U.S. patent application number 16/866026 was filed with the patent office on 2020-09-24 for catheter having a distal section with spring sections for biased deflection.
The applicant listed for this patent is BIOSENSE WEBSTER (ISRAEL) LTD.. Invention is credited to Ariel GARCIA, Jeffrey W. SCHULTZ.
Application Number | 20200297417 16/866026 |
Document ID | / |
Family ID | 1000004885331 |
Filed Date | 2020-09-24 |
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United States Patent
Application |
20200297417 |
Kind Code |
A1 |
GARCIA; Ariel ; et
al. |
September 24, 2020 |
CATHETER HAVING A DISTAL SECTION WITH SPRING SECTIONS FOR BIASED
DEFLECTION
Abstract
A catheter has a distal section that includes a spring member
having at least a slot, a rib and a spine for biasing the distal
section for deflection within a single plane. Depending on the
plurality and orientation of slot(s), rib(s) and spine(s)s, the
distal section can allow for deflection in two opposing directions
while allowing only limited deflection in perpendicular directions
to maintain torquability, axial loading capabilities, and side
force performance.
Inventors: |
GARCIA; Ariel; (Glendora,
CA) ; SCHULTZ; Jeffrey W.; (Chino, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BIOSENSE WEBSTER (ISRAEL) LTD. |
Yokneam |
|
IL |
|
|
Family ID: |
1000004885331 |
Appl. No.: |
16/866026 |
Filed: |
May 4, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13481691 |
May 25, 2012 |
10639099 |
|
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16866026 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2018/00029
20130101; A61B 34/20 20160201; A61M 25/0051 20130101; A61B 18/1492
20130101; A61B 2018/00107 20130101; A61M 25/0138 20130101; A61B
2018/00083 20130101; A61B 2018/00821 20130101; A61M 2025/0166
20130101; A61B 2218/002 20130101; A61M 2025/0161 20130101; A61B
2018/00011 20130101; A61B 2018/00839 20130101 |
International
Class: |
A61B 18/14 20060101
A61B018/14; A61M 25/01 20060101 A61M025/01 |
Claims
1. A catheter, comprising: an elongated catheter body; a distal
section distal the catheter body, the distal section comprising: a
spring member having an elongated hollow body defining a
longitudinal axis and a lumen extending along the length, the
spring member having at least one first section and at least one
second section, the at least one second section having at least two
spines extending longitudinally respectively along a first side and
a second side of the spring member, and at least two rows of ribs
defined by slots extending respectively along a third and a fourth
side of the spring member, the ribs and the slots being transverse
to the longitudinal axis; at least one ring electrode carried on
the at least one first section of the spring member; and at least
one support member positioned in the lumen in the at least one
first section of the spring member to support the at least one ring
electrode, wherein the spring member is more compressible in the
second section bi-directionally in a plane intersecting the first
and second sides, and less compressible in the second section in a
plane intersecting the third and fourth sides.
2. A catheter of claim 1, further comprising an irrigation tubing
extending through the catheter body, into the distal section
through the lumen of the spring member and reaching the at least
one first section so as to provide a fluid passage to the at least
one ring electrode.
3. A catheter of claim 1, wherein the slots and ribs of each row
are aligned with each other.
4. A catheter of claim 1, wherein the slots and ribs of each row
are offset from each other.
5. A catheter of claim 1, wherein the first section is devoid of
slots and ribs.
6. A catheter of claim 1, wherein a coil sensor is wound around an
outer surface of the at least one support member.
7. A catheter of claim 1, wherein the coil sensor is wound in a
groove formed in an outer surface of the at least one support
member.
Description
CROSS-REFERENCE TO CO-PENDING APPLICATION
[0001] The present application is a Divisional Application under 35
U.S.C. .sctn. 121 of U.S. patent application Ser. No. 13/481,691,
filed May 25, 2012. The entire contents of this application is
incorporated by reference herein in its entirety.
FIELD OF INVENTION
[0002] The present invention relates to an electrophysiologic
catheter that is particularly useful for ablation and sensing
electrical activity of heart tissue.
BACKGROUND OF INVENTION
[0003] Electrode catheters have been in common use in medical
practice for many years. Diagnosis and treatment of cardiac
arrythmias by means of electrode catheters include mapping the
electrical properties of heart tissue and selectively ablating
cardiac tissue by application of energy. Such ablation can cease or
modify the propagation of unwanted electrical signals from one
portion of the heart to another. The ablation process destroys the
unwanted electrical pathways by formation of non-conducting
lesions. Various energy delivery modalities have been disclosed for
forming lesions, and include use of microwave, laser and more
commonly, radiofrequency energies to create conduction blocks along
the cardiac tissue wall.
[0004] In a two-step procedure--mapping followed by
ablation--electrical activity at locations within the heart is
typically sensed and measured by advancing a catheter containing
one or more electrical sensors (or electrodes) into the heart, and
acquiring data at a multiplicity of locations. These data are then
utilized to select the tissue target areas at which ablation is to
be performed.
[0005] In use, the electrode catheter is inserted into a major vein
or artery, e.g., the femoral artery, and then guided into a chamber
of the heart. A reference electrode is provided, generally taped to
the patient's skin or provided on the ablation catheter or another
catheter. Radio frequency (RF) current is applied to the ablation
electrode of the catheter, and flows through the surrounding media,
i.e., blood and tissue, toward the reference electrode. The
distribution of current depends on the amount of electrode surface
in contact with the tissue, as compared to blood which has a higher
conductivity than the tissue.
[0006] Heating of the tissue occurs due to its electrical
resistivity. The tissue is heated sufficiently to cause cellular
destruction in the cardiac tissue resulting in formation of a
lesion within the cardiac tissue which is electrically
non-conductive. During this process, heating of the ablation
electrode also occurs as a result of conduction from the heated
tissue to the electrode itself. If the electrode temperature
becomes sufficiently high, possibly above 60.degree. C., a thin
transparent coating of dehydrated blood can form on the surface of
the electrode. If the temperature continues to rise, this
dehydrated layer of blood can become progressively thicker
resulting in blood coagulation on the electrode surface. Because
dehydrated biological material has a higher electrical resistance
than tissue, impedance to the flow of electrical energy into the
tissue also increases. If the impedance increases sufficiently, an
impedance rise occurs and the catheter must be removed from the
body and the tip electrode cleaned.
[0007] In a typical application of RF current, circulating blood
provides some cooling of the ablation electrode. Another method is
to irrigate the ablation electrode, e.g., with physiologic saline
at room temperature, to actively cool the ablation electrode
instead of relying on the more passive physiological cooling
provided by the blood. Because the strength of the RF current is no
longer limited by the interface temperature, current can be
increased. This results in lesions which tend to be larger and more
spherical, usually measuring about 10 to 12 mm.
[0008] The clinical effectiveness of irrigating the ablation
electrode is dependent upon the distribution of flow within the
electrode structure and the rate of irrigation flow through the
catheter. Effectiveness is achieved by reducing the overall
electrode temperature and eliminating hot spots in the ablation
electrode which can initiate coagulum formation. More channels and
higher flows are more effective in reducing overall temperature and
temperature variations, i.e., hot spots. The coolant flow rate must
be balanced against the amount of fluid that can be injected into
the patient and the increased clinical load required to monitor and
possibly refill the injection devices during a procedure. In
addition to irrigation flow during ablation, a maintenance flow,
typically a lower flow rate, is required throughout the procedure
to prevent backflow of blood into the coolant passages. Thus,
reducing coolant flow by utilizing it as efficiently as possible is
a desirable design objective.
[0009] Another consideration is the ability to control the exact
position and orientation of the catheter tip. This is ability is
critical and largely determines the usefulness of the catheter. It
is generally known to incorporate into electrophysiology catheters
an electromagnetic (EM) tri-axis location/position sensor for
determining the location of a catheter's distal end. An EM sensor
in the catheter, typically near the catheter's distal end within
the distal tip, gives rise to signals that are used to determine
the position of the device relative to a frame of reference that is
fixed either externally to the body or to the heart itself. The EM
sensor may be active or passive and may operate by generating or
receiving electrical, magnetic or ultrasonic energy fields or other
suitable forms of energy known in the art.
[0010] U.S. Pat. No. 5,391,199, the entire disclosure of which is
incorporated herein by reference, describes a position-responsive
catheter comprising a miniature sensor coil contained in the
catheter's distal end. The coil generates electrical signals in
response to externally-applied magnetic fields, which are produced
by field-generator coils placed outside the patient's body. The
electrical signals are analyzed to determine three-dimensional
coordinates of the coil.
[0011] U.S. Pat. No. 6,690,963, the entire disclosure of which is
hereby incorporated by reference, is directed to a locating system
for determining the location and orientation of an invasive medical
instrument, for example a catheter or endoscope, relative to a
reference frame, comprising: a plurality of field generators which
generate known, distinguishable fields, preferably continuous AC
magnetic fields, in response to drive signals; a plurality of
sensors situated in the invasive medical instrument proximate the
distal end thereof which generate sensor signals in response to
said fields; and a signal processor which has an input for a
plurality of signals corresponding to said drive signals and said
sensor signals and which produces the three location coordinates
and three orientation coordinates of a point on the invasive
medical instrument.
[0012] Because of the size of the tip electrode and the limited
interior space therein, the EM sensor is often positioned outside
of the tip electrode, proximally thereof, and often off-axis from
the tip electrode which can reduce the accuracy of the position
sensing capabilities of the sensor. Being outside the tip
electrode, the position sensor is also exposed to bending stresses
and can limit the flexibility and deflection of the distal tip
section. Moreover, the sensor can be damaged by RF energy during
ablation.
[0013] Where the distal tip is irrigated, the efficiency of
irrigated cooling becomes a significant factor as ablation
procedures can last five or six hours resulting in extensive
fluid-loading in the patient. Conventional irrigated tip electrodes
typically operate with a flow rate of about 17 ml/minute at below
about 30 watts of RF ablation energy to about 30-50 ml/minute at
about 30 watts or greater.
[0014] Current catheters include irrigated ring electrodes that are
adapted for ablation. Such catheters include coil or single axis
sensors (SASs) for visualization of the irrigated ring electrodes.
However, the sensors are typically housed in a dedicated lumen of a
multi-lumened tubing typically used with deflectable catheters. As
lumens are needed for other components, such as puller wires, lead
wires, and/or irrigation tubing, it becomes difficult to maintain
typical catheter sizes. As catheters become more complex, more
components are incorporated and thus the allocation of space for
each component becomes more challenging.
[0015] Deflectable catheters are known. A control handle typically
provides an actuator by which a user can deflect the catheter
uni-directionally (in one direction) or bi-directionally (in
opposite directions within a plane). Linear ablation catheters are
utilized to create one or more RF lesions at a given time by means
of either uni-polar or bi-polar ablations. The size of the
resulting lesion(s) is highly dependent upon good contact of the
electrodes with the cardiac tissue. Current linear catheter designs
place the ring electrodes on a deflectable or flexible portion.
However, if the portion is too stiff, it does not conform to the
tissue and the electrodes cannot make solid contact for effective
lesions. If the region between the ring electrodes deflects too
much during catheter deflection, the ring electrodes may be pulled
away from the tissue also preventing the formation of effective
lesions.
[0016] Accordingly, it is desirable that a catheter be adapted for
mapping and ablation with improved cooling and position sensing
characteristics by providing a tip section that carries irrigated
tip and ring electrodes on a structure that is deflectable and
contractible in a more controlled and predictable manner.
SUMMARY OF THE INVENTION
[0017] The present invention is directed to a catheter having a
distal section with a spring member that allows for biased and more
predictable deflection to enable better contact between tissue and
electrodes carried on the distal section. The spring member has an
elongated hollow structure on which ring electrodes are mounted at
selected locations along the length of the structure. At least one
section of the spring member extending between the ring electrodes
has a predetermined cut pattern that includes at least one row of
alternating slots and ribs along a first side of the structure and
at least one longitudinal spine along a second side of the
structure, where the first side is relatively more compressible and
the second side is relatively less compressible, in providing the
distal section with biased deflection within a plane defined by the
two sides. Alternatively, where each section of the spring member
has two rows of slots and ribs opposing each other along a first
diameter and two longitudinal spines opposing each other along a
second diameter, the distal section has a biased deflection in two
opposing directions in a first plane defined by the first diameter
while having limited, if any, deflection in a second plane defined
by the second diameter. Where the first and second diameters are
generally perpendicular, the spring member allows the distal
section to have bi-directional deflection in the first plane while
allowing limited, if any, deflection in the second plane to
maintain torquability, axial loading capabilities, and side force
performance.
[0018] Configured for irrigation, each ring electrode carried on
the spring member is formed to provide a gap reservoir between the
ring electrode and the spring member (and its cover). For each ring
electrode, a support member is positioned in the lumen of the
spring member under the ring electrode to support it and to enable
delivery of irrigation fluid to the ring electrode. The support
member is configured with multiple lumens for components extending
through the distal section, one lumen of which receives an
irrigation tubing that defines an irrigation path for fluid
delivery to each ring electrode. A radial irrigation passage is
formed in the support member and the spring member to provide fluid
communication between the irrigation tubing and the gap reservoir
of each ring electrode.
[0019] Carried on the support member for each ring electrode is a
location sensor, e.g., a single axis coil sensor. The sensor is
carried on an outer surface of the support member so that lumens
within the support member can be used for other components such as
lead wires, thermocouple wires, puller wires, irrigation fluid,
and/or sensor cable which typically occupy less space than a
location sensor.
[0020] The catheter includes a tip electrode having a shell wall
that defines a cavity through which fluid flows and exits via fluid
ports formed in the shell wall. The cavity is sealed by an internal
member that extends into the cavity to safely house a position
sensor for the tip electrode. A proximal portion of the internal
member disperses fluid entering the tip electrode for a more
uniform flow through the cavity. As such, fluid is fed to the more
distal fluid ports in the tip electrode for more uniform cooling at
all locations on the tip electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] These and other features and advantages of the present
invention will be better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings wherein:
[0022] FIG. 1 is a perspective of a catheter according to an
embodiment of the present invention.
[0023] FIG. 2A is a side cross-sectional view of the catheter FIG.
1, showing a junction between a catheter body and a deflectable
intermediate section, taken along a first diameter.
[0024] FIG. 2B is a side cross-sectional view of the catheter of
FIG. 1, showing a junction between a catheter body and a
deflectable intermediate section, taken a long a second diameter
generally perpendicular to the first diameter.
[0025] FIG. 2C is an end cross-section view of the deflectable
intermediate section of FIG. 2B taken along line C-C.
[0026] FIG. 3 is a perspective view of a distal section of the
catheter of FIG. 1, with components broken away to show the
interior.
[0027] FIG. 3A is an end cross-sectional view of the distal section
of FIG. 3, taken along line A-A.
[0028] FIG. 3B is a side cross-sectional view of the distal section
of FIG. 3, taken along line B-B.
[0029] FIG. 4A is a perspective view of an embodiment of a spring
member.
[0030] FIG. 4B is a perspective view of another embodiment of a
spring member.
[0031] FIG. 4C is an end cross-sectional view of the spring member
of FIG. 4B, taken along line C-C.
[0032] FIG. 5A is a side sectional view of an embodiment of a
spring member.
[0033] FIG. 5B is a side sectional view of another embodiment of a
spring member.
[0034] FIG. 5C is a detailed side view of an embodiment of a slot
of a spring member.
[0035] FIG. 5D is a detailed side view of another embodiment of a
slot of a spring member.
[0036] FIG. 5E is a detailed side view of yet another embodiment of
a slot of a spring member.
[0037] FIG. 6 is a perspective view of an embodiment of a ring
electrode.
[0038] FIG. 7 is a side cross-sectional view of the tip electrode
of FIG. 3.
[0039] FIG. 7A is an end cross-sectional view of the tip electrode
of FIG. 7, taken along line A-A.
[0040] FIG. 7B is an end cross-sectional view of the tip electrode
of FIG. 7, taken along line B-B.
[0041] FIG. 7C is an end cross-sectional view of the tip electrode
of FIG. 7, taken along line C-C.
[0042] FIG. 8 is a side cross-sectional view of the catheter of
FIG. 1, showing a junction between an intermediate section and a
distal section, taken along a diameter.
DETAILED DESCRIPTION OF THE INVENTION
[0043] FIG. 1 illustrates an embodiment of a catheter 10 carrying
irrigated tip and ring electrodes with improved deflection
characteristics. The catheter has an elongated catheter body 12
with proximal and distal ends, an intermediate deflectable section
14 at the distal end of the catheter body 12, and a distal section
15 which carries an irrigated tip electrode 17 and a plurality of
irrigated ring electrodes 21. The catheter also includes a control
handle 16 at the proximal end of the catheter body 12 for
controlling deflection of at least the intermediate section 14.
Advantageously, the distal section 15 has a spring member that
enables a more controlled and biased deflection, including uni- or
bi-directional deflection within a single plane. Along its length,
the spring member houses discrete support members, each of which
supports a respective ring electrode while allowing the spring
member as a whole to deflect more predictably in enabling better
contact between the tissue and the electrodes for forming more
effective lesions.
[0044] With reference to FIGS. 2A and 2B, the catheter body 12
comprises an elongated tubular construction having a single, axial
or central lumen 18. The catheter body 12 is flexible, i.e.,
bendable, but substantially non-compressible along its length. The
catheter body 12 can be of any suitable construction and made of
any suitable material. A presently preferred construction comprises
an outer wall 20 made of polyurethane or PEBAX. The outer wall 20
comprises an imbedded braided mesh of stainless steel or the like
to increase torsional stiffness of the catheter body 12 so that,
when the control handle 16 is rotated, the intermediate section 14
of the catheter 10 will rotate in a corresponding manner.
[0045] The outer diameter of the catheter body 12 is not critical,
but is preferably no more than about 8 french, more preferably 7
french. Likewise the thickness of the outer wall 20 is not
critical, but is thin enough so that the central lumen 18 can
accommodate puller members (e.g., puller wires), lead wires, and
any other desired wires, cables or tubings. If desired, the inner
surface of the outer wall 20 is lined with a stiffening tube 22 to
provide improved torsional stability. A disclosed embodiment, the
catheter has an outer wall 20 with an outer diameter of from about
0.090 inch to about 0.94 inch and an inner diameter of from about
0.061 inch to about 0.065 inch.
[0046] Distal ends of the stiffening tube 22 and the outer wall 20
are fixedly attached near the distal end of the catheter body 12 by
forming a glue joint 23 with polyurethane glue or the like. A
second glue joint (not shown) is formed between proximal ends of
the stiffening tube 20 and outer wall 22 using a slower drying but
stronger glue, e.g., polyurethane.
[0047] Components that extend between the control handle 16 and at
least the intermediate deflectable section 14 pass through the
central lumen 18 of the catheter body 12. These components include
lead wires 40 for the tip electrode 17 and ring electrodes 21 on
the distal section 15, an irrigation tubing 38 for delivering fluid
to the distal section 15, cables 48 for position/location sensors
36R and 36T located in the tip electrode and the ring electrodes, a
pair of puller wires 26 for bi-directional deflection of at least
the intermediate section 14, and a pair of thermocouple wires 41,
45 to sense temperature at the distal section 15.
[0048] Illustrated in FIGS. 2A, 2B and 2C is an embodiment of the
intermediate section 14 which comprises a short section of tubing
19. The tubing also has a braided mesh construction with multiple
off-axis lumens, for example five lumens 31, 32, 33, 34 and 35.
Each of off-axis, diametrically opposing first and second lumens
31, 32 carries a puller wire 26. A third off-axis lumen 33 carries
the lead wires 40 and the thermocouple wires 41 and 45. A fourth
off-axis lumen 34 carries the sensor cables 48. A fifth on-axis
lumen 35 carries the irrigation tubing 38.
[0049] The tubing 19 of the intermediate section 14 is made of a
suitable non-toxic material that is more flexible than the catheter
body 12. A suitable material for the tubing 19 is braided
polyurethane, i.e., polyurethane with an embedded mesh of braided
stainless steel or the like. The size of each lumen is not
critical, but is sufficient to house the respective components
extending therethrough.
[0050] A means for attaching the catheter body 12 to the
intermediate section 14 is illustrated in FIGS. 2A and 2B. The
proximal end of the intermediate section 14 comprises an outer
circumferential notch 24 that receives an inner surface of the
outer wall 20 of the catheter body 12. The intermediate section 14
and catheter body 12 are attached by glue or the like.
[0051] If desired, a spacer (not shown) can be located within the
catheter body 12 between the distal end of the stiffening tube 22
(if provided) and the proximal end of the intermediate section 14.
The spacer provides a transition in flexibility at the junction of
the catheter body 12 and intermediate section 14, which allows this
junction to bend smoothly without folding or kinking. A catheter
having such a spacer is described in U.S. Pat. No. 5,964,757, the
disclosure of which is incorporated herein by reference.
[0052] Each puller wire 26 is preferably coated with Teflon.RTM..
The puller wires 26 can be made of any suitable metal, such as
stainless steel or Nitinol and the Teflon coating imparts lubricity
to the puller wire. The puller wire preferably has a diameter
ranging from about 0.006 to about 0.010 inch.
[0053] As shown in FIG. 2B, a portion of each puller wire 26
extending through the catheter body 12 passes through a respective
compression coil 37 in surrounding relation to its puller wire 26.
The compression coil 37 extends from about the proximal end of the
catheter body 12 to about the proximal end of the intermediate
section 14. The compression coil 37 is made of any suitable metal,
preferably stainless steel, and is tightly wound on itself to
provide flexibility, i.e., bending, but to resist compression. The
inner diameter of the compression coil is preferably slightly
larger than the diameter of the puller wire 26. Within the catheter
body 12, the outer surface of the compression coil 37 is also
covered by a flexible, non-conductive sheath 39 (FIG. 2B), e.g.,
made of polyimide tubing. As shown in FIGS. 2B and 2C, a portion of
each puller wire 26 extending through the intermediate section 14
is covered by a nonconductive protective sheath 47.
[0054] Proximal ends of the puller wires 26 are anchored in the
control handle 16. Distal ends of the puller wires 26 may be
anchored near the distal end of the intermediate deflectable
section 14 or in the distal section 15 as desired or appropriate.
Separate and independent longitudinal movement of the puller wires
26 relative to the catheter body 12 which results in deflection of
the intermediate section 14 and/or tip section 15 is accomplished
by suitable manipulation of the control handle 16.
[0055] In the illustrated embodiment of FIG. 1, the control handle
16 has a deflection actuator 50 that actuates the puller wires for
bi-directional deflection. The control handle also includes a
deflection tension knob 52 that enables the user to adjust the ease
by which the deflection actuator 50 can be rotated. A suitable
deflection assembly and control handle are described in co-pending
U.S. application Ser. No. 12/346,834, filed Dec. 30, 2008, entitled
DEFLECTABLE SHEATH INTRODUCER, the entire disclosure of which is
hereby incorporated by reference. Other suitable deflection
assemblies are described in co-pending U.S. application Ser. No.
12/211,728, filed Sep. 16, 2008, entitled CATHETER WITH ADJUSTABLE
DEFLECTION SENSITIVITY, and U.S. application Ser. No. 12/127,704,
filed May 27, 2008, entitled STEERING MECHANISM FOR BI-DIRECTIONAL
CATHETER, the entire disclosures of both of which are hereby
incorporated by reference.
[0056] With reference to FIG. 3, at the distal end of the
intermediate section 14 is the distal section 15 that includes the
tip electrode 17 and a plurality of irrigated ring electrodes 21
mounted at selected locations along the length of the distal
section 15. Notwithstanding the ring electrodes 21, the distal
section 15 advantageously has a flexible spring member 60 that
allows for controlled or biased deflection in a single plane, in at
least one direction, if not in two opposing directions, while
allowing only limited deflection outside of the plane or in
perpendicular directions to maintain torquability, axial loading
capabilities, and side force performance. The spring member is
constructed of a suitable material with flexibility and shape
memory, such as nitinol or spring steel.
[0057] As illustrated in FIG. 4A, the spring member 60 has an
elongated tubular form defining a longitudinal axis 61. The tubular
form provides a central lumen 62 extending therethrough. In
accordance with a feature of the present invention, the spring
member 60 has a controlled or biased deflection that is enabled by
at least one section 58 with defined compression characteristics
enabled by a predetermined cut pattern, and at least one section 59
that is devoid of any cut pattern for carrying at least one ring
electrode. The cut pattern of the section 58 includes a plurality
of radial slots 63 with radial ribs 64 that extend from at least
one spine 65 spanning the length of the tubular form. The slots 63
are cut or otherwise formed transversely, if not perpendicularly,
to the longitudinal axis 61 of the tubular form, with each rib 64
having a generally uniform shape, depth D, width W and spacing S.
These parameters may be varied as desired or appropriate for
different deflection or bending characteristics. Illustrated herein
are a few of the endless possible shapes of the slots, for example,
trapezoidal (FIG. 5C), triangular (FIG. 5D), and circular or
keyhole (FIG. 5E), and different depths, for example, less than
half of the diameter of the tubular structure (FIG. 5C), about half
of the diameter (FIG. 5D), or greater than half of the diameter
(FIG. 5E). It is understood that tubular form itself may include
tubes with circular or noncircular cross-sections.
[0058] The spring member 60 extends the length of the tip section
15 generally between a distal end of the intermediate deflectable
section 14 and a proximal end of the tip electrode. The length may
range between about 1.0 cm and 10.0 cm, preferably about 2.0 cm and
5.0 cm, and more preferably about 3.0 cm. In the illustrated
embodiment, the spring member 60 has three pre-cut sections 58 and
two uncut sections 59.
[0059] The distal section 15 as supported by the spring member 60
in its neutral configuration extends linearly (solid line in FIG.
1). The controlled or biased deflection (broken line in FIG. 1) is
enabled by the spring member 60 having at least one side 66 along
its length that is more elastically compressible as shown in FIG.
4A. The side 66 patterned by the slots 63 and ribs 64 is relatively
more elastically compressible and the side 67 of the spine 65 is
relatively less elastically compressible, if not resistant to
compression. And, where the sides 66 and 67 are generally opposite
to each other, as illustrated in FIG. 4A, the spring member 60 is
biased to deflect within a single plane defined by the two sides 66
and 67 (namely, the YZ plane in FIG. 4A), and in one direction in
the single plane (namely, toward the +Z axis).
[0060] In an alternate embodiment, as illustrated in FIGS. 4B and
4C, the spring member 60 has two rows of radial slots 63a, 63b and
ribs 64a, 64b, with each row extending along a respective side 66a,
66b that is relatively more elastically compressible, and two
spines 65a, 65b with each spine extending along a respective side
67a, 67b that is relatively less elastically compressible, if not
compression-resistant. And, where the two more compressible sides
66a, 66b are generally opposite of each other (separated by a
radial angle of about 180 degrees) along a first diameter 54, the
two less compressible sides 67a, 67b are generally opposite of each
other (separated by a radial angle of about 180 degrees) along a
second diameter 55 and the first and second diameters are generally
perpendicular (separated by a radial angle of about 90 degrees),
the spring member 60 is biased for deflection in a single plane
(namely, the XY plane in FIG. 4B), and in opposite directions (or
bi-directionally) within the single plane (namely, toward the +X
axis and the -X axis). FIG. 4B illustrates the embodiment of the
spring member 60 employed in the distal section 15 in FIG. 3.
[0061] In FIGS. 4A and 4B, the slots 63a and ribs 64a are aligned
respectively with the slots 63b and ribs 64b, as better shown in
FIG. 5A. However, it is understood that the slots and ribs of
different rows can be offset from each other such that they present
an alternating pattern, as shown in FIG. 5B.
[0062] It is understood by one of ordinary skill in the art that
deflection characteristics of a spring member depends on various
factors, including plurality, depth D, separation S, width W of any
row of slots/ribs, especially where a spring member has more than
one row of slots/ribs with different pluralities, depths and/or
widths such that the spines have different widths and/or are not
opposite of each other such that their radial separation angle is
greater or less than about 180 degrees.
[0063] The integrity of the spring member 60 is maintained by
including a flexible cover 78 over the spring member, as shown in
FIG. 3. The cover is preferably made of a biocompatible plastic or
polymer, such as PELLETHANE or PEBAX, or polyolefin, with a
flexibility about equal to that of the spring member. The cover
should not hinder the ability of the spring member to bend. The
cover protects the spring member against electrical conductivity,
particularly where the structure is made of Nitinol or another
metal, and also protects against blood and other bodily fluids from
entering and clogging the slots. The cover 78 can be longer than
the member 60 and has proximal and distal ends extending beyond the
member's proximal and distal ends, respectively. The cover can be
secured in place over the member by any suitable methods, such as
by gluing, thermal bonding and/or heat shrinking.
[0064] At least one ring electrode 21 is carried on the spring
member 60 over the cover 78. In the illustrated embodiment, there
are three ring electrodes 21a, 21b, 21c, although it is understood
that the plurality can range between about 2 and 10, and preferably
between about 3 and 5. At each ring electrode 21, a support member
56 is positioned in the central lumen 62 of the spring member 60 to
support its respective ring electrode. The support member 56 may be
constructed of a sufficiently rigid plastic material suitable for
housing position/location sensors, such as SASs, to regulate
irrigation flow to irrigated ring electrodes 21 and to act as a
substrate on which its respective ring electrode is mounted. With
reference to FIGS. 3, 3A and 3B, each support member 56 has a
similar construction with a plurality of lumens, including at least
lumens 73, 74, 75 that preferably are in axial alignment with the
lumens 33, 34 and 35, respectively, of the tubing 19 of the
deflectable intermediate section 14, to avoid sharp bends or kinks
in the components extending through these lumens. In the
illustrated embodiment of FIG. 3A, each member 56 includes an
off-axis lumen 73 for electrode lead wires 40 and thermocouple
wires 41, 45, an off-axis lumen 74 for sensor cables 48, and a
center lumen 75 for irrigation fluid. The member may also include
off-axis, diametrically opposing lumens 71 and 72 for the puller
wires 26 in an embodiment where the puller wires extend into the
distal section 15.
[0065] The length of each support member 56 can range between about
0.2 cm and 1.0 cm, and preferably about 0.5 cm, which is generally
about equal to the length of a ring electrode. The support members
56 may be fabricated using micro machining, micro molding, or
machining of extrusions using plastic materials which are
sufficiently rigid and sufficiently biocompatible for contact with
blood.
[0066] A circumferential groove 80 is formed in the outer surface
of each support member 56. In the illustrated embodiment of FIGS. 3
and 3B, the groove 80 is formed near a proximal end of the support
member 56, although it is understood that the groove 80 may be
formed near a distal end of the support member 56. The groove 80 is
provided on the support member 56 to carry a wire coil of a sensor
36R for each irrigated ring electrode 21. The wire coil (e.g., a
single-axis sensor "SAS") is advantageously wound in the groove 80
on the support member 56 so that it does not occupy any space in
the distal section 15 beyond that already occupied by the support
member 56. Moreover, the wire coil does not occupy any lumens of
the support member 56. Rather, the lumens are available to other
components, including lead wires, thermocouple wires, irrigation
tubing and puller wires, that do not necessarily require dedicated
lumens and/or larger lumens as a typical sensor would.
[0067] A pair of sensor cables 48 are provided for each coil sensor
36R of a ring electrode 21, with each end of the coil being
connected to one of the pair of cables (FIG. 3B). The sensor cables
48 for each coil of the ring electrodes 21 (and for the position
sensor 36T in the tip electrode 17) extend through the fourth lumen
74 of the support member 56. A passage 82 (FIG. 3B) through the
support member 56 allowing communication between the lumen 74 and
the groove 80 is provided at each end of the groove. One sensor
cable 48 is fed through a respective passage 82 for connection to
each end of the wire coil of the sensor 36R, so each sensor 36R has
a pair of sensor cables connected to it.
[0068] Each of the irrigated ring electrodes 21 is adapted for
ablation and irrigation and has a similar structure to each other.
The ring electrodes may be made of any suitable noble metal, such
as platinum or gold, preferably a combination of platinum and
iridium or gold and platinum. In the illustrated embodiment of FIG.
6, the ring electrode 21 is generally cylindrical with a length
greater than its diameter and has a distal end 90, a mid-section 92
and a proximal end 94. With a wall 96 of a generally uniform
thickness throughout its length, the ring electrode 21 has a larger
diameter in the mid-section 92 than in the distal and proximal ends
90, 94. As such, the wall bulges outwardly in the mid-section with
curved transitional regions 98 on each side of the mid-section 92
so as to provide the ring electrode with an atraumatic profile
without corners or sharp edges. With reference to FIGS. 3A and 3B,
a reservoir in the shape of an annular gap G is formed between an
inner surface of the mid-section 92 and an outer surface of the
spring member 60 (inclusive of the cover 78). A plurality of
irrigation apertures 100 are formed in the wall 96 of the
mid-section 92 to promote flow in a radial direction, and of the
curved transitional regions 98 to promote flow in a more axial
direction. In the latter instance, the apertures 100 in the curved
transitional regions 98 are particularly effective in minimizing
charring and coagulation which are likely to be "hot spots"
resulting from higher current densities due to transitions in the
electrode profile. In that regard, the curved transitional regions
98 may have a higher aperture density and/or apertures with a
greater cross-section so as to minimize the occurrence of hot
spots. Suitable ring electrodes are described in US Patent
Application Publication No. US2010/0168548 A1, and U.S. patent
application Ser. No. 13/174,742, filed Jun. 30, 2011, the entire
content of both of which are incorporated herein by reference.
[0069] The ring electrodes 21 can be made of any suitable solid
conductive material, such as platinum or gold, preferably a
combination of platinum and iridium. The ring electrodes can be
mounted onto the support members 56 with glue or the like. The
rings electrodes may be uni-polar or bi-polar. In the illustrated
embodiment, there are a distal monopolar ring electrode and a
proximal pair of bi-polar ring electrodes. Each ring electrode is
connected to a respective lead wire 40R.
[0070] Each lead wire 40R is attached to its corresponding ring
electrode 21 by any suitable method. A preferred method for
attaching a lead wire to a ring electrode involves first making a
small hole through the wall of the non-conductive covering or
tubing. Such a hole can be created, for example, by inserting a
needle through the support member 56 and its cover 78 and heating
the needle sufficiently to form a permanent hole. The lead wire is
then drawn through the hole by using a microhook or the like. The
end of the lead wire is then stripped of any coating and welded to
the underside of the ring electrode, which is then slid into
position over the hole and fixed in place with polyurethane glue or
the like.
[0071] As seen in FIGS. 3 and 3A, at least one opening 77 is formed
in each portion of the irrigation tubing 38 extending through each
ring electrode 21. The opening 77 communicates with a radial
passage 76 formed in the spring member 60, its cover 78, and the
support member 56 below each ring electrode 21. The passage 76
extends radially from the lumen 75 of the support member 56,
through the support member 56, the spring member 60 and the cover
78 to provide fluid communication between the irrigation tubing 38
and the gap reservoir G of each ring electrode 21. Each passage 76
is formed at a predetermined radial angle (FIG. 3A) so that the
passages 76 do not intersect or otherwise interfere with the
off-axis lumens in each of the support member 56. Advantageously,
the passages 76 can be precisely dimensioned so as to regulate the
volumetric flow rate of the irrigation fluid delivered to the gap
reservoirs G.
[0072] The length of a ring electrode 21 is about equal to the
length of a support member 56 so that the support member is covered
in its entirety by its respective ring electrode. The groove 80 and
the coil sensor 36R are positioned under a section 59 of the spring
member so that the coil sensor 36R is isolated from and not exposed
to irrigation fluid in the gap reservoir G of the ring electrode.
The distal and proximal ends 90 and 94 of the ring electrodes are
sized relative to the support members 56 so as to form a fluid
tight seal enclosing the gap reservoir G.
[0073] With reference to FIGS. 3 and 7, the tip electrode 17 houses
an electromagnetic position sensor 36T in a distal and on-axis
location relative to the tip electrode. The tip electrode is
configured to promote turbulent flow and dispersion of irrigation
fluid for increased thermal transfer from the tip electrode to the
fluid and thus with lower flow rates resulting in lower fluid load
in the patient. Fluid, e.g., saline or heparinized saline, can be
delivered to the ablation site from the tip electrode to cool
tissue, reduce coagulation and/or facilitate the formation of
deeper lesions. It is understood that other fluids can be delivered
as well, including any diagnostic and therapeutic fluids, such as
neuroinhibitors and neuroexcitors.
[0074] The tip electrode 17 has a two-piece configuration that
includes an electrically conductive dome shell 110 and an internal
member 112. The shell 110 is generally cylindrical defining a
chamber 113 between a closed distal end 114 and an open proximal
end (or neck) 116. The neck 116 connected with a distal end of the
nonconductive cover 85 of the connection section 81. The internal
member 112 is configured to fit inside the shell 110 with an
elongated distal section 118 that sits inside the chamber 113, and
a proximal core 120 that plugs the neck 116. The core 120 and the
distal section 118 are connected by a stem 119. The distal end 114
of the shell 110 and the distal section 118 of the internal member
112 are relatively sized so that the chamber 113 functions as a tip
reservoir for irrigation fluid entering the tip electrode 17. Fluid
passages 124 are formed in the core 120 to provide fluid
communication from the irrigation connector lumen 86 to the chamber
113.
[0075] The shell 110 is constructed of a biocompatible metal,
including a biocompatible metal alloy. A suitable biocompatible
metal alloy includes an alloy selected from stainless steel alloys,
noble metal alloys and/or combinations thereof. In one embodiment,
the shell is constructed of an alloy comprising about 80% palladium
and about 20% platinum by weight. In an alternate embodiment, the
shell is constructed of an alloy comprising about 90% platinum and
about 10% iridium by weight. The shell can formed by deep-drawing
manufacturing process which produces a sufficiently thin but sturdy
wall that is suitable for handling, transport through the patient's
body, and tissue contact during mapping and ablation procedures. A
deep drawn shell is also suitable for electrical discharge
machining (EDM) process to form a large plurality of through-holes
or ports 122 in the shell that allow fluid communication between
the chamber 113 and outside the shell 110.
[0076] The elongated distal section 118 of the internal member 112
is configured to protect and encapsulate the tip electrode sensor
36T which is positioned centrally within the chamber 113 so that
the sensor is distal and centered in the tip electrode for optimum
performance. In the disclosed embodiment, the tip electrode sensor
36T is an electromagnetic (EM) tri-axis location/position sensor
using three coils that give rise to signals that are used to
determine the position of the device relative to a frame of
reference that is fixed either externally to the body or to the
heart itself. The EM sensor may be active or passive and may
operate by generating or receiving electrical, magnetic or
ultrasonic energy fields or other suitable forms of energy known in
the art.
[0077] The core 120 of the internal member 112 sits in the neck 116
of the shell 110. The core is advantageously configured as a
diffuser that provides multiple fluid passages or channels 124
through the neck 116 so as to diffuse the irrigation fluid. As
such, the diffusing core 120 provides increased turbulence and a
more uniform flow rate in the chamber 113 and thus more increased
convective cooling on the shell 110. Irrigation in the tip
electrode 17 is thus more uniform throughout the length of the tip
electrode. The internal member 112 effectively counters the
tendency for the velocity of the fluid entering the tip electrode
17 to otherwise carry the fluid to the more distal ports and starve
the more proximal ports 122.
[0078] On a proximal surface of the core 120, a center opening 130
(FIG. 7A) connects a distal end of the irrigation tubing 38 with
the channels 124 in the core 120. Within the core 120, the channels
124 intersect each other at varying degrees throughout the tip
electrode (FIG. 7B), and then separate into distinct channels (FIG.
7C.) In the illustrated embodiment, the channels 124 have a
circular cross-section, however, it is understood that the
cross-section may be polygonal or any noncircular shape and can
have any suitable size, as appropriate. The core 120 is made of
electrically conductive material so as to be conductive with the
shell 110 when the core 120 is energized by its lead wire 40T, but
the distal section 118 can be made of plastic such as polyimide, or
an adhesive or sealant, such as epoxy, to encapsulate the tip
electrode sensor 36T.
[0079] Also on the proximal surface of the core 120 are blind holes
132, 133 (FIGS. 3 and 7A) for the tip electrode lead wire 40T, the
thermocouple wires 41, 45. A longitudinal through-hole 134
extending through the core 120, the stem 119 and into the distal
section 118 of the internal member 112 is provided for the cable
48T for the tip electrode sensor 36T. The through-hole or passage
134 is routed from a proximal off-axis location in the core 120 to
a distal on-axis location in the stem 119 without interfering with
the fluid diffusing channels 124.
[0080] A distal end of each puller wire 26 has a T-bar 105. In the
illustrated embodiment of FIG. 8, the T-bars are anchored in the
first and second lumens 31, 32 of the tubing 19 at or near the
distal end of the intermediate section 14. However, it is
understood that the distal ends of the puller wires 26 may be
soldered in diametrically-opposing off axis blind-holes in the
proximal surface of the core 120 (FIG. 3) of the tip electrode 17,
as desired or appropriate.
[0081] In accordance with another feature of the present invention,
fluid is delivered through the catheter body 12 (FIG. 2A), through
the intermediate section 14 (FIG. 2A), and through the distal
section 15 via the irrigating tubing 38 (FIG. 3B) which extends
through the lumen 75 of the support members 56. A portion of the
fluid enters the reservoir gap G of each ring electrode via the
opening 77 and the passage 76 (FIG. 3C), and exits the ring
electrodes via the apertures 100. Another portion of the fluid
continues to the tip electrode 17 via the irrigation tubing 38 and
the diffusing channels 124 (FIG. 5), where it enters the chamber
113 and exits the tip electrode via irrigation ports 122. In the
tip electrode 17, the fluid has a flow that is more uniform and
equal in the radial direction through the diffusing channels 124
which in turn provides increased turbulence and a more uniform flow
rate in the chamber 113 and thus more increased convective cooling
on the shell 110. Irrigation in the tip electrode is thus more
uniform throughout the length of the tip electrode. Suitable tip
electrodes are described in U.S. patent application Ser. No.
12/767,763, filed Apr. 26, 2010 entitled "IRRIGATED CATHETER WITH
INTERNAL POSITION LOCATION SENSOR," the entire disclosure of which
is incorporated herein by reference.
[0082] The lead wires 40T and 40R pass through the lumen 18 of the
catheter body 12 (FIG. 2A), the lumen 33 of the intermediate
section 14 (FIG. 2A), and the lumen 73 of the support members 56
(FIG. 3B) throughout the distal section 15. The portion of the lead
wires extending through the central lumen 18 of the catheter body
12, and proximal portion of the lumen 33 can be enclosed within a
protective sheath 67 (FIG. 2A), which can be made of any suitable
material, preferably polyimide. The protective sheath is anchored
at its distal end to the proximal end of the intermediate section
14 by gluing it in the lumen 33 with polyurethane glue or the like.
Each electrode lead wire has its proximal end terminating in a
connector (not shown) at the proximal end of the control handle 16.
The tip electrode 17 and ring electrodes 21 are electrically
connected to a source of ablation energy by the lead wires 40T and
40R via the connector. The wires may also be electrically connected
to an appropriate mapping or monitoring system via the
connector.
[0083] The preceding description has been presented with reference
to certain exemplary embodiments of the invention. Workers skilled
in the art and technology to which this invention pertains will
appreciate that alterations and changes to the described structure
may be practiced without meaningfully departing from the principal,
spirit and scope of this invention. It is understood that the
drawings are not necessarily to scale. Certain features, including
the cut pattern of slots, ribs and spine, may be exaggerated for
clarity purposes. Accordingly, the foregoing description should not
be read as pertaining only to the precise structures described and
illustrated in the accompanying drawings. Rather, it should be read
as consistent with and as support for the following claims which
are to have their fullest and fairest scope.
* * * * *