U.S. patent application number 15/338600 was filed with the patent office on 2017-02-16 for systems and methods for making and using medical ablation systems having mapping catheters with improved anchoring ability.
The applicant listed for this patent is Boston Scientific Scimed Inc.. Invention is credited to Isaac J. Kim, Josef V. Koblish, David L. McGee.
Application Number | 20170042601 15/338600 |
Document ID | / |
Family ID | 43586818 |
Filed Date | 2017-02-16 |
United States Patent
Application |
20170042601 |
Kind Code |
A1 |
Kim; Isaac J. ; et
al. |
February 16, 2017 |
SYSTEMS AND METHODS FOR MAKING AND USING MEDICAL ABLATION SYSTEMS
HAVING MAPPING CATHETERS WITH IMPROVED ANCHORING ABILITY
Abstract
A mapping catheter includes an elongated body for inserting into
patient vasculature. A distal end of the elongated body includes a
distal portion that includes a plurality of electrodes, a proximal
portion disposed proximal to the distal portion, and a
reduced-dimension portion disposed between the proximal and distal
portions. The distal end is formed, at least in part, from a memory
shape material that bends into a preformed shape upon release from
a confined space. The preformed shape includes a first loop formed,
at least in part, by the distal portion. The first loop is
transverse to a longitudinal axis of the proximal portion. The
reduced-dimension portion is configured and arranged to bend such
that the reduced-dimension section advances distally through the
first loop when the first loop is held in a fixed position and a
force is applied distally along the longitudinal axis of the
proximal portion.
Inventors: |
Kim; Isaac J.; (San Jose,
CA) ; Koblish; Josef V.; (Sunnyvale, CA) ;
McGee; David L.; (San Miguel, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Boston Scientific Scimed Inc. |
Maple Grove |
MN |
US |
|
|
Family ID: |
43586818 |
Appl. No.: |
15/338600 |
Filed: |
October 31, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14282726 |
May 20, 2014 |
9480521 |
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15338600 |
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13770847 |
Feb 19, 2013 |
8731631 |
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14282726 |
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12854692 |
Aug 11, 2010 |
8380275 |
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13770847 |
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61233965 |
Aug 14, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2018/0022 20130101;
A61B 2018/00166 20130101; A61B 5/0036 20180801; A61B 5/0538
20130101; A61B 2018/00577 20130101; A61B 2018/1407 20130101; A61B
5/6857 20130101; A61B 18/1492 20130101; A61B 2018/0212 20130101;
A61B 2017/00867 20130101; A61B 2018/00375 20130101; A61B 5/6856
20130101; A61B 2018/00916 20130101; A61B 18/02 20130101; A61B 18/18
20130101; A61B 5/4836 20130101; A61B 2017/00053 20130101; A61B
5/6853 20130101; A61B 5/0422 20130101; A61B 2018/00642
20130101 |
International
Class: |
A61B 18/02 20060101
A61B018/02; A61B 5/00 20060101 A61B005/00; A61B 5/053 20060101
A61B005/053; A61B 18/14 20060101 A61B018/14; A61B 5/042 20060101
A61B005/042 |
Claims
1. An ablation system comprising: an ablation catheter having a
distal portion and a proximal portion, the ablation catheter
configured and arranged for insertion into patient vasculature; an
expansion element coupled to the distal portion of the ablation
catheter, the expansion element configured and arranged for
ablating patient tissue; a mapping catheter comprising an elongated
body insertable through the catheter and the expansion element, the
elongated body comprising a distal end that is extendable from a
distal end of the expansion element, the distal end of the
elongated body comprising a plurality of electrodes, wherein the
distal end is formed, at least in part, from a shape memory
material that bends into a preformed shape upon release from a
confined space, the preformed shape comprising a loop transverse to
a longitudinal axis of the elongated body; and a control module
coupled to the ablation catheter and the mapping catheter, the
control module configured and arranged for controlling mapping of
electrical activity by the mapping catheter and ablation of patient
tissue by the expansion element.
2. The ablation system of claim 1, wherein when the mapping
catheter is extended distal of the expansion element, the distal
end of the mapping catheter assumes its preformed loop shape,
wherein the plurality of electrodes are disposed on the loop.
3. The ablation system of claim 2, wherein the mapping catheter has
eight electrodes disposed on the loop.
4. The ablation system of claim 1, wherein the expansion element is
a cryo balloon.
5. The ablation system of claim 4, wherein the ablation catheter
defines at least one coolant outtake region extending along at
least a portion of the ablation catheter.
6. The ablation system of claim 1, wherein the preformed shape is a
closed loop.
7. The ablation system of claim 1, wherein the control module
includes one or more sensors for monitoring one or more conditions
within the ablation catheter.
8. The ablation system of claim 1, wherein the expansion element
includes an inner layer and an outer layer.
9. A method of ablating a pulmonary vein, the method comprising:
guiding an ablation catheter into proximity of an ostium of a
pulmonary vein, the ablation catheter including an expansion
element and a mapping catheter, the mapping catheter comprising an
elongated body insertable through the catheter and the expansion
element, the elongated body comprising a distal end that is
extendable from a distal end of the expansion element, the distal
end of the elongated body comprising a plurality of electrodes,
wherein the distal end is formed, at least in part, from a shape
memory material that bends into a preformed shape upon release from
a confined space, the preformed shape comprising a loop transverse
to a longitudinal axis of the elongated body; extending the mapping
catheter through the distal end of the expansion element and
allowing the distal end of the elongated body to form its preformed
loop shape; placing the loop shaped distal end of the mapping
catheter into contact with the pulmonary vein and mapping
electrical activity within walls of the pulmonary vein with the
electrodes; expanding the expansion element and advancing it into
contact with the ostium of the pulmonary vein; and ablating the
pulmonary vein ostium with the expansion element.
10. The method of claim 9, wherein the expansion element is
expanded with coolant, and ablating the pulmonary vein ostium
includes cryoablation.
11. The method of claim 9, wherein the mapping catheter distal end
forms a closed loop upon being extended from the expansion
element.
12. The method of claim 9, wherein the ablation catheter defines at
least one coolant outtake region extending along at least a portion
of the ablation catheter, and the steps of expanding the expansion
element and ablating include flowing coolant into the expansion
element and withdrawing coolant from the coolant outtake region
such that the expansion element expands and freezes tissue in
contact with an outer surface of the expansion element.
13. The method of claim 12, wherein the ablation catheter includes
one or more sensors for monitoring one or more conditions within
the ablation catheter, wherein ablating includes monitoring the one
or more conditions and adjusting the flow of coolant in response to
the one or more conditions.
14. The method of claim 9, further comprising mapping electrical
activity within the walls of the pulmonary vein after the ablation
step.
15. The method of claim 10, wherein the ablation catheter includes
a control module, the control module configured and arranged for
controlling mapping of electrical activity by the mapping catheter
and flow of coolant into and out of the expansion element to
control ablation of patient tissue by the expansion element.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/282,726, filed May 20, 2014, which is a
continuation of Ser. No. 13/770,847, filed Feb. 19, 2013, now U.S.
Pat. No. 8,731,631; which is a continuation of U.S. patent
application Ser. No. 12/854,692, filed Aug. 11, 2010, now U.S. Pat.
No. 8,380,275; which claims the benefit of priority to U.S.
Provisional Application No. 61/233,965, filed Aug. 14, 2009, the
entire disclosures of which are hereby incorporated by
reference.
TECHNICAL FIELD
[0002] The present invention is directed to the area of medical
ablation systems and methods of making and using the medical
ablation systems. The present invention is also directed to medical
ablation systems having mapping catheters configured and arranged
for facilitating the anchoring ability of the mapping catheters to
patient tissue, as well as systems and methods for making and using
the medical ablation systems and mapping catheters.
BACKGROUND
[0003] Medical ablation systems (e.g., cryoablation systems,
radio-frequency ablation systems, or the like) have proven
therapeutic. Cryoablation systems can be used to form cold-induced
lesions on patient tissue. Cryoablation systems have been used to
reduce, or even eliminate, undesired electrical activity between
adjacent cardiac tissues of the heart (arrhythmias). Radio
frequency ablation systems ("RF ablation systems") use microwave
energy to form heat-induced lesions on patient tissue and can also
be used to treat some of the same conditions as cryoablation
systems, including arrhythmias.
[0004] One common type of arrhythmia, atrial fibrillation, is a
result of abnormal electrical signals interfering with the normal
electrical signal propagation along the tissues of the heart.
Atrial fibrillation often originates near the ostia of the
pulmonary veins. Mapping catheters can be used to locate the
abnormal electrical signals and medical ablation systems ("ablation
systems") can be used to form lesions on patient tissue through
which the abnormal electrical signals are propagated (e.g., tissue
along the inner walls of the ostia (where the pulmonary veins open
into the left atrium of the heart), or in proximity to the ostia).
The cold-induced (or heat-induced) lesions can effectively block
the initiation or propagation of the abnormal electrical signals,
thereby preventing the abnormal electrical signals from interfering
with the normal electrical signal propagation along the tissues of
the heart.
SUMMARY
[0005] In one embodiment, a mapping catheter includes an elongated
body configured and arranged for insertion into patient
vasculature. A distal end of the elongated body includes a distal
portion that includes a plurality of electrodes, a proximal portion
disposed proximal to the distal portion, and a reduced-dimension
portion disposed between the proximal portion and the distal
portion. The reduced-dimension portion has a cross-sectional
dimension that is less than corresponding cross-sectional
dimensions of both a proximally-positioned adjacent section of the
distal portion and a distally-positioned adjacent section of the
proximal portion. The distal end is formed, at least in part, from
a memory shape material that bends into a preformed shape upon
release from a confined space. The preformed shape includes a first
loop formed, at least in part, by the distal portion. The first
loop is transverse to a longitudinal axis of the proximal portion.
The reduced-dimension portion is configured and arranged to bend
such that the reduced-dimension section advances distally through
the first loop when the first loop is held in a fixed position and
a force is applied along the longitudinal axis of the proximal
portion in a distal direction.
[0006] In another embodiment, an ablation system includes an
ablation catheter, a guide tube, an expansion element, a mapping
catheter, and a control module. The ablation catheter has a distal
portion, a proximal portion, and a longitudinal length. The
ablation catheter is configured and arranged for insertion into
patient vasculature. The ablation catheter includes a body and
defines at least one coolant outtake region extending along at
least a portion of the ablation catheter. The guide tube is at
least partially disposed in the ablation catheter. The expansion
element is coupled to the distal portion of the body of the
ablation catheter and is configured and arranged for ablating
patient tissue. The mapping catheter includes an elongated body
that is insertable into the guide tube. The elongated body includes
a distal end that is extendable from a distal end of the guide
tube. The distal end of the elongated body includes a distal
portion that includes a plurality of electrodes, a proximal portion
disposed proximal to the distal portion, and a reduced-dimension
portion disposed between the proximal portion and the distal
portion. The reduced-dimension portion has a cross-sectional
dimension that is less than corresponding cross-sectional
dimensions of both a proximally-positioned adjacent section of the
distal portion and a distally-positioned adjacent section of the
proximal portion. The distal end is formed, at least in part, from
a memory shape material that bends into a preformed shape upon
release from a confined space. The preformed shape includes a first
loop formed, at least in part, by the distal portion. The first
loop is transverse to a longitudinal axis of the proximal portion.
The reduced-dimension portion is configured and arranged to bend
such that the reduced-dimension section advances distally through
the first loop when the first loop is held in a fixed position and
a force is applied along the longitudinal axis of the proximal
portion in a distal direction. The control module is coupled to the
ablation catheter and the mapping catheter and is configured and
arranged for controlling the mapping of electrical activity of the
mapping catheter and the ablation of patient tissue by ablation
catheter.
[0007] In yet another embodiment, a method of mapping a pulmonary
vein includes guiding a mapping catheter in proximity to an ostium
of a pulmonary vein. The mapping catheter includes an elongated
body with a distal end formed, at least in part, from a memory
shape material that bends into a preformed shape upon release from
a confined space. The distal end of the elongated body includes a
distal portion that includes a plurality of electrodes, a proximal
portion disposed proximal to the distal portion, and a
reduced-dimension portion disposed between the proximal portion and
the distal portion. The reduced-dimension portion has a
cross-sectional dimension that is less than corresponding
cross-sectional dimensions of both a proximally-positioned adjacent
section of the distal portion and a distally-positioned adjacent
section of the proximal portion. The preformed shape includes a
first loop formed, at least in part, by the distal portion. The
first loop is transverse to a longitudinal axis of the proximal
portion. The mapping catheter is inserted into the pulmonary vein
such that the first loop abuts inner walls of the pulmonary vein. A
force is provided distally along the axis of the proximal portion
sufficient to cause the reduced-dimension portion to preferentially
bend such that the reduced-dimension portion advances distally
through the first loop. Electrical activity is mapped within walls
of the pulmonary vein using a plurality of mapping electrodes
disposed along the first loop.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Non-limiting and non-exhaustive embodiments of the present
invention are described with reference to the following drawings.
In the drawings, like reference numerals refer to like parts
throughout the various figures unless otherwise specified.
[0009] For a better understanding of the present invention,
reference will be made to the following Detailed Description, which
is to be read in association with the accompanying drawings,
wherein:
[0010] FIG. 1 is a schematic partial cross-sectional and partial
block diagram view of one embodiment of a cryoablation system,
according to the invention;
[0011] FIG. 2A is a schematic longitudinal cross-sectional view of
one embodiment of an expansion element coupled to a distal portion
of an ablation catheter of the cryoablation system of FIG. 1, the
expansion element in a deflated configuration, according to the
invention;
[0012] FIG. 2B is a schematic longitudinal cross-sectional view of
one embodiment of an expansion element coupled to a distal portion
of an ablation catheter of the cryoablation system of FIG. 1, the
expansion element an inflated configuration, according to the
invention;
[0013] FIG. 3 is a schematic partial cross-sectional and partial
block diagram view of another embodiment of a cryoablation system
that includes a mapping catheter insertable into, and extendable
from, a distal end of an ablation catheter, according to the
invention;
[0014] FIG. 4A is a schematic side view of one embodiment of a
distal end of the mapping catheter of FIG. 3 in a
substantially-straight configuration, the mapping catheter having
an elongated body that includes a reduced-dimension portion
proximal to a plurality of mapping, electrodes, according to the
invention;
[0015] FIG. 4B is a schematic side view of another embodiment of a
distal end of the mapping catheter of FIG. 3 in a
substantially-straight configuration, the mapping catheter
including a reduced-dimension portion and a distal portion that
tapers in a distal direction, according to the invention;
[0016] FIG. 4C is a schematic transverse cross-sectional view of
multiple embodiments of some exemplary transverse profiles of the
mapping catheters of FIGS. 4A and 4B, according to the
invention;
[0017] FIG. 4D is a schematic transverse cross-sectional view of
multiple embodiments of some exemplary transverse profiles of
reduced-dimension portions of the mapping catheters of FIGS. 4A and
4B, according to the invention;
[0018] FIG. 4E is a schematic perspective view of one embodiment of
the reduced-dimension portion of FIGS. 4A and 4B disposed between
the distally-adjacent section and the proximally-adjacent section
of FIGS. 4A and 4B, according to the invention;
[0019] FIG. 4F is a schematic perspective view of another
embodiment of the reduced-dimension portion of FIGS. 4 A and 4B
disposed between the distally-adjacent section and the
proximally-adjacent section of FIGS. 4A and 4B, according to the
invention;
[0020] FIG. 4G is a schematic perspective view of yet another
embodiment of the reduced-dimension portion of FIGS. 4A and 4B
disposed between the distally-adjacent section and the
proximally-adjacent section of FIGS. 4A and 4B, according to the
invention;
[0021] FIG. 5 A is a schematic bottom view of one embodiment of the
distal end of the mapping catheter of FIG. 4A disposed in a
configuration having a substantially-straight proximal portion and
a distal portion bent into a loop, the loop transverse to a
longitudinal axis of the proximal portion, according to the
invention;
[0022] FIG. 5B is a schematic side view of one embodiment of the
distal end of the mapping catheter of FIG. 4 A disposed in a
configuration having a substantially-straight proximal portion and
a distal portion bent into a loop, the loop transverse to a
longitudinal axis of the proximal portion, according to the
invention;
[0023] FIG. 5C is a schematic side view of one embodiment of the
distal end of the mapping catheter of FIG. 4 A disposed in the
looped configuration of FIG. 5 A and bent along a reduced-dimension
portion of the mapping catheter such that the reduced-dimension
portion is advanced distally through a loop formed by a distal
portion of the mapping catheter, according to the invention;
[0024] FIG. 6 A is a schematic side view of one embodiment of the
mapping catheter of FIG. 4A disposed in the looped configuration of
FIG. 5B and disposed in an ostium of a pulmonary vein such that a
loop formed by the distal portion of the mapping catheter abuts
patient tissue in proximity to the ostium, according to the
invention;
[0025] FIG. 6B is a schematic side view of one embodiment of the
mapping catheter of FIG. 6A disposed in an ostium of a pulmonary
vein, the mapping catheter bent along a reduced-dimension portion
of the mapping catheter such that the reduced-dimension is advanced
distally through a loop formed by a distal portion of the mapping
catheter, according to the invention;
[0026] FIG. 7A is a schematic side view of yet another embodiment
of a distal end of the mapping catheter of FIG. 3 in a
substantially-straight configuration, the mapping catheter having
an elongated body that includes a reduced-dimension portion
proximal to a plurality of mapping electrodes, according to the
invention;
[0027] FIG. 7B is a schematic side view of another embodiment of a
distal end of the mapping catheter of FIG. 3 in a
substantially-straight configuration, the mapping catheter
including a reduced-dimension portion and a distal portion that
tapers in a distal direction, according to the invention;
[0028] FIG. 8 A is a schematic bottom view of one embodiment of the
distal end of the mapping catheter of FIG. 7 A disposed in a
configuration having a substantially-straight proximal portion, a
first loop formed by a distal portion, and a second loop formed by
a tapering reduced-dimension portion proximal to the first loop,
the loops both transverse to a longitudinal axis of the proximal
portion, according to the invention;
[0029] FIG. 8B is a schematic side view of one embodiment of the
distal end of the mapping catheter of FIG. 7B disposed in a looped
configuration having a substantially-straight proximal portion, a
first loop formed by a tapered distal portion, and a second loop
formed by a tapering reduced-dimension portion proximal to the
first loop, the loops both transverse to a longitudinal axis of the
proximal portion, according to the invention;
[0030] FIG. 8C is a schematic side view of one embodiment of the
distal end of the mapping catheter of FIG. 7 A disposed in the
looped configuration of FIG. 8 A and bent along a reduced-dimension
portion of the mapping catheter such that the reduced-dimension
portion is advanced distally through a first loop formed by a
distal portion, according to the invention;
[0031] FIG. 9A is a schematic side view of one embodiment of the
mapping catheter of FIG. 7A disposed in the looped configuration of
FIG. 8B and disposed in an ostium of a pulmonary vein such that a
first loop formed by a distal portion of the mapping catheter abuts
patient tissue in proximity to the ostium, according to the
invention;
[0032] FIG. 9B is a schematic side view of one embodiment of the
mapping catheter of FIG. 9A disposed in an ostium of a pulmonary
vein, the mapping catheter bent along a reduced-dimension portion
of the mapping catheter such that the reduced-dimension is advanced
distally through a first loop formed by the distal portion,
according to the invention;
[0033] FIG. 10 is a schematic side view of one embodiment of the
mapping catheter of FIG. 3 disposed in an ablation catheter which,
in turn, is disposed in a sheath, according to the invention.
DETAILED DESCRIPTION
[0034] The present invention is directed to the area of medical
ablation systems and methods of making and using the medical
ablation systems. The present invention is also directed to medical
ablation systems having mapping catheters configured and arranged
for facilitating the anchoring ability of the mapping catheters to
patient tissue, as well as systems and methods for making and using
the medical ablation systems and mapping catheters.
[0035] Mapping catheters include, but are not limited to, an
elongated body and a plurality of electrodes disposed at the distal
end of the body. The mapping catheters are configured and arranged
for use with a medical ablation system during an ablation
procedure. Examples of mapping catheters for use with medical
ablation systems are found in, for example, U.S. Patent
Applications Nos. 2008/0249518; and 2002/0177765, both of which are
incorporated by reference.
[0036] Mapping catheters are typically used with medical ablation
systems to map electrical activity along patient tissue. Mapping
electrical activity can be useful for locating aberrant electrical
activity, for example, in cardiac tissue. The mapping of the
electrical activity can be performed prior to, during, or after an
ablation procedure with an ablation system (e.g., a cryoablation
system, an RF ablation system, or the like). Mapping catheters are
described herein for use with cryoablation systems. It will be
understood, however, that the mapping catheters may be used with
other types of ablation systems as well including, for example, RF
ablation systems. It will also be understood that mapping catheters
may also be used with other types of medical therapeutic devices
including, for example, electrical stimulation systems.
[0037] A cryoablation system can include an ablation catheter
configured and arranged for transporting coolant to and from a
target location within a patient, an expansion element disposed at
a distal portion of the ablation catheter for ablating contacted
patient tissue, a coolant source coupled to the ablation catheter
for supplying the coolant, and a control module for controlling or
monitoring one or more of the operations of the system (e.g.,
controlling coolant flow, monitoring ablation catheter pressure or
temperature, or the like). The expansion element can be positioned
at a target location in patient vasculature (e.g., the left atrium
of the heart) and the coolant can be input to the ablation catheter
and directed to the expansion element. When the coolant contacts
the expansion element, the coolant absorbs heat and expands,
thereby causing the expansion element to expand and reduce in
temperature to a level low enough to ablate patient tissue upon
contact. The coolant flows out of the expansion element and back to
a proximal end of the ablation catheter. As the coolant flows out
of the expansion element, the expansion element deflates and the
ablation catheter may be removed from the patient vasculature.
[0038] FIG. 1 illustrates schematically one embodiment of a
cryoablation system 100. The cryoablation system 100 includes an
ablation catheter 102 with a distal portion 104 and a proximal
portion 106. An expansion element 108 is coupled to the distal
portion 104 of the ablation catheter 102. A control module 110, a
coolant source 112, and a fluid-drawing source 114 (e.g., a vacuum
source, a pump, or the like) are each coupled to the proximal
portion 106 of the ablation catheter 102. The control module 110
includes a coolant flow controller 116 to control the flow of
coolant within the ablation catheter 102 to and from the expansion
element 108. In at least some embodiments, the control module 104
also includes one or more sensors 118 for monitoring one or more
conditions (e.g., pressure, temperature, or the like) within the
ablation catheter 102.
[0039] In at least some embodiments, the coolant source 112
includes a coolant under pressure. A variety of different coolants
may be used to provide a low enough temperature to ablate tissue
upon contact. In preferred embodiments, the coolant is a low
freezing point liquid with a low vaporization temperature which may
be input to the ablation catheter 102 as a liquid that is sprayed
into the expansion element 108, where the liquid coolant absorbs
heat and is vaporized or atomized. Examples of suitable liquids
include, but are not limited to, a liquefied gas (e.g., nitrogen,
nitrous oxide, carbon dioxide, or the like), one or more
chlorofluorocarbons, one or more hydrochlorofluorocarbons, ethanol
mixtures, saline solutions, or the like. It will be understood that
a combination of one or more coolants may be used in the
cryoablation system 100.
[0040] During a typical cryoablation procedure, the distal portion
104 of the ablation catheter 102 is inserted into patient
vasculature for delivery of the expansion element 108 to one or
more ablation sites. FIG. 2A is a schematic longitudinal
cross-sectional view of one embodiment of the distal portion 104 of
the ablation catheter 102 and the expansion element 108. In FIG.
2A, the expansion element 210 is shown in a deflated configuration.
A guide tube 202, a coolant transfer lumen 204, and at least one
coolant outtake region 206 are each disposed in a flexible body 208
of the ablation catheter 102.
[0041] In some embodiments, the expansion element 108 includes a
single layer. In other embodiments, the expansion element 108
includes multiple layers. For example, in at least some
embodiments, the expansion element 108 includes an inner layer 210
and an outer layer 212 disposed over the inner layer 210. FIGS.
1-3, 5, and 6 show the expansion element 108 having two layers. It
will be understood that the expansion element 108 may, instead,
only have a single layer, or may have more than two layers.
[0042] The expansion element 108 may be formed from any elastic or
semi-elastic material, such as one or more thermoplastics (e.g.,
polyether block amide, or the like), or other plastics (e.g.,
nylon, urethane, or the like) that maintain elasticity over a wide
range of temperatures, particularly at the temperature of the
expanded coolant. In at least some embodiments, the expansion
element 108 is semi-elastic, wherein the size of the expansion
element 108 does not change in response to incremental changes in
pressure that are below 5 psi (about 34.5.times.10.sup.3 Pa).
[0043] The guide tube 202 may be formed from any flexible material
(e.g., a thermoplastic, or the like) that maintains elasticity over
a wide range of temperatures, particularly at the temperature of
the expanded coolant. In at least some embodiments, the guide tube
202 is configured and arranged to receive a mapping catheter (see
e.g., 302 in FIG. 3). In at least some embodiments, the guide tube
202 defines a lumen through which the mapping catheter 302 can be
extended. In at least some embodiments, the mapping catheter 302 is
extendable from a distal end of the guide tube 202, as discussed in
more detail below, with respect to FIG. 3.
[0044] The guide tube 202 is optionally configured and arranged to
receive a stiffening member (e.g., a stylet, or the like) to
facilitate guiding of the ablation catheter 102 to a target
location within patient vasculature by providing additional
rigidity to the ablation catheter 102. In at least some
embodiments, the guide tube 202 defines a lumen through which the
stiffening member can be extended. In at least some embodiments,
the guide tube extends along a longitudinal length of the ablation
catheter 102 from the proximal portion (106 in FIG. 1) of the
ablation catheter 102 to a position that is beyond the distal
portion 104 of the ablation catheter 102.
[0045] The coolant transfer tube 204 extends along the longitudinal
length of the ablation catheter 102 from the proximal portion (106
in FIG. 1) of the ablation catheter 102. The coolant transfer tube
204 defines a lumen. A proximal end of the lumen is coupled to the
coolant source (112 in FIG. 1). The coolant transfer tube 204
includes a distal end 214 that opens into the expansion element
108.
[0046] The coolant outtake region 206 is configured and arranged to
accommodate coolant exiting the expansion element 108. The coolant
outtake region 206 extends along the longitudinal length of the
ablation catheter 102 from the proximal portion (106 in FIG. 1) of
the ablation catheter 102 to the expansion element 108. In some
embodiments, the coolant outtake region 206 includes one or more
tubes that define one or more lumens. In other embodiments, the
coolant outtake region 206 includes one or more open regions within
the body 208 of the ablation catheter 102 and exterior to the guide
tube 202 and the coolant transfer tube 204.
[0047] In at least some embodiments, a proximal end of the
expansion element 108 couples to the distal portion 104 of the
ablation catheter 104. In at least some embodiments, the distal end
of the expansion element 108 is coupled to the guide tube 202. In
at least some embodiments, the expansion element 108 defines an
inner expansion-element space 216 within the inner layer 210. In at
least some embodiments, the inner expansion-element space 216 is in
fluid communication with the distal end of the coolant transfer
tube 204. In at least some embodiments, the inner expansion-element
space 216 is in fluid communication with the at least one coolant
outtake region 206. In at least some embodiments, the distal end
214 of the coolant transfer tube 204 extends beyond the distal
portion of the ablation catheter 102 and into the inner
expansion-element space 216. In at least some embodiments, the
inner expansion-element space 216 is in fluid communication with
the fluid-drawing source (114 in FIG. 1) via a proximal end of the
coolant outtake region 206.
[0048] In at least some embodiments, a vacuum is maintained in a
space between the inner layer 210 and the outer layer 212 (i.e., in
an intra expansion-element space 218) of the expansion element 108.
In at least some embodiments, the intra expansion-element space 218
is also in fluid communication with the fluid-drawing source 114
via a fluid pathway 220. In FIG. 2A, the fluid pathway 220 is shown
as a space within the body 208 of the ablation catheter 102. In at
least some embodiments, the fluid pathway 220 extends beyond the
ablation catheter 102 (see e.g., FIGS. 4A-4B). In at least some
embodiments, the fluid pathway 220 extends into a handle (see e.g.,
402 in FIGS. 4A-4B) configured and arranged to couple to the
proximal end 106 of the ablation catheter 102. In at least some
embodiments, the fluid pathway 220 extends to the fluid-drawing
source (114 in FIG. 1). In at least some embodiments, the fluid
pathway 220 is in fluid communication with the coolant outtake
region 206. In at least some embodiments, the fluid pathway 220 is
in fluid communication with ambient air external to the ablation
catheter 102. In at least some embodiments, the fluid pathway 220
is in fluid communication with ambient air external to a patient
when the distal end 104 of the ablation catheter 102 is inserted
into the patient. In at least some embodiments, the fluid pathway
220 is in fluid communication with ambient air external to the
cryoablation system 100.
[0049] The distal end 214 of the coolant transfer tube 204 is
configured and arranged to output coolant from the coolant transfer
tube 204 to the inner expansion-element space 216. In at least some
embodiments, the distal end 214 of the coolant transfer tube 204 is
open. In at least some embodiments, the distal end 214 of the
coolant transfer tube 204 defines one or more spray apertures. In
at least some embodiments, the coolant is output as a sprayed
liquid that vaporizes or atomizes as the liquid is output from the
distal end 214 of the coolant transfer tube 204. In at least some
embodiments, when the coolant enters the inner expansion-element
space 216, the expansion element 108 absorbs heat and expands,
thereby reducing the temperature of the expansion element 108 to a
temperature sufficiently low enough to ablate patient tissue upon
contact.
[0050] The reduction in temperature of the expansion element 108
may be due to one or more of the Joule-Thompson effect or the
latent heat of vaporization. The Joule-Thompson effect describes
the cooling effect that comes about when a compressed non-ideal gas
expands into a region of low pressure (e.g., within the expansion
element 108). The latent heat of vaporization describes heat being
released as a result of the phase change from a liquid to a gas
(e.g., the liquefied coolant vaporizing upon entering the expansion
element 108).
[0051] FIG. 2B is a schematic longitudinal cross-sectional view of
one embodiment of the expansion element 108 in an inflated
configuration. Directional arrows, such as arrow 230, show the flow
of coolant from the distal end 214 of the coolant transfer tube 204
to the inner expansion-element space 216. The expanded gas
dissipates down the ablation catheter 102 along the coolant outtake
region 206. In at least some embodiments, the fluid-drawing source
(114 in FIG. 1) is used to draw the expanded, heated, and gaseous
coolant along the coolant outtake region 206 from the expansion
element 108 out the proximal end of the coolant outtake region 206.
In at least some embodiments, the fluid-drawing source 114 is also
used to maintain a vacuum in the intra expansion-element space 218.
In at least some embodiments, the fluid-drawing source 114
maintains a vacuum in the intra expansion-element space 218 via the
fluid pathway 220.
[0052] The ablation catheter 102 may be inserted in patient
vasculature and guided to an ablation site, such as the ostia of
one or more of the pulmonary veins in the left atrium of the heart
of the patient. In at least some embodiments, the expansion element
108 is maintained in a vacuum during insertion. Sometime after the
expansion element is in proximity to the ablation site, coolant
from the coolant source (106 in FIG. 1) is released into the
ablation catheter 102. In at least some embodiments, the coolant
source 106 includes a pressurized container or pump. In at least
some embodiments, the lower pressure in the expansion element 108
draws the coolant along the coolant transfer tube 104 and into the
expansion element 108. In at least some embodiments, the
fluid-drawing source (114 in FIG. 1) may be used to control the
rate of flow of the coolant within the ablation catheter 102. The
rate of flow of the coolant within the ablation catheter 102 may be
adjusted to a rate appropriate to the specific type of
operation.
[0053] Typically, electrical activity within patient tissue
surrounding the ostium of the pulmonary vein being ablated is
monitored and mapped prior to ablation. Potential foci for the
arrhythmia are identified based on the electrical map. The foci may
be ablated by forming a lesion (e.g., using the cryoablation system
(or RF ablation system)) along the inner wall of the pulmonary
vein, or along tissue of the left atrium in proximity to the ostia
of the pulmonary vein, to isolate the heart from the aberrant
electrical activity along the pulmonary vein. The efficacy of the
electrical isolation may be checked by remapping the pulmonary vein
during or after ablation. In at least some embodiments, the mapping
catheter may be left in place during ablation in order to allow the
pulmonary vein to be remapped at the same location of the
ablation.
[0054] Effective treatment of atrial fibrillation may depend on the
ability of the ablation system to obtain a successful electrical
map of the heart at the atrium or ostium of one or more of the
pulmonary veins before and after an ablation procedure. In at least
some embodiments, a mapping catheter is used to perform electrical
mapping. FIG. 3 is a schematic partial cross-sectional and partial
block diagram view of another embodiment of a cryoablation system
300 that includes a mapping catheter 302 insertable into, and
extendable from, an ablation catheter 304. In at least some
embodiments, one or more mapping electrodes 306 are disposed along
a distal end of the mapping catheter 302. In at least some
embodiments, the mapping catheter 302 extends through a lumen 308
defined along at least a portion of the ablation catheter 304.
[0055] In at least some embodiments, the electrodes 306 are
electrically coupled to an electronic subassembly 310 disposed in a
control module 312 and configured and arranged to control the
operation of the electrodes 306. In at least some embodiments, the
electrodes 306 are electrically coupled to the control module 312
via one or more conductors (not shown) extending along at least a
portion of the mapping catheter 302.
[0056] In at least some embodiments, once the ablation catheter 304
is positioned in proximity to a potential ablation site, the distal
end of the mapping catheter 302 is extended from the ablation
catheter 304. In at least some embodiments, once the distal end of
the mapping catheter 320 is extended from the ablation catheter
304, the distal end of the mapping catheter 302 bends into a
preformed shape that includes a loop along an axis that is
approximately transverse to the axis of the ablation catheter 304
(see e.g., FIG. 4B). Examples of mapping catheters and associated
ablation catheters can be found in U.S. Patent Applications Nos.
2008/0249518; and 2002/0177765, both of which are incorporated by
reference.
[0057] It is desirable for an ablation system to maintain a stable
position and orientation during an ablation procedure to ensure
accurate electrical mapping and accurate ablation. During at least
a portion of the ablation procedure, the mapping catheter may be
the only portion of an ablation system physically contacting the
pulmonary vein. At least some conventional ablation systems are
configured and arranged such that a transverse loop of the mapping
catheter is the only portion of the ablation system anchoring the
ablation system to the pulmonary vein. When a loop is the only
portion of an ablation system anchoring the ablation system to a
pulmonary vein, the ablation system may pivot, tilt, rock, or even
shift position, thereby maintaining an unstable position or
orientation with respect to the pulmonary vein.
[0058] In at least some embodiments, the mapping catheter 302
includes an elongated body having a proximal portion coupled to a
loop formed by a distal portion of the elongated body that is
transverse to an axis of the proximal portion. In at least some
embodiments, once the loop is positioned against patient tissue, a
reduced-dimension portion of the mapping catheter 302 can be bent
such that the reduced-dimension portion can be advanced distally
through the loop. In at least some embodiments, by advancing the
reduced-dimension portion through the loop, the ablation system 300
may be more stably anchored to patient tissue during at least a
portion of an ablation procedure.
[0059] FIG. 4 A is a schematic side view of one embodiment of a
distal end of the mapping catheter 302 in a substantially-straight
configuration. The mapping catheter 302 may be in a
substantially-straight configuration when, for example, the mapping
catheter 302 is disposed in a confined space (e.g., when the
mapping catheter 302 is disposed in the lumen 308 of the ablation
catheter 302). It will be understood that a "substantially-straight
configuration" may be curved, particularly when the mapping
catheter 302 is disposed in a confined space that is curved, such
as a curved lumen.
[0060] The mapping catheter 302 includes a proximal portion 404 and
a distal portion 402. At least some of the electrodes 306 are
disposed on the distal portion 402 of the mapping catheter 302. In
some embodiments, the distal portion 402 is isodiametric. In other
embodiments, as shown in FIG. 4B, at least a part of the distal
portion 402 tapers towards in a distal direction. The mapping
catheter 302 also includes a reduced-dimension portion 406
positioned between the proximal portion 404 and the distal portion
402. In at least some embodiments, the reduced-dimension portion
406 tapers. In at least some embodiments, at least one of the
electrodes 306 is disposed on the reduced-dimension portion 406.
The proximal portion 404 includes a section 408 that is positioned
proximally-adjacent to the reduced-dimension portion 406. The
distal portion 402 includes a section 410 that is positioned
distally-adjacent to the reduced-dimension portion 406.
[0061] In at least some embodiments, the distal end of the mapping
catheter 302 is formed, at least in part, using a shape memory
material (e.g., nitinol, or the like). For example, in at least
some embodiments, the mapping catheter 302 has a nitinol core and a
shell formed over the nitinol core that is formed from a
non-conductive material (e.g., one or more polymers, or the like or
combinations thereof). In at least some embodiments, the mapping
catheter 302 may be preformed in a desired shape that may be
reversibly straightened when the mapping catheter 302 is disposed
in a confined space (e.g., the lumen 308 of the ablation catheter
302).
[0062] In at least some embodiments, at least a portion of the
mapping catheter 302 has a transverse profile that is round. It
will be understood that one or more portions of the mapping
catheter 302 may have a transverse profile (see e.g., exemplary
transverse profiles 410-417 of FIG. 4C) that is at least one other
shape (either geometric or irregular) besides round. For example,
at least one of the proximal portion 404 or the distal portion 402
of the mapping catheter 302 may have a transverse profile that is
ovoid, triangular, rectangular, pentagonal, hexagonal, heptagonal,
octagonal, nonagonal, decagonal, cross-shaped, star-shaped, or the
like.
[0063] The electrodes 306 may be any suitable shape for contacting
patient tissue when the mapping catheter 302 is configured into a
preformed shape (e.g., when a distal end of the mapping catheter
302 is formed into a looped configuration, as shown in FIGS. 5A-5C
and 8A-8C). For example, the electrodes 306 may be annular,
C-shaped, geometrically shaped (e.g., ovoid, triangular,
rectangular, pentagonal, hexagonal, heptagonal, octagonal,
nonagonal, decagonal, or the like), irregularly shaped, or the like
or combinations thereof.
[0064] Any number of electrodes 306 may be disposed on the mapping
catheter 302 suitable for electrically mapping a region of patient
tissue. For example, there may be one, two, three, four, five, six,
seven, eight, nine, ten, eleven, twelve, sixteen, twenty,
twenty-four, or more electrodes 306. It will be understood that
there may be other numbers of electrodes 306 disposed on the
mapping catheter 302.
[0065] The distal portion 402 of the mapping catheter 302 can be
formed having any transverse diameter suitable for forming into one
or more loops sized for removable placement around an inner
perimeter of a blood vessel (e.g., an ostium of a pulmonary vein,
or the like) for electrical mapping. The reduced-dimension portion
406 is a region that is more flexible than the remaining portions
of the mapping catheter 302 that are extendable from the ablation
catheter 102 along at least one dimension. In at least some
embodiments, when a force is applied to the mapping catheter 302,
the increased flexibility of the reduced-dimension portion 406
causes the reduced-dimension portion 406 to preferentially bend
along the at least one dimension. In at least some embodiments, the
reduced-dimension portion 406 is disposed proximal to the
electrodes 306. In at least some embodiments, at least one
electrode is disposed on the reduced-dimension portion 406. In at
least some embodiments, at least one electrode is disposed proximal
to the reduced-dimension portion 406.
[0066] As discussed above, in at least some embodiments the
transverse profile of the distal portion 402 of the mapping
catheter 302 is isodiametric. In at least some embodiments, the
transverse profile of the proximal portion 404 of the mapping
catheter 302 is isodiametric. In at least some embodiments, the
transverse profile of the portions of the mapping catheter 302 that
are extendable from the ablation catheter 102 are isodiametric
except for the reduced-dimension portion 406.
[0067] In at least some embodiments, the reduced-dimension portion
406 is made more flexible than the remaining portions of the
mapping catheter 302 that are extendable from the ablation catheter
102 by selecting at least one of the size or the shape of the
transverse profile (e.g., the transverse cross-sectional shape) of
the reduced-dimension portion 406 (see e.g., transverse profiles
420 and 421 of FIG. 4D) so that it differs from at least one of the
size or the shape of the transverse profile of the remaining
portions of the mapping catheter 302 that are extendable from the
ablation catheter 102 (see e.g., exemplary transverse profiles
410-417 of FIG. 4C).
[0068] For example, in at least some embodiments, the transverse
profile of the proximal portion 404 and the distal portion 402 of
the distal end of the mapping catheter 302 are round, while the
transverse profile of the reduced-dimension portion 406 is
rectangular 421. Thus, in at least some embodiments, when the
reduced-dimension portion 406 has a rectangular 421 transverse
profile, the reduced-dimension portion 406 has two perpendicular
dimensions that form a height 424 and a width 426, respectively.
Thus, the transverse profile of the reduced-dimension portion 406
may have a variety of different aspect ratios (i.e., the ratio of
the larger diameter (424 in FIG. 4C) to the smaller diameter (426
in FIG. 4C)).
[0069] In at least some embodiments, the transverse profile of the
reduced-dimension portion 406 has an aspect ratio of no greater
than approximately 1:1. In at least some embodiments, the
transverse profile of the reduced-dimension portion 406 has an
aspect ratio of no greater than approximately 2:1. In at least some
embodiments, the transverse profile of the reduced-dimension
portion 406 has an aspect ratio of no greater than approximately
3:1. In at least some embodiments, the transverse profile of the
reduced-dimension portion 406 has an aspect ratio of no greater
than approximately 4:1. In at least some embodiments, the
transverse profile of the reduced-dimension portion 406 has an
aspect ratio of no greater than approximately 5:1. In at least some
embodiments, the transverse profile of the reduced-dimension
portion 406 has an aspect ratio of no greater than approximately
6:1. In at least some embodiments, the transverse profile of the
reduced-dimension portion 406 has an aspect ratio of no greater
than approximately 7:1. In at least some embodiments, the
transverse profile of the reduced-dimension portion 406 has an
aspect ratio of no greater than approximately 8:1. In at least some
embodiments, the transverse profile of the reduced-dimension
portion 406 has an aspect ratio of no greater than approximately
9:1. In at least some embodiments, the transverse profile of the
reduced-dimension portion 406 has an aspect ratio of no greater
than approximately 10:1.
[0070] In at least some embodiments, the smallest transverse
dimension of the reduced-dimension portion 406 is less than the
largest transverse dimension of the proximally-adjacent section 408
and the largest transverse dimension 440 of the distally-adjacent
section 410. FIG. 4E is a schematic perspective view of one
embodiment of a reduced-dimension portion 406 disposed between the
distally-adjacent section 410 and the proximally-adjacent section
408. In FIG. 4E, the smallest transverse dimension 426 of the
reduced-dimension portion 406 is less than the largest transverse
dimension 440 of the proximally-adjacent section 408. In FIG. 4E,
the largest transverse dimension 424 of the reduced-dimension
portion 406 is greater than the smallest transverse dimension 426,
but is less than the largest transverse dimension 440 of the
proximally-adjacent section 408. In at least some embodiments, the
proximally-adjacent section 408 and the distally-adjacent section
410 are equal in diameter.
[0071] In at least some embodiments, the largest transverse
dimension of the reduced-dimension portion 406 is equal to, or
greater than, the largest transverse dimension of the
proximally-adjacent section 408 and the largest transverse
dimension 440 of the distally-adjacent section 410. FIG. 4F shows
the largest transverse dimension 424 of the reduced-dimension
portion 406 being greater than the smallest transverse dimension
426 and equal to the largest transverse dimension 440 of the
proximally-adjacent section 408. FIG. 4G shows the largest
transverse dimension 424 of the reduced-dimension portion 406 being
greater than the smallest transverse dimension 426 and greater than
the largest transverse dimension 440 of the proximally-adjacent
section 408.
[0072] In at least some embodiments, the smallest transverse
dimension 426 of the reduced-dimension portion 406 is no more than
one quarter the length of at least one of the largest transverse
dimension of the proximally-adjacent section 408 or the largest
transverse dimension 440 of the distally-adjacent section 410. In
at least some embodiments, the smallest transverse dimension 426 of
the reduced-dimension portion 406 is no more than one third the
length of at least one of the largest transverse dimension of the
proximally-adjacent section 408 or the largest transverse dimension
440 of the distally-adjacent section 410. In at least some
embodiments, the smallest transverse dimension 426 of the
reduced-dimension portion 406 is no more than one half the length
of at least one of the largest transverse dimension of the
proximally-adjacent section 408 or the largest transverse dimension
440 of the distally-adjacent section 410. In at least some
embodiments, the smallest transverse dimension 426 of the
reduced-dimension portion 406 is no more than one two-thirds the
length of at least one of the largest transverse dimension of the
proximally-adjacent section 408 or the largest transverse dimension
440 of the distally-adjacent section 410. In at least some
embodiments, the smallest transverse dimension 426 of the
reduced-dimension portion 406 is no more than three-quarters the
length of at least one of the largest transverse dimension of the
largest transverse dimension of the proximally-adjacent section 408
or the largest transverse dimension 440 of the distally-adjacent
section 410.
[0073] In at least some embodiments, when the distal end of the
mapping catheter 302 is extended from the ablation catheter 102,
the distal end of the mapping catheter 302 is configured and
arranged to bend into a looped configuration. In at least some
embodiments, the distal end of the mapping catheter 302 is formed
from a shape memory material configured and arranged to bend into a
preformed shape that includes at least one loop without external
aid when the distal end of the mapping catheter 302 is extended
from the ablation catheter 102. In at least some embodiments, the
one or more loops extend approximately transverse to the axis of
the proximal portion 404. In at least some embodiments, the one or
more loops extend approximately transverse to the axis of the
ablation catheter 102.
[0074] FIGS. 5 A and 5B are a schematic side view and bottom view,
respectively, of one embodiment of the distal end of the mapping
catheter 302 having an elongated body 500 that includes the distal
portion 402, the proximal portion 404, and the reduced-dimension
portion 406. The distal portion 402 is configured into a shape that
includes a loop 502. At least one of the electrodes 306 is disposed
on the loop 502. In at least some embodiments, the loop 502 is
formed by bending the distal portion 402 at least three-quarters of
a full circle. In at least some embodiments, the loop 502 is formed
by bending the distal portion 402 at least one full circle. In at
least some embodiments, the loop 502 is formed by bending the
distal portion 402 at least one-and-a-quarter full circles. In at
least some embodiments, the loop 502 tapers in a distal direction
(see e.g., the distal portion 402 of FIG. 4B). In at least some
embodiments, the smallest transverse dimension 426 of the
reduced-dimension portion 406 is greater than a smallest transverse
dimension of the tapered loop 502.
[0075] The loop 502 can be formed to any suitable diameter for
mapping electrical activity of a region of patient tissue. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 1 cm along the body 500 of the mapping catheter 302. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 2 cm along the body 500 of the mapping catheter 302. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 3 cm along the body 500 of the mapping catheter 302. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 4 cm along the body 500 of the mapping catheter 302. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 5 cm along the body 500 of the mapping catheter 302. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 6 cm along the body 500 of the mapping catheter 302. In at
least some embodiments, the reduced-dimension portion 406 extends
at least 7 cm along the body 500 of the mapping catheter 302.
[0076] In at least some embodiments, the reduced-dimension portion
406 is configured and arranged to bend when the loop 502 is held in
a fixed position (such as being extended around inner walls of a
patient blood vessel) and a force is applied distally approximately
along a longitudinal axis of the proximal portion 404 of the
mapping catheter 302, as shown by directional arrow 520. In at
least some embodiments, when such a force is applied, the
reduced-dimension portion 406 is configured and arranged to
preferentially bend to advance the proximal portion 404 distally.
In at least some embodiments, when such a force is applied, the
reduced-dimension portion 406 is configured and arranged to
preferentially bend such that the reduced-dimension portion 406
advances distally through the loop 502. In at least some
embodiments, when such a force is applied, the reduced-dimension
portion 406 is configured and arranged to preferentially bend such
that a section 530 of the mapping catheter 302 proximally adjacent
to the reduced-dimension portion 406 advances distally through the
loop 502. In at least some embodiments, the amount of force applied
to bend the reduced-dimension portion 406 can be less than the
amount of force to bend the remaining portions of the mapping
catheter 302.
[0077] FIG. 5C is a schematic side view of one embodiment of the
distal end of the mapping catheter 302. The reduced-dimension
portion 406 is bent such that the reduced-dimension portion 406 and
the section 530 of the mapping catheter 302 proximally adjacent to
the reduced-dimension portion 406 is extended through the loop
502.
[0078] The mapping catheter 302 can be positioned to abut patient
tissue to be electrically mapped. The distal portion 402 of the
mapping catheter 302 can be extended from the ablation catheter 102
and bent to form the loop 502. The mapping catheter 302 can be
positioned against patient tissue such that the electrodes 306
contact patient tissue at the site to be mapped. FIG. 6A is a
schematic side view of one embodiment of the distal end of the
mapping catheter 302 formed into a looped configuration and
disposed in an ostium 602 of a pulmonary vein such that the loop
502 of the mapping catheter 302 abuts patient tissue along inner
walls 604 of the ostium 602. In FIGS. 6A-6B the walls 604 are shown
as being transparent for clarity of illustration.
[0079] A force may be applied to the mapping catheter 302 in the
direction indicated by directional arrow 520. The force causes the
reduced-dimension portion 406 of the mapping catheter 302 to
preferentially bend such that the reduced-dimension portion 406 of
the mapping catheter 302 advances distally through the loop 502. In
at least some embodiments, the force causes the reduced-dimension
portion 406 of the mapping catheter 302 to preferentially bend such
that the section 530 of the mapping catheter 302 proximally
adjacent to the reduced-dimension portion 406 advances distally
through the loop 502.
[0080] FIG. 6B is a schematic side view of one embodiment of the
distal end of the mapping catheter 302 disposed in the ostium 602
of a pulmonary vein such that the loop 502 of the mapping catheter
302 abuts patient tissue 604 in proximity to the ostium 602. The
reduced-dimension portion 406 of the mapping catheter 302 is bent
such that the reduced-dimension portion 406 of the mapping catheter
302 extends through the loop 502. In at least some embodiments, the
reduced-dimension portion 406 is bent such that the section 530 of
the mapping catheter 302 proximally adjacent to the
reduced-dimension portion 406 extends through the loop 502.
[0081] In at least some embodiments, when the reduced-dimension
portion 406 extends through the loop 502, the mapping catheter 302
anchors more stably to the inner walls 604 of the ostium 602. In at
least some embodiments, when the reduced-dimension portion 406
extends distally through the loop 502, the ability of the mapping
catheter 302 to tilt, pivot, rock, or shift position within the
ostium 602 is reduced from when the reduced-dimension portion 406
is positioned proximal to the loop 502. In at least some
embodiments, the reduced-dimension portion 406 is extended distally
through the loop 502 such that the reduced-dimension portion 406
abuts patient tissue 604.
[0082] FIG. 7 A is a schematic side view of another embodiment of
the distal end of the mapping catheter 302 disposed in a
substantially-straight configuration. The mapping catheter 302
includes a distal portion 702 and a proximal portion 704. The
electrodes 306 are disposed on the distal portion 702 of the
mapping catheter 302. In some embodiments, the distal portion 702
is isodiametric. In other embodiments, as shown in FIG. 7B, the
distal portion 702 tapers in a distal direction. The mapping
catheter 302 also includes a reduced-dimension portion 706
positioned between the distal portion 702 and the proximal portion
704. In at least some embodiments, the reduced-dimension portion
706 tapers in a proximal direction. In at least some embodiments,
at least one of the electrodes 306 is disposed on the
reduced-dimension portion 706. The proximal portion 704 includes a
section 708 that is positioned proximally-adjacent to the
reduced-dimension portion 706. The distal portion 702 includes a
section 710 that is positioned distally-adjacent to the
reduced-dimension portion 706.
[0083] In at least some embodiments, when the distal end of the
mapping catheter 302 is extended from the ablation catheter 102,
the mapping catheter 302 bends into a looped configuration that
includes two loops. In at least some embodiments, the distal
portion 702 bends to form a first loop. In at least some
embodiments, the reduced-dimension 706 bends to form a second loop.
In at least some embodiments, both loops are parallel to one
another. In at least some embodiments, at least one of the loops is
transverse to a longitudinal axis of the proximal portion 704. In
at least some embodiments, both loops are transverse to a
longitudinal axis of the proximal portion 704.
[0084] FIGS. 8A and 8B are a schematic side view and bottom view,
respectively, of alternate embodiments of a distal end of the
mapping catheter 302 having an elongated body 800 that includes the
distal portion 702, the proximal portion 704, and the
reduced-dimension portion 706 disposed between the distal portion
702 and the proximal portion 704. In FIG. 8A, the distal portion
702 is shown as being isodiametric, as shown in FIG. 7A. In FIG.
8B, the distal portion 702 is shown tapering in a distal direction,
as shown in FIG. 7B. The distal portion 702 (as shown in both FIGS.
8A and 8B) is configured into a shape that includes a first loop
802. At least one of the electrodes 306 is disposed on the first
loop 802. In at least some embodiments, at least one electrode is
disposed proximal to the first loop 802. In at least some
embodiments, at least one electrode is disposed on the
reduced-dimension portion 706. In at least some embodiments, at
least one electrode is disposed proximal to the reduced-dimension
portion 706.
[0085] In at least some embodiments, the reduced-dimension portion
706 bends to form a second loop 804. In at least some embodiments,
the second loop 804 is formed by bending the reduced-dimension
portion 706 at least three-quarters of a full circle. In at least
some embodiments, the second loop 804 is formed by bending the
reduced-dimension portion 706 at least one full circle. In at least
some embodiments, the second loop 804 is formed by bending the
reduced-dimension portion 706 at least one-and-a-quarter full
circles. In at least some embodiments, the second loop 804 tapers
proximally (see e.g., FIGS. 7A-7B).
[0086] The second loop 804 can be formed to any suitable diameter
for facilitating stabilization of at least one of the orientation
or the position of the mapping catheter 302 when the mapping
catheter 302 is inserted into patient vasculature. In at least some
embodiments, the second loop 804 has a diameter that is smaller in
length than the first loop 802.
[0087] In at least some embodiments, the reduced-dimension portion
706 is configured and arranged to preferentially bend when the
first loop 802 is held in a fixed position (such as being extended
around inner walls of a patient blood vessel) and a force is
applied distally approximately along a longitudinal axis of the
proximal portion 704 of the mapping catheter 302, as shown by
directional arrow 820. In at least some embodiments, when such a
force is applied, the reduced-dimension portion 706 is configured
and arranged to preferentially bend to advance the proximal portion
404 distally. In at least some embodiments, when such a force is
applied, the reduced-dimension portion 706 is configured and
arranged to preferentially bend such that the reduced-dimension
portion 706 (i.e., the second loop 804) advances distally through
the first loop 802. In at least some embodiments, when such a force
is applied, the reduced-dimension portion 706 (i.e., the second
loop 804) is configured and arranged to preferentially bend such
that the section 708 of the mapping catheter 302 proximally
adjacent to the reduced-dimension portion 706 advances distally
through the first loop 802. In at least some embodiments, the
amount of force applied to bend the reduced-dimension portion 806
can be less than the amount of force to bend the remaining portions
of the mapping catheter 302.
[0088] FIG. 8C is a schematic side view of one embodiment of the
distal end of the mapping catheter 302. The reduced-dimension
portion 706 is bent such that the reduced-dimension portion 706 and
the section 708 of the mapping catheter 302 proximally adjacent to
the reduced-dimension portion 706 extend through the first loop
802. As shown in FIG. 8C, in at least some embodiments the
reduced-dimension portion 706 tapers in a proximal direction. In at
least some embodiments, the tapering of the reduced-dimension
portion 706 allows for further control of the preferential bending
of the reduced-dimension portion 706 by varying the length of at
least one transverse dimension along the reduced-dimension portion
706. For example, in at least some embodiments, when the
reduced-dimension portion 706 tapers in a proximal direction, a
proximal end of the reduced-dimension portion 706 bends
preferentially to a distal end of the reduced-dimension portion
706.
[0089] The mapping catheter 302 can be positioned to abut patient
tissue to be electrically mapped. The distal end of the mapping
catheter 302 can be extended from the ablation catheter 102. Once
extended from the ablation catheter 102, the distal portion 702 can
bend to form the first loop 802 and the reduced-dimension portion
706 can bend to form a second loop 804 disposed proximal to the
first loop 802. The mapping catheter 302 can be positioned against
patient tissue such that the electrodes 306 (disposed at least in
part on the first loop 802) contact patient tissue at the site to
be mapped.
[0090] FIG. 9A is a schematic side view of one embodiment of the
mapping catheter 302 formed into a looped configuration and
disposed in an ostium 902 of a pulmonary vein such that the first
loop 802 of the mapping catheter 302 abuts patient tissue along
inner walls 904 of the ostium 902. In FIGS. 9A-9B the walls 904 are
shown as being transparent for clarity of illustration. A force may
be applied to the mapping catheter 302 in the direction indicated
by directional arrow 820. The force causes the reduced-dimension
portion 706 (i.e., the second loop 804) of the mapping catheter 302
to preferentially bend such that the reduced-dimension portion 706
of the mapping catheter 302 advances distally through the first
loop 802. In at least some embodiments, the force causes the
reduced-dimension portion 706 of the mapping catheter 302 to
preferentially bend such that the section 708 of the mapping
catheter 302 proximally adjacent to the reduced-dimension portion
706 advances distally through the first loop 802.
[0091] FIG. 9B is a schematic side view of one embodiment of the
mapping catheter 302 disposed in the ostium 902 of a pulmonary vein
such that the first loop 802 of the mapping catheter 302 abuts
patient tissue 904 in proximity to the ostium 902. The
reduced-dimension portion 706 (i.e., the second loop 804) of the
mapping catheter 302 is bent such that the reduced-dimension
portion 706 of the mapping catheter 302 extends through the first
loop 802. In at least some embodiments, the reduced-dimension
portion 706 is bent such that the section 708 of the mapping
catheter 302 proximally adjacent to the reduced-dimension portion
706 extends through the first loop 802.
[0092] In at least some embodiments, when the reduced-dimension
portion 706 extends through the first loop 802, the second loop 804
abuts the inner walls 904 of the ostium 902, causing the mapping
catheter 302 to anchor more stably within the ostium 902. In at
least some embodiments, when the reduced-dimension portion 706
(i.e., the second loop 804) extends distally through the loop 802,
the ability of the mapping catheter 302 to tilt, pivot, rock, or
shift position within the ostium 902 is reduced from when the
reduced-dimension portion 706 is positioned proximal to the loop
802.
[0093] In at least some embodiments, a sheath may be used to
facilitate guidance of the ablation catheter (and mapping catheter)
through patient vasculature during insertion of the ablation
catheter (and mapping catheter) into a patient. FIG. 10 is a
schematic longitudinal cross-sectional view of one embodiment of
the distal portion 104 of the ablation catheter 102 disposed in a
sheath 1002. In at least some embodiments, the sheath 1002 is
steerable. Once the ablation catheter 102 is positioned at a target
location, such as the ostia of the pulmonary veins in the left
atrium of the heart of the patient, the sheath 1002 can be removed
and the mapping catheter 302 can be extended from the ablation
catheter 102.
[0094] The above specification, examples and data provide a
description of the manufacture and use of the composition of the
invention. Since many embodiments of the invention can be made
without departing from the spirit and scope of the invention, the
invention also resides in the claims hereinafter appended.
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