U.S. patent application number 14/139062 was filed with the patent office on 2015-06-25 for small loop ablation catheter.
The applicant listed for this patent is Boaz Avitall. Invention is credited to Boaz Avitall.
Application Number | 20150173828 14/139062 |
Document ID | / |
Family ID | 53398828 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150173828 |
Kind Code |
A1 |
Avitall; Boaz |
June 25, 2015 |
SMALL LOOP ABLATION CATHETER
Abstract
A catheter system for creating lesions for the treatment of
cardiac arrhythmias is disclosed that includes a catheter having a
distal ablation segment that has an electrode array comprising a
plurality of spaced ablation and recording electrode devices
arranged in a tight loop configuration that is used to create a
series of overlapping loop-shaped ablation footprints to produce a
continuous lesion resembling a chain-link configuration.
Inventors: |
Avitall; Boaz; (Milwaukee,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Avitall; Boaz |
Milwaukee |
WI |
US |
|
|
Family ID: |
53398828 |
Appl. No.: |
14/139062 |
Filed: |
December 23, 2013 |
Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/1467 20130101;
A61B 2018/1407 20130101; A61B 18/1492 20130101; A61B 2018/0016
20130101; A61B 2018/00357 20130101; A61B 2018/00577 20130101; A61B
2018/00839 20130101; A61B 2018/00815 20130101; A61B 2018/00023
20130101 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1. A medical device comprising: an elongate catheter shaft member
having a proximal end and distal end; an ablation segment attached
at or near the distal end of the catheter shaft member, said
ablation segment comprising an electrode array of spaced ablation
and recording electrodes in an arrangement shape selected from a
generally linear extension of the catheter shaft and a fixed tight
loop, wherein the generally linear shaped arrangement includes a
distally attached pull wire device for causing said array to form a
tight loop when it is retracted.
2. A medical device as in claim 1 wherein in use the ablation
segment is configured to create a loop-shaped, chain link ablation
footprint and wherein a plurality thereof in an overlapping pattern
creates a continuous lesion in tissue of a patient.
3. A medical device as in claim 1 wherein the ablation segment
comprises an array of spaced ablation electrodes arranged in a
fixed tight loop.
4. A medical device as in claim 3 wherein said fixed tight loop
includes a collapsible nose segment.
5. A medical device as in claim 1 wherein electrode array comprises
at least one temperature sensor.
6. A medical device as in claim 1 further comprising an irrigation
system that supplies cooling irrigation fluid to said ablation
electrodes.
7. A medical device as in claim 6 wherein each said ablation
electrode includes an irrigation port.
8. A medical device as in claim 1 wherein said catheter shaft
comprises at least one inner shaft and core.
9. A medical device as in claim 3 wherein said fixed tight loop has
two ends separately attached to said catheter shaft.
10. A medical device as in claim 3 further comprising a membrane
covering an open central portion of said loop.
11. A medical device as in claim 10 wherein said membrane is
provided with sensing and pacing electrodes.
12. A medical device as in claim 10 wherein said membrane is
irrigated.
13. A medical device as in claim 1 wherein the ablation electrodes
apply RF energy to accomplish ablation of tissue to form a lesion
in the tissue enclosed by the loop.
14. A medical device as in claim 13 wherein said RF energy is
applied using bipolar energy delivery to limit lesion
formation.
15. A medical device as in claim 11 wherein the ablation electrodes
apply RF energy using bipolar energy delivery to limit lesion
formation.
16. A medical device as in claim 1 wherein the ablation segment has
one end attached as a generally linear extension of said catheter
shaft and said pull wire enables adjustment of loop size.
17. A medical device as in claim 6 wherein said irrigation fluid is
distributed substantially equally to all connected ablation
electrodes.
18. A medical device as in claim 6 wherein said ablation segment
comprises a tight fixed loop and said irrigation system supplies
halves of said loop separately.
19. A medical device as in claim 13 further comprising a reference
electrode for controlling the amount of RF energy applied to each
ablation electrode.
20. A medical device comprising: an elongate, flexible steerable
outer sheath member having a proximal and a distal end and a lumen
extending therebetween; a catheter having an elongate outer shaft
member and an inner torqueable control shaft disposed in said outer
sheath in slideable relation thereto, wherein the distal portion of
said catheter shaft includes an ablation segment having an
electrode array comprising a plurality of sequentially arranged,
spaced ablation and recording electrode devices arranged to assume
a tight loop configuration.
21. A medical device as in claim 20 wherein in use the ablation
segment is configured to create a loop-shaped, chain link ablation
footprint and wherein a plurality thereof in an overlapping pattern
creates a continuous lesion in tissue of a patient.
22. A medical device as in claim 20 wherein said tight loop is
achieved and adjusted using a pull wire attached to said ablation
segment.
23. A medical device as in claim 20 wherein said ablation segment
is in the form of a fixed tight loop.
24. A medical device as in claim 23 wherein said fixed tight loop
includes a collapsible nose segment.
25. A medical device as in claim 20 wherein electrode array
comprises at least one temperature sensor.
26. A medical device as in claim 20 further comprising an
irrigation system that supplies cooling irrigation fluid to said
ablation electrodes.
27. A medical device as in claim 25 wherein each said ablation
electrode includes an irrigation port.
28. A medical device as in claim 23 wherein said fixed tight loop
has two ends separately attached to said catheter shaft.
29. A medical device as in claim 23 further comprising a membrane
covering an open central portion of said loop.
30. A medical device as in claim 29 wherein said membrane is
provided with sensing and pacing electrodes.
31. A medical device as in claim 20 wherein the ablation electrodes
apply RF energy using bipolar energy delivery to limit lesion
formation.
32. A medical device as in claim 30 wherein the ablation electrodes
apply RF energy to accomplish ablation of tissue to form a lesion
in the tissue enclosed by the loop.
33. A medical device as in claim 32 wherein said RF energy is
applied using bipolar energy delivery to limit lesion
formation.
34. A medical device as in claim 29 wherein said membrane is
irrigated.
35. A medical device as in claim 20 further comprising a reference
electrode for controlling the amount of RF energy applied to each
ablation electrode.
36. A medical device as in claim 20 further comprising a pull wire
attached to said ablation segment and extending proximally for
forming said ablation segment into a loop arrangement of adjustable
size.
37. A method of creating continuous lesions for the treatment of
cardiac arrhythmias comprising: providing a catheter having a
distal ablation segment having an electrode array comprising a
plurality of spaced ablation and recording electrode devices
arranged in a tight loop configuration; using said ablation segment
in a procedure to create a series of overlapping loop-shaped
ablation footprints to create a continuous lesion resembling a
chain-link configuration.
38. A method of claim 37 wherein said ablation electrodes are
operated using RF energy in a bipolar mode to limit lesion
formation to tissue enclosed by the loop.
39. A method as in claim 36 including using irrigation to cool said
ablation electrodes during use.
40. A method as in claim 36 further comprising monitoring lesion
formation and evaluating the maturation of tissue ablation of said
ablation footprints.
41. A method as in claim 36 wherein said procedure includes
isolation of pulmonary veins in the left atrium of a heart.
42. A method as in claim 41 further comprising providing a left
atrial isthmus lesion and connecting lesion between the pulmonary
vein lesions and the left atrial isthmus lesion.
43. A method as in claim 40 wherein said monitoring and evaluating
involves recording and temperature sensing technology.
44. A method as in claim 36 including providing a membrane barrier
between tissue being ablated and adjacent blood flow.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] I. Field of the Invention
[0004] The present invention relates generally to the field of
catheter-based tissue ablation devices and techniques and, more
particularly, to catheter devices and methods for performing tissue
ablation to relieve atrial cardiac arrhythmias. Specifically, the
invention provides a cure for atrial fibrillation by using
transcutaneous transvascular catheter ablation in an overlapping
pattern to produce the effect of the Cox Maze surgical
procedure.
[0005] II. Related Art
[0006] Cardiac arrhythmias, particularly atrial fibrillation, are
common and dangerous medical conditions causing abnormal, erratic
cardiac function. Atrial fibrillation is observed particularly in
elderly patients and results from abnormal conduction and
automaticity in regions of cardiac tissue. Chronic atrial
fibrillation (AF) may lead to serious conditions including stroke,
heart failure, fatigue and palpitations. The treatment of chronic
AF requires the creation of a number of transmural contiguous
linear lesions. The use of a pattern of surgical incisions and thus
surgical scars to block abnormal electrical circuits, and
passageways known as the Cox Maze procedure, has become the
standard surgical procedure for effective surgical cure of AF. The
procedure requires a series of full-thickness incisions to isolate
the pulmonary veins and the posterior wall of the left atria.
Additional lines involve the creation of lesions from the posterior
wall to the mitral valve, at the atrial isthmus line and superior
vena cava (SVC) to the inferior vena cava (IVC) with a connection
to the right atrial appendage.
[0007] Catheters have been developed that make the corrective
procedure less invasive. They are designed to create lesions by
ablation of tissue that performs the function of the surgical
incisions. These include catheters that attempt to connect a series
of local or spot lesions made using single electrodes into linear
lesions. Devices that use a linear array of spaced electrodes or
electrodes that extend along the length of a catheter have also
been used.
[0008] Important drawbacks found fundamental in the current
catheter-based ablation approaches can be attributed to several
factors including a lack of consistent contact between the ablation
devices and the target tissues, an inability to accurately evaluate
lesion maturation, and the inability to connect lesions in a manner
so as to create a continuous transmural line that produces a
continuous electrical conduction block. Therefore, there remains a
need for improved ablation devices and procedure techniques.
SUMMARY OF THE INVENTION
[0009] By means of one aspect of the present inventive concept,
there is provided an ablation catheter to enable an operator to
treat a patient suffering from an arrhythmia by employing an
overlapping ablation technique that increases the ablation
footprint and produces more reliable continuous lesions that
prevent reconnection of electrical pathways in cardiac tissue.
[0010] The catheter system, which may be exemplified in a number of
embodiments, includes an outer multi-directional deflection sheath
in the form of an elongate flexible, steerable sheath member having
a proximal end and a distal end. A lumen extends between the
proximal and distal ends. A catheter including an elongate outer
shaft and an elongate torqueable central control shaft core
coaxially received in the outer catheter shaft is disposed in the
outer sheath lumen and is in slidable relation with respect
thereto. Certain embodiments may have a plurality of central
control shafts as will be described.
[0011] The distal portion of the catheter includes an ablation
segment having a plurality of electrodes forming a combined
electrode array that includes an array of sequentially arranged,
spaced ablation electrodes and an array of spaced recording and
thermistor electrodes. The combined electrode array is designed to
be formed in a tight loop configuration for an ablation procedure.
The array of spaced recording and thermistor electrodes may
preferably be interspersed with the ablation electrodes. The
ablation electrodes are preferably operated by radio frequency (RF)
power.
[0012] In some embodiments, the ablation segment, with the combined
electrode array, is initially arranged as a generally linear
extension of the distal portion of the catheter and is provided
with a distal pull wire-type device that extends proximally such
that it can be caused to be retracted from the proximal end of the
sheath. This causes the attached electrode array to assume a loop
configuration, the size of which can be adjusted as needed.
Alternatively, the ablation segment may be arranged in a fixed
tight loop with both ends attached to the catheter shaft having a
collapsible configuration which can be squeezed together to be
accommodated in a corresponding sheath, which may require a
slightly larger diameter, possibly about 9.5 F vs 8 F, for this
embodiment. Further embodiments may incorporate an electroded
central membrane associated with the loop. The central membrane
insulates adjacent blood from the procedure and may also be
provided with recording, temperature sensing and pacing devices to
monitor lesion formation and maturation. Irrigation may also be
provided via the membrane.
[0013] The catheter further preferably incorporates an irrigation
system that supplies irrigation fluid to cool the electrodes and
prevent char formation. The system is configured to allow equal
flushing of each of the plurality of ablation electrodes during the
ablation procedure. Fluid is supplied through one or more
irrigation channels in the catheter shaft and connections to the
electrodes. The catheter shaft, of course, also accommodates
conductors attached to each ablation and recording electrode.
[0014] Preferred formed ablation loops in accordance with the
invention may be various sizes, but they are generally defined as
"small loops" which may have a nominal width from about 10 mm to 20
mm and a nominal length from about 20 mm to 30 mm. A preferred size
is about 15 mm wide by about 25 mm long.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the drawing figures wherein like numerals depict like
parts throughout the same:
[0016] FIG. 1A depicts a fragmentary schematic view illustrating
the distal end of an ablation catheter system in accordance with
the invention having an ablation segment that is arranged for
transport in a sheath as a generally linear extension of the distal
portion of the catheter;
[0017] FIG. 1B depicts the embodiment of FIG. 1A with the ablation
segment pulled into a loop configuration by a pull wire;
[0018] FIG. 2 is a greatly enlarged schematic cross section view of
the main catheter shaft of the embodiment of FIGS. 1A and 1B;
[0019] FIG. 3 illustrates a view similar to FIGS. 1A and 1B in an
embodiment of the invention in which the ablation segment is in the
form of a fixed loop attached to the distal end of the
catheter;
[0020] FIGS. 4 is a schematic cross sectional representation of the
catheter shaft of FIG. 3;
[0021] FIG. 5 depicts a schematic view of an embodiment similar to
that of FIGS. 3 and 4 wherein the center of the loop is covered
with a membrane;
[0022] FIG. 6 illustrates the creation of a chain link lesion;
[0023] FIG. 7 illustrates the bulging of tissues encircled by the
loop of a catheter in accordance with the invention as it is
compressed into tissue to be ablated;
[0024] FIG. 8 is a partial internal representation of a heart
illustrating a left atrial lesion set directed at the isolation of
the pulmonary veins, isolation of the left atrial posterior wall
and septal, as well as the left atrial isthmus; and
[0025] FIG. 9 is a computed tomography scan of a left atrial lesion
set directed at the isolation of the pulmonary veins (2 veins at a
time) and a connecting lesion between the pulmonary vein isolation
lesions and the left atrial isthmus lesion.
DETAILED DESCRIPTION
[0026] The following detailed description pertains to several
embodiments that feature aspects of the concepts of the present
development. These embodiments are meant as examples and are not
intended to limit the scope of the present invention in any
manner.
[0027] The present invention provides catheters useful for
evaluating tissue temperature and conduction, and for performing
targeted tissue ablation procedures. The catheters include an outer
sheath having an elongated tubular body that includes a proximal
and a distal end and a lumen extending the length of the sheath for
receiving a catheter in slidable relation in the lumen. The
catheters are generally of a type used for performing intracardiac
procedures and are preferably introducible through a
previously-placed sheath that had been inserted into the femoral
vein and maneuvered via the Inferior vena cava (IVC). For ablation
in the left atria, the sheath is guided first into the right atria.
Under intracardiac ECHO visualization, or the like, the deflectable
sheath is caused to penetrate the intra-atrial septum and the
sheath is then positioned in the left atria. The ablation catheter
is then introduced through the sheath and delivered to the left
atria via the sheath. The catheter has a steerable tip that allows
it to be precisely positioned as required for the ablation
procedure. The catheter includes ablation elements mounted on a
distal ablation segment designed to be utilized in a tight loop
formation. The ablation segment contains electrode elements
designed to both ablate and map the electrical activity of tissue.
The array must be sufficiently stiff in use such that it may be
applied with sufficient force against tissue to be ablated.
[0028] Generally, after performing an electrical mapping procedure,
the operator positions the ablation electrode loop as desired and
utilizes energy provided by an external source such as radio
frequency (RF) energy to ablate the tissue in desired areas. The
goal of the catheter ablation procedure is to permanently disrupt
the electrical pathways in cardiac tissue to stop the emission and
propagation of erratic electrical impulses in the tissue. Once
ablated, the tissue no longer conducts such impulses.
[0029] The catheters of the present invention are configured to
accomplish the mapping and ablation procedure utilizing an array of
electrodes arranged in a tight loop, which may be formed by the use
of a distally connected pull wire which deflects a basically linear
arrangement of electrodes into a loop or by the use of a fixed loop
at the distal end of the catheter. As will be discussed, the use of
a tight loop enables the establishment of a series of overlapping
loop-shaped lesions that produce a continuous "chain link"
footprint that greatly improves linear continuity in the
lesion.
[0030] FIGS. 1A and 1B depict fragmentary schematic views
illustrating the distal end of an ablation catheter system in
accordance with the invention. The system is shown generally at 20
and includes an outer steerable and deflectable sheath 22 and
catheter shaft 24. An ablation segment is attached to the distal
end of the catheter shaft and is shown with a linear array of
spaced electrode devices, including radio frequency (RF) ablation
electrodes 26 and interspersed recording/thermistor pin-type
electrodes 28, which function as temperature sensors, determine
tissue contact, evaluate lesion maturation, map and record
conduction with high fidelity. An attached pull wire is shown at
30. The ablation electrodes 26, which may be platinum or platinum
alloy wound wire, for example, are typically about 6 F in width by
about 6 mm long and spaced about 2 mm apart. The example shown in
FIGS. 1A and 1B incorporates a distal ablation segment that has a
total length of about 50 mm. The recording/thermistor electrodes
are about 1 mm.sup.2 in size.
[0031] The loop shown in FIG. 1B is formed by retracting the pull
wire 30 which extends to the proximal end of the sheath 22. The
loop size can readily be adjusted by advancing the catheter shaft
in the sheath to maximize the loop size or by retracting the
catheter shaft to withdraw part of the ablation segment into the
catheter to shrink the size of the loop.
[0032] FIG. 2 is a greatly enlarged schematic cross sectional view
of the main catheter shaft of the embodiment of FIGS. 1A and 1B.
The catheter shaft includes a central control shaft of variable
stiffness 32 with core 34 and a hollow irrigation tube 36.
Recording and thermistor electrical conductors are shown at 38 and
ablation electrode conductors are depicted at 39. The irrigation
tube 36 is connected to each of the ablation electrodes 26 by
branch connectors that are configured to supply like amounts of
irrigation or cooling fluid to each of the ablation electrodes.
[0033] A slightly different embodiment is shown in the fragmentary
schematic view of FIG. 3 in which a different configuration of a
catheter shaft 40 is provided with a fixed loop ablation segment 42
that is attached at both ends to the catheter shaft 40. The loop
includes a soft collapsible nose segment 44, ablation electrodes 46
and recording/thermistor electrodes 48. The soft collapsible nose
segment 44 permits the ablation loop to be compressed and inserted
into the sheath for transport. The distal end of the catheter shaft
40 is provided with a deflection capability to add additional
degrees of freedom and flexibility to the deflection capability of
the sheath in maneuvering the loop during a procedure.
[0034] FIG. 4 depicts a schematic cross sectional representation of
the catheter shaft of the embodiment of FIG. 3. The main catheter
shaft 40 includes a pair of spaced internal loop shaft members 50
and 52, one connected to each side of the fixed loop ablation
segment 42. The shaft 50 includes a variable stiffness shaft and
core 53 that is independently torqueable, recording/thermistor
electrode conductors 54, ablation electrode conductors 56 and an
irrigation tube 58 that supplies irrigation fluid to cool the
electrode of the corresponding side of the fixed loop ablation
segment, each ablation electrode having an irrigation port. The
internal shaft member 52 contains the same devices and these
include independently torqueable shaft and core 60,
recording/thermistor electrode conductors 62, ablation electrode
conductors 64 and irrigation tube 66 that service the other
corresponding section of the fixed loop ablation segment 42. Thus,
the irrigation connections and electrical connections enter the
loop from both ends.
[0035] As with the previous embodiment, the irrigation channels
enable the flushing of the ablation electrodes during the
application of RF power and low level irrigation to maintain the
integrity of the associated irrigation ports at other times. The
ablation electrodes may be wire wound sections, each containing an
irrigation port supplied by an irrigation conduit supplied from a
main irrigation tube. The irrigation system is designed so that the
most distal electrode receives the same irrigation pressure as the
most proximal. This may be done by well-known techniques to adjust
the flow resistance.
[0036] FIG. 5 shows a schematic view of a fixed loop catheter
embodiment similar to that shown in FIGS. 3 and 4, but in which the
open center portion of the loop is covered with a membrane 70. The
membrane is provided with additional sensing/pacing electrodes as
at 72 and an irrigation tube 74. The membrane allows an amount of
irrigation fluid to accumulate within the enclosed space under the
membrane when the loop is pressed against tissue during ablation.
The membrane insulates the tissue being ablated from circulating
blood and allows accurate tissue heating. The recording and pacing
capability permits monitoring of lesion formation and accurate
assessment of tissue electrical isolation post ablation. Pacing can
be used during the ablation process as it has been found that, when
cardiac pace capture is lost during ablation, that signifies
completion of a lesion.
[0037] FIG. 6 illustrates the creation of a chain link lesion. A
sheath fragment is shown at 80, carrying associated catheter 82
with ablation segment 84 is used repeatedly in overlapping fashion
to create a series of overlapping ablation links as footprints 86.
The links may be any desired size and typical links as illustrated
are about 10 mm wide by 15 mm long and overlapped to produce a
continuous "chain link" lesion.
[0038] FIG. 7 schematically illustrates an effect of compression of
the loop into adjacent tissue which results in a corresponding
bulging of the tissues encircled by the loop, particularly at the
center of the loop. The figures includes a multi-directional
deflectable sheath fragment 90 with extended distal catheter at 92
and a catheter ablation segment formed into a loop at 94 with
ablation electrodes 96 and recording/thermistor devices 98 arranged
as in previous embodiments. The bulging of the tissue is
illustrated by curved segment 100 and inter-ablation electrode
conduction paths are illustrated by the lines 102, which indicate
the use of a bipolar technique. The bulging of the tissue at the
center of the loop has been found to enable bipolar RF current to
more effectively ablate the tissue in accordance with the operation
of the loop ablation catheter of the invention.
[0039] FIGS. 8 and 9 illustrate lesion sets formed by utilizing the
chain link technique of the present invention. In FIG. 8, the left
atrial lesion set is directed at isolation of the pulmonary veins,
isolation of the left atrial posterior wall and septal, as well as
the left atrial isthmus. In the right atrium, there is shown a
catheter system 110 in the process of creating an intracaval lesion
at 112.
[0040] In FIG. 9, there is shown a computer tomography scan of a
left atrial lesion set which is directed at the isolation of the
pulmonary veins (two veins at a time) at 120 and 122. A connecting
lesion between the pulmonary vein isolation lesions in the left
atrial isthmus lesion is shown at 124.
[0041] It should be noted that the term "ablation" or "ablation
procedures" refers to procedures in which tissue is destroyed in a
manner that disconnects or isolates pathways of abnormal electrical
activity. The term "ablation electrode" refers to an energy
delivery element used to deliver electrical energy such as RF
energy. The high concentration of energy near the electrode results
in localized tissue ablation. The energy delivery can be monopolar
or bipolar. With bipolar energy delivery, the energy is conducted
from one electrode to one or more other electrodes in an array of
associated electrodes. Bipolar energy delivery enables closer
control of the amount of tissue ablated and is, therefore,
preferred for the loop catheter of the present invention. The
timing of the application of the energy may also be varied and may
controlled by temperature feedback from sensor electrodes which may
also be used to record and map electrical activity in the tissue.
RF electrodes may be constructed from platinum or a platinum alloy
that may be in the form of a solid member or, preferably, a wire
coil.
[0042] It should be recognized that the pattern of ablated tissue
created by the incremental use of the small loop catheter of the
present invention leaves little possibility for gaps in a desired
lesion pattern as it provides a series of overlapping footprints
that give more reliable results than a series of spaced
electrodes.
[0043] This invention has been described herein in considerable
detail in order to comply with the patent statutes and to provide
those skilled in the art with the information needed to apply the
novel principles and to construct and use such specialized
components as are required. However, it is to be understood that
the invention can be carried out by specifically different
equipment and devices, and that various modifications, both as to
the equipment and operating procedures, can be accomplished without
departing from the scope of the invention itself.
* * * * *