Expandable atherectomy cutter with flexibly bowed blades

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FIELD OF THE INVENTION

This invention relates generally to atherectomy cutter devices. More particularly, this invention relates to a rotating atherectomy cutter which permits controllable expansion of its cutting action while in operation. This invention is particularly, but not exclusively, useful for atherectomy procedures wherein it is desirable to cut an opening through obstructive tissue in the lumen of a body vessel that is larger than the maximum normal cross-sectional area of the atherectomy device itself.

BACKGROUND OF THE INVENTION

Various means and procedures have been developed in recent years to clear or open occluded arteries and other body vessels in order to restore the necessary circulation of blood through the body. In many situations, such intravessel procedures are preferable to "by-pass" operations in which the affected vessel is effectively shunted because intravessel procedures can be relatively quickly performed and do not require an incision into the chest cavity or some other part of the body. Consequently, various procedures and several different devices for performing these procedures have been developed.

In general, there are three ways to eliminate or ameliorate the difficulties caused by an occlusion in an artery. First, it may be possible to dissolve the obstructive tissue causing the occlusion by the ingestion or injection of properly selected medicaments. Such treatment, however, may be ineffective due to an excessive time for response or undesirable due to adverse side effects. Second, well known angioplasty procedures may be used. With the angioplasty procedures, however, the obstructive tissue causing the occlusion remains in situ after the procedure is performed. Thus, the problem may be compromised but it is not eliminated and there remains the real probability there will be a restenosis. Third, atherectomy related procedures may be performed.

In any atherectomy procedure, the obstructive tissue causing the occlusion in the vessel (or at least a part of this obstructive tissue) is cut or clipped from the lumen of the vessel. As should be readily apparent, the instruments used for this purpose require specifically designed cutting devices. Further, the devices which are used for controlling the position of the cutting device in the lumen require special fabrication and design considerations. Specifically, both the cutting device itself and whatever control elements are inserted into the vessel with the cutting device must be miniaturized.

Several atherectomy related devices have been previously disclosed. Exemplary of such devices is Husted U.S. Pat. No. 4,754,755 which discloses a catheter with a cylindrical rotary blade that is used to clear arterial obstructions. As another example of an atherectomy device, Shiber U.S. Pat. No. 4,732,154 discloses a rotary catheter system for this same purpose. For each of the devices disclosed in these references, however, the effective cutting area of the blade of the device is limited. This is so because, in these typical devices, the cutting action of the rotating blade is not capable of extending beyond the periphery of the tubular structure which is used to introduce the blade into the vessel. Consequently, the effective cutting area of the blade is limited by the size of the support structure and this support structure, in turn, is limited to the maximum permissible size of the opening that can be used for an entry site. It often happens, however, that the maximum permissible size of the opening for an entry site is smaller than the cross-sectional area of the vessel lumen at the location where the atherectomy cutter is to be operated. Thus, there is a need for an expandable cutter.

The present invention recognizes the need for an atherectomy cutter which can be expanded, once it is positioned within the lumen of a body vessel, to increase the cutting effectiveness of the device. Further, the present invention recognizes the need for a cutter which can have its cutting action expanded through an infinite variety of diameters between given upper and lower limits while the blades are rotating.

In light of the above, it is an object of the present invention to provide a cutter for an atherectomy device which can be expanded once it is inside the lumen of a body vessel. Another object of the present invention is to provide an atherectomy device which can be adjustably expanded to an infinite variety of settings between upper and lower limits as required to excise obstructive tissue from inside the lumen of a body vessel. Still another object of the present invention is to provide an atherectomy device which can be effectively controlled during the cutting of obstructive tissue from the inside of a body vessel. Yet another object of the present invention is to provide an atherectomy device which is easy to use, relatively easy to manufacture and comparatively cost effective.

SUMMARY OF THE INVENTION

A preferred embodiment of the expandable atherectomy cutting device comprises a flexible blade having a first end connected to a tip and a second end connected to a torque tube, the tip and torque tube being coupled for combined rotation about a guide wire. A controlling drive mechanism is attached to the torque tube for rotating the flexible blade about the guide wire. Associated with the tip and torque tube is a mechanism for urging the tip toward the torque tube to cause the flexible blade to bow outwardly away from the guide wire to provide an expanded cutting path. The tip itself is urged by the flexible blade toward and into a first position where the blade defines a first radius of cutting action. The mechanism for pulling the tip away from the first position and toward the torque tube includes a base rotatably mounted in slidable relation with the torque tube. Desmodromic filaments are connected between the base and the tip for pulling the tip toward and into a second position in which the blade defines a second radius of cutting action greater than the first radius of cutting action.

Also included is a suction mechanism for removing unwanted debris. The cutting device of the present invention can be inserted into a desired body vessel while the device is configured with its first radius and moved through the vessel to the desired site of operation. After being positioned at the desired site of operation, the cutting device can then be controllably expanded into the configuration with its larger second radius for cutting obstructive tissue from the lumen of the vessel as desired.

The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the expandable atherectomy cutting device of the present invention in its intended environment;

FIG. 2 is a side view of the expandable atherectomy cutting device of the present invention;

FIG. 3 is a cross-sectional view taken along line 3--3 of the expandable atherectomy cutting device shown in FIG. 2; and

FIG. 4 is a schematic illustration of the expandable atherectomy cutting device moving between a first position and a second position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1 there is shown an expandable atherectomy cutting device, generally designated 10, in its intended environment. The cutting device 10 is shown inserted into the lumen 12 of a vessel 14. On the inner wall 16 of vessel 14 is a lesion 18 (i.e. obstructive tissue) which is an unwanted volume of material that has attached to the inner wall 16 of vessel 14. For purposes of the present invention, vessel 14 may be an artery or any other lumen from which it is necessary to cut away an unwanted volume of material. For example, lesion 18 may be plaque or some other substance which has created an occlusion in the lumen of an artery. Further, lesion 18 may be a growth, or some other similar occluding obstruction which needs to be removed from the inner wall 16 of vessel 14.

Regardless of the type of vessel 14, or the type of lesion 18, it is desired that some or all of the lesion 18 be cut away by cutting device 10. This is accomplished by cutting device 10 substantially as follows. First a guide wire 20 is inserted into lumen 12 of vessel 14 by a procedure well known in the pertinent art. Cutting device 10 is then positioned over guide wire 20 and is slidingly moved along the guide wire 20 until device 10 is urged into contact with lesion 18. The rotating blades 22 of device 10 are driven via a torque tube element 24 which is operatively engaged to a control element 26. Control element 26 is coupled to a drive mechanism 28 which imparts a force on torque tube 24 which rotates the blades 22 about the guide wire 20. Also coupled to control element 26 is a suction mechanism 30 for removing unwanted material which has been cut away from lesion 18 in a manner which will be further described below.

Referring now to FIG. 2, there are shown the detailed components of cutting device 10. In particular, device 10 comprises a tip 32 which is rotatably positioned about guide wire 20. Tip 32 is the leading edge of cutting device 10 and preferably has a generally tapered front surface 34 to ease movement of the cutting device through the vessel 14 along guide wire 20. In the preferred embodiment, the tip 32 has a circular cross section. Also rotatably positioned about the guide wire 20 is the torque tube 24 which is hollow and generally cylindrical in shape. Preferably, torque tube 24 has the same outer diameter as that of tip 32. Connected between tip 32 and the distal end of torque tube 24 is a plurality of flexible blades 22 of a suitable material and thickness for cutting away unwanted tissue. In