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CN-122005052-A - Tissue proximity index threshold for cardiac ablation

CN122005052ACN 122005052 ACN122005052 ACN 122005052ACN-122005052-A

Abstract

In one exemplary mode, an apparatus includes a catheter including electrodes providing an Intracardiac Electrogram (IEGM) signal and a signal for sensing impedance, an ablation energy generator configured to conduct ablation energy to the electrodes of the catheter based on user input, a controller configured to sample the IEGM signal from the electrodes before and after a given ablation and to sense the impedance between the electrodes and tissue, and a processor configured to compare the sensed impedance to a TPI threshold to determine a contact state of the electrodes relative to the tissue, to present an indication of the determined contact state to a display, to calculate a change in the IEGM signal due to the given ablation, and to adjust the TPI threshold for subsequent ablations based on the calculated change in the IEGM signal due to the given ablation of the tissue with the electrodes.

Inventors

  • 5. Greiner
  • A. Gowali

Assignees

  • 伯恩森斯韦伯斯特(以色列)有限责任公司

Dates

Publication Date
20260512
Application Date
20251107
Priority Date
20241111

Claims (10)

  1. 1. An apparatus, comprising: a catheter (14) comprising an electrode (26) providing an Intracardiac Electrogram (IEGM) signal and a signal for sensing impedance; an ablation energy generator (50) configured to conduct ablation energy to the electrode (26) of the catheter (14) based on user input; A controller (30) configured to: Sampling the IEGM signal from the electrode (26) before and after a given ablation, and Sensing impedance between the electrode (26) and tissue (80), and A processor (56) configured to: Comparing the sensed impedance to a Tissue Proximity Index (TPI) threshold to determine a contact state of the electrode (26) relative to the tissue (80); presenting an indication of the determined contact state to a display (27); Calculating a change in the IEGM signal due to the given ablation, and The TPI threshold for subsequent ablations is adjusted based on the calculated change in the IEGM signal due to the given ablation of the tissue (80) with the electrode (26).
  2. 2. The device of claim 1, wherein the processor (56) is configured to iteratively adjust the TPI threshold based on the respective previous TPI threshold and the respective decrease in voltage of the IEGM signal due to ablation at the respective ablation site.
  3. 3. The device of claim 1, wherein the processor (56) is configured to: Checking the movement stability of the electrode (26) during ablation, and The TPI threshold is adjusted based on the movement stability of the electrode (26) being within a given limit.
  4. 4. The apparatus of claim 1, wherein the processor (56) is configured to reduce the TPI threshold based on observing at least a given reduction in the IEGM signal due to ablating the tissue (80) with the electrode (26).
  5. 5. The device of claim 1, wherein the processor (56) is configured to increase the TPI threshold based on observing less than a given decrease in the IEGM signal due to ablating the tissue (80) with the electrode (26).
  6. 6. The device of claim 1, wherein the processor (56) is configured to receive user input to determine a threshold adjustment factor.
  7. 7. The device of claim 1, wherein the processor (56) is configured to: Identifying minimum and maximum impedances and corresponding minimum and maximum TPI limits, and An estimated TPI threshold is defined as a function between and based on the minimum and maximum TPI limits.
  8. 8. The apparatus of claim 1, wherein the processor (56) is configured to adjust the TPI threshold for each electrode (26) of the catheter (14).
  9. 9. The apparatus of claim 1, wherein the processor (56) is configured to adjust the TPI threshold such that the same TPI threshold is maintained for a plurality of electrodes (26) of the catheter (14).
  10. 10. The device of any one of claims 1 to 9, wherein the processor (56) is configured to calculate a new TPI threshold based on a decrease in voltage of the IEGM signal minus a second factor multiplied by a first factor subtracted from a previous TPI threshold.

Description

Tissue proximity index threshold for cardiac ablation Technical Field The present disclosure relates to ablation with therapeutic endocardial catheters, and in particular, but not limited to, tissue proximity indication during cardiac ablation. Background A wide range of medical procedures involve the placement of a probe, such as a catheter, within a patient. One medical procedure for which these types of probes or catheters have proven to be very useful is the treatment of cardiac arrhythmias. Arrhythmia, particularly atrial fibrillation, has been a common and dangerous medical condition, particularly in the elderly population. Diagnosis and treatment of cardiac arrhythmias includes mapping electrical characteristics of cardiac tissue, particularly endocardium and cardiac volume, and selectively ablating the cardiac tissue by applying energy. In such procedures, a catheter is inserted into and optionally around the heart chamber. In most procedures, multiple catheters are inserted into a patient. The catheters may include mapping catheters, ablation catheters, temperature sensing catheters, and image sensing catheters. Some catheters are dedicated for placement in specific parts of the anatomy, such as the coronary sinus, esophagus, atrium, ventricle. The catheters have multiple electrical channels, with some catheters having more channels than others, depending on the number of sensors and electrodes included in each catheter. The number and type of catheters depends on the procedure and the workflow preferred by the physician. A typical ablation procedure involves inserting a catheter having one or more electrodes at its distal end into the ventricle. RF (radio frequency) current (or pulsed electric field ablation (PFA) energy) is applied through the tip electrode of the ablation catheter and the current flows through the medium surrounding the tip electrode, i.e., the blood and tissue between the tip electrode and the indifferent electrode. The distribution of the current depends on the amount of electrode surface in contact with the tissue compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to the electrical resistance of the tissue. The tissue is heated sufficiently to cause cell destruction in the heart tissue, resulting in the formation of non-conductive lesions within the heart tissue. Thus, when placing an ablation catheter or other catheter in the body (particularly near endocardial tissue), it is desirable that the catheter ablation electrode directly contact the tissue. Electrode-tissue contact may be measured based on the impedance between the electrode on the distal end of the catheter and the return electrode. Drawings The disclosure will be understood from the following detailed description taken in conjunction with the accompanying drawings in which: FIG. 1 is a simplified illustration of a catheter-based electrophysiology mapping and ablation system constructed and operative in accordance with an example of the present disclosure; FIG. 2 is a more detailed isometric view of an expandable distal end assembly for a catheter of the system of FIG. 1; FIG. 3 is a simplified qualitative illustration showing impedance measured by electrodes in a body lumen as a function of proximity of the electrodes to wall tissue for use in the system of FIG. 1, and Fig. 4A and 4B are flowcharts including steps in a method for adjusting a tissue proximity index threshold for use in the system of fig. 1. Detailed Description SUMMARY As previously described, contact between an electrode and tissue may be measured based on impedance between the electrode and tissue. The quality of contact between the electrode and the tissue may be expressed as a Tissue Proximity Index (TPI). For example, the TPI threshold for a particular patient may be used to determine whether the electrode is in sufficient contact with tissue to provide successful ablation. From a physician's perspective, it is often important to consider whether the cardiac signal at the ablation site is sufficiently attenuated by ablation for adequate contact of the electrode with the tissue. If the cardiac signal at the tissue is sufficiently attenuated by ablation, the electrode is then in sufficient contact with the tissue during ablation. The TPI threshold may be selected and define whether a given impedance value indicates a contact sufficient to sufficiently attenuate cardiac signals. For example, if the sensed impedance is greater than a threshold TPI, the sensed impedance indicates that the electrode is in sufficient contact with the tissue to successfully ablate the tissue, and if the sensed impedance is not greater than the TPI threshold, the sensed impedance indicates that the electrode is not in sufficient contact with the tissue. It is therefore important that the TPI threshold be carefully selected so that it indicates the contact quality required to achieve successful ablation (e.g., the desir