Methods and devices for cutting tissue

Abstract

A catheter is provided, which includes a cutting element having one or more raised elements. The cutting element has a cup-shaped surface at the distal end that may be smooth and continuous except for the raised elements.

Claims

1. An atherectomy catheter, comprising: a body having opposite proximal and distal ends; a rotatable shaft coupled to the body; a cutting element adjacent the distal end of the body and coupled to the rotatable shaft, such that the rotatable shaft is able to rotate the cutting element through a complete rotation about a longitudinal axis of the cutting element, the cutting element having opposite first and second longitudinal ends, a cutting edge extending circumferentially at the first longitudinal end of the cutting element, and an interior surface recessed longitudinally from the cutting edge; and a raised element extending longitudinally outward from the interior surface of the cutting element toward the first longitudinal end of the cutting element, the raised element having a first side wall extending inward from the interior surface generally toward the longitudinal axis of the cutting element, and a longitudinal end wall defining a longitudinal end surface of the raised element which intersects the first side wall to form a first raised edge of the raised element, wherein the raised element further has a second side wall extending inward from the interior surface generally toward the longitudinal axis of the cutting element, wherein the longitudinal end surface of the raised element intersects the second side wall to form a second raised edge of the raised element.

2. The catheter of claim 1, wherein the longitudinal end surface of the raised element forms an angle from 30 degrees to 90 degrees with respect to the longitudinal axis of the cutting element.

3. The catheter of claim 1, wherein the first raised edge has inner and outer ends relative to the longitudinal axis of the cutting element, wherein the inner end of the first raised edge is spaced radially inward from the cutting edge a distance of 0.0010 in (0.0254 mm) to 0.0020 in (0.0508 mm).

4. The catheter of claim 1, wherein the first raised edge has inner and outer ends relative to the longitudinal axis of the cutting element, wherein the outer end of the first raised edge is recessed longitudinally from the cutting edge.

5. The catheter of claim 4, wherein the first raised edge has inner and outer ends relative to the longitudinal axis of the cutting element, wherein the outer end of the first raised edge is recessed from the cutting edge by a longitudinal distance of 0.0010 in (0.0254 mm) to 0.0020 in (0.0508 mm).

6. The catheter of claim 1, wherein the second raised edge is recessed longitudinally relative to the first raised edge.

7. The catheter of claim 1, wherein the rotatable shaft is configured to rotate the cutting element so that the first raised edge is the leading edge and the second raised edge is the trailing edge.

8. The catheter of claim 1, wherein the raised element further has an inner wall extending between and intersecting the first and second side walls and the longitudinal end wall and the interior surface of the cutting element, respectively.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a distal end of an atherectomy catheter.

(2) FIG. 2 is a cross-sectional view of the atherectomy catheter with a cutting element in as stored position.

(3) FIG. 3 is a cross-sectional view with a cutting element in a working position;

(4) FIG. 4 shows an embodiment of a cutting element;

(5) FIG. 5 shows an end view of an embodiment of a cutting element;

(6) FIG. 6 is a cross-sectional view of an embodiment of a cutting element;

(7) FIG. 7 shows another embodiment of a cutting element which may be used with the atherectomy catheter;

(8) FIG. 8 shows the embodiment of the cutting element of FIG. 7 and FIG. 8A shows one of the raised elements of the cutting element embodiment.

DETAILED DESCRIPTION

(9) Referring to FIGS. 1-4, an atherectomy catheter 2 is shown which has a cutting element 4, which is used to cut material from a blood flow lumen. The cutting element 4 is movable between a stored position (FIG. 2) and a cutting position (FIG. 3) relative to an opening 6 in a body 8 of the catheter 2. The cutting element 8 moves outwardly relative to the opening 6 so that a portion of the element 4 extends outwardly from the body 8 through the opening 6. The cutting element 4 may be positioned relative to the body 8 and opening 6 so that less than 90 degrees of the cutting element 4 is exposed to cut tissue. Of course, more of the cutting element 4 may he exposed without departing from numerous aspects of the invention.

(10) The catheter 2 is moved distally through a vessel with the cutting element 4 in the working or cutting position as described in further detail below. As the catheter 2 moves through the blood vessel, the tissue is cut by the cutting element 4 and is directed into a tissue chamber 12 positioned distal to the cutting element 4. The tissue chamber 12 may be somewhat elongate to accommodate the tissue, which has been cut.

(11) The cutting element 4 is moved proximally from the stored position so that a cam surface 14 on the cutting element 4 engages a ramp 16 on the body 8 of the catheter 2. The interaction between the cam surface 14 and the ramp 16 causes the cutting element 4 to move to the cutting position and also causes a tip 18 to deflect which tends to move the cutting element 4 toward the tissue to be cut.

(12) The cutting element 4 is coupled to a shaft 20 that extends through a lumen 21 in the catheter 2. The cutting element 4 is rotated about a longitudinal axis LA when the shaft rotates. The cutting element 4 is rotated about 1 to 160,000 rpm but may be rotated at any other suitable speed depending upon the particular application.

(13) Referring to FIGS. 2, 4 and 5, the cutting element 4 is shown when viewed along the longitudinal axis LA. The term along the longitudinal axis as used herein shall mean the view of FIG. 5 that shows the distal end of the cutting element 4 when viewed in the direction of the longitudinal axis and/or the axis of rotation. The cutting element 4 has a cutting edge 22 that may be a continuous, uninterrupted, circular-shaped edge although it may also include ridges, teeth, serrations or other features without departing from the scope of the invention. The cutting edge 22 may be at a radially outer edge 23 of the cutting element 4 when the cutting element 4 is in the cutting position.

(14) The cutting element 4 has a cup-shaped surface 24, which directs the tissue cut by the cutting edge 22 into the tissue chamber 12. The cup-shaped surface 24 may be a smooth and continuous surface free of throughholes, teeth, fins or other features, which disrupt the smooth nature of the surface 24 for at least half the distance from the longitudinal axis LA to the outer radius at the cutting edge 22. The cup-shaped surface 24 may also be free of any such features throughout an area of at least 300 degrees relative to the longitudinal axis LA.

(15) Referring to FIG. 4-6, one or more raised elements 26 extend outwardly from the cup-shaped surface 24 with FIG. 5 showing two raised elements 26. The raised element 26 is a small wedge of material that rises relatively abruptly from the cup-shaped surface 24. The raised element 26 has a first wall 30 and a second wall 32 that both extend radially and form an angle of about 20 degrees therebetween so that the two raised elements 26 together occupy an area of about 40 degrees and altogether may be less than 60 degrees. A third wall 34 extends between the radially inner portion of the first and second walls 30, 32. The raised element 26 helps to break up hard tissue and plaque by applying a relatively blunt force to the hard tissue or plaque since cutting such tissue with the cutting edge 22 is often not effective.

(16) The raised elements 26 altogether occupy a relative small part of the cup-shaped surface 24. The raised elements 26 together may occupy less than 5% of as surface area of the cutting element 4. The term surface area of the cutting element as used herein shall mean the surface area which is radially inward from the outer or cutting edge 22 and is exposed when viewed along the longitudinal axis LA. Stated another way, at least 95% of the surface area of the cutting element is a smooth cup-shaped surfaced when viewed along the longitudinal axis. By sizing and positioning the raised element 26 in this manner, the raised element 26 does not interfere with the ability of the cutting element 4 to cut and re-direct tissue into the tissue chamber while still providing the ability to break up hard tissue and plaque with the raised element 26.

(17) The raised element 26 may be recessed from the cutting edge 22 longitudinally and/or radially. The raised element 26 may be recessed longitudinally from the cutting edge 0.0010 to 0.0020 inch and may be about 0.0015 inch. The raised element 26 may be recessed radially from the cutting edge 22 by about the same amount. A distal wall 38 of the cutting element 4 forms a flat surface 40, which is perpendicular to the longitudinal axis LA so that the entire surface is recessed the same distance from the cutting edge. The distal wall 38 may take any other shape, such as a curved shape, or may be tilted, inclined or beveled as now described.

(18) Referring to FIGS. 7, 8 and 8A, another cutting element 4A is shown wherein the same or similar reference numbers refer to the same or similar structure and all discussion concerning the same or similar features of the cutting element 4 are equally applicable here. The cutting element 4A has a cutting edge 22A that may be a continuous, uninterrupted, circular-shaped edge although it may also include ridges, teeth, serrations or other features without departing from the scope of the invention. The cutting edge 22A may he at a radially outer edge 23A of the cutting element 4A when the cutting element 4A is in the cutting position. The cutting element 4A has a cup-shaped surface 24A that directs the tissue cut by the cutting edge 22A into the tissue chamber 12 (see FIG. 2). The cup-shaped surface 24A may be a substantially smooth arid continuous surface as described shove in connection with the cutting element 4.

(19) One or more raised elements 26A, extend outwardly from the cup-shaped surface 24A. FIG. 8 shows four raised elements 26A but may include any number such as 2, 3, 4, 6 or 8 raised elements. The raised clement 26A is a small wedge of material that rises relatively abruptly from the cup-shaped surface 24A. The raised element 26A has a first wall 30A and a second wall 32A which both extend radially and form an angle of about 1 to 30 degrees therebetween so that the four raised elements 26A together occupy an area of about 4 to 60 degrees and altogether may be less than 60 degrees altogether. A third wall 34A extends between the radially inner portion of the first and second walls 30A, 32A. The raised elements 26A may occupy a relative small part of the cup-shaped surface 24A and may be recessed from the cutting edge 22A in the manner described above in connection with the cutting element 4.

(20) A distal wall 38A of the cutting element 4A has a surface 40A that forms an angle of about 30-90 degrees with respect to the longitudinal axis LA. The entire surface 40A may still be somewhat close to but recessed from the cutting edge 22A so that the entire surface 40A is 0.0010 to 0.0050 inch from the cutting edge. An edge 50 formed at the intersection of wall 30A and distal wall 38A is closer to the cutting edge 22A than an edge 52 formed at the intersection of wall 32A and distal wall 38A. The cutting element 4A may be rotated in either direction so that the raised edge 50 may be the leading or trailing edge. The raised edge may be 0.0010 to 0.0020 inch from the cutting edge. The raised elements 26A may all be formed in the same manner or may be different from one another. For example. some of the elements 26A could be angled in different directions so that two of the elements have the raised edge 50 as the leading edge and two of the elements 26A have the raised edge 50 as the trailing edge. The raised elements 26A may also subtend different angles, be of different heights or may have different radial lengths without departing from various aspects of the present invention.

(21) Use of the catheter 2 is now described in connection with the cutting element 4 but is equally applicable to use of the catheter 2 with the cutting element 4A. The catheter 2 is introduced into the patient in a conventional manner using a guidewire (not shown) or the like. The catheter 2 is advanced with the cutting element in the stored position of FIG. 2 until the catheter is positioned at the location where material is to be removed. The cutting element 4 is then moved proximally so that the ramp 16 and cam surface 14 engage to move the cutting element 4 to the cutting position of FIG. 3 and to deflect the tip of the catheter 2. to move the cutting element 4 toward the tissue, to be cut. The cutting element 4 is rotated about longitudinal axis LA and catheter 2 is then moved distally through the vessel so that the cutting element 4 cuts tissue. The tissue, which has been cut, is directed into the tissue chamber 12.

(22) The present invention has been described in connection with preferred embodiments but may, of course, be practiced while departing from the above described embodiments. For example, three or more raised elements may be provided or cutting edge may be serrated without departing from numerous aspects of the present invention.