A local impedance based determination system

Abstract

The application discloses a local impedance-based judgment system, which obtains an excitation source of an ablation electrode to be measured and a voltage difference between the ablation electrode to be measured and an ablation electrode adjacent to the ablation electrode to be measured; then, according to the excitation source, the voltage difference and a preset formula, the local impedance of the ablation electrode to be measured is obtained; the local impedance of the ablation electrode to be measured is received and judged to determine the position of the pulse ablation catheter in a cardiac cavity and the energy output timing. The system judges the local impedance to determine the position of the pulse ablation catheter in the cardiac cavity and the energy output timing, can accurately and effectively judge whether the ablation electrode transmitting the local impedance is in stable contact or excessive contact with the tissue, and takes corresponding measures according to the judgment result, thereby effectively solving the problem of unstable ablation damage.

Description

[0001] This application is a divisional application of application number "202310347853.1", filed on April 3, 2023, entitled "A method and system for determining local impedance". Technical Field

[0002] This application relates to the field of ablation technology, and in particular to a judgment system based on local impedance. Background Technology

[0003] Atrial fibrillation is a rapid arrhythmia that is common in the elderly, with an incidence rate of up to 10% in people over 75 years of age. During atrial fibrillation, the atrial excitation frequency reaches 300 to 600 beats per minute, and the ventricular rate is often fast and irregular, sometimes reaching 100 to 160 beats per minute. It is not only much faster than a normal heartbeat, but also completely irregular, and the atria lose their effective contraction function. The prevalence of atrial fibrillation is also closely related to diseases such as coronary heart disease, hypertension, and heart failure.

[0004] Treatment options for atrial fibrillation include pharmacological and non-pharmacological therapies. Pharmacological therapies can be categorized by their mechanism of action into sodium channel blockers, beta-blockers, action potential duration prolongers, and calcium channel blockers. Generally, pharmacological therapy is the first-line treatment, but it requires long-term use and carries side effects. Since some patients with arrhythmias cannot control their condition with medication, non-pharmacological therapies can help control their heart rhythm and improve symptoms, such as catheter ablation, pacemaker implantation, and surgical intervention.

[0005] Pulmonary vein electrical isolation is a recognized strategy for catheter ablation of atrial fibrillation and is also one of the procedures in catheter ablation surgery. The operator inserts the ablation catheter into the left atrium and performs circumferential ablation of the myocardium at the pulmonary vein orifice / vesicle. Point-to-point ablation with a straight catheter with a single ablation electrode is the traditional surgical method. The electrode at the tip of the ablation catheter can output ablation energy, while the other electrodes on the catheter body can only be used to record intracardiac electrical signals. A pressure sensor is placed inside the straight catheter with a single ablation electrode, and the pressure generated when it is in contact with the ablation electrode is used to detect the degree of coupling between the tissue and the ablation electrode. However, multi-electrode ablation catheters do not have space to place a pressure sensor, so they cannot detect the degree of coupling between the ablation electrode and the tissue by pressure, resulting in unstable ablation damage.

[0006] Therefore, providing a method and system based on local impedance that can accurately assess whether the discharge electrode is stably or excessively attached to the tissue is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a judgment system based on local impedance, which can accurately determine whether the ablation electrode is stably or excessively attached to the tissue, and take corresponding measures based on the judgment results, thereby effectively solving the problem of unstable ablation damage;

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] A local impedance-based judgment system performs the following steps: acquiring an excitation source for the circuit formed by the ablation electrode to be measured and an unrelated electrode; wherein the ablation electrode to be measured is disposed on a pulsed ablation catheter, and the unrelated electrode is not disposed on the pulsed ablation catheter; acquiring the voltage difference between the ablation electrode to be measured and an adjacent ablation electrode through the pulsed ablation catheter; wherein the adjacent ablation electrode is disposed on the pulsed ablation catheter; acquiring the local impedance of the ablation electrode to be measured according to the excitation source, the voltage difference, and a preset formula; receiving and judging the local impedance of the ablation electrode to be measured to determine the position of the pulsed ablation catheter in the cardiac cavity and the timing of energy output adjustment; wherein judging the local impedance includes judging the local impedance according to a target baseline, the target baseline being acquired according to a preset rule.

[0010] This invention also provides a technical solution: a system for determining local impedance, characterized in that it includes: a pulsed ablation catheter, a pulsed electric field ablation device, a connecting fiber, and an unrelated electrode; the pulsed ablation catheter is connected to the pulsed electric field ablation device via the connecting fiber; the unrelated electrode is connected to the pulsed electric field ablation device via the connecting fiber; the pulsed ablation catheter is used to obtain local impedance based on an excitation source and a voltage difference; wherein an adjacent ablation electrode is disposed on the pulsed ablation catheter; the pulsed electric field ablation device is used to receive the local impedance and determine the local impedance; wherein determining the local impedance includes determining the local impedance based on a target baseline, the target baseline being obtained according to a preset rule; wherein the pulsed ablation catheter is used to measure the local impedance and release ablation energy, and the ablation electrode in contact with myocardial tissue can be obtained based on the local impedance generated by each ablation electrode on the pulsed ablation catheter; the timing of the ablation electrode outputting energy can be adjusted.

[0011] This invention provides a system for determining local impedance. It acquires the excitation source of the ablation electrode to be measured and the voltage difference between the ablation electrode and an adjacent ablation electrode. Then, based on the excitation source, voltage difference, and a preset formula, the local impedance of the ablation electrode is obtained. The system receives and judges the local impedance of the ablation electrode to determine the position of the pulsed ablation catheter within the heart cavity and the timing of energy output adjustment. By measuring the excitation source and voltage difference of the ablation electrode to be measured, and calculating the local impedance based on these factors, this system determines the position of the pulsed ablation catheter within the heart cavity and the timing of energy output adjustment. It can accurately and effectively determine whether the ablation electrode transmitting local impedance is stably or excessively attached to the tissue, and takes corresponding measures based on the judgment results, thereby effectively solving the problem of unstable ablation damage. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of the method for determining local impedance in an embodiment of the present invention;

[0014] Figure 2 This is a flowchart of step S4 in an embodiment of the present invention;

[0015] Figure 3 This is a schematic diagram of the structure of the judgment system based on local impedance in an embodiment of the present invention;

[0016] Figure 4 This is a schematic diagram of the pulse ablation catheter in an embodiment of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] like Figure 1 As shown, this embodiment of the invention provides a method for determining local impedance, including the following steps:

[0019] S1. Obtain the excitation source of the ablation electrode to be measured;

[0020] S2. Obtain the voltage difference between the ablation electrode to be measured and an adjacent ablation electrode;

[0021] S3. Obtain the local impedance of the ablation electrode to be measured based on the excitation source, voltage difference, and preset formula;

[0022] S4. Obtain the target baseline according to preset rules;

[0023] S5. Determine the local impedance of the ablation electrode to be measured based on the target baseline.

[0024] In step S1, a circuit is formed by the ablation electrode to be measured and the unrelated electrode (negative plate), which generates an excitation source of a certain amplitude, thereby forming a stable electric field. The frequency of the excitation source can be 1kHz to 1MHz, and the range is not limited. In this embodiment, 10kHz to 100kHz is preferred.

[0025] In step S2, in this embodiment, multiple ablation electrodes are used, and each ablation electrode is located in a different position, so the voltage generated by each ablation electrode is also different. Therefore, it is necessary to calculate the voltage difference of the ablation electrode to be measured.

[0026] In step S3, the local impedance is calculated using the excitation source obtained in step S1 and the voltage difference obtained in step S2, according to a preset formula.

[0027] The default formula is:

[0028] Zm=V_0 / V_1

[0029] Where Zm is the local impedance; V_0 is the voltage difference; and V_1 is the excitation source.

[0030] In step S4, the difference in blood and myocardial conductivity leads to changes in local impedance. The algorithm determines whether the catheter has coupled with the myocardium by the magnitude of the increase. The size of the measuring electrode and the distance between it and its adjacent electrodes directly affect the measured local impedance. Therefore, there is a correlation between the type of pulse ablation catheter and the value of local impedance, and different patients will have different blood conductivity. In pulse ablation catheters with multiple electrodes, the local impedance measured by each electrode is not different, but there is an error of ±1Ω between the channel connecting each electrode to the device. Therefore, the local impedance measured by the system has a difference of ±1Ω. Therefore, in order to make the baseline range more robust, a target baseline is obtained by preset rules.

[0031] In step S5, after obtaining the target baseline in step S4, the calculated local impedance of the ablation electrode to be measured at every moment is compared with the target baseline and a judgment is made.

[0032] Preferably, step S1 includes the following steps:

[0033] A1. Obtain the first voltage value of the ablation electrode to be measured;

[0034] A2. Obtain the second voltage value of the preset resistor;

[0035] A3. Obtain the excitation source of the ablation electrode to be measured based on the first voltage value, the second voltage value, and the preset resistance value.

[0036] In steps A1 to A3, firstly, the first voltage value V_AN1 of the electrode to be ablated is obtained, and then the second voltage value Vs of the preset resistor is obtained. Since the preset resistor is a fixed resistor Zc, there is no need to obtain the resistance value of the preset resistor again, and it can be used directly. Then, the excitation source V1 is calculated using a preset formula. The preset formula is as follows:

[0037] V1=(Vs-V_AN1) / Zc.

[0038] Preferably, step S2 includes the following steps:

[0039] B1. Obtain the third voltage of the ablation electrode to be measured;

[0040] B2. Obtain the fourth voltage of the ablation electrode adjacent to the ablation electrode to be measured;

[0041] B3. Obtain the voltage difference between the ablation electrode to be measured based on the third and fourth voltages.

[0042] In step B1, the third voltage of the ablation electrode to be measured is measured using the equipment. Those skilled in the art can also select suitable equipment to perform voltage measurement according to the actual situation. In this embodiment, a pulse electric field ablation device is used.

[0043] In step B2, the fourth voltage of the next ablation electrode adjacent to the ablation electrode to be measured is also measured using the same equipment. Those skilled in the art can also select suitable equipment to perform voltage measurement according to the actual situation. In this embodiment, a pulse electric field ablation device is used.

[0044] In step B3, the voltage difference of the ablation electrode to be measured is obtained by subtracting the third voltage obtained in step B1 from the fourth voltage obtained in step B2. The last ablation electrode on the annular end tube needs to have its voltage difference measured against its adjacent previous ablation electrode.

[0045] like Figure 2 As shown, preferably, step S4 includes the following steps:

[0046] C1. Obtain the impedance data of the ablation electrode according to the preset time;

[0047] C2. Obtain the quartiles and median based on the impedance data;

[0048] C3. Obtain the initial baseline;

[0049] C4. Update the initial baseline based on the quartiles and median to obtain the target baseline.

[0050] In step C1, after all ablation electrodes have just entered the heart chamber, the impedance data of all ablation electrodes needs to be initialized. Then, according to the preset time, the impedance data around the electrodes is collected in real time during the movement of the ablation electrodes in the heart. The minimum value of the impedance data obtained in each frame is arranged in ascending order.

[0051] In step C2, the impedance data obtained in step C1 is calculated according to a preset statistical method to obtain the quartiles and median. This effectively filters out detected outliers, such as intracardiac metal implants, and can best reflect the impedance around the catheter during initialization. At the same time, the quartiles are set as the minimum baseline, and the median plus X is set as the maximum baseline because the local impedance of blood in the atrium is slightly less than the local impedance when the catheter is suspended at the pulmonary vein orifice. The baseline range at this time is greater than or equal to the quartiles and less than or equal to the median plus X. This can effectively obtain the reasonable baseline range of the current catheter in this cardiac chamber, making the contact judgment more accurate.

[0052] In step C3, firstly, the impedance data of the electrode to be ablated is obtained. The impedance data is obtained once every Y seconds, and the minimum value of the obtained impedance data is used as the initial baseline.

[0053] In step C4, after the initialization settings are completed, the catheter can operate normally. During the operation, the initial baseline obtained in step S3 will be updated based on the baseline range formed by the quartiles and medians obtained in step C2. If the initial baseline is within the baseline range, it will be updated and output as the target baseline; if the initial baseline is not within the baseline range, it will not be updated.

[0054] Preferably, step S5 includes the following steps:

[0055] If the local impedance is greater than the target baseline, the ablation electrode that transmits the local impedance is attached.

[0056] If the local impedance is less than the target baseline, the ablation electrode transmitting the local impedance will not be in contact with the target.

[0057] In practical applications, the conductivity of blood is higher than that of the heart. When there is only blood around the ablation electrode, the local impedance of the ablation electrode is relatively low, approximately 70-90Ω. When the ablation electrode comes into contact with myocardial tissue within the heart chamber, the local impedance measured by the ablation electrode will increase significantly, reaching over 100Ω. Therefore, it is necessary to judge the local impedance based on the target baseline. If the local impedance is greater than the target baseline, it indicates that the ablation electrode transmitting this impedance is in close contact with the myocardial tissue; if the local impedance is less than the target baseline, it indicates that the ablation electrode transmitting this impedance is not in close contact with the myocardial tissue.

[0058] Meanwhile, due to the heart's own rhythmic beating, after the ablation electrode comes into contact with the myocardium, the measured local impedance not only shows a significant increase, but also exhibits periodic and stable fluctuations in impedance at certain locations within the heart. For example, the heart undergoes periodic diastole and systole under its own rhythmic control, with the ventricular volume during diastole being more than twice that during systole. The intense movement of the ventricular free wall may cause the tip of the catheter to come into contact with the myocardium during part of the cardiac cycle, so local impedance fluctuations with the same duration as the cardiac cycle can be observed.

[0059] like Figure 3 As shown, this embodiment of the invention also provides a judgment system based on local impedance, based on the judgment method based on local impedance according to any one of claims 1-5, including: a pulse ablation catheter 1, a pulse electric field ablation device 2, a connecting pigtail 3, an unrelated electrode 4, and a three-dimensional positioning and navigation system 5;

[0060] The pulse ablation catheter 1 is connected to the pulse electric field ablation device 2 via the connecting tail fiber 3;

[0061] The unrelated electrode 4 is connected to the pulse electric field ablation device 2 via the connecting pigtail 3;

[0062] The pulsed electric field ablation device 2 is connected to the three-dimensional positioning and navigation system 5 via a connecting pigtail 3;

[0063] Pulse ablation catheter 1, used to obtain local impedance based on excitation source and voltage difference;

[0064] Pulsed electric field ablation device 2 is used to process local impedance according to the target baseline;

[0065] The three-dimensional positioning and navigation system 5 is used to receive initialization commands;

[0066] The three-dimensional positioning and navigation system 5 is also used to receive the judgment results of the pulse ablation device 2.

[0067] In practical applications, the pulse ablation catheter transmits its local impedance to the pulse electric field ablation device via a connecting fiber optic cable. The device receives and analyzes the local impedance of the pulse ablation catheter via the connecting fiber optic cable. Through an unrelated electrode, a complete circuit is formed with the pulse ablation catheter. Upon receiving the initialization command, the three-dimensional positioning and navigation system initializes the impedance data of the ablation electrode. The pulse ablation device uploads the local impedance of the electrode to be measured to the three-dimensional positioning and navigation system and renders it in color for doctors to observe and interpret. It can also be used to determine the catheter's position within the heart chambers, adjust the timing of energy output, and monitor the patient's intracardiac electrophysiological signals.

[0068] like Figure 4 As shown, preferably, the pulse ablation catheter 1 includes: an ablation electrode 11, an annular end tube 12, a tube body 13, a positioning electrode 14, a handle 15, and a connector 16;

[0069] The annular end tube 12 is connected to the tube body 13;

[0070] Connector 16 is connected to tube body 13 via handle 15;

[0071] The ablation electrode 11 is disposed on the annular end tube 12;

[0072] Positioning electrode 14 is disposed on tube body 13;

[0073] Ablation electrodes are used to measure local impedance and release ablation energy.

[0074] The annular end tube is used to support the ablation electrode;

[0075] Positioning electrodes are used to provide magnetic position information.

[0076] In practical applications, the ablation electrode is placed on the annular end tube, and the positioning electrode is placed on the tube body. This allows both the ablation electrode on the annular end tube and the positioning electrode on the tube body to perform local impedance measurements. In this embodiment, all electrodes of the annular end tube can participate in ablation discharge, and the patient's myocardium, ablation electrode, catheter, cable, and ablation device form an electrical circuit. All ablation electrodes and unrelated electrodes (negative plates) can form a communication circuit for local measurement. In this embodiment, the ablation electrode is 2mm long and 1.5mm wide, and the distance between electrode edges is 4mm.

[0077] In the embodiments provided in this application, it should be understood that the disclosed methods and systems can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple modules or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, and can be electrical, mechanical, or other forms.

[0078] Furthermore, in the various embodiments of the present invention, each functional module can be fully integrated into a processor, or each module can be a separate device, or two or more modules can be integrated into a device; each functional module in the various embodiments of the present invention can be implemented in hardware or in the form of hardware plus software functional units.

[0079] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by program instructions and related hardware. The aforementioned program instructions can be stored in a computer-readable storage medium. When the program instructions are executed, they perform the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0080] It should be understood that the use of terms such as "system," "device," "unit," and / or "module" in this application is merely one method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0081] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0082] Hereinafter, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature.

[0083] If a flowchart is used in this application, it is used to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A judgment system based on local impedance, characterized in that, The judgment system performs the following steps: Obtain the excitation source for the circuit formed by the ablation electrode to be measured and the irrelevant electrode; wherein, the ablation electrode to be measured is disposed on the pulse ablation catheter, and the irrelevant electrode is not disposed on the pulse ablation catheter; The voltage difference between the ablation electrode to be measured and an adjacent ablation electrode is obtained through the pulse ablation catheter; wherein, the adjacent ablation electrode is disposed on the pulse ablation catheter; The local impedance of the ablation electrode to be measured is obtained based on the excitation source, the voltage difference, and the preset formula. The local impedance of the ablation electrode to be measured is received and judged to determine the position of the pulse ablation catheter in the heart cavity and the timing of energy output adjustment; The determination of the local impedance includes determining the local impedance based on a target baseline, which is obtained according to a preset rule.

2. The judgment system based on local impedance according to claim 1, characterized in that, The judgment system also performs the following steps: After the local impedance of the ablation electrode to be measured is uploaded to the three-dimensional positioning and navigation system, color rendering is performed.

3. The judgment system based on local impedance according to claim 1, characterized in that, The ablation electrode to be measured is also used to release ablation energy.

4. The system for determining local impedance according to any one of claims 1-3, characterized in that, The process of obtaining the excitation source for the circuit formed by the ablation electrode to be measured and the unrelated electrode includes the following steps: Obtain the first voltage value of the ablation electrode to be measured; Obtain the second voltage value of the preset resistor; The excitation source of the circuit formed by the ablation electrode to be measured and the unrelated electrode is obtained based on the first voltage value, the second voltage value and the preset resistance value.

5. The system for determining local impedance according to any one of claims 1-3, characterized in that, The step of obtaining the voltage difference between the ablation electrode to be measured and an adjacent ablation electrode includes the following steps: Obtain the third voltage of the ablation electrode to be measured; Obtain the fourth voltage of the ablation electrode adjacent to the ablation electrode to be measured; The voltage difference between the ablation electrode to be measured is obtained based on the third voltage and the fourth voltage.

6. The local impedance determination system according to claim 1, characterized in that, The step of determining the local impedance based on the target baseline includes the following steps: If the local impedance is greater than the target baseline, then the ablation electrode transmitting the local impedance is attached; If the local impedance is less than the target baseline, the ablation electrode transmitting the local impedance will not be in contact with the target baseline.

7. A judgment system based on local impedance, characterized in that, include: Pulsed ablation catheter, pulsed electric field ablation device, connecting pigtail, unrelated electrode; The pulse ablation catheter is connected to the pulse electric field ablation device via the connecting tail fiber; The unrelated electrode is connected to the pulsed electric field ablation device via the connecting pigtail; The pulsed ablation catheter is used to obtain local impedance based on the excitation source of the circuit formed by the ablation electrode to be measured and an unrelated electrode disposed on the pulsed ablation catheter and the voltage difference between the ablation electrode to be measured and an adjacent ablation electrode; wherein, the adjacent ablation electrode is disposed on the pulsed ablation catheter. The pulsed electric field ablation device is used to receive the local impedance and determine the local impedance; wherein, determining the local impedance includes determining the local impedance based on a target baseline, the target baseline being obtained according to a preset rule; The pulsed ablation catheter is used to measure the local impedance and release ablation energy. The ablation electrode that is in contact with the myocardial tissue can be obtained based on the local impedance generated by each ablation electrode on the pulsed ablation catheter. The timing of the ablation electrode outputting energy can be adjusted.

8. The local impedance determination system according to claim 7, characterized in that, The judgment system further includes a three-dimensional positioning and navigation system, which is used to receive initialization commands and receive the judgment results of the pulse ablation device on the local impedance; wherein, after the pulse ablation device uploads the local impedance of the ablation electrode to the three-dimensional positioning and navigation system, it performs color rendering.

9. The local impedance determination system according to claim 7 or 8, characterized in that, The pulse ablation catheter also includes: an annular end tube, a tube body, a positioning electrode, a handle, and a connector; The annular end tube is connected to the tube body; The connector is connected to the tube body via the handle; The ablation electrode is disposed on the annular end tube; The positioning electrode is disposed on the tube body; The annular end tube is used to carry the ablation electrode; The positioning electrode is used to provide magnetic position information.

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