Atherectomy devices and methods

The devices and methods generally relate to treatment of occluded body lumens. In particular, the present devices and method relate to removal of the occluding material from the blood vessels as well as other body lumens.

FIELD OF THE INVENTION

The devices and methods described below generally relate to treatment of occluded body lumens. In particular, the present devices and method relate to improved devices for removal of the occluding material from the blood vessels as well as other body lumens.

BACKGROUND OF THE INVENTION

Atherosclerosis is a progressive disease. In this disease, lesions of the arteries are formed by accumulation of plaque and neointimal hyperplasia causing an obstruction of blood flow. Often plaque is friable and may dislodge naturally or during an endovascular procedure, leading to embolization of a downstream vessel.

Endovascular clearing procedures to reduce or remove the obstructions to restore luminal diameter allows for increased blood flow to normal levels are well known. Removing the plaque has the effect of removing diseased tissue and helps to reverse the disease. Maintaining luminal diameter for a period of time (several to many weeks) allows remodeling of the vessel from the previous pathological state to a more normal state. Finally, it is the goal of an endovascular therapy to prevent short term complications such as embolization or perforation of the vessel and long term complications such as ischemia from thrombosis or restenosis.

Various treatment modalities may help to accomplish treatment goals. In atherectomy, plaque is cut away, or excised. Various configurations are used including a rotating cylindrical shaver or a fluted cutter. The devices may include shielding by a housing for safety. The devices may also remove debris via trapping the debris in the catheter, in a downstream filter, or aspirating the debris. In some cases a burr may be used instead of a cutter, particularly to grind heavily calcified lesions into very small particle sizes. Aspiration may also be used with a burr-type atherectomy device.

Balloon angioplasty is another type of endovascular procedure. Balloon angioplasty expands and opens the artery by both displacing the plaque and compressing it. Balloon angioplasty is known to cause barotrauma to the vessel from the high pressures required to compress the plaque. This trauma leads to an unacceptably high rate of restenosis. Furthermore, this procedure may not be efficient for treatment of elastic-type plaque tissue, where such tissue can spring back to occlude the lumen.

When clearing such obstructions it is desirable to protect the vessel wall or wall of the body lumen being cleared and to debulk substantially all of a lesion. In additional cases, the procedure that clears obstructions may also be coupled with placement of an implant within the lumen. For example, it may be desirable to deploy a stent to maintain patency of a vessel for a period of time and/or to achieve local drug delivery by having the stent elute a drug or other bioactive substance.

On their own, stents fail to perform well in the peripheral vasculature for a variety of reasons. A stent with the necessary structural integrity to supply sufficient radial force to reopen the artery often does not perform well in the harsh mechanical environment of the peripheral vasculature. For example, the peripheral vasculature encounters a significant amount of compression, torsion, extension, and bending. Such an environment may lead to stent failure (strut cracking, stent crushing, etc.) that eventually compromises the ability of the stent to maintain lumen diameter over the long-term. On the other hand, a stent that is able to withstand the harsh mechanical aspects of the periphery often will not supply enough radial force to open the vessel satisfactorily. In many cases, medical practitioners desire the ability to combine endovascular clearing procedures with stenting. Such stenting may occur prior to, after, or both before and after the endovascular clearing procedure.

Accordingly, a need remains for devices that allow for improved atherectomy devices that clear materials from body lumens (such as blood vessels) where the device includes features to allow for a safe, efficient and controlled fashion of shaving or grinding material within the body lumen while minimizing procedure times.

SUMMARY OF THE INVENTION

Devices and methods described herein provide debulking devices having improved means of clearing obstructions within body lumens, especially the vasculature. The features of the devices and methods allow for controlled removal of occlusive materials. In some variations, the methods and devices also have features to convey the materials away from the operative site without the need to remove the devices from the body lumen. Additional aspects include controlled rates of tissue removal as well as other safety features to prevent accidental cutting of the lumen wall. Although the devices and methods described herein discuss removal of materials from a blood vessel, in certain cases the devices and methods have applicability in other body lumens as well. It should be noted that the variations and features of the devices described below may be incorporated selectively or in combination with a basic device configuration that includes a flexible body having a cutter, where the cutter includes a housing and a cutter, where the housing and cutter are able to rotate relative to each other. Variations include a cutter that rotates within the housing, a housing that rotates about the cutter, and combinations thereof.

One variation of the device described herein includes a device configured to remove material from body structures. The device may be a vascular device and have the required structure and configuration to navigate tortuous anatomy. Alternatively, the device may be a cutter that has features that are desired when used in other parts of the anatomy.

In any case, such a device may include a catheter body having a proximal end and a distal end, a cutter assembly located at the distal end of the catheter body, the cutter assembly comprising a housing having at least one opening and a cutter having at least one cutting surface configured to rotate relative to the housing, where movement of the cutting surface relative to the vessel removes occlusive material, a rotating shaft extending through the catheter body and coupled to the cutter, the shaft having a proximal end adapted to couple to a first rotating mechanism, and a deflecting member extending along the catheter body, such that the deflection member can cause deflection of the cutter assembly relative to an axis of the catheter.

Devices of the present invention can also include cutting assemblies where the rotating a cutter rotatably located within a housing has a plurality of cutting edges located on both a near cutting portion and a far cutting portion, where the near cutting portion and the far cutting portion are spaced along an axis of the cutter and the far fluted cutting portion has fewer fluted cutting edges than the near fluted cutting portion, where on rotation of the cutter the fluted cutting edges remove material from the body lumen.

In another variation, a rotatable cutter can include a first plurality of cutting edges extending helically along the entire cutter, and a second plurality of cutting edges extending helically only along a portion of the cutter.

The cutters describe herein can be used with housings that have multiple openings along a wall of the housing. Alternatively, or in combination, a front face of the housing can be open. In some variations, the front edge of the open housing can be configured as a forward cutting surface.

Additional variations of the devices described herein can include a tapered, or conical dilation member located at a tip of the housing. The dilation member provides numerous benefits in addition to dilating material towards openings in a housing of a cutting assembly.

Variations of the devices can also include multiple cutting surfaces. For example, the multiple cutting surfaces may cut tangential to a rotational direction of a cutting head, in a forward direction as the cutting assembly moves distally, and/or in a rearward direction as the cutting assembly is withdrawn proximally. The multiple cutting surfaces can be located on a single cutting head, or may be located on a housing of the cutting assembly. In certain variations of the device, a housing of the cutting assembly may be fully open at a distal end to expose a cutting head. Such a design can incorporate additional safety features to prevent excessive damage to vessel walls.

Variations of the deflecting member may include steerable sheaths adapted to deflect in shape. The steerable sheath may be located internally to a catheter body of the device. Accordingly, the catheter body remains stationary while the sheath can rotate to move a cutting head in an arc about the target body passage.

In some variations the steerable sheath may include a deflecting wire extending through a portion of the sheath, such that axial movement of the deflecting wire deflects the sheath. The deflecting wire can be affixed to the cutter assembly, to a portion of the catheter body that extends out of the deflecting sheath, or to other parts of the device as needed.

The deflecting member can also include a pre-shaped mandrel, or tube where such features are slidable within or relative to the device to produce movement of the cutting head relative to an axis of the device. The devices described herein may have any number of features that allow for locking the device after it is articulated. This feature provides a consistent diameter when sweeping or navigating through the anatomy.

As discussed herein, some variations of the devices have the ability to articulate. This articulation allows for steering the device to the target site as well as creating a sweeping motion of tissue removal. Accordingly, a deflectable sheath used in the device can be rotatable about the catheter body, or about an axis of the catheter.

The devices described herein may have a cutter assembly having a portion of its housing having a curved surface and where the opening forms a plane across the curved surface such that as the cutting surface rotates across the opening, a portion of the cutting surface extends out of the housing through the opening. The cutter assembly may also have various other features as described below that improve the safety of the device as it is articulated while cutting. Furthermore the cutter may have a number of features to impel or drive cut tissue into the cutter assembly for eventual removal by one or more conveying members.

As noted, the devices described herein may have one or more conveying members that convey materials and/or fluids through the device. Such a feature is useful to remove cut tissue and debris from the site during the procedure. In some variations, the device may include multiple conveyors to deliver fluids and remove debris. However, the devices of the present invention may also have containers for use in capturing debris or other materials generated during the procedure.

Another feature for use with the inventions herein is the use of a grinding burr rotatably coupled to a tip of the device. The burr can be useful to remove tissue that is otherwise not conducive to cutting with the cutter assembly.

In another variation, the invention may comprise a device having a straightening tube, with a straight distal portion, a catheter body having a proximal end and a distal end, the catheter body having a flexible section located towards the distal end, such that when located in the straight distal portion of the straightening tube the flexible section is less curved, a cutter assembly located at the distal end of the catheter body, the cutter assembly comprising a housing having at least one opening and a cutter having at least one cutting surface configured to rotate relative to the housing, where movement of the cutting surface removes material, and a rotating shaft extending through the catheter body and coupled to the cutter, the torque shaft having a proximal end adapted to couple to a first rotating mechanism.

In such a case, placement of the straight distal portion over the catheter allows for manipulation of the degree of curvature of the catheter. This feature allows for steering of the device.

As described herein, such a device may have the ability to sweep over an arc to deliver a larger cutting diameter than the diameter of the cutter assembly.

The devices described herein may use a guidewire for advancement through the body. In such cases the devices will have guide-wire lumens located within or about the catheter. Alternatively, a guide-wire section may be affixed to a portion of the device.

Devices of the present invention typically include a torque shaft to deliver rotational movement to components in the cutter assembly. Alternatively, a torque shaft or other such assembly may be used to produce the sweeping action described herein. In any case, the torque shaft may include one or more lumens. Alternatively, the torque shaft may be a solid or hollow member. Variations of the torque shaft also include those aspects known in catheter-type devices such as counter-wound coils, stiffening members, etc. In some variations, the torque shaft may have the conveying member integrally formed about the exterior or an interior surface of the shaft. Alternatively, or in combination, the conveying member may be placed on (or within) the torque shaft as described herein.

The invention also includes various methods of debulking material within body structures. These structures include occluded blood vessels (whether partially or totally occluded), various organs, cavities within the body, or other body lumens.

In one variation a method includes inserting a catheter body having a cutter assembly within the blood vessel, rotating the cutter assembly to remove the material and form a first opening in the body lumen, deflecting the first cutter assembly relative to an axis of the catheter body, rotating the deflected catheter tip while rotating the cutter assembly to form a second opening in the body lumen where the second is larger than the first opening.

The methods may include the use of any of the devices or features of the devices described herein. For example, the methods may include debulking occlusive material within a totally or partially occluded blood vessel by positioning a guidewire adjacent to the occlusive material in the blood vessel, feeding a debulking device on the guidewire to the occlusive material, the debulking device having a cutter, where the cutter includes a housing having a plurality of openings located about the housing and containing a rotatable cutter configured to cut the occlusive material through the openings, where the debulking device further includes a conical dilator tip located at a front of the housing, rotating the rotatable cutter, dilating the occlusive material away from the guidewire and towards an opening in the housing by inserting the conical tip into the occlusive material, and debulking the occlusive material after dilating the occlusive material by cutting the occlusive material with the rotatable cutter through the opening in the housing.

In an additional variation, the methods include circulating fluid for contrast to better visualize the obstruction.

As noted herein, combinations of aspects of the devices, systems, and methods described herein may be combined as needed. Furthermore, combinations of the devices, systems and methods themselves are within the scope of the disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1Aillustrates an exemplary variation of a device100according to the present invention. As shown the device100includes a cutter assembly102affixed to a catheter or catheter body120. The catheter body120can be a reinforced sheath (e.g., a polymeric material with a braid). As shown, the catheter body may be optionally located within an outer sheath122. It is noted that the cutter assembly shown in the figures exemplary purposes only. The scope of this disclosure includes the combination of the various embodiments, where possible, as well as the combination of certain aspects of the various embodiments.

FIG. 1Ashows a variation of a cutter system or debulking device100where the cutter assembly102is within the housing104. The cutter assembly contains a first set of cutting edges112and a second set of cutting edges109, where the first cutting edges112extend along the entire length of the cutting assembly102(i.e., the entire length that is exposed in the openings106of the housing104). In contrast, the second set of cutting edges109(in the figure only one such second cutting edge is visible).

FIG. 1Billustrates an exploded view of the device100ofFIG. 1A. As shown, in this variation the cutter assembly102includes a cutter108is located within a housing104. This cutter108includes a plurality of cutting edges109and112. In this variation, the cutting edges comprise a first set of cutting edges112that extend along (or substantially along) the cutter108and a second cutting edge109that extends only along a portion of the cutter108. Although the number of cutting edges can vary, typically the cutting edges will be symmetric about an axis111of the cutter108. For example, in one variation, the illustrated cutter108will have a pair of second cutting edges109symmetrically located about the cutter108and a pair of first cutting edges112symmetrically located about the axis111of the cutter108. Accordingly, such a construction results in two cutting edges112located on a far or distal end of the cutter108and four cutting edges109and112located on a near or proximal end of the cutter108.

Providing a cutter108with fewer cutting edges on a first cutting portion and an increased number of cutting edges on a second cutting portion, as shown, allows for a more aggressive cutting device. As illustrated in the figures, the cutter can be configured with cutting edges109,112that are adjacent to grooves, channels, or flutes (where the combination is referred to as a “cutting flute”). The flute provides a path for the cut material to egress from the treatment site through the debulking device. By reducing the number of flutes on a far end of the cutter, the flutes can be made deeper. The deeper flutes allow the cutting edge adjacent to the flute to remove greater amounts of material. However, increasing the size of the material can also increase the chances that the material becomes stuck or moves slowly through the catheter during removal. To alleviate this potential problem and increase the efficiency of transporting the material through the catheter, the cutter can be configured with an increased number of cutting edges towards a rear of the cutter that reduce the size of the cut material.

Turning back toFIG. 1B, variations of the debulking device100can also include a cutter assembly102including a housing104with a plurality of openings106in a sidewall of the housing104. However, additional cutter assembly configurations (as noted below) are contemplated. For example, and as noted below, other distinct embodiments of debulking devices a housing can include an opening in a front surface of the housing. In any case, many aspects of either system are combinable where such combinations are not inconsistent.

FIG. 1Balso shows the cutter coupled to a rotating mechanism150. In this variation the rotating mechanism couples to the cutter via a torque shaft114that transmits rotational energy from the rotating mechanism150(e.g., an electric, pneumatic, fluid, gas, or other motor) to the cutter108. Variations of the devices include use of a rotating mechanism150located entirely within the body of the device100. In one variation, the rotating mechanism150may be outside of the surgical field (i.e., in a non-sterile zone) while a portion of the device (e.g., the torque shaft—not shown) extends outside of the surgical field and couples to the rotating mechanism. The rotating mechanism can be a motor drive unit. In one working example, a motor drive unit having 4.5V and capable of producing cutting speeds up to 25K rpm was used.

FIG. 1Balso shows a variation of the device100as having a deflecting member124. In this variation the deflecting member124comprises a curved or curveable sheath/tube that causes deflection of the catheter body122when the sheath124advances distally. In alternate variations, the deflecting member can be a tendon, pull wire, tube, mandrel that causes a distal end of the catheter body to deflect. As described in detail below, the devices100can have deflecting members for articulate the cutting head and allow for a sweeping motion or orbital of cutting around an axis of the body lumen or within a space within the body.

In another variation, the device100can include a catheter body that comprises a soft or flexible portion. In one variation, this soft or flexible portion may be on a single side of the device100to allow flexure of the device100to articulate the cutting head. The flexure may be obtained with the deflecting members discussed above, or other means as known to those skilled in the art. In the illustrated variation, the deflecting member124comprises a sweep sheath. The sweep sheath124has a curved or shaped distal portion, where the curve may be planar or the shaped portion may be a non-planar shape). The distal portion of the sweep sheath is more flexible than a proximal portion of the catheter body. As a result, when the sweep sheath assumes a somewhat straightened shape when in the proximal portion of the catheter body. However, the distal portion of the catheter body is more flexible than the sweep sheath. Accordingly, once the sweep sheath is advanced into the distal portion of the catheter, the catheter assumes the shape or profile of the sweep sheath. This is a way to deflect the cutter assembly off the axis of the catheter. Rotation of the sweep sheath causes the movement of the cutter assembly to sweep in an arc and create an opening larger than a diameter of the catheter itself.

The device100may also include a vacuum source or pump152to assist in evacuation of debris created by operation of the device. Any number of pumps or vacuum sources may be used in combination with the device. For example, a peristaltic pump may be used to drive materials from the device and into a waste container.FIG. 1Balso shows the device100coupled to a fluid source154. As with the rotating mechanism, the vacuum source and/or fluid source may be coupled to the device from outside the surgical field.

It may be advantageous to rotatably couple the torque shaft to the drive unit electromagnetically, without physical contact. For example, the torque shaft114can have magnetic poles installed at the proximal end, within a tubular structure that is attached to the sheath around the torque shaft. The stationary portion of the motor can be built into a handle that surrounds the tubular structure. This allows the continuous aspiration through the sheath without the use of high speed rotating seals.

The device may also include a ferrule116, as shown inFIG. 1B, that permits coupling of the catheter body120to the cutter assembly102. The ferrule116may serve as a bearing surface for rotation of the cutter108within the cutter assembly102. In the illustrated variation, the torque shaft114rotates inside the outer catheter body120and ferrule116to rotate the cutter and pull or aspirate tissue debris in a proximal direction. The clearance between the catheter tube and conveying member118, as well as the pitch and thread depth of the conveying member118, are chosen to provide the desired pumping effectiveness.

In one variation of the device, the housing104is connected to the catheter body120via the ferrule116and thus is static. The cutter108rotates relative to the housing104such that the cutting surface112on the cutter108shears or cleaves tissue and trap the tissue inside the housing104so that it can be evacuated in a proximal direction using the impeller action of the helical flutes and vacuum from the torque shaft. In alternate variations, such as where the housing includes a forward cutting surface, the housing104rotates as well as the cutter. Accordingly, the ferrule can serve as a bearing surface for both the housing and cutter.

The ferrule116can have a distal bearing surface to bear against the proximal surface of the cutter108and keeps the cutter axially stable in the housing104. In cases where the housing is stationary, the ferrule116can be rigidly bonded/linked to the housing104using solder, brazing, welding, adhesives (epoxy), swaging, crimped, press-fit, screwed on, snap-locked or otherwise affixed. As shown, the ferrule116can have holes or other rough features that allow for joining with the catheter body. While adhesives and heat fusing may be employed in the construction, such features are not required. Often adhesives are unreliable for a small surface contact and heat fusing can cause the tube to degrade. The use of a mechanical locking ring126allows the cutting assembly102to be short. Such a feature is important for maximizing the flexibility of the distal section of the catheter as it is required to navigate tortuosity in blood vessels. In one variation, a ring or band (not shown) can be swaged onto the catheter body120and over the ferrule. This drives portions of the ring/band as well as the catheter body into the openings of the ferrule allowing for increased strength between the cutter assembly102and catheter body120.

In another aspect of the invention, devices100can be adapted to steer to remove materials that are located towards a side of the body passage. Such devices may include a deflecting member that permits adjusting the orientation or offset of the cutter assembly102relative to a central axis of the device. InFIG. 1B, the deflecting member comprises a catheter122with a sweep sheath deflecting member132(however, the deflecting member can be a tendon, wire, tube, mandrel, or other such structure.) As described herein, other variations are within the scope of the device.

As shown inFIG. 1C, in certain variations, the housing104can have a distal nose with a center lumen142for receiving a mating piece140of the cutter108. Such features assist in centering the cutter104concentrically inside the housing104. As noted below, variations of the devices include the addition of a burr element (as shown below) for grinding hard tissue such as calcified plaque or a dilator member for separating materials towards the openings106.

The geometry of the cutter108and housing104can be used to tailor the desired degree of cutting. The housing104and orientation of the openings106can be used to limit the depth of cutting by the cutter108. In addition, the distal end of the housing104may be domed shaped while the proximal end may have a cylindrical or other shape. For example, by creating larger windows106in the housing a larger portion of cutter108may be exposed and the rate of cutting increased (for a given rotation speed). By placing the cutting window106on a convex portion or side wall of the housing, the debulking effectiveness is much less sensitive to the alignment of the cutter housing to the lesion, than if the window were on the cylindrical portion of the housing. This is a key performance limitation of traditional directional atherectomy catheters. In addition, placement of the window on the convex portion of the housing creates a secant effect (as described below).

FIG. 1Dillustrates an exploded view of a cutter assembly102and ferrule116. In this variation, the cutter assembly102includes a housing104having three openings106symmetrically placed about a sidewall105of the housing.FIG. 1Dalso shows a variation of cutter108that comprises a far or distal portion90mounted on near or proximal portion92(where the near cutter portion can also be referred to as a cutter core adapter). The near cutter portion94contains a shaft terminating in a mating piece140for coupling the cutter108to the housing104(where the mating piece140nests within an opening in a front face of the housing104. The cutter108can also include a passage96to allow for passing of a guidewire through the device.

Although the inventive device includes cutters formed from in a unitary body, providing the cutter108with far and near90,92cutter portions allows for optimal selection of materials. In addition, as shown, a first cutting edge112can extend along both cutter portions90,92while a secondary cutting edge109extends only along the near cutter portion92. Given this configuration, when the cutter portions90,92join to form the cutter108the far portion90of the cutter only contains two fluted cutting edges while the near cutting portion92includes four fluted cutting edges. Naturally, any number of fluted cutting portions are within the scope of the invention. However, variations include fewer cutting edges on a distal end of the cutter relative to the number of cutting edges on a proximal end of the cutter. Moreover, the cutting edges may or may not be symmetrically located about the cutter.

FIG. 2Aillustrates an additional variation of the device100where the openings106may be helical slots that may or may not be aligned with the cutting edges109,112of the cutter108. For aggressive cutting, the slots106and cutting edges109,112can be aligned to maximize exposure of the tissue to cutting edges. In other words, the cutting edges109,112and openings106can be in alignment so all cutting edges109,112are exposed at the same time to allow simultaneous cutting. Alternatively, alignment of the openings and edges109,112may be configured so that fewer than all the cutting edges109,112are exposed at the same time. For example, the alignment may be such that when one cutting edge is exposed by an opening106, the remaining cutting edges are shielded within the housing104. Variations of such a configuration allow for any number of cutting edges to be exposed at any given time. In addition, the variation depicted inFIG. 2Ashows a window or opening106large enough to expose both the first112and second109cutting edges. However, in alternate variations, the windows can be configured to only expose the cutting edges112on the far end of the cutter108.

In another variation, to even out the torque profile of the device when cutting, the cutter108can be configured such that the number edges/cutting surfaces109,112of the flutes110that are aligned with the housing openings106does not vary throughout the rotational cycle. This prevents the catheter from being overloaded with torque spikes and cyclic torque variations due to multiple cutting edges/flutes engaging with tissue in synchrony. In other words, the length of the cutting surface112exposed through the openings106of the housing104remains the same or constant.

In the variation shown inFIG. 2B, the cutting edges109,112are configured to capture debris within the flute110as the cutter108rotates. Typically, the cutter108may be designed with a secant effect. This effect allows for a positive tissue engagement by the cutter108. As the cutter108rotates through the opening, the cutting edge moves through an arc, where at the peak of the arc the cutting edge slightly protrudes above a plane of the opening. The amount of positive tissue engagement can be controlled through selection of the protrusion distance through appropriate design of the housing geometry (for example, by a combination of location and size of the window and radius of curvature of the housing). The cutting edge109or112can extend out of the housing104through the window106as it rotates. This structure can also be designed to drive or impel the debris to the conveying member118. In this case, the flutes110within the cutter108are helically slotted to remain in fluid communication with the conveying member118. Variations of the device100can also include a vacuum source152fluidly coupled to the conveying member118. In order to improve the impelling force generated by the cutters, variations of the cutter have helical flutes110and sharp cutting edges112that are parallel to each other and are wound from proximal to distal in the same sense as the rotation of the cutter. When the cutter rotates, it becomes an impeller causing tissue debris to move proximally for evacuation.

As shown inFIG. 2C, variations of the device may have cutting edges109,112with positive rake angles α—that is the cutting edge is pointed in the same direction as that of the cutter rotation. This configuration maximizes the effectiveness of the impelling and cutting action (by biting into tissue and avoiding tissue deflection). The cutter is preferably made of hard, wear-resistant material such as hardened tool or stainless steels, Tungsten carbide, cobalt chromium, or titanium alloys with or without wear resistant coatings as described above. However, any material commonly used for similar surgical applications may be employed for the cutter. The outer surfaces of the proximal end of the cutter108are typically blunt and are designed to bear against the housing104. Typically, these surfaces should be parallel to the inner surface of the housing.

FIGS. 2A-2Balso show a surface of the cutter108having a curved-in profile distally and is close to the housing104surface. Note that housing openings106with this curved profile allows the cutting edge112to protrude beyond the housing's outer surface. In other words, the openings106form a secant on the curved surface of the housing104. Such a feature allows improved cutting of harder/stiffer material like calcified or stiff fibrous tissue where such tissue does not protrude into the housing104.

By controlling the number of cutting edges109,112that are exposed through openings106in the housing104, it is possible to control the relative amount of cutting engagement (both length of cutting and depth of cut, together which control the volume of tissue removed per unit rotation of the cutter). These features allow independent control of the maximum torque load imposed on the device100. By carefully selecting the geometry of the flutes and or cutting edges112relative to the openings106in the housing, it is possible to further control the balance of torque. For example, the torque load imposed on the device is caused by the shearing of tissue when the cutter edge is exposed by passing through the housing window. If all cutter edges simultaneously shear, as for example when the number of housing windows is an even multiple of cutter edges, the torque varies cyclically with rotation of the cutter. By adjusting the number of cutters and windows so one is not an even multiple of the other (for example, by using 5 windows on the housing and 4 cutting edges on the cutter), it is possible to have a more uniform torque (tissue removal from shearing action) during each cycle of the cutter.

FIG. 3Ashows a variation of a cutter assembly102where a housing104of the assembly102includes a conical, tapered, or dilator extension133extending from a front face of the housing104. The dilator extension133serves a number of purposes namely that it can keep the cutting assembly102from damaging a vessel wall. In addition, the added structural reinforcement of the front face of the housing104reduces the chance that the rotating cutter108actually cuts through the housing104. However, one important feature of the dilator extension133is that it provides a tapered surface from a guidewire to the openings106in the housing104. Accordingly, as the dilator extension133advances through occlusive material, the dilator extension133forces or dilates material away from a guidewire towards the openings106and cutting edges. In order to dilate material away from a center of the device, the dilator extension133must have sufficient radial strength. In one example, the dilator extension133and housing104can be fabricated from a single piece of material as discussed herein.

The dilator extension133typically includes an opening130for passage of a guidewire. In addition, in most variations, a front end135of the dilator extension133will be rounded to assist in moving the occlusive material over a surface of the dilator133. Furthermore, the surface of the dilator extension133can be smooth to permit sweeping of the cutting assembly102as discussed below. Alternatively, the dilator extension133can have a number of longitudinal grooves to direct material into the openings106. In additional variations, the dilator extension133may not include an opening130. In such a case, the dilator extension133would fully taper to a closed tip.

FIGS. 3B to 3Dconceptually illustrate use of a debulking device having a dilating member133. In this variation, the device100is advanced over a guidewire128. However, use of a guidewire128is optional. As the device100approaches the plaque or occlusive material4, the dilating member133forces the plaque4away from a center of the debulking device100and towards openings106in the cutting assembly102as shown inFIG. 3C. Clearly, the dilating member133must have sufficiently radial strength so that it forces the obstruction towards the openings106. However, in those variations where the dilating member133is conical or tapered, the plaque material4is gradually moved towards the openings106. In those devices not having a dilating member133, the physician must apply excessive force to move the cutter against the plaque4. In some excessive cases, the cutter actually shears through the housing leading to failure of the device.FIG. 3Dillustrates a situation where the debulking device100traverses the entire occlusion4. However, as noted below, the device may be configured for sweeping within the vessel. As such, the physician may choose to sweep the device100within the occlusion to open the occlusion during traversal of the occlusion or after a path is created through the occlusion. In either case, the nature of the dilation member133also functions to keep the cutting assembly102spaced apart from a wall of the vessel2.

FIGS. 4A and 4Bshow an additional variation of a cutting assembly102for use with various debulking devices.FIG. 4Bshows a side view of the cutter assembly102ofFIG. 4A. In this example, the cutting assembly102includes larger windows106to accommodate a cutter108that includes a plurality of directional cutting surfaces112,113,115. As the cutter108rotates within the housing104, the fluted cutting edge112cuts in a direction that is tangential to a rotational direction of the cutter108. In other words, the fluted cutting edges112cut material that is about the perimeter of the cutter108as it spins. The cutter108also includes on or more forward and rearward cutting surfaces113,115. These cutting surfaces113,115engage tissue when the catheter is run in a forward direction or rearward direction. The ability to engage and remove engagements in the multiple directions have been shown to be important for effective debulking. However, a variation of a cutter108in the present invention can include a cutter108with one or two directional cutting surfaces. For example, the fluted cutting edges112can be combined with either the forward113or rearward115cutting surfaces. The ability to debulk in a forward, rearward and rotational directions also reduces the chance that the cutter assembly deflects from stubborn or hard tissue.

FIGS. 5A and 5Bshow another variation of a cutter assembly102having a forward cutting surface113on a front of the cutter108. In this variation, the cutter housing104includes two large openings106that allow the forward cutting surface113to engage tissue when moved in a distal direction. The cutter108also includes a plurality of fluted cutting edges112.

FIGS. 6A and 6Cillustrates another variation of cutter assemblies102where the housing104includes an opening107located on a front face of a cylindrical housing104. The cylindrical housing104containing a cutter108therein. In such a variation, the front edge of the housing104can function as a front or forward cutting surface. As shown, the front cutting surface113can be beveled on an outside surface of the housing104. Such a beveled feature reduces the risk of the cutting surface113from gouging or otherwise damaging the wall of a vessel. As noted above, the forward cutting surface113engages and removes tissue or plaque4when the device is advanced in a distal direction within a body lumen2as shown in below. As discussed herein, features of the device, including a guidewire128assist in preventing the device from excessively cutting the lumen wall2.

The cutter108construction can be similar to that shown above. Namely, where the cutter has a varying number of cutting edges on different portions. Alternatively, the cutter108can be a conventional fluted cutter. In one variation, the cutter108will be tapered or rounded such that the front of the cutter comprises a rounded or partial-ball shape.

The housing104can either be configured to rotate with the cutter108or can be stationary and function as a scraping, scooping, or chisel type surface. For example,FIGS. 6A and 6Bshow a variation where the housing104can be affixed to the cutter108allowing for rotation of the entire cutting assembly102about the catheter body (not shown) or ferrule116. In the illustrated example, the cutting assembly102includes adjoining recessed pin cavities103for securing the housing104to the cutter108.FIG. 6Bshows a cross sectional view of the cutter assembly102ofFIG. 6A. As illustrated, in this particular variation, the entire cutting assembly102rotates relative to the ferrule116which provides a bearing surface for the rotational housing108. The proximal or near portion92of the cutter108rotates within the ferrule while the proximal end of the housing104rotates about the ferrule116.

The housing104can be linked to the cutter108in a variety of ways as is well understood by those skilled in the art. For example the housing104can be directly linked or affixed to the cutter108via connection points103so that both rotate together. Alternatively, the housing104can be geared to rotate faster or slower than the cutter108. In yet another variation, the gearing can be chosen to permit the housing104to rotate in an opposite direction than the cutter108.

Variations of the cutting assemblies include cutters108that protrude partially from the forward cutting surface113of the housing104. In other variations, the cutter108can extend further from the housing104or even cutters108that are totally recessed within the housing108. In certain variations, it was identified that aligning the cutting surface113of the housing104with the deepest part of the flute on the cutter108allows for improved clearing of debris, especially where a single or double fluted cutting edge configuration is used on a distal portion of the cutter.

In any case, the fluted cutting edge112impels tissue debris back into the catheter. The outer diameter of the housing, proximal to the forward cutting surface113can be smooth to protect the lumen wall from the cutting action of the cutting edges. When the cutting assembly102is deflected, the outer diameter of the housing102becomes flush against the lumen wall and prevents the cutting edges from engaging the vessel wall. As the cutter assembly is advanced forward, it removes plaque4protruding from the lumen2wall and tissue debris is impelled backwards by the fluted edge112of the cutter108.

FIGS. 6C and 6Dillustrate a variation of a cutting assembly102where a housing104of the cutting assembly102remains stationary about a catheter body (not shown) or ferrule116while the cutter108rotates within the ferrule.

FIG. 6Dillustrates a partial cross sectional view of the cutting assembly102ofFIG. 6Cwhere the inner portion of the ferrule116provides a bearing surface for the proximal end92of the cutter108. The housing104is affixed to the ferrule116and may also function as a bearing surface for the rotating cutter108.

FIG. 6Eshows an exploded view of the cutting assembly ofFIG. 6C. Again, the cutter108can include a distal or far cutting portion90and a proximal or near cutting portion92. The illustrated configuration provides a device having fewer cutting edges112on a distal portion90of the cutter and increased cutting edges109and112on a proximal cutting portion92. However, variations include a traditional fluted cutter as well. The housing104is mounted about the cutter portions90and92and optionally secured to either the catheter body (not shown) or ferrule116. As noted above, the housing104can also be affixed to the cutter so that it rotates with the cutter.

In alternate variations, the cutter assembly102the mating surface140can function as a blunt bumper at the very tip of the cutter108that acts as a buffer to prevent accidental cutting into the guidewire or the vessel wall given the cutter assemblies' open distal design. In additional variations, the housing104could be expandable (such as a basket or mesh). As the cutter108gyrates inside the housing, the housing expands to cut a larger diameter.

FIG. 6Fillustrates a cutting assembly102having a forward cutting surface113at a distal opening117of a housing104. The housing104rotates along with the cutter108to assist in removal of tissue. As noted above, the forward cutting surface113engages and removes tissue or plaque4when the device is advanced in a distal direction within a body lumen2as shown inFIG. 5E. As discussed below, features of the device, including a guidewire128assist in preventing the device from excessively cutting the lumen wall2.

The shielded atherectomy catheters described herein can perform biopsies, tumor removal, fibroid treatment, debulking of unwanted hyperplastic tissues such as enlarged prostate tissue, or other unwanted tissue such as herniated spinal disc material. The flexible, low profile catheter allows for ease of access to the treatment site and minimizes trauma or collateral damage to surrounding healthy tissue. With the continuous aspiration capability, contamination of the surrounding tissue during device introduction, treatment and removal is reduced or even eliminated. In addition, aspiration can be used to transfer biopsy tissue samples to outside the body for testing with the catheter remains in situ. This helps the physician make real time decision in advancing treatment of malignant tissue. The shield on the cutter assembly maintains controlled excision of tissue by limiting the depth of cutter engagement and thereby prevents the physician from inadvertently cutting into healthy surrounding tissue. The tip steering capability of the cutter allows the physician to direct the cutter towards desired site of tissue removal and minimizing collateral tissue damage. Finally, by deflecting the cutter and rotating the deflection to sweep in an arc, the catheter can excise large tumors or tissue lumps larger than the diameter of the catheter. Thus, excision of large tumors can be achieved through a small access channel and thereby minimizing trauma to the patient.

The construction of the cutting assembly can provide for additional modes of energy delivery. For example, the catheter excises tissue in vascularized regions excessive bleeding can occur (e.g., lung biopsy and excision). Accordingly, energy can be delivered to the target site via a conductive cutter assembly (i.e. shield or even cutter). Sound energy (ultrasound), electrical energy (radio frequency current), or even microwaves can be used for this purpose. These energy sources delivered through the cutter can also be used to denature tissue (collagen), shrink tissue, or ablate tissue.

The cutter assembly can be made from a variety of materials. For example, the housing is preferably made of a strong, wear resistant material such as hardened steels, cobalt chromium, carbides or titanium alloys with or without wear resistant coatings like TiNi. In particular the use of coatings will allow the use of tool steels which, unless coated, do not have acceptable corrosion resistance and biocompatibility. The cutter or cutter can be fabricated from steel and can be coated with a titanium nitride. Alternatively, the cutter can be fabricated from a tungsten carbide material.

Coatings can be applied to the moving components in the catheter to reduce friction. In one embodiment, the sheaths and the torque shaft are coating with a hydrophilic coating (polyvinyl alcohol) to reduce friction between the moving components in the catheter. The coatings can also be hydrophobic (e.g. parylene, PTFE). The coatings can be impregnated with heparin to reduce blood clotting on surface during use.

FIG. 7shows a partial sectional view of an example of a torque shaft114that is coupled to a cutter assembly. To aid in removal of materials, the torque shaft can be a set of counter-wound coils, with the outer coil wound at the proper (greater) pitch to form the conveying member118. Winding the coils counter to each other automatically reinforces the torque shaft114during rotation. Alternatively, the torque shaft114may be made out of a rigid plastic, rendered flexible by incorporation of a conveying member118. Although the shaft may be fabricated from any standard material, variations of the shaft include a metal braid embedded in polymer (PEBAX, polyurethane, polyethylene, fluoropolymers, parylene) or one or more metal coils embedded in a polymer such as PEBAX, polyurethane, polyethylene, fluoropolymers or parylene. These constructions maximize torsional strength and stiffness, as well as column strength for “pushability”, and minimize bending stiffness for flexibility. Such features are important for navigation of the catheter through tortuous vessels but allow for smooth transmission of torque over the long length of the catheter. In the multi-coil construction, the inner coil should be wound in the same sense as that of the rotation so that it would tend to open up under torque resistance. This ensures that the guidwire lumen remain patent during rotation. The next coil should be wound opposite the inner to counter the expansion to keep the inner coil from binding up against the outer catheter tube.

FIG. 7also shows a torque shaft114having a central lumen130. Typically the lumen will be used to deliver a guidewire. In such cases, the central lumen may be coated with a lubricious material (such as a hydrophilic coating or Parylene) or made of a lubricious material such as PTFE to avoid binding with the guidewire. However, in some variations a guidewire section is affixed to a distal end of the housing. Moreover, the central lumen of the torque shaft114may also be used to deliver fluids to the operative site simultaneously with the guidewire or in place of the guidewire.

FIG. 8Aillustrates a variation of a device100configured for rapid exchange. As shown, the device100includes a short passage, lumen, or other track136for the purpose of advancing the device100over a guidewire128. However, the track136does not extend along the entire length of the device100. Moreover, an additional portion of the track136may be located at a distal end of the catheter to center a guidewire128.

This feature permits rapid decoupling of the device100and guidewire128by merely holding the guidewire still and pulling or pushing the catheter100over the guidewire. One benefit of such a feature is that the guidewire128may remain close to the site while being decoupled from the device100. Accordingly, the surgeon can advance additional devices over the guidewire and to the site in a rapid fashion. This configuration allows for quick separation of the catheter from the wire and introduction of another catheter over the wire since most of the wire is outside of the catheter.

As shown inFIG. 8B, centering the tip of the cutting assembly102over a guide wire128improves the control, access and positioning of the cutting assembly102relative to a body lumen or vessel2. To accomplish this, the cutting assembly102can have a central lumen to accommodate a guide wire128. Variations of the device100includes a central guide wire lumen runs the length of the catheter through all central components including the torque shaft and the cutter. As noted above, a guidewire128can be affixed to the housing104or other non-rotational component of the cutting assembly102. In such a case, the guidewire128may preferably be a short segment that assists with navigation of the device through an occluded portion of a body lumen. However, the devices100can also operate without a guidewire since the head is steerable like a guidewire.

FIG. 9Aillustrates a partial cross-sectional view of another variation of a device100. As shown, this variation of the device100includes a conveyor member118located within the device100and located on an exterior surface of a torque shaft114. The conveyor member118may be an auger type system or an Archimedes-type screw that conveys the debris and material generated during the procedure away from the operative site. In any case, the conveying member118will have a raised surface or blade that drives materials in a proximal direction away from the operative site. Such materials may be conveyed to a receptacle outside of the body or such materials may be stored within the device100. In one variation, the torque shaft114and conveying member118extend along the length of the catheter.

In some variations, the conveying member118may be integral to the shaft114(such as by cutting the conveying member118into the torque shaft114or by extruding the torque shaft114directly with a helical groove or protrusion. In an additional variation as shown inFIG. 9B, an additional conveying member118may be incorporated on an inside of the torque shaft, where the internal conveying member is wound opposite to that of the external conveying member118. Such a configuration allows for aspiration and debris (via the external conveying member118) and infusion (via the internal conveying member118). Such a dual action can enhance the ability to excise and aspirate plaque by: (1) thinning the blood, whether by viscosity alone or with the addition of anti-coagulants such as heparin or warfarin (cumadin), and/or anti-platetlet drugs such as Clopidegrel, (2) improving the pumpability (aspirability) of the excised plaque by converting it into a solid-liquid slurry that exhibits greater pumping efficiency, and (3) establishing a flow-controlled secondary method of trapping emboli that are not sheared directly into the housing, by establishing a local recirculation zone.

As noted above, the conveying member118can be wound in the same directional sense as the cutter108and in the same direction of rotation to effect aspiration of tissue debris. The impeller action of the cutter108moves the tissue debris from inside the housing104openings106into the torque shaft. The pitch of the cutting edges112may be matched in to that of the conveying member118to further optimize aspiration. Alternatively, the pitch of the conveying member118may be changed to increase the speed at which material moves once it enters the conveying member118. As discussed herein, debris can be evacuated outside the body by the conveying member118action along the length of the catheter and with or without supplement of the vacuum152pump connected to the catheter handle. Alternatively, the debris may be accumulated in a reservoir within the device.

FIG. 10Aillustrates an example of a variation of a device100equipped to have an articulating or steerable cutter assembly102. The ability to steer the tip of the device100is useful under a number of conditions. For example, when debulking an eccentric lesion as shown, the cutting assembly102should be pointed towards the side of the vessel2having the greater amount of stenotic material4. Naturally, this orientation helps prevent cutting into the bare wall/vessel2and focuses the cutting on stenotic tissue4. As shown in when in a curved section of the vessel2, without the ability to steer, the cutting assembly102would tend to bias towards the outside of the curve. Steering allows the cutting assembly102to point inward to avoid accidental cutting of vessel wall2.

The ability to steer the device100also allows for a sweeping motion when cutting occlusive material.FIG. 10Bshows the rotation of the cutting assembly102. As shown inFIG. 10C, when the cutting assembly102deflects relative to the axis of the catheter, rotation of the deflected portion102creates a sweeping motion. It is noted that rotation or articulation of the cutting assembly also includes rotation or articulation of the catheter to allow the cutting assembly to deflect relative to an axis of the catheter.FIG. 10Dshows a front view taken along an axis of the vessel to illustrate the sweeping motion causing the cutting assembly102to “sweep” over a larger region than the diameter of the cutting assembly. In most cases, when articulated, the device will be rotated to sweep over an arc or even a full circle. The rotation of the cutter may or may not be independent of the rotation of the device. A user of the device may couple the sweeping motion of the cutting assembly with axial translation of the catheter for efficient creation of a larger diameter opening over a length of the occluded vessel. The combination of movement can be performed when the device is placed over a guidewire, for example by the use of a lead screw in the proximal handle assembly of the device. In another aspect of the devices described herein, the angle of articulation may be fixed so that the device sweeps in a uniform manner when rotated.

A number of variations to control the deflection of the device100are described herein. For example, as shown inFIG. 1Athe sheath122itself may have a pre-set curve. In such a case, the area of the catheter body120adjacent to the cutting assembly102will be sufficiently flexible so as to assume the shape of the curved sheath122.

FIG. 10Eillustrates another variation where the catheter body120includes a set curve in an area that is adjacent to the cutting assembly102. In this case, the outer sheath122can be made to be straight relative to the catheter body120. Accordingly, advancement of the curved portion of the catheter body120out of the sheath122causes the catheter body120to assume its curved shape. The degree of articulation in such a case may be related to the degree of which the catheter body120is advanced out of the sheath122.

In addition, the shape of the housing104as well as the location of the windows106can be chosen so that when the device100is substantially aligned with the lesion, or engages it at less than some critical attack angle, it will cut effectively. However, when pivoted at an angle greater than the critical angle, the cutting edges or grinding element will not engage the lesion as shown inFIG. 11A. This means that at large deflections, as the catheter tip approaches the vessel wall, it automatically reduces its depth of cut and ultimately will not cut when the critical angle is exceeded. For example, the cutter distal tip is blunt and does not cut. As the catheter tip is deflected outward, the blunt tip contacts the vessel and keeps the cutting edges proximal to the tip from contacting the vessel wall. Also the wire in combination with the device can also act as a buffer to prevent the cutting edges from reaching the vessel.

FIGS. 11B and 11Cshow a cutter assembly design that is specialized for forward cutting. This particular variation includes an open ended housing where the cutter extends from the housing (as shown above). However, a blunt bumper119at the tip of the cutter108acts as a buffer to prevent accidental cutting into the guidewire144or excessively into the lumen wall2. In addition, this design can optionally incorporate a static housing portion121on a back end of the cutter assembly102that partially shields the cutter from deep side cuts into the lumen wall2.

As mentioned above, variations of the device100allow directional control of the cutting assembly102. In those variations where a slidable, torqueable sheath advances relative to the catheter body122(either external or internal to the catheter body) that can be flexed at the distal end. With the sheath flexed the catheter tip is pointed in the direction of the flex and the degree of bias is affected by the amount of flex on the sheath. The sheath can be rotated about the catheter or vessel long axis to change the direction of the cutting assembly. Also as noted above, this rotation can also effect a sweep of the cutting assembly102in an arc or a circle larger than a diameter of the cutter102(e.g. seeFIG. 10D). Such a feature eliminates the need to exchange the device for a separate cutting instrument having a larger cutting head. Not only does such a feature save procedure time, but the device is able to create variable sized openings in body lumens.

As shown inFIG. 12A, the tension on a slidable wire132in the wall of the sheath122can cause flexure of the sheath122. Compression of the wire can also cause flexure of the sheath in the opposite direction. In one variation, the sheath122can be attached to the housing104of the cutting assembly102. Since the housing104is rotatable relative to the cutter108and the torque shaft114, the sheath122can rotate independently of the torque shaft114and cutter108to either sweep the cutting assembly102or to change direction of the articulated cutting assembly102at an independent rate.

In another variation of the device100, as shown inFIG. 12B, a preshaped curved wire or mandrel134can be advanced in a lumen in either the sheath122or catheter120. As the mandrel134advances, the device takes the shape as shown inFIG. 12C.

In yet another variation, the catheter tip and cutting assembly can be articulated in different directions and swept through an arc by having a series of sliding pull wires running through side lumens in the sheath. The pull wires attach to the cutter assembly. By cycling tension on the pull wires sequentially on the proximal control with such mechanism as a cam, the deflected tip can be swept in an arc.

FIGS. 12D to 12Eillustrate a variation of a device100having a pre-shaped sweep sheath for a deflecting member124located in a space between the catheter120and the torque shaft114. In this variation, the catheter120includes a flexible distal portion123and a relatively stiffer proximal portion125. When the sweep sheath124is located within the stiffer proximal portion125of the catheter lumen the sweep sheath124straightens. To articulate the cutter assembly102, the operator advances the sweep sheath124as shown by arrow127such that the sweep sheath124locates within the flexible distal portion123of the catheter120. As a result, and as shown inFIG. 12B, the sweep sheath124causes articulation of the cutter assembly102. The sweep sheath124is rotatable as well as axially moveable within the catheter124. As a result, rotation of the sweep sheath124sweeps the cutter assembly102in an arc as discussed above.

As shown, the catheter body120remains stationary while the inner sweep sheath124rotates to move the cutting assembly102in an arc or orbit within the lumen. The outer catheter120body provides a static linkage between the cutter assembly and the deflection control assembly. The outer sheath is preferably composed of a metal braid sandwiched in a polymeric matrix of such materials as high density polyurethane (HDPE), polyethylene (PE), fluoro-polymer (PTFE), nylon, polyether-block amide (PEBAX), polyurethane, and/or silicone. The sheath is stiffer proximally than distally. This can be achieved by using softer grades of polymers distally and/or having no metal braid distally.

FIGS. 13A and 13Billustrate one variation of a control system or fixture. As shown, the control system200includes a sweep control knob202coupled to a sweep sheath (not illustrated.) The sweep control knob202can slide axially and rotate independently relative to the outer catheter120and the torque shaft (not shown). Again, the sweep sheath can be composed of a metal braid sandwiched in a polymeric matrix of such materials as polyethylene (PE), fluoro-polymer (PTFE), nylon, and/or polyether-block amide (PEBAX), polyurethane, and/or silicone. The sweep sheath can also be made of counter wound metal coils. Its distal end is curved and is preferably made of a material that can withstand high degree of flex and retain its curved shape. Such material may include polymers such as PE, nylon, Polyetheretherketone (PEEK), Nickel Titanium (Nitinol), or spring steel.

To allow the cutter assembly to be straight and undeflected102, the sweep sheath is withdrawn proximally by the sweep control knob202. This causes the curved or shaped section of the sweep sheath to retract within the stiff portion of the outer catheter120. As shown inFIG. 13A, distal movement of the sweep control knob202advances the sweep sheath to deflect the catheter tip. The degree of the deflection is controlled by the amount the sweep sheath is advanced. The more the curve of the sweep sheath protrudes distal to the stiff section of the outer sheath, the more the catheter deflects.

As shown inFIG. 13B, the sweep control knob202can be rotated to sweep the cutting assembly102in an arc manner. Although sweeping of the cutting assembly102can occur via manual operation. Variations of the device include sweep sheaths that can be selectively coupled to a motor to activate an automated rotation. This allows the physician to have a smooth, continuous, automated means to sweep the cutter without any manual effort.

FIGS. 13A and 13Balso show the catheter120as having a flush port129. The flush port129provides a means for injecting a fluid such as heparinized saline or any other medicine into the catheter body120to keep blood and tissue debris from clogging the space between components in the device. The flush port129can also help lubricate moving components within the device. One desirable fluid path is along the length of the catheter in the space between the catheter body120and sweep sheath124. Drugs or fluids can be introduced via the flush port129for flow out of one or more openings131near the catheter tip or cutting assembly102. In some variations, it may be desirable to place a flush opening131at an “elbow” of the catheter body120as shown inFIG. 13C. During use of the catheter the tip is deflected, the “elbow” always contacts the luminal surface. Drugs flushing out this elbow can then infuse into the vessel wall. Using a stenosis-inhibiting drug like paclitaxel or rapamycin could help prevent restenosis after the atherectomy procedure.

Turning now to a variation of the catheter100and control system200, the entire system is arranged from distal to proximal with a cutter assembly102, a catheter body120, a flush port129, a control system200for tip deflection and sweep control, a hub204or other connection for providing aspiration of the cut materials as well as a drive gear206to turn the torque shaft and cutter. The gear206is connected to a rigid drive shaft208encased within the hub204as shown inFIG. 13D. The drive shaft208can take a form of a hollow tube with a central lumen for passage of the guidewire and is centered within a lumen in the hub204and fixed axially by a pair of bearings210. A seal212adjacent to the bearing210prevents aspirated tissue debris from leaking proximally through the bearing210. A transfer propeller212is rigidly attached to the distal portion of the drive shaft208to pump aspirated tissue debris8from the catheter out into an attached aspiration reservoir. The drive shaft208is connected to flexible torque shaft114that extends the length of the catheter body for the purpose of transfer torque from the drive shaft to the cutter. As noted above, the torque shaft114has helical grooves on its outer diameter and central guidewire lumen. During a procedure run, a motor drives the gear206to rotate. This causes rotation of the drive shaft208, the transfer propeller212, the torque shaft114, and the cutter (not shown) all in the same rotational sense. Thus the cutter assembly effectively cuts plaque and drives the debris back into the helical groove on the torque shaft114. The rotating helical grooves winds the debris back into the hub204, which is then transferred to the aspiration reservoir by the transfer propeller212. The propeller212can take the form of a screw or a series of circumferentially arranged angled fan blades. The cutter is preferably rotated at a speed of 10,000-25,000 rpm. An alternative design would have the aspiration reservoir built into the hub of the catheter.

FIGS. 14A to 14Fillustrate additional mechanisms for flexing the device100. Such mechanisms can include side balloons160, meshes, wire loops164, coils166, and arms or mandrels168and other such structures. These features can be incorporated into catheter body120itself or into the sheath122. If located in the catheter body122, the entire catheter can be rotated to steer the tip in different directions. A curved or helical guidewire170can also be used to effect the flexion of the catheter tip as shown inFIGS. 14A to 14F. The wire can also be actively flexed to control the degree of catheter flexion. All of these deflecting mechanisms can cause the catheter to be deflected in one plane or it can be deflected in three dimensions. The curve on the wire can be in one plane or in 3 dimensions. The sheath can be flexed in one plane or 3 dimensions. Another way to achieve flexion at the distal tip of the catheter is to only partially jacket the distal end with one or more polymers. A bevel at the distal end and/or varying combinations of jacketing and polymers can be used to change the position of the moment arm. This changes the flexibility of the distal end and allows proper deflection.

In addition to providing a means for deflecting the catheter, and allowing the user to sweep the distal tip to engage the lesion as desired, it is also possible to link a separate torque control device to manually or automatically control the sweep of the catheter, independent of the axial control of the catheter insertion and the rotation control of the cutter within the housing. Automatic control may be performed open-loop by user entered settings and activating a switch, or with feedback control designed to further optimize cutting effectiveness, procedural efficiency, and safety. Example structures of how to lock the articulation of the sheath/catheter into place include a lockable collar, a stopper, and friction lock detect mechanisms with one or more springs, coils, or hinges.

Additional components may be incorporated into the devices described herein. For example, it can be desirable to incorporate transducers into the distal region of the catheter to characterize the plaque or to assess plaque and wall thickness and vessel diameter for treatment planning; also transducers may be desired to indicate the progression of debulking or proximity of cutter to vessel wall. For example, pressure sensors mounted on the catheter housing can sense the increase in contact force encountered in the event that the housing is pressed against the vessel wall. Temperature sensors can be used to detect vulnerable plaque. Ultrasound transducers can be used to image luminal area, plaque thickness or volume, and wall thickness. Optical coherence tomography can be used to make plaque and wall thickness measurements. Electrodes can be used for sensing the impedance of contacted tissue, which allows discrimination between types of plaque and also vessel wall. Electrodes can also be used to deliver impulses of energy, for example to assess innervation, to either stimulate or inactivate smooth muscle, or to characterize the plaque (composition, thickness, etc.). For example, transient spasm may be introduced to bring the vessel to a smaller diameter easier to debulk, then reversed either electrically or pharmaceutically. Electrical energy may also be delivered to improve the delivery of drugs or biologic agents, by causing the cell membrane to open in response to the electric stimulation (electroporation). One method of characterization by electrical measurement is electrical impedance tomography.

As shown inFIG. 15, a cutter assembly102can also have a burr protruding out its nose. Although the burr180may have any type of abrasive surface, in one variation, this burr is blunt and has fine grit (such as diamond grit) to allow for grinding of heavily calcified tissue without injuring adjacent soft tissue. This combination of a burr and cutter allow the distal assembly to remove hard stenotic tissue (calcified plaque) using the burr while the sharp-edged shaving cutter removes softer tissue such as fibrous, fatty tissue, smooth muscle proliferation, or thrombus. In variations, the burr can also have helical flutes to help with aspiration, or the burr can be incorporated to a portion of the cutting edge (for example, the most distal aspect of the cutter).

Infusing solutions (flush) into the target treatment site may be desirable. Infused cool saline can prevent heating of blood and other tissue, which reduces the possibility of thrombus or other tissue damage. Heparinized saline can also prevent thrombus and thin out the blood to help maximize effectiveness of aspiration. The flush can also include drugs such as Clopidegrel, Rapamycin, Paclitaxel or other restenosis-inhibitors. This may help to prevent restenosis and may result in better long term patency. The flush may include paralytics or long-acting smooth muscle relaxants to prevent acute recoil of the vessel.FIGS. 16A-16Cillustrate variations of flushing out the device100. The flush can be infused through the guide wire lumen (FIG. 16A), a side lumen in the catheter shaft (FIG. 16B) or tube, the space between the flexing sheath and the catheter and/or the sideports in the guidwire (FIG. 16C). Flush can come out of a port at the distal end of the cutter pointing the flush proximally to facility aspiration. Alternatively, by instilling the flush out the distal end of the cutter housing over the rounded surface, the flow may be directed rearward by the Coanda effect. The restenosis-inhibitors can be carried by microcapsules with tissue adhesives or vecro-like features on the surface to stick to inner vessel surface so that the drug adheres to the treatment site, and to provide a time-release controlled by the resorption or dissolving of the coating to further improve efficacy. Such velcro-like features may be constructed with nanoscale structures made of organic or inorganic materials. Reducing the volume of foreign matter and exposing remaining tissue and extracellular matrix to drugs, stimulation, or sensors can make any of these techniques more effective.

Another way to infuse fluid is to supply pressurized fluid at the proximal portion of the guidewire lumen (gravity or pressure feed) intravenous bag, for example. A hemostatic seal with a side branch is useful for this purpose; tuohy-borst adapters are one example of a means to implement this.

Balancing the relative amount of infusion versus fluid volume aspirated allows control over the vessel diameter; aspirating more fluid than is instilled will evacuate the vessel, shrinking its diameter, and allow cutting of lesion at a greater diameter than the atherectomy catheter. This has been a problem for certain open cutter designs that use aspiration, because the aggressive aspiration required to trap the embolic particles evacuates and collapses the artery around the cutter blades; this is both a performance issue because the cutter can bog down from too high torque load, and the cutter can easily perforate the vessel. The shielded design described here obviates both problems, and further requires less aggressive aspiration to be effective, giving a wider range of control to the user.

The devices of the present invention may also be used in conjunction with other structures placed in the body lumens. For example, as shown inFIG. 17, one way to protect the vessel and also allow for maximum plaque volume reduction is to deploy a protective structure such as a stent, thin expandable coil or an expandable mesh182within a lesion. As this structure expands after deployment, the thin wire coil or the struts push radially outward through the plaque until it becomes substantially flush with the vessel wall. This expansion of thin members requires minimal displacement of plaque volume and minimizes barotrauma produced in balloon angioplasty or balloon expanded stent delivery. Once the protective structure has expanded fully, atherectomy can be performed to cut away the plaque inside to open up the lumen. The vessel wall is protected by the expanded structure because the structure members (coil or struts) resist cutting by the atherectomy cutter, and are disposed in a way that they cannot invaginate into the cutter housing (and thereby be grabbed by the cutter). It is also possible to adjust the angle of the windows on the atherectomy catheter cutter housing so that they do not align with the struts or coils; the adjustment to orientation may be accounted for in the coil or strut design, in the cutter housing design, or both. Furthermore, the protective member can be relatively flexible and have a low profile (thin elements), so that it may be left in place as a stent. Because the stent in this case relies mainly upon atherectomy to restore lumen patency, it may be designed to exert far less radial force as it is deployed. This allows usage of greater range of materials, some of which may not have as high of stiffness and strength such as bioresorbable polymers and metal alloys. Also, this allows a more resilient design, amenable to the mechanical forces in the peripheral arteries. It also minimizes flow disruption, to minimize hemodynamic complications such as thrombosis related to the relatively low flows found in the periphery. It is also possible to perform atherectomy prior to placing the protective structure, whether or not atherectomy is performed after placing the structure.

Additional variations of systems include devices100having a cutting assembly170comprising spinning turbine-like coring cutter172as shown above and as shown inFIG. 18A.FIG. 18Bshows a side view of the coring cutter170. In use, the coring cutter can be hydraulically pushed to drive the sharp edge through tissue. The turbine like cutters has helical blades174on the inside of the sharp cylinder housing176(shell). The coring cutter170may also have spokes or centering devices184as shown to inFIGS. 19A to 19Fcenter the shell about the guidewire. This helps to keep the cut of the plaque centered about the vessel wall for safety. The spokes also act as an impeller to pull stenotic tissue back and this helps to drive the cutter forward as well as achieve aspiration to minimize embolization. In the hydraulically driven cutter design, an anchor186is deployed in tissue and is connected to a backstop192. A balloon or hydraulic chamber188is then pressurized to expand and pushes the cutting blade190forward through the lesion (SeeFIG. 19G). One advantage of this approach may be that the technique is similar to angioplasty (which involves pumping up a balloon with an endoflator). One means of anchoring is to use an anchoring guidewire, for example, a guidewire with an inflatable balloon to be placed distal to the atherectomy catheter. Alternatively, the technique of anchoring distally can be used with the previously described torque shaft driven atherectomy catheter.

It is also possible to use the devices and methods described here to restore patency to arterial lesions in the coronary circulation and in the cerebrovalscular circulation, both by debulking de novo lesions and by debulking in stent restenosis.

The devices and methods described herein also work particularly well in lesions that are challenging to treat with other methods: at bifurcations, in tortuous arteries, and in arteries which are subject to biomechanical stresses (such as in the knee or other joints).

In a further variation of the devices described here, the motor drive unit may be powered by a controller that varies the speed and torque supplied to the catheter to optimize cutting efficiency or to automatically orbit the cutter using variable speed with a fixed flexible distal length of catheter (or providing further orbiting control by controlling the length of the distal flexible section of the catheter).

It is also possible to use feedback control to operate the catheter in a vessel safe mode, so that the rate of cutting is decreased as the vessel wall is approached. This may be accomplished through speed control, or by reducing the degree to which the cutting blades penetrate above the housing window by retracting the cutter axially within the housing. Feedback variables could be by optical (infrared) or ultrasound transducer, or by other transducers (pressure, electrical impedance, etc.), or by monitoring motor performance. Feedback variables may also be used in safety algorithms to stop the cutter, for example in a torque overload situation.

The atherectomy catheter may be further configured with a balloon proximal to the cutter, for adjunctive angioplasty or stent delivery. The catheter may optionally be configured to deliver self-expanding stents. This provides convenience to the user and greater assurance of adjunctive therapy at the intended location where atherectomy was performed.

Further methods include use of similar devices to debulk stenosis in AV hemodialysis access sites (fistulae and synthetic grafts), as well as to remove thrombus. By removing the cutter housing and recessing the fluted cutter within the catheter sheath, a suitable non-cutting thrombectomy catheter may be constructed.

Other methods of use include excising bone, cartilage, connective tissue, or muscle during minimally invasive surgical procedures. For example, a catheter that includes cutting and burr elements may be used to gain access to the spine for performing laminectomy or facetectomy procedures to alleviate spinal stenosis. For this application, the catheter may be further designed to deploy through a rigid cannula over part of its length, or have a rigid portion itself, to aid in surgical insertion and navigation.

For this reason, it is advantageous to couple atherectomy with stenting. By removing material, debulking the lesion, a lesser radial force is required to further open the artery and maintain lumen diameter. The amount of debulking can be tuned to perform well in concert with the mechanical characteristics of the selected stent. For stents that supply greater expansion and radial force, relatively less atherectomy is required for satisfactory result. An alternative treatment approach is to debulk the lesion substantially, which will allow placement of a stent optimized for the mechanical conditions inherent in the peripheral anatomy. In essence, the stent can support itself against the vessel wall and supply mild radial force to preserve luminal patency. The stent may be bioresorbable, and/or drug eluting, with the resorption or elution happening over a period for days to up to 12 weeks or more. A period of 4 to 12 weeks matches well with the time course of remodeling and return to stability as seen in the classic wound healing response, and in particular the known remodeling time course of arteries following stent procedures. In addition, the stent geometry can be optimized to minimize thrombosis by inducing swirl in the blood flow. This has the effect of minimizing or eliminating stagnant or recirculating flow that leads to thrombus formation. Spiral construction of at least the proximal (upstream) portion of the stent will achieve this. It is also beneficial to ensure that flow immediately distal to the stent does not create any stagnant or recirculation zones, and swirl is a way to prevent this also.

FIG. 20Aillustrates another variation of a device for clearing obstructions within body lumens. In some cases where a vessel is totally occluded, a tough fibrous or calcific cap6completely or almost completely blocks the lumen. Because of this blockage, fluid cannot flow past the occlusion. This stagnation also makes it difficult or impossible to properly insert a wire across the lesion with an atherectomy device or stiff catheter.

In a typical case of a total occlusion, it is also difficult if not impossible to visualize the lumen near the occlusion because any injected contrast agents cannot flow through the occlusion site.

FIG. 20Ashows a system for treating total occlusions. The system can include a support catheter comprising a support tube or catheter200, having a central lumen202, the catheter may include side lumens or ports206, for flush and aspiration. The catheter central lumen202can be used to deliver contrast agents208. In addition, tip centering mechanisms, and an atraumatic tip can be useful. The support catheter can be used with any lumen-creating device210, such as the devices100described above, a laser catheter, an RF probe, or an RF guidewire. When using a coring cutter as shown inFIG. 20A, the cutter can have a sharp edge at its tip, helical flutes, helical grooves, or any other mechanism that enables penetration of the fibrous or calcific cap. The cutter and the shaft can be advanced forward within the support catheter, and one or more balloons or baskets can also be deployed by the support catheter to help center it in the vessel.

The lumen-creating device200can optionally be made to have a shoulder212at its distal end, as shown inFIG. 20A. The shoulder212acts as a stop to limit the depth at which the device200protrudes beyond the support catheter200. Such a safety measure may be desired to protect the vessel wall. Driving the device200through the tough fibrous cap creates a lumen in the cap. A guidewire may then be placed into the lumen created in the fibrous cap. The coring cutter may be removed with the core.

Next, a guidewire can be used with a cutter assembly to remove some or all of the remaining mass in the vessel. Alternatively, the initial lumen made may be adequately large without further atherectomy. Technical success is typically less than 30 percent or less than 20 percent residual stenosis. Also, balloon angioplasty with or without stenting may be performed following establishment of a guidewire lumen with a support catheter and a lumen-creating catheter.

Contrast injection and aspiration ports near the distal end of the support circulate contrast agents, enabling the use of fluoroscopy to visualize the lumen adjacent to the total occlusion during diagnosis or treatment. The central lumen202of the support catheter200can also be used to inject or aspire the contrast agents208. The contrast agents can circulate through the center lumen202in the support catheter200and at least one port206in various configurations. The fluid can circulate about the distal tip of the catheter, the motion of the fluid being circular as shown inFIG. 20B. For example, the fluid can be injected through the central lumen202, travel around the distal tip, and then is aspirated back into the support catheter through ports206on the side of the surface of the support catheter200. To illustrate another possible configuration, the fluid can be ejected through the side ports, and then aspired through the central lumen. This recirculation of the contrast agent permits imaging of the vessel at the site of the occlusion.

Any of the atherectomy devices100described herein can be used as a tool to treat chronic total occlusions (CTO) or a complete blockage of the artery. The frontward cutting and tip-steering capabilities allows the physician to controllably create a channel through the blockage. In one such method for creating this channel (recanalization) the physician places the device100proximal edge of a blockage10as shown inFIG. 21A.

The physican steer the cutting assembly102tip towards the center of the vessel as described above. Then, the physician advances a guidewire144forward to penetrate the blockage10. Now that the cutting assembly102is located in or adjacent to the blockage10, the motor is actuated to begin the cutting process allowing the cutting assembly102to follow the guidewire114. During this process, the physician steers the cutting assembly102or catheter tip as necessary to keep the cutter centered in the lumen. With the catheter support close to its tip, the wire can be controllably advanced further through the blockage and the catheter can follow by cutting its way forward as shown inFIG. 21C.

The process continues until the cutting assembly102passes through the blockage10. However, during the recanalization process, the guidewire144can be exchanged easily, as shown inFIG. 21B, so that the physician can selectively use the optimal guidewire. The catheter has a guidewire lumen that runs along its length and thus allows for this guidewire exchange.

Typically, the physician is not able to visualize the anatomy adjacent to the blockage using the fluoroscope because contrast dye injection cannot be performed due to the complete blockage. The catheter above overcomes this problem because of its ability to aspirate at the cutting assembly. Thus dye injection can be introduced into the target area and circulated back into the catheter via the catheter aspiration mechanism. The flow of dye near the catheter tip allows the physician to visualize the anatomy during the recanalization process.

FIGS. 22A and 22Bshow another method of recanalizing a blockage10. In this variation, the physician advances the guidewire144through the device100and between the tissue layers of the vessel (subintimal channel) such as the space between the tunica media (middle layer of vessel wall) and the tunica adventitia (outer elastic layer of the vessel wall). The atherectomy device100described herein can be used to provide support for the advancement of the guidewire144through the subintimal channel as well as a means for steering back into true lumen. Once the wire has crossed the blockage through the subintimal channel, the device advances forward to follow the guidewire144across the blockage10and is steered back towards the true lumen as shown inFIG. 22B. The cutter assembly102can be activated to help pierce a channel into back into the true lumen. In clinical terminology, this catheter is used as a “re-entry device”.

The deflected catheter tip is elastic or spring-like. The degree of the deflection is limited by the diameter of the lumen. As plaque is removed during the atherectomy process, the degree of deflection automatically increases. Since the deflected catheter tip is radiopaque (can be visualized with fluoroscope), its degree of deflection can be continuously visualized during the procedure and thus allows the physician to visualize the progress in the opening of the lumen without having to pause and perform a dye injection. Limiting dye injections helps to minimize health problems for the patient and saves procedure time.

It is important to ensure that the guidewire is axially fixed relative to the target vessel during operation of the atherectomy device100to prevent the guidewire tip144from traumatizing the vessel. This can be accomplished by having an anchoring mechanism154to anchor the wire to the vessel. The mechanism154can be an inflatable balloon on the wire as shown inFIG. 23A, expandable basket as shown inFIG. 23B, deployable loops as shown inFIG. 23C, a deployable helical coilFIG. 23D, a wire taking on a shape of a helical coil or a wave on the guidewireFIG. 23E, a porous umbrella or a mesh as shown inFIG. 23F. These mechanisms can all collapse compactly onto profile as small as a typical guidewire to pass through the guidewire lumen on the catheter and expand as large as the distal vessel diameter to anchor. These mechanisms can also act as a way to prevent plaque debris from floating down stream to provide a type of embolic protection.

It is noted that the descriptions above are intended to provide exemplary embodiments of the devices and methods. It is understood that, the invention includes combinations of aspects of embodiments or combinations of the embodiments themselves. Such variations and combinations are within the scope of this disclosure.