U.S. patent application number 17/483533 was filed with the patent office on 2022-01-20 for catheter systems for cardiac arrhythmia ablation.
The applicant listed for this patent is Boaz Avitall. Invention is credited to Boaz Avitall.
Application Number | 20220015827 17/483533 |
Document ID | / |
Family ID | 1000005872235 |
Filed Date | 2022-01-20 |
United States Patent
Application |
20220015827 |
Kind Code |
A1 |
Avitall; Boaz |
January 20, 2022 |
Catheter Systems for Cardiac Arrhythmia Ablation
Abstract
A plurality of catheter-based ablation apparatus embodiments are
provided that address several areas of atrial target tissue and
which feature firm and consistent ablation element to tissue
contact enabling the creation of effective continuous lesions.
Inventors: |
Avitall; Boaz; (Milwaukee,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Avitall; Boaz |
Milwaukee |
WI |
US |
|
|
Family ID: |
1000005872235 |
Appl. No.: |
17/483533 |
Filed: |
September 23, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12961781 |
Dec 7, 2010 |
|
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17483533 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2018/00375
20130101; A61B 2018/0022 20130101; A61B 2018/00815 20130101; A61B
2018/00351 20130101; A61B 2018/00577 20130101; A61B 2018/00791
20130101; A61B 2018/00357 20130101; A61B 2018/00875 20130101; A61B
18/02 20130101; A61B 18/1492 20130101; A61B 2090/065 20160201; A61B
2018/00369 20130101; A61B 18/24 20130101; A61B 2018/00023
20130101 |
International
Class: |
A61B 18/14 20060101
A61B018/14; A61B 18/02 20060101 A61B018/02 |
Claims
1-86. (canceled)
87. A device for ablating selected tissue in a body organ chamber,
including heart chambers, comprising: (a) a guide body sheath
having a deflectable distal end portion; (b) an electrodeless
guidewire having relatively stiff and soft portions and adapted to
exit and reenter said deflectable distal end portion of said guide
body sheath to form a stable electrodeless guidewire loop that is
controllable in the body organ chamber to create forced contact
with selected tissue of the heart; (c) a catheter guide shaft
having an ablating energy element adapted for creating a lesion on
the selected tissue, the catheter guide shaft able to travel over
and be fully supported by said electrodeless guidewire, said
electrodeless guidewire being of sufficient stiffness and
controllable to create forced contact between said ablating energy
element and said selected tissue at a plurality of desired
locations along said stable electrodeless guidewire loop; (d) a
control handle at a proximal portion of said guide body sheath
operatively coupled to the electrodeless guidewire and containing a
loop control slide element comprising first and second guidewire
locks whereby the size, shape and disposition of the loop can be
adjusted and fixed.
88. The device for ablating the selected tissue as in claim 87
wherein manipulation of the control handle loop control slide
element allows the ablating energy element to make contact with
said selected tissue in the body organ chamber at multiple
locations and thereby create continuous lesions.
89. The device for ablating the selected tissue as in claim 87
wherein said ablating energy element further comprises a plurality
of thermistors and a plurality of electrodes insulated from one
another for temperature monitoring and real-time electrical
activity assessment of lesion maturation.
90. The device for ablating the selected tissue as in claim 87
wherein said control handle loop control slide element comprises a
movable locking device connected to said catheter guide shaft for
controlling a position of said ablating energy element along said
electrodeless guidewire.
91. The device for ablating the selected tissue as in claim 87
wherein said ablating energy element comprises an ablation balloon
device that is made to contain a cryogenic fluid that is selected
from the group consisting of liquid nitrous oxide (N.sub.2O) and
other cryogenic fluids.
92. A device for ablating selected tissue comprising: (a) a guide
body sheath having a deflectable distal end portion with an opening
therein; (b) an ablation catheter sheath extendable from said
deflectable distal end portion of said guide body sheath and having
a J-shaped distal end portion configured with a leading 180.degree.
guiding bend that enables guiding of the device into a pulmonary
vein orifice or other conduit and which continues in a form of a
trailing loop which is provided with an array of spaced recording
and stimulation elements configured to extend circumferentially
around an interior surface of said pulmonary vein orifice or other
conduit; (c) a cryogenic ablation balloon device on said ablation
catheter sheath, said cryogenic ablation balloon device being
guided, supported on, stabilized and anchorable in position just
proximal to said J-shaped distal end portion by said ablation
catheter sheath; (d) a control handle disposed at a proximal end of
the guide body sheath for controlling an extension of said ablation
catheter from said guide body sheath, said control handle
comprising a locking member whereby the disposition of the ablation
catheter sheath can be adjusted and fixed; and (e) wherein said
cryogenic ablation balloon device further comprises a distal ring
electrode placed distal to the entire inflatable ablation balloon
device and a proximal ring electrode placed proximal to the
cryogenic ablation balloon device for measuring impedance during a
cryogenic ablation procedure for determining an extent of ice
formation on the distal ring electrode, indicative of
circumferential ice formation on the outer balloon that extends to
cover the distal ring electrode indicating pulmonary vein occlusion
and lesion adequacy and maturation.
93. The device for ablating the selected tissue as in claim 92
wherein when said cryogenic ablation balloon device is adapted to
be placed in a pulmonary vein orifice whereby pulmonary vein
occlusion and continuous circumferential ablation can be assessed
by impedance measurements between said proximal ring electrode and
said distal ring electrode obtained when a low-power,
high-frequency voltage is applied therebetween.
94. The device for ablating the selected tissue as in claim 92
wherein said inflatable cryogenic ablation balloon device is
connected to said ablation catheter sheath that is arranged to
travel over a guidewire.
95. The device for ablating the selected tissue as in claim 92
wherein said control handle is also configured to adjust a position
of the cryogenic ablation balloon device riding on said ablation
catheter sheath.
96. The device for ablating the selected tissue as in claim 92
wherein said stable electrodeless guidewire loop includes a tip
segment attached to the deflectable distal end portion of the guide
body sheath.
97. A device for ablating selected tissue comprising: (a) A
catheter; (b) a catheter handle; (c) a controller apparatus coupled
to the catheter handle; (d) an ablation/recording device coupled to
the catheter handle; (e) a guidewire extending from the catheter
handle, said guidewire comprising a proximal end, a stiff body,
soft distal end, and a loop; (f) an ablation delivery sheath
comprising an ablation element positioned on the ablation delivery
sheath, wherein the controller apparatus is adapted to lock the
soft distal end of the guidewire in place, allow the proximal end
of the guidewire to be extended and retracted to adjust the size of
the loop, and lock the proximal end of the guidewire in place to
fix the size of the loop; and wherein the ablation/recording device
assess movement and position of the ablation/recording element.
98. The device for ablating selected tissue of claim 97 wherein the
ablation element is a balloon.
99. The device for ablating selected tissue of claim 97 wherein the
ablation delivery sheath is a deflectable transeptal sheath.
100. The device for ablating selected tissue of claim 97 wherein
the ablation/recording element includes a measuring ruler placed on
a sliding track.
101. The device for ablating selected tissue of claim 97 wherein
the loop is formed by extending the soft distal end of the
guidewire and a selected portion of the stiff body portion of the
guidewire from a distal end of the ablation delivery sheath and
causing the soft distal end of the guidewire to reenter the
ablation delivery sheath.
102. A device for ablating selected tissue comprising: a. an
ablation/recording element having a shaft and adapted to create a
continuous lesion and permit recording; b. an anchoring J shaped
guidewire with a soft distal end and stiff body adapted to be
inserted into an anatomical location and allow the ablation element
to be tracked over the guidewire; and c. a J-shaped multi-electrode
lasso catheter adapted to be inserted via the shaft of the
ablation/recording element.
103. The device for ablating selected tissue of claim 102 wherein
the ablation/recording element comprises a cryo-balloon device
including a balloon, a distal ring of a small width placed at an
anterior surface of the balloon, and a proximal ring, wherein said
distal ring and said proximal ring are adapted to measure
impedance.
104. The device for ablating selected tissue of claim 103 wherein
rising impedance is correlated with of ice formation and lesion
maturation.
105. The device for ablating selected tissue of claim 102 wherein
the balloon is adapted to allows electrical recording over the
surface of the ablation/recording element and impedance recording.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
12/961,781, filed Dec. 7, 2010, entitled "CATHETER SYSTEMS FOR
CARDIAC ARRHYTHMIA ABLATION", which is deemed incorporated herein
by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
I. Field of the Invention
[0003] The present invention relates generally to the field of
catheter-based tissue ablation devices and techniques and, more
particularly, to systems for ablation to relieve atrial cardiac
arrhythmias. Specifically, the invention relates to curing atrial
fibrillation by using transcutaneous transvascular catheter
ablation to recreate the effect of the Cox Maze surgical
procedure.
II. Related Art
[0004] 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, known as the
Cox Maze procedure, has become the standard 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.
[0005] 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 proposed.
[0006] More recently, technologies regarding cryogenic and radio
frequency (RF) balloon devices in addition to loop type
multi-electrode catheter devices have been proposed for the
isolation of the pulmonary veins (PV). It has been found that
isolation of the PVs can be achieved consistently with a PV
cryogenic balloon device now in clinical trials. However, presently
no technology has been shown to consistently and safely create
effective transmural contiguous lesions that exhibit an
effectiveness that rivals the surgical cuts placed in the Cox
Maze.
[0007] Important drawbacks found fundamental in the current
approaches can be attributed to several factors including a lack of
consistent contact between the ablation devices and the target
tissues, an inability to define lesion maturation and the inability
to connect lesions in a manner so as to create a continuous
transmural line that produces an electrical conduction block.
SUMMARY OF THE INVENTION
[0008] In accordance with the present invention a plurality of
catheter-based ablation apparatus embodiments are provided that
address several areas of atrial target tissue and which feature
firm and consistent ablation element-to-tissue contact enabling the
creation of effective continuous linear lesions.
[0009] The ablation devices of the invention all are extended from
the distal portion of a main guide body or deflectable sheath that
is capable of penetrating heart septum tissue to enter the desired
chamber. Transeptal guide body sheath devices are known to those
skilled in the art. The distal portion of the guide body or sheath
is preferably further provided with an inflatable balloon device to
prevent the sheath from retracting back through the penetrated
septum during a procedure. This could result in damage to the
septum caused by a protruding guidewire or the like. This
protective balloon can be expanded using a benign solution such as
saline or saline mixed with contrast for visualization.
[0010] Several embodiments of ablation devices of the present
concept are in the form of inflatable balloons which are attached
to and positioned using an expandable guidewire loop which is
anchored at one end in a deflectable catheter sheath. The length of
the guidewire loop emanating from the guide body or sheath is
adjustable and can be controlled to press with force against and
firmly adhere to adjacent atrial tissue. A balloon ablation device
is adapted to be advanced over the guidewire in a deflated
condition until the balloon is in a desired position along the
loop. Once the balloon is properly positioned, it can be expanded
and moved and positioned along the guidewire in an expanded state
and thereby allow delivery of radio frequency (RF) or cryogenic
energies to the targeted tissue for ablation. An end of the
guidewire loop or attached pull line fixes the end of the guidewire
with respect to the distal end of the sheath. The guidewire loop
within the atria can be expanded by inserting additional guidewire
into the sheath from a control handle or the loop can be shrunk by
retracting guidewire out of the sheath. These actions can be used
to control the size and disposition of the guidewire loop.
[0011] The balloon embodiments generally may be of two or more
types, ones that use radio frequency (RF) energy to ablate tissue
with heat and ones that use cryogenics to ablate tissue by
freezing. However, other energy forms can be used such as laser
energy. Radio frequency (RF) ablation balloons have an outer
surface provided with a plurality of segmented RF ablation
electrodes and thermistors to measure temperature. RF ablation is
closely monitored with respect to RF power, electrode temperature
and observance of local electrogram amplitude and percent change.
Overheating of ablated tissue may cause serious problems and RF
electrodes are preferably cooled during RF application by
circulating cooling saline solution or the like which may also
contain a contrast material for easier location tracing. The
ablation balloon includes several elements that enable
determination of its three-dimensional position, tissue temperature
and electrical activity (local electrogram) during the ablation
process. Pressure and surface temperature can be precisely measured
and monitored by imbedded temperature and pressure sensors. The
balloon temperature can be controlled by the saline circulation
that is used to cool the balloon allowing higher delivered power to
create deeper lesions if needed.
[0012] Cryogenic balloon embodiments are also designed to be
delivered over a guidewire delivery and tracking system. The
cryogenic balloon preferably consists of two concentric balloons,
an inner and an outer balloon. The inner balloon is adapted to
receive and contain the cryogenic fluid, normally liquid nitrous
oxide (N.sub.2O) under pressure and the outer balloon is filled
with a low pressure insulating gas highly absorbable in blood such
as nitrogen (N.sub.2) or carbon dioxide (CO.sub.2) at a pressure
just above the normal pressure in the atria. In this manner, the
outer balloon serves to insulate the cryogenic fluid in the inner
balloon from the warm atrial blood flow, thus reducing the effects
on the blood and allowing much of the cryogenic power to be
directed to the targeted tissues.
[0013] Expansion of the relatively stiff guidewire loop forces the
inner balloon toward and against the tissue resulting in
displacement of the insulating gas in the outer balloon where the
tissue is engaged causing the two balloons to be in firm contact
with each other and the tissue, thus allowing maximal freezing
effect to be directed into the tissues of interest at that
interface. In addition, two ring electrodes may be preferably
placed on the distal and proximal end allowing both electrical
recording and positioning of the catheter using presently known 3D
guiding systems. In addition, as mentioned above, embedded
thermistors and additional electrical recording electrodes can be
painted on the surface of the outer balloon and used for cardiac
electrical mapping, and lesion assessment. A simpler embodiment may
consist of a single layer cryogenic balloon with segmented painted
surface electrodes and thermistors.
[0014] An additional anchoring approach involves embedding a soft
distal portion of a stiff guidewire in the left atrial appendage
and tracking the ablation balloon over the guidewire to create
linear lesions. The same type of RF ablation catheter can be guided
by the same or similar guidewire into the PVs for the creation of
circumferential PV isolation lesions.
[0015] By means of the invention, there is also provided
embodiments of a catheter system that use the pulmonary vein (PV)
entrances as base anchors for a multi-electrode system for the
creation of linear lesions between the pulmonary veins (PVs). These
linear lesions are needed to electrically isolate the posterior
wall of the left atrium between the PVs, an area that has been
shown to be an active driver of atrial fibrillation (AF).
[0016] The pulmonary vein anchored embodiments include a transeptal
sheath, nominally a 10-11 F sheath, used to cross the atrial septum
and access the left atrium. Two additional sheaths are placed
inside the transeptal sheath which are configured with fixed
deflections that allow insertion of each of the sheaths into a PV.
These sheaths provide the anchors and support for a multi-electrode
catheter ablation segment that forms a bridge between the
supporting sheaths. By stretching the ablation-electroded segment
of the catheter, a good tissue contact is formed and a transmural
and contiguous lesion can be placed between pulmonary veins. By
placing the support sheath anchors in different PVs, linear lesions
between all of the PVs can be created. These lesions are normally
additional lesions that are placed after isolation of the PVs by
either RF or cryogenic balloon lesions are provided, as described
above. These embodiments have an advantage since they allow for
force to be applied to the catheter at the tissue interface,
thereby creating good ablation electrode and tissue contact
ensuring a good lesion.
[0017] In an additional embodiment the ablation catheter is placed
within a guiding deflectable sheath and by pushing the catheter
into the sheath a rigid loop is created which moved to create
contact with the tissues by moving or deflecting the guide sheath.
To minimize the size of the guide sheath one side of the ablation
catheter can be flexibly attached to the end of the sheath and
thereafter adjusting the catheter into and out of the sheath
creates an expanding loop. Another option is to insert the ablation
catheter into the sheath with a pull string attached to the distal
end of the catheter. Once the catheter is in the desired chamber,
the pull string can be retracted to bring the end of the
multi-electrode ablation catheter against the tip of the sheath to
create a loop by pushing the proximal end of the ablation catheter
into the sheath.
[0018] An electrically insulated extension rod can be attached to
the ablation electrode array to further assist with the loop
expansion and tissue contact.
[0019] The balloon catheters of the present invention can also be
combined with an attached J-loop shaped PV recording and impedance
measuring catheter segment provided with recording and stimulation
electrodes to record electrical activity and verify pulmonary vein
(PV) isolation and lesion quality.
[0020] The last embodiment allows the radio frequency generator to
direct the RF application to the electrode that are in firm contact
with the tissues and titrate the power application time based on
the tissue viability. This approach to the ablation will prevent
extracardiac tissue damage while insuring lesion maturation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In the drawing figures:
[0022] FIG. 1 is a schematic representation of an embodiment
including a radio frequency (RF) balloon ablation device with
segmented electrodes controlled by an adjustable loop guidewire
system;
[0023] FIG. 2 is a schematic representation that depicts an
embodiment including a cryogenic balloon ablation device having
inner and outer concentric balloons that travel along an adjustable
loop guidewire;
[0024] FIG. 3 is a partial schematic representation depicting a
balloon ablation device with a control handle suitable for use with
the balloon ablation catheter devices of the invention;
[0025] FIGS. 4A-4E show different positions of the ablation balloon
device and a variety of shapes and loops that can be created by the
adjustable guidewire with a pull line;
[0026] FIG. 5 is a schematic representation of an RF or cryogenic
balloon ablation device as positioned in the left atrium using a
loop guidewire for the creation of a circumferential lesion;
[0027] FIG. 6 is a schematic representation depicting an RF or
cryogenic balloon ablation device using an anchoring guidewire
anchored in the left atrium appendage;
[0028] FIG. 7 is a schematic diagram showing an RF or cryogenic
ablation balloon with segmented electrodes and thermistors guided
by a guidewire in the left superior pulmonary vein (LSPV) for the
creation of a pulmonary vein (PV) isolation lesion;
[0029] FIG. 8 is a schematic representation of a balloon catheter
combined with a J-loop pulmonary vein recording and impedance
measurement catheter device capable of measuring PV occlusion and
lesion quality, maturation and electrical isolation;
[0030] FIG. 9 depicts schematic representations of multi-electrode,
loop-type catheters for the creation of linear lesions;
[0031] FIG. 10 is a schematic representation of a catheter similar
to that of FIG. 9 showing anchoring support sheaths inside
pulmonary veins for linear lesion placement between the right
superior pulmonary vein (RSPV) and left superior pulmonary vein
(LSPV);
[0032] FIG. 11 is a schematic representation similar to that of
FIG. 10 for linear lesion placement between left superior pulmonary
vein (LSPV) and left inferior pulmonary vein (LIPV);
[0033] FIG. 12 is a schematic representation similar to that of
FIG. 10 for linear lesion placement between left inferior pulmonary
vein (LIPV) and right inferior pulmonary vein (RIPV);
[0034] FIG. 13 is a schematic representation similar to that of
FIG. 10 for linear lesion placement between right inferior
pulmonary vein (RIPV) and right superior pulmonary vein (RSPV);
[0035] FIG. 14 is a schematic representation of an alternate
embodiment of a multi-electrode loop-type catheter which includes
an insulated extension rod;
[0036] FIG. 15 illustrates the multi-electrode catheter of FIG. 14
as it might be used to create linear lesions between pulmonary
veins; and
[0037] FIG. 16 is a schematic and partial block diagram of an
ablation control system.
DETAILED DESCRIPTION
[0038] The following detailed description pertains to several
embodiments that include concepts of the present development. Those
embodiments are meant as examples and are not intended to limit the
scope of the present invention in any manner.
[0039] It will be appreciated that the present development
contemplates a less invasive yet comparably effective solution to
atrial fibrillation that replaces the surgical lesions of the
traditional Cox Maze with lesions created by tissue ablation using
catheters which avoids the need for radical surgical procedures.
The ablation devices of the invention provide firm and consistent
ablation surface to tissue contact.
[0040] FIG. 1 is a schematic representation of an embodiment of an
RF balloon ablation device generally depicted by the reference
character 20. The ablation device includes an ablation balloon 22,
shown as inflated, mounted on a flexible catheter shaft 24 that may
be a 7 F flexible catheter guide shaft that is about 4 feet (122
cm) long. All of the ablation control and data measurement
conductors or wires are embedded in the shaft wall that rides over
a guidewire 26. The most distal section of the guidewire 26 is
about 2 cm long and is of a relatively soft, flexible, material,
which is softer and more flexible than the remainder of the loop,
which is relatively stiff. The guidewire may be attached to or
drawn through the distal end of a deflectable transdermal sheath, a
fragment of which is shown at 28. A transeptal breach protection
balloon, which is inflated, normally with saline to prevent
undesirable withdrawal of the sheath 28 during a procedure, is
shown at 30. The position of the catheter can be adjusted by moving
the adjustable shaft 24 relative to the guidewire 26 using a
proximal handle control as shown in FIG. 3.
[0041] The balloon 22 further includes a plurality of segmented
conductive painted RF electrodes 32, each of which is provided with
a centrally located recording electrode for sensing electrical
activity and a combined recording and thermistor elements 34 for
sensing temperature. The electrodes are highly conductive paintings
on the balloon surface and can be selectively and separately
energized and sensed in a well known manner. While the balloon
itself may be any convenient size, a typical embodiment will be
about 25-30 mm long by 15 mm in diameter when fully inflated. Such
balloons may be made of any suitable benign coatable polymer
material that maintains stable inflated dimensions and is
constructed to include separated conductive segments for tissue
ablation, thermistors placed at the center of each ablation
electrode as well as a recording electrode. One such preferred
material is polyethylene teraphthalate (PET), and it is believed
that other suitable materials could be used.
[0042] As indicated, the RF balloon is coated with a highly
conductive compound painted on the balloon in electrode segments 32
as shown in FIG. 1. The balloon of one typical preferred embodiment
measures about 30 mm in length and has a diameter of about 15 mm.
The balloon preferably has eight segmented conductive painted
electrode segments 32 separated by non-conducting bands, as at 36,
which may be about 1.5 mm wide. The combined recording and
thermistor elements are generally about 2 mm in diameter and are
separated from the conductive segments 32 by a 1 mm insulating
outer ring 35. The recording electrodes and thermistors, located
generally at the center of each ablation element, monitor the pre
and post ablation electrical activity and monitor temperature. The
RF ablation balloon is preferably filled with saline mixed with low
concentration of contrast fluid under low pressure. The saline is
circulated inside the balloon while maintaining constant inner
balloon pressure to keep the balloon itself cool and allow for more
effective ablation.
[0043] FIG. 2 depicts an embodiment of a cryogenic ablation device
in accordance with the invention that uses a dual balloon system
including both a cryogenic balloon and a low pressure insulating
balloon for thermal insulation. The dual balloon construction
includes an inner cryogenic balloon 42 and an outer insulating
balloon 44. Ring electrodes 46 and 48 are located at the distal and
proximal ends of the balloon, respectively, to provide electrical
activity recording and positional verification. Embedded
thermistors and recording electrodes, represented at 50, are also
located at desired points on the outer balloon and connected in a
well known manner. The balloon device is mounted on a flexible
catheter guide shaft 52 that rides over the guidewire 54. As was
the case with the RF device, the position of the balloon can be
changed by pulling or pushing the balloon catheter guide shaft over
the guidewire. The recording electrodes enable cardiac electrical
mapping and lesion assessment. The deployment system may be similar
to that for the RF balloon shown in FIG. 1. Thus, a guidewire loop
is shown at 54 with relatively soft flexible section which may be
attached through the end of a deflectable sheath 56 attached to a
pull cord (not shown). Sheath 56 includes a transeptal protection
balloon at 58.
[0044] In the two balloon cryogenic systems, the inner balloon
receives and contains a cryogenic liquefied material which may be
liquid nitrous oxide (N.sub.2O), which boils at -88.5.degree. C.,
and the outer balloon is filled with an insulating gas such as
CO.sub.2 or N.sub.2 at a pressure just above the left atrial
pressure. In this manner, the cryogenic liquid gas is normally
insulated from the inner atrial blood flow. During ablation,
expansion of the guidewire loop is used to force the balloon
towards the tissue at locations of interest and the force displaces
the insulating gas in the area of tissue contact thereby enabling
the cryogenic inner balloon to come into firm contact with the
outer balloon which produces maximum heat transfer between the
balloon and the tissue resulting in maximum local tissue
freezing.
[0045] A control handle is provided (FIG. 3) to advance the balloon
shaft over the guidewire and adjust its position on the guidewire
as illustrated in FIGS. 4A-4E.
[0046] FIG. 3 shows a schematic representation of an embodiment of
a balloon catheter ablation system generally at 80 including a flat
control handle member 81 that includes an RF/cryogen connector 82
for applying fluid materials to a balloon 88. An ablation
(RF/cryogen) balloon catheter having a proximal end catheter shaft
gliding or operating handle 83 is shown extending into a guide
sheath 84. The proximal end handle 83 is the proximal end of the
balloon ablation catheter shown at 90. The catheter is slidably
mounted over the guidewire 86 and both are delivered to the atria,
or other chamber, via the guide sheath 84. The ablation balloon
catheter shaft is inserted into the deflectable sheath over the
relatively stiff portion of the guidewire. The relatively soft
portion of the guidewire is extended from the sheath and can be
locked in place to prevent the guidewire from drifting or moving
further into the sheath when the balloon catheter is moved along
the guidewire. To accomplish this, a movable locking device
represented at 87 is provided. The position of the balloon along
the guidewire loop can be changed by moving the catheter proximal
end handle 83 along and over the guidewire section 86. A guidewire
fixation lock is shown at 92. It allows a variable length guidewire
fixation point to vary the size of the projected loop and allow the
ablation balloon to cover additional distance. The ablation balloon
catheter sliding range over adjustable guidewire loop 94 as
controlled by handle 83 is indicated by the arrow 85. A deflectable
sheath section is shown at 98 and with soft flexible guidewire loop
segment at 94. A sheath deflection ring is shown at 100.
[0047] The five panels of FIGS. 4A-4E show an ablation catheter
shaft 120 advanced over a guidewire 121 from inside a deflectable
sheath 122. The distal end of the guidewire at 124 is attached to a
pull line or pull wire 126 which is controlled from a control
handle (not shown). A balloon ablation device that has been
advanced over the guidewire is shown at 128. The ablation device is
shown in a deflated condition in FIG. 4A. In this condition, the
deflectable guide sheath has already penetrated into the left atria
or other chamber. In FIG. 4B, the balloon is inflated and the pull
wire 126 is shown drawing the end of the guidewire 124 toward the
sheath thereby creating a guidewire loop. In FIG. 4C, the end of
the guidewire has been pulled back inside of the sheath creating a
loop 130. FIGS. 4D and 4E show how the size of the loop 130 can be
adjusted by advancing or retracting the guidewire in the sheath.
The position of the balloon 128 over the guidewire can also be
adjusted as shown in 4D to 4E by advancement or retraction of the
ablation balloon shaft 83 (FIG. 3) over the guidewire.
[0048] FIG. 5 is a schematic diagram showing how an ablation
balloon guided by an adjustable loop guidewire in the left atrium
can create circumferential lesions. Thus, the wall of the left
atrium is represented by 140 with the left atrial appendage shown
at 142. A transeptal guide sheath 144 is shown penetrating the
septum between the right and left atria at 146. The sheath includes
an integral inflatable balloon 148 filled with saline which
protects the septum from tearing at the transeptal breach during
the procedure. The balloon catheter shaft is shown at 150 and the
guidewire with flexible segment at 152. The segmented ablation
balloon, which can be either a radio frequency or cryogenic
ablation device, is shown at 154 with thermistors and recording
electrodes shown in each balloon surface segment 155 as at 156.
Further, ring electrodes are provided on each end of the balloon,
one of which is shown at 158. The diagram further shows the
location of the outlets of the pulmonary veins, including the right
superior pulmonary vein (RSPV) 160, left superior pulmonary vein
(LSPV) 162, right inferior pulmonary vein (RIPV) 164 and left
inferior pulmonary vein (LIPV) 166.
[0049] As will be noted in conjunction with FIG. 5, the segmented
ablation balloon 154 is held tightly against the wall of the left
atrium 140 by the guidewire loop. By adjusting the size of the
guidewire loop by inserting more guidewire as needed and adjusting
the position of the ablation balloon 154 by increments along the
guidewire loop, it can be seen that a complete continuous
circumferential lesion can be created in the left atrium.
[0050] FIG. 6 is a view similar to FIG. 5 showing an alternative
system for anchoring the segmented painted ablation balloon 154 in
which, instead of the loop system, an anchoring soft portion of a
relatively stiff guidewire 170 is provided to be embedded in the
left atrial appendage 142 and the ablation balloon thereafter may
be tracked over the guidewire 170 to create the linear lesions
about the left atrium. The mitral valve is indicated at 174.
[0051] FIG. 7 is a schematic representation similar to FIG. 6
showing the segmented painted ablation balloon 154 situated in the
orifice or antrum area just beyond the orifice of the LSPV 162
where it can be used for the creation of a pulmonary vein isolation
lesion. In this manner, each of the pulmonary veins can be treated
to create a pulmonary vein isolation lesion.
[0052] FIG. 8 is a schematic diagram showing a radiofrequency or
cryogenic balloon 180 that is shown inserted in the orifice of the
LSPV 196. The balloon is guided into the PV by the transeptal
sheath 182 and the J type 4 F loop recording catheter 184. The J
loop includes an array of recording and stimulation electrodes and
thermistors as at 186 and the balloon is further provided with a
distal ring electrode 188 and a proximal ring electrode 190 for the
measurement of impedance during the ablation (specifically when
using the cryogenic balloon) procedure to define pulmonary vein
occlusion and thereafter lesion quality. The atrial wall is shown
at 192 and the pulmonary veins are indicated by 194, 196, 198 and
200. For use with the embodiment of FIG. 8, the balloon catheter
180 can be constructed in the same manner as those shown in FIGS. 6
and 7. If the catheter is a cryogenic device, an ice ball is
created during the ablation process and recording and impedance
measurements across the ice ball that is created during cryogenic
ablation allows verification of the ice ball size lesion completion
and ablation efficacy.
[0053] It will be appreciated that the J-type loop PV recording,
stimulation and impedance measurement catheter in combination with
the balloon ablation device can realize PV isolation with the use
of cryogenic balloon technology; however, success is critically
dependent on a firm contact between the balloon and the PV tissues
and a complete occlusion of the PV such that there is no blood flow
into the atria around the balloon during the ablation procedure.
This can be verified, for example, by injecting dye into the PV via
a central lumen in the balloon guidewire. If the dye appears to
collect in the vein, it may be assumed that the vein is
appropriately occluded. If the vein is not totally occluded and the
resulting lesion is not a complete circumferential lesion, i.e., if
there is a gap, or if the tissues are only stunned leading to
temporary isolation, this results in procedure failure and the need
for additional interventions.
[0054] It will be appreciated that the J-loop recording/stimulation
catheter serves several purposes: (1) it serves as a guide for a
balloon ablation catheter to place the balloon in a longitudinal
and central position with respect to the desired PV orifice; (2) it
anchors the catheter in the vein with the loop positioned in the
vein antrum just beyond the orifice; (3) pacing can be applied to
the phrenic nerve by the loop electrodes 186 during either RF or
cryogenic ablation while the diaphragmatic movement is monitored to
insure that the phrenic nerve is not ablated; (4) it allows
verification of lesion maturation by monitoring the impedance
during cryogenic ablation; and (5) it allows measurement of vein to
atria or atria to vein conduction during RF and cryogenic
ablation.
[0055] Low intensity RF energy may also be applied to the distal
balloon ring electrode 188, together with the reference electrode
190 positioned on the balloon catheter shaft just proximal to the
balloon (shown in FIG. 8) to measure the conductance across the
balloon. If the balloon solidly occludes the PV, the impedance
rises and the measurement can also be used to verify PV occlusion.
Furthermore, when the system includes a cryogenic balloon,
assessment of PV occlusion and assessment of the size of the
cryogenic ice ball can also be accomplished by measuring changes in
the impedance between the proximal and distal balloon ring
electrodes 190 and 188. Since ice is a very poor electrical
conductor, as the ice ball totally engulfs the PV, the impedance is
seen to rise dramatically and this provides a reliable indicator of
PV occlusion and cryogenic lesion maturation.
[0056] In the embodiment shown in FIG. 8, the J-loop, equipped with
several spaced ring electrodes 186 and thermistors (not shown), is
first placed in the vein, as at 196. The J shape anchors the
catheter in the vein and the loop is positioned in the vein antrum
just beyond the orifice, as shown. The balloon ablation catheter is
guided into position by advancing it over the J catheter shaft.
Baseline impedance can be measured by the delivery of low power,
high frequency electrical current (may utilize less than 1 watt,
550 KHz) to one or more of the electrodes 186 on the J-loop or to
the distal ring electrode (188) and the ring electrode 190 that is
positioned just proximal to the balloon. This impedance can also be
measured by measuring the impedance of the balloon using electrodes
188 and 190. As indicated above, after inflation of the balloon, a
second impedance measurement should show an impedance rise if the
vein is firmly occluded and no change in impedance will be detected
if only partial occlusion is achieved. Additional impedance rise is
also recorded with the cryogenic balloon ablation that indicates
ice ball formation that engulfs the distal electrode.
[0057] The J catheter is preferably a pre-shaped 3-4 F catheter
that is inserted into the central channel of the ablation balloon.
The J portion of the catheter is inserted into a PV with the
circular portion of the catheter equipped with ring
recording/stimulation electrodes and thermistors that encircle the
antrum of the PV. The balloon catheter is advanced over the J
catheter using the J catheter as a guidewire. The balloon is
positioned to occlude the PV while the circular portion of the
catheter encircles the balloon just distal to the balloon contact
with the PV. Low power RF energy is applied to the preselected ring
electrodes placed either on the balloon shaft or the loop portion
of the J catheter for the measurements of impedance pre and post
balloon inflation and during the ablation especially with the
cryogenic balloon embodiment.
[0058] In operation, it should be appreciated that the delivery and
tissue contact procedure for both the RF and cryogenic balloon
embodiments can be the same. The highly conductive elements and
thermistors are circumferentially distributed around the outer
surface of both the RF and outer cryogenic balloons.
[0059] FIG. 9 includes schematic representations of an alternate
embodiment of the invention in the form of a multi-ablation
electrode-type catheter system for the creation of linear lesions
that is particularly designed to create linear lesions in the
tissue located between the pulmonary veins to accomplish isolation
of these tissues, an aspect which is also deemed very important to
the success of atrial fibrillation ablation. As shown in FIG. 9, a
flexible multi-electrode ablation catheter 300 containing an array
of spaced wire wound ablation electrodes 302 is extended from a
support sheath arrangement having two members 304 and 306, which
make up a support and torquable ablation catheter support sheath.
The catheter support sheath members 304 and 306 are extended from a
main transeptal guide sheath 308. Support sheath extensions are
shown at 310 and 312 and a locking device for locking the support
sheath to a deflectable transeptal guide sheath is shown at 314. A
deflection control handle is shown at 316 and an ablation catheter
connector is shown at 318, which supplies power to the electrodes
302 via connecting line 320. While other sizes can be used, the
flexible multi-electrode ablation catheter 300 is normally 4 F and
the wire wound electrodes 302 may be 5 mm long with 2 mm gaps in
between. Each of the support and torquable catheter guide sheaths
304 and 306 are pre-shaped to allow them to be maneuvered into a
pulmonary vein.
[0060] The placement of the guide sheaths 304 and 306 in pairs of
pulmonary veins is illustrated by the schematic drawings of FIGS.
10-13 in which the left atrial wall is represented by 330 and the
pulmonary vein includes RSPV 332, LSPV 334, RIPV 336 and LIPV 338.
The left atrial appendage is shown at 340 and the mitral valve at
342 (FIG. 10).
[0061] In this manner, FIG. 10 illustrates how a linear lesion is
placed between the right superior pulmonary vein 332 and the left
superior pulmonary vein 334. Note that the stabilizing and
supporting guide sheaths 304 and 306 provide penetration into the
orifices and antrums of the pulmonary veins and also provide
support for the array of catheter electrodes. Thermistors as at 344
can be positioned between the ablation/recording electrodes 302. In
the same manner, FIG. 11 shows ablation between the LSPV 334 and
LIPV 338. FIG. 12 shows ablation between the LIPV 338 and the RIPV
336. Finally, FIG. 13 illustrates ablation between the RSPV 332 and
the RIPV 336.
[0062] Thus, the flexible multi electrode ablation catheter 300 is
placed in a pair of stiffer guide sheaths 304 and 306 which, in
turn, are placed in a deflectable guide sheath 308, which is a
transeptal device. In operation, once the main sheath is advanced
into the desired chamber, the ablation catheter 300 and the two
support guide sheaths 304 and 306 are advanced out of the main
sheath into the chamber. Each of the supporting guide sheaths 304
and 306 are pre-shaped to allow them to be maneuvered into a
pulmonary vein. The supporting sheaths 304 and 306 can be advanced
individually by pushing and/or rotating the proximal portion in and
out of the main deflectable sheath 308. The position of the
supporting sheaths can be locked in place by releasing or securing
the locking mechanism 314 on the deflection control handle 316.
Good ablation catheter contact with the desired tissues is ensured
once the support sheaths are forced into the desired pulmonary
veins while keeping the ablation catheter taut across the tissues,
as illustrated in the figures. Another embodiment is seen
schematically in FIGS. 14 and 15. That embodiment is in essence a
simplified version of the embodiment shown in FIGS. 9-13 in which a
multi-electrode catheter 400 with wire wound ablation and
measurement electrodes 402 and intermediate thermistors 404 is
inserted directly into the main deflectable guiding sheath 406 to
form a loop at the end of the sheath. An extension rod, shown at
408, is used to modify the shape of the loop. A handle and
deflection control is shown at 410 with locking device 412 and
multi-electrode and thermistor connector is shown at 414. An
extension rod control is shown at 416 and a draw string with
stopper at 418. A septum protection balloon is shown at 420. In
FIG. 15, the left atrial wall is shown at 422 with the left atrial
appendage at 424. The pulmonary vein orifices are shown at 426,
428, 430 and 432 and the mitral valve at 434. The draw string or
pull wire at 418 can be used to minimize the size of the main
guiding sheath 406 by enabling retraction of the ablation catheter
400 inside the orifice of the main deflectable guiding sheath prior
to deployment. It should be noted that the insulated extension
flexible rod 408 provides further support and stability to the
catheter loop and improves tissue contact. Catheter mobility and
position can be accomplished as desired by deflecting the main
sheath in rotation, ablation catheter torque extension and
expansion of the catheter loop, extension or retraction of the
insulated rod 408.
[0063] FIG. 16 is a schematic representation of a monitoring and
control system for an RF ablation system in accordance with the
invention. The system includes a catheter system 500 with a balloon
catheter 502 mounted on catheter shaft 504 which rides over
guidewire 506. A sheath is shown at 508. The balloon catheter
includes a plurality of thermistor and recording electrodes 510 and
RF ablation electrodes 512. The catheter further includes
mechanical manipulation controls and liquid inflation and
circulation controls represented by block 514.
[0064] An RF energy power generator system including input and
output data processing and an electrogram RF filter is shown at 520
with connection to RF control system 522. The RF generator is
connected to a visual output or screen display device as shown in
block 524 and a recording system is shown connected at 526.
[0065] The RF power generator is programmed to control and modulate
RF power to each ablation electrode in any of the multi-electrode
RF catheter systems as each electrode is separately connected and
separately controllable. The delivery of power is controlled so
that only the electrodes that are in firm contact with the targeted
tissue are energized and the desired power is carefully controlled
to avoid overheating blood or ablated tissue. Overheating of
ablated tissue may cause char formation and can lead to stroke.
Thus, each independent power source is modulated based on sensed
temperature and the first derivative of the temperature change
(dT/dt) which describes the rate of temperature rise. Real time
local electrical activity is closely monitored. This includes
recording of electrogram amplitude, changes in maximal frequency of
the local electrogram and impedance changes.
[0066] Once RF power is turned on, the power generator system
modulates the RF power in accordance with a pre-programmed
procedure, which may be as follows: [0067] 1. After contact and
tissue viability is defined within acceptable parameters, e.g.,
[0068] a. Local electrogram >1 mV, [0069] b. Maximum electrogram
frequency >8 Hz, [0070] c. Impedance <180 ohms. [0071]
Starting with a low power setting, power is increased to control
electrode temperature rate of change at a preset level such as
5.degree. C./second=dT/dt; [0072] 2. Achieve maximum preset
temperature such as 65.degree. C.; [0073] 3. Terminate power input
if impedance increases above a preset level (150-180 ohms, for
example) or if the local electrogram decreases by 50% or more from
baseline levels, and/or in conjunction with the electrogram
amplitude, if the local electrogram frequency decreases by, for
example, 30% from the baseline value. [0074] 4. Certain values in
items 3 can be overridden if advisable during the procedure. [0075]
5. Reduce power to minimum when successful ablation is indicated by
electrogram data and impedance measurements.
[0076] The RF power generator system is designed to receive data
related to all of the necessary parameters from the ablation
electrodes and thermistors, including local electrogram amplitude
and percent change, maximum electrogram frequency temperature, rate
of change of temperature (dT/dt) impedance, output power and
application time.
[0077] After data received indicates that local tissue has been
successfully ablated and power has been terminated, the catheter
can be repositioned for the next local tissue ablation.
[0078] From the above description and drawings, it will be apparent
that there is a unique nature associated with the present invention
that resides in the functionality of the embodiments to accomplish
precise and excellent ablation, particularly with regard to the
control of atrial fibrillation in the human heart. It will be
appreciated, however, that the devices and techniques can be
applied in any area of the heart. Thus, it can be applied to the
right and left ventricle as well as for mapping and ablation of
ventricular tachycardia. With respect to atrial fibrillation, it
has been found that the catheter systems in accordance with the
present invention have vastly improved the contact and catheter
tractability leading to more predictable lesions while minimizing
the amount of tissue that is ablated.
[0079] 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.
* * * * *