U.S. patent application number 17/395789 was filed with the patent office on 2021-11-25 for catheters and devices and systems incorporating such catheters.
This patent application is currently assigned to Perfuze Limited. The applicant listed for this patent is Perfuze Limited. Invention is credited to Andrew CRAGG, Alejandro ESPINOSA, Robert FARNAN, Dara FINNERAN, John LOGAN, Liam MULLINS, Brett NAGLREITER, Lisandro RIVERA.
Application Number | 20210361910 17/395789 |
Document ID | / |
Family ID | 1000005764449 |
Filed Date | 2021-11-25 |
United States Patent
Application |
20210361910 |
Kind Code |
A1 |
MULLINS; Liam ; et
al. |
November 25, 2021 |
CATHETERS AND DEVICES AND SYSTEMS INCORPORATING SUCH CATHETERS
Abstract
A catheter has a jacket (10, 11, 5) defining a lumen and a
helical support (6). The catheter has a proximal portion (4) and a
distal portion (3), the distal portion having for at least some of
its length a corrugated outer surface. A transition portion has a
flexural stiffness which is less than that of the distal portion
and more than that of the proximal portion. The transition portion
provides an optimum transition in flexural stiffness by way of
features of the jacket including geometry of jacket corrugations
(15), or overlapping tubular layers (1073, 1074). The distal end of
the distal portion may have an extension of liner material folded
over (1072, 1082) to provide a particularly soft tip. In other
examples the liner is terminated (763) before the distal tip. The
catheter is particularly suited to an aspiration device (1350) with
a flow restrictor (1353) and the distal portion distal of the flow
restrictor. An aspiration system (3500) may employ the catheter
with a pump which dynamically applies negative or positive pressure
to optimally aspirate a clot.
Inventors: |
MULLINS; Liam; (Galway,
IE) ; FINNERAN; Dara; (County Roscommon, IE) ;
ESPINOSA; Alejandro; (Miami, FL) ; RIVERA;
Lisandro; (Miramar, FL) ; FARNAN; Robert;
(Fort Lauderdale, FL) ; NAGLREITER; Brett;
(Miramar, FL) ; LOGAN; John; (Plymouth, MN)
; CRAGG; Andrew; (Edina, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Perfuze Limited |
Dangan |
|
IE |
|
|
Assignee: |
Perfuze Limited
Dangan
IE
|
Family ID: |
1000005764449 |
Appl. No.: |
17/395789 |
Filed: |
August 6, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16817787 |
Mar 13, 2020 |
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17395789 |
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PCT/EP2018/085064 |
Dec 14, 2018 |
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16817787 |
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62616188 |
Jan 11, 2018 |
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62599573 |
Dec 15, 2017 |
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62599560 |
Dec 15, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 25/0012 20130101;
A61B 2017/22067 20130101; A61M 25/0108 20130101; A61M 25/0054
20130101; A61B 17/22 20130101; A61B 2017/22079 20130101; A61L 29/06
20130101; A61M 25/005 20130101 |
International
Class: |
A61M 25/00 20060101
A61M025/00; A61B 17/22 20060101 A61B017/22; A61L 29/06 20060101
A61L029/06; A61M 25/01 20060101 A61M025/01 |
Claims
1. A catheter (1) comprising a jacket defining a lumen and
comprising a helical support in jacket material along at least some
of its length, the catheter comprising at least a proximal portion
(2) and a distal portion (3), said distal portion having for at
least some of its length a corrugated outer surface (15).
2-135. (canceled)
Description
INTRODUCTION
Field of the Invention
[0001] The present disclosure relates to catheters and to devices
and systems incorporating such catheters, and to their methods of
use. An example is a flexible catheter for endovascular
procedures.
Prior Art Discussion
[0002] Most endovascular procedures require the use of flexible
catheters, for example, to deliver contrast injection, to deliver
implantable devices, perform vascular procedures, or to aspirate.
Due to the tortuous nature of the vasculature, it is important for
catheters to be flexible enough to travel through vessels without
excessive force. However, there is generally a trade-off between
the features of catheter diameter, trackability, flexibility, and
kink resistance. An increase in catheter diameter tends to increase
its stiffness, which lowers its trackability and may dangerously
increase vascular sheer forces. An increase in flexibility tends to
increase the tendency of the catheter to kink as it is pushed
through the vasculature, which limits the catheter to vessels with
gentle curves. In general, a decrease in wall thickness increases
flexibility and allows access to more tortuous vessels, there being
a trade-off between flexural stiffness and kink resistance.
[0003] The invention is directed towards providing a catheter with
improved properties for desired flexural stiffness and flexibility,
to thereby allow use in difficult locations such as where there are
significant curves and small dimensions in the patient vessels.
SUMMARY OF THE INVENTION
[0004] A catheter has a jacket defining a lumen and a helical
support. The catheter has a proximal portion and a distal portion
the distal portion having for at least some of its length a
corrugated outer surface. A transition portion has a flexural
stiffness which is less than that of the distal portion and more
than that of the proximal portion. The transition portion provides
an optimum transition in flexural stiffness by way of features of
the jacket including geometry of jacket corrugations, or
overlapping tubular layers. The distal end of the distal portion
may in some examples have an extension of liner material folded
over to provide a particularly soft tip. In other examples the
liner is terminated before the distal tip. The catheter is
particularly suited to an aspiration device with a flow restrictor
and the distal portion distal of the flow restrictor. An aspiration
system may employ the catheter with a pump which dynamically
applies negative or positive pressure to optimally aspirate a
clot.
[0005] In one aspect we describe a catheter comprising a jacket
defining a lumen and comprising a helical support in jacket
material along at least some of its length, the catheter comprising
at least a proximal portion and a distal portion, said distal
portion having for at least some of its length a corrugated outer
surface. The catheter preferably comprises a transition portion
between said proximal portion and said distal portion, said
transition portion having a flexural stiffness which is less than
that of the distal portion and more than that of the proximal
portion. The transition portion preferably has a corrugated outer
surface in which at least some corrugations of the corrugated outer
surface have a smaller depth and/or width than corrugations of the
surface of the distal portion.
[0006] Other aspects of the catheter are set out in the attached
claims 4 to 88.
[0007] We also describe a method of manufacturing a catheter of any
embodiment, wherein the jacket is formed in at least some regions
by positioning a membrane over a helical structure, applying heat
so that the membrane reflows such that it forms around the helical
structure, winding a tensioned cinch wire around the outside of the
membrane such that it forces membrane material into grooves between
each loop of the helical structure, heat setting the membrane to
fix the corrugations in place, and unwinding the tensioned cinch
wire leaving the corrugations behind.
[0008] The jacket may include fluoropolymers and said
fluoropolymers may be bonded with each other and/or with other
polymers at bonding interfaces. Chemical treatment may be applied
at said interfaces using an etching solution. The etched
fluoropolymer may be coated with a thin layer of urethane such as
Chornoflex, and on the application of heat, this layer flows and
acts to tie the fluoropolymer to a second etched fluoropolymer
layer or to a different polymer layer.
[0009] In one aspect, the method comprises providing the helical
support within a polymer jacket which is bonded to a liner to form
a base assembly, placing an outer liner which will not bond to the
polymer jacket over the jacketed coil, winding the cinch wire in a
helix onto the outside of the outer liner under tension thereby
imparting a corrugate geometry, heating to reflow or anneal the
material to set said material into the corrugate geometry, cooling
the assembly, removing the cinch wire, and peeling off the outer
liner.
[0010] We also describe an aspiration device comprising a catheter
of any embodiment described herein and a flow restrictor, in which
the distal portion is distal of the flow restrictor. The catheter
may comprise a transition portion between said proximal portion and
said distal portion, said transition portion having a flexural
stiffness which is less than that of the distal portion and more
than that of the proximal portion, and at least part of said
transition portion extends distally of the flow restrictor.
[0011] The flow restrictor may comprise a balloon and the balloon
is arranged to inflate to block blood flow before aspiration of a
clot into the catheter distal portion. Alternatively it may be used
to block blood flow before precise delivery of an embolic agent to
region of the vasculature, tumour, or organ.
[0012] Length of the distal portion is in one case suited to reach
specific anatomical locations, such as the distal internal carotid
artery, terminus of the internal carotid artery, proximal M1,
distal M1, proximal M2, distal M2, basilar, or vertebral vessels,
wherein the flow restrictor remains in or proximal of the C1
segment of the ICA.
[0013] Various aspects of the aspiration device are set out in
appended claims 94 to 110.
[0014] We also describe a method of use of an aspiration device of
any embodiment, the method comprising steps of deploying the
aspiration device in a patient's blood vessel, navigating the
distal portion to a clot in the vessel, causing the flow restrictor
to block blood flow, applying a vacuum to the catheter so that the
clot is aspirated into the distal portion.
[0015] In one example, the method comprises: [0016] performing an
angiogram to determine location of an occlusion, and distance
between petrous or cavernous carotid and the occlusion, [0017]
choosing a catheter with a distal portion length suitable to reach
a clot causing the occlusion, while ensuring that the flow
restrictor does not land beyond the cervical carotid, [0018]
navigating the distal portion of the catheter to the clot, [0019]
activating the flow restrictor such that flow arrest is enabled,
and alternative flow pathways which could reduce the effectiveness
of the aspiration are minimised, [0020] applying a vacuum to the
lumen of the catheter to aspirate the clot, [0021] if the clot is
retrieved, performing another angiogram through the balloon guide
catheter or a diagnostic catheter, and [0022] removing the
catheter.
[0023] We also describe an aspiration system comprising a catheter
of any embodiment, a pump linked with the catheter proximal
portion, and a controller arranged to vary aspiration pressure
during aspiration of a clot. The system may comprise a lumen
pressure senor and the controller is configured to vary aspiration
pressure according to sensed pressure within the catheter lumen.
The system may comprise a lumen fluid flow sensor, and the
controller is configured to vary aspiration pressure according to
sensed fluid displacement in the lumen.
[0024] The controller may be configured to improve the efficiency
of aspiration by preventing clogging of the catheter, and/or to
promote maceration and deformation of a clot to enable it to travel
through the lumen.
[0025] Various aspects of the aspiration system are set out in the
appended claims 113 to 135.
[0026] We also describe methods of use of an aspiration system of
any embodiment, in which the controller varies aspiration pressure
during aspiration of a clot. There may be a lumen pressure senor
and the controller varies aspiration pressure according to sensed
pressure within the catheter lumen. There may be a lumen fluid flow
sensor, and the controller varies aspiration pressure according to
sensed fluid displacement in the lumen. Preferably, the controller
improves efficiency of aspiration by preventing clogging of the
catheter, and/or promotes maceration and deformation of a clot to
enable it to travel through the lumen. Also, the controller may
provide a vacuum or a positive pressure based on measured pressure,
and change direction hence altering the pressure and fluid
displacement.
[0027] The controller may have defined upper and lower limits of
pressure or displacement to decide whether to apply a vacuum or
pressurize, and/or it may cause the catheter to cyclically ingest
and if required expel, at least some of a clot, whereby there is
deformation of the clot to improve efficiency of aspiration and
prevent clogging of the catheter. The controller may begin to draw
some vacuum so that a negative pressure is measured and in the
absence of an occlusion or partial occlusion of the catheter tip,
this will be a nominal reading, representing free-flow of fluid
through the catheter, and once the catheter is advanced and engaged
with the clot, an increase in the vacuum is observed.
[0028] The controller may increase a vacuum to ingest more of a
clot and reverse at a low limit of pressure defined such that
during vacuum, a portion of the clot has been aspirated but not so
much that the clot has become irreversibly clogged and the lower
limit of vacuum can be set above a full vacuum pressure to prevent
ingestion of too large a clot that could clog the catheter.
[0029] Other aspects of the method of operation of the aspiration
system are set out in the attached claims 113 to 135. For example,
the controller may set the low limit between -100 mm-HG and -200
mm-Hg, preferably between -200 mm-HG and -300 mm-Hg, more
preferably between -400 mm-HG and -500 mm-Hg, and more preferably
between -600 mm-HG and -700 mm-Hg; and it may cause direction of
fluid displacement of the pump to be reversed thereby increasing
the pressure measured, and unloading a clot.
DETAILED DESCRIPTION OF THE INVENTION
Brief Description of the Drawings
[0030] The invention will be more clearly understood from the
following description of some embodiments thereof, given by way of
example only with reference to the accompanying drawings in
which:--
[0031] FIG. 1 is a schematic cross-sectional view of a distal end
of a catheter;
[0032] FIG. 2 is a cross-sectional view of a catheter wall portion
having varying depths of corrugation;
[0033] FIG. 3 illustrates an outer surface of the catheter shown in
FIG. t;
[0034] FIG. 4 is a cross-sectional view of the full catheter shown
in FIG. 1;
[0035] FIG. 5 is a schematic cross-sectional view of a catheter
wall portion having an outer tubular layer bonded with an inner
tubular layer;
[0036] FIG. 6 is a schematic cross-sectional view of a transition
between a distal wall portion and a proximal wall portion;
[0037] FIG. 7 is a schematic cross-sectional view of another
transition between a distal wall portion and a proximal wall
portion;
[0038] FIG. 8 shows force measured at a 1 mm displacement in a
3-point bend test of a conventional catheter design (0.80 A
urethane jacket over a 0.005 in NiTi coil over on a 0.001 in PTFE
Liner), and highly flexible corrugated ePTFE design;
[0039] FIG. 9 shows behaviour of a conventional catheter under
compression when pushed against restriction, and FIG. 10 shows
behaviour of a corrugated catheter under compression when pushed
against a restriction;
[0040] FIG. 11 shows in a catheter use of progressively more
flexible (or less "pushable") sections of catheter wall within the
distal tip, distally of a proximal portion;
[0041] FIG. 12 is a section through an outer wall having a
corrugated surface, with an inner liner;
[0042] FIG. 13 shows a section through a catheter in which the
inner liner terminates before the of the catheter
[0043] FIG. 14 shows a cross section of the catheter where the
helical support is not exposed to the inner lumen of the
catheter.
[0044] FIG. 15 show further constructional details of catheter
walls to achieve desired flexibility at the proximal and distal
portions;
[0045] FIG. 16 shows an outer tubular layer added to the outside of
the corrugated structure which embeds the helical support to
further increase the stiffness of a section of the catheter
proximally of the distal end;
[0046] FIG. 17 shows steps for manufacture of a corrugated polymer
jacketed catheter section;
[0047] FIG. 18 shows a catheter portion with a liner, a coil and
inner and outer tubular layers respectively and in-fill for
increased stiffness;
[0048] FIG. 19 shows both the inner and outer tubular layer
thickness being increased; in this instance the coil may be
floating or constrained between the outer layer and inner
liner;
[0049] FIG. 20 shows a catheter portion having a liner, an outer
jacket layer underneath a coil, and two layers outside the coil; in
this instance the coil may be floating or constrained in the jacket
material;
[0050] FIG. 21 shows, in order to achieve a controlled change in
stiffness of the distal tip, multiple layers being overlapped to
achieve a precise level of stiffness; in this instance the coil may
be floating or constrained in the jacket material;
[0051] FIG. 22 is a plot showing results of 3-point bend tests to
evaluate stiffness;
[0052] FIG. 23 shows the distal-most end of the distal portion
finished by inverting an inner liner over the helical support to
form a continuous element; in this instance the coil may be
floating or constrained in the jacket material;
[0053] FIG. 24 shows a distal portion in which softness is improved
by extending inner and outer tubular layers beyond the last coil of
the helical support; in this instance the coil may be floating or
constrained in the jacket material;
[0054] FIGS. 25A and 25B show further examples of catheter
arrangements in which an inner liner is inverted to return as a
continuous element; in this instance the coil may be floating or
constrained in the jacket material;
[0055] FIG. 26 shows in a catheter having a proximal end and an
intermediate portion an inner tubular layer of ePTFE material
extending along the entire length of the catheter including a
distal end, where it is bent back to be continuous;
[0056] FIG. 27 shows the inner tubular layer being of ePTFE in a
distal portion and of PTFE in a more proximal portion of the
catheter; a butt joint is used in which the proximal liner is
concentric within the distal liner;
[0057] FIG. 28 shows the proximal region of rib and recess
corrugation having an outer tubular layer comprised of a polymer
material and a distal liner transitioning to different material; a
lap joint is used in which the distal liner is concentric within
the proximal liner;
[0058] FIG. 29 shows that for a distance the ePTFE is concentric
within the PTFE;
[0059] FIG. 30 shows a further arrangement of a helical support in
the jacket in which the helical support is comprised of a tubular
layer of Nitinol or other material over a radiopaque material such
as Platinum; in this instance the coil may be floating or
embedded;
[0060] FIG. 31 shows catheters with radiopaque markers at various
positions along its length;
[0061] FIG. 32 is a series of diagrams showing a typical prior art
setup of a balloon guide catheter in a thrombectomy procedure to
provide proximal flow occlusion;
[0062] FIG. 33 shows a balloon catheter with an enhanced
flexibility section on the distal tip, and
[0063] FIG. 34 is a diagram showing layers and lumens of a dual
lumen balloon of the catheter of FIG. 33;
[0064] FIGS. 35 and 36 show corrugated tube tips for enhanced
flexibility;
[0065] FIG. 37 left image shows an Angiogram demonstrating the
external carotid, common carotid and internal carotid artery (ICA),
including the C1 and C2 segments, and right image shows acceptable
positioning of the balloon;
[0066] FIG. 38 shows the proximal and distal shaft having the same
outer diameter, and the proximal shaft having two concentric
lumens, in which the central lumen diameter is less than that of
the flexible distal tip;
[0067] FIG. 39 shows a catheter with a balloon and a distal portion
having a smaller outer diameter than the proximal portion;
[0068] FIG. 40 shows a catheter with a non-corrugated proximal
region of the distal section;
[0069] FIG. 41 shows a catheter device with a radiopaque marker at
the distal end of the flexible distal tip;
[0070] FIG. 42 shows a mother and daughter catheter arrangement
wherein the larger catheter is used to occlude inflow to the target
vessel, while the smaller catheter is used to retrieve the
clot;
[0071] FIG. 43, left diagram, shows the use of a small catheter
unable to reach a distal target vessel (right) during delivery of a
drug or embolic and the resulting undesired delivery to a
non-target vessel (top left vessel); and the right hand diagram
shows a method wherein a highly flexible large diameter catheter is
chosen to effectively occlude the target vessel, and can be placed
beyond the non-target vessel, so delivery of the embolic only
occurs to the target vessel; it is preferable that the catheter is
wedged in the target vessel;
[0072] FIGS. 44(a) to 44(e) are schematic diagrams outlining
relationship between pressure in the catheter lumen, and the clot
behaviour, during aspiration;
[0073] FIG. 45 shows a setup used for aspiration of a clot or other
material from the body using a pump;
[0074] FIG. 46 is a flow diagram showing steps including pressure
monitoring to establish whether the pump should apply vacuum or
pressurize during the aspiration procedure;
[0075] FIGS. 47(a) to 47(n) are diagrams illustrating operation of
the clot removal device in various examples;
[0076] FIGS. 48(a) to 48(c) show varying pressure signals between
two vacuum levels;
[0077] FIG. 49 is a flow diagram showing method steps for positive
oscillation or shake signals;
[0078] FIGS. 50(a) and 50(b) are plots showing shake signals;
[0079] FIGS. 51(a) and 51(b) are a flow diagram and an associated
plot for vacuum and positive oscillation;
[0080] FIGS. 52(a) and 52(b) are a flow diagram and an associated
plot for positive and negative modulation of aspiration; and
[0081] FIGS. 53(a) and 53(b) are images of a pump and its
components, including a housing, a connecting tube, an on-off
switch, a battery pack, a pulsatile pump, and a motherboard, in
which the pressure sensor is connected to the tube (or "lumen"),
which is connected to the catheter, thereby enabling pressure
measurement within the catheter.
DESCRIPTION OF THE EMBODIMENTS
[0082] Various embodiments are depicted in the accompanying
drawings for illustrative purposes, and should in no way be
interpreted as limiting the scope of the embodiments. Furthermore,
various features of different disclosed embodiments can be combined
to form additional embodiments, which are part of this
disclosure.
Terminology
[0083] "Jacket" is the wall of the catheter, and these terms are
interchangeable. It may be corrugated in all or some regions along
the length (longitudinal direction). It may include any or all of a
helical support (or "coil") surrounded by jacket material, and an
inner liner. The inner liner, where present, defines the lumen, but
otherwise the other jacket material defines the lumen. A liner
where present, may be terminated at some location in the
catheter.
[0084] "Tubular layer" is a layer of material of the jacket.
[0085] "Pushability" is understood as the transfer of force and/or
displacement applied at a proximal portion of a catheter, along a
length of the catheter, to a more distal portion of the catheter.
The higher the flexural stiffness the greater the pushability.
[0086] "Corrugate" is a rib and recess geometry on the outer
surface of the catheter, most often in a spiral pattern.
[0087] "Distal" means further from a clinician in use, closer to a
catheter tip in the longitudinal direction, and "proximal" means
closer to the clinician.
Description of the Embodiments
[0088] FIG. 1 illustrates an embodiment of a highly flexible, kink
resistant catheter 1. The catheter 1 includes a distal portion 3, a
proximal portion 2, a central lumen 5 and a reinforcing structure
such as a helical support 6 that runs the length of the catheter.
The proximal portion and/or a transition between the distal portion
and the proximal portion can in various embodiments include any of
the corresponding features of the catheters described in U.S.
application Ser. No. 15/647,763, filed Jul. 12, 2017, titled "HIGH
FLEXIBILITY, KINK RESISTANT CATHETER SHAFT," which is attached in
the Appendix. The inner tubular layer and/or the outer tubular
layer can include PTFE, ePTFE, electrospun PTFE, silicone, latex,
TecoThane, nylon, PET, Carbothane (Bionate), SIBS, Tecoflex,
Pellethane, PGLA, or Kynar, Polyethylene and cyclic olefin
copolymers, PEEK.
[0089] The inner and outer tubular layers (FIG. 1) in at least the
distal portion can be formed from a single section of material or a
number different sections of similar or different material. In this
embodiment the outer tubular layer 11 of the distal portion is
formed from a polyurethane (e.g. Pellethane 80AE) and the inner
tubular layer 5 is formed from ePTFE and/or PTFE.
[0090] In this case the catheter jacket comprises an inner liner 5
and an outer tubular later 11 with a helical support 6. The highly
flexible distal portion 3 (left side) of the catheter is created by
forming corrugations 15 into the outer surface of the outer tubular
layer 11. The helical support 6 is encapsulated between the
corrugations of the outer tubular layer 11 and the outside of the
smooth inner tubular layer 5 as shown in FIG. 1. The formation of a
corrugated wall structure during bending provides flexibility while
reducing the likelihood of kinking. The corrugated outer surface
can also decrease resistance when the outer surface of the catheter
contacts a vessel wall. The depth of the corrugations may be
tailored to provide a desired variation in stiffness along the
length of the catheter as shown in FIG. 2.
[0091] As shown in FIG. 1 a parameter "D" is depth of a corrugation
and a parameter "W" is the width of a corrugation. The width is not
the distance from peak to peak, rather it is the effective width of
the valley. In effect for many embodiments this is provided during
manufacture by tightening a cinch wire around a tubular layer, heat
treating, and removing the cinch wire to provide the corrugated
surface. The width W it approximately the diameter of the cinch
wire in this case. The depth D is not necessarily uniform because
the pressure applied by the cinch wire may vary along the length of
the catheter thereby forming deeper indentations in some locations
than in others.
[0092] FIG. 2 shows a cross section through a wall of a catheter
tip 50, having an inner layer 51, a helical coil support structure
52, an outer layer 53 with a corrugated surface 53. The depth A of
the corrugations on the left hand side is greater than the depth B
on the right hand side. The section with the lower corrugation
depth B may function as a transition region before a tip (left hand
side) with more flexibility.
[0093] In the examples of FIGS. 1 and 3 the coil is embedded in the
jacket; being constrained from movement relative to the surrounding
jacket material.
[0094] Additionally, pitch, or corrugation width variations may be
used to control the flexibility locally in the corrugated region.
Also, flexibility may be set during manufacture by choosing some
length of the coil to be embedded in the jacket or to be floating,
the region with the floating coil being more flexible. Where the
coil is floating it is in the context of the jacket tubular layers
being attached in the spaces between corrugation rubs, such as a
jacket tubular layer to an inner liner.
[0095] The outer tubular layer can extend at least a length of the
highly flexible distal portion or extend beyond the distal portion
for some distance along the proximal (midsection) length or extend
the entire length of the catheter as shown in FIGS. 3 and 4 (which
shows the catheter of FIG. 1 in its full length). Extending the
outer tubular layer at least some length beyond the highly flexible
distal portion of the catheter allows for a controlled stiffness
transition between the distal and proximal portions of the catheter
and for the formation of a robust joint between the outer tubular
layer and any additional outer jacket materials. Again, flexibility
may be set during manufacture by choosing some length of the coil
to be embedded in the jacket or to be floating, as is the case for
any of the embodiments described with reference to FIG. 3 or 4.
[0096] To form the corrugations in a tubular membrane, the membrane
can first be positioned over the helical reinforcing structure. On
the application of heat, the outer tubular membrane will reflow
such that it forms around the helical structure. A tensioned wire
can then be wound around the outside of the tubular membrane such
that it forces portions of the membrane into the grooves between
each loop of the supporting helical structure. The tubular membrane
can then be heat set to fix the corrugations in place. After this
process the tensioned wire may be unwound leaving eh corrugations
behind.
[0097] The inner tubular layer can extend into the proximal portion
of the catheter to provide an uninterrupted lumen and to join or
improve the joint strength between the highly flexible distal
portion of the catheter and the proximal portion of the catheter.
The diameter of the inner tubular layer can be constant (e.g.
smooth surface). The inner tubular layer may form at least part of
or the entirety of the liner as shown in FIG. 4. The inner tubular
layer can be made from a low friction material such as ePTFE or
PTFE.
[0098] As explained above, the outer tubular layer of at least the
distal portion is formed from a polyurethane (e.g. Pellethane 80AE)
and the inner tubular layer is formed from an ePTFE and/or PTFE
liner. It is necessary to attach these layers together and this is
not easily achieved as fluoropolymers do not form strong bonds with
other materials.
[0099] To facilitate bonding between fluoropolymers (e.g. ePTFE and
PTFE) and between fluoropolymers and other polymers such as
polyurethanes (e.g. Pellethane) the outer or bonding surface of the
fluoropolymer(s) may be chemically treated using a sodium-based
etching solution such as FluoroEtch. The etching solution removes
fluorine atoms from the surface of the fluoropolymer and prepares
it for bonding.
[0100] The etched fluoropolymer can then be coated with a thin
layer of urethane, such as ChronoFlex. On the application of heat,
this thin ChronoFlex layer flows and acts to tie the fluoropolymer
to a second etched fluoropolymer layer or to a different polymer
layer as shown in FIG. 5. This embeds the coil.
[0101] This diagram shows part of the cross-section of a catheter
at its distal portion 150. This includes a liner 151 of ePTFE or
PTFE, a tie layer 152 of urethane or FEP tape or FEP powder. Also,
there is a Nitinol.TM. coil 153 in an outer jacket 154 of ePTFE, or
urethane material. The nitinol coil 153 is encapsulated between the
outer tubular corrugated layer and the smooth inner tubular layer
151. The tie layer 151 serves the purpose of attaching the liner
151 to the outer jacket material. If the liner is of ePTFE material
then it will need to be etched to strip the fluorine atoms so that
it will form a better bond with the tie layer.
[0102] Again, flexibility may be set during manufacture by choosing
some length of the coil to be embedded in the jacket or to be
floating, as is the case for any of the embodiments described below
with reference to FIGS. 6 and 7.
[0103] The ChronoFlex.TM. tie-layer 152 is so thin it does not
cause any significant change in wall thickness. An alternative form
of tie-layer involves the use of FEP. The fluoropolymer may be
sputter coated with a FEP powder which under heat and pressure
forms a bond between the coated fluoropolymer layer and a second
layer. An ultra-thin FEP tape may also be used in the same
application.
[0104] The helical support is encapsulated between the corrugations
of the outer tubular layer and the smooth inner tubular layer as
shown in FIG. 5. The inner tubular layer and the outer tubular
layer are bonded together in the space between the adjacent loops
of the helical support by such mechanisms as a tie-layer. The
helical support is bonded within the helical channel formed by the
corrugated outer tubular layer, i.e., the helical support is
molecularly or physically attached to the outer tubular layer. The
helical support may also be bonded to the outside surface of the
smooth inner tubular layer. The distal portion of the catheter
retains highly flexibility and kink resistance because of the
advantages inherent in a corrugated outer structure and using
materials of appropriate stiffness and thickness.
[0105] In the present configuration, the pitch of the helical
support may vary over the length of the catheter to influence the
flexural stiffness of the catheter. For example, the helical
support could have a different pitch at the proximal loops compared
to the distal loops.
[0106] If the outer tubular layer of the distal portion of the
catheter is formed from a fluoropolymer such as ePTFE or PTFE and
the outer tubular layer of the proximal portion is formed from a
different polymer then achieving a good bond, especially one that
resists delamination during tracking, can be difficult. This may be
overcome by sandwiching the outer layer of the proximal portion of
the catheter between the inner and outer tubular layers of the
distal portion of the catheter as shown in FIG. 6.
[0107] FIG. 6 shows a portion 200 of a catheter, having an inner
lumen 201 with a liner, an outer layer 203 of Pellethane 80AE
material, and Nitinol coils 206. On the right hand sider the
catheter has a smooth outer surface 203, and distally in a
transition section there are corrugations 204 with a small depth,
and more distally deeper corrugations 205 for more flexibility. The
arrangement of having a transition section between proximal and
distal sections may be referred to as a "sandwich arrangement".
[0108] If the inner tubular layer of the distal portion of the
catheter is formed from a different material or different section
of material from that of the inner tubular layer of the proximal
portion then the tubular layers can be joined by creating a small
slit or window in one tubular layer and pulling a spliced length of
the other tubular layer through it as shown in FIG. 7. The helical
support is then wound around the outside of these layers thus
keeping them together.
[0109] FIG. 7 shows a catheter section 250 with a proximal end 251,
a transition section 252, and a distal tip 253, and a spliced
proximal layer 260 with a window 261.
[0110] In various embodiments the helical support is physically
attached by being constrained or embedded in the catheter wall to
move with its surrounding wall material. Such embedding might be
achieved at an interface between the coil and solely the jacket
material, or combination of an interface of the jacket material and
the inner liner.
[0111] The embedding can be achieved by a very tight fit between
the coil and the surrounding material. Generally, there is no gap
between the surrounding wall material and the coil. Due to the
three-dimensional geometry of the coil, when within a surrounding
material, it is unable to move independently.
[0112] Due to the manufacturing technique in which the material may
be moulded around the coil, there is no play between the coil and
jacket, meaning it cannot move independently. That is to say, the
coil is immovable without concurrent movement or deformation the
surrounding jacket material.
[0113] This lack of play, and tightness of fit means there is an
interfacial friction between the coil and surrounding material,
further providing constraint, and meaning the coil and surrounding
material must move together.
[0114] In other embodiments, the coil may be floating, that is to
say there is not a tight fit between the material in the jacket and
the helical coil. In these instances, there is some play between
the helical support and the jacket. This is particularly the case
where the jacket material surrounding the helical support is
comprised of ePTFE. In this instance, even in the presence of a
relatively tight geometric fit, the material is quite supple and
may allow movement of the helical support relative to the
ePTFE.
[0115] In general, the following are some preferred parameter
ranges for aspects of the catheter.
[0116] For at least some of the length of the catheter the width of
the corrugate is no more than 50% of the pitch of the
corrugate.
[0117] For at least some of the length of the catheter the width of
the corrugate is between 5% and 49% of the pitch of the corrugate,
and more preferably the width of the corrugate is between 15% and
45% of the pitch of the corrugate.
[0118] For at least some of the length of the catheter the width of
the corrugate is between 20% and 45% of the pitch of corrugate.
[0119] For at least some of the length of the catheter the width of
the corrugate is at least 10% of the jacket thickness.
[0120] For at least some of the length of the catheter the width of
the corrugate is at least 20% of the jacket thickness.
[0121] At the most distal region of the distal portion the width of
the corrugate it at least 60% of the jacket thickness.
[0122] At the most distal region of the distal portion the width of
the corrugate it at least 60% of the wall thickness and the depth
of the corrugate is at least 70% of the wall thickness.
[0123] The ratio of the width of the corrugate to the depth of the
corrugate is at least 0.5 in at least one region of the
catheter
[0124] In the embodiments described below the coil may be either
embedded or floating in some or all regions of the catheter, unless
stated otherwise.
[0125] Referring again to the construction of the catheter
structure, we achieve a catheter with a highly flexible distal tip,
to ensure that a smooth transition in flexural stiffness and
pushability is achieved between the flexible distal portion and the
proximal portion of the catheter, which may be of more conventional
construction. A smooth transition prevents areas of stress and
strain concentration within the catheter shaft. Such areas have
potential for kinking of the catheter, delamination of layers of
material, and/or of damage to key bonds within the catheter.
[0126] Bench testing demonstrates the large difference between the
stiffness of a conventional catheter tip design and a highly
flexible corrugated design. Smoothly bridging of this gap presents
a technical challenge.
[0127] FIG. 8 shows force measured at a 1 mm displacement in a
3-point bend test of a conventional catheter design (0.80 A
urethane jacket over a 0.005 in NiTi coil 0.018 in (0.45 mm) pitch
over on a 0.001 in (0.025 mm) PTFE Liner), and highly flexible
corrugated ePTFE design (inner and outer 0.002 in (0.05 mm) wall
ePTFE 0.9 g/cm.sup.3 density, with a 0.005 in (0.125 mm) NiTi coil,
0.018 in (0.45 mm) pitch.
[0128] It should be appreciated that while very good catheter shaft
flexibility allows the catheter to navigate extremely tortuous
bends at low force and reduced potential for vessel damage, it can
also lead to some compromise in pushability. For clarity,
pushability is understood as the transfer of force and/or
displacement applied at a proximal portion of a catheter, across a
length of the catheter, to a more distal portion.
[0129] Catheter flexibility may limit the transfer of a
displacement applied at a proximal portion of the catheter to a
distal portion of the catheter. This implies a portion of the
displacement is absorbed through global deformation of the catheter
as shown in FIG. 9. FIG. 9 shows behaviour of a conventional
catheter under compression when pushed against restriction. In this
instance the length of the catheter 600 has not changed. In
general, it is this type of shortening which occurs in catheters of
conventional construction.
[0130] FIG. 10 shows behaviour of a corrugated catheter 650 under
compression when pushed against restriction. In the case of a
corrugated outer jacket with a thin inner and outer tubular layer,
the deformation may be accommodated by the catheter wall. The inner
and or outer tubular layers of the catheter can deform locally,
particularly in the recess meaning the overall length is reduced.
Some of the global deformation of the catheter as shown in FIG. 9
would also be expected.
[0131] This soft compressive behaviour is advantageous at the
distal tip as the catheter tip is limited in its ability to move
forward causing vessel damage or dissection. However, in cases in
which the distal tip is very long, some increased pushability in
the proximal portion of the tip may be preferable to allow the
physician to navigate the catheter distally and proximally as
intended.
[0132] In one configuration one or more regions of varying
pushability and flexibility are present within the catheter tip
comprised of one or more of the regions of a rib and recess
construction. FIG. 11 shows in a catheter 700 use of progressively
more flexible or less pushable sections of catheter wall 701 within
the distal tip, distally of a proximal portion 702. In one
configuration the most flexible region is on the distal tip of the
catheter.
[0133] These regions of increased/decreased pushability/flexural
stiffness are achieved by a number of features such as embedding of
the helical support, alterations to the inner and outer tubular
layers (wherein the helical support may or may not be floating
between the inner and outer tubular layers), or the use of an
in-fill material.
[0134] The change in the stiffness or pushability via the
transition region may be gradual change or via multiple steps.
Where it is stepped or gradually changed it may be achieved by
having a particular tubular layer terminated, or by a change to the
degree of corrugation or a change in material.
[0135] It is envisaged that any or all of these approaches may
combined on some or all of the catheter shaft. Examples are as
follows: [0136] A distal tip in which at least some is of
corrugated material which embeds a helical support, wherein the
degree of corrugation is altered progressively proximally to
achieve in increase in stiffness. The most distal region may or may
not have a liner. The liner is ePTFE, transitioning to PTFE in a
more proximal region. The most proximal portion may not be
corrugated. [0137] A distal tip in which at least some is comprised
of a floating coil between ePTFE layers with a corrugated design,
wherein the thickness of the ePTFE material increases
progressively, or in steps proximally. This may be achieved by
increasing the wall layer thickness, or by the addition of layers
material. The ePTFE liner transitions to PTFE in a more proximal
region. The most proximal portion may not be corrugated. [0138] A
distal region may be comprised of a floating coil between ePTFE
layers of corrugate design and more proximally a corrugated
embedded portion, and more proximally again of an un-corrugated
portion. The ePTFE liner transitions to PTFE in a more proximal
region. A distal corrugated region may be combined with a more
proximal corrugated region with increasing wall thickness, or the
addition of a layer of material to the wall to increase stiffness.
The most proximal portion may not be corrugated.
[0139] In one configuration the helical support is embedded by
being bonded to the outer jacket, of for example ePTFE material.
This has the effect of stiffening the catheter wall construction,
when compared to a floating helical support, thus reducing the
flexibility and increasing the pushability.
[0140] In one configuration, in a catheter portion 750 the helical
support 752 is embedded in a matrix 753 of continuous porous
flexible material such as ePTFE. The outer wall has corrugated
surface, as shown in FIG. 12. An inner tubular layer, or liner 751,
as shown in FIG. 12, may not be required.
[0141] While ePTFE provides a very soft flexible material in the
catheter construction it is also compressible due to its porosity.
Furthermore, when used as a thin tubular layer which deforms easily
locally, macro pushability can be compromised if an area of the
catheter becomes impeded particularly if the distal tip meets a
resistance. To improve pushability while maintaining high
flexibility, an incompressible flexible material may be used for
embedding instead of a porous material such as ePTFE. This means it
can accommodate deformation more readily than materials which are
not porous.
[0142] The corrugations allow localised deformation, while a region
of continuous incompressible material ensures the efficient
transfer of axial force and displacement along the length of the
catheter. By reducing the depth of the corrugations, and
correspondingly increasing the thickness of the continuous
material, the pushability of the catheter can be increased, while
the flexibility is reduced. This may be described as a corrugated
jacket design.
[0143] In one embodiment the inner tubular layer is comprised of
ePTFE. In one configuration the helical support is transposed from
the inner liner such that it is not exposed to the liner. This is
to prevent movement or debonding of the helical support, and to
prevent it placing local stress or strain on the liner of the
catheter. The corrugation geometry may be of semi-circular,
U-shaped groove, V-shaped, or square groove.
[0144] In one configuration the width of the corrugate at the
surface of the catheter is at least 5% of the wall thickness of the
wall. Preferably, in at least one section the width of the
corrugate at the surface of the catheter is at least 10% of the
wall thickness at the wall. Preferably, in at least one region of
the distal tip, the width of the corrugate at the surface of the
catheter is at least 30% of the wall thickness at the wall.
[0145] In one embodiment the corrugate depth is between 5% and 95%
of the catheter wall thickness. In one configuration the corrugate
depth is at least 20% of the catheter wall thickness in at least
one section of the catheter.
[0146] In one embodiment, the corrugate depth varies along the
corrugated region of the catheter from a larger depth distally to
smaller depth proximally. In one embodiment, the corrugate width
varies along the corrugated region of the catheter from a larger
depth distally to smaller depth proximally. In another embodiment,
the corrugate depth varies from a larger depth distally to smaller
depth proximally, while the width is substantially constant along
the length of the corrugated section of the catheter.
[0147] In one embodiment the corrugate represents the impression of
a circular helical wire wound from a depth and width of no
impression, i.e. no corrugate, to a depth of at least 50% of the
wall thickness. It should be appreciated in that instance that the
width of the corrugate is varying from 0 to a maximum width
equivalent to the diameter of the helical wire, or impression which
remains following removal of the helical wire.
[0148] It should be appreciated that a tensile force on the wound
cinch helical wire is required to create the corrugations. For
example, a 0.005 in 304 Stainless Steel circular cross section wire
at 1N tension wound at a force 1N, on an 0.006 in wall thickness 80
A jacket with an ID of 0.088 in will achieve a 10-20% depth of
corrugation. Increasing the tension to 1N tension wound at a force
7N will achieve a 40-70% depth of corrugation. Varying levels of
force will induce different degrees of corrugation. It should be
appreciated that corrugations of high depth D as shown in FIG. 1
will allow the catheter section to flex at a relatively low force.
This is because the global bending of the catheter is actually
concentrated within the recess of the corrugate.
[0149] However, if the corrugation has a very low width, even very
deep and numerous corrugations will have a limit to the degree of
bending the catheter can accommodate. This is because adjacent
corrugations will start to touch one another. Therefore, the
flexural stiffness will be low until the adjacent corrugations
contact one another, or "bottom-out", at which point the flexure
stiffness will increase. Bending will then be accommodated by
deformation of the rest of the catheter wall (and no longer
primarily within the recesses) This bottoming-out means the
catheter shaft has a lower limit of bend-radius which it can
achieve via deformation within the recess. Further bending
deformation beyond the bottoming-out limit is achievable but is not
accommodated by deformation at the recess of the corrugation; it is
accommodated by pressing adjacent corrugations against one another.
This is generally at a very high force compared to the deformation
which occurs at lower bend radii while the deformation is focused
in the recess.
[0150] The width of the corrugate should be controlled so as to be
large enough to accommodate sufficient deformation within the
recess to reach the desired lower limit of bend-radius at
relatively low force of bending. This is important as physicians
generally wish to be able to navigate catheters at low forces so
that the potential for vessel damage is reduced, and the catheters
are not deforming the vessels in order to travel forward.
[0151] While the width and depth of the corrugation contribute to
the flexural stiffness of the catheter, the width can dominate the
lower limit of bend-radius to which the catheter can deform.
Accordingly a larger corrugate width enables a lower bend radius at
a low force of bending.
[0152] Consider the example of an 0.088 in ID (2.2 mm/catheter with
a wall thickness of 0.006 i.eta. (0.15 mm) with an 0.005 in (0.125
mm) diameter Nitinol helical support of 0.018 in pitch embedded in
80 A, over an ePTFE Liner. A sample with a 0.004 in (0.1 mm)
corrugate width and 0.006 in corrugate depth will yield a force in
3 pt bending of 0.05N at 1 mm deflection, and a bottom out bend
radius of 5 mm. A sample with a 0.007 in (0.175) corrugate width
and 0.006 in corrugate depth will yield a similar force in 3 pt
bending but bottom out bend radius of 3.5 mm.
[0153] In order to allow a large catheter to enter the cerebral
vessels safely, and to accommodate lower radii bends such as those
of the carotid siphon, the width of the corrugate should be of a
minimum value relative to the pitch and or wall thickness.
[0154] In one embodiment the width of the corrugate is no more than
50% of the pitch of the corrugate (same as the pitch of the helical
support). Preferably the width of the corrugate is between 5% and
49% of the pitch of the corrugate. More preferably the width of the
corrugate is between 15% and 45% of the corrugate. More preferably
the width of the corrugate is between 20% and 45% of the
corrugate.
[0155] In one embodiment the width of the corrugate is at least 10%
of the wall thickness. Preferably the width of the corrugate is at
least 20% of the wall thickness. In one embodiment at the most
distal section of the tip the width of the corrugate it at least
60% of the wall thickness.
[0156] In one embodiment at the most distal section of the tip the
width of the corrugate it at least 60% of the wall thickness and
the depth of the corrugate is at least 70% of the wall
thickness.
[0157] In another embodiment the corrugate represents the
impression of a circular helical wire wound from a depth and width
of no impression, i.e. no corrugate, to a depth of at least 70% of
the wall thickness.
[0158] In one configuration, the inner tubular layer (liner)
terminates in a region proximal to the distal end of the catheter.
This will further reduce the stiffness of the catheter for a
corrugated or uncorrugated configuration. In this instance,
particularly in the case wherein the catheter wall is comprised of
a material such as a silicone, urethane or pebax, the region
without a liner may be tacky. In one embodiment the region of inner
lumen of the catheter without a liner has hydrophilic or
hydrophobic coating to improve lubricity. This is shown in FIG. 13
for a catheter portion 760 having a helical support 761 embedded in
an outer jacket 762, and in which an inner liner 763 extends for
part of this length but terminates before the distal end (left
side).
[0159] In one embodiment the un-lined section is at least lcm in
length, preferably at least 2 cm in length. The termination of the
liner is advantageous in allowing a more flexible section of the
catheter. However, this can also form a sudden change in flexural
stiffness and potential location for kinking or high stress or
strain. This may be managed using a change in corrugation
parameters, or by skiving the liner. In another embodiment, the
termination of the liner is a skive, or angular cut.
[0160] In one configuration a section of the un-lined jacket
material adjacent to the liner proximally is less corrugated than
the section of unlined jacket distally and proximally. This may be
achieved by decreasing the depth of the corrugation. In another
configuration a corrugated section of the lined jacket adjacent to
the unlined jacket has a longer pitch than the section of unlined
jacket distally and proximally.
[0161] In one configuration the helical support is transposed from
the inner liner such that it is not exposed to the inner lumen of
the catheter as shown in FIG. 14, having a helical support 771 in
an outer jacket 772. This is to prevent pop-out the helical support
into the catheter lumen during bend of the catheter. In one
embodiment the distance from the inner lumen to the helical support
is at least 0.005 mm.
[0162] Referring to FIG. 15, in a catheter portion 780 there is a
helical support 781, and an outer jacket 782 and an inner liner
783. The outer jacket 783 has a proximal part 784 without
corrugations, distal part 785 with corrugations. The inner liner
783 terminates proximally of the distal end at 786. This is an
example of a configuration n which the most distal section of the
distal tip is comprised of a corrugated jacket without a liner, a
more proximal section is corrugated and contains a liner, at least
one section even more proximally is more corrugated, and at least
one section even more proximally again is un-corrugated. In one
embodiment all sections of the jacket are of the same material
durometer. In one embodiment the material is urethane of durometer
80 A. In another embodiment more proximal jackets are of a stiffer
urethane or pebax are present. The liner is comprised of ePTFE. In
a more proximal section of the shaft, the liner may transition to
PTFE. In one embodiment this transition takes place in a more stiff
durometer material than that of the jacket of the corrugated distal
tip.
[0163] In one embodiment, a catheter portion 800 has a liner 751, a
helical support 752, and an outer jacket 753 as for the catheter
portion 750. However, in this case there is an outer tubular layer
801 added to the outside of the corrugated structure which embeds
the helical support to further increase the stiffness of a section
of the catheter proximally of the distal end, as shown in FIG. 16.
This layer may be of the same or different material as the material
used to encapsulate the helical support. Materials of higher
stiffness such as PET or Nylon pr PEEK or other polymer can be used
in this instance without significantly adding to the profile. In
one embodiment a layer of PET is added which has a thickness of
0.05 mm or less, preferably 0.025 or less, and more preferably
0.0125 mm or less.
[0164] In order to manufacture a corrugated polymer jacketed
catheter section a number of approaches may be taken. The following
steps may be used as shown in FIG. 17: [0165] A conventional
catheter construction containing a coil 752 embedded within a
polymer jacket 753 is bonded to a PTFE liner 751 is built to form a
base assembly. [0166] An outer liner 811 which will not bond to the
polymer jacket is then placed over the jacketed coil. Fluoro
polymers of high flexibility such as FEP or PTFE or more preferably
ePTFE may be used. [0167] A wire 810 is wound in a helix onto the
outside of the outer liner under tension imparting a corrugate
geometry on the construction. This may be termed a "cinch wire"
[0168] The construction is heated to reflow or anneal the material,
setting it into the corrugate geometry [0169] The assembly is
cooled [0170] The cinch wire 810 is removed [0171] The outer liner
811 is peeled off the assembly to complete the process.
[0172] An in-fill material may also be used to manage flexibility
and increase pushability, and where it is used it embeds the coil.
FIG. 18 shows a catheter portion 850 with a liner 851, a coil 852
and inner and outer tubular layers 853 and 854 respectively and
in-fill for increased stiffness
[0173] In one embodiment the material is used only to partially
fill the space around the helical support as shown in FIG. 18. In
another embodiment the in-fill material completely fills the
helical channel around the helical support between the inner and
outer tubular layers. In yet another embodiment the in-fill
material is melted to form a layer of material on all surfaces
within the helical channel.
[0174] In one embodiment the outer and inner tubular layer are
comprised of ePTFE or PTFE, and the in-fill material is PET, PEEK
or FEP
[0175] The helical channel may be formed using a helically wound
wire (cinch wire) placed temporarily on the outside of the outer
tubular layer. To permanently form the helical channel, the
construction may then be heated such that the in-fill layer melts
to flow between the helical support, the outer tubular layer, and
the inner tubular layer. Upon cooling and removal of the helically
wound cinch wire on the outer tubular layer, the corrugate
configuration is maintained, and an adhesive chemical bond is
achieved between the components via the in-fill material.
[0176] In one configuration the in-fill material may be a
polyurethane, pebax, PET, silicone, latex, TecoThane, Nylon, PET,
Carbothane, SIBS, Tecoflex, Pellethane, PGLA or Kynar, Polyethylene
and cyclic olefin copolymers, PEEK.
[0177] In one configuration the inner tubular layer and outer
tubular layer of ePTFE are bonded to one another via sintering. It
must be appreciated that in the case of a fluoropolymer, and in
particular ePTFE or PTFE for use as the inner and outer tubular
layers, the temperature required for the sintering can exceed
500.degree. C. In this instance it may be preferable to use
materials for in-fill with a high processing and degradation
temperatures such as PET, FEP, or PEEK. Other materials such as
urethane or pebax will degrade at lower temperature and are not
suitable.
[0178] As PET is a relatively stiff material it can be introduced
in small volumes to stiffen the corrugate structure without
significant impact on catheter profile or completely filling of the
helical channel. This may provide regions of floating and of
embedded coil.
[0179] In one configuration an increase in the pushability or
stiffness is achieved by changing the thickness of one or both of
the tubular layers. An increase in thickness increases the
intrinsic stiffness of the wall. It also means a reduction in the
available space for localised material bending and deformation.
Therefore, the flexibility may be reduced. Furthermore, as the
thickness increases the axial cross-sectional area along the axis
of transmission of force and displacement along the catheter
increases.
[0180] In one embodiment, both the inner and outer tubular layer
thickness are increased, as shown in FIG. 19 for the catheter
portion 950 as compared to the catheter portion 900. In the
catheter portion 900 there is an inner liner 901, a coil 902 and an
outer tubular layer 903. In the catheter portion 950 there is a
thicker inner liner 951, a coil 952, and a thicker outer tubular
layer 953. In another embodiment the inner tubular layer thickness
alone is increased. In yet another embodiment the outer tubular
layer thickness alone is increased.
[0181] In another configuration the total outer tubular wall
thickness may be altered by the addition of one or more layers of
the same material. Referring to FIG. 20 a catheter portion 1000 has
a liner 1001, an outer jacket layer 1002 underneath a coil 1005,
and two layers 1003 and 1004 outside the coil 1005.
[0182] The total inner tubular layer wall thickness may be
increased by the addition of one or more layers. These layers may
be of the same or different materials. In the case of ePTFE, the
combined thickness of the inner tubular layers in an unconstrained
configuration may be between 0.025 mm to 0.3 mm, preferably between
0.05 mm and 0.2 mm.
[0183] In one configuration the inner and outer tubular layers are
comprised of multiple layers of ePTFE, wherein there is at least
one layer between an outer tubular layer and an inner tubular
layer. The total thickness of (for example, ePTFE) tubular layers
which are comprised of one or more layers may be between 0.025 mm
to 0.3 mm, preferably between 0.05 mm and 0.2 mm. The density of
the material (again, such as ePTFE) may be approximately 0.9
g/cm.sup.3. Increasing or decreasing the density of the material
will necessitate a bigger or smaller wall thickness to achieve the
same effect.
[0184] In another embodiment the inner tubular layer thickness is
constant along the length of the tip, but the outer tubular layer
thickness is larger in at least one region. In another embodiment
the outer tubular layer thickness is increased proximally at least
once along the length of the catheter tip.
[0185] In order to achieve a controlled change in stiffness of the
distal tip, multiple layers may be overlapped to achieve a precise
level of stiffness as shown in FIG. 21 in which an additional outer
layer 1010 is present for part of this catheter portion. This
principle may be used for any number of layers, to achieve a
desired variation in stiffness. Similarly, single thicker layers
may be used proximally, connected to a thinner layer more distally
to achieve the same effect.
[0186] In one embodiment the tip has one outer tubular layer of
0.025 mm to 0.075 mm across the length of the tip. A second
additional outer tubular layer of thickness 0.025 mm to 0.075 mm is
present in a region more proximally. A third additional outer
tubular layer of thickness 0.025 to 0.075 mm is present in a region
even more proximally. A fourth additional layer of thickness 0.025
to 0.075 mm is present in a region even more proximally.
[0187] In one embodiment the distal tip comprises an outer tubular
layer of 0.05 mm across the length of the tip. A second additional
outer tubular layer of thickness 0.05 mm is present in a region
more proximally. A third additional outer tubular layer of
thickness 0.05 mm is present in a region even more proximally. A
fourth additional layer of thickness 0.05 mm is present in a region
even more proximally.
[0188] In one configuration the tubular layers are bonded to one
another. The bond may be present across the entire interface of the
tubular layers. Alternatively, the bond may only be present at
recesses of the corrugations, in the area where the inner and outer
tubular layer are in contact. In yet another embodiment, the bond
is present between the layers at the rib and recess regions of the
corrugations. In another embodiment the material of the inner or
outer tubular layer may be changed to one with a higher stiffness
to increase the stiffness of the wall.
[0189] It should be noted that some variation in the thickness of
the tubular layers may be present locally following bonding of
inner and outer tubular layers, or their constituent layers, due to
the use of local compression (pressure) to ensure a strong bond
between tubular layers. This is particularly so with ePTFE because
it is a porous compressible material. This localised compression
may reduce the wall thickness in that area.
[0190] To evaluate a subset of the embodiments described above, 8F
catheter samples of inner diameter 0.088 in were built and tested
in a Three Point Bend Test. The force at a 1 mm displacement was
measured using a 50N Load Cell on a Zwick Roel tensile test
machine. The distance between the supports was 20 mm. Clear changes
in stiffness were achievable using the various configurations
outlined above.
[0191] It can be appreciated that the embodiments described above
can be used to alter the stiffness of the catheter wall as desired.
For comparison, a 6F Microvention Sofia Plus catheter indicated for
use in neurovasculature is included. FIG. 22 shows results of
3-point bend tests to evaluate stiffness of various embodiments
described above.
[0192] In the neurovasculature, when entering delicate vessels such
as M1, M2, ICA, vertebral and basilar arteries, an atraumatic tip
of critical importance. It is preferable that the distal tip has a
minimum length of its most flexible section such that the catheter
tip will deflect or absorb deformation rather than causing vessel
damage.
[0193] In one embodiment the distal and flexible sections of the
catheter of corrugate rib and recess design is a minimum of 1 cm in
length and is comprised of inner and outer tubular layers in a
corrugate configuration, with a floating helical support within a
helical channel. In one embodiment for an 8F catheter distal tip,
the force in 3-point bend test, for a span of 20 mm, at 1 mm
deflection, should not exceed 0.1N.
[0194] As shown in FIG. 23, in one configuration, the distal-most
end 1050 of the distal portion is finished by inverting an inner
tubular layer 1051 over the helical support to form a continuous
element.
[0195] Referring to FIG. 24, in another embodiment, in a distal end
1060 the softness of the distal tip end is improved by extending
inner and outer tubular layers 1061 and 1062 beyond the last coil
of the helical support.
[0196] As shown in FIG. 25A, in a distal portion 1070 an inner
tubular layer 1071 is inverted at the distal end 1072 to return as
a continuous element. Inner and outer tubular layer are comprised
of the same piece of material and are continuous. An extension of
ePTFE at the end 1072 of the corrugated section is present to
improve tip softness. Preferably, an extension beyond the last coil
is between 0.5 and 5.0 mm. More preferably the extension beyond the
last coil is between 1.0 and 0.3 mm. The distal portion 1070 also
has an outer tubular layer 1073 terminating before th distal end
1072, and a concentric further outer tubular layer 1074 around the
layer 1073 for part of the length of the layer 1073. This staggered
overlapping arrangement provides a transition portion with stepped
changes in flexural stiffness.
[0197] FIG. 25B shows a catheter distal portion 1080 with an inner
liner 1081 which extends out at the distal tip to form an
extension. In this case there are also overlapping staggered outer
tubular layers 1083 and 1084.
[0198] In the catheter 1070 two or more layers are achieved by
using the same piece of material inverted and returned along the
length or a portion of the catheter. In one instance two pieces of
ePTFE are used to achieve one inner tubular layer, and three outer
corrugated tubular layers.
[0199] In the catheter 1080 additional layers are added discretely.
In another embodiment, a combination of inverted continuous layers
and discrete layers is used. The proximal portion of the catheter
(shown un-corrugated) may be corrugated or un-corrugated.
[0200] PTFE material is a relatively stiff material compared to
eTPFE and so is therefore preferable to avoid the use of PTFE as an
inner tubular layer (liner) particularly in areas which will be
subject to significant bending during passage through tortuous
vessels. In one embodiment, as shown in FIG. 26, in a catheter 1100
having a proximal end 1101 and an intermediate portion 1102 an
inner tubular layer is of ePTFE material and this extends along the
entire length of the catheter including a distal end 1103, where it
is bent back to be continuous with the outer tubular layer.
[0201] In one configuration, the inner tubular layer is ePTFE in a
distal portion and PTFE in a more proximal portion of the catheter
as shown in FIG. 27 for a catheter 1150 having a proximal end 1151,
an intermediate portion 1152, a distal portion 1153. There is a
transition region 1154 in which the outer jacket a layer is merged
into and joined with an outer jacket of PTFE material in the
intermediate portion and the transition region. The transition from
ePTFE to PTFE may be achieved by a "butt" joint, in which the inner
tubular layers of PTFE and ePTFE are in contact without
overlap.
[0202] In another embodiment, a transition from inner tubular layer
of ePTFE to FTFE occurs in a region of the catheter which is not
subject to significant bending during use. In one configuration the
device dimensions are suitable for placement in the
neurovasculature, including M2, M1 and distal internal carotid
arteries. Preferably, the transition from ePTFE to PTFE occurs
proximal to the petrous segment of the ICA. In one configuration,
the transition from an ePTFE to PTFE inner tubular layer occurs
between 3 and 40 cm from the distal end of the catheter, preferably
between 5 and 30 cm from the distal end, and more preferably at
least 10 cm from the distal end.
[0203] In one configuration, the transition from inner tubular
layer of ePTFE to PTFE occurs in a region proximal to a region of
the catheter of rib and corrugation recess. In another
configuration the transition from inner tubular layer of ePTFE to
PTFE occurs proximal to the most flexible region of a rib and
recess corrugate design, but still within a region of stiffer rib
and recess corrugate design.
[0204] In one embodiment the proximal region of rib and recess
corrugate has an outer tubular layer comprised of a polymer
material, as shown in FIG. 28. In one configuration the polymer
material is a urethane or pebax. In one embodiment the polymer
material is 80 A urethane. FIG. 40 shows a catheter 1200 having a
proximal end 1201, an intermediate portion 1202, a distal portion
1203, and a transition region 1204. An ePTFE inner tubular layer
(liner) 1207 transitions to a PTFE jacket 1205 in the intermediate
portion within a corrugated section of the distal tip. A lap joint
is used in which the PTFE tubular layer 1208 is concentric within
the ePTFE tubular layer 1207.
[0205] In another embodiment the transition from ePTFE to PTFE may
be achieved via a "lap" joint wherein there is overlap of the
tubular layers of ePTFE and PTFE. In one configuration the overlap
between the PTFE and ePTFE is between 1 mm and 30 mm in length. The
use of an overlap increases the area of interface for bonding thus
improving the bond strength.
[0206] In one instance for a distance the ePTFE is concentric
within the PTFE, as shown in FIG. 29. In this diagram a catheter
1250 has a proximal end 1251, and intermediate portion 1252, and a
distal portion 1253. An inner liner 1260 is bent over at the distal
end to form part of the outer jacket of the distal portion 1253. At
a transition region between the intermediate portion 1252 and the
distal portion 1253 the inner liner 1260 is within a tube of PTFE
material 1261 with an overlap length of at least 2 mm, preferably
at least 5 mm. The tubular layer 1261 extends proximally within a
jacket material 1262 in the intermediate portion 1252. This
provides a configuration with an ePTFE inner tubular layer (liner)
transitions to PTFE within a corrugated section of the distal tip.
A lap joint is used in which the ePTFE tubular layer 1260 is
concentric within the ePTFE tubular layer. 1261
[0207] In one configuration, a maker comprised of a helical coil of
Platinum is present on the distal tip.
[0208] In one embodiment, the helical support may be comprised of a
radiopaque material such as Platinum wire. In another embodiment,
to leverage the super elastic properties of Nitinol with
radiopacity, the helical support may be comprised of drawn Nitinol
tubing filled (such as Nitinol #l DFT, Fort Wayne Metals) with
Platinum or other radiopaque material. This would allow the
physician to observe the distal tip behaviour under x-ray through
the procedure. In one embodiment the helical support tube is
comprised of at least 10% Platinum. FIG. 30 shows such an
arrangement in which a catheter portion 1280 has a radiopaque
helical coil 1281 around which there is a coating 1282, and there
is a tubular layer 1283 over the outer jacket.
[0209] In one configuration, the radiopacity of the distal tip is
further enhanced via a region in which the helical support pitch is
reduced such that an area of greater density of radiopacity is
achieved.
[0210] FIG. 31 shows catheters with radiopaque markers 1270 at
various positions along its length. Advantages and novel aspects
are that allow the physician to ensure that more stiff regions the
catheter are not placed in more delicate region of the vasculature.
For example, a proximal marker at the start of the flexible distal
tip can be used to define the region of the proximal catheter which
should not be placed beyond the cervical C1 segment of the internal
carotid artery. An intermediate marker can further be used to
differentiate the end of a region of intermediate flexibility which
should not be placed before, within, or beyond the cavernous
segment C4. The region between the intermediate marker and distal
marker establishes the region of highest flexibility which is
suitable for placement in the C4-C7 regions of the internal carotid
artery, and more distal vessels.
[0211] In one embodiment, in which the device is suitable for
placement in the neurovasculature, the distal flexible tip length
is at least 10 cm, and the un-lined distal section is at least 3 cm
in length. In another embodiment in which the device is suitable
for placement in the peripheral vasculature, the
Aspiration Device including the Catheter.
[0212] A catheter of any example may be used for example for
thrombectomy.
[0213] Recent clinical data has demonstrated that use of flow
arrest using a balloon guide catheter can improve outcomes during
thrombectomy procedures. This is done by: [0214] Reducing flow
towards the clot while the balloon is inflated proximal to the clot
in the ICA. Reducing the flow reduces the potential for distal
emboli to break off, or be carried distally, during the clot
retrieval using a stentriever or aspiration catheter. [0215]
Providing a lumen for aspiration as the clot enters the BGC after
it has been captured by a stentriever or aspiration catheter, and
is dragged from the target site.
[0216] The prior art setup of balloon guide catheter in a
thrombectomy procedure is shown schematically in FIG. 32, with a
balloon 1300 and a tip 1301. Balloon guide catheters for use in
thrombectomy procedures must facilitate the insertion of a
microcatheter, and distal access catheter. In order to do this, the
balloon guide must have an inner diameter in the range of 5F or
greater. Additionally, the catheter typically has an outer diameter
in the range of 8F or 9F.
[0217] Existing catheter technology, at the dimensions described
above, is extremely stiff. This is due to the catheter materials,
design and architecture used. Therefore, the distal tip of the
balloon guide catheter cannot be placed beyond the petrous segment.
Excessive stiffness means the catheter is not flexible enough to
track through the tortuosity of the distal ICA and other target
vessels where the clot may be located, and there is a high
potential for vessel damage or perforation.
[0218] Ideally, the tip of the balloon guide catheter should be as
close to the clot as possible. This reduces the distance over which
the clot must be dragged from the target vessel to the location of
the balloon guide catheter tip. It may also enable the physician to
directly aspirate the clot locally as the tip of the catheter can
now engage the clot.
[0219] In some scenarios, remote aspiration of the clot is being
performed using balloon guide catheters, while the balloon is
inflated. Remote aspiration is a procedure in which the clot is
aspirated without contact of the catheter tip with the clot. This
works particularly well in a closed system where alternative flow
pathways are not present. The success of this technique is often
limited by the fact that the tip of the catheter can be a long
distance from the clot.
[0220] A balloon catheter, whether used for PTA or embolic
protection, is typically of a dual lumen, double layer construction
along the length proximal to the balloon. This ensures there are
two lumens; one for the passage of guide wires, catheters, or
fluids, and one lumen for inflation. This dual layer construction
is not always as flexible as desired, and is prone to kinking.
[0221] There is therefore a need for a balloon guide catheter which
can provide flow arrest, but which also incorporates a very
flexible distal portion which can track through a tortuous vessel,
such as the distal ICA or as far as the M1 or other
vasculature.
[0222] In one embodiment a shaft or section with enhanced
flexibility compared to the proximal section is present distal to
the balloon of a balloon catheter. This flexible section enables
the tip of the balloon to be placed more distally in the
vasculature. This section of enhanced flexibility may be comprised
of the types described in U.S. application Ser. No. 15/647,763,
filed Jul. 12, 2017, titled "HIGH FLEXIBILITY, KINK RESISTANT
CATHETER SHAFT," and U.S. Provisional No. 62/599,560, filed Dec.
15, 2017, titled "HIGH FLEXIBILITY, KINK RESISTANT CATHETER SHAFT"
(both included in the Appendix), corrugate construction or other
design.
[0223] This device may be designed so that the distal tip is
flexible enough to reach and touch the clot for vacuum aspiration.
The part which is distal of the flow restrictor (such as the
balloon) includes the distal portion and preferably at least some
of the transition portion. There may also be some of the transition
portion proximally of the flow restrictor.
[0224] The length of this flexible section may vary such that it
can reach specific anatomical locations, such as the distal
internal carotid artery, terminus of the internal carotid artery,
proximal M1, distal M1, proximal M2, distal M2, basilar, or
vertebral vessels. This length may also help ensure that that while
the tip of the catheter can reach the target vessel, the balloon
does not pass the cavernous, or petrous segment of the ICA.
Inflation of the balloon beyond these segments can cause vessel
damage. The length of the flexible section may be between 1 cmn and
20 cm, preferably between 3 cm and 15 cm.
[0225] The outer diameter of this flexible tip may differ from the
outer diameter of the proximal section of the catheter. In one
embodiment the distal section has a larger diameter than the
proximal section. In yet another embodiment the outer diameter has
a diameter smaller than the diameter of the proximal section of the
catheter. Variations such as a taper in the diameter of the distal
section may also be used. Differing diameter distal sections can
help to ensure access to specific vessels beyond the area to land
the balloon.
[0226] FIG. 33 shows a device 350 with a flexible distal catheter
tip 1351 extending from a balloon 1352, and proximally of which
there is a catheter main section 1353 extending from a Y-piece
1354. FIG. 10 shows the balloon 352 inner layer inflation lumen
1360 and the balloon outer layer inflation lumen 1361.
[0227] In one configuration, the outer layer of balloon inflation
lumen may of enhanced flexibility while the inner layer of the
balloon inflation lumen may be of a conventional construction
comprising a single layer material, braided extrusion, coiled
extrusion or other construction. These layers are shown
schematically in FIG. 34, inner layer 1360 and outer layer 1361. In
this way the pushability of the catheter may be maintained by the
inner layer, while the outer layer mitigates compromise in terms of
flexibility. Furthermore this construction will help to prevent
kinking, since mechanics dictate that as the ratio of the inner
diameter to the outer diameter of a tube increases, kink resistance
is reduced. Use of the enhanced flexibility construction for the
outer layer, traditionally more prone to kinking will solve this
issue.
[0228] In another embodiment, a balloon catheter of dual layer
construction comprises both inner and outer layer of the balloon
inflation lumen of the enhanced flexibility construction. This will
represent an ultra-flexible and kink resistant balloon
catheter.
[0229] In other configurations, the proximal section may utilise
other constructions to inflate the balloon such as a single lumen
design with a vent hole and teak proof seal, a coaxial lumen or
other design.
[0230] It should be noted that a balloon guide catheter, with a
long distal tip capable of reaching a clot may be used as a
thrombectomy device as follows: [0231] Perform an angiogram to
determine location of occlusion, and distance between petrous or
cavernous carotid, and occlusion [0232] Choose a balloon catheter
with distal tip length suitable to reach the clot, while ensuring
the balloon inflation does not land beyond the petrous or cavernous
carotid [0233] Navigate the distal tip of the catheter to the clot.
[0234] Inflate the balloon such that flow arrest is enabled, and
alternative flow pathways which could reduce the effectiveness of
the aspiration are minimised [0235] Apply a vacuum to the inner
lumen of the catheter to aspirate the clot. [0236] If the clot is
retrieved, perform another angiogram through the balloon guide
catheter or a diagnostic catheter. [0237] Remove the balloon guide
catheter. [0238] Procedure is finished.
[0239] It may be noted that in the above method, the use of a large
diameter distal tip, close to that of the target vessel will
maximise the potential of complete clot ingestion.
[0240] In yet another embodiment, enhanced catheter shaft
flexibility and kink resistance may be achieved without additional
helical wire support, but instead using a simple tubular
construction with a corrugate architecture. The corrugations may be
defined as adjacent circular depressions in the wall thickness of
the tube, or as a continuous helical depression as shown in FIGS.
35 and 36 respectively. In these diagrams the tip has an outer
layer 1400 with corrugations 1401 (FIG. 35) and an outer layer 1450
with more shallow corrugations for desired flexibility.
[0241] The device may be designed so that the distal tip is
flexible enough to reach and touch a clot for vacuum aspiration.
The typical target vessels are the M1, M2, M3, distal ICA.
[0242] The distal tip should be long enough to reach the target
vessel, while also ensuring that the balloon does not pass the
petrous segment of the internal carotid artery (known as C2). This
is because the vessels and surrounding tissue beyond the petrous
segment are prone to damage which can have catastrophic
consequences.
[0243] It is preferable to ensure that the location of the balloon
when inflated is within C1 segment of the carotid artery. It is
also preferable that the balloon be distal to the external carotid
artery to ensure effect flow restriction and or flow reversal. The
length of the flexible section may be between lcm and 20 cm,
preferably between 3 cm and 20 cm.
[0244] FIG. 37 left image shows an Angiogram demonstrating the
external carotid, common carotid and internal carotid artery (ICA),
including the C1 and C2 segments, and right image shows acceptable
positioning of the balloon (2282, in a catheter 2280 proximal of a
distal end 2281. It should not be inflated past the C2 segment. The
distal tip length of the catheter should be long enough to reach
the clot while ensuring safe position within or proximal to the C2
segment of the ICA.
[0245] Any or all the embodiments described above to refine the
transition from the stiffness of the proximal portion of the distal
tip to the most distal portion may be used.
[0246] The proximal shaft must serve two functions and have at
least two lumens; one for balloon inflation and a main lumen for
delivery of fluids and devices, and for aspiration. The flexible
tip only requires one lumen, therefore has potential to have a
larger lumen than the proximal section. In one embodiment the inner
diameter of the flexible tip is the same inner diameter as the
proximal shaft.
[0247] In another embodiment the proximal and distal shaft have the
same outer diameter, and the proximal shaft has two concentric
lumens, in which the central lumen diameter is less than that of
the flexible distal tip as shown in FIG. 38. This drawing shows a
balloon guide catheter 2300 with a flexible corrugated distal tip
2302 and a balloon 2301. In this incidence the inner diameter of a
proximal shaft lumen 2303 is less than that of the flexible
corrugated distal tip 2302. The proximal and distal shafts have the
same outer diameter.
[0248] In another embodiment the inner diameter of the proximal
shaft is the same as that of the flexible distal tip. In yet
another embodiment, the outer diameter of the distal tip is smaller
than that of the proximal shaft. The distal tip inner diameter may
be the same as, or smaller than, the inner diameter of the proximal
shaft. FIG. 39 shows a catheter 1400 with a balloon 2401 and a
distal portion 2402 having a smaller outer diameter than the
proximal portion 2403.
[0249] In one configuration, the distal tip is comprised of a
flexible corrugate section distally, and a non-corrugated section
proximally. FIG. 40 shows a catheter 1500 with a non-corrugated
proximal region 2501 of the distal region 2502.
[0250] In one configuration, as shown in FIG. 41 for a catheter
device 2600 a radiopaque marker is present at the distal end of the
flexible distal tip. Markers are also present immediately distal
and or proximal to the balloon to define its location. An
additional intermediate distal marker may be present within he
distal tip to define a proximal region of increased stiffness
unsuitable for placement in distal to the C2 segment of the
ICA.
[0251] In one configuration, the balloon catheter is suitable for
use via direct carotid access. In this case a shorter proximal
shaft will improve ergonomics for the physician. In this instance
the length of the catheter shaft proximal to the balloon does not
exceed 40 cm, and preferably does not exceed 30 cm.
Flow Restriction Using Larger Bore Catheter Via Near Vessel
Occlusion or Wedging
[0252] The embodiments described above enable the physician to
place larger bore catheters more distally than has been possible
using conventional catheter technology. However, it may not be
possible to place a larger catheter in the target vessel due to the
vessel diameter being smaller than the catheter itself. In this
instance a larger catheter may be used to achieve flow
restriction.
[0253] In some instances, additional vessels are present which
perfuse the treatment area. For example, in the case of the
anterior cerebral artery, proximal occlusion using a balloon guide
catheter placed in the ICA does not prevent inflow to the target
treatment site. This is also a problem in posterior stroke where
there are two significant inflow vessels (left vertebral artery and
right vertebral artery), and the target treatment site is the
basilar artery or posterior communicating artery.
[0254] In one embodiment a system is comprised of a "mother" and
"daughter" catheter, in which significant flow restriction, or flow
arrest, may be achieved by placing or wedging a large bore highly
flexible mother catheter in a vessel location proximal to the
target treatment site. A smaller daughter catheter may then be
passed through the parent catheter to the treatment site. In this
instance a proximal balloon for flow restriction is not required.
Near occlusion of the vessel, without wedging the catheter, will
dramatically reduce flow also. This is shown in FIG. 42, in which
there is a large catheter 2702 and a smaller catheter 2703 for
aspiration of a clot 2701. Large bore highly flexible catheters can
enable the most distal flow arrest possible
[0255] In other instances, such as embolization, flow restriction
using a larger bore catheter may also be advantageous. For example,
in embolization, where embolization of non-target vessels is a
major concern, additional embolization procedures are often used
occlude adjacent non-target vessels. Non-target embolization can
cause non-target vessel occlusion, or the delivery of a drug to
non-target tissue. This may be avoided if a larger bore highly
flexible catheter is placed distally in the vessel feeding the
target region of delivery of the embolic such that the catheter tip
is wedged. Upon injection of the embolic, the wedged condition
prevents retrograde flow of the embolic, thus preventing non-target
embolization. Furthermore, the pressure gradient within the vessel
is a reflection of the proximal injection pressure, rather than the
hemodynamic pressure, giving the physician full control of the
delivery of the embolic.
[0256] FIG. 43 shows such a configuration, in a catheter 2800
having a distal portion 2801, Left shows the use of a small
catheter unable to reach a distal target vessel (right side vessel)
during delivery of a drug or embolic and the resulting undesired
delivery to a non-target vessel (top left vessel) The right hand
diagram shows the use of a method wherein a highly flexible large
diameter catheter is chosen to effectively occlude the target
vessel, and can be placed beyond the non-target vessel, so delivery
of the embolic only occurs to the target vessel. It is preferable
that the catheter is wedged in the target vessel.
[0257] Furthermore, the distal nature of the vessels targeted in
embolization procedures means that often, only microcatheters are
capable of entering the vessels today. This limits the type of
embolic which can be used (e.g. 018 microcoils may need to be used
where larger 035 coils or a plug would e preferred, or the desired
particle becomes clogged in the only microcatheter capable of
entering the vessel). The technical success of these procedures (in
particular embolization for BPH) is also limited by the inability
to place larger support catheters distally.
[0258] A corrugated catheter section with or without a transition
arrangement may be used as a proximal section of a catheter in
order to provide flexibility about a particular bend, for example,
as an access sheath to provide controlled flexibility about the
iliac arch. The configurations may could also be incorporated into
a more flexible a urethral stent design or Foley-style catheter,
and for a flexible endoscope of corrugate wall.
[0259] The device may be used to block blood flow before precise
delivery of an embolic agent to region of the vasculature, tumour,
or organ.
Aspiration System with Pressure-Controlling Pump
[0260] Aspiration has been shown to be safe for the retrieval of
clots from the cerebral vasculature. However, technique suffers
from a number of limitations. In particular, it is frequently the
case that the clot cannot be ingested at the target treatment site.
This is particularly the case for harder, larger diameter, and
longer clots.
[0261] If not completely ingested, the physician will attempt to
withdraw catheter and attached clot from the patient under
continuous vacuum. This manoeuvre carries risk, is time-consuming,
and means the physician has lost access to the target vessel.
[0262] If following angiography the physician determines that the
target region has not been reperfused, additional attempts must be
made to retrieve the clot. Up to five attempts, known as passes are
typically required. On average two attempts are required. In 20% to
30% of cases, aspiration is not successful after multiple attempts,
and physicians will switch to the use of a stent retriever
(Almandoz et al. 2015; Lapergue et al. 2017; Blanc et al. 2017;
Mohlenbruch et al. 2016). This further increases procedural time
and cost.
[0263] As the physician withdraws the catheter proximally towards
the access site (typically femoral or radial artery), there is a
likelihood that some or all of the clot may break off. These
fragments of clot, are known as emboli. Distal emboli lead to poor
reperfusion outcomes when assessed under angiography or other
imaging. Poor reperfusion, as defined by the TICI scale, is
associated with worse patient outcomes.
[0264] Another limitation of the aspiration technology is that it
is not always possible to advance the catheter tip to the face of
the clot. This is due to the extreme tortuosity which may be
present in the patient, meaning that often only small diameter
catheters such as microcatheters can reach the clot. Larger bore
catheters are known to have a greater potential to aspirate the
clot, but are frequently too stiff to navigate to the clot face. In
this instance, the physician may use a smaller bore catheter, but
is less likely to successfully aspirate the clot.
[0265] Depending on internal diameter of the catheter, and
properties of the clot (diameter, length, hardness/durometer,
elasticity etc.), there is a limit to the amount of clot which can
be aspirated into the catheter lumen. At this limit the catheter
may be described as being clogged. Large lumen catheters can
aspirate more clot than small lumen catheters without becoming
clogged. During aspiration, the limit to the amount of clot which
can be aspirated may be reached before a complete vacuum is
reached. This implies that the application of further vacuum does
not necessarily increase the amount of clot which is aspirated once
a certain limit is reached. This is shown schematically in FIGS.
44(a) to 44(e), showing a catheter tip 3500 being used to attempt
aspiration of a clot 3501. As illustrated, there is incomplete
aspiration. It is a limitation of existing vacuum technology
(vacuum pumps and syringes) that the applied vacuum is not
engineered to prevent clogging, or maximise efficiency of
aspiration.
[0266] Based on the problems outlined above, it is desirable to
enable the clot to be ingested at the target site in a single
manoeuvre. This will save time, reduce procedural complexity, and
minimise potential for clot fragmentation during clot
retrieval.
[0267] A pump is disclosed, for use in connection with a catheter
such as described above in any embodiment, to aspirate clots or
other materials from a blood vessel or other region of the body. An
aspiration device is shown schematically in FIG. 45, having a
catheter 3500, a guide 3502, tubing 3503, and a pump and reservoir
assembly 3504.
[0268] The invention utilises control and/or, variation of the
vacuum pressure and/or, fluid displacement during aspiration to
improve the efficiency of aspiration. Variations in pressure and/or
fluid displacement at the catheter tip can help achieve the
following: [0269] Prevent clogging of the catheter [0270] Promote
maceration and deformation of the clot to enable it to travel
through the lumen
[0271] The pump 3504 may provide a negative fluid displacement
thereby decreasing pressure (enabling a vacuum) or positive
displacement, thereby increasing pressure. The pump is connected to
a catheter, enabling application of a positive or negative pressure
the catheter lumen. The pump incorporates a sensor which measures
the pressure in the catheter lumen.
[0272] The magnitude of this pressure may be used to decide whether
a vacuum or pressurizing signal should be applied to the catheter.
Based on the measured pressure, the pump may change direction hence
altering the pressure and fluid displacement.
[0273] In one embodiment, shown schematically in the form of a
state diagram in FIG. 46, the pump uses defined upper and lower
limits to decide whether to apply a vacuum or pressurize. These
limits enable the catheter to cyclically ingest and if required
expel, at least some of the clot. This deformation of the clot
improves the efficiency of the aspiration, and prevents clogging of
the catheter.
[0274] For the purposes of explanation, the initial pressure is
defined as 0 in-Hg in all diagrams before the pump is switched on
FIG. 47(a). In reality, a non-zero pressure is present due to blood
pressure. This may be in the region of 60 to 120 mm-Hg (2.4-4.8
in-Hg).
[0275] The pump will continuously measure the pressure within the
catheter lumen during the procedure. This measurement will be
arterial pressure if the pump is switched off. Once the pump is
switched on, and it begins to draw some vacuum a negative pressure
will be measured, FIG. 47(b). In the absence of an occlusion or
partial occlusion of the catheter tip, this will be a nominal
reading, representing free-flow of fluid through the catheter).
Once the catheter is advanced and engaged with the clot, an
increase in the vacuum is observed, FIG. 47(c).
[0276] Initially when switched on the pump applies a vacuum
enabling the catheter to ingest some of the clot, FIG. 47(d). While
further increases in the vacuum ingest more of the clot, FIG.
47(e), the efficiency of increases in the vacuum pressure in
ingesting more clot is reduced, FIG. 47(f). For this reason, the
pump will reverse at some Low Limit of pressure, FIG. 47(g). The
Low Limit is defined such that during vacuum, a portion of the clot
has been aspirated but not so much that the clot has become
irreversibly clogged. An important aspect is that the lower limit
of vacuum can be set well above the full vacuum pressure of -760
mmHg to prevent ingestion of too large a clot that could clog the
catheter. In one embodiment, the Lower Limit is set to between -100
rnm-HG and -200 mm-Hg. In another embodiment the Lower Limit is set
to between -200 mm-HG and -300 mm-Hg. In another embodiment the
Lower Limit is set to between -400 mm-HG and -500 mm-FIg. In
another embodiment the Lower Limit is set to between -600 mm-HG and
-700 mm-Hg.
[0277] The direction of fluid displacement of the pump is now
reversed. Upon reversal, the catheter will begin to pressurize,
thereby increasing the pressure measured, FIG. 47(g). As the
catheter is pressurized (vacuum is reversed), the load which was
applied to ingest the clot will be reduced, thereby unloading the
clot, and even allowing some or all of the clot to be pushed
distally towards the catheter tip FIG. 47(h). During this
loading/unloading the clot is being macerated and accordingly
becomes more "free" within the catheter.
[0278] The pressure is further increased until a High Limit is
reached. In one embodiment this High Limit is defined such that the
ingested clot may not be completely expelled from the catheter.
[0279] Additional cycling of the clot between the Low Limit and
high limit (FIG. 47(i) to (j)) further macerates the clot enabling
a greater amount of the clot to be ingested for the same Low Limit
of vacuum (FIG. 47(m)), with eventual complete ingestion of the
clot, FIG. 47(n).
[0280] In one embodiment the High Limit is a negative pressure. In
another embodiment, the high limit may be 0 mmHg. In yet another
preferred embodiment, the High Limit is a positive pressure (FIG.
48(a) to (c).
[0281] In the absence of a pressure signal from the pump the
presence of intra-vascular blood pressure means there is a force
present which supports transport of material from the distal tip of
the catheter towards the pump. In one embodiment, an initial blood
pressure reading may be taken before the procedure is initiated.
This reading may be used to calculate the precise High Limit value
required. The mean blood pressure, systolic blood pressure, or
diastolic blood pressure may be used. A novel aspect of this pump
system is the incorporation of feedback into the pump algorithm in
order to produce more effective pressure cycling. That is to say,
the ability of the pump to measure the condition in the pump (e.g.
pressure or fluid displacement), and continue or alter its
behaviour.
[0282] In one embodiment, the applied pressure signal incorporates
an oscillation or "shake" signal. The shake signal implies the
application of pulse cycling between two pressure limits as shown
in FIGS. 50(a) and (b). The signal provides acute aspiration of the
clot in order to cause deformation and, or, fragmentation of the
clot to improve transport through the catheter. Another aspect is
the incorporation of rate based cycling of a negative and positive
pressure signal. Oscillating frequencies can be defined that may
cause the elastic modulus of a clot to be exceeded, thereby,
fragmenting the clot in the catheter and promoting easier
transport.
[0283] The addition of this oscillation is shown in the form of the
state diagram in FIG. 49.
[0284] In one embodiment the shake signal may be initiated for a
predefined number of cycles. In another embodiment, the shake
signal may be used until the pressure has returned to blood
pressure. In this instance the material in the catheter can
effectively flow without significant resistance. In another
embodiment, this shake signal may be initiated based on a specific
pressure indicative of catheter occlusion or partial occlusion, and
terminated based on measurement of pressure within the catheter
indicative of free-flow, or partial occlusion.
[0285] While the figures generally show a triangular wave form of
pressure with respect to time, it should be pointed out that this
may not be the case in reality. The graphs are intended to
illustrate the directional changes in pressure which are initiated
and controlled by the invention.
[0286] For example depending on the clot properties, and speed of
activation or reversal of the pump, the signals may be more square,
saw-tooth, or sinusoidal in form. Furthermore, the resulting
pressure-time relationship may not have any repeating unit at
all.
[0287] In one embodiment the invention includes both an oscillation
or shake signal in the vacuum and positive pressurize signals. This
is shown schematically in FIGS. 51(a) and 51(b). In yet another
embodiment, the system my incorporate only a vacuum
oscillation.
[0288] A range of Lower Pressure and Higher-Pressure limit values
may improve efficiency of clot transport compared to static
aspiration technology. In one embodiment it is preferable to
specify a Lower Pressure limit such that the amount of clot which
can be ingested is maximised for a single cycle. In another
embodiment, it is preferable that the Lower Pressure limit is
specified such that the amount of clot which is ingested in a
single cycle is not maximised, but instead represents an
intermediate condition between a small amount of clot ingestion and
maximum clot ingestion. Real numbers will be added in the future
based on experiment.
[0289] In another embodiment, the lower limit may be defined in
real-time. In one embodiment, a change in the rate of change of the
pressure during the vacuum cycle may be used. For example, as the
catheter becomes clogged, there is generally a rapid increase in
the vacuum pressure. This sudden change in vacuum pressure may be
used as a signal to switch the direction of the pump. Similarly,
the upper pressure may be defined based on a sudden change in the
pressure during the pressurize cycle. In one embodiment this may be
defined in order to identify a condition where the catheter is
de-clogged.
[0290] It should be appreciated that the upper and lower limits may
be defined by a combination of rate of change in pressure, or
specific pressure value, or a combination of both.
[0291] In another configuration, a flow displacement, or flow meter
is incorporated. This may be used to define upper and lower limits
to establish the direction of the pump (aspiration or vacuum). In
one embodiment the flow meter can detect if there is no fluid
displacement, which is suggestive of catheter clogging.
[0292] In another embodiment, the pump may use positive and
negative fluid displacement to alternately infuse and aspirate the
catheter. In one embodiment, the ratio of the infuse-to-aspirate
cycle may be between 0.01 and 0.99. Preferably the ratio will
between 0.1 and 0.9, or more preferably between 0.4 and 0.9.
[0293] In one configuration, the pump is a sterile unit, which can
be used within the sterile field, or on the patient table adjacent
to the patient. This enables the physician to perform all
manoeuvres without the requirement of a technician outside the
sterile field. The unit may be single use and disposable.
[0294] In one configuration, the pump incorporates a peristaltic
pump mechanism. This ensures that there is no blood contact with
the pump parts. The pump may incorporate a reservoir for collection
of aspirate. FIGS. 53(a) and 53(b) show a pump and components.
Shown are a housing connecting a tube, an on-off switch, a battery
pack, a pulsatile pump, and a motherboard. The pressure sensor is
connected to the tube-lumen, which is connected to the catheter,
thereby enabling pressure measurement within the catheter.
[0295] In one embodiment the pump incorporates a series of LEDs or
indicators. These are intended to provide feedback to the physician
based on the catheter tip and clot interaction condition. This is
provided by the pressure within the catheter. For example, the
pressure range associated with free-flow within the catheter, or
partial occlusion, or complete occlusion, aspirating or
clogged.
[0296] Furthermore, the indicators may be used to indicate to the
physician that the pump is in the oscillation or shake
condition.
[0297] A method is disclosed whereby the physician uses the
feedback from the indicators to define the required adjustment of
the catheter tip.
[0298] Place catheter tip adjacent to the clot. Switch on the pump.
If the pump indicates free flow is observed the catheter should be
moved distally to further engage the clot. If the catheter is
aspirating with partial or complete occlusion the physician waits
until the pump has free-flow again. The physic again moves the
catheter tip distally to engage the next piece of clot. In this way
the entire vessel can be cleaned of clot. In the event that the
pump becomes clogged, a signal may be provided to the physician
that the traditional catheter withdrawal technique may be
appropriate.
[0299] The embodiments described within this filing are in general
aimed at enabling the physician to access regions of the body which
provide a challenging anatomy, with highly flexible corrugated
catheters. The catheter designs are optimised by way of
transitions, and the addition of other elements, such as flow
restrictors and a highly effective pump. The ability to make larger
catheters while maintaining this type of controlled flexibility
enables improved therapy, such as clot removal, embolic delivery to
the body.
[0300] The invention is not limited to the embodiments described
but may be varied in construction and detail.
* * * * *