U.S. patent application number 12/639870 was filed with the patent office on 2010-04-29 for ablation catheter.
This patent application is currently assigned to CathRx Ltd. Invention is credited to Neil L. ANDERSON, Evan Chong.
Application Number | 20100106155 12/639870 |
Document ID | / |
Family ID | 3835835 |
Filed Date | 2010-04-29 |
United States Patent
Application |
20100106155 |
Kind Code |
A1 |
ANDERSON; Neil L. ; et
al. |
April 29, 2010 |
ABLATION CATHETER
Abstract
An ablation catheter 10 includes an elongate carrier 12. A first
loop 14.1 is arranged at, or adjacent, a distal end of the carrier
12. At least one sensing electrode 40 is carried on the first loop
14.1 for sensing irregular electrical activity in a patient's body.
At least one further loop 14.2 is arranged proximally relative to
the first loop 14.1 on the carrier 12 in a fixed orientation
relative to the first loop 14.1. At least one ablating electrode 42
is carried on the second loop 14.2 for ablating a site of the
patient's body where irregular electrical activity occurs.
Inventors: |
ANDERSON; Neil L.;
(Roseville, AU) ; Chong; Evan; (South Strathfield,
AU) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
755 PAGE MILL RD
PALO ALTO
CA
94304-1018
US
|
Assignee: |
CathRx Ltd
Homebush Bay
AU
|
Family ID: |
3835835 |
Appl. No.: |
12/639870 |
Filed: |
December 16, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11881431 |
Jul 27, 2007 |
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12639870 |
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10514308 |
Nov 9, 2005 |
7347857 |
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PCT/AU03/00559 |
May 9, 2003 |
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11881431 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 18/1492 20130101;
A61B 2018/00375 20130101; A61B 2018/00357 20130101; A61B 2018/00839
20130101; A61B 2018/1407 20130101; A61B 2018/00821 20130101 |
Class at
Publication: |
606/41 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2002 |
AU |
PS2264 |
Claims
1-27. (canceled)
28. An ablation catheter which includes an elongate carrier
defining an outer periphery, the elongate carrier comprising a
tubular member defining a lumen, electrical conductors arranged
about a part of the tubular member defining the lumen and the
conductors being covered with a coating of an insulating material
so that the conductors are embedded in a wall of the tubular member
with the coating defining the outer periphery of the tubular
member; and at least one ablating electrode carried on the outer
periphery, the at least one ablating electrode being shaped to be
on an operatively outer part only of the carrier and being in
electrical communication with at least some of the conductors of
the carrier by removal of a part of the coating of insulating
material with the at least one electrode overlying the opening.
29. The catheter of claim 28 in which the outer periphery of the
carrier is a radially outer part of at least one loop defined by
the carrier and the at least one electrode is carried partially
about the radially outer part of the at least one loop.
30. The catheter of claim 28 in which the at least one electrode is
of semi-cylindrical shape.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/514,308, filed Nov. 12, 2004, which is a national phase filing
of PCT/AU03/00559, filed May 9, 2003, which claims the benefit of
Australian application PS2264, filed May 13, 2002, the disclosures
of which are incorporated herein by reference in their
entirety.
FIELD
[0002] This invention relates to a catheter. The invention relates
particularly, but not necessarily exclusively, to an ablation
catheter for the treatment of atrial fibrillation.
BACKGROUND
[0003] Atrial fibrillation is a condition that affects large groups
of people with new patients being diagnosed each year. These
patients have a lower quality of life as well as having up to a
seven times increase in the likelihood of heart attacks or strokes.
Current therapies include drug treatment or defibrillation, both
palliative forms of treatment. Over the past few years, a number of
research groups have been investigating curative treatment
involving ablative techniques using radio frequency (RF),
ultrasound, laser or microwave energy or cryoablation
techniques.
[0004] Ablation therapy, while being promising, requires complex
catheter designs. Such catheters also have to be reasonably thin to
be manoeuvred through a patient's vascular system.
[0005] A current approach is the use of a catheter in the shape of
a lasso which has a number of electrodes used for diagnostic
purposes only. The lasso is positioned through the left atrium of
the heart in pulmonary veins. As the lasso is round in shape, it
surrounds the inside of the vein. Different sizes of catheters are
required depending on the size and shape of the ostium. A typical
procedure uses a first catheter to sense regions of irregular
electrical activity and a second, separate, ablation catheter to
ablate the specific site of irregular electrical activity. The
procedure is repeated at various sites until all sites of irregular
electrical activity have been blocked. One of the disadvantages
associated with this procedure is the difficulty in guiding the
ablation catheter to the exact site of the vein at which ablation
is to occur. In this regard, it must be borne in mind that the
first catheter which is used to sense the irregular electrical
activity needs to be retained in position while the second catheter
is inserted through the patient's vascular system to the site to
guide the ablation catheter to that site. In addition, too much
energy can lead to excessive tissue damage which can lead to
stenosis of the blood vessel. Conversely, too little energy or
insufficient ablated sites can lead to a re-occurrence of the
irregular, electrically conductive pathways and therefore the
likelihood of further atrial arrhythmia.
SUMMARY
[0006] According to a first aspect of the invention, there is
provided an ablation catheter which includes:
[0007] an elongate carrier;
[0008] a first loop arranged at, or adjacent, a distal end of the
carrier;
[0009] at least one sensing electrode carried on the first loop for
sensing irregular electrical activity in a patient's body;
[0010] at least one further loop arranged proximally relative to
the first loop on the carrier in a fixed orientation relative to
the first loop; and
[0011] at least one ablating electrode carried on the second loop
for ablating a site of the patient's body where irregular
electrical activity occurs.
[0012] Preferably, the catheter includes a plurality of sensing
electrodes arranged at circumferentially spaced intervals about the
first loop and a plurality of ablating electrodes arranged at
circumferentially spaced intervals about the second loop. When
viewed longitudinally along the carrier, each ablating electrode of
the second loop may be aligned with a sensing electrode of the
first loop.
[0013] The elongate carrier may include a tubular member defining a
lumen and a shape forming member carried in the lumen for forming
the loops. The shape forming member may be of a shape memory alloy
such as a nickel, titanium alloy.
[0014] The tubular member may act as a mandrel for electrical
conductors for the electrodes of the first loop and the second
loop, the conductors being arranged about an outer surface of the
tubular member and being covered with a coating of an insulating
material. This leaves a lumen of the tubular member free for the
passage of other elements, such as steering cables, conduits for
cooling fluids etc. At predetermined locations along the coating,
the coating may be removed to expose the conductors and electrodes
may be applied at these exposed locations.
[0015] The tubular member may be folded back on itself to form a
distal hairpin and a pair of limbs extending from the hairpin, the
limbs having a pair of proximal ends, the loops being carried on
the limbs and a size of each loop being adjustable by appropriate
manipulation of the proximal end of at least one of the limbs.
[0016] An electrically isolating discontinuity may be arranged
between the loops isolating the conductors of the first loop from
the conductors of the second loop. The second loop may be arranged
on one of the limbs proximally of the discontinuity with the first
loop also being arranged on the first limb but between the
discontinuity and the hairpin, the electrical conductors for the
ablating electrodes of the second loop extending along the one limb
and the electrical conductors for the sensing electrodes of the
first loop extending along the other limb and through the hairpin
into the one limb.
[0017] It will be appreciated that, because the lumen is free of
conductors, it can be made more narrow. Also, the fact that
conductors for each of the loops run in separate limbs of the
tubular member means that more electrodes can be carried on each
loop without adversely affecting the size of the catheter. As a
result, the accuracy of sensing measurements and ablating
procedures is improved because greater resolution is possible than
has heretofore been the case.
[0018] In the manufacture of the catheter, the conductors may be
mounted on the tubular member prior to folding the tubular member.
The electrodes may be formed at the desired locations along the
length of the conductors where after the tubular member is folded
back on itself and cut to isolate the electrodes on one loop from
the electrodes on the other loop with each set of electrodes having
its own conductors. The shape forming member may then be inserted
into the lumen of the tubular member to form the loops.
[0019] The first loop, which is arranged at a distal end of the
catheter may have only electrodes without any temperature sensing
means and may be used for sensing electrical activity in the
pulmonary vein. The second loop, being proximally arranged relative
to the first loop may, in use, be located at, or adjacent, the
ostium of the pulmonary vein and may be used for ablating purposes.
Thus, the second loop may include the electrodes and the
temperature sensing means. It will be appreciated that the catheter
may comprise more than two loops, with one being used for sensing
and two being used for ablation or vice versa.
[0020] The electrodes of the second loop of the catheter may be
used both for sensing undesirable or irregular electrical activity
at, or adjacent, the ostium of the pulmonary vein and for ablating
tissue at, or adjacent, the ostium of the pulmonary vein at where
such undesirable electrical activity occurs. Thus, where any
electrode of the first loop or the second loop senses undesirable
electrical activity, the relevant electrode or electrodes of the
second loop may be used to ablate the tissue to form a lesion in
the region of the ostium to disrupt the electrically conductive
pathway in the tissue to reduce atrial fibrillation.
[0021] The catheter may include a tubular introducer for
introducing the carrier into the patient's body, the carrier being
slideably received in a passage of the introducer and being
slideable relative to the introducer between a first, retracted
position in which the loops are contained in a collapsed
configuration in the passage of the introducer and a second,
extended configuration in which the loops are in an expanded,
loop-shaped configuration and are distally arranged relative to a
distal end of the introducer. When the loops are in their second,
extended configuration, each loop may lie in a plane transverse to
a longitudinally axis of the carrier. The planes may be
substantially parallel to each other.
[0022] As a result of the looped arrangement of the electrodes,
when the catheter is inserted into the blood vessel, an operator
will know which parts of each loop and, hence, which side of each
electrode is in contact with a wall of the blood vessel and which
side is in contact with blood within the blood vessel. As it is
undesirable to impart heat to the blood carried in the blood
vessel, each electrode may be cuff-shaped to extend only partway
about the periphery of the carrier, the arrangement being such that
the electrodes are arranged on an outer side of their loops. By
"cuff-shaped", it is meant that the electrodes are semi-circular
cylindrical in shape.
[0023] Each of at least certain of the electrodes at least on the
second loop may have a temperature measuring facility associated
with it. The temperature measuring facility may be a thermocouple.
Those electrodes operative also to measure temperature may
therefore have three conductors associated with them. Those
electrodes used only for sensing or ablating may only have a single
conductor associated with them.
[0024] According to a second aspect of the invention, there is
provided an ablation catheter which includes
[0025] an elongate carrier having a loop defined at a distal end,
the loop comprising a first arm and a second arm, the arms of the
loop being at least partly electrically isolated with respect to
each other; and
[0026] at least one electrode arranged on each arm of the loop.
[0027] Preferably, each arm carries a plurality of electrodes. The
electrodes may be serially arranged along a length of each arm.
[0028] The carrier may comprise a tubular member defining a lumen
with a shape forming member being received in the lumen for forming
the loop.
[0029] The tubular member may act as a mandrel for electrical
conductors for the at least one electrode of the loop, the
conductors being arranged about an outer surface of the tubular
member and being covered in a coating of an insulating
material.
[0030] The tubular member may be folded back on itself to form a
distal hairpin and a pair of limbs extending from the hairpin, each
limb having proximal end, the arms of the loop being defined by
distal portions of the limbs on opposite sides of the hairpin.
[0031] The arms of the loop may be electrically isolated from each
other at a distal end of the loop. Thus, the tubular member may
include an electrically isolating discontinuity at the distal end
of the arms, more particularly, at the hairpin. For example, the
arms may be cut and then re-connected in an electrically isolated
manner.
[0032] By "at least partly electrically isolated, it is meant that,
in respect of most conductors of each limb, the conductors
terminate before, or at, the discontinuity. However, it may be
required that at least certain of the conductors traverse the
discontinuity, ie. extend up through one limb and return through
the other limb. Such conductors would then not be terminated
before, or at, the discontinuity.
[0033] A temperature measuring facility may be associated with at
least certain of the electrodes.
[0034] The electrodes may be shaped only to be on an operatively
outer part of the loop. More specifically, each electrode is
substantially semi-cylindrical in shape, or cuff-shaped, as opposed
to being in the form of a band or annulus.
[0035] The semi-cylindrical electrodes may be longer than
band-shaped electrodes so that a surface area of each
semi-cylindrical electrode is substantially the same as that of a
conventional band-shaped, ablating electrode to have the same
current density in the semi-cylindrical ablating electrodes, in
use.
[0036] According to a third aspect of the invention, there is
provided an ablation catheter which includes
[0037] an elongate carrier defining an outer periphery; and
[0038] at least one ablating electrode carried on said outer
periphery, said at least one ablating electrode being arranged only
partially about the periphery of the carrier.
[0039] The outer periphery may be a radially outer part of at least
one loop carried by the carrier and the at least one electrode may
be carried partially about the radially outer part of the at least
one loop. The at least one electrode may be of semi-cylindrical
shape.
[0040] In the case of all aspects as described above, a source of
energy for effecting ablation may be selected from the group
comprising radio frequency, microwave, ultrasound, laser and
cryoablative energy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The invention is now described by way of example with
reference to the accompanying drawings in which:
[0042] FIG. 1 shows a schematic representation of an ablation
catheter, in accordance with a first aspect of the invention, in an
initial stage of formation;
[0043] FIG. 2 shows a schematic representation of the catheter;
[0044] FIG. 3 shows a schematic representation of an interior cross
section of the catheter;
[0045] FIG. 4 shows a three dimensional view of an ablation
catheter, in accordance with the first aspect of the invention;
[0046] FIG. 5 shows a three dimensional view of an ablation
catheter, in accordance with a second embodiment of the invention;
and
[0047] FIG. 6 shows a schematic, cross sectional view of an
ablation catheter, in accordance with a third aspect of the
invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0048] In the drawings, reference numeral 10 generally designates
an ablation catheter, in accordance with an embodiment of the
invention. The catheter 10 include an elongate carrier in the form
of a tubular member 12 having a loop 14 defined at a distal end of
the carrier 12, the loop 14 being formed by two arms 18, 22. The
arms 18, 22 are joined at a distal end of the loop 14. A plurality
of electrodes 16 is carried on one arm 18 of the loop 14 with a
similar number of electrodes 20 being carried on the opposed arm 22
of the loop 14.
[0049] The tubular member 12 defines a lumen 24.
[0050] In the fabrication of the catheter 10, in accordance with
one embodiment of the invention and as shown in FIG. 1 of the
drawings, the tubular member 12 is folded back on itself into a
substantially hairpin shape to define a pair of limbs 26, 28 joined
at a hairpin 29. Conductors, five of which are shown schematically
at 30 in FIG. 3 of the drawings, are embedded in a wall of the
tubular member 12. In the fabrication of the tubular member 12,
once the conductors 30 have been placed in position about the
outside of a part of the tubular member 12 defining the lumen 24, a
covering or coating 31 of an insulating material is applied to the
conductors 30 to form the finished tubular member 12.
[0051] At the distal end of the tubular member 12, the coating of
insulating material 31 is removed to expose the conductors 30.
Metal is applied by a deposition technique to form the electrodes
16, 20. The metal of the electrodes 16, 20 is of a bio-compatible
material such as a noble metal, for example, platinum.
[0052] Once the electrodes 16, 20 have been formed, the tubular
member 12 is cut at its distal end, as indicated at 32 in FIGS. 1
and 2 of the drawings. This includes cutting the conductors 30. The
cut ends are re-joined in an electrically isolated manner to form
the two arms 18, 22 of the loop 14.
[0053] As illustrated in FIG. 3 of the drawings, a further tube 34
is inserted into the lumen 24 of the tubular member 12. This tube
34 accommodates a shape forming member 36 such as a length of
nickel, titanium alloy (Nitinol.TM.) which is used in forming each
arm 18, 22 of the loop 14, as will be described in greater detail
below. The length of shape forming member 36 has two, protruding,
proximal ends 36.1
[0054] The catheter 10 includes an introducer or sleeve 38 in which
the hairpin shaped tubular member 12 is received for use The ends
36.1 of the shape forming member 36 protrude from a proximal end of
the introducer 38 and are used for adjusting the size of the loop
14 to cater for various sizes of pulmonary vein ostia. The
introducer 38 includes a steering mechanism (not shown) for
steering the catheter 10 through the vascular system and heart of a
patient undergoing treatment.
[0055] In use, to treat atrial fibrillation, the catheter 10 is
inserted via the patient's vascular system and the left atrium of
the heart into the ostium of the pulmonary vein to be treated where
atrial arrhythmia may be occurring. To facilitate insertion of the
catheter 10, the loop 14 is retracted into the introducer so that
the loop 14 adopts a collapsed configuration within the introducer
38 as the introducer 38 is steered to the relevant site by an
operator. At the desired location relative to the ostium, the
tubular member 12 is urged towards the distal end of the introducer
38 to eject the loop-defining part of the tubular member 12 out of
the distal end of the introducer 38, the length of shape forming
member 36 acting on the distal end of the tubular member 12, as the
distal end of the tubular member 12 escapes from the introducer 38,
to form the arms 18, 22 of the loop 14.
[0056] Sensing of electrical activity at or adjacent the ostium
takes place by the electrodes 16 and 20 acting as sensing
electrodes.
[0057] To assist the clinician in placement of the loop 14 relative
to the pulmonary vein, radio opaque tokens (not shown) in the form
of bands may be arranged at various location on the loop 14. The
radio opaque bands may be identified with certain of the electrodes
16, 20 so that the clinician knows exactly where the electrodes 16,
20 are positioned at the various locations about the wall of the
pulmonary vein. This is only necessary if the electrodes 16, 20 are
not visible under a fluoroscope.
[0058] An additional lumen 44 extends along the lumen 24 of the
tubular member 12 to the electrodes 16, 20 to provide delivery of a
fluid, such as a saline solution, to the electrodes 16, 20 during
ablation. Due to the fact that the electrodes 16, 20 are coated on
the tubular member 12, this facilitates the formation of an opening
through each electrode 16, 20 through which the saline solution can
be delivered. Instead of the saline solution being ejected through
openings in the electrodes, the solution could, instead, be
circulated through a suitable conduit (not shown) arranged in the
lumen 24 of the tubular member 12 and extending through the limbs
26, 28 of the tubular member. In this way, the electrodes 16, 20
may be cooled allowing for higher energies and deeper lesions while
inhibiting overheating of the tissue or blood in the vessel.
[0059] FIG. 4 of the drawings shows a configuration where a single
loop 14 is provided. In this embodiment of the invention, the
electrodes 16, 20 are used both for sensing of electrical activity
as well as for ablating purposes.
[0060] In the embodiment of the invention shown in FIG. 5 of the
drawings, a catheter 10 is provided which includes two loops 14.1
and 14.2. The loop 14.1 is arranged at the distal end of the
catheter 10 and includes only sensing electrodes 40 arranged about
the loop 14.1.
[0061] The loop 14.2 is arranged proximally relative to the loop
14.1 and includes only ablating electrodes 42 arranged about the
loop 14.2. However, if desired, the electrodes 42 of the loop 14.2
are also used for sensing of irregular electrical activity, in
addition to performing their ablating function.
[0062] In the formation of the catheter 10 of FIG. 5, the cut 32
formed in the tubular member 12 is arranged proximally of the
hairpin 29 so that the loop 14.2 is formed proximally of the cut 32
and the loop 14.1 is formed intermediate the cut 32 and the hairpin
29. The conductors 30 for the loop 142 extend along the limb 26 of
the tubular member 12, the limb 26 terminating at the cut 32. The
conductors 30 for the loop 14.1 extend along the limb 28 of the
tubular member 12, the limb 28 forming the hairpin 29 and
terminating at the cut 32. It is to be noted that, in this
embodiment of the invention, it is not essential that the
conductors 30 for each of the loops 14.1 and 14.2 extend along
separate limbs. In other words, the cut 32 in the tubular member 12
is not essential.
[0063] In use, the catheter 10 of FIG. 5 is used in a similar
manner to that described above with reference to FIG. 4. The
catheter 10 is introduced into the patient's vascular system with
the loops 14.1 and 14.2 retracted, in a collapsed configuration
into the introducer 38. The catheter 10 is inserted via the left
atrium of the patient's heart. At the relevant pulmonary vein, the
loops 14.1 and 142 are urged distally out of the introducer 38 so
that the shape forming member 36 causes the loops 14.1 and 14.2 to
form. When the loops 14.1 and 14.2 are ejected from the catheter
10, they adopt an erected configuration in which the loops 14.1 and
14.2 lie in planes that are substantially parallel to each other
and transversely to a longitudinal axis of the catheter 10. The
loop 14.1 is received within the pulmonary vein with the loop 14.2
being arranged at, or adjacent, the ostium. The electrodes 40 and
42 are arranged on the loops 14.1 and 14.2, respectively, so that
they are aligned with each other longitudinally along the tubular
member 12. The spacing between the loops 14.1 and 14.2 is such
that, in all likelihood, should adverse electrical activity be
picked up by one of the electrodes 40 of the loop 14.1, the
corresponding, aligned electrode 42 of the loop 142 can be used to
ablate the tissue at the ostium which should result in ceasing of
the adverse electrical activity. Accordingly, this aspect of the
invention provides separate electrodes for sensing and for ablating
purposes.
[0064] Referring now to FIG. 6 of the drawings, apart of the
catheter 10 showing one of the electrodes 16, 20, 40 or 42, in
accordance with another aspect of the invention, is illustrated.
The electrodes 16, 20, 40 or 42 do not extend all the way about the
periphery of the tubular member 12. Rather, the electrodes 16, 20,
40 or 42 are each in the form of a cuff-like member which extends
only part way, approximately halfway, about the periphery of the
tubular member 12. Hence, when the loop or loops 14 are formed, the
cuff-like electrode 16, 20, 40 or 42 as the case, are arranged on a
part of each loop facing radially outwardly to be in contact with
the wall of the pulmonary vein to effect sensing/ablating. With
this configuration of electrodes 16, 20, 40, 42 electrical energy
is focused towards ablating the tissue rather than ablating and
coagulating blood in the vessel. This improves the creation of the
lesion in the wall of the vein and optimises the size/depth of the
lesion while lessening the likelihood of stenosis of the vein
occurring.
[0065] A further benefit of this arrangement is that, with
comparison to a band-type electrode, the cuff-type electrode 16,
20, 40 or 42 has a greater length to provide a similar surface area
to the band-type electrode. The greater length of the cuff-shaped
electrode 16, 20, 40 or 42 means that a longer lesion can be formed
with the same current density as presently used.
[0066] Further, as illustrated in FIGS. 3 and 6 of the drawings,
because the conductors 30 for the electrodes 16, 20, 40, 42 are
embedded in a wall of the tubular member 12, it results in a
catheter 10 which is thinner than multi-electrode catheters of the
type presently in use. This facilitates manipulation of the
catheter 10 through the vessels and/or heart of the patient. It
also means that the lumen 24 of the tubular member 12 is free to
accommodate the length of shape-forming member 36 and, where
applicable, the conduit 44 for the delivery of a saline
solution.
[0067] While the catheter 10 has been described with reference to
its application in the treatment of atrial fibrillation, it will be
appreciated that the catheter 10 could also be used in other
applications such as in the treatment of ventricular tachycardia.
It could also be used in non-cardiac applications such as in the
ablation of tumours or of the prostate.
[0068] Further, it is to be noted that any electrode that is being
used of ablation can have a thermocouple pair underneath it if
needed. Thus some of the ablating electrodes have three conductors
30 associated with them while others only have one conductor 30.
Separate electrodes to be used as thermocouples could also be
provided but this would increase the number of electrodes. Such
separate electrodes would each have two conductors 30 associated
with them.
[0069] An example of a catheter 10 is given below:
[0070] A one metre length of 0.4 mm stiff shape forming wire 36
which has two loops 14.1 and 14.2, each of 20 mm diameter shape
formed therein and positioned halfway along the length of the wire
36 was passed in a lumen 24 of a tubular member 12 of 1.6 mm
diameter with a Pebax.TM. jacket 31. The tubular member 12 carried
twenty 0.16 mm conductors 30 helically wound around an outer
surface of the lumen 24 and embedded in the jacket 31. The tubular
member 12 was folded back on itself so that the loops 14.1 and 14.2
were arranged at the distal end with the loop 14.2 being arranged
proximally of the loop 14.1. The folded tubular member 12 had the
ends 36.1 of the shape forming wire 36 protruded from the aligned
proximal ends of the tubular member 12 and was inserted in an
introducer 38 so that the loops 14.1 and 14.2 could be ejected
through a distal end of the introducer 38 to adopt their erected
configuration. It was shown that, by manipulating the ends 36.1 of
each limb 26, 28 of the tubular member 12 relative to the
introducer 38, the diameter of each of the loops 14.1 and 14.2
could be adjusted independently of each other.
[0071] It is a particular advantage of the invention that a
catheter 10 is provided which is used both for sensing and ablating
in the treatment of atrial fibrillation. Also, with the
construction of the tubular member 12 having the conductors 30
embedded therein, a catheter 10 which is of thinner construction
than catheters of which the applicant is presently aware, can be
formed resulting in easier manipulation of the catheter 10.
[0072] Another advantage of the catheter 10 of the present
invention is that, in comparison with existing catheters, the split
construction of the tubular member 12 means that double the number
of conductors 30 can be accommodated and, consequently, double the
number of electrodes 16, 20, 40 or 42. This has the benefit that
more electrodes can be carried on each loop 14 without adversely
affecting the size of the catheter 10. As a result, the accuracy of
sensing measurements and ablating procedures is improved because
greater resolution is possible than has heretofore been the
case.
[0073] With the double loop configuration of the catheter 10, the
fact that the loops 14.1 and 14.2 are in a fixed orientation
relative to each other reduces the risk of the loop 14.1 being
inserted too deeply into the pulmonary vein. As a result the
likelihood of trauma to the vein is reduced.
[0074] Prior art catheters of which the Applicant is aware perform
a circumferential ablation. Still another advantage of the present
invention is that individual electrodes can be controlled
independently to ablate small, segmented regions of tissue rather
than creating an entire circular lesion. As a result, less trauma
is caused to the patient and more accurate directing of the
ablating at the target site can be effected.
[0075] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
* * * * *