Provision of blood pool direction vector based on measured impedance

Abstract

To improve electroanatomical (EA) mapping of a heart.SOLUTION: A method includes monitoring impedances of multiple functional electrodes relative to a reference electrode while maneuvering a catheter within a cavity of an organ, the catheter comprising (i) a shaft having a distal end, and (ii) an expandable distal-end assembly coupled to the distal end of the shaft and comprising the multiple functional electrodes. A direction vector is estimated from the monitored impedances, along which the catheter is free to advance within the cavity of the organ without obstruction by a tissue wall. The direction vector is displayed to a user.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates generally to anatomical mapping, and more specifically to improvements in electroanatomical (EA) mapping of the heart.

Background Art

[0002] Techniques exist in the patent literature for assisting in guiding an EA mapping catheter within a heart chamber to obtain clinically relevant data for constructing an EA map of the heart chamber. Such techniques may involve medical imaging methods such as fluoroscopy to assist a physician in navigating the catheter to a target area within the heart. Typically, it is desirable to minimize the use of fluoroscopy to avoid exposing the patient and medical staff to harmful radiation. Manipulating a catheter within a heart chamber to reach a target area is highly beneficial in heart treatment planning and the treatment itself, but it requires a high level of expertise on the part of the physician performing the procedure.

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

Brief Description of the Drawings

[0004]

Figure 1

Figure 2

Figure 3

Figure 4

[0005] Overview The wall tissue of the cardiac chamber can be electroanatomically (EA) mapped using a catheter having a plurality of functional electrodes attached to an expandable distal end assembly of the catheter. During a mapping procedure within the cardiac chamber, a physician can manipulate the expanded distal end assembly to contact the electrodes with the cardiac chamber wall and acquire and / or apply electrical signals. The final EA map can include many anatomical details that are important for facilitating treatment planning, such as, in the case of the left atrium, the four pulmonary vein (PV) orifices, and the left lower pulmonary vein, etc.

[0006] However, at the initial stage of the mapping procedure, physicians often do not have information on where to direct the catheter to achieve efficient mapping. Only after a portion of the cardiac chamber surface has been mapped can the physician make the mapping more efficient by accessing clinically relevant but difficult-to-access locations within the cardiac chamber, such as the cardiac ostium, auricles, and valves, in a beneficial way. Even at later stages, it is often difficult to understand how to operate within the three-dimensional structure of the cardiac chamber. These difficult problems at the initial stage of EA mapping can prolong the mapping procedure and make the mapping procedure more medically complex for the patient. In some examples, a physician may wish to reach the treatment area with minimal mapping performed during a treatment procedure using a therapeutic catheter.

[0007] Examples of the present disclosure described herein provide techniques that facilitate the initial stage of EA mapping by solving or avoiding the above-described difficulties in efficiently mapping an unknown surface using a catheter.

[0008] In one example of this technique, a physician operates an expanded distal end assembly of a catheter within a heart chamber. The catheter comprises a distal end assembly having a plurality of functional electrodes, such as a basket assembly or a balloon assembly having a plurality of electrodes thereon. While the catheter is being operated, a processor monitors the impedance of the plurality of functional electrodes relative to a reference electrode. Using the monitored impedance, the processor estimates a blood pool direction vector, and along this blood pool direction vector, the catheter freely advances within the heart chamber. The processor displays the direction vector to the user as respective blood direction arrows.

[0009] As described above, the disclosed technique can overcome the difficulty of efficiently mapping an initially unknown tissue surface using a catheter. For example, as seen in FIG. 3, the disclosed technique shows the best approach to landmarks such as the pulmonary vein (PV) ostium, the left atrial appendage (LAA), etc. when the blood pool direction is aligned with the catheter shaft (e.g., by indicating that the direction arrow is aligned with the longitudinal axis icon of the virtual representation of the distal end assembly).

[0010] This method is applied to the heart chamber, but can be applied to another chamber of the organ by measuring the chamber volume and wall impedance.

[0011] To estimate the blood pool direction vector, in some examples, the processor first identifies the maximum and minimum impedance of the patient and normalizes the impedance range between the maximum and minimum impedance. In addition to variability between patients, the maximum and minimum values detected for each functional electrode depend on the distance between the functional electrode and the reference electrode. These differences may be considered, and a normalized range, such as 0 to 1, may be defined for each of the electrodes based on the identified maximum and minimum impedance.

[0012] In some examples, to estimate the blood pool direction vector, the processor relies on the known geometric shape of the extended distal assembly. In some examples, the center point of the internal space is calculated and vectors extending from the center point to each of the electrodes are defined. In some exemplary embodiments, deformation of the distal assembly is tracked and the center point of the internal space is dynamically defined based on the tracked deformation.

[0013] The magnitude of each vector is defined as a scaled value of the impedance sensed at the electrode. Typically, the impedance increases as the electrode approaches the tissue. Since it is desirable to indicate the direction away from the tissue and the impedance decreases as a function of the distance from the tissue, the magnitude of each vector can be defined as the maximum impedance level minus the instantaneous impedance level at that moment. For example, for a range of impedance values normalized to be between 0 and 1, the magnitude of each vector can be 1 minus the normalized impedance value.

[0014] The processor converts the impedance of each functional electrode into a weighted vector. For example, the magnitude of the vector is the weight of the vector in the direction of the functional electrode from a common origin, and the weighted vectors across all functional electrodes are summed. In the case of blood pooling, such vectors can be assumed to be fixed (e.g., close to 0 for a perfectly symmetric arrangement of functional electrodes) and are only a characteristic of the assembly. The sum of the impedance-weighted vectors generates a separate blood pool direction vector only when a portion of the functional electrodes of the assembly are in proximity to the tissue wall.

[0015] Description of the System FIG. 1 is a schematic depiction of a catheter-based electroanatomical (EA) mapping and ablation system 10 according to an embodiment of the present disclosure. System 10 is configured to determine, for example, whether a given functional electrode 26 among a plurality of functional electrodes 26 of basket catheter 14 is in sufficient proximity to tissue or immersed in a blood pool 33 of a cardiac chamber prior to performing a diagnosis and / or ablation.

[0016] System 10 includes one or more catheters that are percutaneously inserted by physician 24 into a cardiac chamber or vascular structure of heart 12 through a patient's vasculature. Typically, a delivery sheath catheter is inserted into the left atrium or right atrium near a desired location of heart 12. Thereafter, one or more catheters can be inserted into the delivery sheath catheter to reach a desired location. The one or more catheters may include a catheter dedicated to sensing intracardiac electrogram (IEGM) signals, a catheter dedicated to ablation, and / or a catheter dedicated to both sensing and ablation. An exemplary basket catheter 14 configured to sense IEGM is shown herein. As seen in insertion FIG. 45, physician 24 moves a basket-type expandable distal end assembly 28 (hereinafter also referred to as “expandable distal end assembly 28”) attached to the shaft 44 of catheter 14 near the heart wall to sense a target site within heart 12. For ablation, physician 24 similarly moves the distal end of an ablation catheter to a target site for ablation.

[0017] As can be seen in Inserted Figure 65, catheter 14 is an exemplary catheter that optionally distributes over a plurality of splines 22 in an expandable distal end assembly 28 and includes one, preferably a plurality of functional electrodes 26 configured to detect IEGM signals. Catheter 14 further includes a proximal position sensor 29 (e.g., a three axial sensor (TAS) 29 with three EMCs) embedded in the distal end 46 of shaft 44 near the expandable distal end assembly 28 to track the position of the distal end of the expandable distal end assembly 28. Optionally and preferably, position sensor 29 is a magnetic-based position sensor that includes a magnetic coil for sensing three-dimensional (3D) position. The distal end 46 of shaft 44 may comprise an amplifier circuit configured to amplify the output from the three EMCs of sensor 29.

[0018] Magnetic position sensor 29 operates with an external position pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field within a predetermined workspace. Using the operation by external position pad 25 (each EMC uses a different frequency), the processor can determine the position of each EMC 29 on the coordinate system of the position tracking system.

[0019] Details of magnetic-based position sensing techniques are described in U.S. Patent Nos. 5,539,199; 5,443,489; 5,558,091; 6,172,499; 6,239,724; 6,332,089; 6,484,118; 6,618,612; 6,690,963; 6,788,967; 6,892,091.

[0020] System 10 includes one or more electrode patches 38 disposed for skin contact with patient 23 to establish a positional reference for position pad 25 and impedance-based tracking of functional electrodes 26. For impedance-based tracking, current is directed to electrodes 26 and sensed at electrode-skin patches 38, whereby the position of each electrode can be triangulated via electrode patches 38. The real-time orientation of the expandable distal end assembly 28 of catheter 14 can be calculated from the tracked positions of electrodes 26. This relative orientation is revealed by the angle formed between distal end 46 and longitudinal axis 42 of expandable assembly 28 (extending to distal edge 16 of the assembly).

[0021] Details of impedance-based position tracking techniques are described in U.S. Pat. Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182.

[0022] Catheter 14 is configured to acquire an electrical signal indicative of the proximity of any given functional electrode 26 to the tissue wall of heart 12. For this purpose, signal generator 35 is configured to generate an AC signal between each of reference ring electrode 17 and functional electrodes 26. The processor measures the corresponding impedance between each functional electrode 26 and reference ring electrode 17 disposed on the base 37 of expandable distal end assembly 28 outside the internal space 77 defined by the splines of assembly 28. The electrical paths between each functional electrode 26 and between reference ring electrode 17 and assembly 28 improve the sensitivity of the measurement to tissue proximity. Reference ring electrode 17 is positioned on the base of assembly 28 at a location that prevents contact with the tissue wall while distal end assembly 28 is in an expanded state, as further explained in FIG. 2.

[0023] Recorder 11 displays the electrocardiogram 21 captured by the body surface ECG electrodes 18 and the intracardiac electrogram (IEGM) captured by the functional electrodes 26 of the catheter 14. Recorder 11 may include pacing capabilities for pacing the rhythm of the heart and / or may be electrically connected to an independent pacer.

[0024] System 10 may include an ablation energy generator 50 that is adapted to deliver ablation energy to a subset of the plurality of electrodes 26 in the distal assembly 28 of the catheter 14 configured to ablate. The energy generated by the 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 such that they can be used to effect irreversible electroporation (IRE), but is not limited thereto.

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

[0026] The workstation 55 includes a memory 57, a processor unit 56 having a memory or storage device loaded with appropriate operating software, and a user interface function. The workstation 55 may optionally (i) render to model in three dimensions (3D) the endocardial anatomical structure and display a model or anatomical map 20 on a display device 27, (ii) display on the display device 27, in a representative visual display or image overlaid on the rendered anatomical map 20, an activation sequence (or other data) compiled from the recorded intracardiac electrogram 21, (iii) display the real-time position and orientation of a plurality of catheters within the heart chamber, and (iv) display on the display device 27 a target site such as the location where ablation energy is being applied, and may provide a plurality of functions including these. 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] FIG. 1 depicts a basket assembly, but the disclosed technology can be applied with the necessary changes to an expandable balloon assembly having an expandable membrane, with the functional electrodes disposed on the membrane.

[0028] Estimation of the blood pool direction for an expandable assembly FIG. 2 is a schematic depiction of a basket assembly 281 configured to acquire electrical measurements to determine proximity vectors 215 of the basket assembly 281 to the heart chamber tissue wall, according to an example of the present disclosure.

[0029] The basket assembly 281 can be used to implement the basket assembly 28 of FIG. 1 above. As shown, the assembly 281 is part of a catheter 214 that further includes a shaft 244 having a distal end 246. The distal end assembly 228 includes a proximal base 227 configured to couple the assembly to the distal end 246 of the shaft 244. The distal axis 278 of the assembly is defined by the longitudinal axis of the distal end 246 of the shaft 244.

[0030] The basket assembly 281 is implemented as an expandable frame with a plurality of splines 222, and the functional electrodes 226 are coupled to the splines. Each of the splines 22 is electrically insulated from the environment by an insulating layer 262 over most of its area.

[0031] As shown in FIG. 3, when the expandable distal end assembly 281 is expanded, it defines an internal space 277. Within the internal space 277, at the base of the assembly, a remote field electrode 223 is used to remove a remote field signal from the IEGM signal acquired by the electrode 226.

[0032] The plurality of functional electrodes 226 are at least partially external to the internal space and are configured to be disposed in contact with the wall tissue of the heart chamber. A reference ring electrode 217 (such as the ring electrode 17 in FIG. 1) is disposed external to the internal space 277 on the proximal base 227 of the expandable distal end assembly 281. The ring-shaped electrode 217 on the base 227 is positioned to avoid contact with the tissue wall while the distal end assembly 281 is in the expanded state.

[0033] In the example of FIG. 2, the reference ring electrode 217 is a ring fitted to the outer periphery of the proximal base section 227. The reference ring electrode 217 can be disposed, for example, on an insulating layer (not shown) if the base section 227 is electrically conductive (e.g., made of nitinol).

[0034] The proximal base section 227 further comprises a mechanical guard ring 231 which projects outwardly from the proximal base, i.e., further away from the reference electrode 227, to prevent the reference electrode 227 from contacting the tissue wall. Further improvement in measurement accuracy can be achieved by applying an internal electrical insulation coating 241 to the electrode 226 such that the electrode portion in the blood is minimized upon contact with the tissue. The coating 241 may be a certain polymer or an additional dielectric layer (e.g., silicon nitride).

[0035] The processor 56 receives impedance signals between each of the electrodes 226 and the reference electrode 217. As the catheter is moved within the blood pool and also contacts the tissue, the processor determines the minimum value R from the electrode 226 within the blood pool B and the maximum value R from the electrode 226 that is sufficiently close to or in contact with the tissue T to obtain a range of impedances having a magnitude range between them.

[0036] For an electrode having an impedance R, the processor defines the weight f j of the electrode direction unit vector v j as f j =(R T -R) / (R T -R B ). As can be understood, the weight f j is the magnitude of the unit vector v j and is equal to the impedance value after normalizing the range, e.g., a value between 0 and 1. For simplicity, it is assumed that all vectors v j have the same unit magnitude (i.e., assuming a spherical expanded distal end assembly normalized to a unit sphere). The weight f j can have any value between 0 and 1.

[0037] The electrode immersed in the blood has f j = 1, while the electrode sufficiently close to the tissue has f j = 0. Some impedance-weighted vectors f originating from the assembly center 280j v j 236 is shown as an example.

[0038] The blood direction vector B represented by arrow 350 in FIG. 3 is given by the weighted sum of all vectors v j and.

[0039]

Number

[0040] Although FIG. 2 illustrates a basket assembly, the disclosed technique can be applied to an expandable balloon assembly having an expandable membrane with the necessary modifications, and the functional electrodes are disposed on the membrane.

[0041] Providing a blood pool direction vector based on the measured impedance FIG. 3 is a schematic depiction of a proximity-based induction method of a basket catheter 214 within a patient's left atrium, according to an example of the present disclosure. This figure shows the output of a scheme within window 300 presented to physician 24, for example, on display 27. Window 300 presents the initial stage of EA mapping in real time when most of the left atrial wall has already been EA mapped. Window 300 shows the EA mapped tissue wall portion 331, the icon 341 of the distal end assembly 281, and an arrow 350 indicating the blood pool direction (found by B), where arrow 350 indicates to physician 24 the direction in which the distal end assembly 281 can be advanced without engaging the tissue wall.

[0042] As an example, the search phase of the distal end assembly is represented in three windows 300: (a), (b), and (c). Each of windows (a), (b), and (c) provides the physician with real-time advice regarding the blood pool direction 350 for moving the catheter, enabling the physician to more rapidly proceed, for example, with the expansion of rendering 331 to a more clinically meaningful EA map portion during the search phase of the EA mapping procedure.

[0043] As indicated by the arrow, window (c) may represent an advanced search stage compared to what is seen in window (b). Similarly, window (b) may represent an advanced search stage compared to what is seen in window (a). FIG. 3(c) shows to the user that the best approach to the pulmonary vein (PV) ostium has been achieved when the blood pool direction 350 is aligned with the catheter shaft (e.g., by showing when the direction arrow 350 is aligned to within a predetermined tolerance with the longitudinal axis icon 450 of the distal end assembly icon 341 (e.g., virtual representation 341)).

[0044] When EA mapping is collected over a sufficient number of anatomical landmarks (e.g., the small holes of the pulmonary vein), it becomes easier for the physician mapping the cardiac chamber with EA.

[0045] Method for providing a blood pool direction vector based on measured impedance FIG. 4 is a flowchart schematically showing a method and algorithm for estimating and presenting a blood pool direction arrow 350 based on measured impedance of functional electrodes, according to an example of the present disclosure. The algorithm, according to this embodiment, executes a process that begins by moving an expanded basket assembly 281 within the cardiac chamber of the heart 12 in a basket movement step 402.

[0046] While the basket is being moved, in a baseline impedance monitoring step 404, the system 10 monitors the impedance between each of the functional electrodes 226 and the reference ring electrode 217.

[0047] In impedance range identification step 406, when the basket occasionally contacts the heart cavity tissue wall, the processor identifies the impedance ranges for contact and non-contact with respect to the monitored and accumulated impedance values. Since the range is a function of the distance between the functional electrode and the reference electrode, a dedicated range is defined for each electrode. However, the ranges for individual electrodes can be inferred from the collective output from all functional electrodes 226 by compensating for the different distances between each functional electrode 226 and the reference electrode.

[0048] Using the monitored impedance and its identified range, the processor calculates the blood pool direction vector B350 in blood pool direction vector calculation step 408.

[0049] Finally, in direction arrow display step 410, the processor displays the respective blood pool direction arrows 350, e.g., arrow 350 on window 300, in relation to the rendering of the distal end assembly.

[0050] The exemplary flowchart shown in FIG. 4 is selected purely for the purpose of clarifying the concept. This embodiment also includes additional steps of algorithms such as acquiring an intracardiac electrocardiogram, which are intentionally omitted from the disclosure herein to provide a more simplified flowchart.

Example

[0051] (Example 1) The method includes monitoring the impedance of a plurality of functional electrodes (26) relative to a reference electrode (17) while operating a catheter (14) within the lumen of an organ (12), the catheter comprising: (i) a shaft (44) having a distal end (46); and (ii) an expandable distal end assembly (28) coupled to the distal end (46) of the shaft (44) and comprising a plurality of functional electrodes. A direction vector is estimated from the monitored impedance, and along this direction vector, the catheter is free to advance within the lumen of the organ without interference from the tissue wall of the lumen. The direction vector is displayed (300) to the user.

[0052] (Example 2) Estimating the direction vector includes estimating the blood pool direction (350) from the monitored impedance, according to the method of Example 1.

[0053] (Example 3) Estimating the blood pool direction vector includes converting the impedance of each functional electrode (26) into a weighted vector in the direction of the functional electrode based on the known geometric shape of the distal end assembly (28), and summing the weighted vectors across all functional electrodes (26), according to the method of Example 1 or 2.

[0054] (Example 4) Converting the impedance of each functional electrode (26) into a weighted vector in the direction of the functional electrode includes: (i) identifying the range of impedance for the accumulated impedance values; and (ii) normalizing each impedance within the range to serve as the weight of its respective weighted vector according to the range, according to any one of Examples 1 to 3.

[0055] (Example 5) Converting the impedance of each functional electrode (26) into a weighted vector includes calculating the weight by normalizing the impedance to a value between 0 and 1 with respect to the range, according to any one of Examples 1 to 4.

[0056] (Example 6) Displaying a direction vector (300) includes presenting a direction arrow (350) on a virtual representation of a distal assembly (341) shown on an electroanatomical (EA) map generated using an electroanatomical (EA) signal from a functional electrode, the method according to any one of Examples 1-5.

[0057] (Example 7) Displaying a direction vector includes indicating that the direction arrow (350) is aligned with a longitudinal axis icon (450) of a virtual representation (341) of the distal assembly (28), the method according to any one of Examples 1-6.

[0058] (Example 8) The distal assembly is one of a basket assembly (281) and a balloon assembly, the method according to any one of Examples 1-7.

[0059] (Example 9) The system includes an interface (30) and a processor (56). The interface (30) is configured to monitor the impedance of a plurality of functional electrodes (26) relative to a reference electrode (17) while operating a catheter within a lumen of an organ (12), the catheter comprising (i) a shaft (44) having a distal end (46) and (ii) an expandable distal assembly (28) coupled to the distal end of the shaft and comprising a plurality of functional electrodes (26). The processor (56) is configured to (i) estimate a direction vector in which the catheter can freely advance within the lumen of the organ without being obstructed by a tissue wall from the monitored impedance and (ii) display (300) the direction vector to a user.

[0060] The examples described herein mainly address cardiac diagnostic applications, but the methods and systems described herein can also be used for other medical applications.

[0061] It should be understood that the embodiments described above are given as examples, and the present disclosure is not limited to those specifically illustrated and described herein. Rather, the scope of the present disclosure includes both the various combinations and sub - combinations of functions described above, as well as those modifications and changes that would occur to those skilled in the art upon reading the foregoing description and that are not disclosed in the prior art.

[0062] 〔Embodiment〕 (1) A method comprising: monitoring the impedance of a plurality of functional electrodes relative to a reference electrode while operating a catheter within a lumen of an organ, the catheter comprising (i) a shaft having a distal end, and (ii) an expandable distal end assembly coupled to the distal end of the shaft and comprising the plurality of functional electrodes; estimating a direction vector from the monitored impedance, along which the catheter can freely advance within the lumen of the organ without interference by the tissue wall of the lumen; and displaying the direction vector to a user. (2) The method according to embodiment 1, wherein estimating the direction vector includes estimating a blood pool direction from the monitored impedance. (3) The method according to embodiment 2, wherein estimating the blood pool direction vector includes converting each impedance of the functional electrodes into a weighted vector in the direction of the functional electrode based on a known geometric shape of the distal end assembly, and summing the weighted vectors over all the functional electrodes. (4) Converting each impedance of the functional electrodes into a weighted vector in the direction of the functional electrode includes: identifying a range of impedance with respect to the accumulated impedance values; normalizing each impedance within the range so as to serve as the weight of the respective weighted vector according to the range; and is the method according to embodiment 3. (5) Converting each impedance of the functional electrodes into a weighted vector includes calculating weights by normalizing the impedance to a value between 0 and 1 with respect to the range, the method according to Embodiment 4.

[0063] (6) Displaying the direction vector includes presenting a direction arrow on a virtual representation of the distal end assembly shown on an EA map generated using electroanatomical (EA) signals from the functional electrodes, the method according to Embodiment 1. (7) Displaying the direction vector includes indicating that the direction arrow is aligned with the longitudinal axis icon of the virtual representation of the distal end assembly, the method according to Embodiment 6. (8) The distal end assembly is one of a basket assembly and a balloon assembly, the method according to Embodiment 1. (9) A system, An interface configured to monitor the impedance of a plurality of functional electrodes relative to a reference electrode while manipulating a catheter within a lumen of an organ, the catheter comprising (i) a shaft having a distal end and (ii) an expandable distal end assembly coupled to the distal end of the shaft and comprising the plurality of functional electrodes, the interface; A processor, Estimating a direction vector from the monitored impedance, along which the catheter can freely advance within the lumen of the organ without interference from the tissue wall of the lumen, and Displaying the direction vector to a user, the processor configured to perform. A system comprising. (10) The processor is configured to estimate the direction vector by estimating a blood pooling direction from the monitored impedance, the system according to Embodiment 9.

[0064] (11) The processor is configured to estimate the blood pool direction vector by converting the impedance of each functional electrode into a weighted vector in the direction of the functional electrode based on the known geometric shape of the distal end assembly and summing the weighted vectors across all the functional electrodes, according to System of Embodiment 10. (12) The processor identifies a range of impedance for the accumulated impedance values, and normalizes each impedance within the range to be the weight of the respective weighted vector according to the range, and is configured to convert the impedance of each functional electrode into a weighted vector in the direction of the functional electrode, according to System of Embodiment 11. (13) The processor is configured to convert the impedance of each functional electrode into a weighted vector by calculating a weight by normalizing the impedance to a value between 0 and 1 with respect to the range, according to System of Embodiment 12. (14) The processor is configured to display the direction vector by presenting a direction arrow on a virtual representation of the distal end assembly shown on an EA map generated using the EA signal from the functional electrode, according to System of Embodiment 9. (15) The processor is configured to display the direction vector by indicating that the direction arrow is aligned with the longitudinal axis icon of the virtual representation of the distal end assembly, according to System of Embodiment 14.

[0065] (16) The distal end assembly is one of a basket assembly and a balloon assembly, according to System of Embodiment 9.

Claims

1. 1. A system comprising: an interface configured to monitor impedance of a plurality of functional electrodes relative to a reference electrode during manipulation of a catheter within a cavity of an organ, the catheter comprising: (i) a shaft having a distal end; and (ii) an expandable distal tip assembly coupled to the distal end of the shaft, the expandable distal tip assembly comprising the plurality of functional electrodes; 1. A processor comprising: estimating from the monitored impedance a directional vector along which the catheter advances freely within the cavity of the organ without obstruction by a tissue wall of the cavity; displaying the directional vector to a user; and A system comprising:

2. The system of claim 1 , wherein the processor is configured to estimate the directional vector by estimating a blood pool direction from the monitored impedance.

3. 3. The system of claim 2, wherein the processor is configured to estimate the blood pool direction vector by converting each impedance of a functional electrode into a weighted vector of orientation of the functional electrode based on a known geometry of the distal tip assembly and summing the weighted vectors over all the functional electrodes.

4. The processor, identifying an impedance range for the accumulated impedance values; normalizing each impedance within said range to become a weight of said respective weighting vector according to said range; 4. The system of claim 3, configured to convert each impedance of a functional electrode into a weighted vector of directions of said functional electrode by:

5. 5. The system of claim 4, wherein the processor is configured to convert each impedance of a functional electrode into a weighted vector by calculating weights by normalizing the impedance to a value between 0 and 1 for the range.

6. 2. The system of claim 1, wherein the processor is configured to display the directional vector by presenting a directional arrow on a virtual representation of the distal end assembly shown on an EA map generated using EA signals from the functional electrodes.

7. The system of claim 6 , wherein the processor is configured to display the directional vector by indicating that the directional arrow is aligned with a longitudinal axis icon of the virtual representation of the distal tip assembly.

8. The system of claim 1 , wherein the distal end assembly is one of a basket assembly and a balloon assembly.

9. 1. A method comprising: monitoring impedance of a plurality of functional electrodes relative to a reference electrode during manipulation of a catheter within a cavity of an organ, the catheter comprising: (i) a shaft having a distal end; and (ii) an expandable distal tip assembly coupled to the distal end of the shaft, the distal tip assembly comprising the plurality of functional electrodes; estimating from the monitored impedance a directional vector along which the catheter advances freely within the cavity of the organ without obstruction by a tissue wall of the cavity; and displaying the directional vector to a user.

10. The method of claim 9 , wherein estimating the directional vector comprises estimating a blood pool direction from the monitored impedance.

11. 11. The method of claim 10, wherein estimating the blood pool direction vector comprises converting each impedance of a functional electrode into a weighted vector of directions of the functional electrodes based on a known geometry of the distal tip assembly, and summing the weighted vector over all the functional electrodes.

12. Transforming each impedance of a functional electrode into a weighted vector of directions of said functional electrodes, comprising: identifying an impedance range for the accumulated impedance values; normalizing each impedance within said range to become a weight of said respective weighting vector according to said range; The method of claim 11 , comprising:

13. 13. The method of claim 12, wherein converting each impedance of a functional electrode into a weighted vector comprises calculating weights by normalizing the impedance to a value between 0 and 1 for the range.

14. 10. The method of claim 9, wherein displaying the directional vector comprises presenting a directional arrow on a virtual representation of the distal tip assembly shown on an electroanatomical (EA) map generated using EA signals from the functional electrodes.

15. The method of claim 14 , wherein displaying the directional vector includes indicating that the directional arrow is aligned with a longitudinal axis icon of the virtual representation of the distal tip assembly.

16. The method of claim 9 , wherein the distal end assembly is one of a basket assembly and a balloon assembly.

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