Automatic detection of the deployment status of the catheter passing through the sheath.

Abstract

Identifying the deployment status of the distal end of a catheter delivered through a sheath. [Solution] The method includes measuring the impedance of an electrode coupled to a catheter as the electrode is delivered through the catheter's delivery sheath into the blood pool of the cardiac chamber. The steepest gradient of impedance is identified. The impedance at the steepest gradient is defined as a threshold. The user is provided with at least one of two indicators: a first indicator that the electrode is inside the sheath as long as the impedance is above the threshold, and a second indicator that the electrode is at least partially outside the sheath as long as the impedance is below the threshold.

Description

Technical Field

[0005] , ,

[0001] The present disclosure generally relates to invasive medical probes, and more particularly to identifying the deployed state of the distal end of a catheter delivered through a sheath.

Background Art

[0002] Techniques for determining the deployment of the distal end of a catheter through its delivery sheath have been previously proposed in the patent literature. For example, U.S. Patent No. 10,398,347 describes a catheter method implemented by inserting a sheath into a human patient and moving a catheter having electrodes through the sheath lumen. A change between a first threshold and a second threshold in the current passing through the electrodes is identified. In response to the change, a portion of the catheter that has transitioned between an in-sheath state and an out-of-sheath state is reported. The sheath is defined and identified by historical data of the readings during the movement of the magnetic sensor of the catheter.

[0003] A more complete understanding of the present disclosure will be obtained by reading the detailed description of the embodiments of the following disclosure in conjunction with the drawings.

Brief Description of the Drawings

[0004] [Figure 1] Schematic depiction of a catheter-based electroanatomical (EA) mapping and ablation system according to an embodiment of the present disclosure. [Figure 2] Schematic graph of the electrode impedance of a catheter as a function of the electrode position relative to the distal edge of the delivery sheath of FIG. 1 according to an embodiment of the present disclosure. And [Figure 3] Schematic flowchart showing a method and algorithm for detecting when each electrode of a catheter or the entire distal end assembly is fully contained within, emerging outside of, or fully outside of the sheath according to an embodiment of the present disclosure.

Modes for Carrying Out the Invention

[0005] overview Diagnostic and therapeutic catheters are typically delivered through a sheath. Before using the catheter for clinical work, it is desirable to identify the deployment status of the distal end assembly of the catheter through the sheath. For example, it is desirable to verify that the electrodes are emerging outside the sheath, and / or that the electrodes are completely outside the sheath, before performing electroanatomical (EA) mapping or ablation with those electrodes. It may also be desirable to verify that the catheter or the electrodes of the catheter have been completely retracted inside the sheath.

[0006] The physician manipulating the catheter may receive feedback during catheter deployment, such as visualization of the state of one or more electrodes on the catheter. For example, an electrode may be marked black on the catheter-based system's display while the electrode is inside the delivery sheath, and white while the electrode is outside the delivery sheath.

[0007] To ensure the proper clinical application of the catheter, the indication of the deployed state of the distal end assembly of the catheter through the sheath and / or the deployed state of each electrode on the distal end assembly should be robust, regardless of the type of sheath (e.g., diameter) and the type of catheter (e.g., tip, lasso, in particular).

[0008] One possible solution for evaluating the deployment state of a catheter electrode passing through a sheath is to measure the electrical impedance between the electrode and the electrode attached to the skin. The measured impedance is expected to be significantly higher while inside the sheath compared to when the sheath is fully deployed. For example, the impedance measured deep inside the sheath may be on the order of approximately 10,000 ohms, while the impedance outside the sheath may be on the order of 100 ohms. An impedance threshold may be defined to identify when the electrode emerges from the outside of the sheath, for example, to distinguish between when the electrode is deployed from the sheath and when it is retracted into the sheath. For example, the electrode impedance may be compared to a predetermined electrode impedance threshold defined during a calibration procedure and stored in memory.

[0009] However, the same catheter may be introduced through sheaths of different sizes. Similarly, catheters of different sizes may be used with the same sheath. The impedance being measured is susceptible to the sheath diameter, catheter size, and electrode size. Using a single threshold for all combinations per catheter and / or per sheath may lead to a erroneous index. A single threshold does not provide sufficient sensitivity for different combinations.

[0010] The embodiments of the present disclosure described below dynamically define an impedance threshold during a clinical procedure. The disclosed technique uses the measured impedance characteristics of one or more electrodes of a catheter to automatically identify whether each electrode (or the entire distal end assembly) is housed within or outside the sheath.

[0011] In addition to its high reliability, the disclosed technology is applicable to many types of sheaths and catheters. The method is based on analyzing the properties of the impedance curve characteristics of the electrode impedance as a function of distance from the distal edge (exit point) of the sheath. Evaluation of multiple types of catheters and sheaths revealed that the impedance curve tends to have a universal inverted S-shaped characteristic.

[0012] In one embodiment, the system circuit measures the catheter electrode impedance as the electrode is delivered (e.g., moved) into the blood pool of the cardiac chamber (e.g., as a function of electrode displacement through the delivery sheath). The physical position of the catheter is obtained using an independent tool such as magnetic position sensing or intracardiac ultrasound imaging. This step may be performed during a calibration procedure (in which the sheath and catheter are immersed in a fluid that mimics the blood pool) and / or at the start of a clinical procedure.

[0013] The system processor identifies the steepest slope of the inverse S-shaped impedance curve as a function of displacement and defines a threshold associated with the steepest slope. In one embodiment, the processor identifies the steepest slope based on detecting the minimum (or maximum) value in the derivative of the impedance curve (e.g., using the second derivative of the original curve). The threshold associated with the slope is the impedance measured at the steepest slope. The processor applies the threshold associated with the steepest slope during a clinical procedure to identify when the distal end assembly of the catheter is outside the sheath.

[0014] The catheter electrode impedance curve can be measured multiple times by the catheter as it advances and retracts (e.g., re-enters) through the delivery sheath. In one embodiment, the measurement, identification, and definition of the threshold associated with the steepest gradient may begin with that of the distal electrode. This threshold is then used to measure, identify, and define the threshold associated with the steepest gradient for the proximal electrode, and the processor proceeds to apply this threshold associated with the steepest gradient to the proximal electrode.

[0015] Each electrode may preferably have its own threshold to indicate when the electrode (or the entire distal end assembly) is fully housed within the sheath or fully outside the sheath, or a single dynamic threshold may be used for all electrodes on the catheter.

[0016] The dynamic threshold definition process may be initiated based on determining a significant change in the measured impedance. At the initiation of the process, the measured impedance may fluctuate around a certain value. The mean and standard deviation of the value may be determined based on accumulated data. A process to calculate the gradient for the purpose of identifying the steepest negative gradient may be initiated when the impedance changes significantly (e.g., decreases). The process may be initiated or updated when the processor identifies that the impedance change exceeds a threshold change, or by identifying an absolute change exceeding a given amount or a certain standard deviation (STD) based on the cumulative impedance sensed over a given period.

[0017] In another embodiment, the processor measures impedance as a function of time and searches for the steepest gradient. This method eliminates the need to explicitly consider position. In any method used herein, the steepest gradient implicitly indicates that the electrodes are located around the edge of the sheath without quantifying their relative positions.

[0018] Finally, the processor displays a virtual representation of the catheter and changes the electrode color (or another graphical coding such as a pattern) based on whether the impedance is above or below a threshold.

[0019] System Description Figure 1 is a schematic diagram of a catheter-based electroanatomical (EA) mapping and ablation system 10 according to one embodiment of the present disclosure. The system 10 includes a delivery sheath 37 (illustrated in insets 45 and 65) which is percutaneously inserted by a physician 24 through the patient's vascular system into a lumen or vascular structure of the heart 12. The physician 24 then deploys the tip catheter 14 of the system 10 into a lumen of the heart 12 (e.g., into the blood pool of the ventricle 33).

[0020] In Figure 1, physician 24 advances the distal end assembly 28, fitted onto the shaft 44 of the catheter 14, to contact the heart wall in order to sense a target site within the heart 12 or to ablate wall tissue. The assembly 28 has a longitudinal axis 42 parallel to the distal end of the shaft 44. The terms “proximal” and “distal” are defined with respect to their position on the axis.

[0021] As seen in inset 65, the tip assembly 28 includes a tip electrode 16 and ring electrodes 26 and 36. Electrode 16 may sense a unipolar EA signal or may be used for radio frequency (RF) ablation. Electrodes 16, 26, and 36 may be used to sense a bipolar EA signal, for electrical position tracking of the tip assembly 28, and for pulsed field ablation (PFA).

[0022] The system 10 further includes one or more electrode patches 38 positioned for skin contact on the patient 23, enabling the sensing of (i) a unipolar EA signal (e.g., between any of electrodes 16, 26, and 36 and a common electrode realized by one or more patches 38), and (ii) impedance in electrodes 16, 26, and 36, e.g., impedance between electrodes 16, 26, and 36 and one or more electrode patches 38.

[0023] The recorder 11 displays the electrophoresis diagram 21 captured by the surface ECG electrode 18 and the EA signals captured by the electrodes 16, 26, and 36 of the catheter 14.

[0024] System 10 may include an ablation energy generator 50 adapted to conduct ablation energy to an electrode 16 in a distal assembly 28 of a catheter 14 configured for electroablation. The energy generated by ablation energy generator 50 may include radiofrequency (RF) energy or pulsed-field ablation (PFA) energy, or a combination thereof, including unipolar or bipolar high voltage DC pulses (or combinations thereof) that can be used to effect irreversible electroporation (IRE), but is not limited thereto.

[0025] A patient interface unit (PIU) 30 is configured to establish electrical communication between the catheter 14, an electrophysiology device, a power source, and a workstation 55 for controlling the operation of system 10. The electrophysiology device of system 10 may include, for example, other catheters, location pads 25, body surface ECG electrodes 18, electrode patches 38, ablation energy generator 50, and recorder 11. Optionally and preferably, PIU 30 additionally includes processing capabilities for performing real-time calculations of catheter position and for performing ECG calculations.

[0026] The workstation 55 includes a memory 57, a processor 56 having a memory or storage device in which appropriate operating software is stored, and user interface functions. The workstation 55 may optionally (i) render to model the endocardial anatomical structure in three dimensions (3D) and display a model or anatomical map 20 on a display device 27; (ii) display on the display device 27 a representative visual display or image of an activation sequence (or other data) compiled from the recorded electrogram 21 superimposed on the rendered anatomical map 20; (iii) display the real-time positions and orientations of a plurality of catheters within the heart chamber; and (iv) display on the display device 27 regions of interest such as the locations where ablation energy has been applied, and may provide a plurality of functions. One commercially available product embodying the elements of the system 10 is available as the CARTO (trademark) 3 system, available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA, 92618.

[0027] Although FIG. 1 illustrates a tip catheter, the following description applies to other catheter types such as loop, multi-arm, and basket multi-electrode self-expanding catheters having one or more ring electrodes, such as electrodes 26 and 36, mounted on the distal end portion of the catheter shaft (i.e., in the proximal direction of the self-expanding assembly).

[0028] Automatic detection of sheath type Figure 2 is a schematic graph of the electrode impedance of a catheter as a function of the electrode position relative to the distal edge of the sheath 37 in Figure 1, according to one embodiment of the present disclosure. The schematic graph applies to any of electrodes 16, 26, and 36, however, the actual values ​​may vary between electrodes. This graph applies to different catheter and sheath types, however, the actual values ​​may vary between catheters and sheaths. As described above, the impedance of an electrode is measured between that electrode and a suitable reference electrode. For example, in Figure 1, electrode patch 38 may serve as a reference electrode for such impedance measurement.

[0029] As shown in Figure 2, the electrode impedance decreases along an inverted S-shaped characteristic curve from a value of 202 inside the sheath to a value of 208 outside the sheath. The impedance changes significantly in one of the regions 209 and 219 of the impedance curve. Significant changes can be quantified as greater than a given amount or as several standard deviations (STD). Although the values ​​202 and 208 may vary as described above, the inverted S-shape remains robust nonetheless.

[0030] In particular, the steepest gradient of the inverted S-shaped curve, 207, occurs near the midpoint between values ​​202 and 208.

[0031] Using the disclosed algorithm, the processor 56 identifies the maximum gradient 207 of the impedance of one or more of the electrodes 16, 26, and 36. The processor 56 defines a threshold associated with the steepest gradient as the impedance 206 measured at the steepest gradient.

[0032] The definitions for values ​​206 and / or 207 are robust enough to enable automatic detection of whether each electrode or the entire distal end assembly of the catheter is housed within or outside the sheath. Optionally, automatic detection may also distinguish, for many types of catheters and sheaths, whether fully housed within the sheath, exposed outside the sheath, or completely outside the sheath.

[0033] Automatic detection method for catheter electrode position for any sheath type Figure 3 is a schematic flowchart illustrating a method and algorithm for detecting when each electrode (16, 26, 36) of the catheter 14 or the entire distal end assembly 28 emerges from the delivery sheath 37, according to one embodiment of the present disclosure. Optionally, a default threshold is stored in memory and applied until an updated threshold is determined. The algorithm according to this embodiment performs a process beginning with a signal measurement step 302, in which the circuitry of the interface 30 measures the signal (e.g., impedance) of one or more of the electrodes 16, 26, and 36 of the assembly 28 as it is displaced (e.g., advanced or retracted) through the sheath 37 inside the blood pool of the atrium or ventricle 33. This step is performed prior to the diagnostic / treatment step of the clinical procedure.

[0034] In threshold setting initiation step 304, the threshold setting process is initiated or updated when the processor identifies a significant change in impedance. A significant change may be defined as a predetermined absolute change, or as a change exceeding a specified number of standard deviations (STDs) of the measurements detected while the catheter is in one of the regions 209 and 219 of the impedance curve.

[0035] In identification step 306, the processor 56 identifies the steepest negative impedance slope 207 associated with one or more of the electrodes 16, 26, and 36 that are emerging outside the sheath, as shown in Figure 2. In addition, the processor 56 may also identify the steepest positive impedance slope, e.g., slope 207, associated with one or more electrodes that are retracting into the sheath. This identification may begin after detecting that one or more electrodes are already outside the sheath.

[0036] In impedance estimation step 308, processor 56 estimates the impedance value 206 with the steepest negative gradient 207. Processor 56 stores the impedance value 206 as the threshold recorded with the steepest gradient. This definition is performed for one or more electrodes 16, 26, 36. Typically, this process is applied to at least the proximal electrode 36.

[0037] During the clinical procedure, in threshold application step 310, the processor 56 provides the user with at least one of the following: a first indicator that the electrode is inside the sheath 37 if the impedance is greater than the threshold 205, and a second indicator that the electrode is at least partially outside (e.g., exposed) the sheath 37 if the impedance is lower than the threshold 206.

[0038] The processor 56 uses a threshold associated with the steepest gradient, preferably the threshold of the proximal electrode 36, to check the position of the distal end assembly 28 relative to the sheath 37, for example, to confirm that the distal end assembly 28 is outside the sheath or completely outside the sheath 37.

[0039] The illustrative flowchart shown in Figure 3 is simplified for clarity of concept. Additional steps, such as multiple advances and retreats of the catheter to obtain multiple measurements, may also be applied. Alternatively, the thresholding process may be initiated or updated when the processor identifies that the impedance has changed beyond a given amount or several standard deviations (STD). For example, thresholding may be initiated when the impedance passes through the shaded area in Figure 2, indicating either an increase in exposure to the external environment, e.g., the left shaded area 209, or a decrease in exposure to the external environment, e.g., the right shaded area 219. [Examples]

[0040] (Example 1) The method includes measuring the impedance (302) of electrodes (16, 26, 36) coupled to a catheter (14) as the electrodes are delivered into the blood pool of a cardiac chamber (33) through the catheter's delivery sheath (37). The steepest gradient of impedance (207) is identified. The impedance at the steepest gradient is defined as a threshold (206). The user is provided with at least one of two indicators: a first indicator that the electrodes (16, 26, 36) are inside the sheath (37) as long as the impedance is above the threshold (206), and a second indicator that the electrodes (16, 26, 36) are at least partially outside the sheath (37) as long as the impedance is below the threshold (206).

[0041] (Example 2) A method according to Example 1, wherein providing an indicator to the user includes displaying a virtual representation of the catheter and changing the color of electrodes (16, 26, 36) based on whether the impedance is above or below the threshold (206).

[0042] (Example 3) A method according to either of Examples 1 and 2, wherein measuring the impedance of electrodes (16, 26, 36) as the electrodes are delivered through a delivery sheath (37) comprises measuring the impedance as a function of the displacement of the electrodes through the delivery sheath.

[0043] (Example 4) A method according to any one of Examples 1 to 3, wherein measuring the impedance of electrodes (16, 26, 36) comprises measuring the impedance of two or more electrodes individually and defining a threshold impedance (206) for each electrode.

[0044] (Example 5) A method according to any one of Examples 1 to 3, wherein measuring the impedance of electrodes (16, 26, 36) comprises measuring the impedance of two or more electrodes individually and defining a single threshold impedance (206) for a plurality of electrodes (16, 26, 36).

[0045] (Example 6) A method according to any one of Examples 1 to 5, comprising initiating a threshold (206) setting process or updating a threshold when identifying a predetermined change (209, 219) in impedance compared to an average impedance measured over a defined period.

[0046] (Example 7) A method according to any one of Examples 1 to 6, wherein a predetermined change (209, 219) is defined as a predetermined number of STDs, where STDs are defined based on impedances measured over a defined period.

[0047] (Example 8) A method according to any one of Examples 1 to 7, comprising updating a threshold (206) based on the detection of re-entry of electrodes (16, 26, 36) into the sheath (37).

[0048] (Example 9) A method according to any one of Examples 1 to 8, comprising identifying that the distal end assembly (28) of the catheter (14) is outside the delivery sheath (37) by identifying that all electrodes (16, 26, 36) of the catheter are outside the delivery sheath, by applying a threshold (206) related to the steepest slope (207).

[0049] (Example 10) The method described in any one of Examples 1 to 9, and Measuring impedance, identifying the steepest slope (207), and defining thresholds related to the steepest slope for the distal electrodes (16, 26), Using a threshold associated with the steepest slope for the distal electrodes (16, 26), measuring impedance, identifying the steepest slope, and defining a threshold associated with the steepest slope for the proximal electrode (36), A method comprising applying a threshold (206) related to the steepest gradient defined for the proximal electrode (36) during a clinical procedure.

[0050] (Example 11) A method according to any one of Examples 1 to 10, comprising measuring displacement using magnetic position detection (25) and intracardiac ultrasound imaging.

[0051] (Example 12) A method according to any one of Examples 1 to 11, comprising tracking the position of the sheath (37) and determining the position of the distal end (28) of the catheter relative to the edge of the sheath (37).

[0052] (Example 13) The system (10) includes an interface (30) and a processor (56). The interface is configured to measure the impedance of electrodes (16, 26, 36) coupled to a catheter (14) as the electrodes are delivered into the blood pool of the cardiac chamber (33) through the catheter's delivery sheath (37). The processor is configured to (i) identify the steepest gradient (207) of the impedance, (ii) define the impedance at the steepest gradient as a threshold (206), and (iii) provide the user with at least one of a first indicator that the electrodes (16, 26, 36) are inside the sheath (37) as long as the impedance is above the threshold (206), and a second indicator that the electrodes (16, 26, 36) are at least partially outside the sheath (37) as long as the impedance is below the threshold (206).

[0053] While the examples described herein primarily address cardiac diagnostic applications, the methods and systems described herein may also be used for other medical applications.

[0054] The embodiments described above are illustrative examples, and it will be understood that this disclosure is not limited to those specifically illustrated and described above. Rather, the scope of this disclosure includes both combinations and partial combinations of the various functions described above, as well as variations and modifications thereof that a person skilled in the art would conceive of from reading the foregoing description and that are not disclosed in the prior art.

[0055] [Implementation Method] (1) A method, The impedance of an electrode connected to a catheter is measured as the electrode is delivered into the blood pool of the cardiac chamber through the delivery sheath of the catheter. Identifying the steepest slope of the aforementioned impedance, The impedance at the steepest gradient is defined as the threshold, A method comprising providing a user with at least one of a first indicator that the electrode is inside the sheath, as long as the impedance is above the threshold, and a second indicator that the electrode is at least partially outside the sheath, as long as the impedance is below the threshold. (2) The method according to Embodiment 1, wherein providing the indicator to the user includes displaying a virtual representation of the catheter and changing the color of the electrode based on whether the impedance is above or below the threshold. (3) The method according to Embodiment 1, wherein measuring the impedance of the electrode as it is delivered through the delivery sheath includes measuring the impedance as a function of the displacement of the electrode through the delivery sheath. (4) The method according to Embodiment 1, wherein measuring the impedance of the electrode includes measuring the impedance of two or more electrodes individually and defining a threshold impedance for each electrode. (5) The method according to Embodiment 1, wherein measuring the impedance of the electrodes includes measuring the impedance of two or more electrodes individually and defining a single threshold impedance for a plurality of electrodes.

[0056] (6) The method according to Embodiment 1, which includes initiating a threshold setting process or updating the threshold when identifying a predetermined change in impedance compared to an average impedance measured over a defined period. (7) The method according to Embodiment 6, wherein the predetermined change is defined as a predetermined number of STDs, and the STDs are defined based on the impedance measured over the defined period. (8) The method according to Embodiment 1, comprising updating the threshold based on the detection of the re-entry of the electrode into the sheath. (9) The method according to Embodiment 1, wherein applying the threshold associated with the steepest gradient identifies that all electrodes of the catheter are outside the delivery sheath, thereby identifying that the distal end assembly of the catheter is outside the delivery sheath. (10) Measuring the impedance, identifying the steepest slope, and defining a threshold related to the steepest slope for the distal electrode, Using a threshold related to the steepest gradient for the distal electrode, measuring the impedance, identifying the steepest gradient, and defining a threshold related to the steepest gradient for the proximal electrode, The method according to Embodiment 1, comprising applying a threshold related to the steepest gradient defined for the proximal electrode during a clinical procedure.

[0057] (11) The method according to Embodiment 1, comprising measuring the displacement using one of magnetic position detection and intracardiac ultrasound imaging. (12) The method according to Embodiment 1, comprising tracking the position of the sheath and determining the position of the distal end of the catheter relative to the edge of the sheath. (13) A system, An interface configured to measure the impedance of an electrode coupled to a catheter as the electrode is delivered into the blood pool of the cardiac chamber through the catheter's delivery sheath, It is a processor, Identifying the steepest slope of the aforementioned impedance, The impedance at the steepest gradient is defined as the threshold, A system comprising a processor configured to provide a user with at least one of the following: a first indicator that the electrode is inside the sheath, as long as the impedance is above the threshold; and a second indicator that the electrode is at least partially outside the sheath, as long as the impedance is below the threshold. (14) The system according to embodiment 13, wherein the processor is configured to provide the indicator to the user by displaying a virtual representation of the catheter and by changing the color of the electrode based on whether the impedance is above or below the threshold. (15) The system according to embodiment 13, wherein the interface is configured to measure the impedance of the electrode as the electrode is delivered through the delivery sheath by measuring the impedance as a function of the displacement of the electrode through the delivery sheath.

[0058] (16) The system according to embodiment 13, wherein the interface is configured to measure the impedance of the electrodes by measuring the impedance of two or more electrodes individually and defining a threshold impedance for each electrode. (17) The system according to Embodiment 13, wherein the interface is configured to measure the impedance of electrodes by measuring the impedance of two or more electrodes individually and by defining a single threshold impedance for a plurality of electrodes. (18) The system according to Embodiment 13, wherein the processor is further configured to initiate a threshold setting process or update the threshold when it identifies a predetermined change in impedance compared to an average impedance measured over a defined period of time. (19) The system according to Embodiment 18, wherein the predetermined change is defined as a predetermined number of STDs, and the STDs are defined based on the impedance measured over the defined period. (20) The system according to embodiment 13, wherein the processor is further configured to update the threshold based on detection of re-entry of the electrode into the sheath.

[0059] (21) The system according to Embodiment 13, wherein the processor is configured to apply the threshold associated with the steepest gradient by identifying that all electrodes of the catheter are outside the delivery sheath, or by identifying that the distal end assembly of the catheter is outside the delivery sheath. (22) The processor Identifying the steepest gradient and defining a threshold related to the steepest gradient for the distal electrode, Identifying the steepest gradient using a threshold related to the steepest gradient for the distal electrode, and defining a threshold related to the steepest gradient for the proximal electrode, The system according to Embodiment 1, further configured to apply a threshold related to the steepest gradient defined for the proximal electrode during a clinical procedure. (23) The system according to embodiment 13, wherein the processor is further configured to measure the displacement using one of magnetic position detection and intracardiac ultrasound imaging. (24) The system according to embodiment 13, wherein the processor is further configured to track the position of the sheath and to determine the position of the distal end of the catheter relative to the edge of the sheath.

Claims

1. It is a system, An interface configured to measure the impedance of an electrode coupled to a catheter as the electrode is delivered into the blood pool of the cardiac chamber through the catheter's delivery sheath, It is a processor, Identifying the steepest slope of the aforementioned impedance, The impedance at the steepest gradient is defined as the threshold, A system comprising a processor configured to provide a user with at least one of the following: a first indicator that the electrode is inside the sheath, as long as the impedance is above the threshold; and a second indicator that the electrode is at least partially outside the sheath, as long as the impedance is below the threshold.

2. The system according to claim 1, wherein the processor is configured to provide the indicator to the user by displaying a virtual representation of the catheter and changing the color of the electrode based on whether the impedance is above or below the threshold.

3. The system according to claim 1, wherein the interface is configured to measure the impedance of the electrode as the electrode is delivered through the delivery sheath, by measuring the impedance as a function of the displacement of the electrode through the delivery sheath.

4. The system according to claim 1, wherein the interface is configured to measure the impedance of the electrodes by individually measuring the impedance of two or more electrodes and defining a threshold impedance for each electrode.

5. The system according to claim 1, wherein the interface is configured to measure the impedance of electrodes by individually measuring the impedance of two or more electrodes and by defining a single threshold impedance for a plurality of electrodes.

6. The system according to claim 1, wherein the processor is further configured to initiate a threshold setting process or update the threshold when it identifies a predetermined change in impedance compared to an average impedance measured over a defined period of time.

7. The system according to claim 6, wherein the predetermined change is defined as a predetermined number of STDs, and the STDs are defined based on the impedance measured over the defined period.

8. The system according to claim 1, wherein the processor is further configured to update the threshold based on detection of re-entry of the electrode into the sheath.

9. The system according to claim 1, wherein the processor is configured to apply the threshold associated with the steepest gradient by identifying that all electrodes of the catheter are outside the delivery sheath, or by identifying that the distal end assembly of the catheter is outside the delivery sheath.

10. The aforementioned processor, Identifying the steepest gradient and defining a threshold related to the steepest gradient for the distal electrode, Identifying the steepest gradient using a threshold related to the steepest gradient for the distal electrode, and defining a threshold related to the steepest gradient for the proximal electrode, The system according to claim 1, further configured to apply a threshold related to the steepest gradient defined for the proximal electrode during a clinical procedure.

11. The system according to claim 1, wherein the processor is further configured to measure the displacement using one of magnetic position detection and intracardiac ultrasound imaging.

12. The system according to claim 1, wherein the processor is further configured to track the position of the sheath and to determine the position of the distal end of the catheter relative to the edge of the sheath.

13. It is a method, The impedance of an electrode connected to a catheter is measured as the electrode is delivered into the blood pool of the cardiac chamber through the delivery sheath of the catheter. Identifying the steepest slope of the aforementioned impedance, The impedance at the steepest gradient is defined as the threshold, A method comprising providing a user with at least one of a first indicator that the electrode is inside the sheath as long as the impedance is above the threshold, and a second indicator that the electrode is at least partially outside the sheath as long as the impedance is below the threshold.

14. The method according to claim 13, wherein providing the indicator to the user includes displaying a virtual representation of the catheter and changing the color of the electrode based on whether the impedance is above or below the threshold.

15. The method according to claim 13, wherein measuring the impedance of the electrode as it is delivered through the delivery sheath includes measuring the impedance as a function of the displacement of the electrode through the delivery sheath.

16. The method according to claim 13, wherein measuring the impedance of the electrode includes measuring the impedance of two or more electrodes individually and defining a threshold impedance for each electrode.

17. The method according to claim 13, wherein measuring the impedance of the electrodes includes measuring the impedance of two or more electrodes individually and defining a single threshold impedance for a plurality of electrodes.

18. The method according to claim 13, comprising initiating a threshold setting process or updating the threshold when identifying a predetermined change in impedance compared to an average impedance measured over a defined period.

19. The method according to claim 18, wherein the predetermined change is defined as a predetermined number of STDs, and the STDs are defined based on the impedance measured over the defined period.

20. The method according to claim 13, comprising updating the threshold based on the detection of re-entry of the electrode into the sheath.

21. The method of claim 13, wherein applying the threshold associated with the steepest gradient identifies that the distal end assembly of the catheter is outside the delivery sheath by identifying that all electrodes of the catheter are outside the delivery sheath.

22. Measuring the impedance, identifying the steepest gradient, and defining a threshold related to the steepest gradient for the distal electrode, Using a threshold related to the steepest gradient for the distal electrode, measuring the impedance, identifying the steepest gradient, and defining a threshold related to the steepest gradient for the proximal electrode, The method according to claim 13, comprising applying a threshold related to the steepest gradient defined for the proximal electrode during a clinical procedure.

23. The method according to claim 13, comprising measuring the displacement using one of magnetic position detection and intracardiac ultrasound imaging.

24. The method according to claim 13, comprising tracking the position of the sheath and determining the position of the distal end of the catheter relative to the edge of the sheath.

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