Controlling cardiac ablation using blood conductivity

Abstract

The title of the invention is "using blood conductivity to control cardiac ablation". Methods and systems provide lesion size assessment for ablation in tissue, such as cardiac tissue. The lesion size assessment is based on parameters including blood conductivity, hot spot temperature, catheter tip temperature, and current data of radio frequency (RF) ablation energy used, such as power, duration, temperature, irrigation, and contact force.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application 63 / 617,780, filed on January 5, 2024, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to tissue ablation procedures and, in particular, to controlling operating parameters of an ablation catheter that performs a tissue ablation procedure. Background Art

[0004] Some medical procedures require applying an ablation signal to tissue of a patient's organ. For example, a radiofrequency (RF) ablation signal can be applied to cardiac tissue at an ablation site for treating arrhythmias. Irreversible electroporation (IRE) / pulsed-field ablation (PFA) procedures utilize high-voltage pulses for catheter-based cardiac ablation to treat conditions such as symptomatic atrial fibrillation in a manner of local tissue necrosis. Brief Description of the Drawings

[0005] The present disclosure will be more fully understood from the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0006] Figure 1 is a schematic illustration of an example system for performing ablation according to the disclosed subject matter;

[0007] Figure 2 is a schematic diagram of a feedback loop for use with the Figure 1 system of;

[0008] Figure 3 is a flowchart of an example ablation lesion assessment algorithm according to the disclosed subject matter; and

[0009] Figure 4 is a flowchart of an example process for determining whether to exclude a patient from a procedure according to the disclosed subject matter. Detailed Description

[0010] Overview

[0011] An ablation catheter is used to create ablation lesions of dead or necrotic tissue for various procedures. As used herein, the term "ablation" refers to a radiofrequency (RF) ablation procedure or an irreversible electroporation (IRE) procedure, which is sometimes also referred to as pulsed field ablation (PFA). These procedures are designed to apply one or more high-voltage monopolar or bipolar electrical pulses to one or more electrodes in contact with the tissue to be ablated, so as to form ablation lesions at a target location in the heart (also referred to herein as the ablation site), and thereby treat cardiac arrhythmias.

[0012] For example, in an RF ablation procedure, the parameters applied to the ablation catheter and the generator include power, duration, temperature, irrigation, and contact force. These parameters are defined to obtain a desired ablation lesion, for example, an ablation lesion having a desired depth of penetration into the tissue and a desired lateral dimension (e.g., diameter).

[0013] During ablation, some energy is absorbed by the blood pool. For example, through RF ablation in the myocardium, most (about 75%-80%) of the current and electrical power generated by the generator flows to the blood and is absorbed by the blood, and only a small amount (20%-25%) enters the tissue. This absorption is thought to be due to the fact that the surface area of the end of the ablation catheter in contact with the blood is much larger than the effective surface area in contact with the tissue, and the electrical conductivity of the blood is higher than that of the tissue.

[0014] When performing an ablation procedure, the depth and lateral dimensions of the ablation lesion vary from patient to patient. To accommodate the differences between patients, the ablation lesion parameters are adjusted based on the individual patient. However, it is difficult to predict the ablation lesion parameters for each patient. A further difficulty in predicting ablation lesion size is due to the very wide range of human blood conductivity (e.g., the blood impedance experienced by the electrode varies between 100 ohms and 150 ohms), which significantly affects the amount of energy flowing to the tissue during RF ablation.

[0015] For example, generally, the higher the blood conductivity, the more RF energy (ablation current) emitted from the ablation catheter flows into the blood (where it is absorbed, rather than flowing into the tissue to be ablated).

[0016] To accurately calculate the desired ablation lesion size of the tissue of an individual patient, it is necessary to analyze the orientation of the ablation catheter with respect to the quality of contact between the end of the ablation catheter and the tissue, and the blood conductivity of the patient should be known. The blood conductivity can be determined from a blood sample prior to the ablation procedure. Based on these two factors, the ablation catheter and its generator can be controlled to produce an ablation lesion of the desired depth and lateral dimension, such that the ablation lesions are uniform among patients.

[0017] Ablation lesion size assessment is performed by an algorithm that uses parameters of current data including blood conductivity, catheter tip temperature, and RF ablation energy used, such as power, duration, temperature, irrigation, and contact force. It has been found that the use of actual measured values of blood conductivity and the measured catheter tip temperature, impedance, and contact force enables substantially more accurate ablation lesion assessment.

[0018] System Description

[0019] Reference Figure 1 , which schematically shows an exemplary catheter-based electrophysiology mapping and ablation system 10 including a plurality of catheters that are percutaneously inserted by a physician 24 through a patient's vascular system into the chambers or vascular structures of the heart 12. Generally, a delivery sheath catheter is inserted into the left atrium or right atrium near a desired location in the heart 12. Then, one or more catheters can be inserted into the delivery sheath catheter to reach a desired location in the heart 12. The plurality of catheters can include catheters dedicated to sensing intracardiac electrogram (IEGM) signals, catheters dedicated to ablation, and / or catheters dedicated to both sensing and ablation.

[0020] An exemplary catheter 14 configured for sensing IEGM is illustrated herein. The physician 24 can place the distal end 28 of the catheter 14 in contact with the heart wall for sensing a target site in the heart 12. For ablation, the physician 24 can similarly place the distal end of an ablation catheter in contact with the target site for ablating tissue. For example, the ablation catheter can include one produced by Biosense Webster Inc. (Irvine, California) or catheter.

[0021] The catheter 14 is, for example, a catheter that includes one or more electrodes 26 optionally distributed on a plurality of strips 22 at the distal end 28 and configured to sense IEGM signals. The electrodes 26 can be used to perform impedance measurements, from which blood conductivity can be derived, coordinated by the workstation 55 and the processor. For example, impedance measurement estimates can use the impedance measured at least between any two catheter electrodes 26.

[0022] The catheter 14 can additionally include one or more position sensors, such as shown by the position sensor 29, which is embedded in or near the distal end 28. The position sensor 29 is used to track the position and orientation of the distal end 28 of the catheter 14. Optionally, the position sensor 29 is a magnetic-based position sensor that includes one to three magnetic coils for sensing the three-dimensional (3D) position and orientation of the catheter 14 and the catheter tip 28.

[0023] The magnetic position sensor 29 may operate in conjunction with a positioning pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field in a predetermined workspace. The real-time position of the distal end 28 of the catheter 14 may be tracked based on the magnetic field generated by the positioning pad 25 and sensed by the magnetic-based position sensor 29. Details of the magnetic-based position sensing technology used by the catheter 14 and the magnetic position sensor 29 are described, for example, in U.S. Pat. Nos. 5,539,199, 5,443,489, 5,558,091, 6,172,499, 6,239,724, 6,332,089, 6,484,118, 6,618,612, 6,690,963, 6,788,967, and 6,892,091.

[0024] The system 10 includes one or more electrode patches 38 that are positioned to contact the skin of the patient 23 to establish a position reference for impedance-based tracking of the position pad 25 and the electrodes 26. For impedance-based tracking, current is directed to the electrodes 26 and sensed at the electrode-skin patches 38 such that the position of each electrode can be triangulated via the electrode patches 38. Details of the impedance-based position tracking technology are described, for example, in U.S. Pat. Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0025] The recorder 11 records and displays the electrogram 21 captured using the body surface ECG electrodes 18 and the intracardiac electrogram (IEGM) captured using the electrodes 26 of the catheter 14. The recorder 11 may include pacing capabilities for pacing the heart rhythm and / or may be electrically connected to an independent pacemaker.

[0026] The system 10 may include an ablation energy generator (generator) 50 that is adapted to conduct ablation energy to one or more electrodes at the distal end of a catheter configured for ablation. The ablation energy may be delivered by the catheter 14 or by an additional ablation catheter (not shown). The energy generated by the ablation energy generator 50 may include, but is not limited to, radiofrequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high voltage DC pulses that may be used to effect irreversible electroporation (IRE) / pulsed field ablation (PFA)), or combinations thereof. The energy generated (e.g., RF energy) is based on various ablation parameters, including, for example, the catheter tip 28 contact quality and the blood conductivity (σ) of the patient 23.

[0027] The Patient Interface Unit (PIU) 30 is an interface configured to establish electrical communication between a catheter, other electrophysiology equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, a plurality of catheters, positioning pads 25, body surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally, the PIU 30 additionally includes processing capabilities for performing real-time calculations of the position of the catheter and for performing ECG calculations.

[0028] The workstation 55 includes a memory, a processor unit 101a (including one or more processors such as a central processing unit (CPU)) having a memory or storage device 101b ( Figure 2 ), and appropriate operating software stored therein. The processor unit 101a and the memory 101b also include and / or provide, for example, user interface capabilities through which a user can manually or automatically input various parameters via the PIU 30, such as blood conductivity, ablation catheter tip 28 temperature (also referred to as tip temperature), hot spot temperature (the hot spot temperature is the region of the maximum or hottest temperature of the internal and ablated ablation lesion), target temperature (t), where t < 140 degrees Celsius, etc. The workstation 55 also includes a proportional-integral-derivative (PID) control module 108 ( Figure 2 ), and via its processor also runs software for an ablation lesion assessment algorithm 102 ( Figure 2 ).

[0029] For example, the workstation 55 also provides, for example, the workstation 55 also provides a variety of functions, such as one or more of the following: (1) performing three-dimensional (3D) modeling of the endocardial anatomy and rendering the model or an electroanatomical (EA) map 20 for display on a display device 27, (2) displaying an activation sequence (or other data) compiled from the recorded electrogram 21 with representative visual markers or images superimposed on the rendered electroanatomical map 20 on the display device 27, (3) displaying the real-time position and orientation of a plurality of catheters within the heart chamber, (4) displaying on the display device 27 sites of interest, such as locations where ablation energy has been applied, and (5) providing optimal ablation parameters for ablation, including catheter tip contact quality and patient blood conductivity. An article of commerce embodying the elements of the system 10 may be the CARTO TM 3 system, available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0030] Workstation 55 typically includes a general-purpose computer that is programmed in software to perform the functions described herein. The software can be downloaded electronically to the computer via a network, for example, or alternatively or additionally it can be set up and / or stored on a non-transitory tangible medium (such as magnetic memory, optical memory, or electronic memory).

[0031] Ablation Control System and Ablation Lesion Evaluation Model

[0032] Figure 2 An ablation control system 100 is schematically shown as part of a feedback control loop 100x. The ablation control system 100 is a subsystem within the main system 10 and, for example, within workstation 55. The system 100 includes components that run an ablation lesion assessment algorithm 102, such as a processor 101a and an associated storage device / memory 101b. The system 100 also includes a target temperature module 104, a mixer 106, and a proportional-integral-derivative (PID) control module (PID controller 108). The components 101a, 101b, 102, 104, 106, 108 of the system 100 communicate electrically and / or data-communicate directly or indirectly with each other, for example.

[0033] Processor 101a includes one or more processors, including a microprocessor, for controlling the operation of the ablation lesion assessment algorithm 102, the target temperature module 104, the mixer 106, and / or the PID control module 108, and for performing the functions and operations described in detail herein. Generally, processor 101a includes a general-purpose computer programmed in software to perform the functions described herein. The software can be downloaded electronically to the computer via a network, for example, or alternatively or additionally it can be set up and / or stored on a non-transitory tangible medium (such as magnetic memory, optical memory, or electronic memory). The processor is, for example, a conventional processor, such as those hardware processors used in servers, computers, and other computerized devices, including hardware processors. For example, for instance, the processor may include AMD's x86 processors (Advanced Micro ) and Intel's and processors, and any combination thereof.

[0034] Memory 101b includes any conventional storage medium. The storage device / memory 204 stores machine-executable instructions that are executed by processor 101a to perform the disclosed processes.

[0035] The ablation lesion evaluation algorithm 102 receives inputs from the RF ablation generator 50, such as the blood conductivity (6), the tip temperature of the ablation catheter 14 detected by the sensor, and the current information of the ablation energy. Based on these inputs, the ablation lesion evaluation algorithm 102 performs calculations to provide the ablation energy that will be output from the RF generator 50 to the ablation catheter (such as catheter 14) to ablate an ablation lesion of the calculated or otherwise evaluated ablation lesion size. Details of the ablation lesion evaluation algorithm 102 are given in the appendix, which is an integral part of this disclosure.

[0036] The blood conductivity (σ) of the blood pool of patient 23, in units of Siemens per meter (S / M), can be obtained by one or more of the following methods:

[0037] 1. Direct measurement - The direct measurement of blood conductivity is performed using a probe, such as the Eutech TM ECTestr11 dual-range conductivity tester from Thermo Scientific, for measuring blood samples. For example, the blood sample is at least 5 ml of venous blood sample from the femoral vein, and the sample is measured by the probe.

[0038] 2. Red blood cell (RBC) count - The number of A red blood cells is taken from the patient's blood sample, such as the blood sample described in detail above for "direct measurement". For example, the correlation described in detail in Texter, Jr. et al. Figure 1 "Relation of Conductivity in Blood-II and Cell Count", in Blood, Vol. 5, No. 11, November 1950, pp. 1036-1048, which is incorporated herein by reference in its entirety. This correlation converts the number of red blood cells into a conductivity value in units of S / m.

[0039] 3. Impedance measurement between the loop electrodes 26 of the catheter 14 - This method involves measuring the blood impedance between at least two catheter electrodes 26, and in some cases, for example, using a chart or calibration table to convert the obtained impedance measurement value into conductivity, as described in detail in co-owned U.S. Patents Nos. 10,398,348 and 11,596,324, the disclosures of which are incorporated herein by reference in their entirety.

[0040] The catheter tip temperature is measured by one or more temperature sensors located at the catheter tip. The temperature measurement is updated continuously, for example, at a rate of 20 Hz.

[0041] For the purpose of algorithm 102, the catheter penetration depth is initially estimated based on the contact force and / or impedance measurement between the ablation electrode and the patient tissue surface.

[0042] The ablation lesion evaluation algorithm 102 (also referred to as the ablation lesion size evaluation algorithm) outputs the ablation lesion size, which is projected onto the electroanatomical (EA) map 20 for viewing by the physician 24 and / or the control room operator. The output is also the hot spot temperature, which is compared to the target temperature, and the difference between them (e.g., calculated by the mixer 106) is input into the PID control module 108.

[0043] The hot spot temperature is calculated, for example, by a thermal model as described in the appendix. For example, the hot spot temperature is the maximum temperature within the ablation region of the tissue, as determined, for example, based on measurements made by the temperature sensors 110 at the tip of the ablation catheter.

[0044] The target temperature is determined by the processor 101a based on a temperature sufficient to perform ablation that does not cause steam bursts, for example, as disclosed in co-owned U.S. Patent 9,241,756, the disclosure of which is incorporated herein by reference, and is typically less than 140 degrees Celsius, for example. Alternatively, the target temperature may be stored in a database or in the PID module 108, such as in a look-up table (LUT), etc.

[0045] The PID controller 108 that receives the "error" value and based on this value is used to control the current supply of RF energy necessary to ablate the ablation point of the size determined by the ablation lesion evaluation algorithm 102. For example, the PID controller 108 calculates an output signal to control the RF ablation energy generated by the RF generator 50 and its pulses. The calculated pulses are used by the ablation catheter 14 to ablate an ablation lesion of the desired size according to the ablation lesion size calculation determined (e.g., calculated) by the algorithm 102.

[0046] Attention is now turned to Figure 3 , which shows a flowchart detailing a computer-implemented process, such as the process performed by the ablation lesion evaluation algorithm 102. Also refer to Figure 1 and Figure 2 the elements shown in. Figure 3 The processes and sub-processes are computerized processes performed by the system 10 and the subsystem 100. The above processes and sub-processes are performed continuously, automatically, and, for example, in real time.

[0047] The ablation lesion evaluation starts at the start block 302. The processor has been programmed with physical parameters and material properties, such as the thermal and electrical properties of the material at the tip 28 of the ablation catheter 14. The processor is also programmed to sample from six different probes (e.g., sensors 29) at the tip 28 of the catheter 14 at regular intervals (e.g., at a rate of 20 times per second).

[0048] Moving to block 304, the ablation catheter 14 positioning begins with the physician 24 inserting the ablation catheter 14 into the tissue to be ablated. The physician 24 can use any suitable method to select the ablation site within the tissue. For example, in cardiac ablation, the physician 24 can select the site of ablation of the arrhythmia, as is known in the art.

[0049] After the probe is positioned, the process moves to block 306, where the processor 101a estimates the initial penetration depth of the distal end 28 of the catheter 14 into the tissue using, for example, one or more of a) impedance, contact force, and / or temperature measurements and b) blood conductivity measurements. For example, the impedance is determined by impedance measurements from the electrodes 26, for example, between two or more electrodes on the catheter 14. For example, a tissue proximity indication (TPI) algorithm can be used to measure the impedance between the electrodes 26 to estimate the penetration depth of the catheter 14 / catheter distal end 28, such as the TPI algorithm described in detail in U.S. Patent No. 10,398,348.

[0050] The contact force is determined by measurements on a force gauge (not shown) near the catheter distal end 28, which measures the contact force on the tissue, for example, at a resolution of 1 gram. For example, the temperature measurement can be performed by penetrating the distal end 28 into the tissue (equal to the tissue being covered by the distal surface), for example, as disclosed in "Chamber-Specific Radiofrequency Lesion Dimension Estimation Using Novel Catheter-Based Tissue Interface Temperature Sensing" by J. Kosuth et al., JACC: Clinical Electrophysiology, Vol. 3, No. 10, pp. 1092-1102 (2017), the disclosure of which is incorporated herein by reference.

[0051] The process moves to block 308, where the RF generator 50 is activated to apply an ablation current to the tissue. The RF power level generated by the RF generator 50 is controlled by the current level applied to the generator 50. The energy generated by the RF generator 50 is delivered via the ablation catheter 14 to the tissue at the ablation site. Typically, when RF energy is applied to the tissue, the ablation catheter 14 performs temperature, impedance, and force measurements, and these measurement results are delivered to the processor 101a.

[0052] Moving to block 310, the processor 101a uses the estimated tip 28 depth (from block 306), the blood conductivity (σ), and the actual temperature and impedance measurements currently being made at the catheter tip 28 to create a finite element (FE) model. The FE model includes temperature and impedance values calculated at multiple sub-regions of a 3D region referred to as the temperature domain. The temperature domain generally includes regions of tissue (e.g., regions and hot spots), the tip 28 of the catheter 14 and the sensors, and regions adjacent to the tissue where liquids such as blood and flushing saline may be present. Note that the sensors at the tip 28 of the ablation catheter 14 reside in some of the sub-regions of the FE model. An example FE model is disclosed in "Chamber-Specific Radiofrequency Lesion Dimension Estimation Using Novel Catheter-Based Tissue Interface Temperature Sensing" by J. Kosuth et al., JACC: Clinical Electrophysiology, as described in detail above. The implementation of the FE model in this embodiment is further described in the appendix.

[0053] The process moves to block 312, where the processor 101a compares the calculated temperature and impedance values of the FE model with the actual measurements of the probe sensors. In the case where there is no match at block 312, the processor re-estimates the tip penetration depth at the re-estimation step 314 and loops back to step 310, from which the process starts over. The loop of re-estimating the penetration depth at block 314 continues by repeating the process of block 306, incorporating and adjusting (at block 310) the FE model until the processor 101a finds a match at block 312.

[0054] If there is a match, at block 312, the process proceeds to block 316, where a real-time model predicting the variation of the hot spot temperature and pressure over time is created for a given blood conductivity and ablation lesion size. The real-time model is based at least on the tip (probe) penetration depth estimated at block 306 or 314 (which is a "free parameter" of the model) and on the ablation current used to activate the RF generator 50. The model generally includes a predicted evolution curve of the temperature and / or pressure at the hot spot. Alternatively, the model can include a table of temperature / pressure and time points. Further alternatively, the model can include any other suitable form, such as a mathematical formula.

[0055] Based on the model and a predetermined temperature / pressure threshold, the process moves to block 318, where at block 320 it is determined whether the now-determined hot spot temperature meets the target temperature. The target temperature is the desired temperature of the ablation point, which is high enough to cause tissue necrosis while avoiding steam bursts and is obtained, for example, from a look-up table or the like.

[0056] Return to block 318. If the hot spot temperature does not meet the target temperature (such as programmed into system 100), the process moves to block 322. At block 322, the PID controller (PID control module 108) changes the RF generator 50 current supply to the end of catheter 28 based on the difference between the hot spot temperature and the target temperature. The process moves to block 316 and restarts from this block.

[0057] Alternatively, at block 318, if the hot spot temperature meets the target temperature, the process moves to block 324. At block 324, the processor determines whether ablation is complete. For example, to determine whether ablation is complete, if the amount of energy applied to the tissue (e.g., the product of RF power and duration) exceeds a predefined threshold, physician 24 may terminate the ablation.

[0058] Alternatively or additionally, physician 24 may decide to terminate ablation by consulting any suitable information presented on display 27 during the ablation process. Further alternatively or additionally, the processor may automatically decide to terminate ablation using, for example, the method described in U.S. Patent No. 8,900,225, the disclosure of which is incorporated herein by reference in its entirety.

[0059] At block 324, when ablation is complete, the process (method) of ablation lesion assessment algorithm 102 terminates at termination step 326.

[0060] Otherwise, at block 324, if ablation is not complete, the processor loops back to step 310 to readjust the FE model in the case where a deviation from the model has occurred. Factors that may cause a deviation in the FE model include, for example, relative tissue probe movement resulting from the heartbeat and breathing operations of patient 23. Note that after adjusting the FE model at step 310, there may be a corresponding update of the real-time model at block 316 and a corresponding update of the predicted occurrence time of the steam burst event at block 320.

[0061] This process can be repeated as long as needed.

[0062] Alternatively or additionally, the physician 24 can adjust the position or penetration depth of the catheter 14 into the tissue, or even temporarily remove the catheter so that it is not in contact with the tissue. If the prediction model indicates a slowly rising temperature / pressure curve, the physician 24 can apply an increased force on the catheter 14 to insert it deeply into the tissue. However, in the case where the model indicates an impending steam burst event, the physician 24 can partially or completely remove the catheter 14 from the tissue. Further alternatively or additionally, the physician 24 can control the irrigation rate in response to the model indication and / or any other suitable means that can affect the temperature / pressure evolution rate. The physician 24 can also take various actions in parallel to respond and reduce the risk of styloid events.

[0063] Figure 4 A flowchart of a process for determining whether a patient is a suitable candidate for ablation based on blood conductivity is illustrated. For example, when the conductivity of the blood is below a certain value (about 4 microsiemens per centimeter (mS / cm)), more ablation current flows to the tissue compared to a normal blood conductivity of about 6.5 mS / cm. When such a large amount of current reaches the tissue, the tissue heats up faster, resulting in greater damage, which is accompanied by risk factors such as steam bursts, charring, and / or overheating of the esophagus.

[0064] The process begins at block 402, where the blood conductivity is obtained by one of the processes detailed above. The process moves to block 404, where it is determined whether the blood conductivity measurement is less than a threshold, such as 4 mS / cm.

[0065] If "yes" at block 404, the process moves to block 406, where a temperature-guided (e.g., controlled) catheter is selected for the procedure. The temperature sensor of such a catheter continuously monitors the temperature at the tip, where ablation occurs. This real-time feedback allows the procedure to be adjusted quickly enough based on how the patient's tissue responds to avoid damage to healthy tissue. Then, the process moves to block 408, where the ablation procedure continues.

[0066] Alternatively, if "no" at block 404, the process moves directly to block 408, where the ablation procedure continues.

[0067] The process moves from block 408 to block 410, where the ablation procedure ends.

[0068] Although the examples described herein primarily address ablation of cardiac tissue, other tissues can also be ablated by the devices and methods disclosed herein.

[0069] Specific implementations of the example methods and / or systems of the present disclosure may involve manually performing or completing selected tasks, automatically performing or completing selected tasks, or a combination thereof. Additionally, depending on the actual instrumentation and equipment of the example methods and / or systems of the present disclosure, several selected tasks may be implemented by hardware, by software, or by firmware, or by a combination thereof using an operating system or a cloud-based platform.

[0070] For example, the hardware for performing selected tasks according to the examples of the present disclosure may be implemented as a chip or a circuit. As software, the selected tasks according to the examples of the present disclosure may be implemented as multiple software instructions executed by a computer using any suitable operating system. In an exemplary example of the present disclosure, one or more tasks according to the exemplary examples of the method and / or system described herein are executed by a data processor, such as a computing platform for executing multiple instructions. Optionally, the data processor includes volatile memory for storing instructions and / or data, and / or non-volatile storage devices for storing instructions and / or data, such as non-transitory storage media, such as magnetic hard disks and / or removable media. Optionally, a network connection is also provided. Optionally, a display and / or user input devices such as a keyboard or a mouse are also provided.

[0071] For example, according to the above examples of the present disclosure, any combination of one or more non-transitory computer-readable (storage) media may be utilized. The non-transitory computer-readable (storage) media may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (non-exhaustive list) of the computer-readable storage medium will include the following: an electrical connection having one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, the computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0072] A computer-readable signal medium can include, for example, a propagated data signal in a baseband or as part of a carrier wave, the propagated data signal having computer-readable program code embodied therein. Such a propagated signal can take any of a variety of forms, including but not limited to electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium that is not a computer-readable storage medium and can convey, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device.

[0073] As will be understood with reference to the paragraphs provided above and the accompanying drawings, various examples of computer-implemented methods are provided herein, some of which can be performed by various examples of the apparatuses and systems described herein and some of which can be performed in accordance with instructions stored on non-transitory computer-readable storage media described herein. Additionally, some examples of the computer-implemented methods provided herein can be performed by other apparatuses or systems and can be performed in accordance with instructions stored on computer-readable storage media other than the computer-readable storage media described herein, as will become apparent to those skilled in the art with reference to the examples described herein. Any reference to a system and a computer-readable storage medium with respect to the following computer-implemented methods is provided for purposes of explanation and is not intended to limit any of such systems among the systems described above with respect to examples of the computer-implemented methods and any non-transitory computer-readable storage media among such non-transitory computer-readable storage media. Similarly, any reference to the following computer-implemented methods with respect to a system and a computer-readable storage medium is provided for purposes of explanation and is not intended to limit any of the computer-implemented methods among the computer-implemented methods disclosed herein.

[0074] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various examples of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of code that includes one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the accompanying drawings. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, and combinations of blocks in the block diagrams and / or flowcharts diagrams, and combinations of blocks in the block diagrams and / or flowcharts diagrams can be implemented by systems based on dedicated hardware for performing the specified functions or actions, or by combinations of dedicated hardware and computer instructions. The description of the various examples of the present disclosure is presented for purposes of illustration, but is not intended to be exhaustive or limited to the examples disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described examples.

[0075] Ablation Lesion Evaluation Algorithm

[0076] The disclosed ablation lesion assessment algorithm (102) is used to evaluate ablation lesion parameters using the temperature measured by a treatment catheter. The ablation lesion parameters are the ablation lesion size (width and depth) and the highest temperature developed in the tissue (hot spot).

[0077] The algorithms described in the following sections run in real time, but are based on offline-compiled data, look-up tables (LUTs), and pre-collected material properties. This contributes both to the relative simplicity of the algorithms and to their speed, without significantly reducing their accuracy.

[0078] Variations in the measurements caused by the heartbeat and even respiration have little effect on ablation lesion formation because the thermal timescale (the time it takes for the temperature front to propagate in the spatial scale of the problem or for the temperature field to change significantly) is on the order of several seconds.

[0079] The heartbeat and respiratory motion cause movement of the catheter relative to the tissue, which in turn causes variations in the measured temperature as the sensor moves relative to the ablation lesion.

[0080] Conversely, with the help of the large heat capacity of the tissue, heat generation in the tissue can be kept stable.

[0081] The tissue heat capacity thus acts as a low-pass filter, averaging out the fluctuations.

[0082] Basic Operating Principle

[0083] Offline (generate look-up table (LUT) model):

[0084] ● Perform all simulations for relevant ablation settings (simulated current, catheter penetration / depth, impedance, ablation time, blood conductivity, etc.)

[0085] Running time:

[0086] 1. Start ablation and measure data from catheter sensors (temperature, impedance).

[0087] 2. The behavior of the measured values is unique and similar to the values generated by specific simulations (especially in the sense of being generated using specific catheter depths, currents, material properties, etc.).

[0088] The data from this simulation can be retrieved from the relevant look-up table.

[0089] 3. The simulated output look-up table includes parameters that are not directly measured, including the extent and form of the temperature field in the tissue, and the measured values that we would have obtained if reality were the same as the simulation.

[0090] By continuously comparing the measured temperature and the simulated temperature, select the best simulated scenario database

[0091] and extract the ablation lesion size and maximum temperature (hot spot) from it.

[0092] Simulation and Model Generation

[0093] To perform the simulations required to generate the data used by the algorithm, the following parameters are needed:

[0094] 1. The catheter tip structure including the insert and temperature sensor.

[0095] 2. The power / current range applied during ablation.

[0096] 3. The catheter penetration depth / angle range specifying the contact geometry.

[0097] 4. Material properties (e.g., thermal conductivity / electrical conductivity, temperature range, flushing flow rate, etc.)

[0098] 5. Ablation site properties (RA, RV, geometry of the tissue, and the presence of, for example, fat layer / lung / pericardium).

[0099] 6. The range of blood conductivity.

[0100] Use multiple parameter combinations from the above set to generate a database that constitutes the input to the algorithm (i.e., the LUT).

[0101] All models are run assuming an ablation duration of up to 125 seconds, and the current range covers the range used in electrophysiological ablation practice.

[0102] Each simulation generates a time-varying temperature field. These results can be parsed into algorithm-relevant data such as ablation lesion width / depth (defined as the ablation lesion boundary at the 57°C isotherm), and maximum tissue temperature (hot spot).

[0103] After completing the simulations covering all parameter combinations and variations, the following results are extracted into the algorithm input database:

[0104] ● Ablation lesion depth

[0105] ● Ablation lesion width

[0106] ● Measured temperature

[0107] ● Temperature at the hottest tissue point

[0108] All parameters are organized in a table:

[0109] Value(time = t, penetration = D, current = I, conductivity = C)

[0110] such that each value corresponds to a specific time, catheter penetration depth, ablation current, and blood conductivity.

[0111] Each parameter is described as a function of (t, D, I, C) by using linear interpolation of the values within the set (t, D, I, C). This provides a continuous function for use as an algorithm to predict ablation lesion progression.

[0112] Data Pre - processing

[0113] Maximum Measured Temperature :

[0114] Among all the temperature measurements (e.g., six measurements in a QDOT catheter), only the maximum value is passed to the algorithm. The implicit assumption is that the sensor with the highest measured temperature is the closest to the ablation lesion and thus the most suitable for evaluating the ablation lesion.

[0115] Instantaneous Loss of Contact :

[0116] As long as the catheter tip is in contact with the tissue and the ablation current heats the tissue, the local reduction of tissue temperature will not be rapid.

[0117] Therefore, when the measured temperature shows a rapid decline, we can assume that the measured temperature decline is due to the instantaneous loss of contact of the measurement sensor, rather than a true decline in tissue temperature. This intermittent contact represents the tissue temperature during its "high" points, and only these points will correctly represent the tissue temperature. Example

[0118] Example 1

[0119] A method for performing ablation of a patient's tissue using an ablation catheter (14), the method comprising obtaining (402) a blood conductivity value of blood of a blood pool associated with the ablation catheter and the tissue to be ablated. Calculating (316) ablation energy required to ablate the tissue based on ablation parameters including the blood conductivity value. Evaluating (310) the size of an ablation lesion to be created by the ablation energy based on the calculated ablation energy.

[0120] Example 2

[0121] The method according to embodiment 1, wherein calculating (316) the ablation energy further comprises applying a hot spot temperature of the ablation lesion to be ablated to the calculation.

[0122] Example 3

[0123] The method according to embodiment 1, wherein evaluating (310) the ablation lesion size further comprises estimating (306) an initial penetration depth of the distal end of the catheter into the tissue, and using the estimated initial penetration depth and the blood conductivity value and current actual temperature and impedance measurements taken at the distal end to create a finite element (FE) model of a three-dimensional (3D) temperature distribution in the tissue, and estimating (316) the size of the ablation lesion from the temperature distribution.

[0124] Example 4

[0125] The method according to embodiment 3, and comprising adjusting (322) the ablation energy based on the size of the ablation lesion.

[0126] Example 5

[0127] The method according to embodiment 1, and comprising selecting (406, 408) a catheter type based on the obtained blood conductivity value.

[0128] Example 6

[0129] The method according to embodiment 1, wherein obtaining (402) the blood conductivity value comprises determining the blood conductivity value from a blood sample of the patient prior to ablation.

[0130] Example 7

[0131] The method according to embodiment 1, wherein evaluating (310) the size of the ablation lesion comprises using a pre-made look-up table with entries for ablation lesion depth, ablation lesion width, measured temperature, and temperature at the hottest tissue point.

[0132] Example 8

[0133] The method according to Example 1, wherein evaluating (310) the size of the ablation lesion includes evaluating the depth and lateral dimension of the ablation lesion.

[0134] Example 9

[0135] A system (10) for performing ablation of tissue of a patient using an ablation catheter (14), the system including an interface (30) and a processor (101a). The interface is configured to obtain (402) a blood conductivity value of blood of a blood pool associated with the ablation catheter and the tissue to be ablated. The processor (101a) is configured to calculate (316) ablation energy required to ablate the tissue based on ablation parameters including the blood conductivity value, and to evaluate (310) the size of an ablation lesion to be created by the ablation energy based on the calculated ablation energy.

[0136] As used herein, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural referents.

[0137] It should be understood that, for clarity, certain features of the present disclosure described in the context of separate examples may also be provided in combination in a single example. Conversely, for brevity, the various features of the present disclosure described in the context of a single example may also be provided separately or in any suitable sub-combination or as suitably provided in any other described example of the present disclosure. Certain features described in the context of various examples should not be considered essential features of those examples unless the example does not function without those elements.

Claims

1. A method for performing ablation of a patient's tissue using an ablation catheter, the method comprising: Obtaining a blood conductivity value of blood in a blood pool associated with the ablation catheter and the tissue to be ablated; Calculating ablation energy required for ablating the tissue based on ablation parameters including the blood conductivity value; And Evaluating the size of an ablation lesion to be generated by the ablation energy based on the calculated ablation energy.

2. The method according to claim 1, wherein calculating the ablation energy further comprises applying a hot spot temperature of an ablated ablation lesion to the calculation.

3. The method according to any one of claims 1 to 2, wherein evaluating the size of the ablation lesion further comprises: Estimating an initial penetration depth at which a distal end of the catheter penetrates into the tissue; And Using the estimated initial penetration depth, the blood conductivity value, and current actual temperature and impedance measurements taken at the distal end to create a finite element (FE) model of a three-dimensional (3D) temperature distribution in the tissue; and estimating the size of the ablation lesion based on the temperature distribution.

4. The method according to claim 3, and comprising adjusting the ablation energy based on the size of the ablation lesion.

5. The method according to any one of claims 1 to 2, and comprising selecting a catheter type based on the obtained blood conductivity value.

6. The method according to any one of claims 1 to 2, wherein, Obtaining the blood conductivity value comprises determining the blood conductivity value from a blood sample of the patient before the ablation.

7. The method according to any one of claims 1 to 2, wherein, Evaluating the size of the ablation lesion comprises using a pre-made look-up table with entries for ablation lesion depth, ablation lesion width, measured temperature, and temperature at the hottest tissue point.

8. The method according to any one of claims 1 to 2, wherein Evaluating the size of the ablation lesion comprises evaluating the depth and lateral dimensions of the ablation lesion.

9. A system for performing ablation of a patient's tissue using an ablation catheter, the system comprising: An interface configured to obtain a blood conductivity value of blood in a blood pool associated with the ablation catheter and the tissue to be ablated; And A processor configured to: Calculate ablation energy required for ablating the tissue based on ablation parameters including the blood conductivity value; And Evaluate the size of an ablation lesion to be generated by the ablation energy based on the calculated ablation energy.

10. The system according to claim 9, wherein, The processor is configured to: calculate the ablation energy by applying a hot spot temperature of an ablated ablation lesion to the calculation.

11. The system according to any one of claims 9 to 10, wherein, The processor is configured to evaluate the ablation lesion size by: estimating an initial penetration depth at which a distal end of the catheter penetrates into the tissue; And using the estimated initial penetration depth, the blood conductivity value, and current actual temperature and impedance measurements taken at the distal end to create a finite element (FE) model of a three-dimensional (3D) temperature distribution in the tissue; and estimating the size of the ablation lesion based on the temperature distribution.

12. The system according to claim 11, wherein The processor is configured to adjust the ablation energy based on the size of the ablation lesion.

13. The system according to any one of claims 9 to 10, wherein, The processor is configured to select a catheter type based on the obtained blood conductivity value.

14. The system according to any one of claims 9 to 10, wherein, The processor is configured to obtain the blood conductivity value by determining the blood conductivity value from a blood sample of the patient before the ablation.

15. The system according to any one of claims 9 to 10, wherein, The processor is configured to evaluate the size of the ablation lesion by using a pre-made look-up table with entries for ablation lesion depth, ablation lesion width, measured temperature, and temperature at the hottest tissue point.

16. The system according to any one of claims 9 to 10, wherein, The processor is configured to evaluate the size of the ablation lesion by evaluating the depth and lateral dimensions of the ablation lesion.

Images