WO2024115107A1

WO2024115107A1 - Temperature-based pressure measurement in cryoballoon ablation catheters

Info

Publication number: WO2024115107A1
Application number: PCT/EP2023/081882
Authority: WO
Inventors: Alessandro Fisher
Original assignee: Medtronic Ireland Manufacturing Unlimited Company
Priority date: 2022-11-30
Filing date: 2023-11-15
Publication date: 2024-06-06

Abstract

A cryoballoon ablation catheter. One example includes an expandable element, an inflow lumen for providing a fluid to the expandable element, and a temperature sensor for sensing a temperature of the fluid in the expandable element, wherein the catheter includes neither a pressure sensor nor a pressure tube for monitoring a pressure within the expandable element.

Description

TEMPERATURE-BASED PRESSURE MEASUREMENT IN CRYOBALLOON ABLATION CATHETERS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/385,516, filed November 30, 2022, and U.S. Provisional Patent Application Serial No. 63/385,521, filed November 30, 2022, the entire contents of each are incorporated herein by reference.

BACKGROUND

[0002] Cryotherapy is a useful treatment modality for many types of medical procedures. In some cases, it is desirable to administer cryotherapy from within a patient's body, such as from within a body lumen. Internal administration of cryotherapy can be advantageous, for example, in at least some neuromodulation procedures. These procedures can include percutaneously introducing a cryotherapeutic element into a patient and then advancing a catheter shaft carrying the cryotherapeutic element along an intravascular path to a suitable treatment location. Once positioned at the treatment location, the cryotherapeutic element can be cooled to modulate nearby nerves. The cooling caused by the cryotherapeutic element, for example, can reduce undesirable local or systemic sympathetic neural activity and thereby achieve various therapeutic benefits.

SUMMARY

[0003] Some vascular denervation catheter devices use cryoablation techniques. During cryoablation treatment, a pressurized refrigerant is circulated through an occlusive balloon, which has been inserted into a patient’s artery. The flow of refrigerant causes the occlusive balloon to expand within the artery. Adequate balloon expansion must be achieved and maintained to hold the occlusive balloon in place during the treatment, thus ensuring complete occlusion of the artery and creation of a circumferential lesion at the treatment site. Some catheter systems monitor pressure within the occlusive balloon using a pressure monitoring tube coupled with a remote pressure sensor.

[0004] A pressure sensor coupled with a mass flow meter can be used to detect irregularities as an ablation procedure is performed. However, the addition of pressure tubes to a catheter device may impede the flow of refrigerant and increase the form factor for the device. In addition, such sensors and meters add expense and can have relatively slow response times. In some instances, redundancy is desired to improve performance of the devices. To address these issues, devices, systems, and methods are provided herein for monitoring cryoballoon fluid pressure using a temperature sensor. Because temperature and pressure are interrelated, temperature readings taken as an ablation sequence is performed can be used to detect irregularities quickly without the use and expense of pressure sensors and mass flow meters.

[0005] Embodiments and aspects described herein provide, among other things, occlusive denervation catheters with treatment elements that include a temperature sensor and do not require a pressure tube. Such catheters and their control systems enable the detection and classification of refrigerant leaks or occlusions. Using the embodiments and aspects described herein shaft occlusions, shaft leaks, and balloon leaks may be quickly detected and mitigated.

[0006] One example provides a cryoablation catheter, which includes a treatment element including an expandable element, an inflow lumen for providing a fluid to the expandable element, and a temperature sensor for sensing a temperature of the fluid in the expandable element. This example does not include a pressure sensor or a pressure tube for monitoring a pressure within the expandable element.

[0007] Another example provides a system for ablating tissue. The system includes a catheter and an electronic controller coupled to the catheter. The catheter includes a treatment element, which includes sensor for sensing a temperature of a fluid in the expandable element. The electronic controller is configured to initiate an ablation process by controlling a fluid source to provide the fluid to the treatment element. The electronic controller is configured to receive a plurality of readings from the sensor. The electronic controller is configured to determine, based on the plurality of readings, whether the temperature of the fluid in the treatment element is dropping. The electronic controller is configured to, responsive to determining that the temperature of the fluid in the treatment element is dropping, compare the plurality of readings to a cooling profile associated with the ablation process. The electronic controller is configured to, responsive to determining that the plurality of readings does not match the cooling profile, stop the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, and present an indication to an operator of the system.

[0008] A further example provides a method for operating an ablation catheter. The method includes initiating an ablation process by controlling a fluid source to provide a fluid to a treatment element of the ablation catheter. The method includes receiving a plurality of readings from a temperature sensor positioned within the treatment element. The method includes determining, based on the plurality of readings, whether the temperature of the fluid in the treatment element is dropping. The method includes, responsive to determining that the temperature of the fluid in the treatment element is dropping, comparing the plurality of readings to a cooling profile associated with the ablation process. The method includes, responsive to determining that the plurality of readings does not match the cooling profile, stopping the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, and presenting an indication to an operator of the ablation catheter.

[0009] Further disclosed herein is a cryoballoon ablation catheter that includes an expandable element, an inflow lumen for providing a fluid to the expandable element, and a temperature sensor for sensing a temperature of the fluid in the expandable element, wherein the catheter includes neither a pressure sensor nor a pressure tube for monitoring a pressure within the expandable element.

[0010] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments, examples, aspects, and features of concepts that include the claimed subject matter and explain various principles and advantages of those embodiments, examples, aspects, and features.

[0012] FIG. 1 is schematic illustration of a vascular denervation system according to some examples.

[0013] FIG. 2 illustrates an inflow lumen of the vascular denervation system of FIG. 1 according to some examples.

[0014] FIG. 3 illustrates a treatment element of the vascular denervation system of FIG. 1 according to some examples. [0015] FIG. 4 is a block diagram that illustrates an electronic controller of the system of FIG. 1 according to some examples.

[0016] FIG. 5 is a chart illustrating aspects of the operation of the system of FIG. 1 according to some examples.

[0017] FIG. 6 is a chart illustrating a computational fluid dynamics model for a treatment element of the vascular denervation system of FIG. 1 according to some examples.

[0018] FIG. 7 is a flow chart illustrating a method for operating the system of FIG. 1 according to some examples.

[0019] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of examples, aspects, and features illustrated.

[0020] In some instances, the apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the of various embodiments, examples, aspects, and features so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

DETAILED DESCRIPTION

[0021] For ease of description, some or all of the example systems presented herein are illustrated with a single exemplar of each of its component parts. Some examples may not describe or illustrate all components of the systems. Other example embodiments may include more or fewer of each of the illustrated components, may combine some components, or may include additional or alternative components.

[0022] It should be understood that although certain figures presented herein illustrate hardware and software located within particular devices, these depictions are for illustrative purposes only. In some embodiments, the illustrated components may be combined or divided into separate software, firmware, and/or hardware. For example, instead of being located within and performed by a single electronic processor, logic and processing may be distributed among multiple electronic processors. Regardless of how they are combined or divided, hardware and software components may be located on the same computing device or may be distributed among different computing devices connected by one or more networks or other suitable communication links.

[0023] FIG. 1 illustrates an example system 10 that is suitable for performing cryoballoon ablation, including renal artery denervation. The system 10 is for delivering thermally conductive fluid (refrigerant) to an area of target tissue, such as, for example, an area of tissue within the hepatic artery to cause denervation. The system 10 may generally include a catheter, such as a catheter 12, and a console 14 for operating, monitoring, and regulating the operation of the catheter 12 (for example, with the electronic controller 33), and a fluid source 16 for delivering fluid (for example, a refrigerant) to the catheter 12.

[0024] The catheter 12 is a highly flexible treatment device that is suitable for passage through the vasculature. The catheter 12 may be adapted for use with the fluid source 16 to denervate portions of an artery. In the example illustrated, the catheter 12 has an elongate body 18 having a proximal portion 20 and a distal portion 22. The distal portion 22 includes a treatment element 23. The proximal portion 20 of the catheter 12 is mated to a handle 24 that can include an element such as a lever or knob for manipulating the elongate body 18 and the treatment element 23. The distal portion 22 may also include an aperture (not shown) sized to allow for the passage of a guidewire 31 through the elongate body 18 and through the aperture.

[0025] The elongate body 18 is sized and configured to be passable through a patient’s vasculature and/or positionable proximate to the area of target tissue, and may include one or more lumens (for example, the inflow lumen 27 and the inner member/guidewire lumen 28) disposed within the elongate body 18 that provide mechanical, electrical, and/or fluid communication between the proximal portion 20 of the elongate body 18 and the distal portion 22 of the elongate body 18. In some aspects, the elongate body 18 includes a guidewire lumen through which a sensing device, mapping device, the guidewire 31, or other system components may be located and extended from the distal portion 22 of the catheter 12. The elongate body 18 may be rigid and/or flexible to facilitate the navigation of the catheter 12 within a patient’s body. In one aspect, the distal portion 22 of the elongate body 18 is flexible to allow for more desirable positioning proximate to an area of target tissue (e.g., positioning within a renal artery, a hepatic artery, the splanchnic bed, the pulmonary artery, the aortic root, the carotid body, and the like). To access an area of target tissue, the catheter 12 may be inserted through one or more blood vessels, such as, for example, one or more brachial arteries, one or more radial arteries, one or more femoral arteries, or other points of access including venous access (e.g., for greater splanchnic nerve denervation or through the jugular vein for carotid body ablation).

[0026] The treatment element 23 includes an expandable element 26 (for example, an occlusive balloon), through which fluid from the fluid source 16 is circulated. An inflow lumen 27 is in fluid communication with the fluid source 16 in the console 14 to supply a refrigerant fluid (e.g., nitrous oxide (N₂O), nitrogen, carbon dioxide, argon, or another suitable refrigerant) in response to console commands and other control input. In some aspects, a vacuum pump 34 (electronically coupled to and controlled by the electronic controller 33) in the console 14 creates a low pressure environment in an outflow lumen (not shown) so that the fluid is drawn into the outflow lumen, away from the expandable element 26, towards the proximal portion 20 of the elongate body 18, and into the fluid recovery reservoir 40 within the console 14. In some aspects, the electronic controller 33 controls a valve or valves (not shown) to open and close to control the flow of a refrigerant fluid (e.g., stored under pressure in the fluid source 16) toward the treatment element 23. When expanded, the expandable element 26 is sized and configured to fit within an area of the artery under treatment such that the thermal element 30 is substantially centered within the artery.

[0027] The inflow lumen 27 includes a plurality of throttle holes 29, which are disposed near the terminus of the inflow lumen 27. The throttle holes are configured to maximize circumferential ablation and heat transfer by producing a desired pressure drop. In some instances, the lumen 27 has between three and nine throttle holes, each sized between 0.0015 and 0.0025” in diameter. As illustrated in FIG. 2, the throttle holes may be distributed around the circumference of the inflow lumen 27. Returning to FIG. 1, the inflow lumen 27, in some aspects, is positioned such that it terminates proximate to the distal end of the expandable element 26 to improve thermal transfer from the target tissue to the refrigerant.

[0028] The treatment element 23 also includes a temperature sensor 30 (e.g., a thermocouple, a thermistor, a fiber optic temperature sensor, or another suitable means of sensing temperature), which is positioned within the expandable element 26 to measure the temperature of the fluid within the expandable element 26. The temperature sensor 30 is coupled to the electronic controller 33 of the console 14. In some aspects, the temperature sensor 30 is directly coupled to the electronic controller 33, which generates temperature values from voltages or other signals read from or provided by the temperature sensor 30. In other aspects, the temperature sensor 30 is indirectly coupled to the electronic controller 33 through, for example, intervening circuitry in the catheter 12 and the electronic controller 33 receives temperature values from the intervening circuitry. As illustrated in chart 500 of FIG. 5, a pressure within the expandable element 26 can be determined from the temperature of the fluid within the expandable element 26. However, because heat transfers into the expandable element 26 from the surrounding tissue, the temperature sensor 30 should be positioned at a location within the expandable element 26 that enables the sensor to sense the minimum temperature of the fluid in the expandable element 26. In some aspects, the temperature sensor 30 is affixed (e.g., with a glue) to the guidewire lumen 28 and positioned near the throttle holes 29 of the inflow lumen 27. In some aspects, the temperature sensor 30 is placed an a location within the expandable element 26 determined through the use of a computational fluid dynamics model (e.g., the model 600 illustrated in FIG. 6). In some aspects, the temperature sensor 30 is placed an a location within the expandable element 26 determined through the use or experimentation.

[0029] In some aspects, the temperature sensor 30 is positioned at a suitable distance from the throttle holes 29 of the inflow lumen 27 to prevent the temperature sensor 30 from coming into contact with the plume of unevaporated refrigerant being pumped into the expandable element 26. In some aspects, the temperature sensor 30 is positioned in a chamber to isolate it from the refrigerant plume 32. For example, as illustrated in FIG. 6, the temperature sensor 30 is positioned in a chamber 602, into which fluid flows through an opening 604. In the example illustrated in FIG. 6, the distal end of the inflow lumen 27 is fixed in epoxy 606, which partially defines the chamber 602. In the illustrated example, the chamber 602 acts as the outflow for the fluid.

[0030] In some aspects, the console 14 includes one or more pressure sensors 42 to continuously record the instantaneous pressure values within the expandable element 26. The pressure sensors 42 may then generate and transmit a pressure signal to the electronic controller 33 of the console 14. As illustrated in FIG. 3, in some aspects, treatment element 23 also includes a pressure monitoring tube 302 (enclosed in the elongate body 18) in fluid communication with the pressure sensor 42 (housed in the console 14) and the expandable element 26.

[0031] In the illustrated example, the control unit 14 includes an electronic controller 33 (described more particularly with respect to FIG. 4) programmed or programmable to execute the automated or semi-automated operation and performance of the features, sequences, calculations, or procedures described herein. The electronic controller 33 is communicatively coupled to the various components of the catheter 12, including the vacuum pump 34, one or move valves as described herein, and the temperature sensor 30. The control unit 14 may include one or more user input devices, controllers, speakers, and/or electronic displays 35 (each coupled to and controllable by the electronic controller 33) for collecting and conveying information from and to the user.

[0032] In some aspects, the treatment element 23 includes ultrasonic transducers (not shown) to record the reflected, refracted, scattered, and/or attenuated ultrasound signals from the target tissue. As the transducers record the ultrasound signals, they begin to vibrate and the mechanical vibrations are converted into electric current signals that are transmitted back to the control unit 14 or an external ultrasound control unit 37 which processes the signals to generate a sonogram or ultrasonogram showing the patient’s tissue, organs, and/or a location of the catheter 12 within the patient’s body. The sonogram may then be relayed to a clinician via a display 35 of the control unit 14, or via a display 39 of the external ultrasound control unit 37, to assist the physician in positioning the catheter 12 near or proximate to a desired treatment location.

[0033] FIG. 4 illustrates an example embodiment of the electronic controller 33, which includes an electronic processor 205 (for example, a microprocessor, application specific integrated circuit, etc.), a memory 210, and an input/output interface 215. The memory 210 may be made up of one or more non-transitory computer-readable media and includes at least a program storage area and a data storage area. The program storage area and the data storage area can include combinations of several types of memory, such as read-only memory (“ROM”), random access memory (“RAM”) (for example, dynamic RAM (“DRAM”), synchronous DRAM (“SDRAM”), etc.), electrically erasable programmable read-only memory (“EEPROM”), flash memory, or other suitable memory devices. The electronic processor 205 is coupled to the memory 210 and the input/output interface 215. The electronic processor 205 sends and receives information (for example, from the memory 210 and/or the input/output interface 215) and processes the information by executing one or more software instructions or modules, capable of being stored in the memory 210, or another non-transitory computer readable medium. The software can include firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. The electronic processor 205 is configured to retrieve from the memory 210 and execute, among other things, software for performing methods as described herein.

[0034] The input/output interface 215 transmits and receives information from devices external to the electronic controller 33 (for example, over one or more wired and/or wireless connections), for example, components of the system 10. The input/output interface 215 receives input (for example, from a human machine interface of the console 14), provides system output or a combination of both. The input/output interface 215 may also include other input and output mechanisms, which for brevity are not described herein and which may be implemented in hardware, software, or a combination of both.

[0035] It should be understood that although FIG. 4 illustrates only a single electronic processor 205, memory 210, and input/output interface 215, alternative embodiments of the electronic controller 33 may include multiple processors, memory modules, and/or input/output interfaces. It should also be noted that the system 10 may include other electronic controllers, each including similar components as, and configured similarly to, the electronic controller 33. In some embodiments, the electronic controller 33 is implemented partially or entirely on a semiconductor (for example, a field-programmable gate array [“FPGA”] semiconductor) chip. Similarly, the various modules and controllers described herein may be implemented as individual controllers, as illustrated, or as components of a single controller. In some aspects, a combination of approaches may be used.

[0036] In some instances, the treatment element 23 is equipped with a temperature sensor, but is not equipped with a pressure tube, pressure sensor, or other means of sensing a pressure of the fluid in the expandable element 26. In such instances, the lack of a pressure sensing means reduces space to provide a more compact catheter. In other instances, the treatment element 23 may be equipped with both a temperature sensor and pressure sensing means. In such instances, the presence of a temperature sensor and a pressure sensing means provides redundancy for of assessing pressure within the expandable element 26.

[0037] FIG. 7 illustrates an example method 700 for operating the system of FIG. 1 to monitor pressure within the expandable element 26, through the use of temperature readings, to detect failures during ablation procedures. Although the method 700 is described in conjunction with the system 10 as described herein, the method 700 could be used with other systems and devices. In addition, the method 700 may be modified or performed differently than the example provided.

[0038] As an example, the method 700 is described as being performed by the electronic controller 33. However, it should be understood that, in some examples, portions of the method 700 may be performed by other components, including for example, the catheter 12.

[0039] At block 702, the electronic controller 33 initiates an ablation process, for example, by controlling the fluid source 16 to provide a volume of the fluid to the expandable element 26 via the inflow lumen 27. In one aspect, the electronic controller 33 controls the vacuum pump 34 or a similar pump to provide a volume of refrigerant to the expandable element 26. In another aspect, the electronic controller 33 controls a valve or valves to provide a volume of refrigerant to the expandable element 26 from a pressurized source.

[0040] At block 704, the electronic controller 33 receives a plurality of readings from the temperature sensor 30 and determines, based on the plurality of readings, whether the temperature of the fluid in the expandable element is dropping. For example, the electronic controller 33 may periodically monitor a voltage from the temperature sensor 30 to generate temperature values and determine whether a rolling average of the temperature values is trending downward. In another example, the electronic controller 33 may generate a curve from the temperature values and determine that the temperature of the fluid is dropping when the curve develops a negative slope. In another example, the electronic controller 33 may receive and process temperature values, e.g., derived from voltages or other readings received from the temperature sensor 30 by intervening circuitry.

[0041] At block 706, when the electronic controller 33 determines (at block 704) that the temperature of the fluid is not dropping, it stops the ablation process. For example, the electronic controller 33 may control the fluid source to stop providing the volume of the fluid to the expandable element (e.g., stopping or reducing the fluid flow). In some aspects, the electronic controller 33 will also present an indication to an operator of the system, for example, indicating that the operator of the system should inspect the catheter. In one example, the electronic controller 33 displays on the electronic display 35 a message to the operator stating “CHECK CONSOLE SETUP AND EXAMINE FOR LEAKS. IF SETUP IS OK, REPLACE CATHETER.” In another example, the electronic controller 33 presents the indication by playing an audio message, activating a warning light, sounding an audio alarm, activating a haptic feedback motor, or performing some combination of the forgoing.

[0042] At block 706, responsive to determining (at block 704) that the temperature of the fluid in the expandable element is dropping, the electronic controller 33 compares the plurality of readings to a cooling profile associated with the ablation process. For example, the electronic controller 33 may generate a curve from the temperature values derived from the readings and compare the curve to a temperature curve for the type of ablation being performed. Where the two curves to not sufficiently match (e.g., are outside a predetermined matching threshold), the electronic controller 33 determines that the plurality of readings does not match the cooling profile and stops the ablation process by controlling the fluid source to stop providing the volume of the fluid to the expandable element. In some instances, the electronic controller 33 also presents a relevant alert.

[0043] For example, the electronic controller 33 may determine (at block 706) that the temperature of the fluid in the expandable element is dropping too slowly. In response, the electronic controller 33, at block 708, stops the ablation process and presents an indication indicating that the treatment element may be leaking (e.g., by displaying a message stating “CATHETER LIKELY LEAKING - REPLACE CATHETER”).

[0044] In another example, the electronic controller 33 may determine (at block 706) that the temperature of the fluid in the expandable element is dropping too rapidly. In response, the electronic controller 33, at block 710, stops the ablation process and presents an indication indicating that the treatment element may be occluded (e.g., by displaying a message stating “CATHETER LIKELY OCCLUDED - REPLACE CATHETER”).

[0045] When (at block 706) the electronic controller 33 determines that the plurality of readings matches the cooling profile, it, at block 712, determines a steady state temperature for the fluid and determines whether the steady state temperature for the fluid exceeds a threshold steady state temperature of the cooling profile. When the steady state temperature does not exceed the threshold, the electronic controller 33, at block 714, continues the ablation process.

[0046] When (at block 714) the stead state temperature exceeds the threshold steady state temperature, the electronic controller 33, at block 716, stops the ablation process and presents an indication indicating that the treatment element may be occluded (e.g., by displaying a message stating “CATHETER LIKELY OCCLUDED - REPLACE CATHETER”).

[0047] In some aspects, the electronic controller 33 performs the method 700 in conjunction with a pressure controlled approach. For example, the electronic controller 33 may receive pressure readings from a pressure sensor and control the fluid source based on the pressure readings, while taking a plurality of readings indicative of temperature, e.g., according to the method 700, to validate the pressure readings.

[0048] The application may be further understood with reference to the following numbered examples:

[0049] Example 1 A: A system for ablating tissue, the system comprising: a catheter including a treatment element, the treatment element including a sensor for sensing a temperature of a fluid in the treatment element; and an electronic controller coupled to the catheter and configured to: initiate an ablation process by controlling a fluid source to provide the fluid to the treatment element; receive a plurality of readings from the sensor; determine, based on the plurality of readings, whether the temperature of the fluid in the treatment element is dropping; responsive to determining that the temperature of the fluid in the treatment element is dropping, compare the plurality of readings to a cooling profile associated with the ablation process; and responsive to determining that the plurality of readings does not match the cooling profile: stop the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, and present an indication to an operator of the system.

[0050] Example 2A: The system of example 1 A, wherein the electronic controller is further configured to: responsive to determining that the temperature of the fluid in the treatment element is not dropping: stop the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, wherein presenting the indication to the operator of the system includes presenting an indication that an operator of the system should inspect the catheter.

[0051] Example 3A: The system of example 1 A or 2A, wherein the electronic controller is further configured to: determine that the plurality of readings does not match the cooling profile by determining that the temperature of the fluid in the treatment element is dropping too slowly; wherein presenting the indication to the operator of the system includes presenting an indication that the treatment element may be leaking.

[0052] Example 4A: The system of any one of examples 1 A to 3 A, wherein the electronic controller is further configured to: determine that the plurality of readings does not match the cooling profile by determining that the temperature of the fluid in the treatment element is dropping too rapidly; wherein presenting the indication to the operator of the system includes presenting an indication that the treatment element may be occluded.

[0053] Example 5A: The system of any one of examples 1 A to 4A, wherein the electronic controller is further configured to: responsive to determining that the plurality of readings matches the cooling profile: determine a steady state temperature for the fluid, and responsive to determining that the steady state temperature for the fluid exceeds a threshold steady state temperature of the cooling profile: stop the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, wherein presenting the indication to the operator of the system includes presenting an indication that the treatment element may be occluded. [0054] Example 6A: The system of any one of examples 1 A to 5A, wherein each of the plurality of readings is indicative of a minimum temperature of the fluid in the treatment element.

[0055] Example 7A: The system of any one of examples 1 A to 6A, wherein the catheter further includes: a pressure sensor for sensing a pressure in the expandable element; and wherein the electronic controller is coupled to the pressure sensor and further configured to, during the ablation process: receive a pressure reading from the pressure sensor; and control the fluid source based on the pressure reading and the plurality of readings.

[0056] Example 8A: The system of any one of claims 1 A to 7A, wherein the fluid is a refrigerant.

[0057] Example 9A: The system of example 8A, wherein the refrigerant is one selected from the group consisting of nitrous oxide, carbon dioxide, nitrogen, and argon.

[0058] Example 10A: The system of any one of examples 1 A to 9A, wherein controlling the fluid source includes controlling at least one selected from the group consisting of a pump and a valve.

[0059] Example 11 A: A method for operating an ablation catheter, the method comprising: initiating an ablation process by controlling a fluid source to provide a fluid to a treatment element of the ablation catheter; receiving a plurality of readings from a temperature sensor positioned within the treatment element; determining, based on the plurality of readings, whether the temperature of the fluid in the treatment element is dropping; responsive to determining that the temperature of the fluid in the treatment element is dropping, comparing the plurality of readings to a cooling profile associated with the ablation process; and responsive to determining that the plurality of readings does not match the cooling profile: stopping the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, and presenting an indication to an operator of the ablation catheter.

[0060] Example 12A: The method of example 11 A, further comprising: responsive to determining that the temperature of the fluid in the treatment element is not dropping: stopping the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, wherein presenting the indication to the operator of the system includes presenting an indication that an operator of the system should inspect the catheter.

[0061] Example 13A: The method of example 11 A or 12A, wherein: determining that the plurality of readings does not match the cooling profile includes determining that the temperature of the fluid in the treatment element is dropping too slowly; and presenting the indication to the operator of the system includes presenting an indication that the treatment element may be leaking.

[0062] Example 14A: The method of any one of examples 11 A to 13A, wherein: determining that the plurality of readings does not match the cooling profile includes determining that the temperature of the fluid in the treatment element is dropping too rapidly; and presenting the indication to the operator of the system includes presenting an indication that the treatment element may be occluded.

[0063] Example 15 A: The method of any one of examples 11 A to 14A, further comprising: responsive to determining that the plurality of readings matches the cooling profile: determining a steady state temperature for the fluid, and responsive to determining that the steady state temperature for the fluid exceeds a threshold steady state temperature of the cooling profile: stopping the ablation process by controlling the fluid source to stop providing the fluid to the treatment element, wherein presenting the indication to the operator of the system includes presenting an indication that the treatment element may be occluded.

[0064] Example 16A: The method of any one of examples 11 A to 15A, wherein receiving a plurality of readings from a temperature sensor positioned within the treatment element includes receiving a plurality of readings, each being indicative of a minimum temperature of the fluid in the treatment element.

[0065] Example 17A: The method of any one of examples 11 A to 16A, further comprising: during the ablation process, receiving a pressure reading from a pressure sensor for sensing a pressure in the treatment element; and controlling the fluid source based on the pressure reading and the plurality of readings.

[0066] Example 18A: The method of any one of examples 11 A to 17A, wherein controlling the fluid source to provide the fluid to the treatment element includes controlling at least one selected from the group consisting of a pump and a valve to provide a refrigerant to the treatment element.

[0067] Example 19A: The method of example 18 A, wherein the refrigerant is one selected from the group consisting of nitrous oxide, carbon dioxide, nitrogen, and argon.

[0068] Example IB: A catheter for ablating tissue, the catheter comprising: an expandable element, an inflow lumen for providing a fluid to the expandable element, and a temperature sensor for sensing a temperature of the fluid in the expandable element, wherein the catheter includes neither a pressure sensor nor a pressure tube for monitoring a pressure within the expandable element.

[0069] Example 2B: The catheter of example IB, wherein the temperature sensor is one selected from the group consisting of a thermocouple, a thermistor, and a fiber optic temperature sensor.

[0070] Example 3B: The catheter of example IB or 2B, wherein the temperature sensor is positioned at a location within the expandable element that enables the temperature sensor to sense the minimum temperature of the fluid in the expandable element.

[0071] Example 4B: The system of example IB or 2B, wherein the temperature sensor is positioned within a chamber to isolate the temperature sensor from a plume of the fluid.

[0072] Example 5B: The catheter of any one of examples IB to 4B, further comprising: a guidewire lumen; wherein the temperature sensor is affixed to the guidewire lumen.

[0073] Example 6B: The catheter of any one of examples IB to 5B, wherein the inflow lumen includes a plurality of throttle holes for delivering the volume of the fluid to the expandable element.

[0074] Example 7B: The catheter of any one of examples IB to 6B, wherein the inflow lumen terminates proximate to the distal end of the expandable element.

[0075] Example 8B: The catheter of any one of examples IB to 7B, further comprising: an outflow lumen for removing fluid from the expandable element.

[0076] Example 9B: The catheter of any one of examples IB to 8B, wherein the fluid is a refrigerant.

[0077] Example 10B: The catheter of example 9B, wherein the refrigerant is one selected from the group consisting of nitrous oxide, carbon dioxide, nitrogen, and argon.

[0078] Example 1 IB: The catheter of any one of examples 1 to 10B, further comprising: a treatment element; wherein the treatment element includes the expandable element, the inflow lumen, and the temperature sensor.

[0079] Example 12B: A system comprising the catheter of any one of examples IB to 1 IB and a console for operating the catheter, the console comprising: an electronic controller configured to: receiving a plurality of readings from the temperature sensor, and controlling the delivery of the fluid to the expandable element based on the plurality of readings. [0080] In the foregoing specification, specific examples have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.

[0081] Moreover, in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has,” “having,” “includes,” “including,” “contains,” “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a,” “has . . . a,” “includes . . . a,” or “contains . . .a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially,” “essentially,” “approximately,” “about,” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way but may also be configured in ways that are not listed.

[0082] It will be appreciated that some examples may be comprised of one or more generic or specialized processors (or “processing devices”) such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used.

[0083] Moreover, an embodiment can be implemented as a computer-readable storage medium having computer readable code stored thereon for programming a computer (e.g., comprising a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage mediums include, but are not limited to, a hard disk, a CD- ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.

[0084] It should be understood that although certain drawings illustrate hardware and software located within particular devices, these depictions are for illustrative purposes only. In some examples, the illustrated components may be combined or divided into separate software, firmware and/or hardware. For example, instead of being located within and performed by a single electronic processor, logic and processing may be distributed among multiple electronic processors. Regardless of how they are combined or divided, hardware and software components may be located on the same computing device or may be distributed among multiple different devices.

[0085] Various features and advantages of the embodiments presented herein are set forth in the following claims.

[0086] Further disclosed herein is the subject-matter of the following clauses:

1. A catheter for ablating tissue, the catheter comprising: an expandable element; an inflow lumen for providing a fluid to the expandable element; and a temperature sensor for sensing a temperature of the fluid in the expandable element, wherein the catheter includes neither a pressure sensor nor a pressure tube for monitoring a pressure within the expandable element. 2. The catheter of clause 1, wherein the temperature sensor is one selected from the group consisting of a thermocouple, a thermistor, and a fiber optic temperature sensor.

3. The catheter of clause 1 or 2, wherein the temperature sensor is positioned at a location within the expandable element that enables the temperature sensor to sense the minimum temperature of the fluid in the expandable element.

4. The system of clause 1 or 2, wherein the temperature sensor is positioned within a chamber to isolate the temperature sensor from a plume of the fluid.

5. The catheter of any one of clauses 1 to 4, further comprising: a guidewire lumen; wherein the temperature sensor is affixed to the guidewire lumen.

6. The catheter of any one of clauses 1 to 5, wherein the inflow lumen includes a plurality of throttle holes for delivering the volume of the fluid to the expandable element.

7. The catheter of any one of clauses 1 to 6, wherein the inflow lumen terminates proximate to the distal end of the expandable element.

8. The catheter of any one of clauses 1 to 7, further comprising: an outflow lumen for removing fluid from the expandable element.

9. The catheter of any one of clauses 1 to 8, wherein the fluid is a refrigerant.

10. The catheter of clause 9, wherein the refrigerant is one selected from the group consisting of nitrous oxide, carbon dioxide, nitrogen, and argon.

11. The catheter of any one of clauses 1 to 10, further comprising: a treatment element, wherein the treatment element includes the expandable element, the inflow lumen, and the temperature sensor.

12. A system comprising: the catheter of any one of clauses 1 to 11; and a console configured to operate the catheter, the console comprising: an electronic controller configured to: receive a plurality of readings from the temperature sensor, and control the delivery of the fluid to the expandable element based on the plurality of readings.

Claims

1. A catheter for ablating tissue, the catheter comprising: an expandable element; an inflow lumen for providing a fluid to the expandable element; and a temperature sensor for sensing a temperature of the fluid in the expandable element, wherein the catheter includes neither a pressure sensor nor a pressure tube for monitoring a pressure within the expandable element.

2. The catheter of claim 1, wherein the temperature sensor is one selected from the group consisting of a thermocouple, a thermistor, and a fiber optic temperature sensor.

3. The catheter of claim 1 or 2, wherein the temperature sensor is positioned at a location within the expandable element that enables the temperature sensor to sense the minimum temperature of the fluid in the expandable element.

4. The system of claim 1 or 2, wherein the temperature sensor is positioned within a chamber to isolate the temperature sensor from a plume of the fluid.

5. The catheter of any one of claims 1 to 4, further comprising: a guidewire lumen; wherein the temperature sensor is affixed to the guidewire lumen.

6. The catheter of any one of claims 1 to 5, wherein the inflow lumen includes a plurality of throttle holes for delivering the volume of the fluid to the expandable element.

7. The catheter of any one of claims 1 to 6, wherein the inflow lumen terminates proximate to the distal end of the expandable element.

8. The catheter of any one of claims 1 to 7, further comprising: an outflow lumen for removing fluid from the expandable element.

9. The catheter of any one of claims 1 to 8, wherein the fluid is a refrigerant.

10. The catheter of claim 9, wherein the refrigerant is one selected from the group consisting of nitrous oxide, carbon dioxide, nitrogen, and argon.

11. The catheter of any one of claims 1 to 10, further comprising: a treatment element, wherein the treatment element includes the expandable element, the inflow lumen, and the temperature sensor.

12. A system comprising: the catheter of any one of claims 1 to 11; and a console configured to operate the catheter, the console comprising: an electronic controller configured to: receive a plurality of readings from the temperature sensor, and control the delivery of the fluid to the expandable element based on the plurality of readings.