US20080228208A1 - Intralumenal material removal using a cutting device for differential cutting - Google Patents

Abstract

Intralumenal material removal systems are provided using an advanceable and rotatable cutter assembly designed for differential cutting. The intralumenal material removal system includes a cutter assembly positionable in the body cavity of a mammalian subject. One embodiment of the cutter assembly comprises a cutter with blades that are designed and arranged to form an acute blade angle of attack with the matter-to-be-removed. The cutter assembly is axially advanceable by translating the drive shaft and rotatable by rotating the drive shaft. The occlusive material is scraped by the cutter assembly and may be aspirated to remove the material from the body cavity. The cutter assembly may provide aspiration ports positioned between facing surfaces of the blades.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of Ser. No. 10/442,888, filed on May 20, 2003, issuing as U.S. Pat. No. 7,344,546 on Mar. 18, 2008, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/453,846 filed Mar. 10, 2003, and is a continuation-in-part of U.S. patent application Ser. No. 09/724,914 filed on Nov. 28, 2000, now U.S. Pat. No. 6,565,588, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/194,805, filed Apr. 5, 2000. The disclosures of the aforementioned applications are herein incorporated by reference in their entirety.
FIELD OF THE INVENTION
• The present invention relates to systems and methods for removing material, such as obstructions and partial obstructions, from a body cavity of a mammalian subject, such as a blood vessel. More particularly, the present invention relates to systems and methods for removing material from a cavity of a mammalian subject using a rotatable cutter assembly having blades designed for differential cutting.
BACKGROUND OF THE INVENTION
• In the medical field it is often required that a medical practitioner manipulate devices within a body cavity residing in a patient. In some cases, undesirable matter may exist or become lodged within the cavity and must be removed by the practitioner. At times, accumulation of the matter may reduce or cut off the flow of fluid, such as blood, and other essential components through the body cavity.
• Some procedures for removing undesirable matter involve the challenging operation of maneuvering a cutting device within small confines of interior body cavities. In order to lead the cutting device to the site for removal of the matter, it must be routed through various internal structures, and the path through the body to the removal site may be tortuous. Usually, the cutting device is coupled to or otherwise associated with various devices, such as a drive shaft, guide wire, catheter(s), etc. that may guide the cutting device to the removal site.
• One application for a cutting device is to remove atherosclerotic obstructions and partial obstructions. The use of rotating cutter assemblies is an established therapeutic intervention, and many different atherectomy methods and devices have been conceived and developed. Many of these systems involve placement of a guide catheter, a guidewire and a cutting device in proximity to an obstruction or partial obstruction in a blood vessel and then advancing and rotating the cutting device to cut or ablate the obstruction.
• The following U.S. patents describe many types and specific features of devices for removing matter, which may be useful in atherectomy procedures: U.S. Pat. Nos. 4,898,575; 5,127,902; 5,409,454; 5,976,165; 5,938,670; 5,843,103; 5,792,157; 5,667,490; 5,419,774; 5,417,713; 4,646,736; 4,990,134; 4,445,509; 5,681,336; 5,695,507; 5,827,229; 5,938,645; 5,957,941; 5,019,088; 4,887,613; 4,895,166; 5,314,407; 5,584,843; 4,966,604; 5,026,384; 5,019,089; 5,062,648; 5,101,682; 5,112,345; 5,192,291; 5,224,945; 4,732,154; 4,819,634; 4,883,458; 4,886,490; 4,894,051; 4,979,939; 5,002,553; 5,007,896; 5,024,651; 5,041,082; 5,135,531; 5,192,268; 5,306,244; 5,443,443; and 5,334,211. These U.S. patents are incorporated by reference herein in their entireties.
• Despite the varied approaches to the systems and methods exemplified by the U.S. patents cited above, many challenges remain in providing systems and methods for removing material from a lumen, such as a blood vessel, safely and reliably and without causing complications. The safety and reliability of the system is manifestly critical.
• The cutting device must not damage delicate beneficial material, such as the walls of a structure or other healthy tissue, which often surrounds the unwanted matter. Thus, it is important for a cutting device to separate the unwanted matter from the beneficial material in a safe manner that is not so aggressive as to damage the beneficial material. Much attention is required in designing such a cutting device that has an optimal cutting surface and material removal mechanism.
• Some special devices are designed to ablate unwanted matter without harming beneficial material by a method known as differential cutting. Differential cutting is based on the observation that oftentimes the unwanted matter located in the cavity is rigid and has a less elastic quality than the beneficial material of the body cavity. Generally, the beneficial material, such as the wall of a blood vessel wall, has a shear modulus of elastic stiffness that is a relatively low value. As a result, when a blade that is designed for differential cutting contacts the beneficial material, the material becomes deformed at the point of contact and large shear stresses in the beneficial material are not exerted. By comparison, the unwanted matter is generally more rigid and has a higher value of shear modulus of elastic stiffness. Harder material is not able to deform when contacted by the differential cutting blade, and shear stresses are consequently exerted on the more rigid material. In this manner, fragments of the harder, undesirable matter are cut away by differential cutting blades, while the more elastic, beneficial material is unharmed.
• Various cutting devices have been proposed that utilize differential cutting principles. U.S. Pat. No. 4,445,509 describes differential cutting in the context of an atherectomy device. Some differential cutting devices have particular features to allow for differential cutting, such as the use of diamond grit on a cutting surface. This diamond grit surface forms random angles of attack and creates random cutting characteristics at various points of contact with the target undesired matter. In using diamond grit cutting devices, when applying increased depth of force of the device into the target matter to be removed, there is a greater risk of cutting into the supporting beneficial material in proximity to the target undesired matter. Thus, these prior devices require extreme caution in use in order to avoid cutting beneficial material.
• One of the particular challenges of removing matter from the interior of lumens is that the drive and cutter assemblies must be small enough and flexible enough to travel over a guidewire to a desired material removal site, such as the site of an obstruction or occlusion. Yet, the drive and cutter assemblies must be large enough and have structural integrity sufficient to operate reliably and effectively to cut or scrape the obstruction. Additionally, removal of the debris from the material removal site using an aspiration system is generally desirable. The drive and cutter assemblies therefore desirably incorporate a debris removal system as well.
• The size and consistency of the material comprising an obstruction are frequently not well characterized prior to introduction of the material removal device. Thus, although devices and cutters having different sizes and properties may be provided, and may even be interchangeable on a material removal system, it is difficult to ascertain which combination of features is desired in any particular operation prior to insertion of the device. The use of multiple cutter assemblies having different properties during a materials removal operation is inconvenient at best, since it requires removal of each independent device and interchange of the cutter assemblies, followed by reinsertion of the new cutter assembly, or of a new device entirely. Interchange and reinsertion of cutter assemblies is time consuming and generally deleterious to the health and condition of the patient undergoing the procedure.
• Many different types of expandable cutters have been conceived in an effort to provide a cutter having a small diameter profile that may be conveniently delivered to and removed from the site of the desired material removal, and that is expandable at the site to provide a larger diameter cutter. The following U.S. patents disclose various approaches to expandable cutter assemblies: U.S. Pat. Nos. 5,540,707; 5,192,291; 5,224,945; 5,766,192; 5,158,564; 4,895,560; 5,308,354; 5,030,201; 5,217,474; 5,100,425; and 4,966,604. These U.S. patents are incorporated by reference herein in their entireties.
• Although numerous approaches to cutter assemblies have been developed, there is still a need for a cutter assembly that is conveniently navigable to the material removal site and that that removes matter of different types in a safe and effective manner, without harming surrounding beneficial material.
SUMMARY OF INVENTION
• Methods and intralumenal material removal systems of the present invention involve a material removal component, referred to herein as a “cutter” or “cutter assembly”. The cutter assembly is positionable in a lumen of a mammalian subject and operably connected to system controls, mechanical and power systems, usually by means of a rotating drive shaft. The cutter assembly comprises one or more distally located cutting or abrading head(s) having one or more cutting and/or abrading surfaces and is advanceable by translating the drive shaft and rotatable by rotating the drive shaft.
• According to one embodiment of the present invention, the removal system comprises a cutter assembly having blades that are specially designed and arranged to cut or scrape matter while not damaging other beneficial material, or at least doing minimal damage to such beneficial material. The blades are provided at acute angles of attack, generally less than 90 degrees.
• The cutter assembly may be either fixed or adjustable in diameter. In one particular embodiment, an expandable cutter is adjustable between a smaller diameter condition, in which it may be guided to and withdrawn from the desired material removal site, and a larger diameter condition, in which it may be operated during a material removal operation. The expandable cutter may thus be introduced to and withdrawn from the material removal site in a retracted, smaller diameter condition that facilitates translation and navigation of the device through various lumens, such as blood vessels. The expandable cutter may be selectively expanded at the material removal site to facilitate cutting, removal and aspiration of the material desired to be removed.
• The material removal system often provides removal of debris, generally via aspiration through one or more material removal ports in the cutter assembly or another component in proximity to the cutter assembly. Debris generated during a material removal operation is removed by aspiration through the material removal ports and withdrawn through a sealed lumen formed, for example, between the cutter assembly drive shaft and a catheter. The sealed lumen is connectable to a vacuum source and aspirate collection system. The ports may be disposed between facing surfaces of the blades.
• According to one embodiment, the material removal device of the present invention comprises multiple cutting members that may have different characteristics. For example, dual cutting and/or abrading members may be provided, one of which is expandable and one of which has a fixed diameter. In one embodiment, a fixed diameter cutter is mounted distal to an expandable diameter cutter. The fixed diameter cutter may take any of a variety of configurations and, according to one embodiment, has a generally ovoid profile and a plurality of cutting flutes. The fixed diameter cutter may also be provided with ports and/or cutouts that may be selectively employed as aspiration or infusion ports. The expandable diameter cutter, positioned proximal to the fixed diameter cutter, may also be provided with ports that may be selectively employed as aspiration or infusion ports. Any one or all of the cutters may be designed for differential cutting, according to the designs presented herein.
• In one embodiment, the cutter assembly drive shaft operates bidirectionally and the adjustable diameter cutter is expanded or retracted selectively and controllably upon rotation in opposite directions. Upon rotation of the drive shaft and dual cutter assembly in a first direction, the fixed diameter cutter is used as the primary cutter and the expandable cutter remains in a smaller diameter condition, while upon rotation of the dual cutter assembly in a second direction, opposite the first, the expandable cutter is in a larger diameter condition and serves as the primary cutter. The present invention uses hydrodynamic, centrifugal and/or frictional forces to expand and contract the dual cutter assembly, thereby obviating the need for additional actuation systems, which add considerable complexity and rigidity to such systems.
• Liquid infusion may be provided in proximity to the cutter assembly in addition to or alternatively to aspiration. Infusion of liquids may be used to provide additional liquids for materials removal or to deliver lubricating fluids, treatment agents, contrast agents, and the like. Infusion of fluids in proximity to the area of a material removal operation may be desirable because it tends to reduce the viscosity of the materials being removed, thus facilitating removal through relatively small diameter lumens. Infusion of liquids also desirably tends to reduce the volume of blood removed during the operation. According to one embodiment, a sealed lumen formed between the cutter assembly drive shaft and a catheter may alternatively and selectively be used as aspirate removal system and an infusion system. The sealed lumen may thus be selectively connectable to a vacuum source and aspirate collection system for aspiration, and an infusion source for infusion of liquids. Ports in or in proximity to the cutter assembly may be thus be employed, selectively, as aspiration and infusion ports.
• According to another embodiment, an infusion system may be provided in addition to and independent of the aspiration system. In one embodiment, an infusion sleeve is provided that extends distal to the material removal element. The infusion sleeve is sealed for the length of the catheter and incorporates distal infusion ports. The infusion sleeve may extend through the lumen formed by the drive shaft and may be fixed, or usually, translatable with respect to the cutter assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows one embodiment of the present invention highlighting the distal end of a primary sheath with an expandable cutter assembly in the expanded condition.
• FIG. 2 shows an enlarged, partially cross-sectional perspective view of one embodiment of an expandable cutter assembly and associated connections with the drive shaft and flexible conduit catheter.
• FIG. 3 shows an enlarged, exploded perspective view of one embodiment of an expandable cutter assembly of the present invention.
• FIG. 4 shows an enlarged, side perspective view of one embodiment of the cutting members in association with the central block of an expandable cutter assembly of the present invention.
• FIG. 5A illustrates an enlarged, perspective view of one embodiment of a dual cutter assembly of the present invention with the cutter assembly in a contracted configuration, and
• FIG. 5B illustrates an enlarged, front view of one embodiment of the dual cutter assembly ofFIG. 5A with the cutter assembly in a contracted configuration.
• FIG. 6A illustrates an enlarged, perspective view of one embodiment of the dual cutter assembly ofFIG. 6A with the cutter assembly in an expanded configuration, andFIG. 6B illustrates an enlarged, front view of one embodiment of the dual cutter assembly ofFIG. 6A with the cutter assembly in the expanded configuration.
• FIGS. 7A-7C illustrate blade angles, whereinFIG. 7A shows a side view of one cutter assembly,FIG. 7B is a cross-sectional view depicting the blade angle of the blades in the cutter assembly ofFIG. 7A, according to one embodiment of the present invention, andFIG. 7C illustrates a prior art cutting device.
• FIGS. 8A and 8B are schematic diagrams illustrating blade angles, whereinFIG. 8A illustrates a blade angle of attack according to one embodiment of the present invention, and
• FIG. 8B illustrates one prior art cutting device.
• FIG. 9 shows another embodiment of the present invention illustrating the distal end of a coiled metallic catheter with a cutter assembly in the expanded configuration.
• FIG. 10 depicts the embodiment ofFIG. 9 in a exploded perspective.
• FIG. 11 provides a cross-sectional perspective of an alternative embodiment of the present invention.
• FIG. 12 shows an embodiment of a expandable cutter highlighting the central block and cutting members assembly.
• FIG. 13A illustrates a side view of another embodiment of a fixed diameter distal cutter, andFIG. 13B provides a front perspective of the fixed diameter distal cutter illustrated inFIG. 13A.
• FIG. 14 is a schematic diagram illustrating an external view of a cutter assembly having large ports between blades according to one embodiment of the present invention.
• FIGS. 15A-15B are schematic diagrams illustrating exemplary curved blades of a cutter assembly, whereinFIG. 15A shows a cup-shaped cutter assembly with symmetrically curved and gradually sloping blades, andFIG. 15B shows a single blade having an asymmetrically curved profile.
• FIGS. 16A-16D are schematic cross-sectional diagrams illustrating different numbers of blades according to various embodiments of the present invention, whereinFIG. 16A shows seven blades,FIG. 16B shows six blades,FIG. 16C shows five blades, andFIG. 16D shows three blades.
• FIGS. 17A and 17B are schematic diagrams illustrating ports, whereinFIG. 17A shows an internal cut-away view of a cutter assembly with ports, according to one embodiment of the present invention, andFIG. 17B shows a cutter assembly with an exploded view of a port.
• FIGS. 18A to 18C are schematic diagrams illustrating a cutter assembly embodiment wherein cutter blades protrude beyond the diameter of a proximal ring.FIG. 18A is a prospective view from the distal to proximal ends of the cutter assembly,FIG. 18B is a prospective view from the proximal to distal ends of the cutter assembly, andFIG. 18C is an angled side view of the cutter assembly.
• FIG. 19A shows an alternative embodiment of an expandable cutter assembly in the contracted configuration, andFIG. 19B provides a front perspective of the alternative embodiment of the present invention illustrated inFIG. 19A.
• FIG. 20A shows an alternative embodiment of an expandable cutter assembly in the expanded configuration andFIG. 20B provides a front perspective of the alternative embodiment of the present invention illustrated inFIG. 20A.
• FIG. 21 shows a drive shaft of the present invention having right-lay and left-lay helical configuration.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• As used herein in the description of various components, “proximal” or “antegrade” refers to a direction toward the system controls and the operator along the path of a drive system, and “distal” or “retrograde” refers to the direction away from the system controls and the operator and toward or beyond a terminal end of the cutter assembly. In general, the material removal system of the present invention comprises a cutter assembly positioned at the distal end of the material removal system.
• Exemplary material removal systems, components and subassemblies suitable for use in connection with methods and systems of the present invention are disclosed and described in the U.S. patents incorporated herein by reference, and in PCT Patent Publication WO 01/76680, entitled “Intralumenal Material Removal Systems and Methods”, which is incorporated herein by reference in its entirety. In particular embodiments, cutter blades of the cutter assembly operate according to differential cutting principles.
• The cutter assembly is guided to the material removal site and is actuated to cut, grind or ablate, or otherwise separate the occlusive material from the beneficial material in proximity to the occlusive material, and to remove the occlusive material from the site. The removal system incorporating the cutter assembly may also include numerous other components that facilitate operation of the cutter assembly, according to the present invention. For example, the removal system may include a control unit, catheter assembly and/or manifold assembly, all of which remain outside the body during a material removal operation. In one embodiment, an advancer system may be integrated in the control unit and may incorporate one or more slip seals for the cutter assembly drive shaft, aspiration and/or infusion connections, and additionally may incorporate a track system for axially displacing the rotating cutter assembly drive shaft and cutter assembly relative to the control unit. The control unit may comprise a base arranged so that the control unit may be stably supported on a work surface or a body surface during material removal operations. The control unit also may incorporate control systems for actuating, adjusting and providing system information concerning power, drive shaft rpm, cutter assembly drive shaft axial translation, aspiration, infusion and the like.
• In other embodiments of a material removal system of the present invention, the control unit may remotely control operation of the cutter assembly, the control unit communicating instructions by sending signals to the various other components of the removal system, e.g. using stereotactic techniques. The cutter assembly may further be guided to the removal site through a variety of local or remote mechanisms, such as magnetic forces, electrical means, etc.
• In some embodiments of the material removal system, the cutter assembly may be guided to the removal site using a guidewire. In these cases, the cutter assembly may be translated over the guidewire. The guidewire is navigated through one or more lumens in a subject, such as blood vessels, to a desired material removal site. Many suitable guidewires are known in the art, including flexible guidewires, and may be used with the material removal system of the present invention. Guidewires having a diameter of from about 0.009 inch to about 0.018 inch and having an atraumatic tip are often used.
• A guiding catheter may be used for guiding the guidewire, and subsequently the cutter assembly, to the lumen or other body cavity to be treated, as is typical and well known in the art for interventions in coronary, vein graft or peripheral arteries. In operation, the guiding catheter and the guidewire are generally introduced into a lumen of a patient, such as the femoral artery, and navigated or guided to the site of the desired material removal operation.
• A guidewire brake or clamp is often provided in proximity to or integrated with the material removal system to hold the guidewire in a stationary, fixed position during operation of the cutter assembly. Rotation and axial displacement of the guidewire may be prevented using either an automatic or a manual grip. An automatic guidewire braking system may be implemented using a solenoid-activated brake that is automatically actuated to brake during activation of the cutter assembly motor drive. A manual guidewire braking system may be actuated by a manual, over-center clamp, cam and brake shoe assembly or another mechanical device. An interlock system may be incorporated in connection with a manual brake system to prevent actuation of the cutter assembly drive system if the guidewire is not in a clamped, stationary condition.
• An aspiration source, such as a roller pump, may be provided to provide aspiration to the cutter assembly. There may also be a collection vessel such as a collection bag or, for example, a commercially available evacuated container having a suitable volume. Alternatively, the aspiration source may be provided as a syringe or similar device actuated by a motor, pressurized gas, or the like. The aspiration source may alternatively be provided as a small, electrical vacuum pump with a suitable collection device.
• The configuration and construction of the control unit and the manifold assembly may vary, depending on specific desired applications for intralumenal material removal. Some suitable designs and configurations are well known in the art. In some embodiments, a control unit is provided as a separate unit in electrical and operating communication via a flexible cable with an advancer unit. An advancer unit may be configured ergonomically and constructed for placement in proximity to and/or in contact with the patient. In one embodiment, the base of advancer unit is configured to rest stably on the leg of a patient while a material removal operation takes place. A tracking unit may additionally have a work platform providing a level surface for use of the operator and associated medical professionals.
• In one embodiment, a control unit houses various components, such as a programmable logic controller and power source in operable communication to provide power and to control operation of a vacuum control unit, a cutter assembly advancer unit, a guidewire brake unit, a cutter assembly drive system, an aspiration control unit and/or a temperature control unit. The control unit may be provided as a separate console and may incorporate various displays for providing information concerning operating conditions and feedback from the material removal site to the operator. According to one embodiment, the control unit provides continuously updated output to an operator including such operating parameters such as temperature at the material removal site; cutter assembly rotation rate and/or advance rate; aspiration rate and/or volume; infusion rate and/or volume; and the like. The control unit may additionally provide adjustable controls permitting the operator to control operating parameters of the cutter assembly and material removal operation. Alternatively, adjustable controls and feedback data may be incorporated in an advancer unit, or a single integrated control and advancer unit may be provided.
• The vacuum control unit may comprise, for example, a solenoid operated vacuum valve. The cutter assembly advance system may comprise, for example, a stepper motor. A guidewire brake unit may comprise, for example, a solenoid actuated braking device. The cutter assembly drive system for rotating the cutter assembly may be operated using a pneumatic- or electric-powered motor. The aspiration control may comprise, for example, a vacuum assist motor/pump. The temperature control monitor may be in operable communication with a temperature probe providing continuous or intermittent feedback relating to the temperature or temperature changes at the site of the material removal operation.
• In some embodiments of the present invention, a high-speed electric motor supplied by a power source, e.g. a battery, is utilized for the cutter assembly drive system. The motor may be geared and/or separated by a short flexible drive shaft that couples the motor to the cutter assembly drive shaft. The motor may thus be mounted off-axis with respect to the cutter assembly drive shaft. This arrangement also permits translation and advancing of the cutter assembly drive shaft independent of the motor, permitting the motor to remain stationary during material removal operations. In alternative embodiments, the motor assembly and other components, such as the drive shaft and cutter assembly may be axially translatable in the advancer unit, as described in more detail below.
• According to some embodiments of the material removal system of the present invention, the drive system may be unidirectional and capable of rotating the cutter assembly drive shaft in one rotational direction, or it may be selectively bi-directional and capable of rotating the drive shaft selectively in both a clockwise and counterclockwise direction. The drive system is also usually capable of rotating drive shaft at variable speeds ranging from 500 rpm to 150,000 rpm, more often from 500 to 60,000 rpm. In an exemplary embodiment of the invention, drive system is a direct current variable speed micro-motor capable of operating at rotational speeds of from 500 rpm to 150,000 rpm. It is understood that a variety of motors may be employed in the system and the range of speeds and capabilities may vary according to the type and site of material removed, and the type of cutter assembly utilized. The present invention also contemplates the use of alternative means of rotating the drive shaft, such as air-driven turbines, and the like.
• A proximal end of the drive shaft is operably connected directly, or via a coupler or transmission system, to the drive system, while a distal end of the drive shaft is operably connected, directly or via a coupler, to the cutter assembly mounted to a distal end of the drive shaft. In one embodiment, the drive shaft is a flexible, hollow, helical, torque-transmitting shaft. Hollow, multi-filar metallic drive shafts are known in the art and are suitable for use with the material removal system and cutter assembly of the present invention. The cutter assembly drive shaft may be a multi-filar stainless steel coil drive shafts having a bi- tri- or quad-filar construction. Coil drive shafts having an inner diameter of from about 0.015 to 0.025 inch and an outer diameter of from about 0.025 to 0.035 inch are generally suitable for atherectomy applications.
• One embodiment of system has a tracking unit for axially translating drive shaft and associated components. The tracking unit may comprise a body having one or more axial translation mechanisms, such as rails running along the longitudinal axis of a bed on which rides a motor assembly. Alternative embodiments of the present invention may employ any conventional axial translation mechanisms including rails, slots, tracks, wheels, and the like. The motor assembly may engage rails to permit controllable axial translation in either an antegrade or retrograde direction, which in turn facilitates axial translation of expandable cutter assembly and associated components. The motor assembly may house several components and assemblies, such as, but not limited to one or motors, drive shafts, gear drives and the like. A guide wire brake system may be fixedly connected to the proximal end of the tracking unit and serve to releasably restrict axial and rotational movement of the guide wire. In this particular embodiment, a movement-restricting mechanism, such as a cam-lever and brake shoe(s) assembly, may comprise the guidewire brake system. Embodiments of the present invention may incorporate any conventional movement-restriction mechanism or mechanisms which serve to controllably limit axial and rotational movement of the guide wire. The tracking unit may further comprise a cover encompassing the motor assembly and the bed. In addition, a locking mechanism may be provided to the tracking unit that controllably restricts axial movement of motor assembly. Any conventional locking mechanism may be employed in the present invention, such as, but not limited to a system whereby a restrictive force is exerted from tracking unit cover to the motor assembly. For example, an element may extend from the top face of motor assembly through a longitudinal slot in the tracking unit cover which may be held in tight association with the cover by a clamping device, such as a threaded knob. Of course, various embodiments of the present invention envision may include any of a wide variety of conventional locking mechanisms.
• The guide wire usually passes through the cutter assembly, catheter, motor system and wire brake and exits out the proximal end of the tracking unit. Housed within the coupler recess may be a drive shaft to drive train coupling assembly. In some embodiments, a magnetic coupler is also provided. In one particular embodiment, the magnetic coupler may comprise a drive shaft connector having a first magnet recess for receiving and magnetically engaging one or more magnets, as well as a plurality of anti-slip cogs. A complementary drive train connector, also having a plurality of anti-slip cogs, may have one or more magnets fixedly connected to drive train connector recess. Drive train connector may further comprise a guide tube, which passes through complementary central apertures of a drive train connector and magnet to extend beyond the distal face of magnet. The guide tube may serve to align and guide the drive shaft connector to properly seat and releasably engage magnet of the drive train connector. The drive shaft connector may be provided with a central aperture for receiving the guide tube, thereby aligning the drive shaft connector with the drive train connector and maintaining a concentric arrangement.
• In one embodiment, the drive shaft connector may releasably engage the drive train connector by passing the guide tube through a central aperture of the drive shaft connector and magnetically adhering to the magnet such that the anti-slip cogs are offset and engaged. In operation, rotational movement may be imparted to the drive train by any conventional drive system whereby drive train connector transfers rotational movement to the drive shaft connector by engaging complementary anti-slip cogs on each connector. The drive shaft may be fixedly connected to the drive shaft connector by any conventional methods, such as welding laser welding, soldering, brazing, adhesive bonds and the like. Rotational movement imparted to the magnetic coupler assembly by the drive train is effectively transferred to the drive shaft and the cutter assembly. The magnetic coupler is designed to accommodate the guide wire. The drive train and all distal components may be provided with a central aperture to receive the guide wire, thereby permitting free axial translation of guide wire through the entire system.
• Some embodiments of the present invention may include additional features, such as aspiration and/or infusion portals, by which aspirate may be removed from and infusion materials may be introduced into various catheter systems. For example, a wide variety of “quick-connect” devices are well known in the art and may be used in the present invention and may also be adapted for specific use within the removal system. The connecting devices may provide a fluid-tight seal. For example, a connector may form a fluid-tight seal with a coupler recess of the motor assembly housing, which may be further connected to one or more catheters and/or sheaths of the present invention. This design, and any similar variations, may enable the operator to quickly and efficiently switch components of the present invention.
• A conduit for aspirate may be integrated into the cutter assembly drive shaft by bonding or shrinking a polymer onto the outer and/or inner surface(s) of the coil drive shaft. TEFLON® brand polytetrafluoroethylene (by e.i. DuPont De Nemours and Company Corporation located in Wilmington, Del.) may be an especially useful polymer for sealing the cutter assembly drive shaft. For many applications of the material removal system of the present invention, a non-compressible multi-filar metallic coil drive shaft without an integrated aspirate conduit may be used. The drive shaft may also have one or more conduit(s) for aspiration and/or infusion being provided internally or externally coaxial with the drive shaft, or a bi-axial conduit. A hollow and flexible drive shaft may be constructed from materials that provide enhanced system flexibility and guidance properties.
• In one embodiment of the present invention, a self-dampening drive shaft having a “multi-helical” design is provided, herein referred to as a multi-helical drive shaft or simply as a drive shaft. It is desired to make the drive shaft lengthwise so that no unusual loading of the distal cutter system occurs regardless of the direction of the rotation. Depending upon the “lay” of the helical structure and the direction of rotation, helical drive shafts undergo transitory expansion or contraction caused by unwinding or cinching of the helical structure in response to the applied torque, resulting in potential axial loading of the cutting device bearing system. As shown inFIG. 21,multi-helical drive shaft410 has adjoining sections of “left-lay” and “right-lay”helical configurations412 and414, respectively, and each section may be of substantially equivalent length. The “left-lay” and “right-lay”sections412 and414 may be arranged along the longitudinal axis ofmulti-helical drive shaft410 in any operable configuration, such as, but not limited to, essentially half the drive shaft length being one continuous length of one lay and the remaining substantially equal length being one continuous lengthy of opposite lay; or a plurality of alternating sections of opposite lay sections of any length, such that, in sum, the multi-helical drive shaft is substantially half left-lay and half right-lay.
• A multi-helical drive shaft having adjoining lengths of oppositely wound helical coils dampens the movement of adjoining, counterpart section(s). For example, upon counterclockwise rotation, left-lay coiled section(s) of the drive tend to unwind, causing axial displacement in the distal direction, while the right-lay section(s) of the drive shaft will tend to contract, causing axial displacement in the proximal direction. The combined opposing forces and actions effectively cancel the axial movement of each respective section, resulting in negligible axial loading of the distal expandable cutter. The multihelical drive shaft may have any number of opposite-lay sections, provided that opposite-lay sections are properly matched to effectively dampen the axial movement. The opposite lay coils412 and414 may be joined together directly, or, as shown inFIG. 21, by means of a fixed connection to aconventional coupler416 interposed between the coils. Such fixed connections may be provided, for example, by welding, soldering, brazing, adhesives and the like.
• The cutter assembly may comprise one or more cutters and one or more distinct types of cutter elements. For example, a dual cutter configuration provide a distal, fixed diameter cutter and a proximal, adjustable diameter cutter. As described in greater detail below, one embodiment of material removal system of the present invention has the ability to remove material from the interior of a lumen, such as a blood vessel or gastro-intestinal lumen, in a two-step process using an expandable cutter assembly. In some methods of using a dual cutter assembly, the cutter assembly is rotated and advanced to remove occlusive material in an initial “pilot pass” in which the distal, fixed diameter cutter is the primary cutter, and the proximal, expandable cutter is in a smaller diameter condition. Following one or more pilot passes, the proximal, adjustable diameter cutter may be adjusted to a larger diameter condition and the dual cutter assembly may be advanced so that the adjustable diameter cutter, in its expanded condition, cuts an even larger volume of occlusive material. Debris and fluids are usually removed from the site, such as by aspiration. Following removal of desired materials, the proximal, adjustable diameter cutter may be adjusted to a smaller diameter condition and the cutter assembly may be withdrawn from the site. This method, using the material removal system of the present invention, obviates the need for the operator to remove and replace, or interchange, cutter assemblies during a material removal operation to provide cutters having different diameters and material removal capabilities.
• An enlarged depiction of one example of a cutter assembly is shown inFIG. 1 having acutter assembly housing46 provided at distal end of guidingcatheter40 or primary sheath. In one embodiment, thecutter assembly housing46 may be provided as a continuous, enlarged section of guidingcatheter40 or a primary sheath that accommodatescutter assembly42. For example, the hollow interior ofcutter housing46 defines aninterior space47 in which thecutter assembly42 resides when axially retracted in a proximal direction.Interior space47 ofexpandable cutter housing46 may be continuous with the lumen of a primary sheath or the lumen of guidingcatheter40, creating a conduit for the flow of various fluids during aspiration and/or infusion. In another embodiment, the distal end of a primary sheath or the guiding catheter is operably connected to a flared coupling that serves as a cutter assembly housing.
• The cutter assembly of the present removal system may be any of a variety of devices having one or more hard and/or sharp cutting surfaces for cutting, fragmentizing, pulverizing, ablating, scraping, grinding or otherwise reducing the size of and/or separating occlusive matter from beneficial matter, such as the walls of a blood vessel, in proximity to the occlusive material. For example, the cutting surfaces may include one or a combination of blade(s), spring(s), metallic or ceramic surfaces having an edge and/or an abrasive surface. Abrasive surfaces may be provided by affixing fine and hard materials, such as diamond grit, etc., to cutting surfaces. The cutter assembly may have blades that are chamfered at one or both of their proximal and distal ends to render them atraumatic to resilient beneficial tissue.
• As illustrated inFIGS. 2 and 3, a distal end ofdrive shaft25 may be fixedly connected to the cutter assembly, such as anexpandable cutter assembly42. One embodiment ofexpandable cutter assembly42 may be a dual cutter assembly comprising aproximal bushing150, an adjustable cutter housing acentral block152 and a plurality of cuttingmembers154, a fixed diameterdistal burr156 and anassembly tube158.
• Some exemplary materials for the components of the cutter assembly include metals, metal alloys and ceramics and cermet materials, such as but not limited to, various types of stainless steels, such asseries300 and/or400, vanadium steel, nickel-titanium, titanium, titanium-containing metals and oxide ceramics. In general, cutter blades are constructed from hard materials and may be treated to impart greater hardness. Cutter blades constructed from a material that is harder than the materials used to construct stents are generally provided. Cutter assemblies of the present invention and the accompanying drives, catheter assemblies, etc., may be constructed having various sizes and configurations to accommodate different material removal applications. For example, expandable cutter assemblies may be provided in several diameters, ranging from less than 2 mm to 5 mm or more. In particular, the expandable cutter assembly may have a contracted diameter/expanded diameter of 2.25 mm/2.75 mm, 2 mm/2.75 mm and/or 1.5 mm/2.0 mm, or the like.
• In the specific embodiment illustrated inFIG. 2, a hollowflexible conduit catheter94 is coaxially disposed within the lumen of a primary sheath.Conduit catheter94 may be constructed from plastic such as polyvinyl chloride (PVC), TEFLON® brand polytetrafluoroethylene, Nylon or another polymer, or from a helical metal spring wire encased in a suitable polymer to provide a sealed conduit.Conduit catheter94 may provide a conduit for aspiration and have sufficient structural integrity to withstand the internal vacuum pressure during aspiration, as well as sufficient flexibility to permit guidance and axial movement of the cutter assembly in an atraumatic manner. In some embodiments,conduit catheter94 is a coiledmetallic catheter106 having a tightly associated flexibleouter sheath108, such as a TEFLON® sheath which has been “shrink-wrapped” onto the outer surface of the coiled metallic catheter. The present invention may also include other suitable materials for encasing the stainless steel coiled catheter, such as any flexible, biocompatible plastic or synthetic material. A sheathing layer may also be applied using techniques other than heat shrinking, such as, but not limited to, plastic extrusion techniques. For example, according to some embodiments,conduit catheter94 has an outer diameter of from about 0.045 to 0.060 inch and an inner diameter of from about 0.035 to 0.050 inch. The lumen formed betweenconduit catheter94 and driveshaft25 usually serves as a conduit for fluids and particulates during aspiration and perfusion.
• Adistal end100 ofconduit catheter94 is fixedly connected to aproximal section102 of a first slip seal/bearing assembly104. Slip seal/bearing assembly104 is a mechanism forcoupling conduit catheter94 toexpandable cutter assembly42, while permitting free rotation ofcutter assembly42 around a central axis and forming a fluid-tight junction betweenconduit catheter94 andcutter assembly42.Outer sheath108 ofconduit catheter94 extends to partially cover the outer wall of the proximal section of slip seal/bearing assembly104. Adistal section110 of first slip seal/bearing assembly104 is in close association with thecollar section112 ofproximal bushing150, thereby forming the slip seal/bearing junction104.Collar section112 ofproximal bushing150 is continuous withbody section118 ofproximal bushing150.Proximal bushing150 has an axially-alignedcentral aperture114, which enlarges atcollar section112 to form aproximal bushing conduit116. The axially-alignedcentral aperture114 receivesassembly tube158.Proximal bushing150 also possesses a first series of receivingapertures120 radially arranged aroundcentral aperture114 for receivingproximal end122 ofrod section124 of cuttingmembers154. The present invention contemplates proximal bushings having various configurations, such as but not limited to, a bushing having raised ridges that act as a cutting or grinding burr for removing material when the cutter assembly is operated in a retrograde axial direction.
• As shown inFIGS. 3 and 4, an expandable type of cutting assembly has cuttingmembers154, i.e. blades, which may comprise arod section124, having aproximal end122 and adistal end126. Along the middle portion of each rod section, ablade128 having abeveled edge130 for cutting may be mounted. It is understood that thebeveled edge130 of the blade(s) may be of different configuration to facilitate the removal of occlusive material.Rod sections124 of cuttingmembers154 may be seated ontocentral block152.
• Central block152 may support a plurality of cuttingmembers154 and may provide acentral lumen136 for receivingassembly tube158.Central block152, having a proximal132 and a distal134 end, may also serve as a control mechanism for the axial rotation of cuttingmembers154, which is explained in detail below.Central block152 often incorporates a plurality of raisedspines138 tangentially arranged around its central axis. Raisedspines138 may have asupport face140 and astop face142. The junction between raisedspines138 forms a seat for receivingrod sections124 of cuttingmembers154. Aproximal end132 ofcentral block152 may be permanently fixed to adistal face144 ofproximal bushing150 using any conventional means, including but not limited to, welds of all types, mechanical attachments and adhesives.
• In some embodiments of the present invention, and as depicted in the accompanying drawings, six cuttingmembers154 are mounted on a central block configured to support six cutting members. Cuttingmembers154 are seated in the junctions of raisedspines138 ofcentral block152, with theblade section128 of each respective cuttingmember154 contacting thesupport face140 of the corresponding raisedspine138 ofcentral block152. Thedistal end126 of eachrod section124 of cuttingmembers154 extends distally beyond thedistal end134 ofcentral block152 to engage theproximal face160 of adistal cutter156 having a fixed diameter.
• As shown inFIGS. 1,2,3,5 and6, the fixed diameterdistal cutter156 typically may have a frusto-conical cross-sectional configuration and a series of raised cuttingflutes148, i.e. blades. The fixedcutter156 may be provided distally to an adjustable cutter or without another cutter in the cutter assembly.
• The raised cuttingflutes148 of fixedcutter156 and/or the cutting members of an expandable cutter may operate according to the principle of differential cutting and operate to cut, scrape or grind occlusive matter, without damaging other tissues in proximity to the occlusive material, such as internal blood vessel surfaces. In operation, these blades make contact with the vessel wall in order to efficiently remove the target matter along the vessel wall; however, the vessel surface remains undamaged.
• The blades may be configured and/or located on the cutter assembly such that they have relatively small blade angles of attack that promote efficient differential cutting. The blade “angle of attack”, as referred to herein, is the angle between the leading face of a blade and a tangent to a circle formed by the tips of the blades while the cutter assembly rotates about a central axis, i.e. the longitudinal axis, of the cutter assembly. Angles of attack of differential cutting blades of the present invention are preferably acute. That is, they are less than 90°. The tangent line to the circle formed by the tips of the blades is on a plane that is generally parallel to the longitudinal axis of the cutter assembly, which is also often the longitudinal axis of the catheter coupled to the cutter assembly. Thus, this tangent is not on a plane that extends through the axis of rotation. In some embodiments, the plane of the cutter blades is radial to the axis of the drive shaft. The “angle of attack” is also referred to herein as “blade angle”.
• One example of the use of an acute angle of attack for a cutter assembly, according to the present invention, is depicted inFIG. 7B.FIG. 7A depicts a side view of one embodiment ofcutter assembly600.FIG. 7B is a cross-sectional view through line (B to B′) of the head ofcutter assembly600 viewed from the proximal to distal ends of the blades. Each of theblades602 is positioned to form an acute blade angle (α). The blade angle (α) is defined by the angle of intersection of the surface of a blade's leadingface606 andtangent line634, which is tangent to acircle636 formed by theoutermost tips638 of theblades602. A leading face is a surface of the blade that faces the direction of the rotation and, in use, that contacts the material during cutting in the direction of rotation C to C′. The opposite facing surface on the opposite side of the blade is a trailing face, which is positioned to face the opposite direction of rotation and does not contact the matter when the cutter assembly is rotated in the direction of rotation from C to C′. Thetangent line634 is in a plane to thecircumference636 of the cutter assembly defined by the outer edge of all of the blades at the blade'soutermost tip638.
• In the cutter assembly and blade embodiment illustrated inFIG. 7B, both faces of eachblade602 may serve as leading faces, depending on the direction of rotation of the cutter assembly. Both faces ofblades602 form an acute blade angle, defined by the angle of intersection of the surface of the blade's face and a line tangent to a circle formed by the blades tips, and both faces ofblades602 may form cutting surfaces, depending on the direction of rotation of the cutter assembly.
• Acute blade angles of cutting assemblies of the present invention should be sufficient to permit differential cutting and effectively separate the undesirable matter from the beneficial material in proximity to the undesired matter. Oftentimes, the use of a smaller, i.e. more acute, blade angle results in a scraping action of the cutter assembly rather than a slicing action, which is observed with larger angles, and particularly blade angles greater than 90°. Preferred blade angles for differential cutting purposes are typically acute, for example, less than or equal to 90°. Acute blade angles are preferably greater than 10° and less than 90°, and also may be greater than about 30° or 45° or 60° and less than 90°. In still other embodiments, the blade angle may be between about 45° to less than or equal to about 75°, and in another embodiment is less than 70°.
• An example of a prior art cutting device that has an obtuse blade angle is shown inFIG. 7C, wherein cutting movement is in a direction A to A′. Theblade602 has aleading edge630, a trailingedge631 and a flatouter face633. The blade attacks the tissue at a tangent632 to a circle. In some embodiments, the tangent may represent a tissue surface and the circle may represent a round lumen. In any case, although an acute angle β is formed between theouter face633 and tangent632, the blade angle of attack α, as defined herein, between theleading edge630 and tangent632 is obtuse. It is this larger obtuse blade angle, e.g. larger than 90 degrees, that result in an increasingly aggressive cutter assembly that is more likely to cut healthy tissue.
• The larger, obtuse blade angles used in prior devices also may require the use of thinner and less robust blades. It has been found through the present invention, however, that a an acute blade angle, e.g. less than 90°, provides safe separation of undesired from desired material, particularly in applications where the undesired material comprises as calcified matter, e.g. bone, atherosclerotic material, thrombus, and similar materials. The acute blade angles used in cutter assemblies of the present invention also do not harm healthy tissue, such as skin, healthy vessel walls, and the like. This enhanced differential cutting capability also allows a fewer number of blades to be used in a cutter assembly than the number that may be required by other cutting devices having larger blade angles. The presence of fewer blades may also allow for larger ports to be provided between the blades. In some instances the cutter assembly has the ability to rotate in both clockwise and counterclockwise directions.
• The blade angle may be optimized to provide the desired aggressiveness when rotated in one direction, and likewise when rotated in the opposite direction. Furthermore, the exemplary cutting assemblies with blade arrangements described herein are not intended to limit the scope of cutting assemblies and arrangements of blades that may be employed with the inventive blade angles for differential cutting. It is understood that other embodiments of cutting assemblies, which may have blades arranged in various fashions, and that have acute blade angles for differential cutting are within the scope of the invention.
• In one embodiment, where the cutter assembly changes directions of rotation to cut, e.g. clockwise to counterclockwise, or visa-versa, the leading face and trailing face of the blade may also switch sides of the blade such that the leading face always faces the direction of rotation. In this embodiment, opposing faces of a blade may have a profile to provide for an acute blade angle for differential cutting. Further, in this case, these opposing sides may have the same profile such that they provide the same blade angle, or the profiles may be different such that the blade angles of each side are different. In addition, where for a multiple cutter assembly having an expandable cutter and fixed cutter, the blades of individual cutters may have opposite sides of the blades of each cutter serving as the leading faces, where the expandable cutter rotates in one direction to cut and the fixed cutter rotates in the opposite direction to cut.
• One example of the use of a cutter assembly in approaching a tissue surface with an acute angle of attack, according to the present invention, is depicted inFIG. 8A. The cutting head is rotated such that each blade sequentially contacts the surface of the target matter and usually also contacts the support surface at ablade contact point635. The leadingsurface630 of theblade602 takes an acute or narrow approach to thesurface632 of the target matter and/or support surface. The scraping or cutting motion, produced by rotation of the blades, proceeds in a direction A to A′ in the direction of the leading face. The support surface that contacts the target matter deforms to reposition out of the way of the blade edge. In this manner, the beneficial material of the supporting surface remains unharmed from the blade even though the blade may move along the surface of the beneficial material.
• The dislodged matter may be withdrawn by aspiration through ports of the cutter assembly to remove the matter from the body cavity. Unlike some prior blades that are designed with blade angles relative to the longitudinal plane extending through an attached catheter, e.g. axis of rotation, such that the blades may not abrade the matter close to the surface of beneficial material, e.g. vessel wall, touching the matter to be removed, but rather may cut matter in front of the beneficial material. By contrast, the present invention cutter assembly is designed to contact the beneficial material in order to scrape or cut the matter from the surface of the beneficial material. Still, other prior art references describe blades that are placed at large angles, increasing the risk of damaging elastic material.
• An example of one prior art cutting device is depicted inFIG. 8B, wherein the cutting movement is in a direction A to A′. Theblade602 has a leadingface630 that is positioned with a wide approach to thesurface632, i.e. greater than 90 degrees, to thesurface632. It was previously believed that the blade must be approach a surface at a large angle, similar to a razor's edge, in order to sufficiently abrade matter. However, it has now been found through the present invention that this wide angle approach may cause the blade to incise into the issue surface as well as the overlying unwanted matter. The present advantages of a narrow approach were not previously recognized.
• In some embodiments of cutting device, the blades of either one of the cutters or all cutters in a multiple cutter assembly, e.g. a fixed cutter and other cuttingmembers154, may be designed and arranged to function according to the principle of differential cutting, to preferentially remove occlusive matter while being atraumatic to the more resilient vessel walls. In some embodiments, proximal and distal portions of cuttingflutes148 are chamfered to render them atraumatic.
• It is understood that the fixed diameter cutter may be of any suitable configuration, and numerous fixed diameter cutter configurations are known in the art. The dimensions of the fixed cutter vary depending upon the particular application and embodiment but, for intravascular applications, the largest outer diameter of the fixed diameter cutter is generally in the range of 1.5 mm to 2.5 mm.
• As shown inFIG. 3, fixedcutter156 may be provided with acentral aperture146, which defines a surface for mountingassembly tube158 and receiving the guidewire. A second series of receiving apertures may be present inproximal face160 of fixedcutter156. The receiving apertures may be radially arranged around the central lumen, and complementary to the first series of receivingapertures120 located ondistal face144 ofproximal bushing150. The receiving apertures receive distal end(s)126 ofrod sections124 of cuttingmembers154. In certain embodiments of the present invention, the fixed cutter may be fixedly joined by a connection means to the central block. This permanent, fixed connection may be achieved by any conventional means, such as a weld, e.g. a laser-weld, soldering, brazing or an adhesive bond between thedistal end134 ofcentral block152 andproximal face160 of fixedcutter156.
• Assembly tube158 may serve as a connecting means for thecutter assembly42, as well as a bore for receiving a guidewire and a conduit for fluids and debris during aspiration and/or infusion.Assembly tube158 may comprise abody section166, aproximal end168 and a distalflanged cap section170 having acentral aperture172 definingguidance passage174. Aproximal end168 ofassembly tube158 may traversecentral aperture146 of fixedcutter156, andcentral lumen136 ofcentral block152, andcentral aperture144 ofproximal bushing150 to fixedly connect with the distal end ofdrive shaft25.Distal cutter156,central block152 andproximal bushing150 may be fixedly joined to the assembly tube by any conventional connection means, such as but not limited, to welds, adhesives and mechanical connection means, such as compression fitting. The components of the cutter assembly may be drawn in and held in tight association by the distalflanged cap section170 ofassembly tube158.
• The present invention often has additional features which permit the aspiration of fluids and small particulates from the vessel lumen, as well as perfusion of liquids, such as physiologically balanced salt solutions, diagnostic or therapeutic substances, and/or contrast media into the intralumenal space in proximity to a material removal site. In general, as illustrated inFIGS. 2 and 3, the inventive device may have a primary aspiration means through the primary sheath, and a secondary aspiration means through a plurality of ports incutter assembly42 andlumen186 formed betweenflexible conduit catheter94 and driveshaft25, which, in some embodiments, is continuous with lumenal space of primary sheath. Proximal end of the primary sheath may be operably connected to a vacuum control unit18 and may incorporate one or more flow-regulation systems, such as valves, seals, manifolds and the like. Upon actuation of the vacuum assembly and opening of the flow-regulation means, a vacuum may be created in the lumen formed by primary sheath that draws fluids and particulates from the material removal site and deposits fluids and associated debris in an aspirate collection means.
• A secondary aspiration and perfusion system is provided using a plurality of ports incutter assembly42 to draw fluids and particulate debris throughlumen174 ofassembly tube158, providing a conduit which is continuous withlumen186 offlexible conduit catheter94 and a lumen of a primary sheath. As illustrated inFIGS. 2-6,cutter assembly42 may be provided with a plurality of ports inassembly tube158, fixed diameterdistal cutter156 andcentral block152.Ports194,194′, etc., indistal cutter156 communicate withassembly tube ports196,196′, etc. In some embodiments,distal cutter ports194,194′, etc. are interspaced circumferentially around thedistal cutter156.Central block152 may have a first plurality of circumferentially interspacedports204,204′, etc., in the distal portion, and a second plurality of circumferentially interspacedblock ports206,206′ etc., in the proximal portion, which may be arranged in a staggered configuration. The first plurality ofports204,204′, etc. may define a lumen that is in alignment and continuous with the second group ofassembly tube ports198,198′ etc., and the second plurality ofports206,206′ etc. may define a lumen that is in alignment and continuous with the third group ofassembly tube ports200,200′ etc., such that under vacuum conditions, fluid and particulates flow throughcutter ports194,194′ etc.,central block ports204,204′ and206,206′ etc. as shown byarrow208 and210, respectively. Fluid and particulates may continue to flow throughassembly tube lumen174 to a third group ofassembly tube ports202,202′ etc., to lumen186 ofconduit catheter94, as shown byarrow212. The infusion of fluids may be provided by switching to an infusion source and reservoir, and reversing flow so that fluid flows throughcutter assembly42 in a direction opposite that ofdirectional arrows208 and210.
• Operationally, the intralumenal material removal system is usually introduced into the body by way of a lumen, such as a blood vessel, using techniques that are well known in the art. Typically, an access sheath is employed to access the desired vessel at the point of introduction. Through an installed access sheath, the guiding catheter, which may house theguidewire11,cutter assembly42 and other associated components and serve as a delivery vehicle for those components, may be navigated and advanced to the desired site of material removal. In general, the guidewire brake may be released and distal end of guidingcatheter40 may be axially translated to a location proximal to the desired material removal site. Guidance and navigation of guiding catheter and associated cutter assembly may be facilitated by the infusion of fluids, such as contrast media, to monitor the progress of the guiding catheter. The cutter assembly, or sub-components thereof, may be coated with a radiopaque material such as gold, platinum, inks and the like, to render the expandable cutter assembly radioscopically visible and to assist a medical professional in guiding and positioning the cutter assembly relative to an occlusion.
• Once the guiding catheter is positioned, the flexible conduit catheter, or other internal catheter, may be extended distally to facilitate placement of the cutter assembly near the occlusion. The distal end ofcutter assembly42 may be positioned at the proximal boundary of the occlusion, whereupon drive system24 may be actuated and driveshaft25 andcutter assembly42 may be rotated. In the use of one embodiment of a dual cutter assembly illustrated in the accompanying figures, particularly inFIGS. 5A and 5B,cutter assembly42 is often initially rotated in a counter-clockwise direction and advanced so that distal, fixeddiameter cutter156 cuts and abrades the occlusion. Initial rotation ofcutter assembly42, contactingdistal cutter156 with the occlusive material, is capable of removing occlusive material having a cross-sectional area roughly equivalent to the largest outer diameter ofdistal cutter156 and diametercentral block152/cuttingmembers154 assembly in its contracted state. Initial “pilot passes” remove part of the occlusive material and subsequent passes with the cutter assembly in the expanded configuration remove additional material. Of course, alternative embodiments of the present invention may be configured to operate in the opposite rotational direction described above, such that clockwise rotation provides a contracted state and counter-clockwise rotation expands the cutter assembly.
• As the fixed diameter cutter assembly is rotated and advanced to remove occlusive material, fluid and debris particulates may be aspirated using the primary and secondary aspiration mechanisms described above. It may be desirable to alternate between advancing and retractingcutter assembly42 to facilitate the aspiration of particulates, especially particulates which are too large to pass throughports194,204,206, etc. incutter assembly42. For example, retractingcutter assembly42 in a retrograde direction (i.e. proximally) withincutter housing46 ofprimary sheath40 during aspiration often creates a laminar-like flow, thereby more effectively drawing fluid and particulates intohousing46 and permitting particulates to be further broken down by the grinding action of the rotating cutter assembly withinhousing46. Larger particulates may thus be broken down to a size that can be withdrawn, with fluids, throughaspiration ports194,204,206, etc.
• In further use of a dual cutter assembly, once one or more initial pilot-passes are complete, the expandable cutter assembly may be retracted in a retrograde direction to the proximal boundary of the occlusion and the direction of rotation of the expandable cutter assembly may be reversed. Reversing the direction of rotation from a counter-clockwise direction to a clockwise direction causes cuttingmembers154 of expandable cutter assembly to open to an expanded configuration, as illustrated inFIGS. 6A and 6B. Specifically, as theexpandable cutter assembly42 is rotated in a clockwise direction, centrifugal forces of rotation combine with hydrodynamic and frictional forces between the surrounding fluid within the lumen andblades128 of cuttingmembers154,cause cutting members154 to rotate around a central axis, as defined byrod sections124 of cuttingmembers154. Cuttingmembers154 may rotate freely within the first receivingapertures120 and second receiving apertures164 inproximal bushing150 anddistal cutter156, respectively. Cuttingmembers154 rotate from a tangential orientation, in whichblades128 are in contact with the respective support faces140 of raisedspines138 of central block152 (i.e., the contracted configuration) to a radial orientation in whichblades128 of cuttingmembers154 are in contact with stop faces142 of raisedspines138 of central block152 (i.e., the expanded configuration). Stop faces142 of raisedspines138 check the rotational movement of the cuttingmembers154, as well as provide support toblades128 of cuttingmembers154 while in the expanded configuration during operation. Movement of the cutting members to the radial configuration increases the overall outer diameter of the cutter assembly. For example, in select embodiments, the outer diameter of the expandable cutter assembly in the contracted configuration may be approximately 2 mm, and the cutter assembly may be expandable to an outer diameter of approximately 2.75 mm. As previously described, the present invention may be designed in a wide range of sizes to accommodate various applications.
• While in the expanded configuration, the expandable cutter assembly may be axially translated alongguidewire11 to retrace the pilot-pass made through the occlusion, whereupon beveled edges130 of cuttingmembers154 engage the occlusive material, removing a larger volume of occlusive material. As previously described, aspiration may be provided throughout the operation of the expandable cutter assembly to effectively remove the particulate debris dislodged during cutting and grinding of the occlusive material.
• After sufficient occlusive material has been removed, the expandable cutter assembly may be contracted by engaging the drive system to rotatecutter assembly42 in the opposite direction, i.e. for the purpose of this example, in a clockwise direction. The centrifugal, hydrodynamic and frictional forces may again act onblades128 of cuttingmembers154, causing the cutting members to rotate around a central axis, as defined byrod sections124 of cuttingmembers154. Cuttingmembers154 rotate from a radial orientation, in whichblades128 of cuttingmembers154 are in contact with stop faces142 of raisedspines138 of central block152 (i.e., the expanded configuration) to a tangential position in whichblades128 are in contact with the respective support faces140 of raisedspines138 ofcentral block152. Support faces140 of raisedspines138 stop the rotational movement of the cuttingmembers154, as well as provide support toblades128 of cuttingmembers154 while in the contracted configuration. While in its contracted state, thecutter assembly42 may be retracted into the primary sheath or guiding catheter for removal from the body or further advanced distally alongguidewire11 to perform additional operations. FIGS.6 and9-11 present one embodiment of the present invention. Wherever appropriate, the same reference numbers have been employed to describe the same or similar elements. In general, the dimensions, materials, method of operation and the like used to describe the previous embodiment apply equally to all embodiments presented herein unless stated otherwise.
• FIG. 9 depicts an alternative embodiment of a dual cutter assembly according to the present invention comprising at least oneflexible conduit catheter94′ in which driveshaft25, such as a multi-helical drive shaft, runs coaxially within its internal lumen. Aproximal encasement340 may fixedly connectflexible conduit catheter94′ to a secondary segment offlexible conduit catheter342, which in turn may fixedly connected to adistal encasement344.Distal encasement344 may form a slip-bearing fitting with aproximal cap346, thereby permitting free rotation ofdrive shaft25 andcutter assembly42′ within coiled metallic catheter. As with previous embodiments,cutter assembly42′ may comprise acentral block152′, a fixed diameterdistal cutter156′ and a plurality of cuttingmembers154′.
• As illustrated inFIGS. 10 and 11,drive shaft25 may be provided with retainer assembly ormechanism338 for interconnectingdrive shaft25 andflexible conduit catheter94′. Any conventional assemblies or mechanisms may be utilized, such as aretainer348 having afirst end350 fixedly connected toflexible conduit catheter94′ and asecond end352 fixedly connected to afirst end360 of secondary segment offlexible conduit catheter342, by any conventional methods, such as by welding, laser-welding, soldering, brazing, adhesive bonds and the like.Retainer348 may operate in conjunction with one or more thrust bearings to facilitate cooperative axial translation ofdrive shaft25 andflexible conduit catheter94′ in either an antegrade or retrograde direction. A first thrust bearing356 may fixedly connected to driveshaft25 proximal to center section ofretainer354, and a second thrust bearing358 may fixedly connected to driveshaft25 distal to center section ofretainer354 in such a manner as to bring first356 and second358 thrust bearings in close or tight association withcenter section354 ofretainer348. Driveshaft25 may freely rotate within central aperture ofretainer348. Retainer assembly may be enveloped by some tubular sheath, such asproximal encasement340 to add additional strength and provide a relatively smooth profile toflexible conduit catheter94′.
• Notably,retainer assembly338 andproximal encasement340 may be located an operable distance fromcutter assembly42′. “Operable distance,” as used herein, is defined as a distance which permits secondary segment offlexible conduit catheter342 and associatedcutter assembly42′ to retain sufficient flexibility to effectively maneuver within intralumenal spaces, particularly along curved, arched and/or branched sections of lumenal bodies. The distance betweenretainer assembly338/proximal encasement340 anddistal cutter assembly42′ may be less than 1 cm to over 20 cm.
• Cutter assembly42′ may be fixedly connected to driveshaft25 while permitting free rotation withinflexible conduit catheter94′. Driveshaft25 may be fixedly connected to aproximal cap346, which has adistal flange section366 fixedly connectedcentral block152′. This arrangement transfers rotational movement fromdrive shaft25 tocutter assembly42′.Proximal cap346 may be provided with a central aperture for receivingguide wire11, and a number of cut-away sections to create one or more accesses continuous with the lumenal space within all sections offlexible conduit catheter342,94′. This lumenal space serves as a conduit for aspiration and infusion materials and is continuous with the various ports ofcutter assembly42′. A slip seal/bearing assembly368 may be created at the connection between distal encasement and flange section ofproximal cap366 thereby permitting free rotation ofdrive shaft25,proximal cap346 andcutter assembly42′ withinflexible conduit catheter94′,342 without imparting rotational movement toflexible conduit catheter94′,342, which minimizes unnecessary trauma to the surrounding tissues.
• The embodiments depicted inFIGS. 9-11 have a number of uniquely distinguishing features. As shown inFIGS. 10,11 and12,central block152′ may be fitted with any suitable number of cuttingmembers154′, such as 8 or less. This embodiment shows a central block having 5 cutting members, but, depending upon the application and overall dimensions of the cutter assembly, greater or fewer than 5 cutting elements may be employed.FIG. 12 showscentral block152′ having a plurality of receivingslots380 for receivingrod sections124′ of cuttingmembers154′. Cuttingmembers154′ may be formed from interconnected rod and blade members, or often machined from one integral piece. As with the previous embodiment, cuttingmembers154′ are provided withbeveled edges130′, such that the principles of differential cutting apply. It is understood that any suitable differential cutting angle may be utilized forbeveled edge130′ in addition to those depicted in the figures. Acentral aperture136′ may be provided running along the longitudinal axis ofcentral block152′ to permit free axial translation ofguide wire11 and/or other components, as well as serve as a conduit for aspiration and infusion. A plurality ofports382 may be provided incentral block152′ which are continuous withcentral aperture136′ and lumen offlexible conduit catheter342,94′, further providing aspiration capabilities tocutter assembly42′. This particular embodiment provides a greater number ofports382 incentral block152′, thereby increasing aspiration and infusion efficiency.Distal face134′ ofcentral block152′ may be fixedly connected toproximal face160′ of fixed diameterdistal cutter156′ by any conventional methods, such as by welding, e.g. laser welding, soldering, brazing, adhesive bonds and the like.
• One aspect of the present removal system relates to improved cutting assemblies and includes a cutter assembly that is especially useful in differential cutting. In some embodiments of the present invention, multiple blades are provided to dislodge and/or ablate the intracorporeal matter. These blades may be positioned at acute blade angles for attack, e.g. less than 90 degrees, for enhanced differential cutting abilities. In addition, one or more port(s) may be included as large openings between the blades to permit highly efficient removal of debris. The position, shape and/or size of the blades and ports promote highly efficient differential cutting and debris removal.
• As more clearly illustrated inFIGS. 13A and 13B,cutter156′ may be generally of tapered, oblong, conical or frusto-conical design, or any suitably balanced configuration, and is usually provided with a plurality of raised “arch-like” cutting flutes orblades148′ radiating fromcentral aperture146′ tobody388 ofcutter assembly156′. As with all cutting members, blades and cutters described herein, this particular embodiment of a cutter also operates by differential cutting. Additionally, proximal and distal aspects of cutting flutes orblades148′ may be chamfered to render them atraumatic.
• As shown inFIGS. 13A and 13B,cutter assembly156′ may be provided with a plurality of port-like cutouts for aspiration and infusion. In the context of this particular embodiment, port-like cutouts may also be referred to as ports. Each pair of cuttingflutes148′ may be cut away to provide anaspiration cutout390, which form an internal cavity that is continuous withcentral aperture136′ of central block. This arrangement may provide an aspiration and infusion conduit to the most distal end of the cutter assembly. The design and arrangement of cuttingflutes148′, andaspiration cutouts390 create an open configuration providing substantially maximal cutout surface area, which allow a greater volume of material to be aspirated from the situs of operation. In addition,cutter assembly156′ may have any sort of cutting and/or grindingelements394 associated withbody388 ofcutter assembly156′ to further facilitate removal of occlusive material.
• Another example of one such a cutter assembly that is designed for differential cutting is depicted inFIG. 14.Cutter assembly600 comprises a plurality ofblades602 arranged in a radially symmetrical configuration to ablate. In one embodiment, as shown, the blades extend along a plane that is generally parallel to the center of axis of the cutter assembly.Ports614 are defined, at least in part, by the gaps between theblades602. The ports open from the exterior of the cutter assembly and extend to the internal head, to receive ablated intracorporeal matter and/or fluid. The gap may be formed between ablade facing surface604 on each blade presented at least substantially in front of and spaced apart from an adjacent and opposing blade's facing surface, such as leadingface606.
• The cutter assembly may further have adistal tip616 on its distal end and on its opposite end, aproximal end620. In some embodiments ofcutter assembly600, thedistal tip616 may have acentral bore618 through which a guide wire may be slidably engageable. In other embodiments, no guide wire is used and the distal tip does not accommodate a guide wire.
• Typically, theblade602 is also provided with anouter surface608 for contacting and cutting the matter to be removed. The outer surface may be, for example, a sharp edge. In one embodiment, the outer surface may additionally have an abrasive or cutting material, e.g. diamond grit, bonded to it. On the side opposite of the outer surface the blade may also have aninner surface610 facing an internal cavity within the cutter assembly.
• The blade may be composed of any material sufficiently durable to ablate the matter of interest and usually is a hard material. For example, the blade may comprise stainless steel, such asseries300 and/or400, vanadium steel, nickel-titanium, titanium-containing metals, oxide ceramics, etc. Typically, softer materials, such as aluminum, pure titanium or annealed stainless steel are not employed. The dimensions of the blade depend on, inter alia, the application for the apparatus, type of matter to be removed, the internal size of the head, material comprising the blade, etc. The blade is usually thick enough to be durable, yet thin enough to permit large ports to be present and, in particular, the blade may tend to be relatively thin and narrow. For example, the blade may have a cross-sectional dimension of between about 0.1 to 0.5 mm.
• For a cutter assembly composed of blades, the shape of the cutter assembly may be defined by the outer profile and arrangement of the blades. In one embodiment of cutter assembly, theproximal end620 is larger than thedistal tip616. For example, the proximal end may have a diameter that is at least twice the diameter of the distal tip, as shown inFIG. 14. The cutter assembly may also be pear-shaped, wherein the cutter assembly has its largest diameter at a portion of the cutter assembly that is close to the proximal end and, from there, tapers to the distal tip.
• Another embodiment ofcutter assembly600 is depicted inFIG. 7A, wherein rather than pear-shaped, the cutter assembly is bullet-shaped and gradually widens from a narrowdistal tip616 to itsproximal end620.FIG. 15A shows a cup-shaped cutter assembly with multiple gradualsloping blades602 from thedistal tip616 to theproximal end620. Depicted inFIG. 15B is asingle blade602 having a gradual sloping blade profile, where the blade profile gradually slopes from one end, such as the blade's distal tip622, to the other end, such as the blade's proximal end624. This gradual sloping profile of the blade is without abrupt points that may cut into wanted matter within the body as the cutter assembly is guided toward the removal site.
• In addition, in one embodiment the contour of the inner surface of a blade may at least substantially match the contour of the outer surface of the blade. For example, the inner surface may have at least considerably the same curvature as the curved profile of the outer surface. The relatively constant chord from proximal to distal ends of the blade may provide strong and thin qualities, advantageous for the present head design. Moreover, this embodiment permits large port gaps to be created between the blades. In addition, in some embodiments the blades may also have a straight and non-sweeping shape. However, in other embodiments, the blade may have any of a variety of shapes, including sweeping, suitable for its particular application.
• Although particular shapes of blades are described herein, the blades may also be of a variety of shapes and sizes have a leading face. For example, the blade may have an asymmetrical or a symmetrical curved profile. Furthermore, the blades may be arranged and positioned in the cutter in a variety of ways.
• There may be any number ofblades602 provided in acutter assembly600, as shown variously in the examples inFIGS. 16A to 16D.FIG. 16A depicts a seven blade head, whereasFIG. 16B depicts a six blade head,FIG. 16C shows a five blade head andFIG. 16D illustrates a three blade head. Generally, according to this embodiment, the greater the number of blades, the close together the blades must be placed and consequently the smaller the port size.
• As illustrated in the exemplary embodiments, the size and shape of theports614 may be defined, at least in part, by the size and shape of the blades and the spacing of the blades relative to each other. Typically, the ports comprise a large portion of the cutter assembly to permit greater aspiration of matter. A high port to blade ratio may be provided with the present embodiment without compromising differential cutting ability. In one embodiment, the total port area, i.e. surface area of the cutter assembly dedicated to ports, to total blade area, i.e. surface area of the cutter assembly dedicated to blades, is equal to or greater than about 1:1, such as about 3:1. For instance, a head that has five blades, each with a 1.75 mm O.D. tip and five ports, each port with an area of about 0.43 mm², results in a port to blade area ratio of about 3.32:1 according to the exemplary cutter assembly design. The ports according to the present invention described herein permit highly efficient aspiration of matter.
• An internal view of acutter assembly600 is represented inFIG. 17A, whereinports614 may be provided as relatively large openings that may open tointernal cavity640. This expansive size of the ports permits efficient collection of materials and may not require a pumping action caused by sweeping blades to encourage materials into the port. Furthermore, the ports of this size need not be shaped to angle from a distal surface opening and to a proximal direction that leads to the interior of the cutter assembly, as is needed in some other devices to promote movement of materials into the ports. Since the present ports may be simple openings rather than angled channels, the manufacturing of the parts may also be simplified.
• The ports usually provide communication between the removal site and the conduit of the removal system through theinternal cavity640. For example, theinternal cavity640 of the cutter assembly may be in communication with and terminate at the conduit, or other connecting component of the removal apparatus, to provide acollar642 at the proximalcutter assembly end620. The collar may have a diameter that generally corresponds to the outer diameter of a connecting component, such as a drive shaft, catheter, sheath, etc. to form a sealed pathway to and from the cutter head. At the distal end of the cutter assembly, there may be adistal tip616 that may provide for translation of the cutter assembly over a guide wire. In some embodiments, thecentral bore618 may extend from thedistal tip616 to theinternal cavity640. In some cutting assemblies, theinternal cavity640 may have a diameter greater than that ofcentral bore618.
• FIG. 17B depicts the shape of aport614 exploded fromcutter assembly600 as created by the space, i.e. gaps, betweenadjacent blades602. The profile of the port may be defined by the contour of the opposing blade's facingsurface606 and the amount of space between the blades. In embodiments that have blades closer to each other at one end of the blade, e.g. the distal end, than the other blade end, e.g. the proximal end, the ports may be advantageously at least substantially triangular in shape to enhance gathering of loose material. A tip of the triangular-shaped port may be pointing toward the cutter assembly's distal end and the facing surfaces of opposite blades may define two sides of the triangular port. The third side of the triangular port may be at the proximal end of the cutter assembly as defined by theproximal face646 of aproximal ring644 that contacts the proximal end of the blades.
• Theproximal ring644 may be positioned in contact with the proximal end of the blades in order to secure the blades in a position relative to each other. Adistal ring648 may also be provided to secure the blades and may be positioned in contact with the distal end of the blades. Oftentimes, the entire proximal ring, or at least the proximal face portion, is larger than the distal ring at its contact point with the blades.
• Theproximal ring644 may also include an outer ablation surface having a plurality ofmicro-flutes650 to contact and cut the intracorporeal matter. The micro-flutes are usually small projections on the proximal ring and may have sharp cutting edges. The micro-flutes may be used for differential cutting at the outermost diameter of the head, where contact with beneficial soft tissue may occur. In this case, the flutes may be at angles of less than or equal to 90 degrees as described above with regard to blade angles. These small flutes may also break up friction that is frequently encountered where the proximal ring does not include such flutes and is generally smooth. Ports may or may not be included between the micro-flutes.
• In one embodiment, as depicted, for example, inFIGS. 18A to 18C, thetips652 of theblades602 are extended farther than the outer diameter of theproximal ring644 and/or greater than the diameter of a connecting conduit. The blades may protrude very slightly beyond the outer profile of the ring, such as between about 0.001 and 0.010 inch, and commonly about 0.001 and 0.005 inch. These protruding blades may prevent the proximal ring from interfering with the cutting action of the blades. Furthermore, where blade angles are acute, the tips do not typically cause harm to wanted tissue when the cutter assembly is not rotated at the removal site. Because the blades cause scraping rather than cutting. Furthermore, the gentle angle of the blade tips resist cutting into tissue as the cutter assembly is guided to the removal site without rotation.
• In some embodiments of a removal system that have more than one cutter in a cutter assembly, e.g. a dual cutter assembly having a distal cutter and a proximal cutter as described above with regard to the adjustable and fixed cutters, either or all of the cutters in this multiple cutter assembly may be designed for differential cutting. The differential cutting design may be the same as or similar to the blade and port configurations described above with regards toFIGS. 14 to 18. The blade angles of the proximal cutter may be the same as, or different from the blade angle of the distal cutter. For example, the blade angle of the distal cutter and proximal cutter may be from about 45 to less than 90 degrees, and commonly the distal cutter may be about 55 to 75 degrees and the proximal cutter about 45 to 65 degrees. In another embodiment, the cutter assembly has a single cutter that is expandable and is designed for differential cutting, as described above in relation to the expandable cutter in a dual cutter assembly.
• Similar to embodiments previously described,FIGS. 19A to 19B illustratecutter assembly42′ in a contracted and expanded configuration, respectively. Cuttingmembers154′ may freely rotate withinrecesses380 ofcentral block154′ and, depending on the direction of rotation, rotate from a tangential orientation, in which blade sections of cutting members engage respective support faces140′ (i.e., contracted configuration) to a radial orientation in which blade sections of cuttingmembers154′ are in contact with stop faces142′ ofcentral block152′ (i.e., expanded configuration). Stop faces142′ check rotational movement of blade members and provide support while operating in the expanded configuration.
• The same general principles of operation described above apply to the embodiment depicted inFIGS. 20A-20B. Notably, one embodiment provides a fixed diameterdistal cutter156′ having cuttingflutes148′ that immediately engage occlusive material. Additionally, the embodiment may provide a comparatively large aspiration conduit area by virtue of the large aspiration cutouts orports390. During aspiration, aspirate and particulates are may be drawn through aspiration cutouts, orports390 ofdistal cutter156′,ports382 ofcentral block152′, as well as spaces betweencentral block152′ andproximal cap366, as depicted by arrows400,402 and404, respectively.
• It will be understood that the foregoing discussion merely illustrative of the invention and its principles. However, modifications and variations in the details of the disclosure will occur to those skilled in the art to which this invention relates and still remain within the scope and principles of the invention. It will be understood that obvious variations and modifications thereof that may be made by those skilled in the art are intended to be included within the spirit and purview of this application and the scope of the appended claims.

Claims (20)

1. An intralumenal material removal system comprising:

a rotatable drive shaft and a drive system operably coupled to the drive shaft for rotating the drive shaft; a cutter assembly coupled to the drive shaft for rotation with the drive shaft, the cutter assembly having a plurality of differential cutting blades, each differential cutting blade having an acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly of greater than 30° and less than 90°; a catheter forming a sealed lumen with the cutter assembly; an aspiration component in proximity to the cutter assembly; and an infusion system providing infusion of liquid in proximity to the cutter assembly.

2. The system ofclaim 1, wherein the acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly is between about 45° and 75°.

3. The system ofclaim 1, wherein the acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly is greater than about 60° and less than 90°.

4. The system ofclaim 1, wherein the cutting blades are raised cutting flutes provided on a fixed diameter cutter assembly.

5. The system ofclaim 1, wherein the cutting blades are provided as cutting members of an expandable cutter assembly.

6. The system ofclaim 1, additionally comprising a control unit designed to remain outside the body during a material removal operation, the control unit having an advancer system for axially displacing the rotating cutter assembly drive shaft and cutter assembly relative to the control unit.

7. The system ofclaim 1, additionally comprising an automated guidewire braking system that is automatically actuated to brake during activation of the cutter assembly drive system, thereby releasably restricting axial and rotational movement of a guidewire.

8. The system ofclaim 1, wherein the drive system is unidirectional and capable of rotating the cutter assembly at variable speeds ranging from 500 rpm to 150,000 rpm.

9. The system ofclaim 1, wherein the drive system is bidirectional and capable of rotating the drive shaft selectively in both a clockwise and a counterclockwise direction.

10. The system ofclaim 1, wherein the differential cutting blades have an abrasive surface.

11. The system ofclaim 1, wherein the differential cutting blades are chamfered at least one of their proximal and distal ends.

12. The system ofclaim 1, wherein the differential cutting blades are constructed from a material selected from the group consisting of: a stainless steel; vanadium steel; nickel-titanium; titanium-containing metals, and oxide ceramics.

13. The system ofclaim 1, wherein the differential cutting blades have an asymmetrical curved profile.

14. The system ofclaim 1, wherein the differential cutting blades have a symmetrical curved profile.

15. An intralumenal material removal system comprising:

a rotatable drive shaft and a drive system operably coupled to the drive shaft for rotating the drive shaft;

a sealed lumen formed between the rotatable drive shaft and a catheter;

a cutter assembly coupled to the drive shaft for rotation with the drive shaft, the cutter assembly having at least one differential cutting blade having an acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly of greater than 30° and less than 90°; and

an aspiration source providing aspiration through at least one material removal port in proximity to the cutter assembly and withdrawal of material through the sealed lumen.

16. The intralumenal material removal system ofclaim 15, wherein the acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly is greater than about 60° and less than 90°.

17. The intralumenal material removal system ofclaim 15, wherein the cutter assembly comprises multiple cutting members having different cutting characteristics.

18. An intralumenal material removal system comprising:

a rotatable drive shaft and a drive system operably coupled to the drive shaft for rotating the drive shaft;

a sealed lumen formed between the rotatable drive shaft and a catheter;

a cutter assembly coupled to the drive shaft for rotation with the drive shaft, the cutter assembly having at least one differential cutting blade having an acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly of greater than 30° and less than 90°; and

a liquid infusion system providing infusion of liquid in proximity to the cutter assembly.

19. The intralumenal material removal system ofclaim 18, wherein the acute angle of attack formed as an angle between the leading face of the blade and a tangent to a circle formed by the circumference of the cutter assembly is greater than about 60° and less than 90°.

20. The intralumenal material removal system ofclaim 18, additionally comprising a control unit provided as a separate console incorporating displays for providing information concerning operating conditions and feedback from the material removal site to the operator.

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