ECG stylet with improved fatigue and crush resistance

Abstract

A stylet for positioning a catheter within a patient's vasculature is disclosed. The stylet may include an ECG sensor assembly having electrodes, a magnetic assembly for generating a magnetic field, a core wire, and a coil defining a lumen. A portion of the core wire may be disposed within the lumen of the coil. An intravascular catheter is disclosed that includes a stylet disposed within a lumen of the catheter. A method for positioning a catheter within a patient's superior vena cava is provided. The method includes inserting a stylet within a lumen of the catheter, connecting the ECG sensor assembly to an ECG system, advancing the catheter along the patient's vasculature, ceasing advancement of the catheter when an ECG signal indicates that a tip of the stylet is disposed within the superior vena cava, and removing the stylet from the lumen of the catheter.

Description

[Technical field]

[0001] The present disclosure relates to an ECG stylet with improved fatigue and crush resistance. [Background technology]

[0002] Various intravascular devices, including but not limited to CVCs (central venous catheters), may be inserted into a patient's vasculature to detect and / or treat various health problems. CVCs are intravascular devices that include any catheter designed to utilize a central vein (e.g., the subclavian vein and superior vena cava) or right heart chamber for delivery and / or withdrawal of blood, blood products, therapeutic agents, and / or diagnostic agents. CVCs also include catheters that are inserted into a central vein or right ventricle for acquisition of hemodynamic data. Standard central venous catheters, dialysis catheters, PICC (percutaneously introduced central catheter) lines, and right heart catheters for intravenous access are examples of CVCs. In some applications, an intravascular device, such as a CVC (central venous catheter), may be inserted into a patient's SVC (superior vena cava).

[0003] Specific location of intravascular devices is critical and can have a significant impact on patient health. For example, an ideally placed CVC (central venous catheter) provides reliable vascular access with optimal therapy delivery while minimizing short-term and long-term complications.

[0004] Although CVCs have been used for many years, determining the location of the tip of a CVC has always been problematic. Furthermore, in addition to needing to know where the tip is during initial placement, CVCs may migrate or move after initial placement and may require repositioning. Thus, operators must monitor or periodically recheck the location of the tip.

[0005] ECG (electrocardiogram) based guidance can be used as a positioning technique for catheter tip placement and confirmation. The cardiac electrical conduction system generates specific electrical signals, electrical energy distributions and their behavior that are indicative of specific locations within the thoracic cavity and / or specific cardiac functions or conditions. When measured intravascularly or intravascularly, i.e. from within the blood vessels or from within the heart, specific parameters of cardiac electrical activity can be used to identify specific locations and / or normal or abnormal functional conditions in the cardiovascular system.

[0006] Some catheter guidance systems may also include a TLS (tip location / navigation system) modality for magnetic-based tracking of the catheter tip. Such systems may include a magnetic element coupled to a stylet within a catheter that is placed within the patient's vasculature. In some instances, the magnetic element may become decoupled from the stylet, exposing the patient to particulate emboli.

[0007] Disclosed herein are new devices and methods for improving the reliability of stylets for use with magnetic-based tracking systems, thereby reducing the likelihood of magnetic elements becoming detached from the stylet, as well as improving patient safety from exposure to particulate emboli. Summary of the Invention

[0008] Disclosed herein is a stylet for positioning a catheter within a patient's vasculature. The stylet includes an ECG sensor assembly having electrodes extending from a proximal end to a distal end of the stylet, the proximal end configured to couple to an ECG sensor. The stylet further includes a magnetic assembly disposed along a distal portion of the stylet, the magnetic assembly generating a magnetic field. The stylet further includes a core wire extending proximally from the magnetic assembly and a coil defining a lumen. The coil extends along a distal portion of the stylet, the distal portion of the core wire being disposed within the lumen of the coil.

[0009] The stylet may be configured to be inserted into the lumen of the catheter, and the stylet may also be configured to position the catheter within the patient's superior vena cava. The electrode may include a core wire and a coil.

[0010] The magnetic assembly may include a plurality of magnet elements disposed within the lumen of the coil. Each of the magnet elements may have a cylindrical shape, and the magnet elements may be disposed end-to-end within the lumen. One or more of the magnet elements may be attached to the coil.

[0011] The coil may be attached to and electrically coupled to the core wire. The coil may include a coil member forming a helix. The coil member may have a rectangular cross-sectional shape having a width and a thickness.

[0012] The coil may include a second coil member forming at least a second helix, and the first coil member and the second coil member may cross one another. In some embodiments, the coil includes at least three coil members defining a braided or woven structure. The stylet may include a sheath extending along a distal portion of the stylet, and the sheath may cover the coil.

[0013] The core wire may have a first thickness extending along a proximal portion of the core wire and a second thickness extending along a distal portion of the core wire, the second thickness being less than the first thickness. The core wire may include a taper extending between the first and second thicknesses. The distal portion of the core wire may be circular, and in some embodiments, the distal portion of the core wire extends along the magnet assembly.

[0014] The stylet may include a distal tip member coupled to the coil, the distal tip member may be formed from an electrically conductive material, and the distal tip member may also be electrically coupled to the coil. A distal portion of the core wire may extend distally beyond the magnet assembly, and the core wire may be electrically coupled to the magnet assembly.

[0015] The stylet may further include a handle attached to the core wire at the proximal end of the core wire, and the stylet may also further include a tether coupled to the core wire at the proximal end of the core wire, the tether including an electrical conductor that forms part of the electrode.

[0016] The stylet may have a width of 0.01 mm to 1 mm and a thickness of 0.005 mm to 1 mm. The helical pitch may be 0.01 mm to 10 mm. Also disclosed herein is an intravascular catheter assembly. The catheter assembly includes a catheter having a lumen and a stylet disposed within the lumen of the catheter. The stylet includes an ECG sensor assembly having electrodes extending from a proximal end to a distal end of the stylet, the proximal end configured to couple to the ECG sensor. The stylet further includes a magnetic assembly disposed along a distal portion of the stylet, the magnetic assembly generating a magnetic field. The stylet further includes a core wire extending proximally from the magnetic assembly and a coil defining a lumen. The coil extends along a distal portion of the stylet, the distal portion of the core wire being disposed within the lumen of the coil.

[0017] The catheter assembly may be configured to place a tip of the catheter within the patient's superior vena cava, and a distal end of the catheter may be substantially coextensive with a distal end of the stylet.

[0018] The catheter assembly may include a preformed curve along a distal portion of the catheter assembly, and the preformed curve may be defined by a preformed curve of the stylet.

[0019] The coil of the stylet may be disposed entirely within the lumen, and the sheath of the stylet may be disposed entirely within the lumen. Also disclosed herein is a method of placing a catheter in a patient's superior vena cava. The method includes inserting a stylet into a lumen of the catheter. The stylet includes an ECG sensor assembly including electrodes extending from a proximal end to a distal end of the stylet, the electrodes configured to transmit ECG signals to an ECG system. The stylet further includes a magnetic assembly that generates a magnetic field and an elongated coil that extends proximally from the distal end of the stylet. The coil defines a lumen that houses the magnetic assembly.

[0020] The method further includes connecting the ECG sensor assembly to an ECG system; advancing the catheter along the patient's vasculature; ceasing advancement of the catheter when the ECG signal indicates that the tip of the stylet is positioned within the superior vena cava; and removing the stylet from the lumen of the catheter.

[0021] In some embodiments of the method, the stylet includes a handle and the method further includes manually applying a torque to the handle to rotate the stylet within the catheter. The method may further include manually applying a torque to the handle and the catheter to rotate the catheter within the vasculature.

[0022] The method may further include aligning a distal tip of the stylet with a distal tip of the catheter and transmitting an ECG signal along a conductive coil member of the coil. These and other features of the concepts provided herein will become more apparent to those of ordinary skill in the art upon consideration of the following description and accompanying drawings, which describe in more detail certain embodiments of such concepts.

[0023] The present disclosure will now be described in more detail by reference to certain embodiments that are illustrated in the accompanying drawings. It should be understood that these drawings depict only typical embodiments of the invention and therefore should not be considered as limiting its scope. Exemplary embodiments of the invention will be described and explained with additional specificity and detail using the accompanying drawings. [Brief description of the drawings]

[0024] [Figure 1] 1 is a simplified diagram of a patient and a catheter inserted into the patient with the aid of an integrated system, according to some embodiments. [Diagram 2] 2 is a perspective view of a stylet used in connection with the integrated system of FIG. 1 in accordance with some embodiments. [Figure 3A] 3 is a side view of the catheter engaging section of the stylet of FIG. 2 in accordance with some embodiments. [Figure 3B] FIG. 13 is a detailed side view of a portion of the catheter engagement section at a junction, according to some embodiments. [Figure 3C] 13A is a side cross-sectional view of a transition portion of the catheter engaging section, according to some embodiments. [Figure 3D] 13A is a side cross-sectional view of a distal tip portion of the catheter engaging section, according to some embodiments. [Figure 4] A catheter assembly including the catheter and stylet of FIG. 1, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Before disclosing some specific embodiments in more detail, it should be understood that the specific embodiments disclosed herein do not limit the scope of the concepts presented herein. It should also be understood that a specific embodiment disclosed herein may have features that can be easily separated from the specific embodiment and can be optionally combined or substituted with features of any of the other embodiments disclosed herein.

[0026] With regard to the terms used herein, it should also be understood that each term is intended to describe certain embodiments and does not limit the scope of the concepts presented herein. Ordinal numbers (e.g., first, second, third, etc.) are generally used to distinguish or identify different features or steps among a group of features or steps, and do not impose any order or numerical limitations. For example, the "first", "second", and "third" features or steps do not necessarily have to appear in this order, and a particular embodiment including such features or steps is not necessarily limited to three features or steps. Designations such as "left", "right", "up", "down", "front", "rear", etc. are used for convenience and do not imply any particular fixed position, orientation, or direction, for example. Rather, such designations are used to indicate relative positions, orientations, or directions, for example. Unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" include the plural.

[0027] The directional terms "proximal" and "distal" are used herein to refer to opposing locations on a medical device. The proximal end of the device is defined as the end of the device that is closest to an end user and farther from the patient when the device is in use by the end user. The distal end is the end opposite the proximal end along the length of the device, or the end that is farthest from the end user and closer to the patient.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. FIG. 1 illustrates various features of a catheter placement system (system) 10. System 10 generally relates to a catheter placement system configured to accurately place a catheter within the vasculature of a patient 70. Catheter placement system 10 uses three modalities to improve catheter placement accuracy: 1) ultrasound-assisted guidance for introducing the catheter into the patient's vasculature, 2) a TLS (tip location / navigation system) for magnetic-based tracking of the catheter tip, and 3) ECG signal-based catheter tip guidance. The combination of the above three modalities enables catheter placement system 10 to place a catheter within the patient's vasculature with a relatively high level of accuracy, i.e., placement of the distal tip of the catheter at a predetermined desired location. Furthermore, with ECG-based guidance of the catheter tip, accurate tip placement may be confirmed without the need for a confirmatory x-ray. This therefore reduces patient exposure to potentially harmful x-rays, the cost and time associated with transporting the patient 70 to and from the x-ray department, costly and inconvenient catheter repositioning procedures, etc.

[0029] The combined features of the system 10 are integrated into a single apparatus for use by a physician placing the catheter 72. The integration of the three modalities into a single device simplifies the catheter placement process and allows for relatively fast catheter placement. The integrated catheter placement system 10 allows ultrasound, TLS, and ECG activity to be observed from a single display of the integrated system. Several systems and methods of TLS and ECG-based guidance are described in U.S. Pat. No. 9,220,432, entitled "Method and system of utilizing ECG signal for central venous catheter tip positioning," and U.S. Pat. No. 9,999,371, entitled "Integrated system for intravascular placement of a catheter," each of which is incorporated by reference in its entirety into this application. Further disclosure of stylets and catheters for use with TLS systems and ECG-based guidance may be found in the following U.S. patents: Nos. 8,388,541, 8,781,555, 8,784,336, 8,849,382, 9,636,031, 9,649,048, and 9,901,714, each of which is incorporated by reference in its entirety into this application.

[0030] FIG. 1 further illustrates various components of the system 10, including the console 20, the display 30, the probe 40, and the sensor 50. FIG. 1 illustrates the general relationship of the components to a patient 70 during a procedure in which a catheter 72 is placed into the patient's vasculature through a skin insertion site 73. The catheter 72 generally includes a proximal portion 74 that remains outside the patient 70 and a distal portion 76 that resides within the patient's vasculature after placement is complete. The system 10 is used to ultimately position the distal tip 76A of the catheter 72 at a desired location within the patient's vasculature. In some embodiments, the desired location of the catheter distal tip 76A is proximate the patient's heart, such as the lower one-third (1 / 3) portion of the SVC (superior vena cava). Equivalently, the system 10 may be used to place the catheter distal tip 76A at other locations. The catheter proximal portion 74 further includes a hub 74A. The hub 74A provides fluid communication between one or more lumens of the catheter 72 and one or more extension legs 74B extending proximally from the hub 74A.

[0031] The stylet 130 is removably loaded into the catheter 72 and used during insertion to position the catheter's distal tip 76A at a desired location within the patient's vasculature. The stylet 130, in one embodiment, may be pre-loaded within the lumen of the catheter 72 such that its distal end 130B is substantially flush with or co-terminal with the catheter opening at its distal end 76A. It should be noted that while described herein as a stylet, in other embodiments, a guidewire or other catheter guiding device may incorporate the principles of the embodiments described herein.

[0032] FIG. 2 illustrates the stylet 130 removed from the catheter 72. Various details of the stylet 130 are described below with reference to FIG. 2. As shown, the stylet 130 defines a proximal end 230A and a distal end 230B and includes an ECG sensor assembly 210 and a magnetic assembly 211. A connector 232 is included at the proximal end 230A, and a tether 134 extends distally from the connector 232 and is attached to a handle 236. A core wire 238 extends distally from the handle 236. Each of the assemblies and components of the stylet 130 are described in detail below.

[0033] The handle 236 is positioned to allow for insertion / removal of the stylet 130 from the catheter 72. In embodiments in which the corewire 238 is rotatable, the handle 236 further assists in navigating the catheter distal portion through the vasculature of the patient 70 by allowing the corewire 238 to rotate within the lumen of the catheter 72.

[0034] The handle 236 is attached to the distal end of the tether 134. In this embodiment, the tether 134 is a flexible shielded cable housing one or more conductors 234 (e.g., wires) electrically connected to both the core wire 238 and the connector 232. The tether 134 thus forms a conductive path from a distal portion of the core wire 238 to the tether connector 232 at the proximal end 230A of the stylet 130. The connector 232 may be configured for operative connection to a TLS sensor 50 on the patient's chest to assist in navigating the catheter distal tip 76A to a desired location within the patient's vasculature. A catheter engaging section 233 of the stylet 130 extends between the distal end 230B and the handle 236.

[0035] 3A-3D show details of the catheter engaging section 233 of the stylet 130. FIG. 3A shows a side view of the catheter engaging section 233. As shown in FIG. 3A, the catheter engaging section 233 includes a proximal portion 301 and a distal portion 302. The proximal portion 301 extends distally from the handle 236 to a junction point 305, and the distal portion 302 extends distally from the junction point 305 to the distal end 230B. The distal portion 302 includes a distal tip portion 306 extending proximally from the distal end 230B and a transition portion 304 extending distally from the junction point 305.

[0036] As described above, the stylet 130 includes a core wire 238 that defines an elongate shape that extends distally from the handle 236 along the proximal portion 301 and at least partially along the distal portion 302. The coil 320 and sheath 330 extend along the distal portion 302, as described in more detail below. The core wire 238 is formed from a suitable stylet material, including stainless steel or, in one embodiment, a shape memory material, such as a nickel- and titanium-containing alloy commonly known as "nitinol." Although not described herein, in some embodiments, the stylet 130 may include one or more pre-formed (e.g., curved) configurations along the catheter-engaging section 233 to bias a distal portion of the catheter 72 into a similar corresponding pre-formed configuration. In other embodiments, the core wire 238 does not include a pre-form.

[0037] Figure 3B is a detailed view of catheter-engaging section 233 at junction 305. As shown in Figure 3B, corewire 238 extends proximally from junction 305 having a first cross-sectional diameter 311. Coil 320 and sheath 330 extend distally from junction 305. As shown in Figure 3C, a distal portion of corewire 238 extends distally from junction 305 and is disposed within lumen 327 of coil 320. In some embodiments, sheath 330 extends proximally from junction 305 to cover at least a portion of corewire 238.

[0038] The coil 320 extends along the distal portion 302 from the junction 305 to the distal end 230B. The coil 320 defines the flexibility and stiffness characteristics of the distal portion 302 such that the stylet 130 follows the curved path of the vasculature without damaging the inner wall of the vasculature. The coil 320 may also define the robustness and / or fatigue resistance characteristics of the distal portion 302. In other words, the coil 320 may define the reliability of the stylet 130 against breakage during use. More specifically, the coil 320 may prevent breakage of the distal portion 302 when the distal portion 302 is bent one or more times during use.

[0039] 3B and 3C, the coil 320 is formed from coil members 322. In some embodiments, the coil 320 may include two or more coil members 322. The structural characteristics (i.e., cross-sectional shape and material) of the coil members 322 may at least partially define the flexibility and / or robustness of the distal portion 302. For example, a coil member 322 having a thicker cross-section may define the flexibility and / or robustness of the distal portion 302 less than a coil member 302 having a thinner (i.e., less thick) cross-section. The cross-sectional shape of the coil members 322 may be circular or non-circular. In the illustrated embodiment, the coil members have a rectangular cross-sectional shape having a width 323 and a thickness 324. In the illustrated embodiment, the width 323 of the coil members 322 may be about 0.01 mm to 0.5 mm. In other embodiments, width 323 may be about 0.01 mm to 0.3 mm, 0.05 mm to 0.3 mm, 0.1 mm to 0.3 mm, or 0.01 mm to 1 mm. In the illustrated embodiment, thickness 324 of coil member 322 may be about 0.005 mm to 0.3 mm. In other embodiments, thickness 324 may be about 0.01 mm to 0.3 mm, 0.05 mm to 0.3 mm, 0.05 mm to 0.2 mm, or 0.01 mm to 1 mm. In some embodiments, coil member 322 may comprise a circular shape. In such embodiments, the diameter may be about 0.005 mm to 0.3 mm. In other embodiments, the diameter may be about 0.01 mm to 0.3 mm, 0.05 mm to 0.3 mm, or 0.05 mm to 0.2 mm. In some embodiments, coil member 322 may be formed from a plurality of wire filaments forming a cable, such as, for example, a braided cable.

[0040] The coil 320 also defines a pitch 325, i.e., the spacing between adjacent turns of the coil 320. In some embodiments, the coil 320 may be configured such that the turns of the coil 320 are disposed directly adjacent to one another, i.e., adjacent turns contact one another. In other embodiments, the coil 320 may be configured to define a space or separation between adjacent turns. In some embodiments, the pitch 325 of the coil 320 may be between about 0.01 mm and 10 mm. In other embodiments, the pitch 325 may be between about 0.01 mm and 1 mm, between 0.01 mm and 0.5 mm, or between 0.1 mm and 0.3 mm.

[0041] In some embodiments, the width 323 and / or pitch 325 of the coil 320 may vary along the distal portion 302, i.e., the length of the coil 320. In some embodiments, the width 323 and / or pitch 325 may be related to one another. For example, a longer width 323 may define a longer pitch 325 and a shorter width 323 may define a shorter pitch 325. As can be understood by one of ordinary skill in the art, the width 323 in combination with the pitch 325 may at least partially, and in some embodiments substantially, define the flexibility and / or stiffness of the stylet 130 along the distal portion 302. As the distal portion 302 advances along the vasculature, the distal portion 302 may have a curved shape with different bend radii. For example, the bend radius along the distal tip portion 306 may be smaller than the bend radius along the transition portion 304. Thus, it may be advantageous for the coil 320 to have a shorter width 323 and corresponding shorter pitch 325 along the distal tip portion 306 than the transition portion 304, thereby defining greater flexibility and / or stiffness along the distal tip portion 306. By varying the width 323 and / or pitch 325 along the distal portion 302, stiffness, flexibility, and stiffness may be optimized along the distal portion 302. Similarly, stiffness, flexibility, and stiffness may be defined by varying the width 323 of the coil member 322. Further discussion of pitch variations and width variations is provided below with reference to FIG.

[0042] In the illustrated embodiment, the coil 320 includes a single coil member 322 forming a single helix. In other embodiments, the coil 320 may include two, three, four, or more coil members 322 arranged in a helical orientation. In the illustrated embodiment, the single coil member 322 defines a single coil layer. In other embodiments, two or more coil members 322 may be co-wound with each other to define a single coil layer. In other embodiments, two or more coil members 322 may be co-wound or counter-wound with each other to define more than one layer. In some embodiments, three or more coil members 322 may be arranged to define a braided or woven structure of the coil 320.

[0043] The coil member 322 may be formed from a metallic material, such as stainless steel or Nitinol (see above). In some embodiments, one or more of the coil members 322 may be formed from a polymeric material. In the illustrated embodiment, the coil 320 may be configured to conduct electricity from a proximal end to a distal end of the coil 320.

[0044] The coil 320 is physically coupled to the core wire 238. The coupling between the coil 320 and the core wire 238 may define an electrical connection between the coil 320 and the core wire 238. In the illustrated embodiment, the coil 320 may be attached to the core wire 238 by a weld 329 at a proximal end of the coil 320. In some embodiments, the coupling may include a radially clamping force of the coil 320 relative to the core wire 238, as defined by the interfering dimensions. In other words, in a free state, the inner diameter of the coil 320 may be less than the first diameter 311 of the core wire 238 such that the coil 320 exerts a radially inward clamping force on the core wire 238 when assembled, i.e., when the core wire 238 is disposed within the lumen 327 of the coil 320. In other embodiments, the coil 320 may be attached to the core wire 238 by an adhesive. As can be appreciated by one of ordinary skill in the art, coil 320 may be attached to core wire 238 at one or more other locations along the overlapping lengths of core wire 238 and coil 320 by any other suitable attachment method.

[0045] FIG. 3C shows a side view of the transition section 304 of the distal portion 302 with portions of the coil 320 and sheath 330 shown in cross section. As described above, the distal portion of the core wire 238 is disposed within the lumen 327 of the coil 320. The diameter of the core wire 238 may transition distally along the distal portion from a first diameter 311 to a second diameter 312. In the illustrated embodiment, the transition may be defined by a taper 313. In some embodiments, the flexibility and / or stiffness of the distal portion 302 may be defined by a combination of the bending stiffness of the core wire 238 along the transition section 304 and the bending stiffness of the coil 320. As can be appreciated by one of ordinary skill in the art, the stiffness of the core wire 238 decreases with a decreasing diameter of the core wire 238. In other words, the stiffness of the catheter-engaging section 233 may gradually decrease along the transition section 304. The first diameter 311 of the core wire 238 may be about 0.01 mm to 0.5 mm. In other embodiments, the first diameter 311 may be about 0.01 mm to 0.3 mm, 0.05 mm to 0.3 mm, or 0.1 mm to 0.3 mm. Similarly, the second diameter 312 may be about 0.01 mm to 0.5 mm. In other embodiments, the second diameter 312 may be about 0.01 mm to 0.3 mm, 0.05 mm to 0.3 mm, or 0.1 mm to 0.3 mm. The longitudinal taper length 314 of the taper 313 may be about 3 mm to 30 mm. In other embodiments, the taper length 314 may be about 10 mm to 30 mm, 20 mm to 30 mm, or 23 mm to 27 mm.

[0046] The sheath 330 is disposed along the exterior of the coil 320 from the junction 305 to the distal end 230B. The sheath 330 may provide a smooth and / or low friction exterior surface of the distal portion 302 to allow the distal portion 302 to be inserted into the catheter 72. The sheath 330 may be formed from an extruded tube into which the coil 320 is inserted during assembly. In some embodiments, the sheath material may be applied to the coil 320 in a liquid state such that the sheath 330 is formed upon curing / solidification of the sheath material. In other embodiments, the sheath 330 may be formed from a shrinkable tube. In such embodiments, the assembly process may include placing the coil 320 within a shrinkable tube and then shrinking the shrinkable tube onto the coil 320. In still other embodiments, the sheath 330 may be formed from a tape wrapped around the coil 320. The sheath material may include polyethylene, polypropylene, polytetrafluoroethylene, polyimide, or any other suitable polymeric material. In some embodiments, the sheath 330 may contribute to the stiffness of the distal portion 302. For example, the sheath 330 may enable the preform shape of the distal portion 302 to be defined.

[0047] 3B illustrates a sheath outer diameter that is larger than the first diameter 311 proximal to the sheath 330, in some embodiments, the catheter engaging section 233 may include a substantially constant cross-sectional size (e.g., diameter) beyond the junction point 305. The outer diameter of the sheath 330 may be substantially equal to the first diameter 311 of the core wire 238. In such a case, the first diameter 311, the taper 313, the coil member thickness 324, and the sheath thickness 334 may be sized and / or longitudinally disposed to define a substantially constant outer diameter beyond the junction point 305.

[0048] 3D is a cross-sectional detail view of the distal tip portion 306. As described above, the stylet 130 includes a magnetic assembly 211 disposed along the distal tip portion 306 proximate the distal end 230B. The magnetic assembly 211 may be configured for use during a TLS mode of the system 10. The magnetic assembly 211 includes a plurality of magnetic elements 344 disposed within the lumen 327 of the coil 320. The plurality of magnetic elements 344 may form a linear array of magnetic elements 344 extending proximally from the distal end 230B. In the illustrated embodiment, the magnetic elements 344 include 20 ferromagnetic magnets in a solid cylindrical shape stacked end-to-end such that the end faces 346 of the magnetic elements 144 are disposed adjacent to one another. However, in other embodiments, the magnetic elements 344 may differ from this design not only in shape but also in composition, number, size, magnetic type, and location within the lumen 327 and along the distal tip portion 306. One or more magnetic elements 344 may be attached to the coil 320 such that longitudinal displacement of the magnetic elements 344 with respect to the lumen 327 may be limited.

[0049] In some embodiments, the magnetic assembly 211 may have a space or separation 345 between adjacent end faces 346 of the magnetic elements 344. The space 345 may allow for reduced stress and / or strain on the coil 320 and / or sheath 330 when the distal tip portion 306 is positioned in a curved shape. Reduced stress or strain along the distal tip portion 306 may improve the reliability of the stylet 130 by preventing breakage of the stylet 130 along the distal tip portion 306. In some embodiments, the space 345 may be defined by a central extension 347 extending from one or both end faces 346 of one or more magnetic elements 344. In some embodiments, the central extension 347 may have a rounded or chamfered shape on one or both end faces 346.

[0050] The magnetic element 144 is positioned along the distal tip portion 306 such that the position of the stylet distal end 230B is observable by a TLS sensor 50 (see FIG. 1 ) positioned on the patient's chest. The TLS sensor 50 is configured to detect the magnetic field of the magnetic element 344 as the stylet 130 is advanced through the patient's vasculature with the catheter 72. In this manner, a physician placing the catheter 72 can generally determine the position of the catheter distal end 76A within the patient's vasculature, as well as detect when catheter malpositioning is occurring, such as, for example, advancement of the catheter along an undesirable vein.

[0051] As shown in FIG. 3D, the stylet 130 may include a distal tip member 350 disposed at the distal end 230B. The distal tip member 350 may extend beyond the distal ends of one or both of the coil 320 and the sheath 330. The distal tip member 350 may be attached to the coil 320. The distal tip member 350 may also be electrically coupled to the coil 320. The distal tip member 350 is formed from a conductive material. In some embodiments, the distal tip member 350 may be formed from a metallic material, such as stainless steel or any other suitable metallic material. In such embodiments, the distal tip member 350 may be fused to the coil 320. In other embodiments, the distal tip member 350 may be formed from a non-metallic material having conductive properties. For example, the distal tip member 350 may include a conductive epoxy. The distal tip member 350 may at least partially define and / or increase the conductive surface of the distal end 230B of the stylet 130 to improve the ability of the stylet 130 to detect ECG signals.

[0052] The connector 232, the conductor 234, the core wire 238, the coil 320, and the distal tip member 350 are all in electrical communication with one another to define the ECG sensor assembly 210, which includes a conductive path for transmitting ECG signals from the distal end 230B to the proximal end 230A of the stylet 130. The ECG sensor assembly 210 thus defines electrodes that allow ECG signals to be transmitted from the bodily fluids of the patient 70 (e.g., blood in the superior vena cava) to the ECG sensor 50. The ECG sensor assembly 210 allows the stylet 130, which is disposed within the lumen of the catheter 72 during insertion, to be used to detect intra-atrial ECG signals generated by the SA or other nodes of the patient's heart. This allows the distal tip 76A of the catheter 72 to be navigated to a predetermined location within the vasculature proximate to the patient's heart. The ECG sensor assembly 210 thus serves as an aid in confirming proper placement of the catheter distal tip 76A.

[0053] In some embodiments, the core wire 238 may extend distally to the distal end 230B. In such embodiments, a portion of the core wire 238 may be disposed between the magnetic element 344 and the inner lumen surface of the coil 320. The core wire 238 is electrically coupled directly to the distal tip member 350, and therefore, the core wire 238 does not need to be electrically coupled to the coil 320.

[0054] As discussed above in connection with FIG. 3B, the pitch of the coil 320 and / or the width of the coil member 322 may vary along the distal portion 302. Thus, in some embodiments, the pitch may vary along the distal portion 302 between a pitch 325 adjacent the junction 305 as shown in FIG. 3B and a pitch 335 adjacent the distal end 230B as shown in FIG. 3D. In some embodiments, the pitch 335 may be less than the pitch 325 so as to define a flexibility and / or stiffness of the stylet 130 at the distal end 230B that is greater than a flexibility and / or stiffness of the stylet 130 adjacent the junction 305. In some embodiments, the pitch 335 may increase along the distal tip portion 306, and the pitch 325 may gradually change along the transition portion 304 toward the pitch 335.

[0055] Similarly, in some embodiments, the width of the coil member 322 may vary along the length of the distal portion 302 between a width 323 adjacent the junction 305, as shown in FIG. 3B, and a width 333 adjacent the distal end 230B, as shown in FIG. 3D. In some embodiments, the width 333 may be less than the width 323 so as to define a flexibility and / or stiffness of the stylet 130 at the distal end 230B that is greater than a flexibility and / or stiffness of the stylet 130 adjacent the junction 305. In some embodiments, the width 333 may increase along the distal tip portion 306, and the width 323 may gradually change along the transition portion 304 towards the width 333.

[0056] 4 shows a catheter assembly 400 including a catheter 72 having a stylet 130 disposed within the lumen of the catheter 72. In some embodiments, the stylet 130 may be disposed with the catheter 72 during manufacture. In other embodiments, a physician may insert the stylet 130 into the catheter 72 prior to inserting the catheter into the patient's vasculature. In the illustrated embodiment, the stylet 130 is disposed within the catheter 72 such that the distal end 230B of the stylet 130 is substantially coterminous with the distal tip 76A of the catheter 72, thereby disposing the distal tips of both the stylet and the catheter in substantial alignment with one another. In other embodiments, the distal end 230B of the stylet 130 may not be substantially coterminous with the distal tip 76A of the catheter 72.

[0057] In the illustrated embodiment, the catheter assembly 400 includes a preformed curve 410. The preformed curve 410 may be defined by a preformed curve of the stylet 130, a preformed curve of the catheter 72, or both. In some embodiments of use, the physician may rotate the stylet 130 relative to the catheter 72 by applying a torque to the handle 236. By doing so, the curve 410 may be oriented in a different direction relative to the hub 74A of the catheter 72. In other embodiments of use, the physician may rotate the catheter assembly 400 within the vasculature of the patient 70 by simultaneously applying a torque to the handle 236 and the catheter 72. By doing so, the curve 410 may be reoriented relative to the patient 70. In some embodiments, the catheter assembly 400 may include more than one preformed curve 410. In other embodiments, the preformed curve 410 may be omitted.

[0058] In the illustrated embodiment, the stylet 130 is inserted sufficiently into the catheter 72 to position the junction 305 within the catheter 72. In this embodiment, the entire coil 320 and sheath 330 are disposed within the catheter 72. In other embodiments, the junction 305 may be located outside the catheter 72, i.e., proximal to the catheter hub 74A, such that only a portion of the coil 320 and sheath 330 are disposed within the catheter 72.

[0059] Any method disclosed herein includes one or more steps or actions for carrying out the described method. The steps and / or actions of the method may be interchanged with one another. In other words, unless a specific order of steps or actions is required to properly practice an embodiment, the order and / or use of specific steps and / or actions may be modified.

[0060] In use, the stylet 130 may be loaded into the lumen of the catheter 72 to define a catheter assembly prior to catheter placement. It is noted that the stylet 130 may be preloaded into the catheter lumen at the manufacturer's stage or may be loaded into the catheter by the physician prior to catheter insertion. The stylet 130 is positioned within the catheter lumen such that the distal end 230B of the stylet 130 is substantially co-terminal with the distal tip 76A of the catheter 72, thereby positioning the distal tips of both the stylet and the catheter in substantial alignment with one another. The co-terminal location of the catheter 72 and stylet 130 allows the magnetic assembly 211 to function with the TLS sensor 50 in TLS mode to track the position of the catheter distal tip 76A as it advances through the patient's vasculature. It is noted, however, that the tip confirmation function of the system 10 does not require that the distal end 230B of the stylet 130 be co-terminal with the catheter distal tip 76A. Specifically, it is only necessary that a conductive pathway be established between the vasculature and the ECG sensor assembly 210 so that electrical impulses at the SA node or other nodes of the patient's heart can be detected. This conductive pathway in one embodiment may include various components including saline, blood, etc.

[0061] In one embodiment, once the catheter 72 is introduced into the patient's vasculature through the insertion site 73 (FIG. 1), the TLS mode of the system 10 can be used to advance the catheter distal tip 76A towards its intended destination proximate the SA node. Upon approaching the region of the heart, an ECG signal can be transmitted to the system 10 via the ECG sensor assembly 210. As the catheter 72 and stylet 130 are advanced towards the patient's heart, the conductive ECG sensor assembly 210, including the distal tip member 250, begins to detect electrical impulses generated by the SA node. In this manner, the ECG sensor assembly 210 functions as an electrode for detecting the ECG signal.

[0062] The ECG sensor assembly 210 communicates the ECG signal to the TLS sensor 50. The ECG sensor assembly 210 is operatively connected to the TLS sensor 50 via a tether connector 232. As described above, the ECG signal is then processed and displayed on the system display 30 (FIG. 1). By monitoring the ECG signal received by the TLS sensor 50 and displayed by the display 30, the physician can observe and analyze changes in the signal as the catheter distal tip 76A advances toward the SA node.

[0063] The ECG sensor assembly 210 and the magnetic assembly 211 may work in concert in assisting the physician in positioning the catheter 72 within the vasculature. In general, the magnetic assembly 211 of the stylet 130 assists the physician in generally navigating the vasculature from the initial catheter insertion to position the distal end 76A of the catheter 72 in the general region of the patient's heart. The ECG sensor assembly 210 may then be used to guide the catheter distal end 76A to a desired location within the SVC by allowing the physician to observe changes in the ECG signal generated by the heart as the ECG sensor assembly 210 approaches the SA node. Again, once the appropriate ECG signal profile is observed, the physician may determine that the distal ends of both the stylet 130 and the catheter 72 have reached the desired location in the patient's heart. Once positioned at the desired location, the catheter 72 may be secured in place and the stylet 130 may be removed from the catheter lumen.

[0064] Although some specific embodiments are disclosed herein and the specific embodiments are disclosed in some detail, the specific embodiments are not intended to limit the scope of the concepts provided herein. Additional adaptations and / or modifications may be understood by those skilled in the art. In the broader aspects, these adaptations and / or modifications are also encompassed. Thus, one may deviate from the specific embodiments disclosed herein without departing from the scope of the concepts provided herein.

Claims

1. 1. A stylet for placing a catheter within a patient's vasculature, comprising: an ECG sensor assembly including an electrode extending from a proximal end to a distal end of the stylet, the proximal end configured to couple to an ECG sensor; a magnetic assembly disposed along a distal tip portion of the stylet, the magnetic assembly generating a magnetic field; a core wire extending proximally from the magnetic assembly; a coil defining a lumen, the coil extending along a distal portion of the stylet; A stylet, the distal portion of the core wire being disposed within the lumen.

2. The stylet of claim 1 , wherein the stylet is configured to be inserted into a lumen of the catheter.

3. The stylet of claim 1 or 2, wherein the stylet is configured to position the catheter within the patient's superior vena cava.

4. The stylet of claim 1 , wherein the electrode comprises the core wire.

5. The stylet of claim 1 , wherein the electrode comprises the coil.

6. The stylet of claim 1 , wherein the magnetic assembly comprises a plurality of magnetic elements disposed within the lumen.

7. The stylet of claim 6 , wherein each of the magnetic elements has a cylindrical shape, and the magnetic elements are disposed end-to-end within the lumen.

8. The stylet of claim 6 or 7, wherein one or more magnetic elements are attached to the coil.

9. The stylet of claim 1 , wherein the coil is attached to the core wire.

10. The stylet of claim 1 , wherein the coil is electrically coupled to the core wire.

11. The stylet of claim 1 , wherein the coil comprises a coil member forming a first helix.

12. The stylet of claim 11 , wherein the coil member has a rectangular cross-sectional shape having a width and a thickness.

13. The stylet described in claim 12, wherein the width is 0.01 mm to 1 mm.

14. A stylet as described in claim 12 or 13, wherein the thickness is 0.01 mm to 1 mm.

15. A stylet described in any one of claims 11 to 14, wherein the pitch of the first spiral is 0.01 mm to 10 mm.

16. 16. The stylet of any one of claims 11 to 15, wherein the coil member is a first coil member and the coil comprises at least a second coil member forming at least a second helix.

17. The stylet of claim 16 , wherein the first coil member and the second coil member cross each other.

18. The stylet of any one of claims 1 to 17, wherein the coil comprises at least three coil members defining a braided or woven structure.

19. The stylet of any one of claims 1 to 18, further comprising a sheath extending along the distal portion, the sheath covering the coil.

20. 20. The stylet of claim 1, wherein the core wire includes a first thickness extending along a proximal portion of the core wire and a second thickness extending along a distal portion of the core wire, the second thickness being less than the first thickness.

21. The stylet of claim 20 , wherein the core wire includes a taper extending between the first thickness and the second thickness.

22. The stylet of claim 20 or 21, wherein the distal portion of the core wire is circular.

23. 23. The stylet of any one of claims 20 to 22, wherein the distal portion of the core wire extends along the magnetic assembly.

24. 24. The stylet of any one of claims 1 to 23, further comprising a distal tip member coupled to the coil.

25. The stylet of claim 24, wherein the distal tip member is formed from an electrically conductive material.

26. The stylet of claim 25, wherein the distal tip member is electrically coupled to the coil.

27. 27. The stylet of any one of claims 1 to 26, wherein the core wire extends distally beyond the magnetic assembly.

28. The core wire extends distally beyond the magnetic assembly; 27. The stylet of any one of claims 24 to 26, wherein the distal tip member is electrically coupled to the core wire.

29. 29. The stylet of any one of claims 1-28, further comprising a handle attached to the core wire at a proximal end thereof.

30. 30. The stylet of any one of claims 1-29, further comprising a tether coupled to the core wire at the proximal end thereof, the tether comprising an electrical conductor that forms part of the electrode.

31. An intravascular catheter assembly comprising: A catheter having a lumen; An intravascular catheter assembly comprising: a stylet according to claim 1 disposed within the lumen of the catheter.

32. 32. The catheter assembly of claim 31, wherein the catheter is configured to position a tip of the catheter within the superior vena cava of a patient.

33. 33. The catheter assembly of claim 31 or 32, wherein the distal end of the catheter and the distal end of the stylet are substantially coterminous.

34. 34. The catheter assembly of claim 31, further comprising a preformed curve along a distal portion of the catheter assembly.

35. The catheter assembly of claim 34 , wherein the preformed curve is defined by a preform curve of the stylet.

36. 36. The catheter assembly of claim 31, wherein the coil of the stylet is disposed entirely within the lumen.

37. 37. The catheter assembly of claim 31, wherein the stylet sheath is disposed entirely within the lumen.

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