U.S. patent application number 09/928033 was filed with the patent office on 2002-01-10 for loop structures for supporting diagnostic and therapeutic elements in contact with body tissue.
Invention is credited to Jenkins, Thomas R., Koblish, Josef V., Swanson, David K., Thompson, Russell B..
Application Number | 20020004631 09/928033 |
Document ID | / |
Family ID | 23775329 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020004631 |
Kind Code |
A1 |
Jenkins, Thomas R. ; et
al. |
January 10, 2002 |
Loop structures for supporting diagnostic and therapeutic elements
in contact with body tissue
Abstract
A probe that facilitates the creation of circumferential lesions
in body tissue. The probe includes a elongate body and a loop
structure that supports electrodes or other operative elements
against the body tissue.
Inventors: |
Jenkins, Thomas R.;
(Oakland, CA) ; Koblish, Josef V.; (Palo Alto,
CA) ; Thompson, Russell B.; (Los Altos, CA) ;
Swanson, David K.; (Mountain View, CA) |
Correspondence
Address: |
HENRICKS SLAVIN AND HOLMES LLP
SUITE 200
840 APOLLO STREET
EL SEGUNDO
CA
90245
|
Family ID: |
23775329 |
Appl. No.: |
09/928033 |
Filed: |
August 9, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09928033 |
Aug 9, 2001 |
|
|
|
09447183 |
Nov 22, 1999 |
|
|
|
Current U.S.
Class: |
600/374 ;
606/41 |
Current CPC
Class: |
A61B 2018/00214
20130101; A61B 2018/00148 20130101; A61B 2018/1467 20130101; A61B
2018/00375 20130101; A61B 2018/00065 20130101; A61B 2018/00821
20130101; A61B 2018/00113 20130101; A61B 2018/00797 20130101; A61B
2018/00077 20130101; A61B 18/1492 20130101 |
Class at
Publication: |
600/374 ;
606/41 |
International
Class: |
A61B 005/0408; A61B
018/14 |
Claims
We claim:
1. A probe, comprising: an elongate body defining a distal region,
a proximal region, a proximal end, a curved portion having a
pre-set curvature and a longitudinal axis; a control element
defining a distal portion associated with the distal region of the
elongate body and extending outwardly therefrom and proximally to
the proximal end of the elongate body; and at least one operative
element supported on the distal region.
2. A probe as claimed in claim 1, wherein the elongate body
comprises a catheter body.
3. A probe as claimed in claim 1, wherein the curved portion is
located within the proximal region.
4. A probe as claimed in claim 1, wherein the proximal region
includes a proximal member defining a first stiffness, the distal
region includes a distal member defining a second stiffness, and
the second stiffness is less than the first stiffness.
5. A probe as claimed in claim 1, wherein the at least one
operative element comprises a plurality of electrodes.
6. A probe as claimed in claim 1, wherein the elongate body defines
a control element aperture and the control element extends from the
distal region of the elongate body and into the control element
aperture.
7. A probe as claimed in claim 1, wherein the curved portion of the
elongate body defines an approximately ninety degree curvature.
8. A probe as claimed in claim 1, wherein the control element
comprises a first control element, the probe further comprising: a
second control element secured to a portion of the distal region of
the elongate body and extending proximally therefrom.
9. A probe as claimed in claim 8, wherein the first control element
defines a first stiffness, the second control element defines a
second stiffness, and the first stiffness is less than the second
stiffness.
10. A probe as claimed in claim 8, wherein the distal region
defines a middle area and the second control element is secured to
the middle area.
11. A probe as claimed in claim 1, wherein the curved portion of
the elongate body defines a curved portion plane, the distal region
comprises a loop defining a loop plane, and the loop plane is
arranged at a non-zero angle to the curved portion plane.
12. A probe as claimed in claim 11, wherein the loop plane is
substantially perpendicular to the curved portion plane.
13. A probe, comprising: an elongate body defining a distal region
and a proximal region, at least a portion of the distal region
having a substantially linear channel; and at least one temperature
sensor located in the substantially linear channel.
14. A probe as claimed in claim 13, wherein the at least one
temperature sensor comprises a plurality of axially spaced
temperature sensors.
15. A probe as claimed in claim 13, further comprising: at least
one operative element carried on the distal region of the elongate
body.
16. A probe as claimed in claim 15, wherein the at least one
operative element comprises an electrode.
17. A probe as claimed in claim 13, wherein the elongate body
defines a longitudinal axis and the substantially linear channel is
substantially c-shaped in a cross-section perpendicular to the
longitudinal axis.
18. A probe, comprising: an elongate body defining a distal region,
a proximal region, a proximal end, a distal end and a longitudinal
axis; a first control element defining a distal portion associated
with the distal region of the elongate body and extending outwardly
from the distal end and proximally to the proximal end of the
elongate body; a second control element extending proximally to the
proximal end of the elongate body, the second control element being
movably secured to the distal region of the elongate body; and at
least one operative element supported on the distal region.
19. A probe as claimed in claim 18, wherein the second control
element includes a collar slidably mounted on the distal region of
the elongate body.
20. A probe as claimed in claim 19, wherein the collar is
relatively soft.
21. A probe as claimed in claim 19, wherein the collar and distal
region of the elongate body are respectively constructed and
arranged such that the collar will be movable relative to the
distal region when the distal region is in a substantially linear
state and the collar will be substantially fixed relative to the
distal region when the distal region is in a curved state.
22. A probe as claimed in claim 18, wherein the elongate body
includes a curved portion having a preset curvature.
Description
BACKGROUND OF THE INVENTIONS
[0001] 1. Field of Inventions
[0002] The present invention relates generally to medical devices
that support one or more diagnostic or therapeutic elements in
contact with body tissue and, more particularly, to medical devices
that support one or more diagnostic or therapeutic elements in
contact with bodily orifices or the tissue surrounding such
orifices.
[0003] 2. Description of the Related Art
[0004] There are many instances where diagnostic and therapeutic
elements must be inserted into the body. One instance involves the
treatment of cardiac conditions such as atrial fibrillation and
atrial flutter which lead to an unpleasant, irregular heart beat,
called arrhythmia.
[0005] Normal sinus rhythm of the heart begins with the sinoatrial
node (or "SA node") generating an electrical impulse. The impulse
usually propagates uniformly across the right and left atria and
the atrial septum to the atrioventricular node (or "AV node"). This
propagation causes the atria to contract in an organized way to
transport blood from the atria to the ventricles, and to provide
timed stimulation of the ventricles. The AV node regulates the
propagation delay to the atrioventricular bundle (or "HIS" bundle).
This coordination of the electrical activity of the heart causes
atrial systole during ventricular diastole. This, in turn, improves
the mechanical function of the heart. Atrial fibrillation occurs
when anatomical obstacles in the heart disrupt the normally uniform
propagation of electrical impulses in the atria. These anatomical
obstacles (called "conduction blocks") can cause the electrical
impulse to degenerate into several circular wavelets that circulate
about the obstacles. These wavelets, called "reentry circuits,"
disrupt the normally uniform activation of the left and right
atria.
[0006] Because of a loss of atrioventricular synchrony, the people
who suffer from atrial fibrillation and flutter also suffer the
consequences of impaired hemodynamics and loss of cardiac
efficiency. They are also at greater risk of stroke and other
thromboembolic complications because of loss of effective
contraction and atrial stasis.
[0007] One surgical method of treating atrial fibrillation by
interrupting pathways for reentry circuits is the so-called "maze
procedure" which relies on a prescribed pattern of incisions to
anatomically create a convoluted path, or maze, for electrical
propagation within the left and right atria. The incisions direct
the electrical impulse from the SA node along a specified route
through all regions of both atria, causing uniform contraction
required for normal atrial transport function. The incisions
finally direct the impulse to the AV node to activate the
ventricles, restoring normal atrioventricular synchrony. The
incisions are also carefully placed to interrupt the conduction
routes of the most common reentry circuits. The maze procedure has
been found very effective in curing atrial fibrillation. However,
the maze procedure is technically difficult to do. It also requires
open heart surgery and is very expensive.
[0008] Maze-like procedures have also been developed utilizing
catheters which can form lesions on the endocardium (the lesions
being 1 to 15 cm in length and of varying shape) to effectively
create a maze for electrical conduction in a predetermined path.
The formation of these lesions by soft tissue coagulation (also
referred to as "ablation") can provide the same therapeutic
benefits that the complex incision patterns that the surgical maze
procedure presently provides, but without invasive, open heart
surgery.
[0009] Catheters used to create lesions typically include a
relatively long and relatively flexible body portion that has a
soft tissue coagulation electrode on its distal end and/or a series
of spaced tissue coagulation electrodes near the distal end. The
portion of the catheter body portion that is inserted into the
patient is typically from 23 to 55 inches in length and there may
be another 8 to 15 inches, including a handle, outside the patient.
The length and flexibility of the catheter body allow the catheter
to be inserted into a main vein or artery (typically the femoral
artery), directed into the interior of the heart, and then
manipulated such that the coagulation electrode contacts the tissue
that is to be ablated. Fluoroscopic imaging is used to provide the
physician with a visual indication of the location of the
catheter.
[0010] In some instances, the proximal end of the catheter body is
connected to a handle that includes steering controls. Exemplary
catheters of this type are disclosed in U.S. Pat. No. 5,582,609. In
other instances, the catheter body is inserted into the patient
through a sheath and the distal portion of the catheter is bent
into loop that extends outwardly from the sheath. This may be
accomplished by pivotably securing the distal end of the catheter
to the distal end of the sheath, as is illustrated in co-pending
U.S. application Ser. No. 08/769,856, filed Dec. 19, 1996, and
entitled "Loop Structures for Supporting Multiple Electrode
Elements." The loop is formed as the catheter is pushed in the
distal direction. The loop may also be formed by securing a pull
wire to the distal end of the catheter that extends back through
the sheath, as is illustrated in co-pending U.S. application Ser.
No. 08/960,902, filed Oct. 30, 1997, and entitled, "Catheter Distal
Assembly With Pull Wires," which is incorporated herein by
reference. Loop catheters are advantageous in that they tend to
conform to different tissue contours and geometries and provide
intimate contact between the spaced tissue coagulation electrodes
(or other diagnostic or therapeutic elements) and the tissue.
[0011] One lesion that has proven to be difficult to form with
conventional devices is the circumferential lesion that is used to
isolate the pulmonary vein and cure ectopic atrial fibrillation.
Lesions that isolate the pulmonary vein may be formed within the
pulmonary vein itself or in the tissue surrounding the pulmonary
vein. Conventional steerable catheters and loop catheters have
proven to be less than effective with respect to the formation of
such circumferential lesions. Specifically, it is difficult to form
an effective circumferential lesion by forming a pattern of
relatively small diameter lesions. More recently, inflatable
balloon-like devices that can be expanded within or adjacent to the
pulmonary vein have been introduced. Although the balloon-like
devices are generally useful for creating circumferential lesions,
the inventors herein have determined that these devices have the
undesirable effect of occluding blood flow through the pulmonary
vein.
[0012] Accordingly, the inventors herein have determined that a
need exists generally for structures that can be used to create
circumferential lesions within or around bodily orifices without
occluding fluid flow and, in the context of the treatment of atrial
fibrillation, within or around the pulmonary vein without occluding
blood flow.
SUMMARY OF THE INVENTION
[0013] Accordingly, the general object of the present inventions is
to provide a device that avoids, for practical purposes, the
aforementioned problems. In particular, one object of the present
inventions is to provide a device that can be used to create
circumferential lesions in or around the pulmonary vein and other
bodily orifices in a more efficient manner than conventional
apparatus. Another object of the present invention is to provide a
device that can be used to create circumferential lesions in or
around the pulmonary vein and other bodily orifices without
occluding blood or other bodily fluid flow.
[0014] In order to accomplish some of these and other objectives, a
probe in accordance with one embodiment of a present invention
includes an elongate body and a helical structure associated with
the distal region of the elongate body. In one preferred
implementation, a plurality of spaced electrodes are carried by the
helical structure. Such a probe provides a number of advantages
over conventional apparatus. For example, the helical structure can
be readily positioned with the body such that a ring of electrodes
is brought into contact with the tissue in or around the pulmonary
or other bodily orifice. The helical structure also defines an
opening that allows blood or other bodily fluids to pass
therethrough. As a result, the present probe facilitates the
formation of a circumferential lesion without the difficulties and
occlusion of blood or other fluids that is associated with
conventional apparatus.
[0015] In order to accomplish some of these and other objectives, a
probe in accordance with one embodiment of a present invention
includes an elongate body, a loop structure associated with the
distal region of the elongate body, and an anchor member associated
with the distal region of the elongate body and located distally of
the loop structure. In one preferred implementation, a plurality of
spaced electrodes are carried by the loop structure. Such a probe
provides a number of advantages over conventional apparatus. For
example, the anchor member may be positioned within a bodily
orifice, such as the pulmonary vein, thereby centering the loop
structure relative to the orifice. This allows a circumferential
lesion to be created in or around the pulmonary vein or other
orifice without the aforementioned difficulties associated with
conventional apparatus.
[0016] In order to accomplish some of these and other objectives, a
probe in accordance with one embodiment of a present invention
includes an elongate body defining a curved portion having a
pre-set curvature and a control element defining a distal portion
associated with the distal region of the elongate body and
extending outwardly therefrom and proximally to the proximal end of
the elongate body. In one preferred implementation, a plurality of
spaced electrodes are carried by the distal region of the elongate
body. Such a probe provides a number of advantages over
conventional apparatus. For example, the control element may be
used to pull the distal region of the elongate body into a loop in
conventional fashion. Unlike conventional apparatus, however, the
pre-set curvature of the curved portion may be such that it orients
the loop in such a manner that it can be easily positioned in or
around the pulmonary vein or other bodily orifice so that a
circumferential lesion can be easily formed.
[0017] The above described and many other features and attendant
advantages of the present inventions will become apparent as the
inventions become better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Detailed description of preferred embodiments of the
inventions will be made with reference to the accompanying
drawings.
[0019] FIG. 1 is a side view of a probe in a relaxed state in
accordance with a preferred embodiment of a present invention.
[0020] FIG. 2 is a section view taken along line 2-2 in FIG. 1.
[0021] FIG. 3 is a side view of the probe illustrated in FIG. 1
with the stylet extended.
[0022] FIG. 4 is a side view of the probe illustrated in FIG. 1
with the stylet retracted.
[0023] FIG. 5a is an end view of the probe illustrated in FIG.
4.
[0024] FIG. 5b is a section view taken along line 5b-5b in FIG.
5a.
[0025] FIG. 6 is a side view of the probe illustrated in FIG. 1 in
an expanded state.
[0026] FIG. 7 is an end view of the probe illustrated in FIG.
6.
[0027] FIG. 8 is a perspective, cutaway view of a probe handle in
accordance with a preferred embodiment of a present invention.
[0028] FIG. 9 is a perspective view of a portion of the probe
handle illustrated in FIG. 8.
[0029] FIG. 10 is an exploded view of the portion of the probe
handle illustrated in FIG. 9.
[0030] FIG. 11 is a partial section view taken along line 11-11 in
FIG. 9.
[0031] FIG. 12 is a partial section view of the knob and spool
arrangement in the probe handle illustrated in FIG. 8.
[0032] FIG. 13 is a perspective view of a probe handle in
accordance with a preferred embodiment of a present invention.
[0033] FIG. 14 is an exploded view of the probe handle illustrated
in FIG. 13.
[0034] FIG. 15 is a partial section view taken along line 15-15 in
FIG. 13.
[0035] FIG. 16 is a side view of a probe in accordance with a
preferred embodiment of a present invention.
[0036] FIG. 16a is a side view of a probe in accordance with a
preferred embodiment of a present invention.
[0037] FIG. 16b is a section view taken alone line 16a-16b in FIG.
16a.
[0038] FIG. 16c is a perspective view of the probe illustrated in
FIG. 16a in a helical orientation.
[0039] FIG. 17 is a plan view of a probe in accordance with a
preferred embodiment of a present invention.
[0040] FIG. 18 is a section view of the distal portion of the probe
illustrated in FIG. 17.
[0041] FIG. 19 is a side, partial section view showing the probe
illustrated in FIG. 17 within a sheath.
[0042] FIG. 20 is a perspective view of the probe illustrated in
FIG. 17 with the loop reoriented.
[0043] FIG. 21 is a side view of the probe illustrated in FIG.
20.
[0044] FIG. 22 is a perspective view of a probe in accordance with
a preferred embodiment of a present invention.
[0045] FIG. 23 is a side view of the probe illustrated in FIG.
22.
[0046] FIG. 24 is an end view of the probe illustrated in FIG.
22.
[0047] FIG. 25 is a side view of the probe illustrated in FIG. 22
being used in combination with a sheath and a guidewire.
[0048] FIG. 26 is an end view of a probe similar to that
illustrated in FIGS. 22-24 with a generally elliptical loop.
[0049] FIG. 27 is a side, partial section view showing a probe in
accordance with a preferred embodiment of a present invention.
[0050] FIG. 28 is a perspective view of the probe illustrated in
FIG. 27 with the loop reoriented.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] The following is a detailed description of the best
presently known modes of carrying out the inventions. This
description is not to be taken in a limiting sense, but is made
merely for the purpose of illustrating the general principles of
the inventions.
[0052] The detailed description of the preferred embodiments is
organized as follows:
[0053] I. Introduction
[0054] II. Helical Loop Structures
[0055] III. Other Loop Structures
[0056] IV. Electrodes, Temperature Sensing and Power Control
[0057] The section titles and overall organization of the present
detailed description are for the purpose of convenience only and
are not intended to limit the present inventions.
[0058] I. Introduction
[0059] The present inventions may be used within body lumens,
chambers or cavities for diagnostic or therapeutic purposes in
those instances where access to interior bodily regions is obtained
through, for example, the vascular system or alimentary canal and
without complex invasive surgical procedures. For example, the
inventions herein have application in the diagnosis and treatment
of arrhythmia conditions within the heart. The inventions herein
also have application in the diagnosis or treatment of ailments of
the gastrointestinal tract, prostrate, brain, gall bladder, uterus,
and other regions of the body.
[0060] With regard to the treatment of conditions within the heart,
the present inventions are designed to produce intimate tissue
contact with target substrates associated with various arrhythmias,
namely atrial fibrillation, atrial flutter, and ventricular
tachycardia. For example, the distal portion of a catheter in
accordance with a present invention, which may include diagnostic
and/or soft tissue coagulation electrodes, can be used to create
lesions within or around the pulmonary vein to treat ectopic atrial
fibrillation.
[0061] The structures are also adaptable for use with probes other
than catheter-based probes. For example, the structures disclosed
herein may be used in conjunction with hand held surgical devices
(or "surgical probes"). The distal end of a surgical probe may be
placed directly in contact with the targeted tissue area by a
physician during a surgical procedure, such as open heart surgery.
Here, access may be obtained by way of a thoracotomy, median
sternotomy, or thoracostomy. Exemplary surgical probes are
disclosed in co-pending U.S. application Ser. No. 09/072,872, filed
May 5, 1998, and entitled "Surgical Methods and Apparatus for
Positioning a Diagnostic or Therapeutic Element Within the
Body."
[0062] Surgical probe devices in accordance with the present
inventions preferably include a handle, a relatively short shaft,
and one of the distal assemblies described hereafter in the
catheter context. Preferably, the length of the shaft is about 4
inches to about 18 inches. This is relatively short in comparison
to the portion of a catheter body that is inserted into the patient
(typically from 23 to 55 inches in length) and the additional body
portion that remains outside the patient. The shaft is also
relatively stiff. In other words, the shaft is either rigid,
malleable, or somewhat flexible. A rigid shaft cannot be bent. A
malleable shaft is a shaft that can be readily bent by the
physician to a desired shape, without springing back when released,
so that it will remain in that shape during the surgical procedure.
Thus, the stiffness of a malleable shaft must be low enough to
allow the shaft to be bent, but high enough to resist bending when
the forces associated with a surgical procedure are applied to the
shaft. A somewhat flexible shaft will bend and spring back when
released. However, the force required to bend the shaft must be
substantial.
[0063] II. Helical Loop Structures
[0064] As illustrated for example in FIGS. 1-7, a catheter 10 in
accordance with a preferred embodiment of a present invention
includes a hollow, flexible catheter body 12 that is preferably
formed from two tubular parts, or members. The proximal member 14
is relatively long and is attached to a handle (discussed below
with reference to FIGS. 8-15), while the distal member 16, which is
relatively short, carries a plurality of spaced electrodes 18 or
other operative elements. The proximal member 14 is typically
formed from a biocompatible thermoplastic material, such as a
Pebax.RTM. material (polyether block emide) and stainless steel
braid composite, which has good torque transmission properties. In
some implementations, an elongate guide coil (not shown) may also
be provided within the proximal member 14. The distal member 16 is
typically formed from a softer, more flexible biocompatible
thermoplastic material such as unbraided Pebax.RTM. material,
polyethylene, or polyurethane. The proximal and distal members,
which are about 5 French to about 9 French in diameter, are
preferably either bonded together with an overlapping thermal bond
or adhesively bonded together end to end over a sleeve in what is
referred to as a "butt bond."
[0065] At least a portion of the distal member 16 has a generally
helical shape. The number of revolutions, length, diameter and
shape of the helical portion will vary from application to
application. The helical portion of the distal member 16 in the
embodiment illustrated in FIGS. 1-7, which may be used to create
lesions in or around the pulmonary vein, revolves around the
longitudinal axis of the catheter 10 one and one-half times in its
relaxed state. The diameter of the helical portion can be
substantially constant over its length. The diameter may,
alternatively, vary over the length of the helical portion. For
example, the helical portion could have a generally frusto-conical
shape where the diameter decreases in the distal direction.
[0066] The helical shape of the exemplary distal member 16 may be
achieved through the use of a center support 20 (FIG. 2) that is
positioned inside of and passes within the length of the distal
member. The center support 20 is preferably a rectangular wire
formed from resilient inert wire, such as Nickel Titanium
(commercially available under the trade name Nitinol.RTM.) or 17-7
stainless steel wire, with a portion thereof heat set into the
desired helical configuration. The thickness of the rectangular
center support 20 is preferably between about 0.010 inch and about
0.015 inch. Resilient injection molded plastic can also be used.
Although other cross sectional configurations can be used, such as
a round wire, a rectangular cross section arranged such that the
longer edge extends in the longitudinal direction is preferred for
at least the helical portion. Such an orientation reduces the
amount of torsional force, as compared to a round wire, required to
unwind the helical portion into an expanded configuration and
collapse the helical portion into a circular structure in the
manner described below. The preferred orientation of the center
support 20 also increases the stiffness of the helical portion in
the longitudinal direction, which allows the physician to firmly
press the present structure against tissue. The center support 20
is also preferably housed in an insulative tube 21 formed from
material such as Teflon.TM. or polyester.
[0067] In the illustrated embodiment, the proximal end of the
helical center support 20 is secured to a C-shaped crimp sleeve
(not shown) that is located where the proximal and distal members
14 and 16 are bonded to one another and is mounted on a guide coil
(not shown) which extends through the proximal member 14 to the
distal end thereof. The distal end of the guide coil is located in
the area where the proximal and distal members 14 and 16 are bonded
to one another. This bond also anchors the proximal end of the
center support 20 to the distal end of the proximal member 14. The
distal end of the center support 20 is secured to a tip member 22
which is in turn secured to the distal end of the distal member 16
with adhesive. Additional details concerning the placement of a
center support within the distal member of a catheter can be found
in commonly assigned U.S. patent application Ser. No. 09/150,833,
entitled "Catheter Having Improved Torque Transmission Capability
and Method of Making the Same," which is incorporated herein by
reference.
[0068] The exemplary catheter 10 also includes a stylet 24 that
enables the physician to manipulate the helical portion of the
distal member 16 and adjust its shape from the at rest shape
illustrated in FIG. 1. For example, the stylet 24 can be moved
distally to deform the helical portion of the distal member 16 in
the manner illustrated in FIG. 3 or proximally to deform the
helical portion in the manner illustrated in FIGS. 4-5b. The
physician can also rotate the stylet 24 in one direction, which
will cause the helical portion of the distal member 16 to unwind
and so that its diameter increases, as illustrated in FIGS. 6 and
7, or rotate the stylet in the other direction to cause the distal
member to wind up and its diameter to decrease.
[0069] In any of these states, the helical portion will define an
open area interior to the electrodes 18 through which blood or
other bodily fluids can flow. As a result, the helical portion can
be used to create a circumferential lesion in or around the
pulmonary vein, or other bodily orifice, without occluding fluid
flow.
[0070] The stylet 24, which is preferably formed from inert wire
such as Nitinol.RTM. or 17-7 stainless steel wire and should be
stiffer than the center support 20, extends through the catheter
body 12 from the proximal end of the proximal member 14 to the
distal end of the distal member 16. There, it may be secured to
either distal end of the center support 20 or to the tip member 22.
The stylet 24 is located within the catheter body 12 except in the
area of the helical portion of the distal member 16. Here,
apertures 26 and 28 are provided for ingress and egress. In order
to insure that the stylet 24 moves smoothly through the catheter
body 12, the stylet is located within a lubricated guide coil 30
(FIG. 2) in the preferred embodiment.
[0071] The exemplary catheter 10 illustrated in FIGS. 1-7 is not a
steerable catheter and, accordingly, may be advanced though a
conventional steerable guide sheath 32 to the target location. The
sheath 32 should be lubricious to reduce friction during movement
of the catheter 10. With respect to materials, the proximal portion
of the sheath 14 is preferably a Pebax.RTM. and stainless steel
braid composite and the distal portion is a more flexible material,
such as unbraided Pebax.RTM., for steering purposes. The sheath
should also be stiffer than the catheter 12. Prior to advancing the
catheter 10 into the sheath 32, the stylet 24 will be moved to and
held in its distal most position (i.e. beyond the position
illustrated in FIG. 3) in order to straighten out the helical
portion of the distal member 16. The stylet 24 will remain in this
position until the helical portion of the distal member 16 is
advanced beyond the distal end of the sheath 32. A sheath
introducer, such as those used in combination with basket
catheters, may be used when introducing the distal member 16 into
the sheath 32.
[0072] As illustrated for example in FIGS. 1, 3, 4 and 6, the
exemplary catheter 10 may also include an anchor member 34 which
allows the catheter to be precisely located relative to the
pulmonary vein (or other orifice). More specifically, advancing the
anchor member 34 into the pulmonary vein aligns the helical portion
of the distal member 16 with the pulmonary vein. The physician can
then manipulate the stylet 24 to bring the helical portion of the
distal member 16 into the desired configuration and press the
distal member (and electrodes 18) firmly against the region of
tissue surrounding the pulmonary vein to create a circumferential
lesion around the pulmonary vein. Alternatively, the physician can
advance the helical portion of the distal member 16 into the
pulmonary vein and thereafter manipulate the stylet 24 so that the
helical portion expands and brings the electrodes 18 into contact
with the interior of the pulmonary vein so that a circumferential
lesion can be created within the vein. In the illustrated
embodiment, the anchor member 34 is simply the portion of the
distal member 16 that is distal to the helical portion.
Alternatively, a separate structure may be secured to the distal
end of the distal member 16. The exemplary anchor member 34 is
approximately 1 to 2 inches in length, although other lengths may
be used to suit particular applications.
[0073] The exemplary catheter 10 illustrated in FIGS. 1-7 should be
used in conjunction with a handle that allows the physician to move
the stylet 24 proximally and distally relative to the catheter body
12 and also allows the physician to rotate the stylet relative to
the catheter body. One example of such a handle, which is generally
represented by reference numeral 38, is illustrated in FIGS. 8-12.
The handle 38 includes distal member 40, a rotatable knob 42 that
is connected to the stylet 24 and a rotatable end cap 44 that is
connected to the catheter body 12 through the use of a tip member
45. Specifically, the catheter body 12 is bonded to the tip member
45 which is in turn bonded to the rotatable end cap 44. The handle
also includes a transition piece 46 that is used to secure the
distal member 40 to a proximal member 48 (FIG. 11). The proximal
end of the proximal member 48 includes a port (not shown) that
receives an electrical connector from a power supply and control
device. Alternatively, the distal and proximal members 40 and 48
may be combined into a unitary structure having a shape that is
either the same as or is different than the illustrated shape of
the combined distal and proximal members.
[0074] Turning first to the proximal and distal actuation of the
stylet 24, the proximal portion of the stylet and lubricated guide
coil 30 extend through the catheter body 12 and into the handle 38,
as illustrated in FIG. 11. The lubricated guide coil 30 is secured
to a seat 50 within the distal member 40. A stylet guide 52 that
includes a guide slot 54 is secured within the distal member 40.
The stylet guide 52 is preferably formed from a lubricious material
such as acetal, which is sold under the trade name Delrin.RTM.. The
stylet 24 passed through the guide slot 54 and is anchored to a
threaded spool 56 that is secured to, and is preferably integral
with, the rotatable knob 42. The rotatable knob and spool are
secured to the proximal member 40 with a cap screw and nut
arrangement or the like that extends through aperture 57 (FIG. 12).
The threads on the spool 56 act as guides to control the manner in
which the stylet 24 winds onto and unwinds from the spool.
Anchoring is accomplished in the illustrated embodiment by
inserting the stylet 24 into an anchoring aperture 58 and securing
the stylet within the aperture with a set screw (not shown) that is
inserted into a set screw aperture 60.
[0075] Proximal rotation of the knob 42 and threaded spool 56, i.e.
rotation in the direction of arrow P in FIG. 9, will cause the
stylet 24 to move proximally and wind onto the threaded spool. As
this occurs, the stylet 24 will travel within the guide slot 54
towards the knob 42 in the direction of the arrow in FIG. 11.
Distal rotation of the knob 42 on the other hand, i.e. rotation in
the direction of arrow D in FIG. 9, will cause the stylet 24 to
move distally, unwind from the threaded spool 56 and travel away
from the knob within the guide slot 54.
[0076] In the preferred embodiment illustrated in FIGS. 8-12, the
stylet 24 can be rotated relative to the catheter body 12 because
the stylet is anchored with the handle distal member 40, while the
catheter body is secured to the end cap 44 that is free to rotate
relative to the distal member. Referring more specifically to FIGS.
10 and 11, the rotatable end cap 44 is mounted on an end cap
support member 66. A set screw (not shown) engages a longitudinally
extending slot 68 formed in the support member 66 and holds it in
place within the distal member 40. The distal portion of the
support member 66 includes a circumferentially extending slot 70. A
series of set screws 72, which have a diameter that is
substantially equal to the width of the slot 70, pass through the
end cap 44 into the slot. This arrangement allows the end cap 44 to
rotate relative to the support member 66 and, therefore, rotate
relative to the handle distal member 40. The proximal end of the
end cap support member 66 includes a relief surface 74 that
prevents unnecessary stress on the stylet 24 as it travels back and
forth within the guide slot 54.
[0077] To rotate the stylet 24 relative to the catheter body 12,
the physician may hold the end cap 44 in place and rotate the
handle distal member 40 relative to the end cap. When such rotation
occurs, the stylet 24 will rotate within the catheter body 12. The
catheter body 12, on the other hand, will be held in place by
virtue of its connection to the end cap 40. As a result, the stylet
24 can be used to apply torsional forces to the helical portion of
the proximal member 16 to move the helical portion between the
various states illustrated in FIGS. 1, 4, and 6.
[0078] Another handle that may be used in conjunction with the
exemplary catheter 10 is illustrated for example in FIGS. 13-15.
Exemplary handle 76 includes a main body 78 and a stylet control
device 80 that can be used to move the stylet 24 proximally and
distally and that can also be used to rotate the stylet relative to
the catheter body 12. The stylet control device 80 consists
essentially of a housing 82, a rotatable threaded spool 84 and knob
86 arrangement, and a housing support member 88 that supports the
housing such that the housing may be rotated relative to the main
body 78.
[0079] The exemplary housing 82 is composed of two housing members
90 and 92 which fit together in the manner illustrated in FIG. 14.
A stylet guide 94, which includes a guide slot 96, is located
within the housing 82. The stylet guide 94 is secured in place and
prevented from rotating relative to the housing 82 with a set screw
(not shown) that rests within a positioning slot 98 after being
inserted though an aperture 100 in the housing. The stylet 24
passes through the guide slot 96 and, in a manner similar to that
described above with reference to FIGS. 8-12, is anchored in an
anchoring aperture 102. The stylet 24 is secured within the
anchoring aperture 102 with a set screw (not shown) that is
inserted into a set screw aperture 104. Here too, proximal rotation
of the knob 86 (arrow P in FIG. 13) will cause the stylet 24 to
wind onto the threaded spool 84, thereby pulling the stylet
proximally, while distal rotation (arrow D in FIG. 13) will cause
the stylet to unwind from the spool and move distally.
[0080] In the preferred embodiment illustrated in FIGS. 13-15, the
housing 82 includes a post 106 that may be inserted into the
housing support member 88, which is itself fixedly secured to the
handle main body 78. A circumferentially extending slot 108 is
formed in one end of the post 106. In a manner similar to the end
cap 44 illustrated in FIGS. 8-12, the post 106 may be secured to
the housing support member 88 by inserting a series of set screws
110 though a corresponding series of support member apertures and
into the slot 108. As described in greater detail below with
reference to FIG. 15, the catheter body 12 is fixedly secured to
the handle main body 78. Thus, rotation of the housing 82 relative
to the housing support member 88 and, therefore, the main body 78
will cause the stylet 24 to rotate relative to the catheter body
12. Upon such rotation, the stylet 24 will apply torsional forces
to the helical portion of the proximal member 16, thereby causing
it to move between the states illustrated in FIGS. 1, 4, and 6.
[0081] As illustrated for example in FIG. 14, the exemplary handle
main body 78 is a multi-part assembly consisting of handle members
112 and 114, a base member 116 and a strain relief element 118.
Handle member 114 includes a series of fasteners 120a-c which mate
with corresponding fasteners (not shown) on the handle member 112.
Handle member 114 also includes a wire guide 122 which is used to
centralize the electrical wires. A cutout 124 is formed at the
proximal end of the handle member 114 and a similar cutout (not
shown) is formed in the handle member 112. The cutouts together
form an opening for an electrical connector from a power supply and
control device. The base member 116 includes an aperture 126 for
seating the housing support member 88 and a cylindrical post 128 on
which the strain relief element 118 is fixedly mounted.
[0082] The catheter body 12 may be inserted into and bonded to the
base member 116 in the manner illustrated for example in FIG. 15.
Thus, the catheter body 12 is fixed relative to the handle 76. The
guide coil 30 is secured within a guide coil seat 130 and the
stylet 24 extends through the guide coil seat and into the housing
support member 88 in the manner shown.
[0083] Like the catheter illustrated in FIGS. 1-7, the helical
catheter 132 illustrated in FIG. 16 includes a catheter body 12
having a proximal member 14 and a distal member 16 with a helical
portion, a plurality of electrodes 18, and an anchor member 34. The
catheter illustrated in FIG. 16 does not, however, include a stylet
24. In order to compensate for the decrease in manipulability
associated with the lack of a stylet, the center support may be
formed from material such as actuator-type Nitinol.RTM. (discussed
in detail below) which has shape memory properties that are
activated at a temperature higher than body temperature. The shape
memory properties allow the physician to, for example, cause the
helical portion of the distal member 16 to expand from the state
illustrated in FIGS. 4-5b (albeit with respect to catheter 10) to
the state illustrated in FIGS. 6 and 7 by energizing the electrodes
18.
[0084] The helical portion of the distal member 16 in the catheter
132 should be flexible enough that the helical portion will deflect
and straighten out when pushed or pulled into the sheath, yet
resilient enough that it will return to its helical shape when
removed from the sheath. In addition, the proximal and distal end
of the helical portion should be oriented at an angle relative to
the longitudinal axis of the catheter 36 (preferably about 45
degrees) that facilitates a smooth transition as the distal member
16 is pushed or pulled into the sheath 32. Also, because the
catheter 132 lacks the stylet 24, it may be used in conjunction
with any conventional catheter handle.
[0085] A guidewire may be used in conjunction with the catheters
illustrated in FIGS. 1-16 to position the sheath 32 in the manner
described below with reference to FIG. 25.
[0086] Another exemplary catheter that relies on materials which
have shape memory properties activated at high temperatures is
illustrated in FIGS. 16a-16c. Exemplary catheter 133, which is a
non-steerable catheter that may be inserted into a patient over a
guidewire 135, includes a catheter body 12' having a proximal
member 14' and a distal member 16', a plurality of electrodes 18,
and an anchor member 34. The catheter 133 also includes a shape
memory core wire 137 that is friction fit within the distal member
16' and heat set into a helical configuration. The core wire 137 is
relatively flexible at body temperature. As such, a stylet 24 may
be used to maintain the core wire 137 and electrode supporting
distal member 16' in the linear state illustrated in FIG. 16a.
[0087] The core wire 137 and distal member 16' may be driven to the
helical state illustrated in FIG. 16c by heating the core wire 137.
Resistive heating is the preferred method of heating the core wire
137. To that end, electrical leads 139 (only one shown) are
connected to the ends of the core wire 137 and supply current to
the core wire. The stylet 24 and guidewire 135 should be pulled in
the proximal direction beyond the distal member 16' prior to
heating the core wire 137.
[0088] A suitable material for the core wire 137 is a shape memory
alloy such as actuator-type Nitinol.RTM.. Such material has a
transition temperature above body temperature (typically between
about 550.degree. C. and 70.degree. C.). When the material is
heated to the transition temperature, the internal structure of the
material dynamically changes, thereby causing the material to
contract and assume its heat set shape. Additional information
concerning shape memory alloys is provided in T. W. Duerig et al.,
"Actuator and Work Production Devices," Engineering Aspects of
Shape Memory Alloys, pp. 181-194 (1990).
[0089] The exemplary catheter body 12' is substantially similar to
the catheter body 12 described above. However, as illustrated in
FIG. 16b, the exemplary catheter body 12' includes five lumens--a
central lumen 141 and four outer lumens 143. The guidewire 135
passes through the central lumen 141. The core wire 137 and
conductor 139 are located within one of the outer lumens 143 and
the stylet 24 is located in another outer lumen. The other two
outer lumens 143 respectively house electrode wires 168 and
temperature sensor wires 174 (discussed in Section IV below). Of
course, other catheter body configurations, such as a three outer
lumen configuration in which the electrode and temperature sensor
wires are located in the same lumen, may be employed.
[0090] The exemplary catheter 133 illustrated in FIGS. 16a-16c also
includes a pair of radiopaque markers 145 and 147 that may be used
to properly position the helical portion of the catheter. More
specifically, because the core wire 137 contracts equally in the
distal and proximal directions, the catheter 133 should be
positioned such that the target tissue area is located at about the
mid-point between the radiopaque markers 145 and 147 prior to
actuating the core wire 137. To form a lesion within the pulmonary
vein, for example, the anchor member 34 may be inserted into the
pulmonary vein to such an extent that the mid-point between the
radiopaque markers 145 and 147 is located at the target site within
the vein. Actuation of the core wire 137 will cause the electrode
supporting distal member 16' to assume the helical shape
illustrated in FIG. 16c and press against the vein so as to achieve
a suitable level of tissue contact.
[0091] Once the lesion has been formed, the core wire 137 may be
deactivated and the stylet 24 may be moved back into the distal
member 16' to return the distal member to the linear state
illustrated in FIG. 16a. A diagnostic catheter (not shown) may then
be advanced through the central lumen 141 to map the vein and
insure that a curative lesion has been formed.
[0092] III. Other Loop Catheters
[0093] A loop catheter 134 in accordance with a preferred
embodiment of another present invention is illustrated in FIGS.
17-21. The loop catheter 134 includes a hollow, flexible catheter
body 136 that is preferably formed from two tubular parts, or
members. The proximal member 138 is relatively long and is attached
to a handle, while the distal member 140, which is relatively
short, carries a plurality of spaced electrodes 18 or other
operative elements. The proximal member 138 is typically formed
from a biocompatible thermoplastic material, such as a Pebax.RTM.
material (polyether block emide) and stainless steel braid
composite, which has good torque transmission properties and, in
some implementations, an elongate guide coil (not shown) may also
be provided within the proximal member. The distal member 140 is
typically formed from a softer, more flexible biocompatible
thermoplastic material such as unbraided Pebax.RTM. material,
polyethylene, or polyurethane. The proximal and distal members are
preferably either bonded together with an overlapping thermal bond
or adhesive bonded together end to end over a sleeve in what is
referred to as a "butt bond."
[0094] The distal portion of the proximal member 138 includes a
pre-shaped curved portion (or elbow) 142. Although other curvatures
may be used, the curved portion 142 in the illustrated embodiment
is a ninety degree curve with a radius of about 0.5 inch. The
preset curvature may be accomplished in a variety of manners.
Preferably, the curved portion 142 is preset through the use of a
thermal forming technique (100.degree. C. for 1 hour). The preset
curved portion 142 in the illustrated embodiment results in a loop
that is in plane with the remainder of the catheter 134. However,
as discussed below with reference to FIGS. 22-24, curvatures that
result in an out-of-plane loop may also be employed.
[0095] The preset curvature may also be accomplished through the
use of a pre-shaped spring member (not shown) formed from
Nitinol.RTM. or 17-7 stainless steel that is positioned within the
proximal member 138 and anchored where the proximal and distal
members 138 and 140 are bonded to one another. Such a spring member
would preferably be rectangular in cross-section and have a nominal
radius of about 0.5 inch. Another alternative would be to adjust
the location of the proximal member/distal member bond and use the
center support 150 (discussed below) to provide the preset
curvature.
[0096] The exemplary catheter 134 illustrated in FIGS. 17-21 also
includes a pull wire 144. The pull wire 144 is preferably a
flexible, inert cable constructed from strands of metal wire
material, such as Nitinol.RTM. or 17-7 stainless steel, that is
about 0.012 inch to about 0.025 inch in diameter. Alternatively,
the pull wire 144 may be formed from a flexible, inert stranded or
molded plastic material. The pull wire 144 is also preferably round
in cross-section, although other cross-sectional configurations can
be used.
[0097] As illustrated for example in FIG. 18, the pull wire 144 in
the exemplary embodiment extends into an opening 146 in a tip
member 148 and is secured to a center support 150 with a stainless
steel crimp tube 152. More specifically, the pull wire 144 passes
through a bore 154 in the distal end 156 of the crimp tube 152 and
abuts the center support 150. The in-line connection of the center
support 150 and pull wire 144 allows for a reduction in the overall
diameter of distal portion of the catheter body 136. The tip member
148 is preferably formed from platinum and is fixedly engaged with,
for example, silver solder, adhesive or spot welding, to the distal
end 156 of crimp tube 152. The center support may be electrically
insulated with a thin walled polyester heat shrink tube 158 that
extends beyond the proximal end of the crimp tube 152. The pull
wire 144 extends proximally from the tip member 148 and preferably
back into the catheter body 136 through an aperture 158 to the
proximal end of the catheter body. Alternatively, the pull wire can
simply be run proximally within the interior of the sheath 32 along
the exterior of the catheter body 136. Other pull wire
configurations, other methods of attaching the pull wire to the
catheter body, and methods of reducing stress on the pull wire are
disclosed in aforementioned U.S. application Ser. No.
08/960,902.
[0098] The center support 150 is similar to the center support 20
illustrated in FIG. 2 in that it is positioned inside the distal
member 140 and is preferably a rectangular wire formed from
resilient inert wire, such as Nitinol.RTM. or 17-7 stainless steel
wire. The thickness of the rectangular center support 150 is
preferably between about 0.010 inch and about 0.020 inch. Resilient
injection molded plastic can also be used. Although other cross
sectional configurations can be used, such as a round wire, a
rectangular cross section arranged such that the longer edge
extends in the longitudinal direction is preferred. This
orientation reduces the amount of force required to pull the distal
member 140 into the loop configuration illustrated in FIG. 17. The
preferred orientation also increases the stiffness of the loop in
the longitudinal direction, which allows the physician to firmly
press the present structure against tissue. The center support 150,
which may also be heat set into the preset curvature, is secured
within the catheter body 136 in the manner described above with
reference to FIGS. 1-7.
[0099] As illustrated for example in FIG. 19, the curved portion
142 of the proximal member 138 will be straightened out when the
catheter 134 is within the sheath 32. After the exemplary catheter
134 has been deployed, the curved portion will return to its curved
state and the pull wire may be retracted to form the loop
illustrated in FIG. 17.
[0100] The loop in the embodiment illustrated in FIGS. 17-21 is in
plane with the remainder of the catheter body 136. A stylet 160
allows the physician to reorient the loop from the orientation
illustrated in FIG. 17 to, for example, the orientation illustrated
in FIGS. 20 and 21 which is ninety degrees out of plane. The stylet
160 is soldered to the tip member 148 and extends through the
sheath 32 to the proximal end thereof. The tip member 148 is, in
turn, bonded to the distal member 140. The stylet 160 is preferably
formed from inert wire such as Nitinol.RTM. or 17-7 stainless steel
wire and should be stiffer than the center support 150.
[0101] The combination of the pre-shaped curved portion 142 and the
stylet 160 advantageously allows the physician to precisely
position the loop relative to the pulmonary vein or other bodily
orifice. As a result, the exemplary catheter 134 can be used to
create lesions in or around the pulmonary vein or other bodily
orifice in an expedient manner without occluding blood or other
bodily fluid flow.
[0102] Another exemplary loop catheter, which is generally
represented by reference numeral 162, is illustrated in FIGS.
22-24. The loop catheter illustrated in FIGS. 22-24 is
substantially similar to the loop catheter illustrated in FIGS.
17-21 and common elements are represented by common reference
numerals. Here, however, there is no stylet. Loop catheter 162 also
includes a pre-shaped curved portion 164 that positions the loop
out of plane with respect to the remainder of the catheter. More
specifically, the exemplary pre-curved portion 164 positions the
loop ninety degrees out of plane with respect to the remainder of
the catheter 162 and orients the loop such that the opening 166
defined thereby faces in the distal direction. Other curvatures may
be used as applications require.
[0103] A sheath 32 and a guidewire 161 (FIG. 25), as well as the
curvature of the pre-shaped curved portion 164, allows the
physician to precisely position the loop relative to the pulmonary
vein or other bodily orifice. As a result, the exemplary catheter
162 may be used to expediently create lesions in or around the
pulmonary vein or other bodily orifice without the occlusion of
blood or other bodily fluids.
[0104] The exemplary loop catheter 162 illustrated in FIGS. 22-24
has a generally circular loop (note FIG. 24). However, other loop
configurations, such as the elliptical loop configuration on the
catheter 167 illustrated in FIG. 26, may be employed as
applications require.
[0105] Still another exemplary loop catheter, which is generally
represented by reference numeral 163, is illustrated in FIGS. 27
and 28. The loop catheter illustrated in FIGS. 27 and 28 is
substantially similar to the loop catheter illustrated in FIGS.
17-21 and common elements are represented by common reference
numerals. Here, however, the pull wire 144 extends along the
exterior of the proximal member 138 and the stylet 160 is secured
to a collar 165 that is free to slide along the distal member 140
when the distal member is in the substantially linear state
illustrated in FIG. 27. The collar 165, which has an inner diameter
that is slightly larger than the outer diameter of the distal
member 140, is preferably formed from a relative soft material,
such a soft plastic or silicone rubber. Mechanical interference
will cause the collar 165 to become fixed in place when the distal
member 140 is bent. As a result, the physician can move the collar
165 to the desired location on the distal member 140 prior to
formation of the loop to vary the location at which pushing and
pulling forces will be applied by the stylet 160 and, therefore,
vary the ultimate shape and orientation of the loop.
[0106] The exemplary loop catheter 163 illustrated in FIGS. 27 and
28 has a generally circular loop. However, other loop
configurations, such as the elliptical loop configuration on the
catheter 167 illustrated in FIG. 26, may be employed as
applications require.
[0107] The catheters illustrated in FIGS. 17-28 may be used in
conjunction with conventional catheter handles that provide for the
manipulation of one or more control elements, such as a pull wire
and a stylet. Suitable handles are disclosed in U.S. Pat. Nos.
5,871,523 and 5,928,191.
[0108] IV. Electrodes, Temperature Sensing and Power Control
[0109] In each of the preferred embodiments, the operative elements
are a plurality of spaced electrodes 18. However, other operative
elements, such as lumens for chemical ablation, laser arrays,
ultrasonic transducers, microwave electrodes, and ohmically heated
hot wires, and such devices may be substituted for the electrodes.
Additionally, although electrodes and temperature sensors are
discussed below in the context of the exemplary catheter probe
illustrated in FIGS. 1-7, the discussion is applicable to all of
the probes disclosed herein.
[0110] The spaced electrodes 18 are preferably in the form of
wound, spiral coils. The coils are made of electrically conducting
material, like copper alloy, platinum, or stainless steel, or
compositions such as drawn-filled tubing (e.g. a copper core with a
platinum jacket). The electrically conducting material of the coils
can be further coated with platinum-iridium or gold to improve its
conduction properties and biocompatibility. A preferred coil
electrode is disclosed in U.S. Pat. No. 5,797,905. The electrodes
18 are electrically coupled to individual wires 168 (see, for
example, FIG. 2) to conduct coagulating energy to them. The wires
are passed in conventional fashion through a lumen extending
through the associated catheter body into a PC board in the
catheter handle, where they are electrically coupled to a connector
that is received in a port on the handle. The connector plugs into
a source of RF coagulation energy.
[0111] As an alternative, the electrodes may be in the form of
solid rings of conductive material, like platinum, or can comprise
a conductive material, like platinum-iridium or gold, coated upon
the device using conventional coating techniques or an ion beam
assisted deposition (IBAD) process. For better adherence, an
undercoating of nickel or titanium can be applied. The electrodes
can also be in the form of helical ribbons. The electrodes can also
be formed with a conductive ink compound that is pad printed onto a
non-conductive tubular body. A preferred conductive ink compound is
a silver-based flexible adhesive conductive ink (polyurethane
binder), however other metal-based adhesive conductive inks such as
platinum-based, gold-based, copper-based, etc., may also be used to
form electrodes. Such inks are more flexible than epoxy-based
inks.
[0112] The flexible electrodes 18 are preferably about 4 mm to
about 20 mm in length. In the preferred embodiment, the electrodes
are 12.5 mm in length with 1 mm to 3 mm spacing, which will result
in the creation of continuous lesion patterns in tissue when
coagulation energy is applied simultaneously to adjacent
electrodes. For rigid electrodes, the length of the each electrode
can vary from about 2 mm to about 10 mm. Using multiple rigid
electrodes longer than about 10 mm each adversely effects the
overall flexibility of the device, while electrodes having lengths
of less than about 2 mm do not consistently form the desired
continuous lesion patterns.
[0113] The portion of the electrodes that are not intended to
contact tissue (and be exposed to the blood pool) may be masked
through a variety of techniques with a material that is preferably
electrically and thermally insulating. This prevents the
transmission of coagulation energy directly into the blood pool and
directs the energy directly toward and into the tissue. For
example, a layer of UV adhesive (or another adhesive) may be
painted on preselected portions of the electrodes to insulate the
portions of the electrodes not intended to contact tissue.
Deposition techniques may also be implemented to position a
conductive surface only on those portions of the assembly intended
to contact tissue. Alternatively, a coating may be formed by
dipping the electrodes in PTFE material.
[0114] The electrodes may be operated in a uni-polar mode, in which
the soft tissue coagulation energy emitted by the electrodes is
returned through an indifferent patch electrode (not shown)
externally attached to the skin of the patient. Alternatively, the
electrodes may be operated in a bi-polar mode, in which energy
emitted by one or more electrodes is returned through other
electrodes. The amount of power required to coagulate tissue ranges
from 5 to 150 w.
[0115] As illustrated for example in FIGS. 5a and 5b, a plurality
of temperature sensors 170, such as thermocouples or thermistors,
may be located on, under, abutting the longitudinal end edges of,
or in between, the electrodes 18. Preferably, the temperature
sensors 170 are located at the longitudinal edges of the electrodes
18 on the distally facing side of the helical (or other loop)
structure. In some embodiments, a reference thermocouple 172 may
also be provided. For temperature control purposes, signals from
the temperature sensors are transmitted to the source of
coagulation energy by way of wires 174 (FIG. 2) that are also
connected to the aforementioned PC board in the catheter handle.
Suitable temperature sensors and controllers which control power to
electrodes based on a sensed temperature are disclosed in U.S. Pat.
Nos. 5,456,682, 5,582,609 and 5,755,715.
[0116] As illustrated for example in FIGS. 5a and 5b, the
temperature sensors 170 are preferably located within a linear
channel 171 that is formed in the distal member 16. The linear
channel 171 insures that the temperature sensors will directly face
the tissue and be arranged in linear fashion. The illustrated
arrangement results in more accurate temperature readings which, in
turn, results in better temperature control. As such, the actual
tissue temperature will more accurately correspond to the
temperature set by the physician on the power control device,
thereby providing the physician with better control of the lesion
creation process and reducing the likelihood that embolic materials
will be formed. Such a channel may be employed in conjunction with
any of the electrode (or other operative element) supporting
structures disclosed herein.
[0117] Finally, the electrodes 18 and temperature sensors 172 can
include a porous material coating, which transmits coagulation
energy through an electrified ionic medium. For example, as
disclosed in U.S. application Ser. No. 08/879,343, filed Jun. 20,
1997, entitled "Surface Coatings For Catheters, Direct Contacting
Diagnostic and Therapeutic Devices," electrodes and temperature
sensors may be coated with regenerated cellulose, hydrogel or
plastic having electrically conductive components. With respect to
regenerated cellulose, the coating acts as a mechanical barrier
between the surgical device components, such as electrodes,
preventing ingress of blood cells, infectious agents, such as
viruses and bacteria, and large biological molecules such as
proteins, while providing electrical contact to the human body. The
regenerated cellulose coating also acts as a biocompatible barrier
between the device components and the human body, whereby the
components can now be made from materials that are somewhat toxic
(such as silver or copper).
[0118] Although the present inventions have been described in terms
of the preferred embodiments above, numerous modifications and/or
additions to the above-described preferred embodiments would be
readily apparent to one skilled in the art. It is intended that the
scope of the present inventions extend to all such modifications
and/or additions and that the scope of the present inventions is
limited solely by the claims set forth below.
* * * * *