U.S. patent application number 11/767774 was filed with the patent office on 2008-01-10 for method and apparatus for inflating and deflating balloon catheters.
This patent application is currently assigned to CRYOCATH TECHNOLOGIES INC.. Invention is credited to Marwan ABBOUD, Chadi HARMOUCHE, Rachid MAHROUCHE, Teresa MIHALIK, Eric MONGER.
Application Number | 20080009925 11/767774 |
Document ID | / |
Family ID | 34991052 |
Filed Date | 2008-01-10 |
United States Patent
Application |
20080009925 |
Kind Code |
A1 |
ABBOUD; Marwan ; et
al. |
January 10, 2008 |
Method and Apparatus for Inflating and Deflating Balloon
Catheters
Abstract
A system and method for controlling the inflation, ablation, and
deflation of a balloon catheter. The system includes a balloon
catheter, a console, having a pressurized gas or liquid inflation
source, and an umbilical system to deliver pressurized coolant to
the balloon catheter. The system comprises a PID (Proportional
Integral Derivative) controller or other pressure-sensing device
that monitors the amount of pressure and volume within the balloon
catheter. During inflation, the pressure and/or volume of fluid
within the balloon is maintained at a target amount in order to
provide sufficient mechanized pressure against the desired target
region. The system limits the inflation pressure such that a safe
quantity of gas would be released should a leak occur. If the
amount falls below a certain threshold level, gas or fluid egress
is presumed and the inflation process is halted. In one embodiment,
an intermediate console is placed between the console and the
balloon catheter and coupled thereto. If a leak is detected, a shut
off valve in the intermediate station is activated and the flow of
pressurized coolant is interrupted. The balloon catheter can be
re-inflated by a separate coolant source in the intermediate
station or by a syringe. A further embodiment provides a second
balloon to envelope the first balloon and in order to provide a
safety vacuum between the two balloons.
Inventors: |
ABBOUD; Marwan;
(Pierrefonds, CA) ; MAHROUCHE; Rachid; (Anjou,
CA) ; MIHALIK; Teresa; (Montreal, CA) ;
HARMOUCHE; Chadi; (St-Laurent, CA) ; MONGER;
Eric; (Ste-Genevieve, CA) |
Correspondence
Address: |
CHRISTOPHER & WEISBERG, P.A.
200 EAST LAS OLAS BOULEVARD
SUITE 2040
FORT LAUDERDALE
FL
33301
US
|
Assignee: |
CRYOCATH TECHNOLOGIES INC.
16771 Chemin Ste-Marie
Kirkland
CA
H9H 5H3
|
Family ID: |
34991052 |
Appl. No.: |
11/767774 |
Filed: |
September 24, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10806995 |
Mar 23, 2004 |
|
|
|
11767774 |
Sep 24, 2007 |
|
|
|
Current U.S.
Class: |
607/101 ; 601/2;
606/41; 607/105 |
Current CPC
Class: |
A61B 18/02 20130101;
A61B 2018/00577 20130101; A61B 2018/00994 20130101; A61M 25/1018
20130101; A61B 2018/0212 20130101; A61M 25/10185 20131105; A61B
2018/0022 20130101; A61B 18/1492 20130101; A61B 2018/0025 20130101;
A61M 25/1011 20130101; A61B 2017/22051 20130101; A61B 2018/0262
20130101 |
Class at
Publication: |
607/101 ;
601/002; 606/041; 607/105 |
International
Class: |
A61B 18/00 20060101
A61B018/00 |
Claims
1-31. (canceled)
32. A method of inflating and deflating a catheter having an
expandable membrane, the method comprising the steps of:
controllably inflating the expandable membrane with a fixed amount
of coolant.
33. The method of claim 32, further comprising the step of
inserting the catheter into a portion of a cardiovascular
system.
34. The method of claim 33, further comprising the step of ablating
a desired tissue region with the expandable membrane.
35. The method of claim 32, further comprising the step of
controllably deflating the expandable membrane.
36. The method of claim 35, wherein the step of controllably
deflating the expandable membrane includes terminating inflation of
the expandable membrane and evacuating coolant from the expandable
membrane when the membrane reaches a predetermined temperature.
37. The method of claim 36, wherein the predetermined temperature
is greater than 0.degree. C.
38. The method of claim 32, wherein the step of inflating the
expandable membrane includes transferring a predetermined volume of
coolant at a predetermined temperature to the expandable
membrane.
39. The method of claim 38, wherein the predetermined volume is
less than approximately 20 cubic centimeters.
40. The method of claim 32, further comprising keeping the
expandable membrane inflated until a region proximate the
expandable membrane reaches a predetermined temperature range.
41. The method of claim 32, wherein inflation of the expandable
membrane is performed by a pressurized coolant source within a
first console coupled to the catheter.
42. The method of claim 41, wherein the pressurized coolant source
is a fixed volume reservoir located within the first console.
43. The method of claim 32, further comprising the step of
measuring a pressure of coolant within the expandable membrane.
44. The method of claim 43, further comprising the step of
evacuating coolant from the expandable membrane in response to the
pressure measurement.
45. The method of claim 32, further comprising the step of
measuring a volume of coolant within the expandable membrane.
46. The method of claim 45, further comprising the step of
evacuating coolant from the expandable membrane in response to the
volume measurement.
47. The method of claim 32, further comprising the step of
measuring a flow rate of coolant being transferred to the
expandable membrane.
48. The method of claim 32, further comprising the step of
substantially maintaining the inflation of the expandable membrane
by controllably introducing and evacuating coolant from the
membrane.
49. The method of claim 48, wherein the step of substantially
maintaining the inflation of the expandable membrane is performed
by a PID controller.
50. The method of claim 32, wherein the step of ablating the
desired tissue region is part of a cryoablation process.
51. The method of claim 32, wherein the step of ablating the
desired tissue region is part of a radio frequency ablation
process.
52. The method of claim 32, wherein the step of ablating the
desired tissue region is part of an ultrasound ablation
process.
53. A method for inflating and deflating a catheter having an
expandable membrane, the catheter being part of a catheter system
including a first console, a catheter, and an umbilical system
coupling the first console to the catheter, the method comprising
the steps of: evacuating air from the expandable membrane by
creating a vacuum in the expandable membrane; controllably
inflating the expandable membrane proximate a desired tissue
region, the expandable membrane being inflated with a fixed amount
of coolant in order to provide sufficient mechanical force against
the desired tissue region; and ablating the desired tissue
region.
54. The method of claim 53, further comprising the step of
inserting the catheter into a portion of a cardiovascular
system.
55. The method of claim 53, further comprising the step of
controllably deflating the expandable membrane.
56. The method of claim 55, wherein the step of controllably
deflating the expandable membrane includes terminating inflation of
the expandable membrane and evacuating coolant from the expandable
membrane when the membrane reaches a predetermined temperature.
57. The method of claim 56, wherein the predetermined temperature
is greater than 0.degree. C.
58. The method of claim 53, wherein the step of inflating the
expandable membrane includes transferring a predetermined volume of
coolant at a predetermined temperature to the expandable
membrane.
59. The method of claim 58, wherein the predetermined volume is
less than approximately 20 cubic centimeters.
60. The method of claim 53, further comprising keeping the
expandable membrane inflated until a region proximate the
expandable membrane reaches a predetermined temperature range.
61. The method of claim 53, wherein inflation of the expandable
membrane is performed by a pressurized coolant source within the
first console coupled to the catheter.
62. The method of claim 61, wherein the pressurized coolant source
is a fixed volume reservoir.
63. The method of claim 53, further comprising the step of
measuring a pressure of coolant within the expandable membrane.
64. The method of claim 63, further comprising the step of
controllably deflating the expandable membrane by evacuating
coolant from the expandable membrane in response to a pressure of
the coolant in the expandable membrane.
65. The method of claim 53, further comprising the step of
measuring a volume of coolant within the expandable membrane.
66. The method of claim 65, further comprising the step of
controllably deflating the expandable membrane by evacuating
coolant from the expandable membrane in response to a volume of
coolant within the expandable membrane.
67. The method of claim 53, further comprising the step of
measuring a flow rate of coolant being transferred to the
expandable membrane.
68. The method of claim 53, further comprising the step of
substantially maintaining the inflation of the expandable membrane
by controllably introducing and evacuating coolant from the
membrane.
69. The method of claim 68, wherein the step of substantially
maintaining the inflation of the expandable membrane is performed
by a PID controller.
70. The method of claim 53, wherein the step of ablating the
desired tissue region is part of a cryoablation process.
71. The method of claim 53, wherein the step of ablating the
desired tissue region is part of a radio frequency ablation
process.
72. The method of claim 53, wherein the step of ablating the
desired tissue region is part of an ultrasound ablation process.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] n/a
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] n/a
FIELD OF THE INVENTION
[0003] The present invention relates to a method and system for
inflating and deflating balloon catheters and more specifically to
a method and system for controlling the inflation and deflation of
balloon catheters in order to safely and effectively ablate a
tissue region.
BACKGROUND OF THE INVENTION
[0004] The use of fluids with low operating temperatures, or
cryogens, has begun to be explored in the medical and surgical
field. Of particular interest are the potential use of catheter
based devices, which employ the flow of cryogenic working fluids
therein, to selectively freeze, or "cold-treat", targeted tissues
within the body. Catheter based devices are desirable for various
medical and surgical applications in that they are relatively
non-invasive and allow for precise treatment of localized discrete
tissues that are otherwise inaccessible. Catheters may be easily
inserted and navigated through the blood vessels and arteries,
allowing non-invasive access to areas of the body with relatively
little trauma.
[0005] Catheter-based ablation systems are well known in the art. A
cryogenic device uses the energy transfer derived from
thermodynamic changes occurring in the flow of a cryogen
therethrough to create a net transfer of heat flow from the target
tissue to the device, typically achieved by cooling a portion of
the device to very low temperature through conductive and
convective heat transfer between the cryogen and target tissue. The
quality and magnitude of heat transfer is regulated by the device
configuration and control of the cryogen flow regime within the
device.
[0006] A cryogenic device uses the energy transfer derived from
thermodynamic changes occurring in the flow of a refrigerant
through the device. This energy transfer is then utilized to create
a net transfer of heat flow from the target tissue to the device,
typically achieved by cooling a portion of the device to very low
temperature through conductive and convective heat transfer between
the refrigerant and target tissue. The quality and magnitude of
heat transfer is regulated by device configuration and control of
the refrigerant flow regime within the device.
[0007] Structurally, cooling can be achieved through injection of
high pressure refrigerant through an orifice. Upon injection from
the orifice, the refrigerant undergoes two primary thermodynamic
changes: (i) expanding to low pressure and temperature through
positive Joule-Thomson throttling, and (ii) undergoing a phase
change from liquid to vapor, thereby absorbing heat of
vaporization. The resultant flow of low temperature refrigerant
through the device acts to absorb heat from the target tissue and
thereby cool the tissue to the desired temperature.
[0008] Once refrigerant is injected through an orifice, it may be
expanded inside of a closed expansion chamber, which is positioned
proximal to the target tissue. Devices with an expandable membrane,
such as a balloon, are employed as expansion chambers. In such a
device, refrigerant is supplied through a catheter tube into an
expandable balloon coupled to such catheter, wherein the
refrigerant acts to both: (i) expand the balloon near the target
tissue or the purpose of positioning the balloon, and (ii) cool the
target tissue proximal to the balloon to cold-treat adjacent
tissue.
[0009] One of the principal drawbacks to such a technique is that
during the inflation phase coolant may seep out of the balloon and
get into the bloodstream to cause significant harm. Therefore, if
the balloon develops a crack, leak, rupture, or other critical
structural integrity failure, coolant may quickly flow out of the
catheter. Another situation that may occur during the balloon
deflation phase is that the balloon may adhere to the ablated
tissue causing severe damage. This may occur after cryoablation or
cryomapping. Cryomapping is a procedure that chills conducting
target tissue to create a transient electrical effect. By
temporarily chilling the target tissue, it allows for precise site
confirmation in order to prevent inadvertent ablation. During
cryomapping, a procedure known as cryoadhesion takes place.
Cryoadhesion is a procedure that ensures the catheter tip remains
at the target cite for a seamless transition to cryoablation. In a
cryoadhesion procedure, the tip of the catheter firmly attaches to
the tissue when it freezes thereby reducing the risk of accidental
slippage of the catheter tip. Therefore, during unmonitored balloon
deflation, i.e. if the balloon deflates too quickly, the balloon,
adhering to the tissue walls, may cause severe damage.
[0010] Accordingly, it would be desirable to provide an apparatus
and method of monitoring and controlling the inflation and
deflation phases of a balloon catheter that is adaptable and
compatible with all types of balloon ablation catheters, and with
all types of ablation procedures, for example RF ablation or
cryoablation.
SUMMARY OF THE INVENTION
[0011] The present invention advantageously provides a method and
system for controllably inflating and deflating a balloon catheter.
The method and system allows for the monitoring of the inflation
and deflation phases of a catheter system in order to allow
ablation to take place, while detecting unwanted leaks of
refrigerant into the bloodstream. Balloon leaks are identified,
safety evacuation routes are provided, and a controlled deflation
mechanism is presented that prevents damage to the interior blood
vessel and tissue region, which may occur during unmonitored
deflation due to the adherence of the expandable membrane to the
interior of the vessel.
[0012] In its preferred embodiment, a method of inflating and
deflating a catheter during an ablation process, the catheter
having an expandable membrane, is provided. The method comprises
the steps of controllably inflating the expandable membrane to a
target pressure or volume, ablating a desired tissue region while
maintaining the target pressure or volume of the expandable
membrane, and controllably deflating the expandable membrane so as
not to damage desired tissue region.
[0013] In another aspect of the invention, a method for inflating
and deflating a catheter having an expandable membrane during an
ablation process is provided. The catheter is part of a catheter
system including a console, the catheter, and an umbilical system
coupling the console to the catheter. The method comprises the
steps of evacuating air from the expandable membrane by creating a
vacuum in the expandable membrane, controllably inflating the
expandable membrane proximate a desired tissue region, wherein the
expandable membrane is inflated to a target pressure or volume in
order to provide sufficient mechanical force against the desired
tissue region, ablating the desired tissue region while maintaining
the expandable membrane at the target pressure or volume, and
controllably deflating the expandable membrane such that the
desired tissue region is not damaged.
[0014] In still another aspect of the invention, an apparatus for
inflating and deflating a catheter having an expandable membrane is
provided. The apparatus comprises a console the console including
means for controlling the inflation and deflation of the expandable
membrane and for determining if the expandable membrane maintains a
target pressure or volume. The console also includes a pressurized
inflation source. The apparatus further includes a catheter, and an
umbilical system coupling the console to the expandable membrane
and delivering pressurized media to the expandable membrane.
DESCRIPTION OF THE DRAWINGS
[0015] A more complete understanding of the present inventions and
the attendant advantages and features thereof, will be more readily
understood by reference to the following detailed description when
considered in conjunction with the accompanying drawings
wherein:
[0016] FIG. 1A illustrates a first embodiment of a double balloon
catheter used in conjunction with the present invention;
[0017] FIG. 1B illustrates a catheter system used in conjunction
with the present invention;
[0018] FIG. 1C illustrates the double balloon catheter of FIG. 1A
including a flow sensor located in the handle of the catheter;
[0019] FIG. 1D illustrates the double balloon catheter of FIG. 1A
including a pressure sensor located in the handle of the
catheter;
[0020] FIGS. 2A-2E illustrate a cryoablation system incorporating
various embodiments of the apparatus and method of the present
invention;
[0021] FIG. 3 is a schematic representing the mechanical components
of the control console of the present invention;
[0022] FIG. 4 is a schematic representing the mechanical components
of the inflation circuit portion of the control console of the
present invention;
[0023] FIG. 5 is a schematic representing the mechanical components
of the deflation circuit and main vacuum path of the control
console of the present invention; and
[0024] FIG. 6 is a schematic representing the mechanical components
of the safety vacuum path of the control console of the present
invention;
[0025] FIG. 7 is a schematic representation of the embodiment
illustrated in FIG. 2A;
[0026] FIG. 8 is a schematic representation of the embodiment
illustrated in FIG. 2B;
[0027] FIG. 9 is a schematic representation of the embodiment
illustrated in FIG. 2C;
[0028] FIG. 10 is a schematic representation of the embodiment
illustrated in FIG. 2D; and
[0029] FIG. 11 is a schematic representation of the embodiment
illustrated in FIG. 2E.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The present invention is an apparatus and method for
controlling the inflation and deflation of balloon catheters. In
its preferred embodiment, the invention requires four steps to
properly control the inflation and deflation of the balloon
catheter. However, the invention allows for a variety of different
implementations in order to accomplish this task. An intermediary
control station containing a shut off valve and/or a coolant source
may be implemented to assist in properly monitoring, controlling
and maintaining the target balloon pressure and/or volume.
[0031] Referring now to the drawing figures in which like reference
designations refer to like elements, a first embodiment of a double
balloon catheter used in conjunction with the present invention is
shown in FIG. 1A. The catheter 1 includes a handle 2 having a
number of proximal connector ports 3a-3d. Port 3a may be a first
vacuum connector, having a first vacuum lumen therein, such as a 10
French lumen. Port 3b may be a coaxial connector having both a
vacuum lumen and injection therein, the vacuum lumen being a second
vacuum lumen, such as a 8 French lumen. Port 3c may be an
electrical connector. Port 3d may be a guidewire luer hub.
[0032] The handle 2 further includes a blood detection board 4 and
pressure relief valve 5. The distal end portion of the catheter 1
includes two balloons: an inner balloon 6a and an outer balloon 6b
surrounding inner balloon 6a. A soft distal tip 7 is located just
distal to the two balloons 6a and 6b. When refrigerant is injected
into the balloons along lines R as shown, vacuum applied through
the ports 3a and 3b will serve to draw any fluid within balloons 6a
and 6b along arrows V out of the balloons and the catheter.
Radiopaque marker bands M are located proximate the exit point of
the refrigerant injected into balloon 6a to aid in the positioning
and tracking of the device.
[0033] Catheter 1 includes an elongate shaft having a guidewire 8
and an inner shalt 9a and outer shaft 9b. Exemplary embodiments of
the inner shaft 9a include an 8 French shaft, while exemplary
embodiments of the outer shaft 9b include a 10 French shaft.
[0034] A typical catheter system 10 is shown in FIG. 1B. The system
includes a console 20 coupled to one end of an umbilical system 12.
The opposing end of umbilical system 12 is coupled to an energy
treatment device 22. Energy treatment device 22 may be a medical
probe, a catheter, a balloon-catheter, as well as other devices
commonly known in the art that are smooth enough to pass easily
through blood vessels and heart valves. As shown in FIG. 1A, the
energy treatment device 22 includes a balloon structure 23 that can
be a single wall or a double wall configuration, wherein the double
wall configuration places the space between balloon walls in
communication with a vacuum source.
[0035] Umbilical system 12 is comprised of three separate
umbilicals: a coaxial cable umbilical 14, an electrical umbilical
16 and a vacuum umbilical 18. An outer vacuum umbilical is used in
the case of a double balloon system; it is not necessary for a
single balloon system having only one vacuum lumen. If the user
wishes to perform an RF ablation procedure, radiofrequency energy
can be provided to electrodes on device 22 via electrical umbilical
16 to perform an RF ablation technique as is common in the art.
Electrical umbilical 16 can include an ECG box 82 to facilitate a
connection from electrodes on catheter 22 (not shown) to an ECG
monitor. Coaxial umbilical 14 includes both a cooling injection
umbilical and a vacuum umbilical that provide respective inlet and
return paths for a refrigerant or coolant used to cool a
tissue-treating end of device 22. The vacuum umbilical 18 is used
as safety conduit to allow excess coolant or gas to escape from
device 22 if the pressure within the balloon on device 22 exceeds a
predefined limit. The vacuum umbilical 18 can also be used to
capture air through a leak of the outer vacuum system where it is
outside the patient and as a lumen to ingress blood when in the
patient.
[0036] Referring once again to FIG. 1B, catheter system 10 may
include one or more sensors #, which are used to monitor the amount
of fluid or gas refrigerant injected through the umbilical system
and into the balloons. It is contemplated that the sensors may be
located in one of several locations throughout catheter system 10.
For example, sensor 11 may be located in console 20, ECG Box 82,
and/or handle 2.
[0037] Two different types of sensors are contemplated for use with
the present invention in order to monitor how much coolant is
flowing into the balloons. A flow sensor 13 shown in FIG. 1C,
measures the rate or speed of fluid or gas at a certain location.
An exemplary embodiment of flow sensor 13 is the Microbridge Mass
Air Flow Sensor by Honeywell.RTM..
[0038] Alternately, one or more sensors 11 may be a pressure sensor
15 as shown in FIG. 1D. Pressure sensor 15 in FIG. 1D is a
differential pressure sensor that can determine the amount of
pressure in the balloons by determining the difference in pressure
between points p.sub.1 and p.sub.2 and the velocity through the
restriction point d. An exemplary embodiment of pressure sensor 15
is the 26PC SMT Pressure Sensor by Honeywell.RTM..
[0039] FIGS. 2A-2E illustrate different embodiments of the catheter
system 10 of the present invention. In general, the
inflation/deflation system described herein can be used with both
single and double balloon systems. For a single balloon system, the
refrigerant is sprayed into the balloon and creates a
circumferential region of cooling through the balloon's perimeter.
The refrigerant expands and the vapor is drawn back into the
console via the return vacuum lumen. With respect to a double
balloon system, a second balloon and second vacuum lumen envelop
the single balloon system and are always maintained under vacuum
for safety reasons. The vacuum of the outer balloon will capture
refrigerant escaping through any breach of the inner balloon
system. A flow switch mounted on the outer vacuum system is used to
monitor any flow activity. Under normal operation, no fluid should
pass through the outer vacuum system. Any discussion of a "flow
switch" herein implies a double balloon system. Otherwise, all
inflation/deflation methods also apply to a single balloon
catheter.
[0040] Each embodiment includes a console 20 or console 21 an
umbilical system comprised of varying combinations of separate
umbilicals, and an ablation device 22. Each of the embodiments
shown in FIGS. 2A-2E is represented by more detailed corresponding
schematic in FIGS. 7-11, respectively, and are discussed in greater
detail below.
[0041] FIG. 2A represents a typical catheter ablation system 10.
Console 20 is coupled to a catheter 22 via an umbilical system 12,
comprised of coaxial umbilical 14, which transfers coolant from
console 20 to catheter 22 and provides a return conduit for the
coolant, electrical umbilical 16, which transfers RF energy from
console 20 to catheter 22 during an RF ablation procedure or
electrical signals during a cryoablation procedure, and safety
vacuum umbilical 18, to allow for quick evacuation of coolant if
needed.
[0042] Coolant is provided by a coolant source within console 20.
Coolant, typically N.sub.2O, passes through the internal piping of
console 20 before being transferred to catheter 22 via the coaxial
umbilical 14. At the distal end of the umbilical, inside catheter
22, the coolant is released inside the catheter tip cavity, which
is under vacuum. Both the phase change from liquid to gas and the
sudden expansion of the coolant are endothermic reactions, causing
a temperature differential which results in the catheter tip or
balloon freezing. The coolant vapor is then returned through the
vacuum path via umbilical 14 and into console 20, where it is
evacuated through a scavenging line.
[0043] FIG. 2B represents another catheter ablation system.
However, in this embodiment, an intermediary station 74 is inserted
into the catheter system. As explained in greater detail below,
station 74 contains detection valves to detect a drop in balloon
pressure which might indicate a leak, and shut off valves to
terminate balloon inflation if necessary. Station 74 is coupled to
console 21 and catheter 22 via electrical umbilical 16 and coaxial
umbilical 14. Vacuum umbilical 18 provides an emergency evacuation
path for coolant from the catheter.
[0044] FIG. 2C represents the catheter ablation system of FIG. 2A
including a secondary coolant source 78 used to re-inflate the
expandable membrane, or balloon 23 of catheter 22 via syringe
76.
[0045] FIG. 2D illustrates two possible configurations for the
ablation system. In a first configuration, a secondary coolant
source includes a small tank or canister 80 located within an
intermediary station 74. In a second configuration, the secondary
coolant source includes a small tank or canister 60 located inside
the console 21. In both configurations, the secondary coolant
source is independent from the source of cooling provided by other
components within the console 21 (the primary coolant source), and
it does not require the same type of refrigerant that is provided
by the primary coolant source.
[0046] FIG. 2E illustrates a configuration where the secondary
cooling source and the primary cooling source are unified and thus
share the same source of refrigerant.
[0047] FIG. 3 refers to a schematic representing the console 20
portrayed in FIGS. 2A and 2C. The schematic shown is designed
specially for balloon catheters and contains a series of two and
three-way solenoid valves and regulators that assist in monitoring
the pressure of the balloon catheter 23, which may drop quickly if
a leak of fluid occurs. Device 22 (shown in FIGS. 2A-2E) is a
catheter with an expandable membrane 23 at its distal end. Console
20 is represented by the schematic in FIG. 3 that shows the layout
of the internal mechanical components of console 20.
[0048] In an exemplary embodiment, the system is operated in four
phases. The first phase is the evacuation flushing phase. When the
catheter 22 is inserted inside the patient it is first necessary to
evacuate air molecules from within the catheter, air contained
inside the umbilical connecting the catheter 22 to the console 20,
as well as from the catheter shaft itself. Although it is not
theoretically possible to evacuate 100% of the air molecules, by
minimizing the amount of air within the umbilical and catheter
shaft, the catheter is prepared for inflation and then ablation,
while minimizing the dangers associated with fluid egress.
[0049] During the evacuation/flushing phase, a 3-way solenoid valve
24 is open toward vacuum pump 26, which ensures that there is a
vacuum in catheter 22. The 3-way solenoid valve 24 can be replaced
by a PID-driven proportional valve. In either configuration, the
2-way solenoid 28 that supports high pressure is closed to prevent
any high-pressure gas from reservoir 30 from entering the inner
vacuum system/balloon catheter during the refilling process.
Reservoir 30 could be a tube or reservoir containing enough fluid
volume to fill the umbilical tubes and catheter 22 to a predefined
pressure. If the pressure within reservoir 30 exceeds a
predetermined pressure setpoint, a check valve 32 will open to
evacuate the exceeded amount of coolant such as, for example,
nitrous oxide (N.sub.2O) in the system in order to keep a fixed
amount of nitrous oxide in reservoir 30. During this phase,
reservoir 30 is filled with N.sub.2O received from N.sub.2O source
60. The N.sub.2O is received from a high pressure line after leaves
tank 60 and passes through a series of regulators, namely, a first
regulator 34, a second regulator 36 and then into either a third
regulator 38 or a proportional valve, that are adjusted to the
predetermined pressure. The reservoir pressure can be controlled
through a pressure regulator 38 or through a proportional valve
that would refill the tank with different pressure setpoints for
different balloon sizes or different inflation pressures. The
pressure setpoint can be programmed into a circuit, chip or other
memory device that can be located in the handle.
[0050] Refilling valve 40 opens for a period of time and fills
reservoir 30. During this phase, the 2-way solenoid valve 28
remains closed. Also, during this phase, the system is under vacuum
and provides verification for any leaks that occur.
[0051] Thus, when the the catheter is outside the patient, any
breach of the inner or outer vacuum systems will be detected by a
high baseline flow through the console flow meter. In addition, a
flow switch located in the console or in the catheter handle and
mounted on the outer vacuum system will also detect a leak of air
through a breach of the outer balloon or vacuum lumen. The flow
switch is capable of detecting volumes of gas as little as 1 cc of
vapor, and flow rates as little as 20 sccm. When the catheter is
inserted into the patient, blood ingress through either the inner
or outer vacuum lumens or both will be detected by the leak and
blood detection systems. In the case of a constant pressure
inflation with circulating flow, the balloon pressure can also be
controlled with a PID-driven proportional valve located on the
return vacuum lumen or a three-way solenoid valve in series with a
pressure switch or pressure transducer.
[0052] Referring to FIG. 4, the inflation phase of the invention
will now be discussed. Prior to positioning catheter 22 on the
ablation site, the physician must first inflate the expandable
membrane 23 inside the heart chamber and then position the balloon
23 proximate the ablation site. During this phase, the system is
under vacuum and provides verification for leaks between balloon 23
and the blood. In one embodiment, balloon 23 is inflated by
injecting fluid or gas through the umbilical under a fixed flow
pressure. This insures a defined and constant pressure inside the
balloon in order to provide a mechanical force for inflation. An
alternate way to inflate balloon 23 is to use a fixed volume of
inflation. This volume would be minimized in order to meet the
constraints related to gas egress within the blood stream (maximum
of 20 cc within 10 minutes) and meet the requirement for pressure
needed to inflate the balloon under the harshest room
conditions.
[0053] FIG. 3 illustrates the inflation portion of the console
mechanics of FIG. 2. During the inflation phase, valve 24 is open
toward reservoir 30 and valve 28 opens, while refilling valve 40
remains closed. A fixed amount of N.sub.2O is injected to inflate
balloon 23 in order to provide sufficient mechanical force for
inflation. If a leak occurs in the balloon, the released volume of
N.sub.2O would be no more than 20 cc. The solenoid valve 44 (shown
in FIG. 33) remains open during this phase in order to ensure a
vacuum in the safety line. If a leak occurs in the inner balloon of
the catheter, the flow switch 42 (FIG. 3), detects leaks as small
as 1 cc of vapor. Flow switch 42 is active during all phases to
prevent any leak of the inner balloon system in catheter 22. The
leak and blood detection systems are still active and monitoring
any blood ingress through the outer vacuum lumen. After air has
been flushed from catheter 22 and the umbilicals connecting
catheter 22 to console 20, and balloon 23 has been inflated,
ablation may now take place.
[0054] A transition mode follows inflation but precedes ablation.
In the case of cryogenic ablation systems, a transition method is
needed to transition from closed pressurized volume to an open
circuit, which allows the flow of refrigerant to enter and exit the
catheter tip while at the same time controlling the balloon
pressure in order to keep the balloon inflated and in place. During
the transition, a pressure switch, which is adjusted to a pressure
higher than atmospheric pressure but preferably lower than 20 psia,
monitors the pressure inside the balloon catheter 22. The solenoid
valve 24 remains closed until the pressure in the catheter is
higher than the preset switch value after which the solenoid valve
opens to allow evacuation of excess refrigerant. When the pressure
falls below the reset switch value, the solenoid valve 24 closes to
keep the balloon inflated and above atmospheric pressure. During
the transition, ablation is already initiated but the pressure
switch controls the balloon pressure until refrigerant flow alone
maintains the balloon open and above atmospheric pressure. The
transition phase is considered complete when certain conditions are
met: 1) when the pressure switch commands the solenoid valve 24 to
open to vacuum and the balloon pressure remains above the present
switch value; 2) the duration of the transition phase exceeds a
predetermined time; and 3) the injection pressure reaches a
predetermined value that is adequate to generate enough flow to
maintain the balloon open. Check valve 56 is used to prevent any
abnormal rise in the pressure in the catheter tip. Another check
valve 58, shown also in FIG. 6, prevents any excessive pressure in
the safety vacuum line and in in the event the soloenoid valve 44
is blocked.
[0055] During the ablation phase, refrigerant is injected through
the umbilical system into the ablation device 22. When injection of
refrigerant is desired, N.sub.2O gas is released from source 60 and
provides high pressure liquid through a check valve 62 and a series
of pressure regulators 34 and 36. Regulators 34 and 36 are primary
and secondary pressure regulators respectively, which serve to
bring the gas pressure down to between 810 and approximately 840
psig. The liquid nitrous oxide goes through a proportional valve 64
driven by a Proportional Integral Derivative (PID) controller 66 so
that the refrigerant pressure can be varied from 0 psig to
approximately 760 psig, and through an injection solenoid valve 68
which remains open. The N.sub.2O then passes through a sub-cooler
70 with various refrigeration components such as a compressor, a
condenser, a capillary tube and a heat exchanger, which insures its
liquid state through the umbilical and into the small diameter
catheter injection tubing. During injection, solenoid vent valve 46
is closed. To detect a failure of this valve, the pressure switch
72 will close when detecting a pressure higher than 15 psig,
creating a failure signal.
[0056] During the injection phase, proportional valve 64 is used to
vary the pressure inside the injection line. This in turn will vary
the flow rate of refrigerant to the catheter tip. An increase in
the flow rate (less restriction by the regulator) lowers the
temperature of the catheter tip. Conversely, decreasing the flow
rate allows the catheter tip to be warmed by its surroundings.
[0057] FIG. 5 illustrates the deflation and main path circuitry of
the present invention. At the end of the ablation phase, the system
provides a method to insure a controlled/slow deflation in order to
prevent damaging the ablated tissue during balloon deflation. This
can be a hazard due to cryoadhesion, which may occur when the
catheter attaches to the tissue during freezing. Referring to both
FIGS. 3 and 5, during deflation, the solenoid valve 24 (FIG. 3)
remains closed until the temperature in the balloon is higher than
a predetermined temperature (usually above freezing to ensure that
surrounding tissue has thawed). When the temperature increases to
greater than the predetermined temperature, the solenoid valve 24
opens to vacuum and collapses the balloon. On both vacuum paths,
liquid sensors and insulated liquid separators 48 and 50 (FIG. 3)
are installed to prevent any liquid from entering the vacuum pump
26. If this occurs, injection and/or inflation will be stopped and
both valves 52 (FIG. 3) and 44 (FIG. 3) will switch to
atmosphere.
[0058] FIG. 6 illustrates the safety vacuum portion of the console
circuitry of FIG. 3. If a leak occurs in the catheter during
inflation or ablation, flow switch 42 can detect such a leak in
amounts as small as 1 cc of vapor. Upon detection of the leak,
inflation of the balloon catheter is stopped. Prior to inflation,
the flow switch can detect leaks of the outer balloon or guide wire
lumen when the catheter is in the air. In case of pressurization of
the safety vacuum line 1/3 psi above atmospheric, a pressure relief
valve 58 located distal to the flow switch will vent excess
pressure.
[0059] Referring now to FIG. 7, one embodiment of the present
invention is shown. The schematic in FIG. 7 illustrates the
mechanical connection of the console 20, umbilical system 12 and
catheter 22. The representation in FIG. 7 corresponds to the
embodiment shown in FIG. 2A. The internal components of console 20
are similar and correspond to those shown in greater detail in FIG.
3 explained above. In this embodiment, the balloon 23 is inflated
by receiving gas or fluid from source 60 via coaxial umbilical 14.
PID controller 66 controls the flow of pressurized fluid/gas from
console 20 through umbilical system 12 to balloon 23.
[0060] FIG. 8 shows an alternate embodiment of the invention in
which an intermediary station 74 containing all components and
circuits to operate the balloon catheter is coupled to console 10,
between the console and balloon catheter 23. Station 74 includes a
series of shut-off valves and detection switches. Detection
circuitry within station 74 can detect if the volume of gas within
balloon catheter 23 has exceeded a certain predetermined amount
(i.e. 20 cc within the catheter and the umbilical system), and
shut-off valves within station 74 are activated, preventing any
further inflation. Station 74 advantageously provides a quicker and
more effective way of detecting leakage of gas or liquid into the
blood stream. If the pressure within balloon catheter 23 drops,
this could be an indication that fluid within the balloon has
escaped. By inserting station 74 within system 10, a quicker and
more efficient way of detecting leaks and preventing unwanted
balloon inflation is provided.
[0061] FIG. 9 shows yet another embodiment of the invention. Here,
balloon inflation can be performed by a syringe 76 coupled to a
saline water source 78 or any other fluid media including gasses or
liquids. This embodiment becomes practical when manual balloon
inflation is required.
[0062] In FIG. 10, intermediary station 74 includes a second
inflation source 80. As in the embodiment depicted in FIG. 8, leak
detection circuitry and shut-off valves located in station 74
provide an efficient way of detecting leaks and quickly prohibiting
the further inflation of balloon catheter 23. Should further
inflation be required, a separate pressurized N.sub.2O source 80 is
provided in station 74, which is at a closer and more convenient
location, i.e. nearer the catheter and not in a remote location
such as console 20.
[0063] In FIG. 10, the refilling source 80 is located in the
intermediate box 74 and inflation occurs through the outer vacuum
umbilical. In FIG. 11, the refilling source is the coolant tank 60
located in the cryoablation console and inflation occurs through
the inner vacuum umbilical.
[0064] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described herein above. In addition unless mention was
made above to the contrary, it should be noted that all of the
accompanying drawings are not to scale. A variety of modifications
and variations are possible in light of the above teachings without
departing from the scope and spirit of the invention, which is
limited only by the following claims.
* * * * *