U.S. patent number 5,273,535 [Application Number 07/790,207] was granted by the patent office on 1993-12-28 for catheter with electrode tip having asymmetric left and right curve configurations.
This patent grant is currently assigned to EP Technologies, Inc.. Invention is credited to Stuart D. Edwards, Russell B. Thompson.
United States Patent |
5,273,535 |
Edwards , et al. |
December 28, 1993 |
Catheter with electrode tip having asymmetric left and right curve
configurations
Abstract
A catheter has an electrode tip assembly that is bendable at the
selection of the user in two different directions. The electrode
tip assembly assumes a different predetermined curve configuration
when bent in the two direction.
Inventors: |
Edwards; Stuart D. (Los Altos,
CA), Thompson; Russell B. (San Leandro, CA) |
Assignee: |
EP Technologies, Inc.
(Sunnyvale, CA)
|
Family
ID: |
25149959 |
Appl.
No.: |
07/790,207 |
Filed: |
November 8, 1991 |
Current U.S.
Class: |
604/95.01;
600/585 |
Current CPC
Class: |
A61M
25/0136 (20130101); A61M 25/0138 (20130101); A61M
25/0144 (20130101); A61N 1/06 (20130101); A61N
1/0565 (20130101); A61M 25/0147 (20130101); A61M
2025/0161 (20130101) |
Current International
Class: |
A61M
25/01 (20060101); A61N 1/05 (20060101); A61N
1/06 (20060101); A61B 001/00 () |
Field of
Search: |
;604/95,159,282
;128/772 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Preliminary report on a new method of intestinal intubation with
the aid of a flexible stylet with controllable tip." Smith et
al.--Surgery vol. 27 No. 6 Jun. 1950 pp. 817-821..
|
Primary Examiner: Green; Randall L.
Assistant Examiner: Clarke; Rob
Attorney, Agent or Firm: Ryan, Kees & Hohenfeldt
Claims
We claim:
1. A catheter comprising
a flexible wire member having left and right faces, the wire member
being bendable toward the right and toward the left in response to
external forces applied to the right face and left face,
respectively,
left and right steering wires having distal ends and proximal
ends,
means for attaching the distal ends of the left and right steering
wires to the left and right faces of the wire member,
respectively,
steering means movable in two paths for applying different external
bending forces on the flexible wire member, the steering means
including
a wheel having a left side and a right side,
means for attaching the proximal ends of the left and right
steering wires to the left wheel side and the right wheel side,
respectively,
means for rotating the wheel to the left and to the right,
first cam surface means formed on the left wheel side that bears
against and tensions the left steering wire in response to rotation
of the wheel to the left for bending the wire member toward the
left and into a first nonlinear configuration, and
second cam surface means formed on the right side of the wheel that
is different than the first cam surface means and that bears
against and tensions the right steering wire in response to
rotation of the wheel to the right for bending the wire member
toward the right and into a second nonlinear configuration
different than the first nonlinear configuration.
2. A catheter according to claim 1
wherein the points of attachment of the distal ends of the left and
right steering wires are generally symmetrically spaced on the left
and right faces of the wire member.
3. A catheter according to claim 1
wherein the points of attachment of the distal ends of the left and
right steering wires are generally asymmetrically spaced on the
left and right faces of the wire member.
4. A catheter according to claim 1
wherein the first and second cam faces are formed as curved having
different radii.
5. A catheter according to claim 1
wherein one of the first and second cam faces is generally linear
while the other one of the first and second cam faces is generally
nonlinear.
6. A catheter according to claim 1
wherein the flexible wire member includes opposite ends and
stiffening means for varying the stiffness of the wire member so
that one end of the wire member is more resistant to bending than
the other end.
7. A catheter according to claim 1 and further including
a guide tube having a distal end attached to the flexible wire
member, and
handle means attached to the proximal end of the guide tube for
holding the steering means.
8. A catheter according to claim 7
wherein the handle means includes sleeve means gripping the guide
tube and having a coefficient of friction that translates rotation
of the handle means about the axis of the guide tube into rotation
of the guide tube about its axis.
Description
FIELD OF THE INVENTION
The invention generally relates to catheters. In a more specific
sense, the invention relates to catheters that can be steered and
manipulated within interior regions of the body from a location
outside the body.
BACKGROUND OF THE INVENTION
Physicians make widespread use of catheters today in medical
procedures to gain access into interior regions of the body. In its
important that the physician can control carefully and precisely
the movement of the catheter within the body.
The need for careful and precise control over the catheter is
especially critical during procedures that ablate tissue within the
heart. These procedures, called electrophysiological therapy, are
becoming more widespread for treating cardiac rhythm
disturbances.
During these procedures, a physician steers a catheter through a
main vein or artery (which is typically the femoral arterial) into
the interior region of the heart that is to be treated. The
physician then further manipulates a steering mechanism to place
the electrode carried on the tip of the catheter into direct
contact with the tissue that is to be ablated. The physician
directs radio frequency energy into the electrode tip to ablate the
tissue and form a lesion.
Cardiac ablation especially requires the ability to precisely bend
and shape the tip end of the catheter to position the ablation
electrode.
SUMMARY OF THE INVENTION
The invention provides a catheter having a distal tip section that
is bendable at the selection of the user in two different
directions. The distal tip section assumes different predetermined
curves when bent in each direction.
The invention provides a catheter having a body that is bendable in
different first and second directions in response to external
forces. The catheter includes a steering mechanism that is movable
in two paths for applying different external bending forces on the
body.
The steering mechanism includes a first actuator that operates in
response to movement of the steering mechanism in the first path.
The first actuator bends the body in the first direction into a
first predetermined nonlinear shape.
The steering mechanism also includes a second actuator that
operates in response to movement of the steering mechanism in the
second path. The second actuator bends the body in the second
direction into a second predetermined nonlinear shape. The second
shape is different from the first shape.
In one embodiment, the bendable body includes a flexible wire
member having left and right faces. In this arrangement, the
steering mechanism includes left and right steering wires. The
distal ends of the steering wires are attached, respectively, to
the left and right faces of the wire member.
In this embodiment, the first actuator places the left steering
wire into tension to bend the wire member to the left into the
first nonlinear shape. The second actuator places the right
steering wire into tension to bend the wire member to the right
into the second nonlinear shape.
In one embodiment, the points of attachment of the distal ends of
the left and right steering wires are generally symmetrically
spaced on the left and right faces of the wire member. In another
arrangement, the points of attachment of the distal ends of the
left and right steering wires are generally asymmetrically spaced
on the left and right faces of the wire member.
In one embodiment, the steering mechanism includes a wheel to which
the proximal ends of the left and right steering wires are
attached. A lever mechanism rotates the wheel to the left and to
the right.
In this arrangement, the first actuator includes a first cam
surface formed on the left side of the wheel. The first can surface
bears against and tensions the left steering wire in response to
rotation of the wheel to the left.
Also in this arrangement, the second actuator includes a second cam
surface formed on the right side of the wheel. The second cam
surface is different from the first cam surface. The second cam
surface bears against and tensions the right steering wire in
response to rotation of the wheel to the right.
In one embodiment, the first and second cam faces form curves
having different radii. In another embodiment, one cam face is
generally linear, while the other cam face is generally
nonlinear.
By varying the symmetrical relationships among the cam faces and
the points of steering wire attachment, the bendable wire can form
a multitude of different left and right curve shapes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a catheter that embodies the
features of the invention;
FIG. 2A is a side section view of the catheter taken generally
along line 2A--2A in FIG. 1;
FIG. 2B is an exploded view of FIG. 2A;
FIG. 3A is an exploded view of the electrode tip assembly of the
catheter;
FIG. 3B is a view of an alternative guide tube shaft for the
catheter;
FIG. 4 is a perspective view of the stiffening assembly for the
support wire of the catheter;
FIGS. 5A to D show the assembly of reinforcing tube that surrounds
the support wire of the catheter;
FIGS. 6A to C show the steering mechanism for Curve Option 1 of the
catheter;
FIGS. 7A to C show the steering mechanism for Curve Option 2 of the
catheter;
FIGS. 8A to C show the steering mechanism for Curve Option 3 of the
catheter;
FIGS. 9A to C show the steering mechanism for Curve Option 4 of the
catheter; and
FIGS. 10A to C show the steering mechanism for Curve Option 5 of
the catheter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows the assembly of a steerable catheter 10 that embodies
the features of the invention. As there shown, the catheter 10
includes three main parts or assemblies: the handle assembly 12,
the guide tube assembly 14, and the electrode tip assembly 16.
The catheter 10 can be used in many different environments. This
specification will describe the catheter 10 as used to provide
electrophysiologic therapy in the interior regions of the
heart.
When used for this purpose, a physician grips the handle assembly
12 to steer the guide tube assembly 14 through a main vein or
artery (which is typically the femoral arterial) into the interior
region of the heart that is to be treated. The physician then
further manipulates a steering mechanism 18 on the handle assembly
12 (which will be described later) to place the electrode tip
assembly 16 in contact with the tissue that is to be ablated. The
physician directs radio frequency energy into the electrode tip
assembly 16 to ablate the tissue contacting the electrode tip
assembly 16.
As FIGS. 2A and 2B best show, the handle assembly 12 includes a
housing 20 that encloses the steering mechanism 18. The steering
mechanism 18 includes a rotating cam wheel 22 carried on a screw 24
within the housing 20. The cam wheel 22 is seated for rotation
between a top washer 26 and a bottom washer 28. A lock nut 30 and a
pin 32 couple an external steering lever to the top of the cam
wheel 22. The steering lever 34 seats against an O-ring 36.
Movement of the steering lever 34 by the user rotates the cam wheel
22 about the screw 24 within the housing 20. Clockwise movement of
the steering level rotates the cam wheel 22 to the right.
Counterclockwise movement of the steering wheel rotates the cam
wheel 22 to the left. Contact between the steering lever 34 and the
side of the housing 20 physically limits the range of left and
right rotation of the cam wheel 22 within the housing 20.
The steering mechanism 18 also includes an external locking lever
38 that an adhesive couples to the head of the screw 24. The
locking lever 38 seats against another O-ring 36.
Movement of the locking lever 38 rotates the screw 24. Clockwise
rotation of the locking lever 38 tightens the screw 24 to increase
the seating force between the cam wheel 22 and the bottom washer
28. When moved fully clockwise into contact against the housing 20,
the locking lever 38 imposes a seating force that prevents rotation
of the cam wheel 22 by the steering lever 34. Counterclockwise
movement of the locking lever 34 loosens the screw 24 to decrease
the seating force and free the cam wheel 22 for rotation.
The cam wheel 22 includes a forward cam face 40 and a rear cam face
42. The forward cam face 40 is oriented toward the front of the
housing 20, where the guide tube assembly 14 attaches. The forward
cam face includes a right side surface 44 and a left side surface
46.
The rear cam face 42 is oriented toward the back of the housing 20,
where a coaxial cable 48 attaches. The rear cam face includes right
and left side surfaces 50 and 52.
The cam wheel 22 also carries a wire fastener 54 between the right
and left side surfaces 50 and 52 of the rear cam face 42. The wire
fastener 54 holds the proximal ends of right and left catheter
steering wires 56 and 58, which are soldered to the interior of the
fastener 54.
The steering wires 56 and 58 extend from the opposite ends of the
fastener 54 and along the associated left and right side surfaces
44/46 and 50/52 of the front and rear cam faces 40 and 42. The
steering wires exit the front of the housing 20 through the
interior bore of a tension screw assembly 60.
As will be described in greater detail later, the distal ends of
the steering wires 56 and 58 are attached to the electrode tip
assembly 16. They extend from the wire fastener 54 through the
guide tube assembly 14 to the electrode tip assembly 16.
As also will be described in greater detail, the wire fastener 54
in association with the cam faces 40 and 42 translate rotation of
the cam wheel 22 into lateral pulling movement of the steering
wires 56 and 58 attached to the electrode tip assembly 16.
By rotating the cam wheel 22 to the left (by moving the steering
lever 34 counterclockwise), the left steering wire 58 bears against
the left front and rear cam surfaces 46 and 52. The cam surfaces 46
and 52 tension the left steering wire 58 to impose a discrete,
constant pulling force that causes the electrode tip assembly 16 to
bend to the left.
Also, by rotating the cam wheel 22 to the right (by moving the
steering lever 34 clockwise), the right steering wire 56 bears
against the right front and rear cam surfaces 44 and 56. The cam
surfaces 44 and 56 tension the right steering wire 56 to impose a
discrete, constant pulling force that causes the electrode tip
assembly 16 to bend to the right.
Rotation of the tension screw assembly 60 additionally varies the
amount of slack (i.e., tension) in the steering wires 56 and 58
between the wire fastener 54 and the distal ends of the steering
wires 56 and 58. This controls the responsiveness of the electrode
tip assembly 16 to rotation of the cam wheel 22.
The component parts of the handle assembly 12 can be constructed of
various materials, depending upon the durability needed and the
sterilization process used.
For example, when EtO sterilization is used, the housing 20 and
bottom washer 28 can be made of a polycarbonate material. In this
arrangement, the cam wheel 22, steering lever 34, and locking lever
38 can be made of a delrin material. These plastic materials are
durable and EtO sterilizable. In this assembly, the lock nut 30,
pin 32, and screw 24 are preferably made of a metallic material
like brass or stainless steel.
As FIG. 3A shows, the guide tube assembly 14 includes a flexible
shaft 62 attached to the handle assembly 12. The flexible shaft 62
encloses an interior bore 64. The steering wires 56 and 58 pass
through the interior bore 64.
The shaft 62 may constructed in various ways. In the embodiment
shown in FIG. 3, the shaft 62 comprises a length of stainless steel
coiled into a flexible spring enclosing the interior bore 64. A
braided sheath 66 of plastic material encloses the coil.
Alternatively (as FIG. 3B shows), the shaft 62 comprises a slotted,
stainless steel tube enclosing the interior bore 64. An array of
slots 70 subtends the tube along its length. The slots 70 subtend
less than one circumference of the shaft 62 at an angle of between
270 degrees to 300 degrees. The slots 70 are also radially offset
one from the other by about 30 degrees to 120 degrees.
The slotted shaft 62 shown in FIG. 3B provides strength and
flexibility along the length of the guide tube assembly 14. The
slotted shaft 62 also transmits twisting motions (torque) from the
handle assembly 12 to the electrode tip assembly 16 more directly
than the coiled shaft 62 shown in FIG. 3. Further details of the
slotted shaft 62 are disclosed in pending Lundquist U.S. patent
application Ser. No. 07/657,106 filed Feb. 15, 1991 and entitled
"Torquable Catheter 10 and Method."
Like the coiled shaft 62 in FIG. 3A, a sheath 66 encloses the
slotted shaft. The sheath 66 is made from a plastic material, such
as polyolefin.
The handle assembly 12 includes a tubular stem 74 though which the
proximal end of the guide tube assembly 14 extends for attachment
to the tension screw assembly 60. Adhesive attaches the proximal
end of the coil to the tension screw assembly 60.
The guide tube assembly 14 can be made in various lengths. In the
illustrated, the guide tube assembly 14 is about 100 cm in
length.
As FIGS. 1 and 2A/B show, a sleeve 76 couples the guide tube
assembly 14 to the handle assembly 12. Adhesive secures one end of
the sleeve 76 to the handle stem 74. The sleeve 76 includes an
interior bore that progressively tapers from the handle stem 74
into a tight interference fit about the sheath 66 of the guide tube
assembly 14. The exterior of the sleeve 76 also tapers, extending
about 4 to 5 inches beyond the front of the handle housing 20.
The sleeve 76 is made of a material having a high coefficient of
friction, like Krayton G2703. The sleeve 76 provides a gripping
surface to help the user manipulate the catheter 10. When used in
association with the slotted tube, the sleeve 76 also significantly
enhances the transmission of torque from the handle assembly 12 to
the electrode tip assembly 16 through the guide tube assembly
14.
The electrode tip assembly 16 includes a bendable main support wire
78 having left and right faces 78L and 78R. In the illustrated
embodiment, the main support wire 78 is made of stainless steel
flat wire stock in an elongated shape about 0.035 inch wide and
about 0.005 inch thick. The main support wire 78 is about 3 inches
in total length.
The opposite ends of the main support wire 78 are cut away to form
stepped shoulders 80 and 82. In the illustrated embodiment, the
shoulders 80 and 82 are about 0.024 inch wide and aligned along the
centerline of the main support wire 78. Each shoulder 80 and 82 is
about 12 inch in length.
As FIG. 3A shows, one stepped shoulder 80 fits within the distal
end of the flexible guide tube shaft 62 to append the electrode tip
assembly 16 to the guide tube assembly 14. When properly oriented,
the left and right faces 78L and 78R of the main support wire 78
lie in a plane that is generally parallel to the axis about which
the cam wheel 22 rotates. Stated differently, when the user holds
the handle assembly 12 in a horizontal plane, the left and right
faces 78L and 78R of the main support wire 78 lie in a vertical
plane.
As FIG. 3A shows, the distal end of the left steering wire 58 is
soldered to the left face 78L of the main support wire 78. When
pulled by left rotation of the cam wheel 22, the left steering wire
58 bends the main support wire 78 to the left.
Also, the distal end of the right steering wire 56 is soldered to
the right face 78R of the main support wire 78. When pulled by
right rotation of the cam wheel 22, the right steering wire 56
bends the main support wire 78 to the right.
In the illustrated embodiment, the stiffness of the main support
wire 78 is not uniform, but varies along its length. Its stiffest
point is near its proximal end region, where it joins the guide
tube shaft 62. Its stiffness is least at the tip end 88 of the
shoulder 82. By varying the stiffness of the main support wire 78
between its proximal end and its distal tip end 88, the base of the
electrode tip assembly 16 (where it joins the guide tube assembly
14) resists bending and buckling. The bending forces generated by
the steering wires 56 and 58 are directed toward the distal tip end
88 of the main support wire 78. The variable stiffness of the main
support wire 78 concentrates the bending forces at the distal tip
end 88 of the electrode tip assembly 16.
There are various ways to varying the stiffness of the main support
wire 78 along its length. One way (not shown) is to vary the
thickness of the main support wire 78 as it is manufactured, so
that it is thickest (i.e., most stiff) near the shoulder 80 that,
in use, is fitted within the guide tube shaft 62.
In the illustrated and preferred embodiment (see FIG. 4), a
stiffening spring assembly 90 stiffens the center support near the
distal end of the guide tube shaft 62. The stiffening spring
assembly 90 includes two leaf springs 92 that sandwich the main
support wire 78 between them. Each leaf spring 92 is made of
stainless steel flat wire stock in an elongated shape that is about
0.039 inch wide and about 0.0029 inch thick.
The stiffening spring assembly 90 can sized and configured to
provide the degrees of stiffness and variance wanted. In the
illustrated embodiment, the stiffening spring assembly 90 stiffens
the main support wire 78 beginning about 0.030 to 0.050 inch from
the inner edge of the attachment shoulder 80 and extending from
there about 1.5 inches.
In the illustrated embodiment, spot welds 94 secure the leaf
springs 92 to the main support wire 78. The three spot welds 94
shown are clustered near the proximal end of the stiffening spring
assembly 90. There, they are evenly spaced, with the most distal
spot weld 94 being about 0.10 inch from the proximal end of the
stiffening spring assembly 90.
In the illustrated embodiment, the distal end of the electrode tip
assembly 16 carries an ablation tip electrode 96 and three ring
electrodes 98. Interior conducting wires 100 are connected to the
tip electrode 96 and the three ring electrodes 98. The conducting
wires 100 extend along the main support wire 78, through the
interior bore of the guide tube shaft 62, and into the handle
housing 20 to join the coaxial cable 48 that extends from the rear
of the housing 20.
The coaxial cable 48 ends with plugs 102. The plugs 102 connect
with appropriate conventional catheter control equipment (not
shown). The conducting wires 100 transfer electrical current from
the ring electrodes 98 indicative of electrical activity within the
heart. The conducting wires 100 also transfer radio frequency
energy to the tip electrode 96 to carry out ablation procedures
within the heart.
There are various ways of securing the attachment between the
electrode tip assembly 16 and the guide tube assembly 14. The
illustrated embodiment employs a reinforcing sleeve assembly 104
for this purpose.
As shown in the FIGS. 5A to D, the reinforcing sleeve assembly 104
is made in association with a specially designed sleeve mandrel
106. In the illustrated embodiment, the sleeve mandrel 106 is made
from stainless steel and is about 7 inches in total length. As FIG.
5A shows, the mandrel 106 has a first cylindrical body portion 108
and second cylindrical body portion 110 having an enlarged
diameter. In the illustrated embodiment, the first body portion 108
is about 0.032 inch in diameter and is about 5 inches long. The
second body portion 110 has an enlarged diameter of about 0.043
inch and is about 2 inches long. The first body portion 108 and the
second body portion 110 each includes an inwardly sloping notch
112.
In making the reinforcing sleeve assembly 104 (see FIG. 5A), a
sleeve mandrel 106 receives a first heat shrink tube 114 that, in
the illustrated embodiment, is about 4.5 inches long. A portion of
the first tube 114 is pulled over the second body portion 110 of
the mandrel 106. Heat is applied using an oven or heat gun to
shrink the tube in place upon the sleeve mandrel 106.
Next (see FIG. 5B), a reinforcing fabric 116 is wrapped in tension
over the first tube 114 while still on the mandrel 106. The fabric
116 is wrapped as a single spiral about the first tube 114 to
obtain a desired, closely spaced pitch. In the illustrated
embodiment the fabric 116 is wrapped to a pitch of about 18 to 20
wraps per inch. The notches 112 on the sleeve mandrel 106 hold the
fabric 116 in tension during this step of the manufacturing
process.
The mandrel 106 now receives a second heat shrink tube 118 over the
fabric-wrapped first tube 114 (see FIGS. 5B and 5C). The second
tube 118 is shorter than the first tube 114, and is not pulled over
the second body portion 110 of the sleeve mandrel 106. In the
illustrated embodiment, the second tube 118 is about 4.0 inches
long.
Heat is again applied using an oven or heat gun to shrink the
second tube 118 in place over the fabric-wrapped first tube 114.
When shrunk in place, the second tube 118 captures and encases the
wrapped fabric 116 and underlying first tube 114 (as FIG. 5C
shows).
Next (see FIG. 5D), the fabric 116 extending from the second tube
118 to the notches 112 is cut away. The reinforcing sleeve assembly
104 is removed from mandrel 106.
The reinforcing sleeve assembly 104 is inserted over the main
support wire 78 appended to the distal end of the guide shaft 62
(see FIG. 3A) so that the enlarged diameter portion of the
reinforcing sleeve assembly 104 slips over the distal end of the
guide shaft 62. At this time, the left and right steering wires 56
and 58 and stiffening spring assembly 90 are attached to the main
support wire 78. The conducting wires 100 also extend along the
main support wire 78 and into the bore of the guide shaft 62.
Heat is again applied using an oven or heat gun to finally shrink
the second tube 118 in place over distal end of the guide shaft 62
and over the main support wire 78 and its associated parts. When
finally shrunk in place, the reinforcing sleeve assembly 104
tightly encases the main support wire 78.
The wrapped fabric 116 becomes an integrated part of the
reinforcing sleeve assembly 104. The reinforcing sleeve assembly
104 is flexible enough to accommodate the bending movement desired
for the electrode tip assembly 16. Still, due to the wrapped fabric
116, the reinforcing sleeve assembly 10 provides added strength and
resistance against wear and tear during repeated bending
operations.
The reinforcing sleeve assembly 104 also holds the steering wires
56 and 58 and conducting wires 100 in close intimate contact
against the main support wire 78. The intimate contact prevents
kinking and chafing of the steering wires 56 and 58 and conducting
wires 100 during bending operations.
The materials used to make the reinforcing sleeve assembly 104 can
vary. In the illustrated embodiment, the shrink tubes 114 and 118
are made from medical grade TFE Teflon material having a 2 to 1
shrink ratio. The material used has a wall thickness (after heat
shrinkage) of about 0.003 to 0.0045 inch. In the illustrated
embodiment, the fabric 116 is a Kevlar 49 Yarn (which is available
from DuPont). This material has a tensile strength of about 400,000
lbs/in.sup.2 and a modulus of about 18,000,000 lbs/in.sup.2.
An outer tube 120 covers the reinforcing sleeve assembly 104. The
tip electrode 96 and ring electrodes 98 are attached to the
conducting wires 100 and joined to the outer tube 120 by
conventional methods to complete the electrode tip assembly 16.
In the illustrated embodiment, the curvature assumed upon bending
the electrode tip assembly 16 to the left is different that the
curvature assumed upon bending the electrode tip assembly 16 to the
right. The electrode tip assembly 16 assumes one curvature when
bent to the left and a different curvature when bent to the right.
These different left and right curvatures provide the physician
with flexibility in steering the tip electrode 96 into position.
These differing curvatures will be called asymmetric curves.
The drawings show five representative asymmetric curve options that
embody the features of the invention. The invention achieves the
different curve options by varying two relationships.
The first relationship is that between the cam radius on the left
side surfaces 46 and 52 of the forward cam and rear cam faces 40
and 42, and the cam radius on the right side surfaces 44 and 50 of
the forward and rear cam faces 40 and 42. According to the
invention, the cam radii differ, forming various asymmetric cam
arrangements.
The second relationship is that between the point of attachment of
the left steering wire 58 on the left face 78L of the main support
wire 78 and the point of attachment of the right steering wire 56
on the right face 78R of the main support wire 78. According to the
invention, the point of attachment can be varied, forming both
symmetrical and asymmetric steering wire attachment sites.
Combinations of asymmetric cam arrangements and symmetrical and
asymmetric steering wire attachments create differing asymmetric
curve options. The five curve options shown are intended to
illustrate the ideas of forming asymmetric curves by varying the
two relationships, but they do not encompass all the possible curve
options that can be made.
Asymmetric Curve Option 1
As FIGS. 6A to C show, the catheter 10 includes an asymmetric
forward cam face 40 on the cam wheel 22 and a symmetrical rear cam
face 42. In addition, the electrode tip assembly 16 includes
asymmetric attachments of the left and right steering wires 56 and
58 to the left and right faces 78L and 78R of the main support wire
78.
More particularly, the right side surface 44 of the forward cam
face 40 is formed with a radius of 0.3125 inch, while the left side
surface 46 of the forward cam face 40 is formed with a radius of
0.4062 inch. The right and left side surfaces 50 and 52 of the rear
cam face 42 each has a radius of 0.313".
The right steering wire 56 is attached at the distal tip 88 of the
main support wire 78, while the left steering wire 58 is attached
about 1.5 inches from the distal tip 88 of the main support wire
78.
When the steering lever 34 is rotated clockwise, the foregoing
relationships bend the main support wire 78 about 270 degrees to
the right to form a looping "pigtail" curve. When the steering
lever 34 is rotated counterclockwise, the foregoing relationships
bend the main support wire 78 about 90 degrees to the left to form
an elbow curve.
Asymmetric Curve Option 2
As FIGS. 7A to C show, the catheter 10 includes symmetrical forward
and rear cam faces 40 and 42 on the cam wheel 22 in combination an
asymmetric attachment of the left and right steering wires 56 and
58 to the main support wire 78 to achieve the asymmetric left and
right curves in Option 2.
More particularly, the right side surface 44 and the left side
surface 46 of the forward cam face 40 are both formed with a radius
of 0.4062 inch. The right side surface 50 and the left side surface
52 of the rear cam face 42 are both formed with a radius of
0.313".
The right steering wire 56 is attached at the distal tip 88 of the
main support wire 78, while the left steering wire 58 is attached
about 1.5 inches from the distal tip of the main support wire
78.
When the steering lever 34 is rotated clockwise, the foregoing
relationships bend the main support wire 78 about 135 degrees to
the right to form an open, arching curve. When the steering lever
34 is rotated counterclockwise, the foregoing relationships bend
the main support wire 78 about 90 degrees to the left to form an
elbow curve (just as in Curve Option 1).
Asymmetric Curve Option 3
As FIGS. 8A to C show, the catheter 10 includes an asymmetric
forward cam face 40 on the cam wheel 22 and a symmetrical rear cam
face 42. In addition, the electrode tip assembly 16 includes
symmetrical attachments of the left and right steering wires 56 and
58 to the left and right faces 78L and 78R of the main support wire
78.
More particularly, the right side surface 44 of the forward cam
face 40 is formed with a radius of 0.3125 inch, while the left side
surface 46 of the forward cam face 40 is formed with a radius of
0.4062 inch. The right and left side surfaces 50 and 52 of the rear
cam face 42 each has a radius of 0.313".
The right and left steering wires 56 and 58 are attached at the
distal tip 88 of the main support wire 78.
When the steering lever 34 is rotated clockwise, the foregoing
relationships bend the main support wire 78 about 270 degrees to
the right to form a looping "pigtail" curve (as in Curve Option 1,
where the same cam and steering wire relationships exist on the
right side). When the steering lever 34 is rotated
counterclockwise, the foregoing relationships bend the main support
wire 78 about 80 degrees to the left to form a partial arch.
Asymmetric Curve Option 4
As FIGS. 9A to C show, both forward and rear cam faces 40 and 42 on
the cam wheel 22 are asymmetric. The electrode tip assembly 16
includes a symmetrical attachment of the left and right steering
wires 56 and 58 to the main support wire 78.
More particularly, the right side surface 44 of the forward cam
face 40 is formed with a radius of 0.3125 inch. The left side
surface 52 of the forward cam face 40 is formed as a straight
(i.e., linear) line. The linear line extends along a tangent from
an interior hub 68 of the cam wheel 22 to intersect the curved
(i.e., nonlinear) right side surface 44.
The left side surface 52 of the rear cam face 42 extends arcuately
from the tangent along the circumference of the interior hub 68. In
contrast, the right side surface 50 is asymmetrically formed with a
radius of 0.313".
The right steering wire 56 and the left steering wire 52 are both
attached at the distal tip 88 of the main support wire 78.
When the steering lever 34 is rotated clockwise, the foregoing
relationships bend the main support wire 78 in an open arch about
135 degrees. When the steering lever 34 is rotated
counterclockwise, the foregoing relationships bend the main support
spring in a tighter arch about 135 degrees to the left to form a
"shepard's crook" curve.
Asymmetric Curve Option 5
As FIGS. 10A to C show, the catheter 10 includes an asymmetric
forward cam face 40 and a symmetrical rear cam face 42. The
electrode tip assembly 16 includes symmetrical attachments of the
left and right steering wires 56 and 58 to the main support wire
78.
More particularly, the right side surface 50 of the forward cam
face 40 is formed with a radius of 0.3125 inch, while the left side
surface 46 of the forward cam face 40 is formed with a radius of
0.4062 inch. The left and right side surfaces 50 and 52 of the rear
cam face 42 are each formed with a radius of 0.313".
The right steering wire 56 and the left steering wire 58 are both
attached at the distal tip 88 of the main support wire 78.
When the steering lever 34 is rotated clockwise, the foregoing
relationships bend the main support spring about 270 degrees to the
right to form the looping "pigtail" curve (as in Curve Options 1
and 3). When the steering lever 34 is rotated counterclockwise, the
foregoing relationships bend the main support spring about 135
degrees to the left to form a "shepard's crook" curve (like the
right curve in Curve Option 4).
The following table summarizes the relationships that were varied
to achieve Curve Options 1 to 5.
TABLE 1 ______________________________________ Asymmetric Curve
Options 1 to 5 Curve Left Left Right Right Option Wire Cam* Wire
Cam* ______________________________________ 1 1.5" .4062" Tip
.3125" 2 1.5" .4062" Tip .4062" 3 0.75" .4062" Tip .3125" 4 Tip
Linear Tip .4062" 5 Tip .4062" Tip .3125"
______________________________________
Various features of the invention are set forth in the following
claims.
* * * * *