WO1999030624A1

WO1999030624A1 - Apparatus and methods for removing occluding material from body lumens

Info

Publication number: WO1999030624A1
Application number: PCT/US1998/027029
Authority: WO
Inventors: John G. Stine; David W. Snow; John B. Simpson; Martin F. Overbeek Bloem
Original assignee: Fox Hollow Technologies
Priority date: 1997-12-17
Filing date: 1998-12-16
Publication date: 1999-06-24
Also published as: US6027514A

Abstract

An atherectomy catheter (10) comprises a catheter body (12) having a blade assembly (18) at its distal end. The blade assembly includes a first (20) blade and a second blade (22), where each blade has an opposed cutting edge (47, 49). At least one of the cutting edges will have a penetrating point (60) formed thereon. Preferably, both edges will have at least one aligned cutting point, more preferably at least two or more aligned cutting points. When the blades are actuated to shear tissue therebetween, the cutting points act to penetrate, and capture the material to be sheared. Optionally, the penetrating points may be staggered so that opposed points meet at different times as the blades are advanced relative to each other.

Description

APPARATUS AND METHODS FOR REMOVING OCCLUDING MATERIAL FROM BODY LUMENS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to apparatus and methods for removing occluding materials from body lumens. More particularly, the present invention relates to the construction and use of atherectomy catheters for excising atheroma and other materials from blood vessels.

Cardiovascular disease frequently arises from the accumulation of atheromatous material on the inner walls of vascular lumens, particularly arterial lumens of the coronary and other vasculature, resulting in a condition known as atherosclerosis. Atherosclerosis occurs naturally as a result of aging, but may also be aggravated by factors such as diet, hypertension, heredity, vascular injury, and the like. Atheromatous and other vascular deposits restrict blood flow and can cause ischemia which, in acute cases, can result in myocardial infarction. Atheromatous deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and/or calcified. In the latter case, the deposits are frequently referred to as plaque. Atherosclerosis can be treated in a variety of ways, including drugs, bypass surgery, and a variety of catheter-based approaches which rely on intravascular widening or removal of the atheromatous or other material occluding a blood vessel. Of particular interest to the present invention, a variety of methods for cutting or dislodging material and removing such material from the blood vessel have been proposed, generally being referred to as atherectomy procedures. Atherectomy catheters intended to excise material from the blood vessel lumen generally employ a rotatable and/or axially translatable cutting blade which can be advanced into or past the occlusive material in order to cut and separate such material from the blood vessel lumen. In particular, side- cutting atherectomy catheters generally employ a housing having an aperture on one side, a blade which is rotated or translated by the aperture, and a balloon or other deflecting structure to urge the aperture against the material to be removed. Although atherectomy catheters have proven to be very successful in treating many types of atherosclerosis, some catheter designs suffer from certain limitations. For example, many side-cutting atherectomy catheters have difficulty in capturing occluding material in the cutting aperture. To facilitate material capture, the cutting aperture is frequently elongated to increase the area into which the material can penetrate. While such elongation is effective, it requires an equivalent lengthening of the cutter housing. Most cutter housings are rigid, and such lengthening makes it more difficult to introduce the distal end of the catheter through torturous regions of the vasculature. Moreover, having a cutting blade travel over a lengthy cutter aperture increases the risk of penetrating the vascular wall.

For these reasons, it is desired to provide atherectomy catheters which can access small, tortuous regions of the vasculature and which can remove atheromatous and other occluding materials from within blood vessels in a controlled fashion with minimum risk of injuring the blood vessel wall. In particular, it is desired to provide atherectomy catheters which can facilitate capturing and invaginating atheromatous materials with relatively short cutter mechanisms. Desirably, the blade or blades of the atherectomy catheter will be actuable with the application of reasonable mechanical forces which are capable of being transmitted along even rather lengthy catheters. Further desirably, the catheters will be suitable for directional removal of occluding material and will include mechanisms for engaging cutting blades against selected portions of a vascular wall. Optionally, the engaging mechanisms should permit blood perfusion during performance of an atherectomy procedure. The catheters and methods for use in a variety of body lumens, including but not limited to coronary and other arteries. At least some of these objectives will be met by the catheter and method of the present invention described hereinafter and in the claims.

2. Description of the Background Art

Atherectomy catheters having axially reciprocatable, non-rotating blades are described in U.S. Patent Nos. 5,674,232 and 4,994,067. Other atherectomy catheters are described in U.S. Patent Nos. 5,571,130; 5,431,673; 5,312,425; 5,242,460; and 5,087,265. A household knife having a N-shaped cutting edge is described in U.S. Patent No. 2,178,790. Surgical cutters and biopsy devices having axially translatable and/or rotatable cutting blades are described in U.S. Patent Nos. 5,505,210; 5,395,313; 5,285,795; 5,226,910; 5,250,065; 3,815,004; 4,819,635; 4,696,298; 4,210,146; 3,995,619; 3,705,577; and Re. 33,258.

SUMMARY OF THE INVENTION According to the present invention, a catheter for removing occluding and other materials from a body lumen, particularly for removing atheromatous material from a blood vessel, comprises a catheter body having a proximal end and a distal end. First and second blades having cutting edges are disposed near the distal end of the catheter body, and an actuator is operatively linked to the blades to draw their respective cutting edges together to capture and shear material located between the blades. In order to facilitate capture of the material, at least one of the blades will have a cutting point disposed along its cutting edge in order to penetrate and engage material disposed between the blades. In particular, as the cutting blade having the penetrating point is advanced, the point will penetrate into the material and prevent the material from being pushed away from the blade.

Preferably, the cutting edges of both the first and second blades will have such penetrating points. More preferably, at least one of the penetrating points on the first cutting blade will be aligned with one of the penetrating points on the second cutting blade so that they meet as the blades are drawn together. By providing the blades with edges which recede from the penetrating points, preferably along arcuate lines, the cutting edges of the blades will provide an angled shearing motion which has been found to be very effective in capturing and shearing atheromatous and other occluding materials which are initially captured by the penetrating points. In particularly preferred embodiments, the cutting blades will each have at least two penetrating points aligned with each other, and even more preferably have at least three penetrating points aligned with each other. In a particular configuration, the cutting blades will each have at least two aligned penetration points, where the penetration points are "staggered" in the direction of cutting so that a first pair of aligned points will meet and penetrate tissue before a second pair of aligned points meet and penetrate tissue. It will be appreciated that two, three, four, or more individual pairs of points can be staggered in this fashion. Alternatively, two or more pairs of points may be arranged to meet simultaneously while other single pairs or groups of pairs can be arranged to meet at other times during the travel of the cutting blades. It has been found that staggering the penetration points in this manner can reduce the peak force required to penetrate shear tissue using the cutting blades.

The cutting edges may be drawn together in either an axial or circumferential direction. Usually, the cutting edges will not rotate or otherwise be moved with respect to each other, other than in the direction in which they are drawn together. In some instances, however, it may be desirable to oscillate the blades relative to each other in order to further enhance the shearing action. Such oscillation, however, may decrease the ability of the penetrating points to capture and maintain the occluding material between the blades. In a first exemplary embodiment, the cutting blades are drawn together in an axial direction (as defined with respect to the catheter body) by an actuator comprising a rod having a distal end attached to one of the blades and a proximal end having a slider for manual advancement, typically being disposed within a proximal hub or handle. Preferably, the rod will be radially offset within the catheter body and axially aligned with the cutting edge on the cutting blade. Such alignment transmits the cutting motion to the cutting edge of the blade in a direct, efficient manner.

In another aspect of the catheter, the first blade is fixedly attached to the distal end of the catheter body and the second blade is disposed to move within the first blade in order to pass the cutting edges by each other. In a specific embodiment, the first and second blades are arranged as coaxial tubes with side apertures which define the cutting edges. The cutting edges may be disposed transversely so that the cutting edges are axially opposed, in which case the actuator will translate the second blade axially relative to the first blade. Alternatively, the cutting edges may be disposed axially, in which case the actuator rotates the second blade relative to the first blade to draw the cutting blade together circumferentially. In either case, the inner blade may be spring- biased so that its cutting edge is aligned to shear closely against the cutting edge of the first blade. For example, the inner blade may be in the form of a split tube which is biased so that its outer surface engages an inner surface with the outer tubular blade. The catheter body can have a wide variety of configurations as are commonly used in the fabrication of intravascular catheters, particularly intravascular catheters intended for use in the coronary arteries. The dimensions, materials, flexibilites, and other structural aspects of intravascular catheter bodies are well known. The catheter body of the present invention will usually be configured to be placed over a guidewire and will thus include a guidewire lumen. As illustrated, the catheter is an "over-the-wire" design where the guidewire lumen extends generally from the distal tip of the catheter body all the way to or near the proximal end of the catheter body. Catheter bodies having shortened guidewire lumens, typically referred to as rapid exchange or monorail configurations, could also be used. In those cases, the guidewire will enter the catheter body at the distal tip but exit from the catheter body at a point closer to the distal end of the catheter body then the proximal end of the catheter body. Usually, the guidewire lumen exit port will be from 10 cm to 50 cm of the distal end, more usually from 15 cm to 30 cm. In an exemplary embodiment, the catheter body comprises an outer tubular body and an inner guidewire tube. The inner guidewire tube is usually, but not necessarily, located coaxially in the center of the outer tubular body. The inner guidewire tube will typically terminate at the tip of a soft conical catheter tip attached at the distal end of the catheter body, usually on the distal side of the cutter mechanism, as described above. The outer tubular body of the catheter can also accommodate other structural components, such as drive rods, drive tubes, cables, and the like, associated with translating or actuating the cutter blade(s), the urging mechanism, and any other mechanical features of the catheter as may be described elsewhere in this application. The catheters of the present invention will optionally further include a mechanism for urging the distal end of the catheter body in a transverse direction when the catheter body is in a body lumen, e.g., a blood vessel. For example, the urging mechanism may comprise a resilient ski that projects radially outwardly from the catheter body, typically on the side of the catheter body opposite to the cutting mechanism. In a first exemplary embodiment, the resilient ski is fully extended in the radial position in the absence of a constraining force, e.g., a guiding catheter or body lumen. In alternative embodiments, the resilient ski or other deflecting mechanism may be selectively actuated, e.g., using a radially extensible element and an axially translatable element which cooperate to extend the ski or other member radially outward. The urging mechanism could also comprise a balloon structure, although that is not presently preferred. In an exemplary embodiment, the urging mechanism comprises a pair of radially projecting resilient skis which are diametrically opposite to the cutting edge of the cutting blade(s). The skis are attached at their distal ends to the catheter body and/or a fixed component of the cutter mechanism so that the skis may be deployed radially outwardly by axial compression, i.e., pushing on their proximal ends. A preferred axially translatable element for actuating the skis comprises a tube which is slidably mounted over a fixed cable. A tube and cable actuator is preferred since it is quite flexible but permits relatively high axial compression forces to be transferred. It will appreciated, of course, that axially fixed tubes and axially slidable cables may also be used, either for actuating the urging mechanism or actuating the cutter blade(s), as described elsewhere in this application.

A preferred atherectomy catheter according to the present invention comprises a catheter body having a proximal end, a distal end, and a lumen therethrough. A first tubular blade having an interior is attached to the distal end of the catheter body so that its interior opens into the lumen of the catheter body. A second tubular blade is coaxially disposed within the interior of the first tubular blade. The blades each have side apertures defining transverse, opposed cutting edges, and each of the cutting edges has at least one penetrating point aligned with the penetrating point on the other cutting edge. An actuator is disposed at the proximal end of the catheter body and operatively connected to axially translate the second tubular blade relative to the first tubular blade to cause the penetrating points to penetrate material within the apertures and thereafter to cause the cutting edges to shear material within the apertures. The actuator typically comprises a rod, as described above, and the blades preferably include at least two aligned penetrating points, and more preferably at least three aligned penetrating points. The inner tubular blade is preferably radially spring-biased within the first tubular blade, as described above, and an urging mechanism may be provided on the outer tubular blade, also as discussed above.

The present invention still further provides methods for excising occlusive material from body lumens, particularly atheroma, thrombus, or plaque from within blood vessels, including the coronary arteries and peripheral vasculature. The method comprises disposing first and second blades within body lumen so that a cutting edge on each blade is on one side on the portion of the material to be removed. At least one of the cutting blades has a penetrating point on its cutting edge, preferably multiple (optionally staggered) cutting points as discussed above. The blades are then drawn together so that the penetrating point(s) penetrate into and capture said material. The blades are further drawn together to shear the portion with the cutting edges. In specific aspects of the method, the cutting blades are typically disposed within the body lumen by advancing a catheter intraluminally within the body lumen. The drawing/excising step will typically remove relatively small amounts of material, usually in the range from 0.005 mg to 5 mg, preferably in the range from 0.01 mg to 2 mg, usually from 0.01 to 1 mg. Thus, the method of the present invention may be repeated multiple times, typically from 10 times to 100 times, more typically from 25 times to 75 times, often from 40 to 60 times, in order to remove an occluding amount of atheromatous material from a blood vessel.

As discussed above in connection with the apparatus, the blades may be axially translated relative to each other or may be rotated in a circumferential direction relative to each other. The excised material may be captured within the catheter body and either extracted from the catheter body while the catheter remains in situ or retained within the catheter body and removed together with removal of the entire catheter. Although the provision of penetrating points greatly facilitates the capture and invagination of material to be removed into the cutting mechanism, the method may further comprise urging the cutting side of the catheter body against the material to be removed, typically using resilient skis as described above.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an atherectomy catheter constructed in accordance with the principles of the present invention.

Fig. 2 is a detailed view of the distal end of the atherectomy catheter of Fig. 1.

Fig. 2A is an enlarged view of the cutter blades of Fig. 2 with portions broken away.

Fig. 2B is a cross-section taken along line 2B-2B of Fig. 2A. Fig. 2C is an enlarged detail view illustrating how the honed edges of the cutting blades at the catheter of Fig. 2 A meet.

Figs. 3A-3E are top and detail views of the cutting mechanism of the atherectomy catheter of Figs. 1 and 2 illustrating axial translation of a second, inner cutting blade relative to a first, outer cutting blade.

Fig. 3F is an alternative configuration of a cutting mechanism having a pair of opposed cutting blades, according to the present invention. Figs. 4A-4D illustrate use of the atherectomy catheter of Figs. 1 and 2 for removing a portion of an occluding mass within a body lumen according to the method of the present invention.

Figs. 5A-5C illustrate alternative mechanisms for urging a distal end of an atherectomy catheter according to the present invention in a radial direction while the catheter is positioned within a body lumen.

Figs. 6A-6C illustrate an alternative cutter mechanism where axially aligned cutting edges of inner and outer cutting blades are rotationally advanced in a circumferential direction relative to each other. Fig. 7 illustrates an alternative embodiment of an inner cutter member having a plurality of cutting apertures.

Fig. 8A and 8B illustrate an alternative blade actuation mechanism. Fig. 9 illustrates a kit according to the present invention. Fig. 10 is a perspective view of the distal end of an alternative atherectomy catheter constructed in accordance with the principles of the present invention.

Fig. 11 is a cross-sectional view taken along line 11-11 of Fig. 10. Fig. 12 is cross-sectional view taken along line 12-12 of Fig. 10. Figs. 13A and 13B are cross-sectional views taken along line 13-13 of Fig. 12, with Fig. 13A showing an urging mechanism in a non-deployed configuration and Fig. 13B showing the same urging mechanism in a deployed configuration.

Figs. 14A-14D illustrate actuation of a cutting mechanism having opposed blades, each with three penetration points, wherein a central penetration point on each blade is staggered relative to the other penetration points.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

Apparatus and methods according to the present invention will generally be adapted for the intraluminal treatment of a target site within a body lumen of a patient, usually in a coronary artery or peripheral blood vessel which is occluded with atherosclerotic or other material. The apparatus and methods, however, are also suitable for treating other hyperplastic and neoplastic conditions in other body lumens, such as the ureter, the biliary duct, respiratory passages, the pancreatic duct, the lymphatic duct, and the like. Neoplastic cell growth will often occur as a result of a tumor surrounding and intruding into a body lumen. Removal of such material can thus be beneficial to maintain patency of the body lumen.

Apparatus according to the present invention will comprise catheters having catheter bodies adapted for intraluminal introduction to the target body lumen. The dimensions and other physical characteristics of the catheter bodies will vary significantly depending on the body lumen which is to be accessed. In the exemplary case of atherectomy catheters intended for intravascular introduction, the catheter bodies will typically be very flexible and suitable for introduction over a guidewire to a target site within the vasculature. In particular, catheters can be intended for "over-the-wire" introduction when a guidewire lumen extends fully through the catheter body or for

"rapid exchange" introduction where the guidewire lumen extends only through a distal portion of the catheter body. Catheter bodies intended for intravascular introduction will typically have a length in the range from 50 cm to 200 cm and an outer diameter in the range from 1 French (0.33 mm; Fr.) to 12 Fr., usually from 3 Fr. to 9 Fr. In the case of coronary catheters, the length is typically in the range from 125 to 200 cm, the diameter is preferably below 8 Fr., more preferably below 7 Fr., and most preferably in the range from 2 Fr. to 7 Fr. Catheter bodies will typically be composed of an organic polymer which is fabricated by conventional extrusion techniques. Suitable polymers include polyvinylchloride, polyurethanes, polyesters, polytetrafluoroethylenes (PTFE), silicone rubbers, natural rubbers, and the like. Optionally, the catheter body may be reinforced with braid, helical wires, axial filaments, or the like, in order to increase rotational strength, column strength, toughness, pushability, and the like. Suitable catheter bodies may be formed by extrusion, with one or more lumens being provided when desired. The catheter diameter can be modified by heat expansion and shrinkage using conventional techniques. The resulting catheters will thus be suitable for introduction to the vascular system, often the coronary arteries, by conventional techniques.

First and second cutting blades will be disposed at or near the distal end of the catheter body and will have cutting edges, typically oriented in an opposed manner. The cutting blades will usually be formed from a metal, but could also be formed from hard plastics, ceramics, or composites of two or more materials, which can be honed or otherwise formed into the desired cutting edge. In the exemplary embodiments, the cutting blades are formed as coaxial tubular blades with the cutting edges defined in aligned apertures therein. It will be appreciated that the present invention is not limited to such preferred cutting blade assemblies, in a variety of other designs, such as the use of wiper blades, scissor blades or the like. Optionally, the cutting edge of either or both the blades may be hardened, e.g., by chrome plating. A preferred chrome plating material is ME-92, available from ME-92 Operations, Inc., which may be applied according to manufacturer's instructions.

Referring now to Figs. 1 and 2, a catheter 10 constructed in accordance with the principles of the present invention comprises a catheter body 12 having a proximal end 14 and a distal end 16. A cutting mechanism 18 comprising an outer blade 20 and an inner blade 22 is attached to the distal end of the catheter body 12. An atraumatic tip 24 is attached to the distal end of the outer cutting blade 20, and a guidewire lumen 25 extends through the entire catheter body, cutting mechanism 18, and terminates in port 25 at the distal tip of tip section 24. A proximal hub 30 is attached to the proximal end of catheter body 12 and comprises a perfusion/aspiration connector 32, a guidewire connector 34, and a slider 36. The slider 36 is attached to the proximal end of an actuator rod 37 which extends from the hub 30 through the lumen of catheter body 12 into the cutting mechanism 18 where it is attached at a proximal end of the inner cutting blade 22. In this way, manual actuation of slider 36 in the direction of arrow 38 moves inner cutting blade 22 in the direction of arrow 40.

The outer cutting blade 20 has an aperture 46 formed in one side thereof, as best seen in Fig. 2A. A cutting edge 47 is formed into a transverse peripheral portion of the aperture 46 and includes a plurality of penetrating points as will be described in more detail hereinafter. A second aperture 48 is formed in the side of the inner cutting blade 22, where aperture 48 includes a cutting edge formed in a transverse peripheral region thereof which is opposed to the cutting edge 47 of aperture 46. In this way, the cutting edges 47 and 49 of apertures 46 and 48 and blades 20 and 22 will be drawn past each other when the slider 36 (Fig. 1) is drawn in the proximal direction of arrow 38 to translate rod 37. In a preferred aspect of the present invention, the inner cutting blade 22 is an axially split tubular member which is sized (in its unbiased state) to have an outer diameter slightly larger than the inner diameter of tubular cutting blade 20 (Fig. 2B). Thus, when the inner blade 22 is disposed within the interior of outer blade 20, the outer surface of blade 22 will be slightly constrained and have its outer surface spring-biased against the inner surface of blade 20. In this way, close contact between the blades is assured and shearing between the cutting edges 47 and 49 is enhanced. The cutting mechanism at the distal end of catheter 10 will include a further mechanism for urging it in a radial direction aligned with the apertures 46 and 48. In particular, a pair of resilient ski members 50 may be provided on the side of the outer blade 20 which is opposite to that of the apertures 46 and 47. As described in more detail later in connection with Figs. 5A-5C, the mechanism 50 may be passive or active.

Referring now to Figs. 3A-3E, actuation of the 47 and 49 of blades 20 and 22 will be described in more detail. Initially, before a cut is commenced, the inner blade 20 will usually be distally retracted so that cutting edge 49 lies outside of the aperture 46, as illustrated in Fig. 3 A. The cutting edges 47 and 49 are preferably honed (i.e., sharpened or otherwise formed to sharp cutting edges) with one flat surface and one chamfered surface. The blades are disposed so that the flat surfaces of the cutting edges 47 and 49 slide past each other as the blades are actuated, as illustrated in Fig. 2C. The inner cutting blade 22 is then advanced proximally using rod 37 so that cutting edge 49 enters into the aperture 46, as illustrated in Fig. 3B. Each of the cutting edges 47 and 49 includes penetrating points 60 which are axially aligned so that they will meet when the inner cutting blade 22 is sufficiently retracted in the distal direction, as shown in Fig. 3C. After initially meeting, as shown in Fig. 3C, penetrating points 60 and remainder of the cutting edges 47 and 49 will pass each other in a shearing action, as shown in Fig. 3D. The cutting edges 47 and 49 and penetrating points 60 thus define a plurality of peripherally constrained excision regions 70, where material to be removed is trapped and efficiently excised from the luminal wall. As illustrated in Fig. 3E, the arcuate cutting edges between adjacent penetrating points 60 meet at an angle α which varies as the blades pass each other.

The constrained excision regions defined by cutting edges 47 and 49 are beneficial since portions of the atheroma or other material to be removed will be captured in the constrained excision regions 70 while the opposed edges cross and excise in the direction of arrows 71 in Fig. 3E. Other configurations of the cutting blades, however, will be possible. For example, opposed blades 20' and 22' (Fig. 3F) have straight, transversely aligned cutting edges 47' and 49'; respectively. Spike-like penetrating points 60' are disposed on each of the edges 47' and 49'. The penetrating points 60' will be very effective in penetrating and immobilizing tissue between the blades, but cutting may be less efficient since the material will be sheared all at once as the edges 47' and 49' meet. Note that the points 60' on the opposed edges 47' and 49' may be aligned or not, and are shown as being non-aligned.

The manner in which occluding material M is removed from a body lumen BL (usually a blood vessel and more usually an artery), is illustrated in Figs. 4A-4D. Initially, the cutting blades 20 and 22 are aligned so that aperture 46 is fully opened to receive a portion of the material M therein. The transverse urging mechanism 50 helps initially position the aperture 46 to receive a relatively large portion of the material M, as shown in Fig. 4 A. After the portion of material M is initially received within the aperture 46, the inner blade 22 is proximally translated so that penetrating point 60 (one of two, three, or more of such point in this embodiment) penetrates into the material M, as shown in Fig. 4B. Note that embodiment employing only a single penetrating point may also be employed, although they are not generally preferred. The opposed penetrating point(s) 60 thus act to penetrate and capture the portion of the material M to be excised. In the absence of such penetrating points, the material would have a tendency to be extruded from the apertures as the blades 20 and 22 are closed. As the blades are further advanced (Fig. 4C), the material M continues to be excised. As the blades are closed, as shown in Fig. 4D, the material is fully excised and captured within the interior blade assembly and the catheter.

The resilient skis 50 shown in Fig. 1 are schematically illustrated in Fig. 5 A. Each of skis 50 is normally radially extended to its maximum extension, as shown in full line. When constrained by a body lumen or guiding catheter, however, the resilient ski 50 is radially compressed, as shown in broken line in Fig. 5 A. The advantage of such a passive urging mechanism is that it need not be actuated and requires very little supporting mechanism. The ability to use such a passive urging mechanism is greatly facilitated by the cutting blade assembly which acts to penetrate, engage, and capture occluding material with minimum need to urge the cutter mechanism against the material.

If, however, it is desired to provide positive urging, a variety of other mechanisms are possible. Although not illustrated, a balloon mechanism may be employed as disclosed in numerous prior atherectomy catheters. Other mechanical mechanisms are disclosed in Figs. 5B and 5C. In Fig. 5B, one or more resilient skis, similar to those described previously, are fixedly attached at end 82 to the outside of a catheter body. A proximal end of the element 80 is attached to an axially reciprocatable actuator sleeve 84 which extends to the proximal end of the catheter assembly (not shown). Axial advancement and retraction of the sleeve 84 thus acts to positively expand and retract the ski 80, as shown in full line and broken line respectively.

Another alternative urging mechanism is illustrated Fig. 5C. A resilient ski element or membrane 90 is secured to the outside at the side of the catheter opposite to that of a cutting aperture. A wire 92 may be advanced through a tube 94 having a deflected port 96 at its distal end. Thus, the tube 92 may extend out of the port 96 in a direction suitable for radially deploying the ski membrane element 90, as shown in broken line.

Further alternatives to the apparatus of the present invention are illustrated in Figs. 6 and 7. Figs. 6A-6C illustrate a rotary cutter assembly 100 having an outer blade 101 with an axially aligned cutting edge 102, similar to those described previously. Inner cutting blade 104 also has an axially aligned cutting edge 106. Relative rotation of the inner and outer cutting blades 101 and 104 (as shown by the arrows in Fig. 6C) can thus draw the cutting edges 102 and 106 together in a manner which is otherwise fully analogous to that of the axially translatable cutting blades described previously.

Fig. 7 illustrates an inner cutting blade 120 and outer cutting blade 121, each having a plurality of cutting apertures 122 and 123 formed therein. The inner cutting blades 120 and 121 differ in several respects from the cutting blades described previously. First, they have a non-cylindrical cross-section and may thus be deployed in a blood vessel while permitting perfusion thereacross. The cutting apertures 122 also include penetrating points on both axial sides of the aperture. Thus, the cutting mechanism could be actuated in both proximal and distal directions. Thus, a variety of alternatives and modifications of the present invention can be achieved using designs shown in the inner cutting blade 120 of Fig. 7. Referring now to Figs. 8A and 8B, an alternative mechanism for the blade actuator will be described. In previous embodiments, an actuator rod or similar mechanism has been provided to directly translate a blade axially and proximally (or alternatively rotationally), depending on the direction from which the actuator is moved at the proximal end of the catheter. In some instances, however, it will be preferred to provide a spring-biased return mechanism to translate or rotate the blade in one direction. This is particularly useful with axially translated blades where "pushing" of the blade in the proximal direction requires an actuator rod having a relatively high column strength. Conversely, "pulling" of the blade in the proximal direction can be accomplished with a relatively small rod or filament since only tensile strength is required. Thus, the embodiment of Figs. 8 A and 8B includes an outer tubular blade 200 and an inner tubular blade 202. The blades 200 and 202 will be mounted to axially translate relative to each other in a manner analogous to that described for prior embodiments. The inner blade 200 is connected to an elongate actuator member 204 which will extend through the associated catheter body (not shown) to a proximal end thereof. As spring mechanism 210 is mounted on one end of the inner blade 202, preferably at its distal end as illustrated. When the inner blade 202 is advanced fully in the distal direction (as shown in Fig. 8 A), the spring mechanism 210 will be relaxed. By pulling on member 204, the inner blade 202 may be retracted proximally, as illustrated in Fig. 8B. After it is fully retracted, the spring mechanism 210 will be stretched or expanded so that it applies a biasing force on the inner blade 202 in the distal direction relative to the outer blade 200. This spring mechanism 210 will be sufficiently strong, i.e. have a sufficiently high spring constant, so that the biasing force will be able to return the inner blade 202 to the distal position illustrated in Fig. 8 A when force is released from the actuator member 204. Since it is the spring mechanism 210 which returns the blade 202 to the distal position, the actuator member 204 need not have significant column strength.

Referring now to Fig. 9, the present invention will further comprise kits including catheters 300, instructions for use 302, and packages 304. Catheters 300 will generally be described above, and the instruction for use (IFU) 302 will set forth any of the methods described above. Package 304 may be any conventional medical device packaging, including pouches, trays, boxes, tubes, or the like. The instructions for use 302 will usually be printed on a separate piece of paper, but may also be printed in whole or in part on a portion of the packaging 304. Referring now to Figs. 10-12, 13A and 13B, a catheter 400 having alternative cutting mechanisms and urging mechanisms will be described. Catheter 400 comprises a catheter body having an outer tubular member 402 and an inner guidewire tube 404. The outer tubular member or tube 402 will typically be polymeric, more typically being a tubular extrusion made from any of the materials described above. The inner guidewire tube 404 will typically be a polymeric extrusion but in some instances at least a proximal portion could be a hypotube or similar structure. An outer cutting blade 406 is secured to the distal end of the outer tubular member 402 and comprises a generally continuous structure therewith. The outer cutting blade 406 comprises an aperture 408 having three, staggered penetration points 410, 412, and 414 on a proximal edge thereof. The particular staggering of these penetration points will be described in greater detail in connection with Figs. 14A-14D below. A soft conical tip 420 is attached to the distal end of the outer cutting blade 406 and completes the distal terminus of the catheter 400. The guidewire tube 404 have a lumen which is contiguous to a distal guidewire port 422 in the tip 420. The outer tubular member 402 of the catheter body will also enclose a blade drive assembly 430 and a ski drive assembly 440, as discussed in more detail below. A pair of skis 450 and 452 are mounted on the exterior of the first cutter blade 406 and disposed diametrically opposite to the cutting edge of the cutting blade.

An inner cutting blade 460 comprising three penetration points (best illustrated in Figs. 14A-14D) is slidably mounted within the interior of the first cutting blade 406, as best seen in Figs. 13 A and 13B. In its proximally retracted configuration (as shown in Fig. 13 A), the inner cutting blade 460 generally covers the aperture 408 in the outer cutting blade 406. This is the "closed" configuration of the cutter mechanism which will be used for introducing the catheter 400.

The second cutting blade 460 is axially translated within the first cutting blade 406 by a drive cable 462 which is slidably mounted in a drive tube 464. The guide tube 464, in turn, is fixedly attached relative to the outer cutting blade 406. In particular, it is secured to a transition adaptor 466 which is used to secure the outer tubular member 402 to the outer cutting blade 406. A distal end of the cable 462 is secured to the inner cutting blade 460 by a fitting 468. In this way, axial movement of the cable 462 can distally advance the inner cutting blade 460 to a fully open configuration, as illustrated in Fig. 13B. The ski actuation mechanism 440 comprises a wire 470 which is fixed to the transition adaptor 466 and a tube 472 which slides over the cable and is actuated from the proximal end of the catheter. The tube 472 is attached to the proximal ends of the skis 450 and 452, as best illustrated in Fig. 12. Thus, axial translation of the tube 472 will axially translate the free proximal end of both of the skis 450 and 452 simultaneously. In this way, the skis can be moved between their radially collapsed configurations, as shown in Fig. 13A, and their radially expanded configurations, as shown in Fig. 13B.

Referring now to Figs. 14A-14D, the outer cutting blade 406 includes three penetration points 410, 412, and 414, as generally noted above. The inner cutting blade 460 also includes three penetration points 480, 482, and 484. The penetration points on each of the cutting blades are axially aligned in pairs so that point 410 will meet point 480 as the blades 406 and 460 are drawn together. Similarly, point 412 will meet point 482 and point 414 will meet point 484. The penetration points on each of the blades, however, are axially staggered so that the outer point pairs 410/480 and 414/484 are closer together than the middle point pair 412/482. Thus, when the blades are in their fully opened configuration (Fig. 14A), all points 480, 482, and 484 will be fully retracted so that they are not visible through aperture 408. As the blades are drawn closed, as shown in Figs. 14B and 14C, the penetration point pairs 410/480 and 414/484 will first meet, as shown in Fig. 14C. After the blades are further closed, the center points 412/482 will meet as shown in Fig. 14D. It will be appreciated that the points could have been staggered in other patterns. For example, the center points 412/482 could have met first, and it would have also been possible to have the points meet at three different times, with no two points meeting simultaneously. By staggering the positions of the penetration points, advancement of the cutting blades is facilitated since the peak force required is reduced. Such reduction results from the lessening of the tissue surface area being cut at any one point in time, i.e., the cutting will be distributed over a longer time which reduces the peak cutting force required.

While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting the scope of the invention which is defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A catheter comprising: a catheter body having a proximal end and a distal end; a first blade having a cutting edge and a second blade having a cutting edge disposed near the distal end of the catheter body; and an actuator operatively linked to the first and second blades to draw their respective cutting edges together; wherein at least one of the cutting edges has a penetrating point disposed to penetrate and engage material to be removed as the cutting edge is passed through said material.

2. A catheter as in claim 1, wherein the cutting edges of both the first and second blades have penetrating points.

3. A catheter as in claim 2, wherein at least one of the penetrating points on the first cutting blade is aligned with one of the penetrating points on the second cutting blade so that they substantially meet as the cutting edges are drawn together.

4. A catheter as in claim 3, wherein the first cutting blade has at least two penetrating points aligned with two penetrating points on the second blade.

5. A catheter as in claim 4, wherein the first cutting blade has at least three penetrating points aligned with three penetrating points on the second cutting blade.

6. A catheter as in claim 1, wherein the at least one cutting edge has at least two penetrating points which are staggered in the direction of cutting.

7. A catheter as in claim 6, wherein both cutting edges have at least two staggered penetrating points and wherein a first pair of opposed cutting point meet prior to meeting of a second pair of opposed cutting points as the cutting edges are drawn together.

8. A catheter as in claim 7, wherein each cutting edge has at least three penetrating points with a central penetrating point on each cutting edge disposed to meet after two flanking penetrating points on each cutting edge have met.

9. A catheter as in claim 1, wherein the actuator draws the cutting edges of the blades together in an axial direction.

10. A catheter as in claim 9, wherein the actuator comprises a rod having a distal end attached to one of the blades and a proximal end having a slider for manual advancement and retraction of the rod and blade.

11. A catheter as in claim 10, wherein the rod is radially offset in the catheter body and axially aligned with a cutting edge on the blade.

12. A catheter as in claim 1 , wherein the actuator draws the cutting edges of the blades together in a circumferential direction.

13. A catheter as in claim 1, wherein the first blade is fixedly attached to the distal end of the catheter body and the second blade moves within the first blade.

14. A catheter as in claim 13, wherein the first and second blades are arranged as coaxial tubes with side apertures which define the cutting edges.

15. A catheter as in claim 14, wherein the cutting edges are disposed transversely and the actuator translates the second blade axially relative to the first blade.

16. A catheter as in claim 14, wherein the cutting edges as disposed axially and the actuator rotates the second blade relative to the first to draw the cutting blades together circumferentially.

17. A catheter as in claim 1 , wherein the inner blade is spring-biased so that its cutting edge is aligned to shear closely against the cutting edge of the first blade.

18. A catheter as in claim 17, wherein the inner blade is a split tube biased so that its outer surface engages against an inner surface of the outer tubular blade.

19. A catheter as in claim 1 , wherein the catheter body comprises an inner guidewire tube and an outer tubular body disposed coaxially about the guidewire tube.

20. A catheter as in claim 19, wherein the catheter body comprises a soft conical tip attached at its distal end, wherein the guidewire tube has a lumen which is contiguous with a guidewire port at the distal end of the tip.

21. A catheter as in claim 1 , further comprising means for urging the distal end of the catheter body in a transverse direction within a body lumen.

22. A catheter as in claim 21, wherein the urging means comprises at least one resilient ski that projects radially outward from the catheter body.

23. A catheter as in claim 22, wherein the urging means comprises a pair of radially projecting resilient skis which are diametrically opposite to the cutting edge of the cutting blade.

24. A catheter as in claim 21 , wherein the urging means comprises a radially extensible element and an axially translatable element for mechanically extending the element.

25. A catheter as in claim 24, wherein the radially extensible element comprises a resilient ski which is fixedly attached at its distal end to the catheter body and attached at its proximal end to the axially translatable element, wherein axial reciprocation of the translatable element causes bowing of the ski.

26. A catheter as in claim 25, wherein the axially translatable element is radially offset within the catheter body.

27. A catheter as in claim 25, wherein the axially translatable member comprises a tube which is slidably mounted over a fixed cable.

28. A catheter as in claim 24, wherein the radially extensible element comprises a resilient membrane and the axially translatable element is disposed to push outwardly on said membrane.

29. A catheter as in claim 1 , wherein the actuator comprises a biasing element that returns the blades to an initial relative position after they have been moved by the actuator to a second position.

30. An atherectomy catheter comprising: a catheter body having a proximal end, a distal end, and a lumen therethrough; a first tubular blade having an interior and attached to the distal end of the catheter body so that said interior opens into the lumen of the catheter body; a second tubular blade coaxially disposed within the interior of the first tubular blade, wherein the first and second blades each have side aperture defining transverse, opposed cutting edges and wherein each of said cutting edges has at least one penetrating point aligned with a penetrating point on the outer cutting edge; and an actuator disposed at the proximal end of the catheter body for axially translating the second tubular blade with the first tubular blade to cause the penetrating points to penetrate material within the apertures and the cutting edges to shear material within the apertures .

31. An atherectomy catheter as in claim 30, wherein the actuator comprises a rod having a distal end attached to a proximal end of the second tubular blade and a proximal end having a slider for manual advancement and retraction of the rod and blade.

32. An atherectomy catheter as in claim 31 , wherein the rod is attached to a side of the blade having the side aperture therein.

33. An atherectomy catheter as in claim 30, wherein the first cutting blade has at least two penetrating points aligned with two penetrating points on the second blade.

34. An atherectomy catheter as in claim 33, wherein the first cutting blade has at least three penetrating points aligned with three penetrating points on the second cutting blade.

35. A catheter as in claim 30, wherein the at least one cutting edge has at least two penetrating points which are staggered in the direction of cutting.

36. A catheter as in claim 35, wherein both cutting edges have at least two staggered penetrating points and wherein a first pair of opposed cutting points meet prior to meeting of a second pair of opposed cutting points as the cutting edges are drawn together.

37. A catheter as in claim 36, wherein each cutting edge has at least three penetrating parts with a central penetrating point with a central penetrating point on each cutting edge disposed to meet after two flanking penetrating points on each cutting edge have met.

38. An atherectomy catheter as in claim 30, wherein the inner blade is spring-biased so that its cutting edge is aligned to shear closely against the cutting edge of the first blade.

39. An atherectomy catheter as in claim 38 wherein the inner blade is a split tube biased so that its outer surface engages against an inner surface of the outer tubular blade.

40. A catheter as in claim 30, wherein the catheter body comprises an inner guidewire tube and an outer tubular body disposed coaxially about the guidewire tube.

41. A catheter as in claim 40, wherein the catheter body comprises a soft conical tip attached at its distal end, wherein the guidewire tube has a lumen which is contiguous with a guidewire port at the distal end of the tip.

42. An atherectomy catheter as in claim 30, further comprising means for urging the distal end of the catheter body in a transverse direction within a body lumen.

43. An atherectomy catheter as in claim 42, wherein the urging means comprises a resilient ski that projects radially outward from the catheter body.

44. A catheter as in claim 42, wherein the urging means comprises a pair of radially projecting resilient skis which are diametrically opposite to the cutting edge of the cutting blade.

45. An atherectomy catheter as in claim 42, wherein the urging means comprises a radially extensible element and an axially translatable element for mechanically extending the element.

46. An atherectomy catheter as in claim 45, wherein the radially extensible element comprises a resilient ski which is fixedly attached at its distal end to the catheter body and attached at its proximal end to the axially translatable element, wherein axial reciprocation of the translatable element causes bowing of the ski.

47. A catheter as in claim 45, wherein the axially translatable element is radially offset within the catheter body.

48. A catheter as in claim 45, wherein the axially translatable member comprises a tube which is slidably mounted over a fixed wire.

49. An atherectomy catheter as in claim 45, wherein the radially extensible element comprises a resilient membrane and the axially translatable element is disposed to push outwardly on said membrane.

50. An atherectomy catheter as in claim 30, wherein the actuator comprises a biasing element that returns the blades to an initial relative position after they have been moved by the actuator to a second position.

51. A method for excising occlusive material from within a body lumen, said method comprising: disposing a first blade within the body lumen so that a cutting edge of said blade is on one side of a portion of said material; disposing a second blade within the body lumen so that a cutting edge of said blade is on another side of said portion of said material wherein at least one of said blades has a penetrating point thereon; and drawing the blades to first penetrate the penetrating point into said material and thereafter to shear the portion with the cutting edges.

52. A method as in claim 51 , wherein the disposing steps comprises intraluminally advancing the blades on a catheter.

53. A method as in claim 52, wherein the body lumen is blood vessel and the occlusive material is selected from the group consisting of clot, thrombus, atheroma, and plaque.

54. A method as in claim 51 , wherein the drawing step excises an amount of material in the range from 0.005 mg to 5 mg.

55. A method as in claim 51 , wherein the cutting edges of both the first and second blades have penetrating points.

56. A method as in claim 55, wherein at least one of the penetration points on the first cutting blade is aligned with one of the penetrating points on the second cutting blade so that they substantially meet as the cutting edges are drawn together.

57. A method as in claim 56, wherein the first cutting blade has at least two penetrating points aligned with two penetrating points on the second blade.

58. A method as in claim 57, wherein the first cutting blade has at least three penetrating points aligned with three penetrating points on the second cutting blade.

59. A method as in claim 51 , wherein the at least one cutting edge has at least two penetrating points which are staggered in the direction of cutting.

60. A method as in claim 50, wherein both cutting edges have at least two staggered penetrating points and wherein a first pair of opposed cutting points meet prior to meeting of a second pair of opposed cutting points as the cutting edges are drawn together.

61. A method as in claim 60, wherein each cutting edge has at least three penetrating points with a central penetrating point on each cutting edge disposed to meet after two flanking penetrating points on each cutting edge have met.

62. A method as in claim 51, wherein the drawing step comprises translating the blades relative to each other in a direction aligned with an axis of the body lumen.

63. A method as in claim 51 , wherein the drawing step comprises rotating the blades in a circumferential direction relative to each other with respect to an axis of the body lumen.

64. A method as in claim 51, further comprising removing excised material from the body lumen.

65. A method as in claim 51 , wherein the drawing step is repeated a plurality of times to penetrate and shear a plurality of occlusive material portions.

66. A method as in claim 51 , further comprising radially engaging the blades against a target site on the luminal wall.

67. A method as in claim 66, wherein the radially engaging step comprises urging the blades with at least one radially disposed resilient ski.