U.S. patent application number 12/050833 was filed with the patent office on 2008-09-18 for intralumenal material removal using a cutting device for differential cutting.
This patent application is currently assigned to PATHWAY MEDICAL TECHNOLOGIES, INC.. Invention is credited to Brent NISTAL, Casey TORRANCE, Edward I. WULFMAN, Scott YOUMANS.
Application Number | 20080228208 12/050833 |
Document ID | / |
Family ID | 36703959 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080228208 |
Kind Code |
A1 |
WULFMAN; Edward I. ; et
al. |
September 18, 2008 |
INTRALUMENAL MATERIAL REMOVAL USING A CUTTING DEVICE FOR
DIFFERENTIAL CUTTING
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.
Inventors: |
WULFMAN; Edward I.;
(Woodinville, WA) ; TORRANCE; Casey; (Seattle,
WA) ; NISTAL; Brent; (Seattle, WA) ; YOUMANS;
Scott; (Bothell, WA) |
Correspondence
Address: |
SPECKMAN LAW GROUP PLLC
1201 THIRD AVENUE, SUITE 330
SEATTLE
WA
98101
US
|
Assignee: |
PATHWAY MEDICAL TECHNOLOGIES,
INC.
Kirkland
WA
|
Family ID: |
36703959 |
Appl. No.: |
12/050833 |
Filed: |
March 18, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10442888 |
May 20, 2003 |
7344546 |
|
|
12050833 |
|
|
|
|
60453846 |
Mar 10, 2003 |
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Current U.S.
Class: |
606/159 ;
606/180 |
Current CPC
Class: |
A61B 5/418 20130101;
A61M 25/0147 20130101; A61B 2017/00199 20130101; A61B 2017/2927
20130101; A61B 2017/00017 20130101; A61B 17/320758 20130101; A61M
2039/062 20130101; A61B 2017/320032 20130101; A61B 8/12 20130101;
A61B 5/415 20130101; A61B 17/320725 20130101; A61B 8/4209 20130101;
A61B 17/3462 20130101; A61M 39/0606 20130101; A61B 2017/00973
20130101; A61B 2017/22049 20130101; A61B 5/061 20130101; A61M
1/0084 20130101; A61M 39/06 20130101; A61B 17/32002 20130101; A61B
2217/005 20130101 |
Class at
Publication: |
606/159 ;
606/180 |
International
Class: |
A61B 17/3207 20060101
A61B017/3207; A61B 17/22 20060101 A61B017/22 |
Claims
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.degree. and less than 90.degree.; 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 of claim 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.degree. and 75.degree..
3. The system of claim 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.degree. and less than 90.degree..
4. The system of claim 1, wherein the cutting blades are raised
cutting flutes provided on a fixed diameter cutter assembly.
5. The system of claim 1, wherein the cutting blades are provided
as cutting members of an expandable cutter assembly.
6. The system of claim 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 of claim 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 of claim 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 of claim 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 of claim 1, wherein the differential cutting blades
have an abrasive surface.
11. The system of claim 1, wherein the differential cutting blades
are chamfered at least one of their proximal and distal ends.
12. The system of claim 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 of claim 1, wherein the differential cutting blades
have an asymmetrical curved profile.
14. The system of claim 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.degree. and less than
90.degree.; 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 of claim 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.degree. and less than 90.degree..
17. The intralumenal material removal system of claim 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.degree. and less than
90.degree.; and a liquid infusion system providing infusion of
liquid in proximity to the cutter assembly.
19. The intralumenal material removal system of claim 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.degree. and less than 90.degree..
20. The intralumenal material removal system of claim 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.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] 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. .sctn.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. .sctn.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
[0002] 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
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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
[0023] 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.
[0024] 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.
[0025] FIG. 3 shows an enlarged, exploded perspective view of one
embodiment of an expandable cutter assembly of the present
invention.
[0026] 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.
[0027] 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
[0028] FIG. 5B illustrates an enlarged, front view of one
embodiment of the dual cutter assembly of FIG. 5A with the cutter
assembly in a contracted configuration.
[0029] FIG. 6A illustrates an enlarged, perspective view of one
embodiment of the dual cutter assembly of FIG. 6A with the cutter
assembly in an expanded configuration, and FIG. 6B illustrates an
enlarged, front view of one embodiment of the dual cutter assembly
of FIG. 6A with the cutter assembly in the expanded
configuration.
[0030] FIGS. 7A-7C illustrate blade angles, wherein FIG. 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 of
FIG. 7A, according to one embodiment of the present invention, and
FIG. 7C illustrates a prior art cutting device.
[0031] FIGS. 8A and 8B are schematic diagrams illustrating blade
angles, wherein FIG. 8A illustrates a blade angle of attack
according to one embodiment of the present invention, and
[0032] FIG. 8B illustrates one prior art cutting device.
[0033] 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.
[0034] FIG. 10 depicts the embodiment of FIG. 9 in a exploded
perspective.
[0035] FIG. 11 provides a cross-sectional perspective of an
alternative embodiment of the present invention.
[0036] FIG. 12 shows an embodiment of a expandable cutter
highlighting the central block and cutting members assembly.
[0037] FIG. 13A illustrates a side view of another embodiment of a
fixed diameter distal cutter, and FIG. 13B provides a front
perspective of the fixed diameter distal cutter illustrated in FIG.
13A.
[0038] 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.
[0039] FIGS. 15A-15B are schematic diagrams illustrating exemplary
curved blades of a cutter assembly, wherein FIG. 15A shows a
cup-shaped cutter assembly with symmetrically curved and gradually
sloping blades, and FIG. 15B shows a single blade having an
asymmetrically curved profile.
[0040] FIGS. 16A-16D are schematic cross-sectional diagrams
illustrating different numbers of blades according to various
embodiments of the present invention, wherein FIG. 16A shows seven
blades, FIG. 16B shows six blades, FIG. 16C shows five blades, and
FIG. 16D shows three blades.
[0041] FIGS. 17A and 17B are schematic diagrams illustrating ports,
wherein FIG. 17A shows an internal cut-away view of a cutter
assembly with ports, according to one embodiment of the present
invention, and FIG. 17B shows a cutter assembly with an exploded
view of a port.
[0042] 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, and FIG. 18C is an angled side view of the cutter
assembly.
[0043] FIG. 19A shows an alternative embodiment of an expandable
cutter assembly in the contracted configuration, and FIG. 19B
provides a front perspective of the alternative embodiment of the
present invention illustrated in FIG. 19A.
[0044] FIG. 20A shows an alternative embodiment of an expandable
cutter assembly in the expanded configuration and FIG. 20B provides
a front perspective of the alternative embodiment of the present
invention illustrated in FIG. 20A.
[0045] FIG. 21 shows a drive shaft of the present invention having
right-lay and left-lay helical configuration.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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.RTM.
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.
[0065] 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 in FIG. 21, multi-helical drive
shaft 410 has adjoining sections of "left-lay" and "right-lay"
helical configurations 412 and 414, respectively, and each section
may be of substantially equivalent length. The "left-lay" and
"right-lay" sections 412 and 414 may be arranged along the
longitudinal axis of multi-helical drive shaft 410 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.
[0066] 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 coils 412 and 414 may be
joined together directly, or, as shown in FIG. 21, by means of a
fixed connection to a conventional coupler 416 interposed between
the coils. Such fixed connections may be provided, for example, by
welding, soldering, brazing, adhesives and the like.
[0067] 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.
[0068] An enlarged depiction of one example of a cutter assembly is
shown in FIG. 1 having a cutter assembly housing 46 provided at
distal end of guiding catheter 40 or primary sheath. In one
embodiment, the cutter assembly housing 46 may be provided as a
continuous, enlarged section of guiding catheter 40 or a primary
sheath that accommodates cutter assembly 42. For example, the
hollow interior of cutter housing 46 defines an interior space 47
in which the cutter assembly 42 resides when axially retracted in a
proximal direction. Interior space 47 of expandable cutter housing
46 may be continuous with the lumen of a primary sheath or the
lumen of guiding catheter 40, 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.
[0069] 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.
[0070] As illustrated in FIGS. 2 and 3, a distal end of drive shaft
25 may be fixedly connected to the cutter assembly, such as an
expandable cutter assembly 42. One embodiment of expandable cutter
assembly 42 may be a dual cutter assembly comprising a proximal
bushing 150, an adjustable cutter housing a central block 152 and a
plurality of cutting members 154, a fixed diameter distal burr 156
and an assembly tube 158.
[0071] 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 as series 300 and/or 400, 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.
[0072] In the specific embodiment illustrated in FIG. 2, a hollow
flexible conduit catheter 94 is coaxially disposed within the lumen
of a primary sheath. Conduit catheter 94 may be constructed from
plastic such as polyvinyl chloride (PVC), TEFLON.RTM. brand
polytetrafluoroethylene, Nylon or another polymer, or from a
helical metal spring wire encased in a suitable polymer to provide
a sealed conduit. Conduit catheter 94 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 catheter 94 is a coiled metallic catheter 106 having a
tightly associated flexible outer sheath 108, such as a TEFLON.RTM.
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 catheter 94 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 between conduit catheter 94 and
drive shaft 25 usually serves as a conduit for fluids and
particulates during aspiration and perfusion.
[0073] A distal end 100 of conduit catheter 94 is fixedly connected
to a proximal section 102 of a first slip seal/bearing assembly
104. Slip seal/bearing assembly 104 is a mechanism for coupling
conduit catheter 94 to expandable cutter assembly 42, while
permitting free rotation of cutter assembly 42 around a central
axis and forming a fluid-tight junction between conduit catheter 94
and cutter assembly 42. Outer sheath 108 of conduit catheter 94
extends to partially cover the outer wall of the proximal section
of slip seal/bearing assembly 104. A distal section 110 of first
slip seal/bearing assembly 104 is in close association with the
collar section 112 of proximal bushing 150, thereby forming the
slip seal/bearing junction 104. Collar section 112 of proximal
bushing 150 is continuous with body section 118 of proximal bushing
150. Proximal bushing 150 has an axially-aligned central aperture
114, which enlarges at collar section 112 to form a proximal
bushing conduit 116. The axially-aligned central aperture 114
receives assembly tube 158. Proximal bushing 150 also possesses a
first series of receiving apertures 120 radially arranged around
central aperture 114 for receiving proximal end 122 of rod section
124 of cutting members 154. 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.
[0074] As shown in FIGS. 3 and 4, an expandable type of cutting
assembly has cutting members 154, i.e. blades, which may comprise a
rod section 124, having a proximal end 122 and a distal end 126.
Along the middle portion of each rod section, a blade 128 having a
beveled edge 130 for cutting may be mounted. It is understood that
the beveled edge 130 of the blade(s) may be of different
configuration to facilitate the removal of occlusive material. Rod
sections 124 of cutting members 154 may be seated onto central
block 152.
[0075] Central block 152 may support a plurality of cutting members
154 and may provide a central lumen 136 for receiving assembly tube
158. Central block 152, having a proximal 132 and a distal 134 end,
may also serve as a control mechanism for the axial rotation of
cutting members 154, which is explained in detail below. Central
block 152 often incorporates a plurality of raised spines 138
tangentially arranged around its central axis. Raised spines 138
may have a support face 140 and a stop face 142. The junction
between raised spines 138 forms a seat for receiving rod sections
124 of cutting members 154. A proximal end 132 of central block 152
may be permanently fixed to a distal face 144 of proximal bushing
150 using any conventional means, including but not limited to,
welds of all types, mechanical attachments and adhesives.
[0076] In some embodiments of the present invention, and as
depicted in the accompanying drawings, six cutting members 154 are
mounted on a central block configured to support six cutting
members. Cutting members 154 are seated in the junctions of raised
spines 138 of central block 152, with the blade section 128 of each
respective cutting member 154 contacting the support face 140 of
the corresponding raised spine 138 of central block 152. The distal
end 126 of each rod section 124 of cutting members 154 extends
distally beyond the distal end 134 of central block 152 to engage
the proximal face 160 of a distal cutter 156 having a fixed
diameter.
[0077] As shown in FIGS. 1, 2, 3, 5 and 6, the fixed diameter
distal cutter 156 typically may have a frusto-conical
cross-sectional configuration and a series of raised cutting flutes
148, i.e. blades. The fixed cutter 156 may be provided distally to
an adjustable cutter or without another cutter in the cutter
assembly.
[0078] The raised cutting flutes 148 of fixed cutter 156 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.
[0079] 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.degree.. 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".
[0080] One example of the use of an acute angle of attack for a
cutter assembly, according to the present invention, is depicted in
FIG. 7B. FIG. 7A depicts a side view of one embodiment of cutter
assembly 600. FIG. 7B is a cross-sectional view through line (B to
B') of the head of cutter assembly 600 viewed from the proximal to
distal ends of the blades. Each of the blades 602 is positioned to
form an acute blade angle (.alpha.). The blade angle (.alpha.) is
defined by the angle of intersection of the surface of a blade's
leading face 606 and tangent line 634, which is tangent to a circle
636 formed by the outermost tips 638 of the blades 602. 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'. The tangent line 634 is in a
plane to the circumference 636 of the cutter assembly defined by
the outer edge of all of the blades at the blade's outermost tip
638.
[0081] In the cutter assembly and blade embodiment illustrated in
FIG. 7B, both faces of each blade 602 may serve as leading faces,
depending on the direction of rotation of the cutter assembly. Both
faces of blades 602 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 of
blades 602 may form cutting surfaces, depending on the direction of
rotation of the cutter assembly.
[0082] 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.degree.. Preferred blade angles for differential
cutting purposes are typically acute, for example, less than or
equal to 90.degree.. Acute blade angles are preferably greater than
10.degree. and less than 90.degree., and also may be greater than
about 30.degree. or 45.degree. or 60.degree. and less than
90.degree.. In still other embodiments, the blade angle may be
between about 45.degree. to less than or equal to about 75.degree.,
and in another embodiment is less than 70.degree..
[0083] An example of a prior art cutting device that has an obtuse
blade angle is shown in FIG. 7C, wherein cutting movement is in a
direction A to A'. The blade 602 has a leading edge 630, a trailing
edge 631 and a flat outer face 633. The blade attacks the tissue at
a tangent 632 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 .beta. is formed
between the outer face 633 and tangent 632, the blade angle of
attack .alpha., as defined herein, between the leading edge 630 and
tangent 632 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.
[0084] 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.degree., 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.
[0085] 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.
[0086] 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.
[0087] 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 in FIG. 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
a blade contact point 635. The leading surface 630 of the blade 602
takes an acute or narrow approach to the surface 632 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.
[0088] 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.
[0089] An example of one prior art cutting device is depicted in
FIG. 8B, wherein the cutting movement is in a direction A to A'.
The blade 602 has a leading face 630 that is positioned with a wide
approach to the surface 632, i.e. greater than 90 degrees, to the
surface 632. 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.
[0090] 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 cutting members 154, 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 cutting flutes 148 are chamfered to
render them atraumatic.
[0091] 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.
[0092] As shown in FIG. 3, fixed cutter 156 may be provided with a
central aperture 146, which defines a surface for mounting assembly
tube 158 and receiving the guidewire. A second series of receiving
apertures may be present in proximal face 160 of fixed cutter 156.
The receiving apertures may be radially arranged around the central
lumen, and complementary to the first series of receiving apertures
120 located on distal face 144 of proximal bushing 150. The
receiving apertures receive distal end(s) 126 of rod sections 124
of cutting members 154. 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 the
distal end 134 of central block 152 and proximal face 160 of fixed
cutter 156.
[0093] Assembly tube 158 may serve as a connecting means for the
cutter assembly 42, as well as a bore for receiving a guidewire and
a conduit for fluids and debris during aspiration and/or infusion.
Assembly tube 158 may comprise a body section 166, a proximal end
168 and a distal flanged cap section 170 having a central aperture
172 defining guidance passage 174. A proximal end 168 of assembly
tube 158 may traverse central aperture 146 of fixed cutter 156, and
central lumen 136 of central block 152, and central aperture 144 of
proximal bushing 150 to fixedly connect with the distal end of
drive shaft 25. Distal cutter 156, central block 152 and proximal
bushing 150 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 distal flanged cap section 170 of
assembly tube 158.
[0094] 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 in
FIGS. 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 in cutter assembly 42 and lumen 186
formed between flexible conduit catheter 94 and drive shaft 25,
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 unit 18 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.
[0095] A secondary aspiration and perfusion system is provided
using a plurality of ports in cutter assembly 42 to draw fluids and
particulate debris through lumen 174 of assembly tube 158,
providing a conduit which is continuous with lumen 186 of flexible
conduit catheter 94 and a lumen of a primary sheath. As illustrated
in FIGS. 2-6, cutter assembly 42 may be provided with a plurality
of ports in assembly tube 158, fixed diameter distal cutter 156 and
central block 152. Ports 194, 194', etc., in distal cutter 156
communicate with assembly tube ports 196, 196', etc. In some
embodiments, distal cutter ports 194, 194', etc. are interspaced
circumferentially around the distal cutter 156. Central block 152
may have a first plurality of circumferentially interspaced ports
204, 204', etc., in the distal portion, and a second plurality of
circumferentially interspaced block ports 206, 206' etc., in the
proximal portion, which may be arranged in a staggered
configuration. The first plurality of ports 204, 204', etc. may
define a lumen that is in alignment and continuous with the second
group of assembly tube ports 198, 198' etc., and the second
plurality of ports 206, 206' etc. may define a lumen that is in
alignment and continuous with the third group of assembly tube
ports 200, 200' etc., such that under vacuum conditions, fluid and
particulates flow through cutter ports 194, 194' etc., central
block ports 204, 204' and 206, 206' etc. as shown by arrow 208 and
210, respectively. Fluid and particulates may continue to flow
through assembly tube lumen 174 to a third group of assembly tube
ports 202, 202' etc., to lumen 186 of conduit catheter 94, as shown
by arrow 212. The infusion of fluids may be provided by switching
to an infusion source and reservoir, and reversing flow so that
fluid flows through cutter assembly 42 in a direction opposite that
of directional arrows 208 and 210.
[0096] 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 the guidewire 11, cutter assembly
42 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 guiding catheter 40 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.
[0097] 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 of cutter assembly 42 may be positioned
at the proximal boundary of the occlusion, whereupon drive system
24 may be actuated and drive shaft 25 and cutter assembly 42 may be
rotated. In the use of one embodiment of a dual cutter assembly
illustrated in the accompanying figures, particularly in FIGS. 5A
and 5B, cutter assembly 42 is often initially rotated in a
counter-clockwise direction and advanced so that distal, fixed
diameter cutter 156 cuts and abrades the occlusion. Initial
rotation of cutter assembly 42, contacting distal cutter 156 with
the occlusive material, is capable of removing occlusive material
having a cross-sectional area roughly equivalent to the largest
outer diameter of distal cutter 156 and diameter central block
152/cutting members 154 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.
[0098] 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 retracting cutter assembly 42 to
facilitate the aspiration of particulates, especially particulates
which are too large to pass through ports 194, 204, 206, etc. in
cutter assembly 42. For example, retracting cutter assembly 42 in a
retrograde direction (i.e. proximally) within cutter housing 46 of
primary sheath 40 during aspiration often creates a laminar-like
flow, thereby more effectively drawing fluid and particulates into
housing 46 and permitting particulates to be further broken down by
the grinding action of the rotating cutter assembly within housing
46. Larger particulates may thus be broken down to a size that can
be withdrawn, with fluids, through aspiration ports 194, 204, 206,
etc.
[0099] 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 cutting members 154 of expandable cutter assembly
to open to an expanded configuration, as illustrated in FIGS. 6A
and 6B. Specifically, as the expandable cutter assembly 42 is
rotated in a clockwise direction, centrifugal forces of rotation
combine with hydrodynamic and frictional forces between the
surrounding fluid within the lumen and blades 128 of cutting
members 154, cause cutting members 154 to rotate around a central
axis, as defined by rod sections 124 of cutting members 154.
Cutting members 154 may rotate freely within the first receiving
apertures 120 and second receiving apertures 164 in proximal
bushing 150 and distal cutter 156, respectively. Cutting members
154 rotate from a tangential orientation, in which blades 128 are
in contact with the respective support faces 140 of raised spines
138 of central block 152 (i.e., the contracted configuration) to a
radial orientation in which blades 128 of cutting members 154 are
in contact with stop faces 142 of raised spines 138 of central
block 152 (i.e., the expanded configuration). Stop faces 142 of
raised spines 138 check the rotational movement of the cutting
members 154, as well as provide support to blades 128 of cutting
members 154 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.
[0100] While in the expanded configuration, the expandable cutter
assembly may be axially translated along guidewire 11 to retrace
the pilot-pass made through the occlusion, whereupon beveled edges
130 of cutting members 154 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.
[0101] After sufficient occlusive material has been removed, the
expandable cutter assembly may be contracted by engaging the drive
system to rotate cutter assembly 42 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 on
blades 128 of cutting members 154, causing the cutting members to
rotate around a central axis, as defined by rod sections 124 of
cutting members 154. Cutting members 154 rotate from a radial
orientation, in which blades 128 of cutting members 154 are in
contact with stop faces 142 of raised spines 138 of central block
152 (i.e., the expanded configuration) to a tangential position in
which blades 128 are in contact with the respective support faces
140 of raised spines 138 of central block 152. Support faces 140 of
raised spines 138 stop the rotational movement of the cutting
members 154, as well as provide support to blades 128 of cutting
members 154 while in the contracted configuration. While in its
contracted state, the cutter assembly 42 may be retracted into the
primary sheath or guiding catheter for removal from the body or
further advanced distally along guidewire 11 to perform additional
operations. FIGS. 6 and 9-11 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.
[0102] FIG. 9 depicts an alternative embodiment of a dual cutter
assembly according to the present invention comprising at least one
flexible conduit catheter 94' in which drive shaft 25, such as a
multi-helical drive shaft, runs coaxially within its internal
lumen. A proximal encasement 340 may fixedly connect flexible
conduit catheter 94' to a secondary segment of flexible conduit
catheter 342, which in turn may fixedly connected to a distal
encasement 344. Distal encasement 344 may form a slip-bearing
fitting with a proximal cap 346, thereby permitting free rotation
of drive shaft 25 and cutter assembly 42' within coiled metallic
catheter. As with previous embodiments, cutter assembly 42' may
comprise a central block 152', a fixed diameter distal cutter 156'
and a plurality of cutting members 154'.
[0103] As illustrated in FIGS. 10 and 11, drive shaft 25 may be
provided with retainer assembly or mechanism 338 for
interconnecting drive shaft 25 and flexible conduit catheter 94'.
Any conventional assemblies or mechanisms may be utilized, such as
a retainer 348 having a first end 350 fixedly connected to flexible
conduit catheter 94' and a second end 352 fixedly connected to a
first end 360 of secondary segment of flexible conduit catheter
342, by any conventional methods, such as by welding,
laser-welding, soldering, brazing, adhesive bonds and the like.
Retainer 348 may operate in conjunction with one or more thrust
bearings to facilitate cooperative axial translation of drive shaft
25 and flexible conduit catheter 94' in either an antegrade or
retrograde direction. A first thrust bearing 356 may fixedly
connected to drive shaft 25 proximal to center section of retainer
354, and a second thrust bearing 358 may fixedly connected to drive
shaft 25 distal to center section of retainer 354 in such a manner
as to bring first 356 and second 358 thrust bearings in close or
tight association with center section 354 of retainer 348. Drive
shaft 25 may freely rotate within central aperture of retainer 348.
Retainer assembly may be enveloped by some tubular sheath, such as
proximal encasement 340 to add additional strength and provide a
relatively smooth profile to flexible conduit catheter 94'.
[0104] Notably, retainer assembly 338 and proximal encasement 340
may be located an operable distance from cutter assembly 42'.
"Operable distance," as used herein, is defined as a distance which
permits secondary segment of flexible conduit catheter 342 and
associated cutter assembly 42' to retain sufficient flexibility to
effectively maneuver within intralumenal spaces, particularly along
curved, arched and/or branched sections of lumenal bodies. The
distance between retainer assembly 338/proximal encasement 340 and
distal cutter assembly 42' may be less than 1 cm to over 20 cm.
[0105] Cutter assembly 42' may be fixedly connected to drive shaft
25 while permitting free rotation within flexible conduit catheter
94'. Drive shaft 25 may be fixedly connected to a proximal cap 346,
which has a distal flange section 366 fixedly connected central
block 152'. This arrangement transfers rotational movement from
drive shaft 25 to cutter assembly 42'. Proximal cap 346 may be
provided with a central aperture for receiving guide wire 11, and a
number of cut-away sections to create one or more accesses
continuous with the lumenal space within all sections of flexible
conduit catheter 342, 94'. This lumenal space serves as a conduit
for aspiration and infusion materials and is continuous with the
various ports of cutter assembly 42'. A slip seal/bearing assembly
368 may be created at the connection between distal encasement and
flange section of proximal cap 366 thereby permitting free rotation
of drive shaft 25, proximal cap 346 and cutter assembly 42' within
flexible conduit catheter 94', 342 without imparting rotational
movement to flexible conduit catheter 94', 342, which minimizes
unnecessary trauma to the surrounding tissues.
[0106] The embodiments depicted in FIGS. 9-11 have a number of
uniquely distinguishing features. As shown in FIGS. 10, 11 and 12,
central block 152' may be fitted with any suitable number of
cutting members 154', 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 shows
central block 152' having a plurality of receiving slots 380 for
receiving rod sections 124' of cutting members 154'. Cutting
members 154' may be formed from interconnected rod and blade
members, or often machined from one integral piece. As with the
previous embodiment, cutting members 154' are provided with beveled
edges 130', such that the principles of differential cutting apply.
It is understood that any suitable differential cutting angle may
be utilized for beveled edge 130' in addition to those depicted in
the figures. A central aperture 136' may be provided running along
the longitudinal axis of central block 152' to permit free axial
translation of guide wire 11 and/or other components, as well as
serve as a conduit for aspiration and infusion. A plurality of
ports 382 may be provided in central block 152' which are
continuous with central aperture 136' and lumen of flexible conduit
catheter 342, 94', further providing aspiration capabilities to
cutter assembly 42'. This particular embodiment provides a greater
number of ports 382 in central block 152', thereby increasing
aspiration and infusion efficiency. Distal face 134' of central
block 152' may be fixedly connected to proximal face 160' of fixed
diameter distal cutter 156' by any conventional methods, such as by
welding, e.g. laser welding, soldering, brazing, adhesive bonds and
the like.
[0107] 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.
[0108] As more clearly illustrated in FIGS. 13A and 13B, cutter
156' 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 or
blades 148' radiating from central aperture 146' to body 388 of
cutter assembly 156'. 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 or blades 148' may be chamfered to
render them atraumatic.
[0109] As shown in FIGS. 13A and 13B, cutter assembly 156' 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 cutting
flutes 148' may be cut away to provide an aspiration cutout 390,
which form an internal cavity that is continuous with central
aperture 136' 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 cutting flutes 148',
and aspiration cutouts 390 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 assembly 156' may have any sort of cutting and/or
grinding elements 394 associated with body 388 of cutter assembly
156' to further facilitate removal of occlusive material.
[0110] Another example of one such a cutter assembly that is
designed for differential cutting is depicted in FIG. 14. Cutter
assembly 600 comprises a plurality of blades 602 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. Ports 614 are
defined, at least in part, by the gaps between the blades 602. 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 a blade facing surface 604 on
each blade presented at least substantially in front of and spaced
apart from an adjacent and opposing blade's facing surface, such as
leading face 606.
[0111] The cutter assembly may further have a distal tip 616 on its
distal end and on its opposite end, a proximal end 620. In some
embodiments of cutter assembly 600, the distal tip 616 may have a
central bore 618 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.
[0112] Typically, the blade 602 is also provided with an outer
surface 608 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 an inner
surface 610 facing an internal cavity within the cutter
assembly.
[0113] 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
as series 300 and/or 400, 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.
[0114] 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, the proximal
end 620 is larger than the distal tip 616. For example, the
proximal end may have a diameter that is at least twice the
diameter of the distal tip, as shown in FIG. 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.
[0115] Another embodiment of cutter assembly 600 is depicted in
FIG. 7A, wherein rather than pear-shaped, the cutter assembly is
bullet-shaped and gradually widens from a narrow distal tip 616 to
its proximal end 620. FIG. 15A shows a cup-shaped cutter assembly
with multiple gradual sloping blades 602 from the distal tip 616 to
the proximal end 620. Depicted in FIG. 15B is a single blade 602
having a gradual sloping blade profile, where the blade profile
gradually slopes from one end, such as the blade's distal tip 622,
to the other end, such as the blade's proximal end 624. 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.
[0116] 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.
[0117] 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.
[0118] There may be any number of blades 602 provided in a cutter
assembly 600, as shown variously in the examples in FIGS. 16A to
16D. FIG. 16A depicts a seven blade head, whereas FIG. 16B depicts
a six blade head, FIG. 16C shows a five blade head and FIG. 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.
[0119] As illustrated in the exemplary embodiments, the size and
shape of the ports 614 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 mm.sup.2, 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.
[0120] An internal view of a cutter assembly 600 is represented in
FIG. 17A, wherein ports 614 may be provided as relatively large
openings that may open to internal cavity 640. 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.
[0121] The ports usually provide communication between the removal
site and the conduit of the removal system through the internal
cavity 640. For example, the internal cavity 640 of the cutter
assembly may be in communication with and terminate at the conduit,
or other connecting component of the removal apparatus, to provide
a collar 642 at the proximal cutter assembly end 620. 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
a distal tip 616 that may provide for translation of the cutter
assembly over a guide wire. In some embodiments, the central bore
618 may extend from the distal tip 616 to the internal cavity 640.
In some cutting assemblies, the internal cavity 640 may have a
diameter greater than that of central bore 618.
[0122] FIG. 17B depicts the shape of a port 614 exploded from
cutter assembly 600 as created by the space, i.e. gaps, between
adjacent blades 602. The profile of the port may be defined by the
contour of the opposing blade's facing surface 606 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 the proximal
face 646 of a proximal ring 644 that contacts the proximal end of
the blades.
[0123] The proximal ring 644 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. A distal ring 648 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.
[0124] The proximal ring 644 may also include an outer ablation
surface having a plurality of micro-flutes 650 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.
[0125] In one embodiment, as depicted, for example, in FIGS. 18A to
18C, the tips 652 of the blades 602 are extended farther than the
outer diameter of the proximal ring 644 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.
[0126] 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 to FIGS. 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.
[0127] Similar to embodiments previously described, FIGS. 19A to
19B illustrate cutter assembly 42' in a contracted and expanded
configuration, respectively. Cutting members 154' may freely rotate
within recesses 380 of central block 154' and, depending on the
direction of rotation, rotate from a tangential orientation, in
which blade sections of cutting members engage respective support
faces 140' (i.e., contracted configuration) to a radial orientation
in which blade sections of cutting members 154' are in contact with
stop faces 142' of central block 152' (i.e., expanded
configuration). Stop faces 142' check rotational movement of blade
members and provide support while operating in the expanded
configuration.
[0128] The same general principles of operation described above
apply to the embodiment depicted in FIGS. 20A-20B. Notably, one
embodiment provides a fixed diameter distal cutter 156' having
cutting flutes 148' that immediately engage occlusive material.
Additionally, the embodiment may provide a comparatively large
aspiration conduit area by virtue of the large aspiration cutouts
or ports 390. During aspiration, aspirate and particulates are may
be drawn through aspiration cutouts, or ports 390 of distal cutter
156', ports 382 of central block 152', as well as spaces between
central block 152' and proximal cap 366, as depicted by arrows 400,
402 and 404, respectively.
[0129] 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.
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