Impedance-based navigation of sheath
Patent Information
- Application Number
- JP2024133987
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-08-10
- Filing Date
- 2024-08-09
- Publication Date
- 2025-02-21
Smart Images
Figure 2025026437000001_ABST
Abstract
Description
[Background technology]
[0001] Tracking the position of internal body objects such as sensors, tubes, catheters, dispensing devices, and implants is required in many medical procedures. Well-established high-precision systems for determining the position of internal body objects have been developed based on magnetic field sensing. These systems utilize sensors attached to the internal body objects to measure the relative strength of externally generated magnetic fields and derive the object's position from these measurements. Details of magnetic-based position sensing technology are described in U.S. Patent Nos. 5,391,199, 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, and 6,892,091, each of which is incorporated herein by reference.
[0002] Position sensing systems have also been developed that utilize impedance-based measurements. In such systems, impedance is measured between electrodes affixed to the internal object and electrodes placed on the body surface. The system then derives the position of the internal object from the impedance measurements. Details of impedance-based position tracking techniques are described in U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182, each of which is incorporated herein by reference and attached in an appendix hereto.
[0003] Regions of cardiac tissue can be mapped by a catheter to identify abnormal electrical signals. The cardiac tissue can be ablated to block the abnormal electrical signals. Electrophysiological mapping can include the use of sensing electrodes on a catheter that are configured to monitor electrical signals in the cardiovascular system to pinpoint the location of abnormal conductive tissue sites involved in arrhythmias. An example of an EP mapping system is described in U.S. Pat. No. 5,738,096, which is incorporated herein by reference. Examples of EP mapping catheters are described in U.S. Pat. No. 9,907,480, U.S. Patent Publication No. 2018 / 0036078, and U.S. Patent Publication No. 2018 / 0056038, each of which is incorporated herein by reference.
[0004] In addition to using EP mapping, some catheter ablation procedures may be performed using an image guided surgery (IGS) system. An IGS system may allow a physician to visually track the position of the catheter within the patient in real time in conjunction with an image of the patient's internal anatomy. Some systems, including the CARTO 3® system by Biosense Webster, Inc. (Irvine, Calif.), may offer a combination of EP mapping and IGS capabilities. Summary of the Invention [Means for solving the problem]
[0005] Presented herein is a sheath that can have radial perforations in the sheath wall approximately 1-3 centimeters (cm) from the distal end of the sheath. The perforations can be large enough to allow saline to perfuse during sheath irrigation. The perforations can extend approximately 1-2 millimeters (mm) along the length of the sheath. The sheath is configured such that the perforations act as conductive conduits to an impedance-based tracking electrode of a catheter positioned within the lumen of the sheath. When the impedance-based tracking electrode is positioned adjacent to or near the perforation. The impedance-based tracking electrode can be positioned on the shaft of the catheter. For example, the impedance-based tracking electrode can include an inferior vena cava (IVC) electrode, which is the most proximal electrode of a local catheter, such as the SMARTTOUCH® SF by Biosense Webster. When the impedance-based tracking electrode is positioned adjacent to or near the perforation, current injected from the catheter electrode will be conducted primarily through the perforation. The control unit of the impedance-based tracking system can calculate the location of the sheath perforation based on the ratio of current between the impedance-based tracking electrodes and the body patch (e.g., six body patches). This calculation allows visualization of the sheath itself instead of only the impedance-based tracking electrodes moving through the sheath. Alternatively, instead of perforations, small bands of conductive material can be placed on the sheath to allow current to pass through the sheath wall. This conductive material can be polymeric or metallic in nature, can make up the entire section of the sheath in that region, and / or can include conductive fibers or rivets (polymeric or metallic) that act as pass-through channels for ACL flow.
[0006] An exemplary guide sheath may include a tubular shaft extending along a longitudinal axis between a proximal end and a distal end. The tubular shaft may have a lumen therethrough and a tubular wall surrounding the lumen. The predetermined tubular wall region may be configured to provide an electrically conductive pathway through a tubular wall of the tubular shaft. The predetermined tubular wall region may be disposed proximate to a distal end of the tubular shaft.
[0007] An exemplary impedance-based tracking system may include a guide sheath, a medical probe, a plurality of body patch electrodes, and a control unit. The guide sheath may include a first tubular shaft having a lumen therethrough and a predetermined tubular wall region disposed near a distal end of the first tubular shaft. The predetermined tubular wall region may be configured to provide a conductive path through the predetermined tubular wall region. The medical probe may include a second tubular shaft configured to be translated through the lumen of the first tubular shaft. The medical probe may further include a tracking electrode coupled to the second tubular shaft. The plurality of body patch electrodes may be configured to contact the patient's skin. The control unit may be configured to determine a position of the predetermined tubular wall region based at least in part on an electrical signal between the tracking electrode and the plurality of body patch electrodes.
[0008] An exemplary method of impedance tracking of a guide sheath within a patient can include the following steps, performed in various orders and with interleaving steps, as will be appreciated by those skilled in the art: The method can include passing a current signal between a probe electrode of a medical probe and a plurality of body patch electrodes, the probe electrode being disposed within a lumen of a guide sheath within the patient and the plurality of body patch electrodes being in contact with the patient's skin. The method can include determining a position of a distal portion of the guide sheath based at least in part on the current signal. [Brief description of the drawings]
[0009] While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter described herein, it is believed that the subject matter will be better understood from the following description of specific embodiments taken in conjunction with the accompanying drawings, in which like reference numerals identify the same elements and in which: The figures depict one or more implementations of the device of the present invention by way of example only, and not by way of limitation. [Figure 1] FIG. 1 illustrates an exemplary catheter-based electrophysiological mapping and ablation system. [Diagram 2] FIG. 1 is a diagram of an exemplary sheath and catheter. [Figure 3A] FIG. 2 is a view of the distal portion of the sheath. [Figure 3B] FIG. 2 is a view of the distal portion of the catheter. [Figure 4A] FIG. 1 is a diagram of an impedance-based tracking system in which the impedance-based tracking electrodes of the catheter are not adjacent to the conductive regions of the sheath. [Figure 4B] FIG. 1 is a diagram of an impedance-based tracking system in which impedance-based tracking electrodes are adjacent to conductive regions of a sheath. [Diagram 5] 1 is a diagram of a distal portion of an exemplary sheath. [Figure 6A] 6 is a cross-sectional view of a distal portion of an exemplary sheath as shown in FIG. 5 showing an exemplary configuration of a given tubular wall region configured to provide an electrically conductive path through the tubular wall. [Figure 6B] 6 is a cross-sectional view of a distal portion of an exemplary sheath as shown in FIG. 5 showing an exemplary configuration of a given tubular wall region configured to provide an electrically conductive path through the tubular wall. [Figure 6C] 6 is a cross-sectional view of a distal portion of an exemplary sheath as shown in FIG. 5 showing an exemplary configuration of a given tubular wall region configured to provide an electrically conductive path through the tubular wall. [Figure 6D] 6 is a cross-sectional view of a distal portion of an exemplary sheath as shown in FIG. 5 showing an exemplary configuration of a given tubular wall region configured to provide an electrically conductive path through the tubular wall. [Figure 7] FIG. 1 is a flow diagram of a method for impedance tracking a guide sheath within a patient. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. The detailed description illustrates, by way of example and not by way of limitation, the principles of the invention. The description clearly enables one skilled in the art to make and use the invention and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is currently contemplated to be the best mode for carrying out the invention.
[0011] As used herein, the term "about" or "approximately" in relation to any numerical value or range indicates a suitable dimensional tolerance that enables a portion or collection of components to function for the intended purpose described herein. More specifically, "about" or "approximately" may refer to a range of values of ±10% of the recited value, for example, "about 90%" may refer to a range of values of 81% to 99%.
[0012] Additionally, as used herein, the terms "patient," "host," "user," and "subject" refer to any human or animal subject, and while use of the invention in a human patient represents a preferred embodiment, it is not intended to limit the systems or methods to human use. Similarly, the term "proximal" refers to a location closer to the operator, while "distal" refers to a location further away from the operator or physician.
[0013] As used herein, the terms "tubular" and "pipe" are to be interpreted broadly and are not limited to right cylindrical structures, or structures that are strictly circular in cross section, or structures that are uniform in cross section throughout their length. For example, a tubular structure or system is generally illustrated as a substantially right cylindrical structure. However, a tubular structure or system may have a tapered or curved outer surface without departing from the scope of the invention. A tubular structure or system or pipe may have a hollow lumen, a solid core, or a combination thereof.
[0014] As used herein, the terms "sheath" and "guide sheath" refer to an elongated intravascular device having a hollow tubular shaft configured to deliver one or more medical probes to a treatment site within a patient's body. A sheath or guide sheath is sized based on the inner diameter (e.g., measured in French units) of the lumen of the hollow tubular shaft. A sheath or guide sheath may or may not be steerable.
[0015] As used herein, the term "catheter" refers to an elongated intravascular device that may be configured as a therapeutic and / or diagnostic medical probe. Catheters are sized based on the outer diameter (e.g., measured in French units) of the elongated tubular body. Catheters may be delivered through a matching sheath having a size that matches the size of the catheter.
[0016] Alternative apparatus and system features and alternative method steps are presented in the exemplary embodiments herein. Each given exemplary embodiment presented herein can be modified to include features and / or method steps presented with different exemplary embodiments herein, but such features and / or steps are compatible with the given embodiment as understood by those skilled in the art and as expressly set forth herein. Such modifications and variations are intended to be included within the scope of the claims.
[0017] FIG. 1 illustrates an exemplary catheter-based electrophysiology mapping and ablation system 10. The system 10 includes multiple catheters that are percutaneously inserted by a physician 24 through a patient's vascular system into a cavity or vasculature of the heart 12. Typically, a guide sheath 40 is inserted into the left or right atrium near a desired location in the heart 12. Multiple catheters can then be inserted through the guide sheath 40 to reach the desired location. The multiple catheters may include catheters dedicated to sensing Intracardiac Electrogram (IEGM) signals, catheters dedicated to ablation, and / or catheters configured for both sensing and ablation. An exemplary catheter 14 is illustrated herein. The physician 24 brings a distal electrode 34 of the catheter 14 into contact with the heart wall to sense and / or ablate a target site in the heart 12.
[0018] The catheter 14 optionally includes a magnetic-based position sensor 29 embedded in the distal portion 28 of the catheter 14 for tracking the position and orientation of the distal portion 28. Preferably, the magnetic-based position sensor 29 includes three magnetic coils for sensing three-dimensional (3D) position and orientation.
[0019] The magnetic-based position sensor 29 may operate in conjunction with a location pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field within a predetermined working volume. The real-time position of the distal portion 28 of the catheter 14 may be tracked based on the magnetic fields generated using the location pad 25 and sensed by the magnetic-based position sensor 29. Details of magnetic-based position sensing technology are described in U.S. Patent Nos. 5,391,199; 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; and 6,892,091, which are incorporated herein by reference.
[0020] The illustrated system 10 includes one or more electrode patches 38 positioned for skin contact on the patient 23 to establish a location reference for the location pads 25 and impedance-based tracking of one or more impedance-based tracking electrodes 26. For impedance-based tracking, a current is directed to the impedance-based tracking electrodes 26 and sensed at the electrode skin patch 38, so that the position of each electrode 26 can be triangulated via the electrode patch 38. Details of impedance-based position tracking technology are described in U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182, which are incorporated by reference herein and attached as an appendix hereto.Instead of relying on a patch 38, the catheter can utilize existing impedance sensing electrodes 39′ on the sheath 40 (FIG. 4B), which are provided on the Biosense Webster Vizigo Sheath Introducer product (shown here: https: / / www.jnjmedtech.com / en-US / product / carto-vizigo-bi-directional-guiding-sheath) and the article entitled “FIRST EXPERIENCE WITH LEFT ATRIAL ARRHYTHMIA ABLATION USING A BIDIRECTIONAL STEERABLE TRANSSEPTAL SHEATH(VIZIGO)VISIBLE IN THE CARTO SYSTEM AS A METHOD TO REDUCE FLUOROSCOPY”, published in EUROPEAN JOURNAL OF TRANSLATIONAL AND CLINICAL MEDICINE 2020;3(2):18-21, corresponding author: Edward Kozluk,PhD MD,I Chair and Department of Cardiology,Medical University The impedance sensing electrodes are similar to those described in the literature by Edward Kozluk1, Katarzyna Lojewska, Jaroslaw Hiczkiewicz of Warsaw, available online at www.ejtcm.gumed.edu.pl, a copy of which is incorporated herein by reference and attached in an appendix hereto. In some embodiments, the sensing electrode 39' is optional and the position of the sheath 40 can be determined without the sensing electrode 39'.
[0021] The guide sheath 40 may include a predetermined tubular wall region 42 positioned at a predetermined location relative to the distal end 43 of the sheath within the wall of the tubular shaft 47 of the guide sheath 40. The predetermined tubular wall region includes a low impedance path through the wall of the guide sheath 40. When the impedance-based tracking electrode 26 of the catheter 14 is positioned adjacent the predetermined tubular wall region 42 of the guide sheath 40, a current is directed to the impedance-based tracking electrode 26, through the predetermined tubular wall region 42, and sensed at the electrode skin patch 38, so that the location of the predetermined tubular wall region 42 may be triangulated via the electrode patch 38 using the systems and methods disclosed in U.S. Patent Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182, variations thereof, and alternatives thereof. These are incorporated herein by reference and are attached as appendices hereto, as will be understood by those of skill in the art.
[0022] The predetermined tubular wall region 42 is located approximately one centimeter from the distal end 43 of the tubular shaft of the sheath 40 and can extend approximately one to two millimeters along the tubular shaft.
[0023] The given tubular wall region 42 can include various features to facilitate electrical conduction through the tubular wall at the given tubular wall region 42. For example, the given tubular wall region can include pores sized to allow flow of saline from the lumen through the tubular wall of the tubular shaft, conductive bands coupled to the tubular wall of the guide sheath and configured to conduct electrical current between the lumen and the environment external to the tubular shaft, conductive rivets extending through the tubular wall of the guide sheath, conductive fibers embedded in the tubular wall of the guide sheath and configured to conduct electrical current between the lumen and the environment external to the tubular shaft, combinations thereof, or variations thereof in various combinations.
[0024] The guide sheath 40 further includes a sheath handle 44 coupled to a proximal end of the tubular shaft 47. The handle 44 can be configured to deflect the distal portion 41 of the tubular shaft 47 of the guide sheath 40. The guide sheath 40 can further include an irrigation port configured to connect to an irrigation system 51 to provide irrigation fluid to the lumen of the guide sheath 40. If the given tubular wall region 42 includes pores, the flow of saline through the pores can provide a conductive path through the tubular wall of the tubular shaft 47 of the guide sheath 40. The distal portion 41 of the guide sheath 40 can be located based on an impedance signal through the saline in the pores of the given tubular wall region 42.
[0025] The tubular shaft 47 of the guide sheath 40 may lack an active position sensor. Impedance-based tracking based on electrical signals through a given tubular wall region 42 may be sufficient to track the distal portion 41 of the guide sheath 40. The guide sheath 40 may further lack an electrical port. Impedance-based tracking based on electrical signals through a given tubular wall region 42 may be sufficient to track the distal portion 41 of the guide sheath 40 without any electrical signals being transmitted along the length of the tubular shaft 47.
[0026] The impedance-based tracking electrodes 26 may be multi-functional and may additionally be configured for sensing and / or ablation.
[0027] Recorder 11 displays electrograms 21 captured by the body surface ECG electrodes 18, and intracardiac electrograms (IEGMs) captured by one or more electrodes 26, 34 of catheter 14. Recorder 11 may include pacing capability for pacing the cardiac rhythm and / or may be electrically connected to a stand-alone pacer.
[0028] The system 10 may include an ablation energy generator 50 adapted to conduct ablation energy to the distal electrode 34 of the catheter 14. The energy generated by the ablation energy generator 50 may include, but is not limited to, radiofrequency (RF) energy or pulsed-field ablation (PFA) energy, including monopolar or bipolar high-voltage DC pulses such as may be used to effect irreversible electroporation (IRE), or combinations thereof.
[0029] The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between the catheters, the electrophysiological equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiological equipment of the system 10 may include, for example, multiple catheters, localization pads 25, body surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 includes processing capabilities for performing real-time calculations of catheter location and for performing ECG calculations.
[0030] The workstation 55 includes a processor unit having a memory, a memory or storage device loaded with appropriate operating software, and a user interface function. The workstation 55 can be configured to provide multiple functions, optionally including: (1) modeling the endocardial anatomical structure in three dimensions (3D) and rendering the model or anatomical map 20 for display on the display device 27, (2) displaying on the display device 27 activation sequences (or other data) compiled from the recorded electrograms 21 with representative visual indicia or images superimposed on the rendered anatomical map 20, (3) displaying a graphical representation 53 of the sheath 40 and / or a graphical representation 52 of the catheter 14 with their real-time positions and orientations within the heart chambers, and (4) displaying on the display device 27 sites of interest, such as locations where ablation energy has been applied. One commercially available product embodying elements of system (10) is available as the CARTO™ 3 system, commercially available from Biosense Webster, Inc., 31A Technology Drive, Irvine, Calif., 92618.
[0031] 2 is a diagram of an exemplary guide sheath 40 and catheter 14. The guide sheath 40 includes a handle 44, an irrigation port 49 extending proximally from the handle 44, and a tubular shaft 47 extending distally from the handle 44. The tubular shaft 47 has a distal portion 41 and a predetermined tubular wall region 42 at the distal portion 41. The handle 44 includes a knob 48 that can be manipulated to deflect the distal portion 41 of the tubular shaft 47, as shown.
[0032] The catheter 14 may include a handle 16 and a catheter shaft 17 extending distally from the catheter handle 16. The catheter shaft 17 includes an impedance-based tracking electrode 26 and a distal electrode 34. The distal portion of the catheter shaft 17 can be deflected by manipulation of a catheter knob 19 on the catheter handle 16.
[0033] The guide sheath 40 includes a lumen therethrough through which the shaft of the catheter 14 may be translated. As shown, the catheter shaft may extend through a handle 44 of the guide sheath 40, extend through a tubular shaft 47 of the guide sheath, and extend from a distal end 43 of the guide sheath 40. When the impedance-based tracking electrode 26 of the catheter 14 is aligned with a given tubular wall region 42, a conductive pathway exists through the given tubular wall region 42 to the impedance-based tracking electrode 26.
[0034] FIG. 3A is a diagram of the distal portion 41 of the sheath 40. The tubular shaft 47 includes a proximal conductive region 46 and a distal conductive region 45. Each conductive region 45, 46 is configured similarly to the given tubular wall region 42 illustrated in FIGS. 1, 2, 4A, 4B, 5, and 6A-6D. Each conductive region 45, 46 may include pores sized to allow flow of saline from the lumen through the tubular wall of the tubular shaft, conductive bands coupled to the tubular wall of the guide sheath and configured to conduct electrical current between the lumen and the external environment of the tubular shaft, conductive rivets extending through the tubular wall of the guide sheath, conductive fibers embedded in the tubular wall of the guide sheath and configured to conduct electrical current between the lumen and the external environment of the tubular shaft, combinations thereof, or variations thereof in various combinations. Each conductive region 45, 46 may otherwise be configured to provide an electrically conductive path through the tubular wall of the tubular shaft 47 of the guide sheath 40.
[0035] The distal conductive region 45 may be disposed a predetermined distance L1 from the distal end 43 of the guide sheath 40. The proximal conductive region 46 may be disposed a predetermined distance L3 from the distal end 43 of the guide sheath 40. The distal conductive region 45 may be shaped as a ring having a length L2 that surrounds the tubular shaft 47. The proximal conductive region 46 may be shaped as a ring of length L4 that surrounds the tubular shaft 47.
[0036] 3B is a diagram of a distal portion 28 of the catheter 14. The catheter 14 includes ring electrodes 31, 35, 36, 37, 39. Each of the ring electrodes may be configured as an impedance tracking electrode similar to the impedance-based tracking electrode 26 illustrated in FIGS. 1, 2, 4A, and 4B. The catheter 14 may include a distal ring electrode 31 disposed a first distance L5 from the distal end 33 of the catheter 14, a second ring electrode 35 disposed a second distance L6 from the distal end 33 of the catheter 14, a third ring electrode 35 disposed a third distance L7 from the distal end 33 of the catheter 14, a fourth ring electrode 35 disposed a fourth distance L8 from the distal end 33 of the catheter 14, and a fifth ring electrode 35 disposed a fifth distance L9 from the distal end 33 of the catheter 14.
[0037] As illustrated in Figures 3A and 3B, the guide sheath 40 can include multiple conductive regions 45, 46 and the catheter 14 can include multiple ring electrodes 31, 35, 36, 37, 39. Some or all of the ring electrodes 31, 35, 36, 37, 39 can be configured as impedance tracking electrodes. As the catheter 14 moves distally through the guide sheath 40, the ring electrodes 31, 35, 36, 37, 39 pass through the conductive regions 45, 46. The distances L1, L3 and distances L5, L6, L7, L8, L9 between the conductive regions 45, 46 and the distal end 43 of the guide sheath 40 can be configured such that two of the ring electrodes 31, 35, 36, 37, 39 are simultaneously aligned with the conductive regions 45, 46, so that the positions of the conductive regions 45, 46 can be simultaneously determined by an impedance-based tracking system. The distances L1, L3, L5, L6, L7, L8, L9 may be further configured such that two of the ring electrodes (e.g., the two most proximal electrodes 37, 39) are simultaneously aligned with the conductive regions 45, 46 while a third electrode (e.g., one or both of the intermediate electrodes 35, 36) is positioned distal to and proximate the distal end 43 of the guide sheath 40 such that the location of the conductive regions 45, 46 and the location of the distal end 43 of the guide sheath 40 may be determined by the impedance-based tracking system. The curvature of the distal portion 41 of the guide sheath 40 may be determined based on the locations of the conductive regions 45, 46 and the distal end 43. The impedance-based tracking system may further determine the location and curvature of the distal portion of the catheter 14 based on the locations of the ring electrodes 31, 35, 36, 37, 39 distal to the distal end 43 of the guide sheath 40.
[0038] The illustrated catheter 14 is a local ablation catheter. Examples of local ablation catheters include CELSIUS®, NAVISTAR®, THERMOCOOL SMARTTOUCH® SF, THERMOCOOL SMARTTOUCH®, THERMOCOOL®, and THERMOCOOL® RMT by Biosense Webster. Alternatively, the catheter 14 may be another therapeutic or diagnostic catheter configured with at least one impedance-based tracking electrode 26. The catheter 14 may include a linear end effector (as shown), a lasso or curved end effector, a cage end effector, a balloon end effector, a light beam end effector, variations thereof, or alternatives thereof, as will be appreciated by those skilled in the art. The end effector of the catheter 14 may include one or more electrodes configured to sense intracardiac electrogram signals. The end effector of the catheter 14 may include one or more electrodes configured to provide an electrical signal for radio frequency ablation and / or irreversible electroporation.
[0039] As an alternative to the catheter 14, the system 10 (FIG. 1) can be configured to include a medical probe having at least one impedance-based tracking electrode 26. For example, a dilator having at least one impedance-based tracking electrode 26, or a medical probe having a dilator and at least one impedance-based tracking electrode 26, can be used in place of the catheter 14.
[0040] At least one of the predetermined tubular wall regions 45, 46 is preferably located about 1 centimeter to about 3 centimeters from the distal end 43 of the tubular shaft 47 of the guide sheath 40. The lengths L2, L4 of the predetermined tubular wall regions are preferably about 1 millimeter to about 2 millimeters.
[0041] 4A is a diagram of an impedance-based tracking system in which the impedance-based tracking electrodes 26 of the catheter 14 are not adjacent to a predetermined tubular wall region 42 of the sheath 40. For purposes of illustration, the catheter 14 includes only one impedance-based tracking electrode 26 and the sheath 40 includes only one predetermined tubular height region 42. The catheter 14 and / or sheath 40 may alternatively be configured as disclosed in connection with FIGs. 3A and 3B. The catheter 14 is positioned with its tubular body within the tubular body of the guiding sheath 40 such that the tubular bodies of the catheter 14 and guiding sheath 40 are aligned along a longitudinal axis AA.
[0042] The impedance-based tracking system includes a guide sheath 40, a catheter 14 (or other suitable medical probe), a body patch 38, and a control unit 56. Figures 4A and 4B include elements of the system 10 illustrated in Figure 1.
[0043] When the impedance-based tracking electrode 26 is not aligned with a given tubular wall region 42, there is no direct path for current between the impedance-based tracking electrode 26 and the body patch 38, and therefore the impedance between the impedance-based tracking electrode 26 and the body patch 38 is high. When the impedance-based tracking electrode 26 is not aligned with a given tubular wall region 42, it may be difficult or impossible to determine the position of the impedance-based tracking electrode 26.
[0044] FIG. 4B is a diagram of an impedance-based tracking system in which the impedance-based tracking electrode 26 is adjacent to a predetermined tubular wall region 42 of the guide sheath 40. When the impedance-based tracking electrode 26 is aligned with the predetermined tubular wall region 42, a current can pass between the body patch electrode 38 and the impedance-based tracking electrode 26 through the predetermined tubular wall region 42. Additionally or alternatively, a sensing electrode 39′ can be used in place of the body patch electrode 38. The control unit 56 can be configured to determine a position of the predetermined tubular wall region 42 based at least in part on an electrical signal between the tracking electrode 26 and the body patch electrode 38. The controller can be configured to drive a current between the body patch electrode 38 and the impedance-based tracking electrode 26. The controller can be configured to measure an impedance between the impedance-based tracking electrode 26 and the body patch electrode 38 to determine a distance between each of the impedance-based tracking electrodes 26 and the body patch electrode 38 and to determine a three-dimensional coordinate of the impedance-based tracking electrode 26.
[0045] The impedance between the impedance-based tracking electrode 26 and each of the body patch electrodes 38 decreases dramatically as the impedance-based tracking electrode 26 moves from a misaligned position (e.g., FIG. 4A) to an aligned position (e.g., FIG. 4B). The control unit 56 can be configured to determine that the impedance-based tracking electrode 26 is aligned with a given tubular wall region 42 by detecting the dramatic decrease in impedance.
[0046] When the catheter 14 includes two or more impedance-based tracking electrodes 26 (e.g., ring electrodes 31, 35, 36, 37, 39 illustrated in FIG. 3B), at least one of the impedance-based tracking electrodes can be in a misaligned position (e.g., FIG. 4A) while at least one of the impedance-based tracking electrodes is aligned with one or more conductive regions of the guide sheath 40. There can be a higher impedance between the impedance-based tracking electrode and the body patch electrode 38 in the misaligned position compared to the impedance between the impedance-based tracking electrode and the body patch electrode 38 in the aligned position. The control unit 56 can be configured to determine which of the impedance-based tracking electrodes are in an aligned position versus a misaligned position based on a comparison of the impedance between each impedance-based tracking electrode and the body patch electrode 38. The controller can be configured to determine that the impedance-based tracking electrode with the higher impedance is misaligned and that one with the lower impedance is aligned. The controller can be configured to determine a location of each predetermined tubular wall region based on the location of each impedance-based tracking electrode in the aligned position.
[0047] The control unit 56 can be configured to determine the position of the distal end 43 of the tubular shaft of the guide sheath 40 based at least in part on the position of the predetermined tubular wall region 42 .
[0048] The control unit 56 can be configured to determine a position and orientation of the distal portion 41 of the guide sheath 40 relative to the patient's anatomy. As illustrated in FIG. 1, the system 10 can be configured to generate an anatomical map 20. A graphical representation 52 of the distal portion of the catheter 14 can be superimposed on the anatomical map 20 based on magnetic and / or impedance-based tracking of the catheter 14. A graphical representation 53 of the distal portion 41 of the guide sheath 40 can be superimposed on the anatomical map 20 based on impedance-based tracking of a given tubular wall region 62 (or a given tubular wall region).
[0049] The control unit 56 can be configured to determine the position and orientation of the distal portion 41 of the guide sheath 40 without relying on an active position sensor on the tubular shaft 47 of the guide sheath 40. The control unit 56 can be configured to determine the position and orientation of the distal portion 41 of the guide sheath 40 that lacks an active position sensor.
[0050] The control unit 56 can be configured to determine the position and orientation of the distal portion 41 of the guide sheath 40 without relying on any electrical signal connection to the guide sheath 40. The control unit 56 can be configured to determine the position and orientation of the distal portion 41 of the guide sheath 40 that lacks an electrical port.
[0051] 4B is optional. Additionally or alternatively, the sensing electrodes 39' can be used in place of or in addition to the body patch electrodes 38.
[0052] FIG. 5 is a view of the distal portion 41 of the guide sheath 40.
[0053] 6A, 6B, 6C, and 6D are cross-sectional views of the distal portion 41 of the guide sheath 40 as shown in FIG. 5, illustrating exemplary configurations of predetermined tubular wall regions 42 configured to provide a conductive pathway through the tubular wall.
[0054] Figure 6A illustrates a cross-section in which a given tubular wall region 42a includes circular pores 62a similar to those illustrated in Figure 1. The pores can allow saline to flow through the lumen of the guide sheath 40 to provide a conductive path through the tubular wall of the guide sheath 40. Alternatively, the tubular wall region 42 can include a circular plug filled with a conductive material (e.g., a conductive polymer or metal) as an alternative to saline.
[0055] 6B illustrates a cross-section in which a given tubular wall region 42b includes a conductive rivet 62b extending through the wall of the first tubular shaft. The rivet includes a conductive material (e.g., a conductive polymer or metal).
[0056] FIG. 6C illustrates a cross-section in which a given tubular wall region 42c includes a conductive band 62c or ring that is coupled to the wall of the tubular shaft of the guide sheath 40 and configured to conduct electrical current between the lumen and the environment external to the tubular shaft.
[0057] 6D illustrates a cross-section in which a given tubular wall region 42d includes conductive fibers 62d embedded in the wall of the tubular shaft of the guide sheath 40. The conductive fibers 62d are configured to conduct electrical current between the lumen of the tubular shaft of the guide sheath 40 and the environment external to the tubular shaft.
[0058] 7 is an illustration of a flow diagram of a method 100 of impedance tracking a guide sheath within a patient. The method 100 can be implemented using the system illustrated in FIGs. 4A and 4B and the system 10 illustrated in FIG. 1, variations thereof, and alternatives thereof, as would be understood by one of ordinary skill in the art. The guide sheath can be configured with features of the guide sheath 40 illustrated herein, variations thereof, and alternatives thereof, as would be understood by one of ordinary skill in the art.
[0059] In block 102, a current signal can be passed between a probe electrode and a plurality of body patch electrodes of a medical probe, while the probe electrode is disposed within a lumen of a guide sheath in a patient and the plurality of body patch electrodes are in contact with the patient's skin. The probe electrode can be configured similar to any of the impedance-based tracking electrodes 26, 31, 35, 36, 37, 39 illustrated herein, their variations, and their alternatives, as will be understood by those skilled in the art. The plurality of body patch electrodes can be configured similar to the body patch electrode 38 illustrated herein, their variations, and their alternatives, as will be understood by those skilled in the art. The medical probe can be configured similar to the catheter 14, the dilator, the medical probe with the dilator, other such medical probes as disclosed herein, their variations, and their alternatives, as will be understood by those skilled in the art. The current signal can be passed between the body patch electrode and the probe electrode by a control unit, such as the control unit 56 illustrated in FIG. 4A and FIG. 4B, a patient interface unit, such as the PIU 30 illustrated in FIG. 1, their variations, and their alternatives, as will be understood by those skilled in the art.
[0060] At block 104, translation of the probe electrode through a lumen adjacent a predetermined tubular wall region of a wall of the guide sheath is detected. The predetermined tubular wall region can be configured similarly to the predetermined tubular wall regions 62, 62a-d or conductive regions 45, 46 illustrated herein, variations thereof, and alternatives thereof, as will be understood by those skilled in the art.
[0061] At block 106, a current signal can be passed between the probe electrode and the plurality of body patch electrodes such that the current signal passes through a predetermined tubular wall region of the wall of the guide sheath. The predetermined tubular wall region can include saline-filled pores through the wall of the guide sheath, and the current signal can pass through the saline-filled pores.
[0062] At block 108, a position of the predetermined tubular wall region may be determined based at least in part on the current signal. A position of the distal end of the guide sheath may be determined based at least in part on a predetermined distance between the predetermined tubular wall region and the distal end of the guide sheath. Additionally or alternatively, the current signal may pass through a conductive band coupled to the wall of the guide sheath at the predetermined tubular wall region. Additionally or alternatively, the current signal may pass through a conductive rivet extending through the wall of the guide sheath at the predetermined tubular wall region. Additionally or alternatively, the current signal may pass through a conductive fiber embedded in the wall of the guide sheath at the predetermined tubular wall region. A position and orientation of the distal portion of the guide sheath may be determined relative to the patient's anatomy. A position of the distal portion of the guide sheath may be determined without requiring an active position sensor on the guide sheath. A position of the distal portion of the guide sheath may be determined without requiring active electrical communication with the guide sheath.
[0063] At block 110, a graphical representation of a distal portion of the guide sheath relative to the patient's anatomy may be generated based at least in part on the locations of the conductive regions.
[0064] The following clauses list non-limiting embodiments of the present disclosure.
[0065] Clause 1. A guide sheath comprising a tubular shaft extending along a longitudinal axis between a proximal end and a distal end, the tubular shaft comprising a lumen through the tubular shaft and a tubular wall surrounding the lumen, a predetermined tubular wall region configured to provide an electrically conductive pathway through a tubular wall of the tubular shaft, the predetermined tubular wall region being disposed proximate to a distal end of the tubular shaft.
[0066] Clause 2. The guide sheath of clause 1, wherein the predetermined tubular wall region is disposed approximately 1 centimeter from the distal end and extends approximately 1 millimeter to 2 millimeters along the tubular shaft.
[0067] Clause 3. A guide sheath as described in clause 1 or 2, wherein the predetermined tubular wall region is configured with pores sized to permit the flow of saline from the lumen through the tubular wall of the tubular shaft.
[0068] Clause 4. A guide sheath as described in any one of clauses 1 to 3, wherein the predetermined tubular wall region comprises a conductive band coupled to the tubular wall of the guide sheath and configured to conduct electrical current between the lumen and an environment external to the tubular shaft.
[0069] Clause 5. A guide sheath as described in any one of clauses 1 to 4, wherein the predetermined tubular wall region is provided with a conductive rivet extending through the tubular wall of the guide sheath.
[0070] Clause 6. A guide sheath as described in any one of clauses 1 to 5, wherein the predetermined tubular wall region includes conductive fibers embedded in the tubular wall of the guide sheath and configured to conduct electric current between the lumen and an environment external to the tubular shaft.
[0071] Clause 7. The guide sheath of any one of clauses 1-6, further comprising a handle coupled to a proximal end of the tubular shaft and configured to deflect a distal portion of the tubular shaft.
[0072] Clause 8. The guide sheath of any one of clauses 1 to 7, further comprising an irrigation port configured to provide irrigation fluid to the lumen.
[0073] Clause 9. A guide sheath as described in any one of clauses 1 to 8, wherein the tubular shaft is devoid of an active position sensor.
[0074] Clause 10. A guide sheath as described in any one of clauses 1 to 9, wherein the guide sheath is devoid of electrical ports.
[0075] Clause 11. A guide sheath as described in any one of clauses 1 to 10, wherein the tubular shaft comprises a plurality of predetermined tubular wall regions including a predetermined tubular wall region, each of the plurality of predetermined tubular wall regions being disposed at a respective predetermined length from the distal end of the tubular shaft, and each of the plurality of predetermined tubular wall regions providing a conductive path through the tubular wall of the tubular shaft.
[0076] Clause 12. An impedance based tracking system comprising: a guide sheath comprising a first tubular shaft having a lumen passing therethrough and a predetermined tubular wall region disposed near a distal end of the first tubular shaft, the predetermined tubular wall region being configured to provide a conductive path through the predetermined tubular wall region; a medical probe comprising a second tubular shaft configured to be translated through the lumen of the first tubular shaft and comprising a tracking electrode coupled to the second tubular shaft; a plurality of body patch electrodes configured to contact a patient's skin; and a control unit configured to determine a position of the predetermined tubular wall region based at least in part on an electrical signal between the tracking electrode and the plurality of body patch electrodes.
[0077] Clause 13. The impedance-based tracking system of clause 12, wherein the control unit is further configured to determine a position of a distal end of the first tubular shaft of the guide sheath based at least in part on the position of the predetermined tubular wall region.
[0078] Clause 14. The impedance-based tracking system of clause 12 or 13, wherein the control unit is further configured to determine a position and orientation of the distal portion of the guide sheath relative to the patient's anatomy.
[0079] Clause 15. An impedance-based tracking system as described in any one of clauses 12-14, wherein the predetermined tubular wall region is configured with pores sized to permit flow of saline from the lumen through the wall of the first tubular shaft.
[0080] Clause 16. The impedance-based tracking system of clause 15, further comprising an irrigation source configured to provide saline through the lumen and pores of the first tubular shaft.
[0081] Clause 17. An impedance-based tracking system as described in any one of clauses 12 to 16, wherein the predetermined tubular wall region comprises a conductive band coupled to the wall of the first tubular shaft and configured to conduct an electric current between the lumen and an environment external to the first tubular shaft.
[0082] Clause 18. An impedance-based tracking system as described in any one of clauses 12-17, wherein the predetermined tubular wall region comprises a conductive rivet extending through the wall of the first tubular shaft.
[0083] Clause 19. An impedance-based tracking system as described in any one of clauses 12 to 18, wherein the predetermined tubular wall region includes conductive fibers embedded in the wall of the first tubular shaft and configured to conduct an electric current between the lumen and an environment external to the first tubular shaft.
[0084] Clause 20. An impedance-based tracking system as described in any one of clauses 12 to 19, wherein the predetermined tubular wall region is located about 1 centimeter to about 3 centimeters from the distal end of the first tubular shaft and extends a length of about 1 millimeter to about 2 millimeters along the first tubular shaft.
[0085] Clause 21. An impedance-based tracking system as described in any one of clauses 12 to 20, comprising a handle coupled to a proximal end of the first tubular shaft and configured to deflect a distal portion of the first tubular shaft.
[0086] Clause 22. An impedance-based tracking system as described in any one of clauses 12 to 21, wherein the guide sheath comprises an irrigation port configured to provide irrigation fluid to the lumen.
[0087] Clause 23. An impedance-based tracking system as described in any one of clauses 12 to 22, wherein the first tubular shaft is devoid of an active position sensor.
[0088] Clause 24. An impedance-based tracking system as described in any one of clauses 12 to 23, wherein the guide sheath is devoid of electrical ports.
[0089] Clause 25. An impedance-based tracking system as described in any one of clauses 12 to 24, wherein the first tubular shaft comprises a plurality of conductive regions including a conductive region, each of the plurality of conductive regions being disposed at a respective predetermined length from the distal end of the first tubular shaft, and each of the plurality of conductive regions providing a conductive path between a lumen of the first tubular shaft and an environment external to the first tubular shaft.
[0090] Clause 26. An impedance-based tracking system as described in any one of clauses 12 to 25, wherein the medical probe further comprises one or more electrodes configured to sense intracardiac electrogram signals.
[0091] Clause 27. An impedance-based tracking system described in any one of clauses 12 to 26, wherein the medical probe further comprises one or more electrodes configured to provide an electrical signal for radio frequency ablation.
[0092] Clause 28. An impedance-based tracking system described in any one of clauses 12 to 27, wherein the medical probe further comprises one or more electrodes configured to provide an electrical signal for ablation by electroporation.
[0093] Clause 29. An impedance-based tracking system as described in any one of clauses 12 to 28, wherein the medical probe comprises an expander.
[0094] Clause 30. A method of impedance tracking of a guide sheath within a patient, the method comprising: passing a current signal between a probe electrode of a medical probe and a plurality of body patch electrodes, the probe electrode being disposed within a lumen of a guide sheath within the patient, the plurality of body patch electrodes being in contact with skin of the patient; and determining a position of a distal portion of the guide sheath based at least in part on the current signal.
[0095] Clause 31. The method of clause 30, further comprising detecting translation of the probe electrode through a lumen adjacent a predetermined tubular wall region of a wall of the guide sheath.
[0096] Clause 32. The method of clause 31, further comprising: determining a position of the predetermined tubular wall region; and determining a position of the distal end of the guide sheath based at least in part on a predetermined distance between the predetermined tubular wall region and the distal end of the guide sheath.
[0097] Clause 33. The method of clause 31 or 32, further comprising passing a current signal between the probe electrode and the plurality of body patch electrodes such that the current signal passes through a predetermined tubular wall region of the wall of the guide sheath.
[0098] Clause 34. The method of clause 33, further comprising passing the electrical current signal through a saline-filled pore through a wall of the guide sheath at a predetermined tubular wall region.
[0099] Clause 35. The method of clause 33 or 34, further comprising passing the current signal through a conductive band coupled to the wall of the guide sheath at the predetermined tubular wall region.
[0100] Clause 36. The method of any one of clauses 33-35, further comprising passing the current signal through a conductive rivet extending through the wall of the guide sheath at the predetermined tubular wall region.
[0101] Clause 37. The method of any one of clauses 33 to 36, further comprising passing the current signal through conductive fibers embedded in the wall of the guide sheath at the predetermined tubular wall region.
[0102] Clause 38. The method of any one of clauses 30-37, further comprising determining a position and orientation of a distal portion of the guide sheath relative to the patient's anatomy.
[0103] Clause 39. The method of any one of clauses 30-38, further comprising determining the position of the distal portion of the guide sheath without requiring an active position sensor on the guide sheath.
[0104] Clause 40. The method of any one of clauses 30-39, further comprising determining a position of a distal portion of the guide sheath without requiring active electrical communication with the guide sheath.
[0105] Although exemplary embodiments of the subject matter encompassed by the present invention have been shown and described, further adaptations of the methods and systems described herein can be achieved by appropriate modifications without departing from the scope of the claims. Moreover, where the above methods and steps show certain events occurring in a particular order, it is intended that the specific steps need not be performed in the order described, but rather in any order as long as the steps enable the embodiments to function for their intended purpose. Thus, to the extent there are variations of the invention that are within the spirit of the disclosure or equivalent to the invention found in the claims, this patent is intended to cover those variations as well. Some such modifications should be apparent to those skilled in the art. For example, the above examples, embodiments, geometries, materials, dimensions, proportions, steps, etc. are exemplary. Thus, the claims should not be limited to the specific details of structure and operation set forth in the specification and drawings.
[0106] [Embodiment] (1) An impedance-based tracking system, comprising: a guide sheath comprising: a first tubular shaft having a lumen therethrough; and a predetermined tubular wall region disposed near a distal end of the first tubular shaft, the predetermined tubular wall region configured to provide an electrically conductive pathway therethrough; a medical probe comprising a second tubular shaft configured to be translated through the lumen of the first tubular shaft, the medical probe comprising a tracking electrode coupled to the second tubular shaft; a plurality of body patch electrodes configured to contact the patient's skin; and a control unit configured to determine a position of the predetermined tubular wall region based at least in part on electrical signals between the tracking electrode and the plurality of body patch electrodes. (2) The impedance-based tracking system of embodiment 1, wherein the control unit is further configured to determine a position of the distal end of the first tubular shaft of the guide sheath based at least in part on the position of the predetermined tubular wall region. (3) The impedance-based tracking system of embodiment 1, wherein the control unit is further configured to determine a position and orientation of a distal portion of the guide sheath relative to the patient's anatomical structure. (4) The impedance-based tracking system of embodiment 1, wherein the predetermined tubular wall region is configured with pores sized to allow the flow of saline from the lumen through the wall of the first tubular shaft. (5) The impedance-based tracking system of embodiment 1, wherein the predetermined tubular wall region comprises a conductive band coupled to a wall of the first tubular shaft and configured to conduct an electric current between the lumen and an environment external to the first tubular shaft.
[0107] (6) An impedance-based tracking system as described in embodiment 1, wherein the predetermined tubular wall region comprises a conductive rivet extending through a wall of the first tubular shaft. (7) The impedance-based tracking system of embodiment 1, wherein the predetermined tubular wall region includes a conductive fiber embedded in a wall of the first tubular shaft and configured to conduct an electric current between the lumen and an environment external to the first tubular shaft. (8) The impedance-based tracking system of embodiment 1, wherein the predetermined tubular wall region is located about 1 centimeter to about 3 centimeters from the distal end of the first tubular shaft and extends along the first tubular shaft for a length of about 1 millimeter to about 2 millimeters. (9) The impedance-based tracking system of embodiment 1, wherein the guide sheath comprises a handle coupled to a proximal end of the first tubular shaft and configured to deflect a distal portion of the first tubular shaft. (10) An impedance-based tracking system as described in embodiment 1, wherein the guide sheath includes an irrigation port configured to provide irrigation fluid to the lumen.
[0108] (11) The impedance-based tracking system of embodiment 1, wherein the first tubular shaft lacks an active position sensor. (12) An impedance-based tracking system as described in embodiment 1, wherein the guide sheath is devoid of electrical ports. (13) The first tubular shaft has a plurality of conductive regions including the conductive region, each of the plurality of conductive regions is disposed a respective predetermined length from the distal end of the first tubular shaft; An impedance-based tracking system as described in embodiment 1, wherein each of the plurality of conductive regions provides a conductive path between the lumen of the first tubular shaft and an environment external to the first tubular shaft. (14) The impedance-based tracking system of embodiment 1, wherein the medical probe further comprises one or more electrodes configured to sense intracardiac electrogram signals. (15) The impedance-based tracking system of embodiment 1, wherein the medical probe further comprises one or more electrodes configured to provide an electrical signal for ablation.
[0109] (16) The impedance-based tracking system of claim 1, wherein the medical probe comprises an expander. (17) A guide sheath, 1. A guide sheath comprising a tubular shaft extending along a longitudinal axis between a proximal end and a distal end, the tubular shaft comprising a lumen through the tubular shaft and a tubular wall surrounding the lumen, a predetermined tubular wall region configured to provide an electrically conductive pathway through the tubular wall of the tubular shaft, the predetermined tubular wall region being disposed proximate to the distal end of the tubular shaft. (18) The guide sheath of embodiment 17, wherein the predetermined tubular wall region is disposed approximately 1 centimeter from the distal end and extends approximately 1 millimeter to 2 millimeters along the tubular shaft. (19) The guide sheath of embodiment 17, wherein the tubular shaft comprises a plurality of predetermined tubular wall regions including the predetermined tubular wall region, each of the plurality of predetermined tubular wall regions being disposed a respective predetermined length from the distal end of the tubular shaft, and each of the plurality of predetermined tubular wall regions providing a conductive path through the tubular wall of the tubular shaft. (20) A method for impedance tracking of a guide sheath within a patient, comprising: passing a current signal between a probe electrode of a medical probe and a plurality of body patch electrodes, the probe electrode being disposed within the patient within a lumen of the guide sheath and the plurality of body patch electrodes being in contact with the patient's skin; and determining a position of a distal portion of the guide sheath based at least in part on the current signal.
Claims
1. 1. An impedance-based tracking system comprising: a guide sheath comprising a first tubular shaft having a lumen therethrough and a predetermined tubular wall region disposed near a distal end of the first tubular shaft, the predetermined tubular wall region configured to provide an electrically conductive pathway therethrough; a medical probe comprising a second tubular shaft configured to be translated through the lumen of the first tubular shaft, the medical probe comprising a tracking electrode coupled to the second tubular shaft; a plurality of body patch electrodes configured to contact the patient's skin; and a control unit configured to determine a position of the predetermined tubular wall region based at least in part on electrical signals between the tracking electrode and the plurality of body patch electrodes.
2. 2. The impedance-based tracking system of claim 1, wherein the control unit is further configured to determine a position of the distal end of the first tubular shaft of the guide sheath based at least in part on the position of the predetermined tubular wall region.
3. The impedance-based tracking system of claim 1 , wherein the control unit is further configured to determine a position and orientation of a distal portion of the guide sheath relative to the patient's anatomy.
4. 2. The impedance-based tracking system of claim 1, wherein the predetermined tubular wall region is configured with pores sized to allow flow of saline from the lumen through a wall of the first tubular shaft.
5. 2. The impedance-based tracking system of claim 1, wherein the predetermined tubular wall region comprises a conductive band coupled to a wall of the first tubular shaft and configured to conduct an electrical current between the lumen and an environment external to the first tubular shaft.
6. The impedance-based tracking system of claim 1 , wherein the predetermined tubular wall region comprises a conductive rivet extending through a wall of the first tubular shaft.
7. 2. The impedance-based tracking system of claim 1, wherein the predetermined tubular wall region includes conductive fibers embedded in a wall of the first tubular shaft and configured to conduct an electrical current between the lumen and an environment external to the first tubular shaft.
8. 2. The impedance-based tracking system of claim 1, wherein the predetermined tubular wall region is located about 1 centimeter to about 3 centimeters from a distal end of the first tubular shaft and extends a length of about 1 millimeter to about 2 millimeters along the first tubular shaft.
9. 2. The impedance-based tracking system of claim 1, wherein the guide sheath comprises a handle coupled to a proximal end of the first tubular shaft and configured to deflect a distal portion of the first tubular shaft.
10. The impedance-based tracking system of claim 1 , wherein the guide sheath comprises an irrigation port configured to provide irrigation fluid to the lumen.
11. The impedance-based tracking system of claim 1 , wherein the first tubular shaft is devoid of an active position sensor.
12. The impedance-based tracking system of claim 1 , wherein the guide sheath is devoid of electrical ports.
13. the first tubular shaft comprises a plurality of conductive regions including the conductive region; each of the plurality of conductive regions is disposed a respective predetermined length from the distal end of the first tubular shaft; The impedance-based tracking system of claim 1 , wherein each of the plurality of conductive regions provides a conductive path between the lumen of the first tubular shaft and an environment external to the first tubular shaft.
14. The impedance-based tracking system of claim 1 , wherein the medical probe further comprises one or more electrodes configured to sense intracardiac electrogram signals.
15. The impedance-based tracking system of claim 1 , wherein the medical probe further comprises one or more electrodes configured to provide an electrical signal for ablation.
16. The impedance-based tracking system of claim 1 , wherein the medical probe comprises a dilator.
17. A guide sheath, 1. A guide sheath comprising a tubular shaft extending along a longitudinal axis between a proximal end and a distal end, the tubular shaft comprising a lumen through the tubular shaft and a tubular wall surrounding the lumen, a predetermined tubular wall region configured to provide an electrically conductive pathway through the tubular wall of the tubular shaft, the predetermined tubular wall region being disposed proximate to the distal end of the tubular shaft.
18. The guide sheath of claim 17, wherein the predetermined tubular wall region is located approximately one centimeter from the distal end and extends approximately one to two millimeters along the tubular shaft.
19. 18. The guide sheath of claim 17, wherein the tubular shaft comprises a plurality of predetermined tubular wall regions including the predetermined tubular wall region, each of the plurality of predetermined tubular wall regions disposed a respective predetermined length from the distal end of the tubular shaft, and each of the plurality of predetermined tubular wall regions provides an electrically conductive path through the tubular wall of the tubular shaft.
20. 1. A method for impedance tracking of a guide sheath within a patient, comprising: passing a current signal between a probe electrode of a medical probe and a plurality of body patch electrodes, the probe electrode being disposed within the patient within a lumen of the guide sheath and the plurality of body patch electrodes being in contact with the patient's skin; and determining a position of a distal portion of the guide sheath based at least in part on the current signal.