of material cut free from an atheroma during use of said catheter atherotome.

10. The catheter atherotome of claim 2 further including skirt means of flexible membranous material, arranged about said blades for retrieving pieces of material from within an artery.

11. The catheter atherotome of claim 2, said plurality of blades defining a basket when said distal end of said inner member is retracted toward said distal end of said outer sheath, said basket defining an equator, and said respective knife-life sharpened edges of said blades being located along said equator portion of said basket.

12. The catheter atherotome of claim 2 said intermediate portions being resiliently flexible and twistable, and each said knife-like sharpened edge normally being oriented helically about a central longitudinal axis of said inner member and defining an angle of attack, said angle of attack being shallow enough so that said knife-like sharpened edge ordinarily will not cuttingly engage the surface of the interior tissue of a healthy artery but great enough so that said knife-like sharpened edge will cuttingly engage atherosclerotic plaque projecting from the interior surfaces of an artery, said intermediate portions being torsionally elastic enough to permit said middle portions of said blades to rotate resiliently to a position in which said knife-like sharpened edges can engage and pare away a portion of said plaque material from said interior surfaces of said artery.

13. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate inner member disposed within said outer sheath, said inner member having respective proximal and distal ends and defining a central longitudinal axis and said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said blades into a radially outwardly bowed arcuate configuration;

(e) at least some of said blades defining respective sharp edges, at least a portion of each said sharp edge extending alongside said inner member and facing generally more toward said proximal ends than toward said distal ends of said outer sheath and said inner member;

(f) means for preventing at least one of said ends of each of said blades from rotating with respect to said outer sheath and said inner member about an axis extending generally parallel with said central longitudinal axis, while permitting a terminal portion of each of said blades to rotate about an axis extending substantially perpendicular to said central longitudinal axis, between a position in which said terminal portion extends generally parallel with said longitudinal axis and a position in which said terminal portion extends away from said longitudinal axis at an acute angle and said middle portion of said blade is displaced radially away from said longitudinal axis;

(g) fin means included in at least one of said terminal portions of each of said blades, for defining a bore, each said bore defining an axis of rotation of a respective one of said terminal portions relative to a respective one of said inner member and said outer sheath to which said respective one of said terminal portions is attached; and

(h) mounting means for attachment of said blades to said inner member and said outer sheath, said mounting means defining radial slot means for cooperating with said fin means of each of said blades, so as substantially to prevent said terminal portions of each of said blades from rotating about an axis parallel with said central longitudinal axis of said inner member.

14. The catheter atherotome of claim 13 wherein said mounting means includes a distal fitting fixedly attached to said inner member, a distal end of each of said blades being movably attached to said distal fitting.

15. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate flexible tubular outer sheath having respective proximal and distal ends;

(b) an elongate flexible tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate knife blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) at least some of said knife blades defining respective knife-like sharp edges, at least a portion of each said knife-like sharp edge extending alongside said inner member and facing more toward said proximal ends than toward said distal ends of said outer sheath and said inner member, said knife blades defining a diameter of said catheter atherotome and each knife blade having a pitch with respect to said inner member;

(e) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said knife blades into a radially outwardly bowed arcuate configuration of increased diameter; and

(f) means for rotating said inner member with respect to said outer sheath so as to control the pitch of said knife blades.

16. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate flexible tubular outer sheath having respective proximal and distal ends;

(b) an elongate flexible tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate knife blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) at least some of said knife blades defining respective knife-like sharp edges, at least a portion of each said knife-like sharp edge extending alongside said inner member and facing more toward said proximal ends than toward said distal ends of said outer sheath and said inner member, said knife blades defining a diameter of said catheter atherotome and each knife blade having a pitch with respect to said inner member;

(e) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said knife blades into a radially outwardly bowed arcuate configuration of increased diameter; and

(f) means for controlling said pitch and said diameter while using said catheter atherotome.

17. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said blades into a radially outwardly bowed arcuate configuration; and

(e) at least some of said blades defining respective sharp edges, at least a portion of each said sharp edge extending alongside said inner member and being oriented more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said blades are in said outwardly bowed arcuate configuration, so as to engage plaque associated with an inner wall of an artery cuttingly as said catheter atherotome is moved within said artery in a proximal direction, without engaging said interior wall of said artery cuttingly as said catheter atherotome is moved within said artery in a distal direction and at least one of said sharp edges having respective opposite first and second ends, said first and second ends thereof being angularly separated from each other by a controllably variable angle about said inner member when said blades are in said outwardly bowed arcuate configuration.

18. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said blades into a radially outwardly bowed arcuate configuration; and

(e) at least some of said blades defining respective sharp edges, at least a portion of each said sharp edge extending alongside said inner member and being oriented more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said blades are in said outwardly bowed arcuate configuration, so as to engage plaque associated with an inner wall of an artery cuttingly as said catheter atherotome is moved within said artery in a proximal direction, without engaging said interior wall of said artery cuttingly as said catheter atherotome is moved within said artery in a distal direction and some of said blades being free from sharp edges and being located opposite said blades defining sharp edges, so as to contact an interior surface of an artery and distend said artery when said blades are in said radially outwardly bowed arcuate configuration.

19. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate knife blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said knife blades into a radially outwardly bowed arcuate configuration defining a cutting diameter; and

(e) said knife blades having sharpened front edges and blunt back margins, each of said knife blades including a middle portion, defining said sharpened front edge, and a pair of opposite intermediate portions, said intermediate portions being sufficiently more flexible than said middle portion that said middle portion substantially retains its original shape as said knife blade flexes into said outwardly bowed configuration and said sharpened front edges overlapping one another about said outer sheath and being oriented more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said knife blades are at any of a plurality of predetermined cutting diameters, providing complete circumferential coverage of said artery so as to cut through a stenotic lesion as said catheter atherotome is moved in the proximal direction in said artery.

20. The catheter atherotome of claim 19 wherein said inner member defines interior bore means for receiving a guide wire for guiding said catheter atherotome within said artery.

21. The catheter atherotome of claim 19, said plurality of knife blades defining a basket when said distal end of said tubular inner member is retracted toward said distal end of said outer sheath, said basket defining an equator portion and said sharpened front edges of said knife blades being located in said equator portion of said basket and being directed spirally with respect to said outer sheath of said catheter atherotome.

22. The catheter atherotome of claim 19 wherein each of said elongate knife blades includes flexible portions thereof which are free of sharpened edges.

23. The catheter atherotome of claim 19 wherein said inner member defines a central longitudinal axis, said intermediate portions being resiliently flexible and twistable, and said middle portions each including a respective one of said sharpened front edges, each sharpened front edge normally being oriented spirally about said central longitudinal axis and defining an angle of incidence, said angle of incidence being shallow enough that said sharpened edge will not cuttingly engage the surface of healthy interior tissue of an artery but great enough so that said sharpened edge will cuttingly engage atherosclerotic plaque projecting from the interior surfaces of an artery, said intermediate portions being torsionally elastic enough to twist sufficiently to permit said middle portions of said blades to reach a position in which said edges can engage and pare away said plaque material from said interior surfaces of said artery.

24. The catheter atherotome of claim 19 wherein said inner member defines a central longitudinal axis, and including means for preventing at least one of aid ends of each of said knife blades from rotating with respect to said outer sheath and said inner member about an axis extending generally parallel with said central longitudinal axis, while permitting a terminal portion of each of said knife blades to pivot in a radial plane including said central longitudinal axis, between a position in which said terminal portion extends generally parallel with said longitudinal axis and a position in which said terminal portion extends away from said longitudinal axis at an acute angle and said middle portion of said knife blade is displaced radially away from said longitudinally axis.

25. The catheter atherotome of claim 24 wherein said terminal portion of each of said knife blades includes means for defining a bore, said bore defining an axis about which said terminal portion can pivot relative to said inner member and said outer sheath.

26. The catheter atherotome of claim 19 wherein said means for moving said inner member includes means defining a scale for indicating the position of said inner member with respect to said outer sheath and thus providing an indication of a cutting diameter within said artery and for measuring said artery following removal of said plaque from said artery.

27. The catheter atherotome of claim 19 wherein each of said sharpened front edges of said knife blades is located in a cutting position, exposed toward said proximal end of said outer sheath and extending generally circumferentially about said inner member when said distal end of said inner member is retracted toward said distal end of said outer sheath and said knife blade members are in said outwardly bowed arcuate configuration.

28. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate knife blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said knife blades into a radially outwardly bowed arcuate configuration defining a cutting diameter; and

(e) said knife blades having sharpened front edges and blunt back margins, and having respective opposite first and second ends, said first and second ends thereof being angularly separated from each other by a controllably variable angle about said inner member when said knife blades are in said outwardly bowed arcuate configuration and said sharpened front edges overlapping one another about said outer sheath and being oriented more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said knife blades are at any of a plurality of predetermined cutting diameters, providing complete circumferential coverage of said artery so as to cut through a stenotic lesion as said catheter atherotome is moved in the proximal direction in said artery.

29. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate knife blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said knife blades into a radially outwardly bowed arcuate configuration defining a cutting diameter; and

(e) said knife blades having sharpened front edges and blunt back margins, said means for moving said inner member including means for rotating said inner member with respect to said outer sheath, so as to alter the inclination of said sharpened front edges with respect to said outer sheath and thus with respect to a stenotic lesion to be cut by said catheter atherotome and said sharpened front edges overlapping one another about said outer sheath and being oriented more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said knife blades are at any of a plurality of predetermined cutting diameters, providing complete circumferential coverage of said artery so as to cut through a stenotic lesion as said catheter atherotome is moved in the proximal direction in said artery.

30. A catheter atherotome for use in surgical removal of plaque from the interior wall of an artery, comprising:

(a) an elongate tubular outer sheath having respective proximal and distal ends;

(b) an elongate tubular inner member disposed within said outer sheath and having respective proximal and distal ends, said distal end of said inner member extending beyond said distal end of said outer sheath;

(c) a plurality of elongate knife blades each having a proximal end interconnected with said outer sheath and a distal end interconnected with said inner member;

(d) means for moving said inner member with respect to said outer sheath so as to retract said distal end of said inner member toward said distal end of said outer sheath and flex said knife blades into a radially outwardly bowed arcuate configuration; and

(e) at least some of said knife blades defining respective knife-like sharpened edges, at least a portion of each said knife-like sharpened edge extending alongside said inner member and facing generally more toward said proximal ends than toward said distal ends of said outer sheath and said inner member when said knife blades are in said outwardly bowed arcuate configuration, some of said knife blades being free from sharpened edges and being located opposite respective ones of said knife blades defining knife-like sharpened edges, so as to contact an interior surface of an artery and support said knife-like sharpened edges with respect to said interior surface of said artery when said knife blades are in said radially outwardly bowed arcuate configuration.

31. The catheter atherotome of claim 30, said plurality of knife blades defining a basket when said distal end of said inner member is retracted toward said distal end of said outer sheath, said basket defining an equator portion and said respective sharpened edges of said knife blades being located in said equator portion of said basket and being directed spirally with respect to said outer sheath of said catheter atherotome.

32. The catheter atherotome of claim 30 wherein each of said elongate knives includes flexible portions thereof which are free of sharpened edges.

33. The catheter atherotome of claim 30 wherein each of said knives defining a sharpened edge includes a middle portion defining said sharpened edge and a pair of opposite intermediate portions, said intermediate portions being sufficiently more flexible than said middle portion that said middle portion substantially retains its original shape as said knife blade flexes into said radially outwardly bowed configuration.

34. The catheter atherotome of claim 30 wherein each of said knife members defining a sharpened edge includes a pair of opposite intermediate portions and a middle portion, said intermediate portions being resiliently flexible and twistable, and said middle portion including said sharpened edge and normally being oriented spirally about a central longitudinal axis of said inner member and defining an angle of incidence, said angle of incidence being shallow enough so that said sharpened edge will not cuttingly engage the surface of healthy interior tissue of an artery but great enough so that said sharpened edge will cuttingly engage atherosclerotic plaque projecting from the interior surface of an artery, said intermediate portions being torsionally elastic enough to twist sufficiently to permit said middle portions of said blades to reach a position in which said edges can engage and pare away said plaque from said interior surface of said artery.

35. The catheter atherotome of claim 30 wherein said knife blades have respective opposite first and second ends, said first and second ends thereof being angularly separated from each other by a controllably variable angle about said inner member when said knives are in said outwardly bowed arcuate configuration.

36. The catheter atherotome of claim 30 wherein said inner tubular member defines a central longitudinal axis, and including means for preventing at least one of said ends of each of said knife blades from rotating with respect to said outer sheath and said inner tubular member about an axis extending generally parallel with said central longitudinal axis, while permitting a terminal portion of each of said knives to pivot in a radial plane including said central longitudinal axis, between a position in which said terminal portion extends generally parallel with said longitudinal axis and a position in which said terminal portion extends away from said longitudinal axis at an acute angle and said middle portion of said knife is displaced radially away from said longitudinal axis.

37. The catheter atherotome of claim 36 wherein said terminal portion of each of said knife blades includes means for defining a bore, said bore defining an axis about which said terminal portion can pivot relative to said inner member and said outer sheath.

38. The catheter atherotome of claim 30 wherein said means for moving said inner member includes means for rotating said inner member with respect to said outer sheath, so as to alter the inclination of said sharpened front edges with respect to said outer sheath and thus with respect to a stenotic lesion to be cut by said catheter atherotome.

39. The catheter atherotome of claim 30 wherein said means for moving said inner member includes means defining a scale for indicating the position of said inner member with respect to said outer sheath and thus providing an indication of a cutting diameter within said artery and for measuring said artery following removal of said plaque from said artery.

40. The catheter atherotome of claim 30 wherein each of said sharpened edges of said knife blades is located in a cutting position, exposed toward said proximal end of said outer sheath and extending generally circumferentially about said inner member when said distal end of said inner member is retracted toward said distal end of said outer sheath and said knife blade members are in said outwardly bowed arcuate configuration.

41. The catheter atherotome of claim 30 wherein at least one of said knife blades which are free from sharpened edges is located so as to distend said artery when said knife blades are in said radially outwardly bowed arcuate configuration.

42. The catheter atherotome of claim 30 wherein said inner member defines lumen means for receiving a guide wire extending through said inner member for guiding said catheter atherotome within said artery.