Heart tissue ablation depth and range identification method and system based on catheter position

Abstract

The invention relates to a heart tissue ablation depth and range identification method and system based on a catheter position. The ablation depth identification method comprises the following steps: acquiring a cardiac cavity position of an ablation catheter and a cardiac muscle tissue thickness corresponding to the position, and establishing a relation function between a signal penetration energy threshold value required by a detection signal to penetrate through the cardiac muscle tissue and the ablation depth; setting a plurality of penetration signal energy levels for different set ablation depths based on the relation function; according to the sequence of the energy levels of the penetration signals from large to small, the ablation catheter is controlled to sequentially release the detection signals of the corresponding energy levels, and the obtained ablation depth is analyzed to be the set ablation depth corresponding to the detection signal with the minimum energy level of the received penetration signals. In combination with tissue thickness characteristics of different anatomical parts of the heart, detection signal energy levels are automatically distributed, and region matching and efficient detection are achieved. In addition, an ablation area model can be constructed in the detection process, and the real-time performance and accuracy of ablation integrity evaluation are improved.

Description

Technical Field

[0001] This invention relates to the field of medical device and medical image modeling technology, and in particular to a method and system for identifying the ablation depth and extent of cardiac tissue based on catheter location. Background Technology

[0002] Cardiac catheter ablation, particularly pulsed electric field (PFA) ablation, has become an important method for treating arrhythmias such as atrial fibrillation. Specifically, it involves inserting an electrode catheter into the main vein or artery (e.g., the femoral artery) to reach the heart chambers and perform ablation therapy. The core objective of ablation is to block abnormal activation pathways by creating an electrical conduction blockade zone, thereby achieving rhythm control. However, clinical studies and long-term follow-up show that the recurrence rate is closely related to whether the ablation is completely transmural and whether the blockade is continuous and closed-loop.

[0003] Currently used evaluation methods include the disappearance of hysteresis line potential, changes in interval signals, and reductions in local voltage. These methods essentially rely on indirect inference from local electrical signals and have the following significant limitations:

[0004] 1. Unable to confirm whether it is truly transmural: Especially in areas with large tissue thickness or complex anatomy (such as the roof of the left atrium and the ventricular septum), local signal changes may not mean that the tissue has completely lost its conduction ability, which can easily lead to the illusion of "effective on the surface, preserved in the deep".

[0005] 2. Inability to assess the continuity of blockage: Current assessments are mostly based on discrete potential points, which cannot continuously describe the boundary of the ablation region in space, and there is a risk of "jumping" missed judgments, which in turn affects the overall integrity of the blockage.

[0006] 3. Lack of quantitative depth information: Existing methods lack the ability to classify ablation depth, making it difficult to provide effective feedback for different energy ablation schemes;

[0007] 4. Evaluation results depend on the surgeon's experience: The ablation effect is usually subjectively judged by the surgeon through the potential changes of the three-dimensional mapping model, which is not standardized enough and the results are inconsistent.

[0008] Therefore, how to simultaneously assess changes in the state of ablated tissue during catheter manipulation and develop a quantifiable, continuous, and objective method for assessing the degree of transmural penetration is a key issue that urgently needs to be addressed in the field of interventional electrophysiology. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method and system for identifying the depth and range of cardiac tissue ablation based on catheter location, which can simultaneously assess changes in the state of ablated tissue during catheter operation and achieve quantifiable, continuous and objective ablation assessment of the degree of signal penetration.

[0010] The technical solution adopted by this invention to solve its technical problem is: to provide a method for identifying the ablation depth of cardiac tissue based on catheter location, comprising the following steps:

[0011] The location of the ablation catheter in the cardiac chamber and the corresponding thickness of the myocardial tissue are obtained. A function is established to determine the relationship between the signal penetration energy threshold required for the detection signal to penetrate the myocardial tissue and the ablation depth.

[0012] Based on this relationship function, multiple penetration signal energy levels are set for different ablation depths;

[0013] The ablation catheter is controlled to release detection signals of corresponding energy levels in descending order of penetration signal energy levels. The ablation depth is obtained by analyzing the detection signal with the smallest received penetration signal energy level and determining the set ablation depth.

[0014] Furthermore, the setting of multiple penetration signal energy levels for different preset ablation depths includes:

[0015] The depth sampling interval is set based on the maximum detectable ablation depth of the location of the ablation catheter within the heart chamber.

[0016] Obtain the curve showing the relationship between the attenuation of the detection signal and the ablation depth;

[0017] The relationship curve is backsampled based on the set depth sampling interval to obtain multiple depth sampling points and their corresponding signal penetration energy.

[0018] The depth sampling point is used as the set ablation depth, and the signal penetration energy of the detection signal corresponding to the depth sampling point is mapped to the penetration signal energy level corresponding to the set ablation depth.

[0019] Furthermore, the relational function is expressed as follows:

[0020]

[0021] Where E0(D) is the maximum signal penetration energy corresponding to the thickness D of myocardial tissue, E req (d,D) represents the minimum signal penetration energy corresponding to the myocardial tissue thickness D and ablation depth d, k is a parameter, and d0 is the ablation depth corresponding to the inflection point of the detection signal penetration ability decay.

[0022] Furthermore, the detection signal is represented as

[0023] s(t)=A(t)·sin(2πf c t)

[0024]

[0025] Where s(t) is the instantaneous detection signal, f c For high-frequency carrier frequency, T p Let A(t) be the duration of each envelope period, A(t) be the envelope modulation function, and A0 be the amplitude of the envelope modulation signal.

[0026] This invention also provides a method for identifying ablation regions of cardiac tissue based on catheter location, comprising the following steps:

[0027] Multiple detections are performed along the detection path using the method described above, and the ablation depth identification result and the signal phase angle of the detection signal with the smallest received penetration signal energy level are recorded for each detection.

[0028] Based on the recorded signal phase angle, it is determined whether there is an ablation area on the detection path, and then the entire ablation area is determined by combining the judgment result and the ablation depth recognition result.

[0029] Furthermore, the determination of whether an ablation region exists on the detection path based on the recorded signal phase angle is achieved by analyzing the relationship between the recorded signal phase angle and the baseline conduction phase angle to determine the path category.

[0030] Furthermore, the relationship between the recorded signal phase angle and the baseline propagation phase angle determines the path category, including:

[0031] If the recorded signal phase angle is closer to 0 than the baseline conduction phase angle, it is determined that the path crosses the ablation blockage zone.

[0032] If the recorded signal phase angle is closer to the baseline conduction phase angle, the path is determined to be located in the non-ablation stasis region.

[0033] If the recorded signal phase angle does not change significantly compared to the baseline conduction phase angle, it is determined that the path is near the edge of the ablation area or an unstable ablation area.

[0034] If no detection signal is received, it is determined that there is tissue obstruction in the path;

[0035] If no detection signal is received and it was historically detectable, then it is determined that the tissue along the path has reformed and blocked the path.

[0036] Furthermore, the baseline conduction phase angle is obtained by recording the detection signal after controlling the ablation catheter to release the highest penetration signal energy level in the non-ablation area.

[0037] The present invention also provides a cardiac tissue ablation depth recognition system based on catheter location, comprising:

[0038] The ablation catheter includes a ring-shaped body on which an even number of electrodes are evenly distributed. Any pair of electrodes with the largest spacing constitutes the transmitting end and receiving end of the detection signal, used to transmit and receive the detection signal.

[0039] The module is used to obtain the location of the ablation catheter in the heart chamber and the thickness of the myocardial tissue corresponding to that location, establish a relationship function between the signal penetration energy threshold required for the detection signal to penetrate the myocardial tissue and the ablation depth, and then set multiple penetration signal energy levels for different ablation depths based on this relationship function.

[0040] The control and analysis module is used to control the ablation catheter to release detection signals of corresponding energy levels in descending order of penetration signal energy levels, and analyze and obtain the ablation depth corresponding to the detection signal with the smallest received penetration signal energy level.

[0041] Furthermore, each pair of electrodes has a different carrier frequency, and the frequency interval between two adjacent carrier frequencies is the same set value.

[0042] Beneficial effects

[0043] Due to the adoption of the above-mentioned technical solutions, this invention has the following advantages and positive effects compared with the prior art: In this invention, after the catheter electrode emits a detection signal at a certain energy level, if the receiving electrode can detect the signal, it is considered that the ablation area has been penetrated. If the energy level is changed further but the receiving electrode cannot detect the signal, it is considered that the minimum penetration energy level has been reached. The ablation depth can be obtained by combining the penetration threshold of the minimum penetration energy level. Furthermore, by dividing the detection signal into several different energy levels, each level corresponds to a specific penetration depth range. This division is based on the inverse mapping of the response relationship between signal energy and tissue penetration ability, ensuring that the penetration depth and energy level remain linearly consistent in operation. This invention combines the myocardial thickness distribution in different parts of the heart chamber and selects a suitable energy level scanning window for the region according to the catheter position, avoiding inefficient full-scan scanning and improving detection speed and accuracy. This invention uses a high-frequency sine wave to construct the detection signal and combines envelope modulation technology to periodically generate amplitude. The signal exhibits a continuous, high-frequency, and low-interference structure, avoiding inducing myocardial tissue excitation. It can penetrate tissue without causing cardiac depolarization and has high signal recognition, making it suitable for accurately determining whether penetration has occurred in complex intracardiac backgrounds. After obtaining multiple penetrable energy levels, this invention can confirm the ablation area range based on the phase angle change of the detection signal, and further perform three-dimensional spatial and boundary reconstruction to assist in forming an ablation range model, providing visual support for accurate evaluation of ablation effects. The method described in this invention can be integrated with existing PFA ablation catheters to detect tissue ablation depth and range in real time, and improve ablation permeability by adjusting energy output through feedback, reducing recurrence after ablation of atrial fibrillation and other arrhythmias. This invention can be used in conjunction with a three-dimensional electrophysiological mapping system to dynamically evaluate the signal conduction state between electrode paths during the release of detection signals by the catheter, and provide real-time feedback on "whether the ablation is completely permeable" and "whether the blockade is continuous and closed-loop" in combination with the catheter position. Attached Figure Description

[0044] Figure 1 This is a flowchart of the first embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the conduction of electrical signals across ablated tissue according to the first embodiment of the present invention;

[0046] Figure 3 This is a graph showing the relationship between tissue ablation depth and minimum penetration energy intensity in the first embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram illustrating the detection of different ablation depths achieved by controlling energy levels according to the first embodiment of the present invention;

[0048] Figure 5 This is an example diagram illustrating the division of energy level intervals in different regions within the cardiac cavity according to the first embodiment of the present invention;

[0049] Figure 6 This is a time-domain schematic diagram of the detection signal according to the first embodiment of the present invention;

[0050] Figure 7 These are schematic diagrams of the annular pulse ablation catheter structures of the first and third embodiments of the present invention;

[0051] Figure 8 These are example diagrams illustrating the catheter movement measurement ablation range according to the first and third embodiments of the present invention;

[0052] Figure 9 This is a flowchart of the second embodiment of the present invention;

[0053] Figure 10 This is a three-dimensional contour diagram of the ablation region according to the second embodiment of the present invention. Detailed Implementation

[0054] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0055] The first embodiment of the present invention relates to a method for identifying the ablation depth of cardiac tissue based on catheter location, such as... Figure 1 As shown, it includes the following steps:

[0056] The location of the ablation catheter in the cardiac chamber and the corresponding thickness of the myocardial tissue are obtained. A function is established to determine the relationship between the signal penetration energy threshold required for the detection signal to penetrate the myocardial tissue and the ablation depth.

[0057] Based on this relationship function, multiple penetration signal energy levels are set for different ablation depths;

[0058] The ablation catheter is controlled to release detection signals of corresponding energy levels in descending order of penetration signal energy levels. The ablation depth is obtained by analyzing the detection signal with the smallest received penetration signal energy level and determining the set ablation depth.

[0059] More specifically, the energy level of the transmitted signal can be set using the following methods:

[0060] The depth sampling interval is set based on the maximum detectable ablation depth of the location of the ablation catheter within the heart chamber.

[0061] Obtain the curve showing the relationship between the attenuation of the detection signal and the ablation depth;

[0062] The relationship curve is backsampled based on the set depth sampling interval to obtain multiple depth sampling points and their corresponding signal penetration energy.

[0063] The depth sampling point is used as the set ablation depth, and the signal penetration energy of the detection signal corresponding to the depth sampling point is mapped to the penetration signal energy level corresponding to the set ablation depth.

[0064] The following section will further explain this implementation method in conjunction with the technical principles.

[0065] Normal myocardial tissue is composed of tightly packed cardiomyocytes, which form electrical channels through gap junctions, exhibiting high directionality and electrical conductivity. Signal propagation in the myocardium depends on cell membrane depolarization mechanisms and intercellular coupling states. PFA utilizes a high-voltage pulsed electric field to induce irreversible electroporation (IRE) in the myocardial cell membrane. After electroporation forms nano / micron-sized pores, ions rapidly exchange between the inside and outside of the cell, significantly reducing membrane resistance and increasing transient or permanent permeability of the cell membrane, leading to increased conductivity and decreased equivalent resistivity in myocardial tissue.

[0066] According to electromagnetic wave propagation theory and tissue electrical properties, the degree of attenuation of electrical signals by tissue is closely related to tissue conductivity. In normal myocardial tissue, the cell membrane structure is intact, and the conductivity σ normal The amplitude is low, and the electrical signal attenuates significantly during propagation. In the ablation area, the permeability of myocardial tissue cell membranes increases significantly due to the electroporation effect, leading to a decrease in tissue conductivity σ. damaged It increases significantly during the acute phase. As shown in the following formula:

[0067] σ damaged >σ normal

[0068] This increase in conductivity has a significant impact on signal propagation, manifested as a decrease in overall tissue impedance and a reduction in signal attenuation. The conduction of the electrical signal across the ablated tissue is illustrated below. Figure 2 As shown.

[0069] Assuming the total thickness of the myocardial tissue is fixed at d, under conditions without tissue ablation, the energy of the signal that can penetrate the tissue and protrude beyond the background noise to be detected by the receiving electrode is denoted as E. normal When an ablation zone of a certain thickness exists on the surface of the tissue, due to the electroporation effect in this zone, its conductivity is higher than that of the unablated tissue. This allows it to penetrate the tissue and protrude beyond the background noise. The signal energy detected by the receiving electrode is E. damaged The following relationship exists:

[0070] E normal >E damaged

[0071] As the ablation depth increases, signal propagation attenuation further decreases, and the required energy continuously decreases. Therefore, it can be deduced that there is a certain monotonically decreasing relationship between the energy threshold and the ablation depth, which can be approximated as:

[0072]

[0073] Among them, E threshold Let E0 be the initial signal amplitude, and a(x) be the signal attenuation coefficient in the tissue depth direction (determined by conductivity). As can be seen from the above relationship, with increasing ablation depth, the region of increased surface conductivity thickens, the integral value decreases, and thus the energy threshold E... threshold Monotonically decreasing. Therefore:

[0074] 1. If a high-energy signal can penetrate the tissue, it indicates that the ablation layer is thin or the tissue ablation is incomplete;

[0075] 2. If low-energy signals can penetrate tissue, it indicates that the ablation layer has a large depth and high continuity;

[0076] To measure the relationship between the energy intensity of the detection signal and the tissue penetration depth, E normal The average penetration energy of the signal at different ablation depths was measured using an animal tissue model at 100% energy intensity. If the detected signal can be captured by other electrodes, it indicates that the signal at that energy intensity can penetrate the current ablation lesion area. If the detected signal cannot be captured by other electrodes, it indicates that the signal at that energy intensity cannot penetrate the current ablation depth. The experimental results are shown in Table 1 below:

[0077] Table 1. Relationship between Penetration Signal Energy Intensity and Ablation Depth

[0078]

[0079]

[0080] The experimental results show that after the catheter electrode emits a detection signal, the effective propagation ability of the signal during tissue penetration is significantly affected by tissue conductivity, structural integrity, and the degree of damage. Particularly during PFA ablation, myocardial tissue undergoes heterogeneous damage at different depths, and tissue impedance changes exhibit a hierarchical distribution, thus affecting the penetration performance of the detection signal. This invention constructs a functional relationship model between detection signal energy and tissue ablation depth using the "minimum energy intensity required for a signal to penetrate a certain ablation depth" as the core parameter, as shown in the following equation:

[0081]

[0082] Where E(d) is the minimum energy intensity that the detection signal can penetrate when the tissue ablation depth is d, expressed as a percentage. max The energy intensity required for a signal to penetrate when the tissue is undamaged, typically 100%. min The energy intensity required for the signal to still penetrate when the tissue reaches its maximum ablation depth. max and E min It depends on the thickness of the myocardial tissue in the cardiac chamber to which the ablation area belongs. d0 is the ablation depth corresponding to the inflection point of decreased penetration ability. k is a parameter that controls the rate of decrease in energy decay, determining the steepness of the energy decay trend. This model reflects the following characteristics:

[0083] (1) When the tissue is not ablated or only superficially ablated, the tissue structure is highly continuous, has low conductivity, and the electrical signal propagation path impedance is high. A strong detection signal is required to effectively achieve penetration.

[0084] (2) As the ablation deepens, local cell membranes rupture, gap junctions break, microstructures are destroyed, tissue conductivity increases, low-resistance channels are formed, signal penetration ability is enhanced, and the required energy gradually decreases.

[0085] (3) When the transmural ablation is close to complete, the resistance retardation band is fully opened, and the signal can penetrate the tissue at a low energy. At this time, the energy required for penetration recorded by the system is the minimum.

[0086] Based on this relationship, to improve the readability and standardization of intraoperative detection results, this invention introduces a discretization and grading mechanism on the basis of the continuous functional relationship between signal energy and tissue penetration depth. This mechanism standardizes the system output into a fixed number of depth level increments, forming a quantitative, hierarchical presentation of detection results. The specific implementation method is as follows:

[0087] (1) Preset depth grading range and number of levels: The system sets the maximum range of detection depth output to d. max Based on the desired scan resolution, the penetration depth range [0, d] is determined. max The gear is evenly divided into N (N>0) gear positions, and the width of each gear position is:

[0088]

[0089] (2) Fitting function E from measured energy-depth data exp (d) Obtain the penetration energy decrease curve, and perform mean depth backsampling on the curve to obtain the actual required penetration energy E for each depth level. i E i As a benchmark for system energy level setting, a non-equally spaced energy level table is formed:

[0090]

[0091] d i = (i-0.5)·Δd

[0092] The energy level range and total number of energy levels can be calculated according to actual needs, enabling control over the detection resolution of the ablation depth. This ensures that, from the user's perspective, the detected ablation depth and the energy level of the detection signal are linearly consistent, and that the actual physical signal meets the nonlinear requirements for penetration discrimination. The tissue ablation depth d and the minimum penetration energy intensity E are also considered. i The relationship between the control energy level E and the control energy level E i Achieve the corresponding maximum detection ablation depth d i The illustration is as follows Figure 3 and Figure 4 As shown.

[0093] Based on cardiac anatomy and intraoperative measurements, the myocardial thickness D varies significantly in different locations within the cardiac chambers. Therefore, the maximum detectable ablation depth d at each location is [not specified]. max They are also different. From the perspective of organizational structure and electrophysical propagation path, they can be divided into the following cases:

[0094] (1) When the ablation depth d = 0, the myocardial thickness D affects penetration: When there is no ablation (or the ablation zone has not been penetrated), due to the intact structure of normal cells, good gap junctions, and high impedance, the signal must penetrate the intact myocardial tissue. At this time, the penetration ability of the detection signal depends entirely on the original thickness and resistivity of the tissue, and the energy required for penetration is high, which is approximately equivalent to:

[0095] E req (d=0)∝f(D)

[0096] f(D): Energy required to penetrate a thickness D of myocardial tissue

[0097] (2) When the ablation depth d>0, both myocardial thickness D and ablation depth d affect penetration: Once the ablation zone begins to form, a portion of the path is replaced by low-resistance ablated tissue. Due to the increased conductivity of the ablated tissue, the remaining "high-resistance" normal tissue thickness to be penetrated is Dd. The overall penetration capability becomes a series model of "low-resistance zone + high-resistance zone". At this time, the energy required for the detection signal to penetrate is approximately equivalent to:

[0098] E req (d)∝f1(D)+f1(Dd)

[0099] Due to E max and E min Influenced by D, the functional relationship between penetration energy and ablation depth can be written as:

[0100]

[0101] Where E0(D) is the maximum reference penetration energy corresponding to the myocardial thickness D.

[0102] In summary, when the myocardial thickness D changes, the overall upper and lower intervals of the function will shift. Therefore, when detecting the ablation depth level, the energy level interval must be dynamically generated based on the myocardial thickness D in that region before releasing the signal to detect the ablation depth. The specific implementation method is as follows:

[0103] (1) When the catheter moves to a new position, the corresponding myocardial thickness D is matched. new Update the relationship function E(d,D) between penetration depth and signal energy. new );

[0104] (2) Set the number of energy level levels N for the detection signal, and remap the energy level table {E1,E2,…,E1,E2,…,E2,…} corresponding to the actual required penetration energy for each depth. N This represents the new energy level range. Ensure that the energy level at each position corresponds to 0 to d. max The complete depth segment.

[0105] (3) Release detection signals sequentially according to the energy level intervals. Once a certain energy level E is reached... n The detected end successfully received the signal, and the next energy level E n+1 The signal cannot be received by the detection end, apparent energy level E n The minimum threshold energy level that can penetrate the current ablation depth is used to terminate subsequent energy level tests, and the penetration depth d corresponding to the current energy level is set. n This is considered the ablation depth.

[0106] Myocardial thickness information can be obtained through preoperative imaging (such as cardiac MRI and CT) or by dynamically identifying catheter position information using an intraoperative electroanatomical three-dimensional positioning system, thereby automatically adjusting the detection range. The thickness distribution of some myocardial tissues is shown in Table 2. Examples of energy level intervals for different cardiac locations and the minimum threshold energy level for penetrable ablation depth are shown below. Figure 5 As shown.

[0107] Table 2. Distribution of partial myocardial tissue thickness

[0108]

[0109] It should be noted that, Figure 3The statement "the penetration energy decrease curve is only related to the ablation depth" can be understood as "the penetration energy decrease curve is only related to the thickness of the myocardium penetrated by the ablation." The selection of the energy level interval is related to the thickness of the myocardium to be ablated; that is, the energy corresponding to the selected energy level interval must be able to penetrate the thickness of the myocardium to be ablated without causing over-ablation. For example, when ablation of 2.5±0.5 mm thick myocardial tissue is required, the energy level interval corresponding to a penetration depth of 2.5±0.5 mm is preferred, as this can obtain higher resolution ablation depth identification. Here, resolution can be understood as the difference in detection depth between two energy levels. Figure 5 As shown, the resolution varies depending on the thickness of the myocardial tissue being detected. The lower left posterior wall of the left atrium is relatively thin; selecting an energy level range of 0–2.5 mm, with 2.5 / N = 2.5 / 8 ≈ 0.3 mm, yields a resolution of 0.3 mm. However, if an energy level range of 0–5 mm is selected in this case, although it covers the thickness range of the myocardial tissue, only a resolution of 5 / 8 = 0.625 mm can be obtained.

[0110] Assuming the ablation target is 2.5 ± 0.5 mm thick myocardial tissue, the corresponding energy level range is 1.5–3.5 mm (covering the 2.5 ± 0.5 mm thick myocardial tissue), with energy level N. Figure 4 Figure 5 Example: N=8; at this time, the energy level resolution is (3.5-1.5) / 8=0.25mm. En=(3.5-1.5)*n / 8, n=1,2,3……8. If the detection end receives a signal when n=3, but does not receive a signal when n=4, it means that the current ablation depth is approximately 1.5+(3.5-1.5)*3 / 8=1.5+0.75=2.25mm, indicating ablation through the wall.

[0111] Cardiac cardiomyocytes are highly excitable to low-frequency (<1kHz) electrical signals, easily triggering action potentials, leading to rhythmic disturbances and even inducing arrhythmias. High-frequency (>10kHz) signals, however, cannot be recognized by the depolarization mechanism of the cardiomyocyte membrane, thus failing to induce electromyographic responses or cardiac excitation. Considering factors including the physiologically sensitive frequency band of the signal, the action potential threshold, the conductivity of cardiac fluid, and interference from surrounding electrodes, this invention introduces a continuous, high-frequency, low-stimulation detection signal into the detection mechanism to improve signal recognition accuracy and tissue penetration ability, while avoiding interference with the heart or inducing abnormal excitation. The mathematical expression of this signal is:

[0112] s(t)=A(t)·sin(2πf c t)

[0113]

[0114] Where s(t) is the instantaneous detection signal, f cFor high-frequency carrier frequency (f in this system) c >300kHz), T p The duration of each envelope cycle (T in this system) p =2ms), A(t) is the envelope modulation function, which controls the amplitude fluctuation within each period. An example of the time-domain detection signal is shown below. Figure 6 As shown. This signal has the following characteristics:

[0115] (1) The detection signal frequency is higher than the myocardial cell excitation response frequency band, which will not induce action potentials or interfere with cardiac electrical activity, and has high biological safety.

[0116] (2) The continuous emission of modulation amplitude is adopted, which is manifested as multiple repeated "detection cycles" in the time domain. Each cycle lasts for about 2ms. By changing the way the amplitude fluctuation of the detection signal is changed, the energy intensity of the signal release can be controlled to achieve the ability to penetrate ablation areas of different depths.

[0117] (3) In each "detection cycle", the signal amplitude changes in a way that is small at both ends and large in the middle, similar to a cosine envelope waveform. This causes the signal energy to be concentrated in the middle of the time axis. The envelope change produces a highly recognizable signal shape, which is beneficial for the receiver to perform matching and recognition and improves anti-interference performance.

[0118] (4) The signal is delivered stably and continuously throughout the detection process. It can be carried out simultaneously with catheter mapping. The operator can complete the ablation depth detection without interrupting routine operations, achieving "simultaneous detection and scanning with real-time feedback".

[0119] In some preferred embodiments, a ring-shaped pulse ablation catheter can be used. This catheter is equipped with multiple independent electrodes, each capable of both transmitting and receiving detection pulses independently. The electrodes are evenly arranged in a ring structure, with the two electrodes with the largest relative spacing forming the signal transmitting and receiving ends, totaling [number] electrode pairs. Because the absolute path length between each electrode pair covers the largest possible area of ​​myocardial tissue, it facilitates the acquisition and analysis of path signal characteristics. The catheter structure is as follows... Figure 7 As shown, electrodes 1 and 6 form a pair, electrodes 2 and 7 form a pair, electrodes 3 and 8 form a pair, electrodes 4 and 9 form a pair, and electrodes 5 and 10 form a pair.

[0120] A signal transmission path is established between each pair of electrodes to detect the tissue state within the path. As the catheter moves near the ablation area, each electrode pair simultaneously and continuously transmits and receives detection signals with independently modulated frequencies, ensuring that every potential path can be adequately measured at a given catheter position. Taking electrodes 4 and 9 as examples, the catheter movement measurement process is illustrated below. Figure 8 As shown.

[0121] Since multiple electrode pairs simultaneously transmit high-frequency detection signals, this invention employs Frequency Division Multiple Access (FDMA) technology to effectively distinguish the received signals from different electrode pairs. Through a multi-frequency carrier modulation strategy, it ensures that the detection signal spectra of different electrode pairs do not overlap, minimizing interference between signals and guaranteeing a high signal-to-noise ratio and high reception accuracy.

[0122] (1) Assign an independent carrier frequency to each electrode pair with a frequency interval of 1kHz to ensure that the signal spectrum is clearly distinguishable.

[0123] (2) The receiver accurately extracts the amplitude and phase information of the transmitted signal from each independent electrode pair through bandpass filter, digital filtering and spectrum analysis techniques;

[0124] (3) Ensure that the phase characteristics of each path can be clearly and reliably identified and recorded when the catheter moves rapidly and multiple electrode pairs are detected simultaneously.

[0125] The phase characteristics of high-frequency detection signals change significantly due to the tissue state after propagation through myocardial tissue. This principle provides a reliable basis for the discrimination in this invention. This invention designs and establishes the following phase response classification system:

[0126] (1) Conduction pathway in non-ablation area: The tissue is intact, the cell membrane is not damaged, the capacitance effect is obvious, the phase angle is negative (typically about -9° to -12°), and it is stable and consistent.

[0127] (2) Conduction path of shallow ablation area: the tissue structure is partially destroyed, the cell membrane is partially ruptured, the capacitance effect is weakened, and the absolute value of the phase angle is reduced (typically between -5° and -8°).

[0128] (3) Conduction path in the middle layer ablation area: The tissue structure is partially destroyed, the capacitance characteristics are reduced, the signal phase is close to resistive conduction, and the absolute value of the phase is small (about -3° to -4°).

[0129] (4) Conduction path in deep ablation area: The tissue structure is greatly destroyed, the capacitance characteristics are further reduced, the signal phase is close to pure resistive conduction, the absolute value of the phase is smaller (about -2° to -3°), which is significantly different from the non-ablated tissue.

[0130] (5) Transmural conduction path: The tissue structure is almost completely destroyed, and it is approximately equivalent to a pure resistor. Its impedance phase angle is almost zero and changes slowly with frequency.

[0131] Table 3 shows the phase angle records of the detection signals penetrating different ablation depths in the isolated pig heart model experiment.

[0132] Table 3. Phase angles of detection signals penetrating different ablation depths

[0133]

[0134]

[0135] A second embodiment of the present invention relates to a method for identifying ablation regions of cardiac tissue based on catheter location, comprising the following steps:

[0136] Multiple detections are performed along the detection path using the method described above, and the ablation depth identification result and the signal phase angle of the detection signal with the smallest received penetration signal energy level are recorded for each detection.

[0137] Based on the recorded signal phase angle, it is determined whether there is an ablation area on the detection path, and then the entire ablation area is determined by combining the judgment result and the ablation depth recognition result.

[0138] More specific steps are as follows Figure 9 As shown, it includes:

[0139] (1) Based on the location of the catheter in the cardiac chamber and the myocardial thickness D, the number of energy level levels N for the detection signal and the ablation depth of 0 to d are set. max The energy level table {E1, E2, ..., E} corresponding to the actual required penetration energy of the interval. N}

[0140] (2) When the catheter is located in the non-ablation area, a high-energy detection signal is released and the baseline conduction phase angle θ0 is measured and recorded.

[0141] (3) The catheter is moved to the vicinity of the area to be tested. The system periodically activates all electrode pairs, and the detection signal energy level changes sequentially to complete a complete detection scan. If the receiving electrode can detect the signal, it is considered that the ablation area has been penetrated. If the energy level continues to change but the receiving electrode cannot detect the signal, it is considered that the minimum penetration energy level has been reached. The signal phase angle θ and the ablation depth d corresponding to the minimum penetration energy level are recorded.

[0142] (4) After each detection cycle, the system classifies all detection paths to determine whether an ablation region exists on the path. Paths passing through an ablation region typically meet the following characteristics: the signal can be received, the phase angle θ is closer to 0 than the baseline propagation phase angle θ0, it is sensitive to energy changes, and the direction coverage is independent and the response is stable. This invention further proposes a "detection path response type classification system", which divides the paths into five categories, each representing its different role in ablation region identification, as shown in Table 4.

[0143] (5) Use path classification to determine the boundary of the ablation area, perform micro-movement or rotation of the catheter in the heart chamber, repeat the above measurements at different spatial positions, and then completely determine the two-dimensional or three-dimensional contour of the entire ablation area. Combine the three-dimensional navigation data to draw the three-dimensional boundary model of the ablation area in real time. Figure 10 A three-dimensional outline diagram of the ablation area is shown.

[0144] Table 4 Classification of Detection Path Response Types

[0145]

[0146]

[0147] The third embodiment of the present invention relates to a cardiac tissue ablation depth recognition system based on catheter location, used to implement the method described above, specifically including:

[0148] The ablation catheter includes a ring-shaped body on which an even number of electrodes are evenly distributed. Any pair of electrodes with the largest spacing constitutes the transmitting end and receiving end of the detection signal, used to transmit and receive the detection signal.

[0149] The module is used to obtain the location of the ablation catheter in the heart chamber and the thickness of the myocardial tissue corresponding to that location, establish a relationship function between the signal penetration energy threshold required for the detection signal to penetrate the myocardial tissue and the ablation depth, and then set multiple penetration signal energy levels for different ablation depths based on this relationship function.

[0150] The control and analysis module is used to control the ablation catheter to release detection signals of corresponding energy levels in descending order of penetration signal energy levels, and analyze and obtain the ablation depth corresponding to the detection signal with the smallest received penetration signal energy level.

[0151] More specifically, the ablation catheter is equipped with multiple independent electrodes, each capable of both transmitting and receiving detection pulses independently. The electrodes are evenly arranged in a ring structure, with the two electrodes having the largest relative spacing forming the signal transmitter and receiver, totaling [number] electrode pairs. Because the absolute path length between each electrode pair covers the largest possible area of ​​myocardial tissue, it facilitates the acquisition and analysis of path signal characteristics. The catheter structure is as follows... Figure 7 As shown, electrodes 1 and 6 form a pair, electrodes 2 and 7 form a pair, electrodes 3 and 8 form a pair, electrodes 4 and 9 form a pair, and electrodes 5 and 10 form a pair.

[0152] A signal transmission path is established between each pair of electrodes to detect the tissue state within the path. As the catheter moves near the ablation area, each electrode pair simultaneously and continuously transmits and receives detection signals with independently modulated frequencies, ensuring that every potential path can be adequately measured at a given catheter position. Taking electrodes 4 and 9 as examples, the catheter movement measurement process is illustrated below. Figure 8 As shown.

[0153] Since multiple electrode pairs simultaneously transmit high-frequency detection signals, this invention employs Frequency Division Multiple Access (FDMA) technology to effectively distinguish the received signals from different electrode pairs. Through a multi-frequency carrier modulation strategy, it ensures that the detection signal spectra of different electrode pairs do not overlap, minimizing interference between signals and guaranteeing a high signal-to-noise ratio and high reception accuracy.

[0154] (1) Assign an independent carrier frequency to each electrode pair with a frequency interval of 1kHz to ensure that the signal spectrum is clearly distinguishable.

[0155] (2) The receiver accurately extracts the amplitude and phase information of the transmitted signal from each independent electrode pair through bandpass filter, digital filtering and spectrum analysis techniques;

[0156] (3) Ensure that the phase characteristics of each path can be clearly and reliably identified and recorded when the catheter moves rapidly and multiple electrode pairs are detected simultaneously.

[0157] The phase characteristics of high-frequency detection signals change significantly due to the tissue state after propagation through myocardial tissue. This principle provides a reliable basis for the discrimination in this invention. This invention designs and establishes the following phase response classification system:

[0158] (6) Conduction pathway in non-ablation area: The tissue is intact, the cell membrane is not damaged, the capacitance effect is obvious, the phase angle is negative (typically about -9° to -12°), and it is stable and consistent.

[0159] (7) Conduction path of shallow ablation area: the tissue structure is partially destroyed, the cell membrane is partially ruptured, the capacitance effect is weakened, and the absolute value of the phase angle is reduced (typically between -5° and -8°).

[0160] (8) Conduction path in the middle layer ablation area: The tissue structure is partially destroyed, the capacitance characteristics are reduced, the signal phase is close to resistive conduction, and the absolute value of the phase is small (about -3° to -4°).

[0161] (9) Conduction path in deep ablation area: The tissue structure is greatly destroyed, the capacitance characteristics are further reduced, the signal phase is close to pure resistive conduction, the absolute value of the phase is smaller (about -2° to -3°), which is significantly different from the non-ablated tissue.

[0162] Transmural conduction path: The tissue structure is almost completely destroyed, and it is approximately equivalent to a pure resistor. Its impedance phase angle is almost zero and changes slowly with frequency.

Claims

1. A catheter position-based method of identifying the depth of cardiac tissue ablation, comprising: Includes the following steps: The location of the ablation catheter in the cardiac chamber and the corresponding thickness of the myocardial tissue are obtained. A function is established to determine the relationship between the signal penetration energy threshold required for the detection signal to penetrate the myocardial tissue and the ablation depth. Based on this relationship function, multiple penetration signal energy levels are set for different ablation depths; The ablation catheter is controlled to release detection signals of corresponding energy levels in descending order of penetration signal energy levels. The ablation depth is obtained by analyzing the detection signal with the smallest received penetration signal energy level and determining the set ablation depth.

2. The method of claim 1, wherein, The setting of multiple penetration signal energy levels for different preset ablation depths includes: The depth sampling interval is set based on the maximum detectable ablation depth of the location of the ablation catheter within the heart chamber. Obtain the curve showing the relationship between the attenuation of the detection signal and the ablation depth; The relationship curve is backsampled based on the set depth sampling interval to obtain multiple depth sampling points and their corresponding signal penetration energy. The depth sampling point is used as the set ablation depth, and the signal penetration energy of the detection signal corresponding to the depth sampling point is mapped to the penetration signal energy level corresponding to the set ablation depth.

3. The method of claim 1, wherein, The relational function is expressed as follows: wherein E0(D) is the maximum signal penetration energy corresponding to the myocardial tissue thickness D, E req (d, D) is the minimum signal penetration energy corresponding to the myocardial tissue thickness D and the ablation depth d, k is a parameter, and d0 is the ablation depth corresponding to the inflection point of the detection signal penetration capability decay.

4. The method of claim 1, wherein, The detection signal is represented as s(t) = A(t) • sin(2πf c t) Where s(t) is the instantaneous detection signal, f c is the high frequency carrier frequency, T p is the length of each envelope period, A(t) is the envelope modulation function, and A0is the envelope modulation signal amplitude.

5. A method for catheter location based identification of ablation zones in cardiac tissue, characterized in that, Includes the following steps: The method described in claims 1-4 is used to perform multiple detections along the detection path, and the ablation depth identification result of each detection and the signal phase angle of the detection signal with the smallest received penetration signal energy level are recorded. Based on the recorded signal phase angle, it is determined whether there is an ablation area on the detection path, and then the entire ablation area is determined by combining the judgment result and the ablation depth recognition result.

6. The method according to claim 5, characterized in that, The method of determining whether an ablation region exists on the detection path based on the recorded signal phase angle is achieved by analyzing the relationship between the recorded signal phase angle and the baseline conduction phase angle to determine the path category.

7. The method according to claim 6, characterized in that, The relationship between the recorded signal phase angle and the baseline propagation phase angle determines the path category, including: If the recorded signal phase angle is closer to 0 than the baseline conduction phase angle, it is determined that the path crosses the ablation blockage zone. If the recorded signal phase angle is closer to the baseline conduction phase angle, the path is determined to be located in the non-ablation stasis region. If the recorded signal phase angle does not change significantly compared to the baseline conduction phase angle, it is determined that the path is near the edge of the ablation area or an unstable ablation area. If no detection signal is received, it is determined that there is tissue obstruction in the path; If no detection signal is received and it was historically detectable, then it is determined that the tissue along the path has reformed and blocked the path.

8. The method according to claim 6, characterized in that, The baseline conduction phase angle is obtained by recording the detection signal after controlling the ablation catheter to release the highest penetration signal energy level in the non-ablation area.

9. A cardiac tissue ablation depth recognition system based on catheter location, characterized in that, include: The ablation catheter includes a ring-shaped body on which an even number of electrodes are evenly distributed. Any pair of electrodes with the largest spacing constitutes the transmitting end and receiving end of the detection signal, used to transmit and receive the detection signal. The module is used to obtain the location of the ablation catheter in the heart chamber and the thickness of the myocardial tissue corresponding to that location, establish a relationship function between the signal penetration energy threshold required for the detection signal to penetrate the myocardial tissue and the ablation depth, and then set multiple penetration signal energy levels for different ablation depths based on this relationship function. The control and analysis module is used to control the ablation catheter to release detection signals of corresponding energy levels in descending order of penetration signal energy levels, and analyze and obtain the ablation depth corresponding to the detection signal with the smallest received penetration signal energy level.

10. The system according to claim 9, characterized in that, Each pair of electrodes has a different carrier frequency, and the frequency interval between two adjacent carrier frequencies is the same set value.

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