Atherectomy System and Method of Using the Same

With age a large percentage of the population develops arterial obstructions formed by fats, fibrous material and calcified deposits, resulting in a diminished blood circulation. The disturbance to blood flow that these obstructions cause may induce blood clots which further diminish or block the blood flow. When this process occurs in the coronary arteries it is referred to as a heart attack. Presently such obstructions are circumvented by surgically grafting a bypass or they are treated by a catheter equipped with a balloon which is inserted through the arterial system, over a flexible guide-wire, into the obstruction and then inflated to expand the obstruction's lumen (angioplasty). Problems with this treatment are that it injures the arterial wall and in certain cases it is ineffective. Further, angioplasty creates a rough lumen and does not remove the obstruction material out of the arterial system, therefore in a case of a heart attack, immediate angioplasty carries the risk of dislodging the blood clot and allowing it to move down stream creating additional blockages.

An objective of the present invention is to provide an atherectomy catheter rotatable over a flexible guide-wire, equipped with a rotary coring means at its distal end, that would core and extract the obstruction material, including blood clots if present, create a smooth lumen and not crack the arterial wall. The design of an atherectomy catheter should lend itself to be producable in diameters down to around 1mm (millimeter) and a length of up to a meter to be able to reach and enter small and remote arteries. Preferably, the operation of the atherectomy system would resemble the operation of present catheter systems, so that existing skills of the medical staff can be utilized. These and other objectives of the invention will become apparent from the following discussion and the accompanying drawings.

FIG. 1 generally shows an atherectomy system inserted at the groin area through the arterial system of a patient, into his coronary artery.

FIG. 2 shows a cross sectioned view of an atherectomy system. The middle portion of the atherectomy system is removed due to space limitations on the drawing sheet.

FIG. 3 shows a cross sectioned view of a flexible rotary catheter equipped with a torque limiting clutch between its proximal end portion and distal end portion.

FIG. 4 shows a cross sectioned view of the distal end portion of a flexible rotary catheter over a flexible guide-wire having triple windings. The flexible rotary catheter is formed of an outer helical winding wound over an inner helical winding which includes a radially protruding spiral step. A plastic jacket coats the outer winding.

FIG. 5 is an enlarged cross sectioned view of the distal end of the system shown in FIG. 4.

FIG. 6 shows a cross sectioned view of the distal end of the system shown in FIG. 5.

FIG. 7 shows a cross sectioned view of the distal end portion of the same flexible rotary catheter shown in FIG. 4 over a hydraulically expandable flexible guide-wire, shown in its relaxed, contracted position.

FIG. 8 shows a cross sectioned view of the flexible guide-wire shown in FIG. 7.

FIG. 9 shows a cross sectioned view of the distal end portion of the flexible rotary catheter shown in FIG. 7 over the expandable flexible guide-wire, shown in its energized, expanded position.

FIG. 10 shows a cross sectioned view of the expanded flexible guide-wire shown in FIG. 9.

FIG. 11 shows the distal end portion of an atherectomy system having a rotary coring means in the form of a variable diameter tubular-blade, shown in its contracted position being compressed inside a sleeve.

FIG. 12 shows the distal end of the variable diameter tubular-blade shown in FIG. 11.

FIG. 13 shows a cross sectioned view of the variable diameter tubular-blade shown in FIG. 11 in its relaxed expanded position after it has emerged out of the sleeve. The variable diameter tubular-blade is mounted on a flexible rotary catheter made of plastic with an integral spiral step formed on its inner wall.

FIG. 14 shows the distal end of the variable diameter tubular-blade shown in FIG. 13.

FIG. 15 shows a cross sectioned view of the distal end portion of an atherectomy system with a rotary coring means in the form of a heated tubular-blade, disposed over a flexible guide-wire having distal barrier devices resembling an umbrella mechanism.

FIG. 16 shows a cross sectioned view of the system shown in FIG. 15 along a line 16--16 marked on FIG. 15.

FIG. 17 shows a flexible guide-wire having remotely actuatable distal barrier devices resembling an umbrella mechanism in their closed position.

FIG. 18 shows a cross sectioned view of the flexible guide-wire shown in FIG. 17 along a line 18--18 marked on FIG. 17.

FIG. 19 shows the flexible guide-wire shown in FIG. 17 with the distal barrier devices in their expanded position.

FIG. 20 shows a cross sectioned view of the flexible guide-wire shown in FIG. 19 along a line 20--20 marked on FIG. 19.

FIG. 21 shows a cross sectioned view of an atherectomy system with a flexible sleeve having a remotely actuatable tongue at its distal end.

FIG. 22 shows a cross sectioned view of the tongue shown in FIG. 21.

FIG. 23 shows a cross sectioned view of an inflatable chamber located at the distal end of the flexible sleeve.

FIG. 24 shows a cross sectioned view of the chamber shown in FIG. 23 along a line 24--24 marked on FIG. 23.

FIG. 25 shows a cross sectioned view of an atherectomy system where the rotary coring means utilizes a radiation emitting device.

FIG. 26 shows a cross sectioned view of the system shown in FIG. 25 along a line 26--26 marked on FIG. 25.

FIG. 1 generally shows an atherectomy system 10 inserted at the groin area, through a patient's arterial system into a coronary artery serving the patient's heart 11.

FIG. 2 shows the atherectomy system 10 (similar parts will be indicated by same numbers throughout the FIGURES) for coring ingesting and removing an obstruction 12 from within a patient's vessel 13. As shown in FIG. 2, the atherectomy system comprises several elongated parts in a nested relationship, and their ends shall be referred to as "distal" meaning the end which goes into the vessel and "proximal" meaning the other end. In view of the above, "distal direction" or the term "distally" shall indicate a general direction from the proximal end to the distal end, and "proximal directon" or "proximally" shall refer to an opposite direction.

The atherectomy system comprises:

A flexible guide-wire 14 which is insertable into the vessel. The distal end portion of the flexible guide-wire is shaped as an auger 15, made of a core wire 16 and a wire 17 which is helically wound around the core wire. At the distal tip the core wire is tapered and covered with a shoft spring to form a standard guide-wire's tip 18.

A flexible rotary catheter 21 is rotatably disposed and insertable into the vessel, over the flexible guide-wire.

A rotary coring means in the form of a tubular-blade 22, is located at the distal end of the flexible rotary catheter. The term "rotary coring means" as used herein, means a tubular-blade with at least a part of its front edge being sharp, or a heated blade, or a radiation emitting means such as an optical fiber (or fibers) located at a wall of the flexible rotary catheter carrying laser energy, or other means which core by making a narrow circular cut in an obstruction placed in front of it. The rotary coring means has an outer wall 23 which slidingly and rotatably bears against the arterial wall spreading the contact force on a relatively large area and thereby minimizing the damage to the artery. A rotary coring means is efficient and uses less energy in comparison to other systems which pulverize the mass of the material of the obstruction. To illustrate this point, when a tubular-blade cores and extracts an obstruction with an outside diameter of 3mm, an inside diameter (lumen) of 1mm and a length of 10mm the area that the tubular-blade has to cut through is 94.25 square mm. If a pulverizing blade, for example as shown in U.S. Pat. No. 4,445,509 by Auth, is used to break the same obstruction to particles measuring 0.01mm by 0.01mm by 0.01mm the area that a pulverizing blade would have had to cut through is 37,699 square mm, and this area which is 400 times larger requires a much larger energy input to the blade, thereby substantially increasing the probability of traumatizing the artery.

A rotating inner-wall 24 is formed by the inside surfaces of the rotary coring means and the flexible rotary catheter.

A continuous passage 25 is defined between the rotating inner-wall and the flexible guide-wire, and the relative motion between the inner-wall and the flexible guide-wire mechanically acts on the ingested obstruction material in the continuous passage and enables it to move towards the proximal end of the flexible rotary catheter and make room for additional cored material.

Coupling means at the proximal end of the flexible rotary catheter in the form of a conical seat 27 couples it to rotating means in the form of a motor having a housing 28 and a hollow shaft 29 with a matching tapered end 31 and a seal 32 at its other end through which the proximal end of the flexible guide-wire slidingly and rotatably extends.

Suction can be applied to the flexible rotary catheter through a port 33 which communicates through a groove 34 , defined by the motor's housing, through hole 39 and through the hollow shaft to the proximal end of the continuous passage 25. The suction cooperates with the mechanical action taking place in the continuous passage in proximally moving the cored obstruction material.

FIG. 4, 5 and 6 show a flexible rotary catheter 85 having an inner helical winding 86 with an inverted "L" cross section. The longer vertical part 89 forms a part of the inner-wall of the flexible rotary catheter whereas the horizontal shorter part 88 extends radially into a continuous passage 91 to form the spiral step 88 which mechanically acts on the cored material in the continuous passage pushing it in a proximal direction when the flexible rotary catheter rotates forward ("forward rotation" of a part is defined herein as a clockwise rotation of the part when its proximal end is viewed in a distal direction; "backward rotation" is an opposite rotation). The inner helical winding 86 tends to diametrically expand when the flexible rotary catheter 85 is rotated forward by its proximal end, but this tendency is balanced by an outer helical winding 92, made of a flat ribbon and wound in a counter direction which tends to diametrically contract, acting as a hoop member balancing and restraining the inner winding's diametrical expansion. A jacket 93 made of plastic with a low coefficient of friction coats the outer windings. A tubular blade 22'attached to the distal end of the windings has a smooth outer surface 23'for slidingly bearing against an arterial wall while its sharp edge cores into an obstruction placed in front of it, and coupling means (not shown) is attached to the proximal end of the windings and has a conical seat for engaging the motor's shaft.

The flexible guide-wire 14 shown in FIG. 2 (and is also shown in the embodiments shown in FIGS. 11, 13, 21, 23 and 25) does several things: It is a distal barrier countering distal movement of the obstruction material in the artery before and while it is being cored, it is an anti-rotational device which restrains the cored material from freely rotating around the flexible guide-wire and to the extent that the obstruction material does rotate around the flexible guide-wire this rotation is translated by the auger to proximally urge the cored obstruction material in the continuous passage. In addition when the flexible guide-wire has to be inserted into a tight obstruction the auger can be screwed into the obstruction by rotating the flexble guide-wire backwards.

Further, the auger guides the flexible rotary catheter on the side of its wire 17, taking up the free play between the core wire 16 and the flexible rotary catheter. If instead of an auger a conventional flexible guide-wire, with an outside diameter equal to the auger's outside diameter, was used, it would have made the system less effective and interfere with the ingestion of the cored obstruction material into the continuous passage, as discussed above.

The auger can be modified by varying its helix angle and/or the number of wires coiled around its core wire. FIGS. 4, 5 and 6 show a flexible guide-wire with three wires 35, 36 and 37, attached to a core wire 16. At an extreme case, when the helix angle 38 is zero degrees, the wires 35 , 36 and 37 are parallel to the core wire, and the flexible guide-wire serves as an anti-rotational device but is not effective by itself as a distal barrier or in urging the cored obstruction material into the continuous passage. These functions are increased as the angle 38 is increased. Therefore, a flexible rotary catheter that has means of pushing the cored obstruction material into the continuous passage, like the flexible rotary catheter shown in FIG. 4, may be teamed with flexible guide-wires which function mostly as anti-rotational devices whereas a flexible rotary catheter without such additional means are preferably teamed with a flexible guide-wire having a more pronounced helix angle.

FIGS. 7 to 10 show a flexible guide-wire having anti-rotational longitudinal ridges 97, 98 and 99, mounted onto a hydraulically expandable tube 96. In its relaxed position the tube has a clover leaf shape, harboring the elongated ridges as shown in FIGS. 7 and 8. The elongated tube is made of a non streching material and can be remotely, at its proximal end, inflated and expanded with fluid to become round as shown in FIGS. 9 and 10 thereby radially displacing the elongated ridges engaging into the obstruction material. As the flexible rotary catheter 85 advances and rotates around the flexible guide-wire it cores, ingests and envelopes the obstruction's material. The spiral step 88 utilizes the relative rotation to mechanically push the obstruction material into the continuous passage 91 while the ridges negate the material's rotation, but they allow the material to move proximally in the continuous passage. When expanded the ridges move close to the spiral step providing positive guidance, with minimal deviation, to the advancing flexible rotary catheter.

FIGS. 11 and 12 show the rotary coring means being a variable diameter tubular-blade 41 in its contracted, compressed position as it is inserted into the vessel through a sleeve 42. The variable diameter tubular-blade (which resembles a collet of the type used in mechanical pencils to grip the lead) is made of four flexible leaves 43 which move radially to their relaxed position, shown in FIGS. 13 and 14 when they exit and are no longer compressed by the sleeve. This reduces the size of the initial puncture wound needed to introduce a certain size rotary coring means into an artery and thereby reduces the associated bleeding and other healing problems of the puncture wound. FIG. 13 also illustrates a spiral step 49 formed on the inner-wall of the flexible rotary catheter 50.

FIG. 15 shows a distal end portion of an atherectomy system having a rotary coring means in the form of a heated tubular-blade 44 having a ring shaped heating element 45 to which energy is brought by means of two flexible conduits 46 and 47 embedded in a wall of a flexible rotary catheter 48 (cross hatching omitted). The heating can be done electrically, in which case the conduits 46 and 47 are electrical wires and the heating element can be a resistive element, or the heating can be done with laser energy in which case the conduits 46 and 47 can be optical fibers and the heating element can serve to absorb the laser energy from the distal end of the optical fibers translating it to heat and distributing it to the tubular-blade 44.

FIG. 15 further shows a flexible guide-wire which has a distal barrier means in the form of umbrella elements 56 to counter distal movement of surrounding obstruction material. The elements 56 can be made of thin plastic tube sections and have a distal collar 57 affixed to the core wire 16 and a proximal collar 58 slidable on the core wire. These collars are connected to a slit collar 59 which, in its relaxed position is open as the most distal umbrella element shown in FIG. 15 is illustrated, but the umbrella element can be closed to the configuration of the adjacent umbrella element 56 when it is pushed through a tight obstruction, as illustrated, in order to reopen when the umbrella element passes the obstruction, forming a distal barrier and preventing the obstruction material from moving distally in the vessel and in the continuous passage while the flexible rotary catheter cores and ingests the obstruction material. During the opening action the collar 58 moves towards the collar 57 and the arms 61 of the slit collar fold and expand out radially (like the action of an umbrella's mechanism) as shown in FIG. 16.

FIG. 17 to 20 show remotely controlled distal barrier means formed by making several slits as shown, in a thin tube 60 thereby forming umbrella elements 56'as an integral part of the thin tube. The distal end to the thin tube is bonded to the distal end of a core wire 16. The distal barrier means can be remotely expanded, as shown in FIGS. 19 and 20, and contracted, as shown in FIGS. 17 and 18, by pushing and pulling, respectively, the proximal end of the thin tube 60 while holding the proximal and of the core wire fixed in place.

FIGS. 21 and 22 show an atherectomy system where a flexible sleeve 76 has a tongue 77 which can be used when coring an eccentric obstruction 95. In such cases the tongue can be inserted opposite of the obstruction 95 to protect an arterial wall 78 and bias the rotary coring means into the obstruction. To further bias the flexible sleeve and the rotary coring means the tongue can be energized against the arterial wall by tensioning a flexible rope 79, moving the tongue from its relaxed position shown in a phantom line in FIG. 14 and marked 77'to the position shown in solid lines and marked 77.

FIG. 23 and 24 show an alternative biasing means in the form of an asymmetrical inflatable chamber 81 formed at the distal end of a flexible sleeve 82 which, when inflated through a channel 83 formed in the sleeve's wall, bears against the vessel's wall, as shown in solid lines, eccentrically biasing the flexible sleeve and the rotary coring means. When deflated, as shown in phantom lines, it wraps the sleeve to minimize interference with its insertion into the vessel.

FIGS. 25 and 26 show an atherectomy system having a flexible rotary catheter 51 where the rotary coring means is a radiation emitting device in the form of an optical fiber (or fibers) 52 which emits laser energy through a lens 53 aligned with the distal end of the fiber. The laser energy cores the obstruction by cutting a narrow channel in it and the continuous passage 63 ingests the cored obstruction material as in previous embodiments. Similarly to the tubular-blade, the laser based rotary coring means is efficient and uses less energy in comparison to other laser based systems which pulverize the mass of the material of the obstruction. Using the same hypothetical obstruction which was used in the previous numerical example (having an outside diameter of 3mm, an inside diameter of 1mm and a length of 10mm) with the system shown in FIG. 25, when laser energy is used to make a 0.1mm wide circular cut in it, it has to disintegrate 9.42 cubic mm of material which is 15% of the obstruction's volume.

Torque generated by the motor is partially dissipated by frictional losses along the flexible rotary catheter, therefore, the flexible rotary catheter can be manufactured with a variable cross section, for example, an increased outside diameter and or/wall thickness at the vicinity of its proximal end compared with the same at its distal end, as shown in FIG. 2. This gives the flexible rotary catheter an increased torque carrying capacity in the vicinity of its proximal end. Such a design is useful when treating small arteries in the heart or brain while entering the arterial system at the groin area as shown in FIG. 1, which requires a long flexible rotary catheter having a distal end portion as small as 1 mm. As shown in FIG. 3 the flexible rotary catheter 65 can be equipped with a torque limiting clutch 66 between the proximal and distal sections, 67 and 68 , respectively, of the flexible rotary catheter. The clutch is made by press fitting the section 68 into section 67 to establish frictional engagement between the two which limits the torque capacity of the clutch 66 to a certain permissible value, thereby protecting the smaller distal end from damage by occasional transfer of higher torques that may be applied at the proximal end. A lock-ring 70 prevents relative longitudinal displacement between sections 67 and 68 while not interfering with their relative rotation.

Referring back to FIG. 2, a flexible sleeve 71 in which the flexible rotary catheter is rotatably disposed protects the arterial wall from the rotating catheter, and can be used to introduce the flexible rotary catheter into the vessel. Means for introducing fluids into the vessel are connected to the flexible sleeve in the form of a nipple 72 leading into an annular chamber 73 which communicates with the sleeve. The annular chamber is equipped with a seal 74 which seals around the flexible rotary catheter and forces fluid entering the nipple 72 to continue and move distally in the sleeve around the flexible rotary catheter.

The atherectomy system can be manufactured in different diameters and lengths depending on the size and site of artery that it is intended for and on whether the system is to be used percutaneously (that is through the skin) or intra-operatively (that is when the vessel is surgically exposed for inserting the system into the vessel).

It can be noted from the FIGURES that the components of the atherectomy system can be modified: The flexible rotary catheter can be made from plastic or metal, it can be equipped with a spiral step and the rotary coring means can vary. The flexible guide-wire can be equipped with anti-rotational means, a distal barrier or an auger and by combining a specific flexible rotary catheter and flexible guide-wire a variety of species can be made. This gives the user a choice of matching the system's characteristics with the clinical condition that is to be treated. The clinical characteristics of atherosclerotic disease vary with the size, geometry and location of the artery as well as with the morphology and chemistry of the obstruction.

A process for removing an obstruction from a vessel with an atherectomy system, comprises the following steps:

Conventionally inserting into a vessel, into an obstruction, a flexible guide-wire. In case of a tight obstruction, an auger shaped flexible guide-wire can be rotated backwards so that the auger section will screw and pull itself through the obstruction.

Advancing over the flexible guide-wire a rotary coring means located at a distal end of an atherectomy catheter.

Advancing the rotary coring means to the obstruction and coring the obstruction. During the operation the flexible guide-wire and the flexible sleeve (if present) are prevented from being rotationally dragged by the rotary coring means. Fluid can be delivered to the obstruction site through the flexible sleeve, around the atherectomy catheter. Such fluid can lubricate and cool the coring process and provide a medium for flushing particles of obstruction material into the atherectomy catheter, especially in conjunction with suction applied to the proximal end of the atherectomy catheter. The fluid may be radio-opaque to assist x-raying the process. Prior to coring, fluid can also be delivered through the atherectomy catheter. A mechanical action of the rotary coring means and the flexible guide-wire on the cored obstruction material due to the relative motion between them enables the cored material into a continuous passage defined in the atherectomy catheter and around the flexible guide-wire.

Removing the catheter containing the obstruction material out of the vessel.

The sequence of insertion of the components into the artery may vary depending on the nature and the location of the obstruction and the preferences of the medical staff. Additional steps may be added to assist the process. A standard guiding catheter, which is either straight or pre-formed, may function as a sleeve and be inserted into the vessel to assist in placing the flexible-guide-wire and the atherectomy catheter in the obstruction site.

When an arterial obstruction is further blocked by a fresh blood clot, as is often the case in a heart attack, the flexible guide-wire can usually be inserted through the clot and the atherectomy system can be used to first clear the clot, preferably while employing suction, and then to continue and core the underlying atherosclorotic obstruction. Therefore, the atherectomy system can be an effective tool in treating a heart attack, where the treatment will relieve the immediate threat to the patient's life and continue to provide a long term correction to the condition that induced the attack.

Differing strategies can be employed when dealing with the process of opening an arterial obstruction. A rotary coring means having an opening approximately equal in area to the artery's internal area can be chosen, however this raises the probability of injuring the artery or of leaving a thin layer of obstruction material hanging on the arterial wall. Such a thin layer which has no structural integrity of its own may separate from the arterial wall and act as a flap of a one way valve which may block the artery. An alternative strategy is to choose a rotary coring means with an area of less than three quarters of the area of the arterial lumen. Coring the obstruction with such a rotary coring means usually relieves the patient's symptoms and it leaves sufficient material for the obstruction to remain structurally stable, reducing the likelihood of creating a flap, and, by using an undersized rotary coring means the probability of injuring the arterial wall is also reduced, even when dealing with an eccentric obstruction. After the obstruction is cored it is also possible to further increase the lumen by angioplasty, however, this will introduce some of the undesirable side effects that are associated with angioplasty, and the choice of strategy will depend on the patient's specific disease characteristics and the judgement of the medical staff.

While the present invention has been illustrated by a limited number of embodiments, it should be understood that various modifications and substitutions may be made without departing from the spirit of the invention or the scope of the claims.