Note: Descriptions are shown in the official language in which they were submitted.
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COILED ABLATION CATHETER SYSTEM
FIELD OF THE INVENTION
The present invention relates generally to catheter systems, and more
particularly, to catheter systems for ablating and/or isolating foci that
contribute to
cardiac arrhythmia.
BACKGROUND OF THE INVENTION
Catheters are commonly used in surgical procedures to access certain areas of
a
patient's body without resorting to invasive surgical procedures. For example,
catheters are widely used in the field of cardiology to conduct
electrophysiological
studies in which electrical potentials within the heart are mapped to
determine the cause
and location of arrhythmia. In many cases, certain undesired conductive
pathways,
known as foci, contribute to and cause the arrhythmia. Once the location of
foci is
identified, elements on or within the catheter can be utilized to ablate or
isolate the foci,
thus eliminating the arrhythmia.
One form of arrhythmia is atrial fibrillation, which is an uncoordinated
contraction of the heart muscle within the atrium. Atrial fibrillation results
from
rapidly discharging foci and causes irregular heart beats, possibly leading to
inefficient
pumping of blood. In a significant number of patients, the foci that
contribute to this
condition are located within the pulmonary vein, adjacent to the atrium. These
foci
may be in the form of scattered groups of rapidly discharging cells. Treatment
of this
condition can sometimes be effective through the ablation of these foci.
However,
identifying the location of these foci and effecting the ablative treatment of
the foci can
be time consuming and difficult.
A variety of cardiac mapping and ablation catheter systems are well known in
the art. For example, U.S. Patent No. 5,476,495 (Kordis et al.) discloses a
steerable
catheter system that is able to conduct cardiac mapping and ablation. U.S.
Patent No.
5,507,743 (Edwards et al.) discloses a radio frequency (RF) treatment
apparatus that
includes a RF electrode that assumes a helical orientation upon deployment.
U.S.
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Patent No. 5,738,683 (Osypka) discloses a cardiac mapping/ablation catheter
that
includes an electrode that may be deployed in the shape of a loop. U.S. Patent
No.
5,782,879 (Imran) discloses an endocardial mapping and ablation system in
which the
catheter includes a deployable distal extremity, in the form of a cage-like
member that
includes a plurality of electrodes.
Despite the existence of these references and existing ablation catheter
systems,
there exists a need to provide a system that is able to effectively treat
atrial fibrillation
conditions that are caused by foci present within the pulmonary vein.
SUMMARY OF THE INVENTION
The present invention provides a cardiac catheter system for ablating tissue
to
electrically isolate certain tissue from arrhythmia-inducing foci. Although
the invention
is primarily shown and described as a cardiac catheter system for ablating
tissue with RF
energy, it is understood that the system has other applications and
embodiments as well.
For example, other types of energy, such as microwave, laser, cryogenic, and
ultrasonic
energy, can be used without departing from the scope of the invention.
In one embodiment, a cardiac ablation catheter system includes an elongate,
flexible sheath having an internal lumen and an open distal end. An ablating
element is
disposed within the sheath and is selectively deployable therefrom so as to
project from
the sheath in a substantially coil-like shape. In an exemplary embodiment, the
deployed
ablating element has a geometry forming at least one revolution for generating
a
circumferential lesion within a vessel, such as a pulmonary vein. In general,
the ablating
element is oriented in a plane that is substantially orthogonal to the
longitudinal axis of
the sheath in the deployed position to facilitate the formation of a lesion
about the vein
inner wall circumference.
The catheter system can include a variety of mechanisms for deploying the
ablation member from the catheter. In one embodiment, the ablation member is
released
from a distal end of the catheter such that it assumes a predetermined shape.
In another
embodiment, the catheter includes a hatch or port from which the ablation
member is
selectively deployed. In a further embodiment, the elongate member includes a
distal end
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affixed to a support member that is extendable from the catheter distal end.
By rotating
and/or longitudinally displacing the support member, the ablation member can
be
deployed such it assumes a desired size.
To ablate or isolate the target foci tissue, the catheter is manipulated
through the
arterial network until the catheter is located proximate the desired treatment
site. For
example, the treatment site may be a location within the pulmonary vein or
left atrium
at or near the pulmonary vein os or in the right ventricular outflow tract,
such as at the
junction of the right atrium and superior vena cava. The ablating element is
then
deployed from the catheter such that the coil-like ablating element is
generally oriented
in a plane orthogonal to the longitudinal axis of the sheath. The deployed
ablating
element should be in contact with tissue about the circumference of the vein
inner wall,
such as at the os. The ablation element is then energized to ablate the target
tissue to
electrically isolate the foci from healthy tissue on the opposite side of the
formed
lesion. The atria, for example, can be electrically isolated from a treated
pulmonary
vein by creating a circumferential lesion on the inner wall of the left atrium
or in the
pulmonary vein proximate the os.
Accordingly, in one aspect the present invention resides in an ablative stent
device comprising: a self-expanding stent adapted to be implanted and deployed
within
a vessel to provide circumferential support of the vessel; said stent
including a proximal
portion having a first diameter and an ablation region along at least a
portion of its
length, the ablation region being adapted for surface contact with the vessel
and the
ablation region subtending at least a substantially complete circumferential
band and
being effective to ablate a signal-blocking path within the vessel upon
application of
energy to the stent, the stent further including a distal portion having a
second diameter
that is less than the first diameter and that is sufficient to enable the
stent to seat within
the vessel.
In another aspect, the present invention resides in a catheter for use in
ablating a
selected region of body tissue, comprising:
(a) the catheter comprising:
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an elongate, flexible sheath having an internal lumen, an open distal end
and a longitudinal axis;
an ablating element disposed within the sheath and selectively
deployable therefrom so as to project from the sheath in a pulmonary vein with
a substantially coil-like shape having at least one revolution, wherein the
ablating element is positionable, in a deployed condition, is in a plane that
is
substantially orthogonal to the longitudinal axis of the sheath; and at least
one
exposed, conductive region disposed on at least a portion of the ablating
element;
(b) the ablating element being distally advancable out of the sheath to allow
the ablating element to form a substantially coil-like shape having at least
one
revolution;
(c) the ablating element having a conductive region sized for contact along
a selected circumferential region of body tissue at the pulmonary vein; and
wherein
(d) the catheter is operable to transmit ablating energy to the ablating
element while contacting the selected region of body tissue to form a
circumferential lesion blocking arythmia signals originating in the pulmonary
vein.
In a further aspect, the present invention resides in a catheter for use in
ablating
a selected region of body tissue, comprising the steps of:
(a) the catheter comprising:
an elongate, flexible sheath having an internal lumen, an open distal
end and a longitudinal axis;
an ablating element disposed within the sheath and selectively
deployable therefrom so as to project from the sheath in a substantially coil-
like shape having at least one revolution, wherein the ablating element, in a
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deployed condition is oriented in a plane that is substantially
orthogonal to the longitudinal axis of the sheath; and
at least one exposed, conductive region disposed on at least a portion
of the ablating element;
(b) the ablating element being advancable distally out of the sheath to
allow the ablating element to form a substantially coil-like shape having at
least one revolution and a conductive region which is contactable with a
selected region of body tissue; and
(c) wherein the catheter is operable to transmit ablating energy to the
ablating element while contacting the selected region of body tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood from the following detailed
description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a perspective new of an ablation catheter system in accordance with
the present invention;
FIG. 2 is a side view of a portion of the catheter system of FIG. 1;
FIG. 3 is a front view of a portion of the catheter system of FIG 1;
FIG. 4 is a pictorial representation of the orientation of an ablating element
in a
deployed position and a catheter that forms a part of the catheter system of
FIG. 1;
FIG. 5 is a perspective view of an alternative geometry for an ablating
element;
FIG. 6 is a perspective view of a further embodiment of an ablation catheter
system in accordance with the present invention;
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FIG. 7 is a perspective view of another embodiment of an ablation catheter in
accordance with the present invention;
FIG. 7A is a pictorial representation of an alternative embodiment of an
ablation
catheter in accordance with the present invention;
FIG. 8A is a pictorial representation of a further embodiment of an ablation
catheter in accordance with the present invention shown in a first position;
FIG. 8B is a pictorial representation of the catheter of FIG. 8A shown in a
second position;
FIG. 8C is a pictorial representation of the catheter system of FIG. 8A shown
in
a a third position; and
FIG. 9 is a perspective view of another embodiment of an ablation catheter
system in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1-3 show an ablation catheter system 100 in accordance with the present
invention having an ablation element 102 that is deployable from a flexible
elongate
catheter or sheath 104. The catheter sheath 104 should be semi-rigid and
flexible so as
to be readily steerable to a desired location in a patient's body, such as
proximate the os
of a pulmonary vein. Such catheter delivery systems are well known to those of
ordinary skill in the art. In general, the deployed coil-like ablation element
102 has a
shape that includes one or more revolutions substantially oriented in a
transverse plane
106 (FIG. 4) that is orthogonal to a longitudinal axis 108 of the sheath 104.
This
geometry facilitates treating tissue about a circumference of a vessel, such
as a
pulmonary vein. The circumferential region of ablated tissue electrically
isolates tissue
on opposite sides of the ablated tissue. Thus, the atria, for example, can be
electrically
isolated from any arrhythmia-inducing foci within the pulmonary vein.
In one embodiment, the catheter system 100 includes a tubular inner member
110 for housing the ablation member 102 in the non-deployed position. In
general, it is
preferred that the inner member 102 be formed from an insulative material to
prevent
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unintended contact with tissue, for example. Exemplary materials for the
insulative
inner member 110 include Teflon and polyethylene.
The elongate ablation element 102 can have a variety of geometries that are
effective to form a generally annular lesion about a circumference of a vessel
wall.
Exemplary geometries include annular shapes having one or more revolutions,
crenulated, corrugated, and combinations thereof. It is understood that the
term
"revolution" should be construed broadly to include configurations of somewhat
less
than three hundred and sixty degrees. It is further understood that the
transverse plane
106 on which the revolutions of the elongate member are located provides a
general
frame of reference and that the elongate member can vary in distance from the
plane as
the elongate member forms a revolution.
In the exemplary embodiment of FIGS. 1-3, which shows the ablation member
102 in the deployed state, the ablation member 102 has a coil-like appearance
that
forms approximately one revolution generally oriented in the transverse plane
106 that
is substantially orthogonal to a longitudinal axis 108 of the sheath. This
configuration
is well-suited for contacting a vessel inner wall about its circumference or
for
contacting the posterior wall of the left atrium to circumscribe the os of a
pulmonary
vein. The resultant circumferential lesion on the atrial or vessel wall can be
effective to
isolate electrical impulses from the offending foci from passing to healthy
tissue on the
opposite side of the lesion.
FIG. 5 shows the catheter system 100' including an ablation member 102'
having an alternative, crenulated geometry. That is, the ablation member 102'
undulates so as to intersect the transverse plane 106' at defined intervals
along a
revolution. This configuration may inhibit or limit stenosis of the treated
vessel
proximate the circumferential lesion. The ablation member 102' can be partly
surrounded by an insulative coating 112.
In one embodiment, the ablation member 102 is formed from a conductive
elastic or superelastic shape memory material for ablating tissue with RF
energy.
Exemplary shape memory materials include nickel-titanium alloys, such as
Nitinol, and
copper based alloys. It is understood that shape memory materials, in general,
can be
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plastically deformed from a first shape at a relatively low temperature. Upon
heating
the material to some higher temperature, such as by resistive heating, the
material will
tend to return to the first shape. Such materials can have so-called one-way
and two-
way shape memories.
In further embodiments (not shown), the ablation member can be at least partly
surrounded by an insulative coating. The insulative coating can be disposed on
the
ablation member so as to form a plurality of discrete electrodes for ablating
tissue at
selected locations along the vessel circumference.
The ablation element can be deployed from the sheath using a variety of
mechanisms that are compatible with steerable catheter systems. Exemplary
mechanisms include predetermined shapes for the elongate member, manual
deployment mechanisms, and guide-wire based mechanisms.
FIG. 6 shows an ablation catheter system 200 having an ablation member 202
with a distal end 204 secured to a bulbous end 206 of a support member 208.
The
support member 208 is disposed within the sheath 210 and connected to an
actuator (not
shown) at a proximal end of the catheter. To deploy the ablation member 202,
the
support member 208 is longitudinally displaced with respect to the sheath such
that the
bulbous end 206 protrudes from the end 212 of the catheter. Upon exiting the
sheath
210, the ablation member 202 assumes a predetermined shape that includes about
one
revolution in a transverse plane 214 orthogonal to the sheath longitudinal
axis 216. The
ablation member 202 can extend from a retractable support wire 218.
In one embodiment, the bulbous end 206 of the support member is radiopaque to
facilitate determining the ablation member position on an external viewing
system, such
as an X-ray system.
Alternatively, the ablation member 202 can be wound on the support member
208 in the non-deployed state. The support member 208 can be rotated in a
predetermined direction such that the ablation member 202 is unwound or
released from
the support member. The support member 208 can be rotated until the ablation
member extends from the support member a desired distance. After ablation, the
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ablation member 202 can be retracted to the non-deployed state by rotating the
support
member in the opposite direction.
FIG. 7 shows an ablation catheter system 300 including a guide wire 302 for
manipulating a catheter 304 within the patient's body. It is understood that
the guide
wire 302 can be utilized in conjunction with mapping systems (which may be
separate
from or integral with the catheter system 300) to locate arrhythmic foci. The
catheter
304 includes a hatch 306 from which an ablation member 308 can be deployed.
Upon
actuating the hatch 306 to the open position, the ablation member 308
discharges from
the resultant opening 310 and assumes a predetermined configuration. It is
understood
that the predetermined annular shape will be effective to contact vessel walls
having a
circumference less than or equal to a predetermined value, which by way of
example,
may be in the range of about 0.4 centimeters to about 4.0 centimeters.
FIG. 7A shows an alternative embodiment of a catheter system 350 including an
ablation member 352 having an exposed proximal portion 354 for ablating tissue
and an
insulated distal portion 356 for centering the catheter within a pulmonary
vein 358.
The catheter system 350 is well suited for creating a circumferential lesion
on the
posterior left atrial wall 360 around the pulmonary vein os 362.
FIGS. 8A-C show a manually expandable ablation member 402 that forms a part
of a cardiac ablation catheter system 400 in accordance with the present
invention. The
system 400 includes a guide-wire based catheter 404 with an ablation member
406 that
is manually deployable from the catheter. In one embodiment, the ablation
member
406 is coupled to a semi-rigid support member 408 (FIG. 8C) that can be
rotated and/or
longitudinally displaced so as to deploy the ablation member 406. The size of
the loop
formed by the ablation member 406 can be selected by controlling the amount of
rotation/displacement of the support member 408. Alternatively, the leading
end of the
ablation element can be affixed to the guide wire. In one embodiment, the
ablating
element can be manipulated by rotating the guide wire.
FIG. 9 shows a further embodiment of a guide-wire based ablation catheter
system 500 having a manually deployable ablation member 502. This system is
similar
to the system 200 shown in FIG 6 with the addition of a guide wire 504 that
can
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provide additional stability during ablation. The catheter 506 is mounted on
the guide
wire 504 to facilitate advancement of the catheter into the pulmonary vein.
One skilled in the art will appreciate further features and advantages of the
invention based on the above-described embodiments. Accordingly, the invention
is
not to be limited by what has been particularly shown and described, except as
indicated by the appended claims. All publications and references cited herein
are
expressly incorporated herein by reference in their entirety.
What is claimed is:
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