Contact indication of balloon catheter ablation electrode via balloon surface temperature measurement

Abstract

The invention is entitled "Contact indication of balloon catheter ablation electrodes via balloon surface temperature measurements." The invention discloses a method comprising positioning an inflatable balloon coupled to a distal end of a catheter at a target location within an organ of a patient, the inflatable balloon comprising a plurality of electrodes and one or more sensors proximate each electrode, wherein the one or more sensors are each configured to measure a blood property; inflating the inflatable balloon at the target location. Fluid flows through a lumen of the catheter and into blood proximate each electrode. A dependence of the blood property on time is measured via the one or more sensors proximate each electrode. Using a processor, whether each electrode is in physical contact with tissue is determined based on the measured dependence of the blood property. An indication of whether each electrode is in physical contact with tissue is output to a user.

Description

Technical Field

[0001] This invention generally relates to medical probes, and more specifically to cardiac radiofrequency (RF) balloon ablation catheters. Background Technology

[0002] Medical probes equipped with biophysical sensors at their distal ends have been previously disclosed in patent literature. For example, U.S. Patent Application Publication 2014 / 0276709 describes a medical system including an ablation catheter. The ablation catheter includes an elongated shaft having a proximal end, a distal end, and a lumen disposed between the proximal and distal ends. The ablation catheter also includes an inflatable element in fluid communication with the lumen, a first temperature sensor operable to measure a first temperature, and a second temperature sensor operable to measure a second temperature. The first and second temperature sensors are longitudinally separated from each other by at least a portion of the inflatable element. A temperature difference is maintained between the first temperature measured at the first temperature sensor and the second temperature measured at the second temperature sensor using a continuous flow of inflatable fluid. Maintaining the temperature difference facilitates closure assessment. Specifically, when fully closed, the first temperature at the first temperature sensor will be several degrees Celsius lower than the second temperature at the second temperature sensor.

[0003] For example, U.S. Patent Application Publication 2016 / 0157914 describes a method, system, and apparatus for predicting the quality of ablation lesions. Specifically, the quality of the ablation lesion can be predicted based on an assessment of pulmonary vein closure using saline infusion and an assessment of temperature measurements recorded by a thermocouple located distal to a cryoprecipitate balloon of the treatment device. The quality of closure can be assessed based on the time taken for the temperature recorded by the thermocouple to increase from about 32°C to about 38°C, the rate of temperature change over a predetermined time period, and / or the rate of dissipation of saline containing a given volume of contrast medium within the pulmonary vein. For example, the quality of closure can be assessed as good, average, or poor. This assessment can be quickly and easily communicated to the operator.

[0004] U.S. Patent Application Publication 2008 / 0097422 describes a system and method for deploying an electrode structure in contact with a tissue region. The electrode structure carries sensors at known locations on the electrode structure to monitor operating conditions. The system and method provide an interface that generates an idealized image and an indicator image of the electrode structure to represent the operating conditions monitored in spatial locations corresponding to the sensor locations on the electrode structure. The interface displays a view image including the idealized image and the indicator image. The system and method cause the electrode structure to apply energy to heat the tissue region while displaying the view image on a display screen. In one embodiment, each electrode carries one or more temperature sensors. Each electrode may carry two temperature sensors, one for sensing temperature conditions near the exposed distal end of the electrode and the other for sensing temperature conditions in an electrically insulated location outside the electrode. Summary of the Invention

[0005] Embodiments of the present invention provide a method comprising positioning an inflatable balloon coupled to the distal end of a catheter at a target location within a patient's organ. The inflatable balloon includes a plurality of electrodes and one or more sensors proximal to each electrode, wherein each of the sensors is configured to measure blood properties. The inflatable balloon inflates at the target location. Fluid flows through the lumen of the catheter and into the blood near each electrode. The time dependence of the blood properties is measured via the one or more sensors proximal to each electrode. Using a processor, it is determined whether each electrode is in physical contact with tissue based on the measured dependence of the blood properties. An indication of whether each electrode is in physical contact with tissue is output to a user.

[0006] In some embodiments, fluid flow includes continuously applying flushing fluid via a balloon. In other embodiments, fluid flow includes injecting fluid.

[0007] In some implementations, each of the one or more sensors includes a temperature sensor, and the blood properties include temperature.

[0008] In one embodiment, each of the one or more sensors includes a first electrode and a second electrode, and the blood characteristics include bipolar impedance. In another embodiment, each of the one or more sensors includes a first electrode and a second electrode, the second electrode being a reference electrode, and the blood characteristics include unipolar impedance.

[0009] In some implementations, each of the one or more sensors includes a pH sensor, and the blood properties include pH.

[0010] In some implementations, determining whether each electrode is in physical contact with tissue includes establishing a baseline for blood properties and comparing that baseline with the measured time dependence.

[0011] In one implementation, establishing a baseline involves using one or more sensors with electrodes that are intentionally manipulated to avoid contact with tissue.

[0012] In some embodiments, determining whether each electrode is in physical contact with the tissue includes estimating the rate at which blood properties return to their initial values ​​after fluid flow is stopped. In other embodiments, determining whether each electrode is in physical contact with the tissue includes estimating the time period from the start of fluid flow until the blood properties reach their steady-state values.

[0013] In one implementation, determining whether each electrode is in physical contact with tissue includes determining the extreme values ​​of blood properties reached near each electrode.

[0014] In another implementation, the dependence of the measurement characteristic includes comparing the characteristic with a calibrated characteristic.

[0015] In some implementations, the fluid includes a coolant.

[0016] In some implementations, the fluid includes brine.

[0017] In one embodiment, fluid flow includes injecting fluid through a lumen for injecting contrast fluid. In another embodiment, fluid flow includes injecting fluid through a flushing port in the balloon.

[0018] In some implementations, the cavity includes either the pulmonary veins of the heart or the left atrium of the heart.

[0019] According to embodiments of the invention, this document further provides a system comprising a catheter and a processor. The catheter includes a shaft for insertion at a target location within a patient's organ, the shaft having an inner lumen for allowing fluid flow to induce transient blood properties. The catheter also includes an inflatable balloon coupled to a distal end of the shaft, the inflatable balloon including a plurality of electrodes and one or more sensors proximate to each electrode, wherein each of the one or more sensors is configured to measure blood properties. The processor is configured to determine whether each electrode is in physical contact with tissue based on the dependence of the measured blood properties, and to output an indication to the user of whether each electrode is in physical contact with tissue.

[0020] The invention will be more fully understood through the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, wherein: Attached Figure Description

[0021] Figure 1A schematic diagram of a catheter-based positioning-tracking and balloon ablation system according to an embodiment of the present invention;

[0022] Figure 2 It is deployed in the region of the pulmonary vein (PV) and its orifice according to an embodiment of the present invention. Figure 1 A schematic side view of the distal end of the balloon catheter;

[0023] Figure 3 This illustrates an embodiment of the invention as a function of time. Figure 1 A graph showing the sensed temperature near the two ablation electrodes of the balloon catheter;

[0024] Figure 4 This is an illustrative illustration of an embodiment of the invention. Figure 1 A flowchart illustrating the method for contacting the ablation electrode in a balloon catheter. And...

[0025] Figure 5 This illustrates an embodiment of the invention as a function of time (including during RF ablation). Figure 1 A graph showing the sensed temperature near the ablation electrode of the balloon catheter. Detailed Implementation

[0026] Overview

[0027] For effective ablation using medical probes such as intracardiac balloon catheters, it is crucial that the ablation electrodes positioned above the balloon make good physical contact with the tissue before ablation. For example, in pulmonary vein (PV) isolation, all ablation electrodes should make good contact around the periphery of the PV ostium. However, verifying good contact with tissue, such as the ostium, by examining the closure of distal vessels (e.g., PV vessels) is cumbersome and typically relies on another method, such as fluoroscopy. Furthermore, if incomplete closure is present, it is difficult to use fluoroscopy to identify which specific ablation electrode lacks good tissue contact.

[0028] The embodiments of the invention described herein provide improved techniques for monitoring, for example, whether the ablation electrodes of a cardiac balloon are in contact with tissue and the degree of good contact just before ablation. The disclosed techniques provide systems and methods for estimating the degree of physical contact of the electrodes and measuring transient changes in the resulting blood properties using local flushing and / or injection of fluids having properties different from blood. Based on the sensed transient changes in blood properties, the processor can determine whether each ablation electrode of the balloon ablation catheter is in contact with tissue.

[0029] In some embodiments, a system is provided comprising a catheter including (i) a shaft for insertion into a lumen of a patient's organ at a target location within the organ, the shaft having an inner lumen configured to allow fluid flow to induce transient blood properties, and (ii) an inflatable balloon coupled to a distal end of the shaft, the inflatable balloon including a plurality of electrodes and one or more sensors proximate to each electrode, wherein each of the one or more sensors is configured to measure blood properties. The system also includes a processor configured to (a) determine, based on a dependence of the measured blood properties, whether each electrode is in physical contact with tissue, and (b) output an indication to a user of whether each electrode is in physical contact with tissue.

[0030] In one implementation, the processor determines whether each electrode is in physical contact with the tissue by establishing a baseline of blood properties and comparing that baseline with the measured time dependence.

[0031] In some cases, establishing a baseline involves using one or more sensors with electrodes that are intentionally manipulated to avoid contact with tissue.

[0032] In some embodiments, the processor determines whether each electrode is in physical contact with the tissue by estimating the rate at which blood properties return to their initial values ​​after fluid injection has ceased. In another embodiment, determining whether each electrode is in physical contact with the tissue includes determining the extreme values ​​of blood properties reached near each electrode.

[0033] In some implementations, each of the one or more sensors includes a temperature sensor, and the blood properties include temperature. A fluid that has a cooling effect on the blood, such as a saline solution, is pumped from the balloon through a flushing port and into the bloodstream. One or more temperature sensors disposed on each ablation electrode in the balloon acquire (the temperature of each electrode) over time after fluid release. The temperature characteristic map (temperature change over time) varies depending on whether the electrode is in good contact with the tissue.

[0034] In another embodiment, in order to achieve an enhanced transient effect on temperature, a cooling fluid, such as a cryogenic saline or glucose solution, can be injected through a separate lumen, such as a lumen for injecting contrast fluid.

[0035] In one implementation, measuring the time dependence of blood properties near each electrode involves comparing that property to a calibrated property. For example, a coolant with a given lower temperature is prepared compared to the in vivo blood temperature. After coolant injection, the resulting peak difference between the temperature of the tissue and the electrode in contact with the blood can be calibrated relative to the original coolant temperature. Based on this calibration, the field physician obtains a prediction of the expected peak difference in electrode temperature, which indicates that physical contact between the electrode and the tissue has indeed been achieved.

[0036] With necessary modifications, other physical effects can be generated, sensed, and analyzed using the disclosed techniques. For example, the pumped or injected fluid can locally affect blood pH, and a pH sensor on each ablation electrode in the balloon collects (for each electrode) different pH over time after fluid release. Similarly, the pumped or injected fluid can locally affect blood CO2 content, and a CO2 sensor on each ablation electrode in the balloon collects (for each electrode) different PCO2 over time after fluid release. PCO2 is defined herein as the partial pressure of carbon dioxide in blood. The peak and / or steady-state differences of each of the above physical effects are also correlated with the differences between these values ​​in (i) blood, (ii) in vivo, and (iii) in extracorporeal fluids, and these relationships can be calibrated. A prediction of the expected peak difference can be made, and this prediction is used to indicate the level of physical contact.

[0037] In one embodiment, a sensor made of two electrodes measures changes in bipolar impedance as a function of transient blood characteristics, which have different effects on inter-electrode impedance via blood and via heart tissue. In another embodiment, the sensor uses one electrode and a reference electrode to measure unipolar impedance as a function of transient blood characteristics. For example, the impedance of blood can change in the presence of pumped saline, and utilizing two different sensors to measure both impedance and temperature profiles can further improve the technique.

[0038] In some implementations, based on the disclosed technology, the processor is further configured to provide contact values ​​on a scale between contactless and full contact, and to visually indicate the contact value of each electrode of the balloon.

[0039] By providing tissue contact indication for each electrode along the entire periphery of the ablation balloon, the disclosed technique improves the accuracy of balloon catheter placement against tissue, thereby enhancing the effectiveness of balloon ablation. Furthermore, the disclosed technique eliminates the need for X-ray fluoroscopy imaging using contrast materials, making it safer for both patients and physicians.

[0040] Therefore, the disclosed technology provides a complete and safe real-time assessment of the contact between a single balloon electrode and tissue, which can improve the outcomes of cardiac balloon ablation treatments such as pulmonary vein (PV) isolation as a treatment for arrhythmias.

[0041] System Description

[0042] Figure 1 This is a schematic illustration of a catheter-based positioning-tracking and balloon ablation system 20 according to an embodiment of the present invention. System 20 includes a catheter 21, as shown in illustration 25, with an RF ablation inflatable balloon 40 adapted at a distal end 22a of the catheter's shaft 22. As further shown in illustration 25, the distal end 22a includes a magnetic sensor 39, which is housed within the distal end 22a, just proximal to the inflatable balloon 40.

[0043] The proximal end of catheter 21 is connected to console 24. Console 24 includes a flushing module 46 that allows system 20 to control flushing provided to the distal end 22a. In the embodiments described herein, catheter 21 can be used for any suitable therapeutic and / or diagnostic purpose, such as electrosensing and / or radiofrequency (RF) ablation of tissue in the heart 26. To perform its functions, system 20 also includes a temperature sensing module 49, the function of which is described below.

[0044] The physician 30 inserts the distal end 22a of the shaft 22 through the sheath 23 into the heart 26 of the patient 28 lying on the worktable 29. The physician 30 manipulates the shaft 22 using a manipulator 32 located near the proximal end of the catheter to navigate the distal end of the shaft 22 to a target location in the heart 26 and / or to deflect the distal end of the shaft relative to the sheath 23. During insertion of the distal end 22a, the balloon 40 is held in a collapsed configuration by the sheath 23. By containing the balloon 40 in a collapsed configuration, the sheath 23 also serves to minimize vascular trauma along the route to the target location.

[0045] During navigation of the distal end 22a within the heart 26, the console 24 receives signals from a magnetic sensor 39 in response to a magnetic field from an external field generator 36, for example, to measure the position of the ablation balloon 40 within the heart, and optionally, displays the tracked position on a display 27. The magnetic field generator 36 is positioned at a known location outside the patient 28, for example, below the patient's workbench 29. The console 24 also includes drive circuitry 34 configured to drive the magnetic field generator 36.

[0046] In one implementation, a position signal received from position sensor 39 indicates the position of ablation balloon 40 in the coordinate system of position tracking and ablation system 20. Position sensing methods using external magnetic fields are implemented in various medical applications, such as the CARTO system manufactured by Biosense Webster Inc. (Irvine, California). TM The system is implemented and described in detail in U.S. Patents 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, as well as PCT Patent Publication WO96 / 05768 and U.S. Patent Application Publications 2002 / 0065455A1, 2003 / 0120150A1, and 2004 / 0068178A1, the disclosures of which are all incorporated herein by reference.

[0047] Once the distal end 22a of shaft 22 has reached the target position, the physician 30 retracts the sheath 23 and inflates the balloon 40, and further manipulates shaft 22 to bring the balloon 40 into contact with the opening of the pulmonary vein, as... Figure 2 As shown in the figure, the balloon 40 includes a plurality of RF ablation electrodes 44 disposed above the periphery of the balloon 40. Each electrode structure includes one or more temperature sensors, such as... Figure 2 As shown.

[0048] The console 24 includes: a processor 41, typically a general-purpose computer with a suitable front end; and interface circuitry 38 for receiving signals from catheter 21, for applying RF energy therapy via catheter 21 to the left atrium of heart 26, and for controlling other components of the system 20. The processor 41 typically includes software in the memory 48 of the system 20, which is programmed to perform the functions described herein. This software can be downloaded electronically to a computer via a network, or alternatively or additionally set and / or stored on a non-transitory tangible medium (such as magnetic storage, optical storage, or electronic storage). Specifically, the processor 41 operates as disclosed herein, including... Figure 4 A dedicated algorithm is used to enable processor 41 to perform the steps disclosed in this invention, as further described below.

[0049] Contact indication of balloon catheter ablation electrode via balloon surface temperature measurement

[0050] Figure 2 It is deployed in the region of the pulmonary vein (PV) 13 and its orifice 11 according to an embodiment of the present invention. Figure 1A schematic side view of the balloon catheter. The balloon catheter is used for ablation of port 11 to isolate the source of the arrhythmia. Balloon 40 may be similar to the balloon used in the HELIOSTAR multi-electrode RF balloon ablation catheter (manufactured by Biosense Webster), which has ten large-area electrodes 50 positioned above it. During ablation foci formation, different levels of RF energy can be independently delivered to each of the ten electrodes, depending on the tissue. Furthermore, the HELIOSTAR balloon design allows isolation, such as PV isolation, to be achieved with a single application of RF energy.

[0051] like Figure 2 As shown, the distal end 22a includes an inner cavity 57 through which fluids such as saline can flow. The balloon 40 has an outer membrane with a flushing port 55 through which fluid (e.g., saline) can be drained from the interior of the balloon 40 to cool the tissue ablation site at the port 11. Although Figure 2 The fluid exiting the balloon 40 as a jet is shown. It should be understood that the fluid can exit the balloon at any desired flow rate or pressure, including the rate at which fluid leaks from the balloon.

[0052] like Figure 2 As further shown, the membrane of the balloon 40 supports and carries the ablation electrode 50, wherein each electrode structure includes one or more temperature sensors 60. The temperature measured by the sensor 60 is used to indicate the contact between the ablation electrode and the oral tissue, as described below.

[0053] Figure 2 The side view of the painting shown is chosen by way of example, where other embodiments are also possible. For example, in another embodiment, the cooling fluid may be discharged through a separate lumen (not shown) and enter PV 13, such as the lumen currently used for injecting contrast fluid.

[0054] Salt water rinsing method

[0055] Figure 3 This illustrates an embodiment of the invention as a function of time. Figure 1 The graphs 70 and 72 are plots showing the sensed temperatures near the two ablation electrodes of the balloon catheter. Graphs 70 and 72 respectively show how the temperature of the electrode 50 in contact with tissue and the electrode 50 not in contact changes over time during the disclosed contact detection procedure. It should be noted that these graphs do not include… Figure 5 The ablation effect described in the text.

[0056] Initially, before approximately t=0, the flushing is maintained at a low flow rate (e.g., 5 ml / min), which keeps the balloon 40 deflated and the electrode temperature nearly the same as the blood temperature (37°C). Then, a few seconds after t=0, a high flow rate (e.g., 35 ml / min) flushing is applied, for example, by a physician, to prepare for ablation. Flushing saline flows from the balloon 40 through the flushing port 55, as... Figure 2 As shown, the balloon 40 is fully inflated. At this point, a few seconds after time t=0, the balloon 40 is positioned at the target tissue, for example, in contact with the opening 11. It can now be assumed that the balloon 40, firmly positioned by the physician in contact with the tissue, will close PV13, except for any possible segmented leakage areas.

[0057] As shown on the left side (up to t=28s), there are significant differences in the temperature and time curves of the sensor on the closed electrode (curve 70 shows good contact) and the non-closed electrode (curve 72 shows poor contact).

[0058] Coolant injection method

[0059] At time t = 28 s (line 74), the physician injects a small, single-volume dose of cooling diluent (e.g., 20 ml of saline or glucose at low temperature) into PV 13 through a separate lumen. This injection is performed manually or automatically by a pump over short time intervals (such as a few seconds), where the exact timing depends on the volume and injection rate; this injection can also be described as a pressurized injection (pump) of the cooling fluid.

[0060] The injected cooling fluid caused a further rapid drop in blood temperature, as sensed by the two sensors, but this drop was particularly pronounced in graph 72 due to poor contact, where the temperature dropped from 34°C to about 27°C within seconds after time t = 32 s (line 76).

[0061] One mechanism that causes a rapid drop in temperature is the blood flow itself, where cooled flowing blood removes heat from the electrodes through convection. When the electrodes come into contact with tissue, a slower heat conduction mechanism through the tissue and through the balloon membrane (into the cooler saline solution inside the balloon) results in a slower and gentler temperature drop.

[0062] like Figure 3As shown, the temperatures at the two electrodes have significantly different recovery rates after t = 32 s: the temperature in the closed region remains low (∼26 °C), while the temperature in the leak region rapidly rises to 30 °C. As further seen, during the time period 65 < t < 105 seconds, cycles 75 and 77 reach different steady-state temperatures: approximately 26 °C and approximately 30 °C, respectively. The four-degree (4 °C) difference measured between the closed and non-closed electrodes can be used to detect partial closure and the location where partial closure occurs on the periphery of the balloon, which provides a way for the physician to improve the contact between the balloon catheter and the ostium 11.

[0063] Finally, when the closure is released at time t = 105 s (line 78), the temperatures of all the electrodes return to the blood temperature (about 37 °C). For example, the closure condition is removed by retracting the balloon 40 after ablation is performed, leaving the ostium 11 completely reopened to the blood flow.

[0064] Figure 3 The figures in are given by way of example. The pressurized injection can be applied independently or added to the flushing, for example to accelerate cooling. When flushing is used alone, similar steady-state temperatures are achieved, approximately 26 °C and approximately 30 °C for the contacting and non-contacting electrodes, respectively.

[0065]

[0066] Figure 4 Figure 1 ​​​

[0067] In the subsequent contact monitoring step 88, the processor 41 provides a contact indication for each balloon electrode based on the obtained temperature from the monitoring.

[0068] In some embodiments, the contact indication is an audio and / or visual binary indication (contact / no contact). In other embodiments, a fuzzy measurement contact indication is used to show how much electrode contact is made (100% = full contact, 0% = no contact, 90% = almost full contact, etc.). The fuzzy indication can be implemented as different hues, different syllables, different volumes, and displayed numbers such as percentages, meters, etc. In some embodiments, the processor 41 is further configured to provide a contact index ranging between no contact and full contact, and to visually indicate the contact index for each balloon electrode.

[0069] Finally, at instruction step 90, processor 41 instructs physician 30 on the assessed physical contact.

[0070] Figure 4 The exemplary flowchart shown is chosen solely for clarity of concept. In alternative implementations, additional steps may be performed, such as injecting a contrast agent followed by fluoroscopic imaging. Contact force sensing may also be applied to monitor the quality of balloon positioning prior to ablation.

[0071] Figure 5 This illustrates an embodiment of the invention as a function of time (including during RF ablation). Figure 1 A graph showing the sensed temperature near the ablation electrode of the balloon catheter. Figure 5 It was obtained during clinical trials of the disclosed technology.

[0072] As shown in the figures, graphs 170 and 172 respectively illustrate how the temperatures of the two electrodes 50 in good contact with the tissue and the temperature of the non-contact electrode 50 change over a period of time during the disclosed contact detection process.

[0073] Initially, before t=4200 seconds, the flushing is performed at a low flow rate (e.g., 5 ml / min), which keeps the balloon 40 deflated and the electrode temperature slightly below blood temperature (i.e., at approximately 35°C). Then, a few seconds after t=4200 seconds, a high flow rate (e.g., 35 ml / min) flushing is applied by the physician to prepare for ablation.

[0074] like Figure 5As shown, immediately after t = 4200 seconds, there is a significant difference between the temperature-time curves of the sensors on the closed electrodes (good contact is shown in graph 170) and the sensors on the non-closed electrodes (poor contact is shown in graph 172). During the steady-state temperature phase, between times 4260 < t < 4310, the temperature in both closed regions remains low (∼27.5 °C), while the temperature in the leakage region rapidly rises to 31 °C. Generally, the temperature of an electrode with poor contact with tissue will be more affected by the blood temperature (i.e., about 37 °C), which causes the temperature in the leakage region to rise rapidly, as shown in graph 172.

[0075] As further seen, during RF ablation, at times 4310 < t < 4360 seconds, the electrodes found to have good contact with tissue by the disclosed technique reach clinically effective ablation temperatures in the range of 45 °C - 50 °C. On the other hand, the electrodes found to have poor contact with tissue by the disclosed technique are largely unable to be heated above 35 °C because they dissipate RF energy into the surrounding flowing blood.

[0076] In addition to measuring temperature, the impedance between each ablation electrode in the ablation electrodes and the surface electrodes attached to the patient's skin can also be measured. When the electrode contacts the tissue, corresponding to a significant temperature drop in the closed electrode (i.e., in good correspondence with graph 170), a change in impedance can be observed at the time series. On the other hand, the impedance response is expected to remain flat (as a function of time) for the non-closed electrodes because the electrodes remain immersed in blood after balloon inflation. Using these two detection methods (i.e., temperature change and impedance response) can improve the accuracy of the disclosed technique.

[0077] Although the embodiments described herein mainly relate to pulmonary vein isolation, the methods and systems described herein can also be used in other applications that require determination of closure, such as electrophysiological mapping and sympathetic denervation.

[0078] Therefore, it should be understood that the embodiments described above are cited by way of example, and the present invention is not limited to what is specifically shown and described above. Instead, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as their variations and modifications, which will occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art. The documents incorporated by reference into this patent application are considered an integral part of this application, except that if any terms defined in these incorporated documents conflict with the definitions explicitly or implicitly given in this specification, only the definitions in this specification should be considered.

Claims

1. A system comprising: The catheter includes: A shaft for insertion into a cavity of a patient's organ at a target location, the shaft having an inner cavity for allowing fluid flow to induce transient characteristics of blood; and An inflatable balloon, coupled to the distal end of the shaft, includes multiple electrodes and one or more sensors proximate to each electrode, each sensor configured to measure the blood characteristics, wherein the inflatable balloon includes an outer membrane forming a flushing orifice configured to allow fluid to drain from the interior of the balloon; and The processor is configured to, The determination of whether each electrode is in physical contact with the tissue is based on the measured dependence of the blood properties; and It outputs an indication to the user whether each electrode is in physical contact with the tissue.

2. The system of claim 1, wherein each of the one or more sensors includes a temperature sensor, and wherein the blood characteristic includes temperature.

3. The system of claim 1, wherein each of the one or more sensors comprises a first electrode and a second electrode, and wherein the blood characteristic comprises bipolar impedance.

4. The system of claim 1, wherein each of the one or more sensors includes a first electrode and a second electrode, the second electrode being a reference electrode, and wherein the blood characteristic includes unipolar impedance.

5. The system of claim 1, wherein each of the one or more sensors includes a pH sensor, and wherein the blood property includes pH.

6. The system of claim 1, wherein the processor is configured to determine whether each electrode is in physical contact with tissue by determining a baseline of the blood characteristics and comparing the baseline with a measured time dependence.

7. The system of claim 1, wherein the processor is configured to determine whether each electrode is in physical contact with tissue by estimating the rate at which the blood properties return to their initial values ​​after the flow of the fluid is stopped.

8. The system of claim 1, wherein the processor is configured to determine whether each electrode is in physical contact with tissue by estimating the time period from the start of the flow of the fluid until the blood properties reach a steady-state value.

9. The system of claim 1, wherein the processor is configured to determine whether each electrode is in physical contact with tissue by determining the extreme values ​​of the blood properties reached near each electrode.

10. The system of claim 1, wherein the processor is configured to measure the dependence of the characteristic by comparing the characteristic with a calibrated characteristic.

11. The system of claim 1, wherein the fluid comprises a coolant.

12. The system of claim 1, wherein the fluid comprises brine.

13. The system of claim 1, wherein the cavity comprises one of the pulmonary veins of the heart and the left atrium of the heart.

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