U.S. patent application number 12/084596 was filed with the patent office on 2009-12-10 for device for the removal of thrombi.
Invention is credited to Fabian Dieste, Ralf Hannes, Elina Miloslavski, Hermann Monstadt, Holgar Pracht.
Application Number | 20090306702 12/084596 |
Document ID | / |
Family ID | 35500794 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090306702 |
Kind Code |
A1 |
Miloslavski; Elina ; et
al. |
December 10, 2009 |
Device for the Removal of Thrombi
Abstract
The invention relates to a device provided with one or several
distal elements (27), with the distal element (27) comprising at
least two core wires (14) which are twisted around each other and
between which fibers (6) are arranged transversely to the extension
of the core wires (14), with said fibers (6) being twisted together
with the core wires (14) so that the fibers (6) project radially
outward from the distal element (27).
Inventors: |
Miloslavski; Elina; (Bochum,
DE) ; Hannes; Ralf; (Dortmund, DE) ; Pracht;
Holgar; (Bochum, DE) ; Dieste; Fabian;
(Bochum, DE) ; Monstadt; Hermann; (Bochum,
DE) |
Correspondence
Address: |
BERLINER & ASSOCIATES
555 WEST FIFTH STREET, 31ST FLOOR
LOS ANGELES
CA
90013
US
|
Family ID: |
35500794 |
Appl. No.: |
12/084596 |
Filed: |
November 9, 2006 |
PCT Filed: |
November 9, 2006 |
PCT NO: |
PCT/EP2006/010751 |
371 Date: |
January 13, 2009 |
Current U.S.
Class: |
606/200 ;
604/264 |
Current CPC
Class: |
A61B 2017/22079
20130101; A61B 2090/397 20160201; A61B 2010/0216 20130101; A61B
2017/2212 20130101; A61B 17/221 20130101; A61B 2017/22042 20130101;
A61B 2017/22034 20130101; A61B 2017/22038 20130101; A61B 2017/22001
20130101 |
Class at
Publication: |
606/200 ;
604/264 |
International
Class: |
A61M 29/00 20060101
A61M029/00; A61M 25/00 20060101 A61M025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2005 |
DE |
10 2005 053 434.1 |
Claims
1. Device for the removal of foreign objects and thrombi from body
cavities and blood vessels comprising a guide wire (18) provided
with one or several distal elements (27), characterized in that the
distal element (27) consists of at least two core wires (14) which
are twisted around each other and between which fibers (6) are
arranged transversely to the extension of the core wires (14), with
said fibers (6) being twisted together with the core wires (14) so
that the fibers (6) project radially outward from the distal
element (27).
2. Device according to claim 1, characterized in that the core
wires (14) are connected with each other at the distal end in such
a way that they form a loop (16).
3. Device according to claims 1 or 2, characterized in that the
core wires (14) are connected at their proximal end via a coil (17)
with other, proximally arranged components of the device.
4. Device according any one of claims 1 to 3, characterized in that
the core wires (14) are made of platinum or a platinum alloy,
platinum-iridium, a nickel-titanium alloy, tungsten, a tungsten
alloy, stainless steel or a combination thereof.
5. Device according to any one of the claims 1 to 4, characterized
in that the twisted core wires (14) extend in a straight line.
6. Device according to any one of the claims 1 to 4, characterized
in that the twisted core wires (14) form a secondary structure.
7. Device according to claim 6, characterized in that an elongation
preventing filament extends through the inner space of the
secondary structure or external to the secondary structure.
8. Device according to claim 7, characterized in that the
elongation preventing filament is designed in the form of a
straight, wave-like or helical wire.
9. Device according to claim 7, characterized in that the
elongation preventing filament consists of a polymer material.
10. Device according to any one of the claims 6 to 9, characterized
in that the twisted core wires (14) have a wave-like
configuration.
11. Device according to any one of the claims 6 to 9, characterized
in that the twisted core wires (14) are designed in the form of a
helix.
12. Device according to claim 11, characterized in that the
diameter of the helix increases from distal to proximal or from
proximal to distal.
13. Device according to any one of the claims 1 to 12,
characterized by several distal elements (27) from which fibers (6)
protrude radially outward.
14. Device according to claim 13, characterized in that the distal
elements (27) are connected with each other by articulated joints
(20).
15. Device according to claim 13, characterized in that the distal
elements (27) are arranged side by side viewed in a cross-sectional
representation.
16. Device according to claim 15, characterized in that the distal
elements (27) are twisted around each other to form a helix.
17. Device according to any one of the claims 1 to 16,
characterized in that the distal elements (27) are provided with
braces (21) starting out from the distal end of the distal element
(27), extend radially outward and again converge centrally at the
proximal end of the distal element (27).
18. Device according to claim 17, characterized in that the braces
(21) span over several distal elements (27).
19. Device according to claim 17 or 18, characterized in that
additional intermediate braces (22) are arranged between braces
(21) and the centrally extending core wires (14) of the distal
element (27).
20. Device according to any one of the claims 1 to 19,
characterized in that the radial extension of the fibers (6) of the
distal element (27) increases from proximal to distal.
21. Device according to any one of the claims 1 to 20,
characterized in that the fibers (6) in the proximal area of the
distal element (27) are harder than in the distal area of the
distal element (27).
22. Device according to any one of the claims 1 to 20,
characterized in that the fibers (6) in the middle area of the
distal element (27) are softer than in the proximal and distal area
of the distal element (27).
23. Device according to any one of the claims 1 to 22,
characterized in that the density of the fiber coverage in the
middle area of the distal element (27) is lower than in the
proximal and distal area of the distal element (27).
24. Device according to any one of the claims 1 to 23,
characterized in that the fibers (6) are secured or attached to the
core wires (14) by clamping, bonding, knotting and/or fusing.
25. Device according to any one of the claims 1 to 24,
characterized in that the ends of the fibers (6) located radially
outward are provided with slubs or nubs.
26. Device according to any one of the claims 1 to 25,
characterized in that the ends of the fibers (6) located radially
outward are at least in part connected with each other by means of
loops.
27. Device according to any one of the claims 1 to 26,
characterized in that the fibers (6), at least partially, protrude
differently far radially outward at both sides of the distal
element (27).
28. Device according to any one of the claims 1 to 27,
characterized in that the core wires (14) in the cross sectional
area of the distal element (27) are arranged and extend
eccentrically.
29. Device according to any one of the claims 1 to 28,
characterized in that the brush structure formed by one or several
distal elements is suitable to be flatly collapsible under the
external strain exerted by a micro-catheter and transported inside
the micro-catheter and unfolds to its full brush structure when
said external strain caused by the micro-catheter is omitted.
30. Device according to any one of the claims 1 to 29,
characterized in that the distal elements (27) are designed so as
to be detachable from the guide wire (18).
31. Device according to any one of the claims 1 to 30,
characterized in that the device additionally is provided with an
elongated cage structure which is suitable to be flatly collapsible
under the external strain exerted by a micro-catheter and
transported inside the micro-catheter and unfolds to its full cage
structure when said external strain caused by the micro-catheter is
omitted.
32. Device according to any one of the claims 1 to 31,
characterized in that the fibers (6) form an angle with
longitudinal axis of the device that ranges between 70.degree. and
110.degree., preferably between 80.degree. and 90.degree..
33. Device according to any one of the claims 1 to 32,
characterized in that the fibers (6) have been provided with a
coating.
34. Device according to any one of the claims 1 to 31,
characterized by one or several radiopaque markers (9).
35. Device according to any one of the claims 1 to 34 in
combination with a guide catheter and/or micro-catheter.
36. Device according to claim 35, characterized in that the guide
or micro-catheter is designed as aspiration catheter.
37. Method for the manufacture of a distal element (27) forming
part of a device according to claim 1, characterized in that at
least two core wires (14) are arranged parallel to each other,
between which fibers (6) are arranged transversely to the extension
of the core wires (14), with said core wires (14) being twisted
around each other.
38. Device for the removal of foreign objects and thrombi from body
cavities and blood vessels comprising a guide wire (18) provided
with one or several distal elements (27), with the distal element
(27) being provided with fibers (6) projecting radially outward,
characterized in that the distal element (27) has a tapered
shape.
39. Device according to claim 38, characterized in that the
diameter of the distal element (27) increases from proximal to
distal.
40. Device according to claim 38, characterized in that the
diameter of the distal element (27) increases from distal to
proximal.
Description
[0001] The invention relates to a device for the removal of foreign
bodies and thrombi from body cavities and blood vessels using a
guide wire provided with one or several distal elements.
[0002] Thromboembolic diseases such as cardiac infarction,
pulmonary embolism, peripheral thrombosis, organ embolisms etc. are
typically caused by a thromboembolism (hereinafter for short thromb
or thrombus), i.e. a visco-elastic blood clot comprising platelets,
fibrinogen, coagulation factors etc. forming in a blood vessel
which it obstructs either wholly or in part. The obstruction of
organ arteries also leads to the supply of oxygen and nutrients to
the associated tissue being interrupted. The disorder of the
functional metabolism linked with functional losses is closely
followed by a failure of the structural metabolism resulting in the
relevant tissue becoming destroyed (infarction). Organs most
frequently affected in this way are the heart and the brain.
Nevertheless, the arteries of the limbs as well as pulmonary
arteries are also impaired. Venous thromboses and thromboembolic
occlusions are frequently occurring in the leg and pelvic veins.
The disease pattern of the thrombotic occlusion of an intracranial
sinus may lead to severe intracerebral hemorrhage due to a failure
of venous drainage of brain tissue.
[0003] In view of the severity of the disease patterns associated
with thromboembolism and the prevalence rate of such diseases
various techniques have been developed aimed at dissolving or
removing thrombi.
[0004] It is known in this context to treat such patients with
thrombolytic agents such as streptokinase or urokinase or
anticoagulants intended to achieve thrombolysis or limit the growth
of thrombi. Since treatment methods of this kind are usually very
time consuming they are frequently combined with invasions aimed at
reducing the size of or removing the thrombus or embolus
mechanically.
[0005] Aside from open surgical operations prior art techniques
more and more embrace the use of transluminal or endovascular,
catheter-guided interventional therapy methods because these are of
less invasive nature. It is thus known to remove the thrombus from
the patient's body by means of vacuum producing suction catheters
or mechanically using catheters provided with capturing cages,
helixes, hooks or similar elements; refer to U.S. Pat. No.
6,245,089 B1, U.S. Pat. No. 5,171,233 A1, Thomas E. Mayer et al.,
Stroke 2002 (9), 2232.
[0006] Disadvantages associated with the known transluminal devices
are that with said devices it is often impossible to remove the
thromb completely and, moreover, there is a risk of the thromb or
fragments of it being released into the blood stream thus passing
on to vessels of smaller lumen which are more difficult to be
reached and treated. Furthermore, due to their size and/or low
flexibility the devices known from prior art are only inadequately
suited for the removal of thrombi from greatly convoluted vessels
or those of particularly small lumen such as those in the
brain.
[0007] From US 2002/0049452 a device with a catheter is known for
the removal of thrombi to which distal end capture arms made of
shape-memory material are attached which in their compressed state
rest against the catheter and when expanded extend radially from
the catheter outwards. When in expanded position which is caused by
the body temperature the capture arms are intended to get caught in
the thrombus and then retract it out of the blood vessel as the
catheter is pulled back into another catheter. The drawback
associated with this device is, however, that in order to cool and
thus keep the capture arms below trans-formation temperature before
they are released into the blood stream it must either be moved
past the thrombus in a secondary catheter which brings about the
cooling effect, or a heating system has to be arranged inside the
catheter provided with the capture arms that enables the
transformation temperature to be attained when the thrombus has
been reached. Not only are the design requirements of this
configuration very high and thus prone to disturbances it is also
the sheer physical size of this device that rules out a treatment
of vessels having a particularly small lumen.
[0008] In view of the disadvantages of these prior art devices it
is thus the object of the invention to provide a device for the
removal of foreign bodies and thrombi from body cavities and blood
vessels which alleviates the surgical risk existing when removing
thrombi and allows the treatment of vessels of especially small
lumen.
[0009] According to the invention this objective is reached by
providing a device for the removal of foreign bodies and thrombi
from body cavities and blood vessels using a guide wire and one or
several distal elements that comprise at least two core wires which
are twisted around each other and between which fibers are arranged
transversely to the extension of the core wires, with said fibers
being twisted together with the core wires, so that the fibers
project radially outward from the distal element.
[0010] The distal element thus has the form of a brush provided
with bristle-like outwardly projecting fibers. The fibers serve the
purpose of capturing and stabilizing a thrombus in that they hook
themselves into the thrombus and in this manner facilitate its
retrieval. At the same time the fibers/bristles are designed so as
to be flexible so that due to the mechanical resistance in proximal
direction they press against the distal element when the device is
moved forward. When the external strain caused by the
micro-catheter is omitted the brush unfolds to assume its full
brush structure. Accordingly, to fulfill their intended purpose of
securing the thrombus the fibers must have adequate stiffness but
at the same time must be sufficiently flexible and bendable so that
they can be passed through a catheter and do not damage the vessel
walls.
[0011] The fibers or bristles are suited to capture and stabilize a
thrombus, especially if they are made of or finished with
thrombogeneous materials.
[0012] The fibers/bristles may also consist of a natural substance,
polymer material, metal, ceramic material, glass or combinations
thereof. Especially preferred are polymer materials.
[0013] Suitable materials in this respect are primarily
polyurethane, polyacrylics, polyester, polytetrafluoroethylene,
polyamide or polyethylene and, due to its peptide-like bond
structure, most notably polyurethane and polyamide, e.g. nylon,
which enable the thrombus to excellently attach/adhere to the
fibers.
[0014] Aside from polymer materials metals also well suited for the
intended purpose. Suitable metallic materials for treatment
purposes are all metals that do not have detrimental effects on the
patients. Especially suited for the described purpose are stainless
steel fibers made of metal alloys having shape-memory properties
such as for example nitinol fibers. Fibers made of shape-memory
materials offer the advantage that when under the external strain
exerted by a micro-catheter they are initially shaped to fit
closely and after having been released from the micro-catheter
assume a second orthogonal shape allowing them to stick out freely.
Furthermore, gold and platinum are suitable materials as well. Also
suited are ceramic materials, fiber glass and carbon fibers.
[0015] Particularly suitable for the treatment of vessels of
especially small lumen are fibers having a length of 0.5 to 6 mm
and preferably 0.5 to 3 mm so that an outer diameter of 1 to
maximum 12 mm of the fiber-carrying part of the distal element is
attained even when the fibers are arranged radially. For a
particularly atraumatic treatment such outer diameter should be
sized slightly smaller than the inner diameter of the relevant
blood vessel.
[0016] Expediently, the fibers extend over a length of the distal
element which ranges between 0.5 and 5 cm. To make sure the
thrombus is sufficiently anchored it is expedient if the fibers are
arranged on the distal element of the guide wire with a density
ranging between 20 and 100 per cm.
[0017] The fibers or bristles to be used according to the invention
preferably project at an angle ranging between 70.degree. and
110.degree., preferably at an angle of between 80.degree. and
90.degree. from the longitudinal axis of the device. These angle
indications are to be understood such that angles<90.degree.
characterize a proximal orientation of the fibers whereas
angles>90.degree. signify a distal orientation of the fibers.
Embodiments providing for an angle which is slightly smaller than
90.degree. are particularly atraumatic when being moved into the
vessel or through the thrombus and at the same time result in an
especially effective anchoring within the thrombus when being
pulled out of the blood vessel.
[0018] Expediently, the guide wire is made of a medical stainless
steel or shape-memory material, preferably nitinol. It is expedient
in this case to provide a guide wire having an outer diameter
ranging between 0.2 and 0.4, preferably 0.22 and 0.27 mm. A typical
guide wire length ranges between 50 and 180 cm, but may as well
amount to several meters.
[0019] As per a particularly preferred embodiment of the device the
fibers are coated. For example, this coating may be a neutral one
consisting of Parylene or polytetrafluoroethylene (Teflon), but may
also be comprised of collagen or may be a coating of a material
conducive to blood coagulation, preferably having one or several
coagulation factors. This embodiment serves to strengthen the
anchorage of the fibers inside the thrombus and alleviates the risk
of the thrombus disintegrating to such an extent that fragments of
it remain in the blood vessel or may be allowed to be released in
the blood stream.
[0020] Surprisingly, it has been found that a thrombogeneous
finishing of the fibers/bristles resulted in a significant
stabilization of the thrombus at the device according to the
invention. In this context it is left to the surgeon to bring the
inventive device into contact with the thrombus and maintain this
contact for a certain period of time thus allowing the
thrombogeneous elements to promote an "adherence" of the thrombus
to the device. Such an adherence to thrombogeneous fibers/bristles
is achieved after a relatively short period, even within a few
minutes at times. Not only does this preclude the disintegration of
the thrombus as it is encountered with many commercially available
devices, also the retraction of the thrombus into the catheter and
its extraction from the vascular system is facilitated in this
manner. Especially suited thrombogeneous materials and coatings for
this purpose are known from literature to those skilled in the art.
Especially suitable to this end are, for example, one or several of
the factors fibrin, thrombin, factor XIII and/or factor VIII.
[0021] The following procedure is to be adopted when using the
invention: The device is transferred to the application site with
the aid of a small-lumen micro-catheter. The device situated inside
the micro-catheter may either be 1) initially maneuvered to the
distal location of the thrombus and then retracted, 2) released
from the micro-catheter in the area of the thrombus, or 3) pushed
out of the micro-catheter at a point proximal to the thrombus and
then penetrate the thrombus anterogradedly. When moving the device
forward the flexible fibers are pressed onto the distal element in
proximal direction due to the mechanical resistance encountered,
and when the device is retracted they assume an upright position,
hook themselves into the thrombus and thus aid the retraction into
a micro-catheter larger than the one originally used. Said larger
catheter is usually a guide catheter by means of which a
micro-catheter can be introduced coaxially which in turn is used to
bring the device to the target area. The thrombus thus secured via
the device will then preferably be retracted into the guide
catheter and contained in this catheter eliminated from the
body.
[0022] In the context of this invention the terms "distal" and
"proximal" are to be understood as viewed from the direction of the
attending physician. The distal end is thus the end situated away
from the attending physician which relates to the components of the
device advanced farther into the blood vessel system whereas
proximal means facing towards the attending physician, i.e. the
proximally arranged components of the device are introduced less
far into the blood vessel system.
[0023] If the phrase `longitudinal direction` is used in this
document it is to be understood as denoting the direction into
which the device is advanced, i.e. the longitudinal axis of the
device also coincides with the longitudinal axis of the blood
vessel along which the device is moved forward.
[0024] The inventive device is manufactured in such a way that the
fibers ultimately forming the brush are placed adjacent to each
other and, if so desired, also superimposed on each other between
two core wires, with said fibers extending orthogonally to the core
wires. It is to be noted in this context that according to the
invention an orthogonal extension shall not exclusively mean an
angle of exactly 90.degree. but rather any transverse configuration
of the fibers in relation to the core wires, i.e. the fibers
primarily extend transversely to the core wires, not in parallel.
Accordingly, also angles of for instance 700 may be viewed as being
orthogonal in the framework of the invention. After the fibers have
been placed between the core wires, said wires are twisted
together, for example in that one end is fixed while the other one
is turned or twisted around the other to bring about a plastic
deformation of the core wires thus forming into a spiral structure.
After the core wires have been twisted together the fibers project
outwardly from the twisted core wires virtually in the form of a
helical line. A significant advantage of such a device is that
relatively little core wire is required to achieve a very high
fiber coverage of the distal element serving as brush. Having to
use only a little amount of core wire also offers benefits in that
the system retains high flexibility. Moreover, fixing the fibers at
the core wires in this embodiment is particularly simple and
results in the fibers to be distributed over the brush in very
uniform manner.
[0025] Quantity as well as density of the fibers can be controlled
via the number of core wire twistings or windings so that different
hardness characteristics can be produced with respect to the radial
force exerted by the brush because the higher the number of
windings the more fibers can be arranged per unit of brush length.
Moreover, the bending stiffness of the core can be adjusted, inter
alia, via the number of core wires and twistings provided. For
example, by providing for a great number of twistings or windings
of two or more core wires a double helix of these two core wires is
formed that is less rigid than with a design wherein fewer windings
are provided.
[0026] If thought expedient, the at least two core wires may be
connected with each other at the distal end and thus form a loop.
In this case only a single core wire is used that first extends up
to the distal end and then leads back in such a manner that it
twists together the two parallelly arranged lines of the core wire
with the fibers arranged in between.
[0027] At the proximal end the core wires may be connected by means
of a coil to additional components of the device located in
proximal direction. Such proximally arranged additional components
may, in particular, consist of a guide wire or another distal
element designed in the form of a brush. A connection with the help
of coils of this nature is sufficiently known in the field of
medical technology, particularly when occlusion helixes are
employed to treat aneurysms. Connecting the coil with the core
wires may be brought about in this case by welding, bonding,
soldering or mechanical (i.e. force- and/or form-closed) joining
methods.
[0028] The core wires may consist of platinum or its alloys, in
particular of a platinum-iridium alloy, stainless steel,
nickel-titanium alloys such as nitinol, or of tungsten and tungsten
alloys as well as of combinations of the materials named here.
[0029] The core wires and thus the entire brush may have a straight
configuration or form into a secondary structure, for example be
shaped in the form of a wave or helix, i.e. the core wires
themselves which are twisted together are designed such that the
core itself has a wave or helix form. It is to be understood in
this context that the difference between a wave and a helix is that
the geometry of a wave is merely two-dimensional whereas a helix
has a three-dimensional configuration. Brushes having a wave or
helix form offer advantages in terms of an improved cleaning
efficiency. In this context the diameter of the helix may increase
either from proximal to distal or from distal to proximal.
[0030] In the case of a secondary structure formed by twisted core
wires an elongation preventing filament may additionally be run
through the inner space of the secondary structure or external to
it, with said filament ruling out an axial extension of the device
beyond the nominal length. Elongation preventing filaments of this
nature may be made of polymer materials (e.g. nylon) or metal, such
as, for example, nickel-titanium alloys (nitinol). The filaments in
this case are connected both distally and proximally to the
secondary structure formed by the core wires. The elongation
preventing filament itself may have a straight, wave-like or
helix-shaped geometry, with the two latter variants allowing for a
certain tolerance or play in longitudinal direction with respect to
a possible axial extension. However, to achieve a still sufficient
protection against elongation such a helix should have a very high
pitch resulting in the tolerance or play with respect to axial
extension to be kept within certain limits.
[0031] The core wires mentioned above must not necessarily be
conventional wires having a round cross section but may be provided
in the form of cut or shaped form elements, for example if the core
wires are cut from a plate. In this case the cross section of the
core wires is not round but quadratic or foursquare.
[0032] In accordance with another advantageous embodiment the
device is provided with several distal elements from which fibers
stick out radially. Such a system consisting of several brushes
may, for example, offer benefits if particularly large thrombi or,
as the case may be, several thrombi have to be eliminated from the
blood vessel system. Furthermore, a brush located farther distally
may serve, if need be, to intercept and remove fragments of a
thrombus that detach from the proximally arranged brush.
[0033] To enable an adequate flexibility to be achieved despite the
length of such a system comprising several brush portions it is
considered expedient to interconnect the individual distal elements
by means of connecting elements, especially articulated joints.
Such an articulated joint makes it possible for the device to
perform within certain limits bending movements and thus follow the
configuration of the blood vessels.
[0034] As the case may be, several distal elements forming a brush,
preferably two or three brushes, may be arranged side by side as
viewed in the cross section of the device, preferably in parallel.
These brushes are in turn interconnected proximally and distally,
for example in that the core wires of the brushes again converge
centrally on the proximal and distal sides. Such an embodiment
offers the advantage that each individual brush may be provided
with shorter fibers because the fibers need not extend from the
center of the device to the inner wall of the vessel but merely
from the individual distal elements that are near the vessel walls
in the event they are arranged side by side. Since fibers that are
shorter or stick less far out of the distal element are in any case
harder the cleaning efficiency may be improved even more in this
way. If thought expedient, the individual brushes may also be
twisted further so as to form a helix. Furthermore, the distal
elements may be provided with braces (expediently at least 3) that
start out from the distal end of the distal element, extend
radially outward and again converge centrally at the proximal end
of the distal element. The radial extension of the braces
preferably corresponds roughly to the radial extension of the
fibers. Throughout the middle area the braces thus extend for the
main part in parallel with the inner core of the distal element.
The provision of braces on the distal element serves as additional
guide for the system in the blood vessel. To a certain extent the
braces impart a resemblance to cage structures, but the braces in
this case need not be arranged such closely so that it cannot be
said in any circumstance that a true cage structure exists.
[0035] In cases where the device is provided with several distal
elements having outwardly projecting fibers the braces may span in
each case over one distal element or over several distal elements.
In the event of two distal elements the braces may, for example,
extend from the distal end of the distal element located farthest
away in distal direction and only converge at the proximal end of
the proximal brush. In this case it is expedient to arrange
additional intermediate braces between the braces and the centrally
extending core wires and in this way enhance the stability of the
structure formed by the braces.
[0036] In accordance with another advantageous embodiment of the
invention the brushes have a tapered structure, i.e. the radial
extension of the fibers which eventually corresponds to the brush
diameter increases from proximal to distal. The main advantage of
such a tapered brush form is that irrespective of the width of the
blood vessel to be cleaned at a time there are always at least some
brush portions the fibers of which are of optimum length. Fibers
have an optimum length for a given blood vessel especially if the
fibers contact the walls of the blood vessel in such a way that
they are not bent in distal direction when the device is moved
proximally. In this case the cleaning efficiency of the fibers is
particularly good. Longer fibers, on the other hand, are bent
distally during the return movement in proximal direction so that
their cleaning efficiency diminishes whereas short fibers may not
even reach the inner wall of the vessel and are thus incapable of
providing a cleaning effect anyway. Due to the fact that with a
tapered brush shape not all fibers are of equal length there are
even in the case of varying blood vessels always at least some
fibers that have an optimum cleaning efficiency.
[0037] Preferred is a tapered distal element (brush) wherein the
radial extension of the fibers increases from proximal to distal.
This can be achieved in that fibers of increasing length are placed
from proximal to distal between the core wires. Such a brush offers
the advantage that should the situation arise the distally arranged
longer fibers are capable of also capturing individual thrombus
fragments if the device is retracted in proximal direction.
However, tapered brushes are also conceivable wherein the radial
extension of the fibers increases from distal to proximal.
[0038] In this case the tapered brushes may be of different shape,
and it will basically be adequate of they are of tapered
configuration. However, also several tapered brushes may be
provided which are interconnected by means of an articulated joint,
or many short tapered segments on a single distal element.
[0039] Additionally or alternatively the fibers in the proximal
area of a distal element may also be designed to be harder than in
the distal area. The harder fibers in the proximal area in this
case mainly serve to scrape off a thrombus adhering to the vessel
wall while the softer fibers in the distal area primarily serve to
secure or retain the thrombus or fragments of a thrombus. Another
possibility warranting that fibers of different length are provided
so that at least some fibers always have an optimum length is to
arrange the individual fibers in such a way that they have a
shorter and a longer side when sticking out on both sides of the
core wires twisted around each other. This can be brought about by
placing the fibers, before the core wires are twisted around each
other, not exactly centered between the core wires but in an
irregular fashion.
[0040] Further possibilities of producing on the distal element
fibers of different length are to use even at the time of twisting
differently long fibers so that an irregular brush structure is
arrived at in this way or to produce tapered brushes the diameter
of which increases from distal to proximal. However, more
advantageous is the variant described heretofore wherein the radial
extension of the fibers increases from proximal to distal because
the longer fibers in this case are situated to the rear when the
device is retracted in proximal direction so that thrombus
fragments may be intercepted in this way.
[0041] To facilitate the capture of a clot (thrombus) the brush of
the distal element may be differently designed along its core. Some
areas, for example, especially the area in the middle of a brush
may be provided with softer fibers, with these fibers serving to
retain the clot. Areas located further proximally or distally
provided with harder fibers on the other hand are rather intended
to produced a more intense cleaning effect.
[0042] A similar effect is achieved if the density of the fiber
coverage in some areas is lower, especially in the middle area of
the distal element, than in other areas. This as well produces the
effect that the proximal and distal areas of the brush where the
fibers are more densely arranged primarily serve to enhance the
cleaning effect on the walls of the vessel whereas the less densely
covered middle area is intended to capture the clot.
[0043] The fibers placed between the twisted core wires are
primarily secured in that they are clamped in place when twisting
is carried out. However, further fixation can be achieved
additionally or alternatively by bonding, knotting and/or fusing
methods.
[0044] The fiber ends located radially outward beneficially are
provided with slubs or thicker nubs, for example of spherical
shape, so that increased surface is available for better clot mass
retention. Another advantage of this embodiment makes it possible
in this way to provide fiber ends that have an atraumatic effect.
The thicker nubs at the ends of the fibers may for example be
produced by cutting the fibers with the aid of methods like
micro-laser cutting, electron beam cutting etc.
[0045] In accordance with another embodiment the fiber ends located
radially outward are at least partially connected with each other
via loops. The fibers connected in this manner thus comprise or are
made up by a single fiber and not two fibers with the single fiber
having a loop-shaped configuration. The fiber emerges from the
core, extends to the outer rim of the brush where it forms into a
loop and then runs back to the core. The fiber in this case extends
such that an elliptical shape is formed. This embodiment offers
advantages in that, similar to the thicker nubs at the end of the
fiber, there is a larger surface available for clot mass retention
which results in the thrombus capturing effect being improved.
Furthermore, the roundness of the loop makes it atraumatic. Also
beneficial is that the fibers have increased stiffness due to the
loop-shaped fiber configuration exhibiting a behavior similar to
that of two fibers arranged side by side.
[0046] As per a further embodiment the core wires in the cross
section of the distal element extend outside the center, i.e. have
eccentric extension. Such a brush with an eccentrically arranged
core has the effect that on one side of the brush relatively short
fibers are located while long ones exist on the other side of the
core. As a result of their short distance to the core the short
ends of the fibers have significantly harder characteristic and the
long fiber ends are significantly softer so that in this case as
well the harder fibers rather improve the cleaning effect whereas
the softer fibers enable a better retention of the captured
thrombus. A brush with eccentrically arranged core offers still
another advantage in that such a brush can be maneuvered past the
side of a clot more easily and then be retracted so that while the
brush moves back in proximal direction the thrombus is
captured.
[0047] The brush-shaped devices described hereinbefore may
basically be used for the filling of aneurysms as well. In such
cases the brushes should be designed in the form of a helix which
are relatively short in comparison to brushes that serve the
purpose of eliminating thrombi. To be able to place the brushes
into aneurysms the distal element(s) have to be designed so as to
be detachable from the guide wire. To be able to fill the aneurysm
more completely the bristles may also be provided with an adhesive
or a thrombogeneous coating.
[0048] The tapered form of a brush as described earlier where the
diameter of the distal element increases from proximal to distal
has turned out to be especially advantageous. Aside from a device
providing for the above described arrangement of fixing the fibers
between two core wires another device is as well basically
conceivable for the removal of foreign objects and thrombi from
body cavities and blood vessel wherein the distal element has a
tapered form, the diameter of the distal element thus increasing
from proximal to distal or vice versa. Preferred is a tapered form
wherein the distal element has a diameter that distally is greater
than proximally.
[0049] In accordance with an alternative embodiment (irrespective
of the brush structure described above) a device with guide wire is
provided for the elimination of foreign objects and thrombi from
body cavities and blood vessels, wherein said device is provided
with a cage structure at the distal end of the guide wire which is
composed of individual braces and suited to be flatly collapsible
under the external strain exerted by a micro-catheter and capable
of being transported inside the micro-catheter and unfolding to its
full cage structure as soon as the external strain caused by the
micro-catheter is omitted, with said cage structure comprising at
least two cages arranged in longitudinal direction one behind the
other.
[0050] Such a device with cage structure for the removal of thrombi
is in principle intended to accommodate thrombi in its interior and
in this way enable thrombi to be eliminated. The cage structure in
collapsed condition is transported inside a micro-catheter through
the blood vessels to the target site where it is then pushed out of
the micro-catheter distally of the thrombus to be removed whereupon
the device unfolds and assumes its full cage structure. The cage
structure may accommodate the thrombi to be removed either
completely or in fragmented form. Subsequently, the device is
retracted through the blood system and, after it has been pulled
into a catheter which may be provided in the form of an additional
guide catheter having a greater inner diameter than the
micro-catheter within which the cage structure was brought to the
target site, finally and completely removed from the blood vessel
system together with the thrombus.
[0051] Generally, the cage structure has an oblong, ship-like
structure of a length ranging between 5 and 50 mm with a diameter
of between 2 and 6 mm in expanded state. The cage structure is
composed of peripheral, in particular longitudinally extending
braces which as a rule are regularly spaced over the
circumference.
[0052] According to the invention this cage structure comprises at
least two cages arranged in longitudinal direction one after the
other so that a double-cage structure is formed. Two or more
successively arranged cages offer the advantage that the cages may
serve different purposes. For example, the proximally arranged cage
may serve as cutting tool for the thrombus or clot that has formed
within the vessel whereas the distal cage serves to accommodate the
thrombus or the fragments of it. Such a fragmentation of the clot
is of special significance if the clot in its entirety is too big
to be accommodated entirely within the cage structure or has
hardened to such an extent that it is very difficult to maneuver it
into the cage structure. It is to be assumed that especially older
thrombi show such hardening tendencies.
[0053] As mentioned earlier, the cage structure is composed of
braces which preferably extend at least partially in longitudinal
direction. It is to be noted in this respect that by `braces
extending in longitudinal direction` not only braces are meant that
are running exactly parallelly to the longitudinal axis but also
those extending at a certain degree of <90.degree. to the
longitudinal axis in distal or proximal direction. It is to be
noted further that in order to form a true cage structure it must
preferably be composed of at least three, but even better of four
to eight braces. It is also considered expedient for the cage
structure and thus the braces to be made of shape-memory material,
preferably nitinol, which enables said structure to be transported
in folded-up condition in a micro-catheter and unfold automatically
when released from the micro-catheter.
[0054] The process of unfolding to the full cage structure upon
omission of the external strain exerted by the micro-catheter must
not necessarily take place automatically but may also be effected
manually. For example, an additional guide wire may be attached to
the cage structure which causes the cage structure to unfold when
being advanced.
[0055] Expediently, a core filament extends centrally through the
cage structure. This core filament constitutes the distal segment
of the guide wire or is a separate core filament serving as
continuation of the guide wire in distal direction.
[0056] Folding up of the cage structure under the influence of the
external constraint caused by a catheter is normally associated
with a stretching of the cage structure. To counteract this
stretching or facilitate radial expansion associated with a
longitudinal contraction when the cage structure is released from
the catheter it will be expedient for the cage structure to be
movably designed allowing it to follow these stretching/contraction
movements. Therefore, the cage structure should be movable relative
to the core filament at least at its proximal end. This can be
achieved in such a manner that the cage structure terminates in a
sleeve at its proximal end through which the core filament movably
extends in longitudinal direction.
[0057] Since with the inventive double-cage structure the cage
arranged further distally shall primarily serve as cutting tool for
the clot to be removed whereas the distal cage is intended to
accommodate the clot, it is considered expedient to appropriately
design the cages such that they can fulfill their duty optimally.
To this end the distally located cage may thus be designed to be
longer for instance to make available sufficient space for the
thrombus to be taken in. On the other hand, the proximal cage
intended to fragment the thrombus may be designed to be shorter in
longitudinal direction.
[0058] Considering the necessity that the proximally arranged cage
must exert such forces on the thrombus that are necessary to
fragment it, it is moreover deemed expedient to design this cage so
as to be harder than the distally arranged cage. A harder design in
this context is to be understood such that the radial forces
required to bring about deformation are higher than the radial
forces necessary to deform the distally arranged cage. By providing
an appropriately hard design for the proximally arranged cage even
very old and already severely hardened thrombi can be scraped off
the vessel wall or fragmented to such an extent that after they
have been accommodated in the distally arranged cage they may be
eliminated from the blood vessel.
[0059] To enable the proximally and distally arranged cages to
fulfill their duty they can be manufactured of different materials,
and for this purpose a harder material should be used for the
proximal cage as mentioned above. For example, different nitinol
materials may be used here, i.e. especially different alloys.
Alternatively or additionally also the braces of which the
proximally arranged cage is formed may have a greater diameter than
the braces of which the distally arranged cage is composed. In this
way it is ensured as well that the proximal cage not only is harder
but also capable of withstanding higher radial forces.
[0060] It is also possible in this context to select a suitable
angle determining the position of the braces in relation to the
longitudinal axis. The braces of which the proximally arranged cage
is made may thus extend in relation to the longitudinal axis at
least partially at an angle greater than that of the braces of the
distally arranged cage which results in the proximally arranged
cage to be less easily collapsible by radial forces. The distally
arranged cage thus has a somewhat flatter structure which will be
noticeable particularly if the distal cage is designed to be longer
than the proximal cage.
[0061] In cases where on account of extraordinarily big thrombi the
amount of clot material to be taken in is particularly great cage
structures may be employed that comprise more than two cages. All
the cages thus provided distally of the proximally arranged cage
will then serve to accommodate clot material.
[0062] As mentioned above, the cages may be composed of braces of
different number with the highest cage density being achieved of
course in the cage that has been provided with the greatest number
of braces. It has turned out, however, that depending on
application it may be expedient not to provide too many braces lest
the proximal opening of the cage structure through which the
thrombus shall enter the cage structure may be too small. Viewed in
the proximal cross section of the cage structure the partial
openings between the braces will be all the greater the fewer
braces are provided. This is of special significance if the
thrombus is rather old and thus firm and coherent and creates
problems when it is attempted to capture it through the openings in
the cage structure. To handle thrombi of this type it has turned
out to be especially advantageous to provide for a number of braces
ranging between four and six.
[0063] Conceivable are of course also combinations configured in
such a way that the proximal cage which the thrombus must first
enter when the cage structure is retracted within the blood vessel
system is provided with fewer braces than the distally arranged
cage which is designed to accommodate the thrombus already
fragmented by the proximal cage.
[0064] The braces of each cage usually meet at the distal and at
the proximal end of the cage each in a point which is preferably
arranged centrally. At the points where the braces converge the
braces may be connected with each other directly or indirectly by
means of a connecting element. If thought expedient the connecting
element may be designed in the form of a sleeve which in relation
to a centrally extending core filament is longitudinally movable so
as to facilitate in this way stretching and contraction of the cage
structure when moved into or out of the catheter.
[0065] Besides the above described approach of reducing the number
of braces there is another method by means of which the proximal
opening of the cage structure can be made larger, said method
providing for the partial openings existing between the braces to
be enlarged at least partially, so that in this manner a strongly
coherent thrombus is allowed to enter more easily. For this purpose
the large partial openings existing between the braces are enlarged
which in turn causes the size of small partial openings to reduce.
This can be brought about by arranging the braces of at least one
cage, preferably the proximally arranged cage, such that they
extend, with the cage structure unfolded, from the point where the
braces at the proximal cage end converge, in groups along a first
section, e.g. in pairs close to each other in distal direction,
then diverge distally to this first section, and in a second
section distally to the first section extend equally distributed in
distal direction over the circumference of the cage. In other
words, the braces do not uniformly extend along the entire cage
equally spaced over the circumference but such an equal
distribution is provided in distal direction only some distance
away from the proximal opening. Due to the fact that the braces at
the proximal end of the cage initially are grouped close to each
other, partial openings are created the size of which giving the
impression as if only half or a third of the number of braces were
used. In case a total of four braces are provided two pairs of
braces each run together for example at the proximal opening so
that two significantly enlarged partial openings are created which
are almost semicircular whereas the remaining small partial
openings left between the braces closely adjacent to each other can
be neglected. Similarly, if a total of six braces are provided with
said braces initially extending in pairs, partial openings almost
the size of a third of a circle would be produced. If along the
first section three braces each are arranged close to each other in
distal direction, two almost semicircular openings are even created
if six braces are provided. Basically, such an approach providing
for the partial openings to be enlarged in part is of course also
conceivable in the event of cage structures that merely consist of
a single cage.
[0066] The braces forming the cages may be of identical design for
the proximal and distal cage. In this case the braces will extend
from the proximal end of the proximally arranged cage to the distal
end of the distally located cage. To make sure that the braces form
a double-cage structure and do not merely build up a greatly
extended cage they will preferably cross each other at least
partially so that the junction point where the braces meet
constitutes the distal end of the proximally arranged cage and at
the same time the proximal end of the distally located cage. Such
an embodiment offers the advantage that the radial forces being
exerted on the distal cage and on the proximal cage will influence
each other because the radial forces in the braces are transmitted
to the other cage. In this manner the device may retain its
unfolded shape even if the nominal diameter cannot be realized in a
given vessel. This is particularly true if the measures for a
length adjustment of the cage structure as described hereinbefore
have been provided.
[0067] At the junction point the braces may be interconnected
and/or attached to the core filament. Preferably, no connection
will be provided, however, because the radial forces effect will
not be disturbed in this manner.
[0068] Furthermore, the radial forces may also be influenced by not
entirely pushing the device out of the micro-catheter. For example,
if only the distal cage is moved out whereas the proximal one is
kept within the micro-catheter the radial force of the distally
arranged cage increases. This may be advantageous in the event
especially firm clots/thrombi have to be retrieved.
[0069] The radial forces will influence each other particularly
well if from the proximally arranged cage to the next distally
located cage the braces are run to the opposite side of the cage
structure, i.e. if there is an offset by 180.degree. from one cage
to the next.
[0070] The cage arranged farthest in distal direction may
expediently be designed to have a net structure at least distally
so as to provide increased safety against losing thrombus fragments
that may slip out of the cage when the device is retracted out of
the blood vessel. This net structure may in particular be composed
of braided wire for which, same as for the braces, nitinol can be
used. Expediently, such a net structure of a cage is arranged
especially at the distal end because for the removal of the
thrombus the cage structure after all is moved in proximal
direction so that a net structure located at the proximal end of
the cage would be less desirable as it could in fact prevent the
thrombus from entering the cage. Accordingly, the net structure
should only be located at the distal end of the cage or should
become more fine-meshed from proximal to distal. Moreover, a
greater mesh size in the proximal area of the cage facilitates the
retraction of the cage into the catheter with the structures
collapsing and containing the thrombus.
[0071] A function similar to that of the net structure just
described can also be achieved by providing a cover on the distal
side of the distally arranged cage in the form of a polymer skin.
Providing such a polymer skin which may for example consist of
expanded PTFE (polytetrafluoroethylene) results in the distal end
of the cage forming a bag-like structure. The polymer skin in this
case extends from the distal tip of the cage along the braces on to
a desired position, for example to roughly the middle of the cage.
At the distal end of the cage the polymer skin may be provided with
one or several openings of a size big enough to allow liquid,
especially blood, to pass through without difficulty whereas the
thrombus or fragments of a thrombus captured by means of the cage
structure are retained. This is advantageous, in particular, when
the cage structure is retracted because such a configuration will
in fact not impair the flow of blood while the thrombus itself can
be completely eliminated from the blood vessel system.
[0072] As per another beneficial embodiment the braces of the cage
structure are arranged in a helical fashion, i.e. the distal end
and the proximal end are offset against each other by an angle
ranging between 45.degree. and 180.degree., preferably by approx.
90.degree.. Such a helical line arrangement allows a thrombus
adhering to a vessel wall to be sheared or cut off when the cage
structure is moved forward without the necessity of having to turn
to device.
[0073] In accordance with another variant the braces extend along a
wave line with a lateral deflection of between 45.degree. and
90.degree., i.e. the braces at first extend in lateral direction
until they have reached for instance a point offset by 90.degree.
to the starting point and then along the second half of their
length extend back to the starting point. In this case the proximal
end and the distal end are not offset against each other.
[0074] In accordance with an especially preferred embodiment the
device not only comprises a cage structure arranged at the distal
end of the guide wire but in the area of the cage structure has
additionally been provided with fibers or bristles projecting
radially outward, with said fibers or bristles being arranged
individually or in bundles.
[0075] The fibers or bristles are connected with a distal element
of the guide wire in a manner known per se, for example, as is
known from the fabrication of fiber-equipped embolization spirals.
This may be achieved through entwinement with the distal element,
by gluing, welding or any other suitable fastening method.
[0076] Advantageously, the device is provided with one or several
radiopaque markers. These may, for example, be made of platinum or
a platinum alloy. Radiopaque markers of this kind may be located
both in areas from which the fibers or bristles emanate and as well
on the cage structure to enable the attending physician to monitor
the treatment with the help of image-forming methods conducive to
the purpose.
[0077] Moreover, it is considered advantageous if the tip of the
entire device is designed so as to be atraumatic, i.e. is rounded
off for example.
[0078] The distal element of the device which is provided with
fibers expediently extends centrally in the cage structure, i.e.
the fiber-covered element is in fact located in the center of the
cages. In this manner, the beneficial effect of the cage structure
on the one hand and those of the fibers arranged on the distal
element on the other are combined with each other. This design
enables the captured thrombus to be secured and retained most
safely both by means of the cage structure and the fibers so that
the thrombus can be retrieved and drawn into a catheter.
[0079] The fibers or bristles may be arranged on and attached to in
particularly one or several movable filaments located on the core
filament extending through the cage structure so that the
fibers/bristles virtually stick out radially from the cage
structure in radiated form. The movable filament may, for example,
consist of a helically wound wire. Alternatively or additionally,
fibers or bristles may also be secured to the braces of the cage
structure.
[0080] It shall, furthermore, be observed also with respect to the
embodiment of the invention relating to a cage structure that with
respect to the fibers all comments made hereinbefore in the context
of the brush-like distal element shall apply as well, in particular
regarding the material used for the fibers, the angular alignment,
the length of the fibers, the coating of the fibers, the use of
radiopaque markers etc.
[0081] Moreover, all the described embodiments of the invention may
be combined with each other. Especially, the embodiment providing
for a double-cage structure may have additional fibers, whereas, on
the other hand the embodiment providing for fibers emanating from
the distal element may additionally have a cage structure. In
particular, a combination of double-structure and distal element
composed of core wires twisted around each other with outwardly
protruding fibers is also possible.
[0082] Eventually, the invention also relates to the combination of
the device with a guide and/or micro-catheter in which the device
is maneuvered to the application site and when filled with the
thrombus removed from the blood vessel system. It may be expedient
to additionally design the catheter in the form of an aspiration
catheter capable of accommodating micro-catheters.
[0083] The above described invention is of special significance to
the removal of thrombi from vessels of especially small lumen, in
particular intracranial. The invention may of course be used also
for the elimination of thrombi from other parts of the body, for
example the heart, lungs, legs etc. However, the invention may also
be used for the removal of other foreign objects from blood
vessels, for example removing embolization spirals and stents.
[0084] Further elucidation of the invention is provided by way of
examples through the enclosed figures, where
[0085] FIG. 1 shows the making of a brush-like distal element;
[0086] FIG. 2a is a longitudinal section of the distal element;
[0087] FIG. 2b is a longitudinal section of the distal element;
[0088] FIG. 2c is a cross-sectional view of the distal element;
[0089] FIG. 3 shows an embodiment with tapered brush;
[0090] FIG. 4 is a longitudinal view of another embodiment of the
distal element;
[0091] FIG. 5 shows a distal element provided with a wave-like
core;
[0092] FIG. 6 shows a helically extending core;
[0093] FIG. 7 illustrates a helically extending core with outwardly
protruding fibers;
[0094] FIG. 8 shows an embodiment with two distal elements arranged
in succession;
[0095] FIG. 9 shows an embodiment with two distal elements arranged
one after the other and additional braces;
[0096] FIG. 10 shows another embodiment with two distal elements
arranged one after the other and with additional braces;
[0097] FIG. 11 shows an embodiment with tapered brush elements;
[0098] FIG. 12 shows a further embodiment with tapered brush
elements;
[0099] FIG. 13 shows an embodiment with fibers having different
hardness characteristics;
[0100] FIG. 14 shows an embodiment with a fiber coverage of
different density;
[0101] FIG. 15a is a longitudinal view of an embodiment with
eccentrically arranged core;
[0102] FIG. 15a is a cross-sectional view of an embodiment with
eccentrically arranged core;
[0103] FIG. 16 shows an embodiment with cage structure and brush
element;
[0104] FIG. 17a is a side view showing a double-cage structure;
[0105] FIG. 17b shows the double-cage structure of FIG. 17a viewed
from distal end;
[0106] FIG. 18a shows another side view of a double-cage
structure;
[0107] FIG. 17b illustrates the double-cage structure of FIG. 18a
viewed from distal end;
[0108] FIG. 19a is the proximal view of a cage structure in
accordance with an embodiment;
[0109] FIG. 19b is the proximal view of a cage structure in
accordance with an alternative embodiment;
[0110] FIG. 20a is the proximal view of a cage structure in
accordance with another embodiment;
[0111] FIG. 20b is the proximal view of a cage structure in
accordance with another embodiment;
[0112] FIG. 20c is the proximal view of a cage structure in
accordance with another embodiment;
[0113] FIG. 21 is a side view of the cage structure shown in FIG.
20a;
[0114] FIG. 22 shows a side view of another embodiment of the
invention.
[0115] The invention is elucidated by way of FIG. 1 which shows two
core wires 14 arranged in parallel, with orthogonal fibers 6 being
arranged between the two core wires 14. Subsequently, the core
wires 14 are restrained at location 15 and twisted around each
other by performing a torsional movement T. In this way a
brush-like distal element 27 is obtained from which fibers 6 are
projecting radially outward.
[0116] When core wires 14 have been twisted around each other the
distal element 27 appears as shown in FIGS. 2a to 2c, said FIGS. 2a
and 2b being longitudinal sections, whereas FIG. 2c shows a view
from the proximal or distal end. It can be seen that the fibers 6
are equally distributed over the circumference of the distal
element 27 and protude radially outward.
[0117] In FIG. 3 an embodiment is shown wherein the brush-like
distal element 27 is has a tapered shape, i.e. its diameter
increases from proximal to distal. The proximal diameter A
typically ranges between 1 and 3 mm, the distal diameter B between
2 and 5 mm. The length of the distal element 27 is in the range of
between 10 and 20 mm, the length D of guide wire 18 for example is
3000 mm. As a rule, core 14 will consist of core wires twisted
around each other, however tapered brush forms provided with fibers
6 attached to core 14 by some other method are conceivable as well.
Moreover, the device is fitted with radiopaque markers 9 arranged
at the proximal and distal end of the distal element 27.
[0118] FIG. 4 illustrates another embodiment of the inventive
distal element 27 wherein fibers 6 are shown as a consistent,
homogeneous area produced on account of the density of the fiber
coverage. In this case the core wires 14 at the distal end of the
distal element are connected with each other via a loop 16 so that
in fact a single core wire 14 exists that extends from proximal to
distal where it forms into a loop and then extends back in proximal
direction. In this way both ends of core wire 14 are thus twisted
around each other.
[0119] It is also evident from FIG. 4 how the distal element 27 can
be attached via a helix 17 to other components of the device
located farther proximally, in particular to a guide wire 28.
[0120] In FIG. 5 an extension of core wire 14 is shown in a
wave-like or sine-wave form. Fibers 6 as well follow this wave-like
extension which is thus provided for the entire distal element 27.
In comparison to core wires 14 of straight configuration this
results in an improved cleaning efficiency.
[0121] From FIG. 6 a helical secondary structure of core 14 can be
seen, with the fiber structure not being shown here for the sake of
simplifying the representation. It is to be noted in this case as
well that core 14 is also composed of at least two core wires 14
twisted around each other and forming a primary helix comprising of
twisted core wires 14. The secondary helix shown in FIG. 6 must
therefore not be confused with a primary helix arrived at by
twisting core wires 14 together. A helical structure of the distal
element offers advantages in that the inner walls of vessels are
cleaned more efficiently and, moreover, such an embodiment may
serve to place shorter brushes into an aneurysm for the purpose of
occluding the same.
[0122] Another representation of a helical distal element can be
seen from FIG. 7 which is a longitudinal section showing the fiber
coverage 6 as a schematic view.
[0123] FIG. 8 shows an embodiment of the invention consisting of
several distal elements 27. Each distal element 27 is composed of
core wires 14 twisted around each other and provided with a fiber
coverage 6. Distal elements 27 in this case are connected with each
other by articulated joint 20 so that a certain degree of
flexibility is achieved when advancing and retracting the device
within vessels. At the proximal end the distal element is attached
via a coil 17 to a push or guide wire 18. At the distal end the
device is provided with a rounded tip 19. Since fibers 6 of the two
distal elements 27 have different characteristics in this example,
a different color shading has been selected here.
[0124] Another embodiment is shown in FIG. 9 which shows several
distal elements with said embodiment largely corresponding to the
one depicted in FIG. 8. However, the device additionally has braces
21 extending from the distal end of the distal element 27,
projecting radially outward and again joining centrally at the
proximal end of the distal element 27. The radial extension of the
braces 21 in this case coincides with the radial extension of the
fibers 6. Such an embodiment comprising additional braces 21 serves
to improve the guidance of the system within the vessel.
[0125] Another embodiment with braces can be seen from FIG. 10
wherein the braces 21 extend along and over all distal elements 27.
Additional stabilization in this case is obtained, however, by
providing intermediate braces 22.
[0126] In FIG. 11 an embodiment with two distal elements is shown
with each distal element 27 having a tapered structure. The radial
extension of the fibers of distal elements 27 increases here from
proximal to distal, i.e. in each case the distal elements 27 are
wider in the distal than in the proximal area. Such an embodiment
has the benefit in that irrespective of the blood vessel width
fibers 6 are always available that are of optimum length.
[0127] In FIG. 12 another embodiment is shown wherein within each
distal element 27 the radial extension of the fibers increases from
proximal to distal several times. Accordingly, each distal element
27 consists of several tapered brushes.
[0128] FIG. 13 illustrates an embodiment wherein the center area 24
of the distal element 27 has been provided with softer fibers,
whereas in the proximal as well as distal area 23 harder fibers
have been arranged. In this case the center area 24 primarily
serves to accommodate clots while the proximal and distal areas 23
are designed to intensify the cleaning effect.
[0129] Likewise, the embodiment shown in FIG. 14 serves a similar
purpose with the exception that a similar effect is brought about
here due to the fiber coverage in area 26 being thinner than in
proximal and distal areas 25.
[0130] From FIGS. 15a and 15b a distal element 27 can be seen as a
longitudinal section as well as a proximal/distal view wherein the
twisted core wires 14 extend eccentrically. Accordingly, fibers 6
project significantly farther on one side than on the other. This
is especially advantageous if the distal element 27 must be moved
laterally past a thrombus.
[0131] FIG. 16 shows an embodiment wherein a cage structure 3 has
been combined with a brush structure. The distal element 27 here
also consists of core wires 14 twisted around each other and fibers
6 radially projecting outward, with said element being arranged
proximal to cage 3. The cage 3 has a polymer skin 10 with
transverse braces 11 connecting the polymer skin 10 with braces 4.
Furthermore, the device comprises radiopaque markers 9 and a guide
wire 18. Upon retraction of the device in proximal direction a
thrombus is initially captured and secured by means of the distal
element 27 via fibers 6. In the event individual thrombus fragments
become split off these are retrieved by action of the distally
arranged cage structure 3 with its polymer skin 10 because polymer
skin 10 is purposefully designed to form a pocket. As a result of
brush structure and cage structure being combined an especially
advantageous device for the removal of thrombi is provided.
[0132] As per an alternative embodiment of the invention FIG. 17a
represents a cage structure 1 consisting of a proximal cage 2 and a
distal cage 3 in accordance with the invention. The two individual
cages 2, 3 in this case are formed in that the braces 4 that form
the cages 2, 3 cross each other at the center, with said braces of
the proximal cage 2 being offset in relation to the distal cage 3
by 180.degree. each. A core filament 5 extends centrally through
the cage structure 1 and is connected to braces 4 at the distal end
whereas the braces 4 at the proximal end are movably designed in
relation to the core filament 5. In this way the cage structure 1
is capable of being moved to a certain extent in longitudinal
direction which is important when the cage structure 1 is moved
into or discharged out of a micro-catheter.
[0133] Since both cages 2, 3 are formed by the same braces 4 it is
ensured that radial forces are transmitted from one cage to the
next, and, for example, radial forces acting on the proximal cage 2
increase the outwardly acting radial forces exerted by the distal
cage 3. For example, for the retrieval of particularly firm thrombi
only the distal cage 3 may be pushed out of a micro-catheter while
the proximal cage 2 is left inside the micro-catheter so that as a
result of the external constraint the micro-catheter exerts on the
proximal cage 2 the outwardly acting radial force of distal cage 3
is significantly increased.
[0134] It must be pointed out in this context that FIG. 17a is
merely a schematic representation which only show two braces 4. For
the formation of the cage structure 1 more braces 4 are usually
used, for example three to six braces 4.
[0135] FIG. 17b shows the cage structure 1 of FIG. 17a viewed from
the distal end. The core filament 5 extends through the center
whereas, viewed in longitudinal direction, the braces 4 turn around
the core filament 5 forming a right-hand helix.
[0136] FIG. 18a is a side view of another cage structure 1 wherein
the proximal cage 2 is arranged on the left-hand side and the
distal cage 3 on the right-hand side. Four braces 4 each are shown
here that form both cages 2, 3 and intersect at a junction point 8
located between the two cages 2, 3. Through the cage structure 1 a
core filament 5 extends on which filaments 7 are arranged movable
in longitudinal direction, said filaments being reinforced through
fibers 6 projecting radially outward. These fibers 6 are flexible
such that when the device is moved forward through a micro-catheter
they fold in the direction of the longitudinal axis but when the
device has been discharged from the micro-catheter assume an
upright position. Fibers 6 serve the purpose of additionally
securing a captured thrombus and, moreover, have a stabilizing
effect which results from the thrombogeneous coating of the fibers
6. Both at the distal end and at the proximal end of the cage
structure 1 radiopaque markers 9 are arranged by means of which the
system can be monitored with the aid of image-forming methods. Core
filament 5 is interrupted at the point marked by a circle so that
upon contraction or unfolding of the cage structure 1 the proximal
portion of the core filament 5 is allowed to move to and from in
longitudinal direction within the filament 7. In this manner the
longitudinal expansion and contraction of the cage structure 1 is
significantly facilitated. The radiopaque marker 9 located at the
distal end of the device has a rounded tip which has an atraumatic
effect.
[0137] FIG. 18b is a view of the cage structure 1 illustrated in
FIG. 18a as seen from the distal end showing six braces 4 equally
distributed over the circumference. Fibers 6 in this case are
arranged in bundles projecting radially outward. Core filament 5
again forms the longitudinal axis.
[0138] In FIGS. 19a and 19b views of proximal openings of a cage
structure can be seen, with the cage structure shown in FIG. 19a
being composed of four, the cage structure in FIG. 19b of six
braces 4. On the one hand, using six braces 4 brings about a more
enclosed cage structure 1, but if only four braces 4 are arranged
the proximal openings of the cage structure 1 between braces 4 will
be significantly larger. The latter arrangement may be advantageous
in the event of especially firm and coherent thrombi because in
this manner the thrombus can be more easily maneuvered through the
proximal opening into the cage structure 1.
[0139] In FIGS. 20a, 20b and 20c an alternative arrangement is
illustrated by means of which the partial openings 12, 13 existing
between the braces 4 can be made larger. In this case, the braces 4
at the proximal end of the cage structure 1 emanate from a common
point and initially extend in distal direction in groups close to
each other and in parallel before they diverge at a point somewhat
farther distally of a first section and finally assume their end
position in which the braces 4 are equally distributed over the
circumference of the cage. If four braces are used four partial
openings are obtained as already shown in FIG. 19a but due to the
novel configuration of the braces the large partial openings 12 are
significantly enlarged whereas the size of the small partial
openings 13 is considerably reduced. On account of braces 4
extending close to each other in pairs and parallel partial
openings 12, 13 are created which almost coincide with the partial
openings that would exist if only half the number of braces 4 were
used, i.e. in FIG. 20a the proximal opening is cut into halves
nearly, in FIG. 20b where six braces 4 are shown approximately into
thirds. In FIG. 20c three braces 4 each initially extend in groups
close to each other so that two approximately semicircular partial
openings 12 are created although a total of six braces 4 are
arranged.
[0140] FIG. 21 again illustrates as a side view the cage structure
1 shown in FIG. 20a where it can be seen that starting out from
marker 9 the braces 4 initially extend parallelly in pairs before
they diverge and are equally distributed over the circumference of
the cage structure 1. It is to be observed in this case that FIG.
21 only shows one cage of the cage structure 1 with the center
portion having been omitted.
[0141] From FIG. 22 another cage structure 1 can be seen with only
the distal cage 3 being shown here. Said cage consists of four
braces 4 extending between two radiopaque markers 9. Core filament
5 runs centrally through the cage structure 1. The special feature
of the embodiment shown in FIG. 22 is the polymer skin 10 arranged
at the distal end of the cage structure 1. Arranged transversely to
braces 4 cross braces 11 can be seen which in each case constitute
the limit of the polymer skin 10 in proximal direction. This design
provides for a pocket being formed at the distal end of the cage
structure 1 which serves to accommodate a thrombus. The
transversely extending connecting braces 11 serve to stabilize the
edge structure of the polymer skin 10 and additionally secure the
braces in relation to each other.
* * * * *