ECG stylet with improved fatigue resistance and fracture 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

[0005] ,

[0004] , ,

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

Background Art

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

[0003] The specific positioning of an intravascular device is very important and can have a significant impact on a patient's health. For example, a CVC (central venous catheter) with its tip positioned ideally provides reliable vascular access with optimal treatment delivery while minimizing short-term and long-term complications.

[0004] Although CVCs have been used for many years, it has always been problematic to determine the position of the tip of a CVC. In addition to the need to know where the tip is during initial placement, a CVC can move or may need to be repositioned after initial placement. Therefore, the operator must monitor or periodically reconfirm the position of the tip.

[0005] ECG (electrocardiogram)-based leads 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 indicate specific locations and / or specific cardiac functions or states within the thoracic cavity. By using specific parameters of cardiac electrical activity, when measured intravascularly or intravascularly, i.e., from within the blood vessels or within the heart, specific locations and / or normal or abnormal functional states in the cardiovascular system can be identified.

[0006] Some catheter guidance systems may also include a TLS (Tip Position / Navigation System) modality for magnetic-based tracking of the catheter tip. Such systems may include a magnetic element coupled to a stylet within the catheter, which is positioned within the patient's vascular structure. In some examples, the magnetic element may be detached from the stylet, exposing the patient to particulate embolisms.

[0007] Disclosed herein are novel devices and methods for improving the reliability of stylets for use with magnetic-based tracking systems, thereby reducing the possibility of magnetic elements becoming detached from the stylet, and improving patient safety from exposure to particulate embolisms. [Overview of the project]

[0008] This specification discloses a stylet for positioning a catheter within a patient's vascular structure. The stylet includes an ECG sensor assembly having electrodes extending from the proximal end to the distal end of the stylet, the proximal end configured to couple with an ECG sensor. The stylet further includes a magnetic assembly positioned along the distal portion of the stylet, the magnetic assembly generating a magnetic field. The stylet further includes a core wire extending proximal to the magnetic assembly and a coil defining a lumen. The coil extends along the distal portion of the stylet, and the distal portion of the core wire is positioned 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] A magnetic assembly may include multiple magnetic elements arranged within the lumen of a coil. Each magnetic element has a cylindrical shape, and the magnetic elements may be arranged end-to-end within the lumen. One or more magnetic elements may be attached to the coil.

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

[0012] The coil may include at least a second coil member forming a second helix, and the first and second coil members may intersect each other. 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 the distal portion of the stylet, and the sheath may cover the coil.

[0013] The core wire may have a first thickness extending along its proximal portion and a second thickness extending along its distal portion, 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 a coil, the distal tip member may be formed from a conductive material. The distal tip member may also be electrically coupled to the coil. The distal portion of the core wire may extend distally beyond the magnet assembly, and the core wire may be electrically coupled to another core wire.

[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 a 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 spiral pitch may be 0.01 mm to 10 mm. This specification also discloses intravascular catheter assemblies. The catheter assembly includes a catheter having a lumen and a stylet positioned within the lumen of the catheter. The stylet includes an ECG sensor assembly having electrodes extending from the proximal end to the distal end of the stylet, the proximal end configured to be coupled to an ECG sensor. The stylet further includes a magnetic assembly positioned along the distal portion of the stylet, the magnetic assembly generating a magnetic field. The stylet further includes a core wire extending proximal to the magnetic assembly and a coil defining the lumen. The coil extends along the distal portion of the stylet, and the distal portion of the core wire is positioned within the lumen of the coil.

[0017] The catheter assembly may be configured to position the tip of the catheter within the patient's superior vena cava, and the distal end of the catheter may be substantially the same as the distal end of the stylet.

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

[0019] The entire coil of the stylet may be placed within the lumen, or the entire sheath of the stylet may be placed within the lumen. This specification also discloses a method for positioning a catheter in a patient's superior vena cava. The method includes inserting a stylet into the lumen of the catheter. The stylet includes an ECG sensor assembly, which includes electrodes extending from the proximal to the distal end of the stylet, and the electrodes are configured to transmit ECG signals to an ECG system. The stylet further includes a magnetic assembly that generates a magnetic field and a long coil extending from the distal to the proximal end of the stylet. The coil defines a lumen that houses the magnetic assembly.

[0020] The method further includes the steps of connecting an ECG sensor assembly to an ECG system, advancing a catheter along the patient's vascular structure, halting catheter advancement when the ECG signal indicates that the tip of the stylet has been positioned within the superior vena cava, and removing the stylet from the catheter lumen.

[0021] In some embodiments of this method, the stylet includes a handle, and the method further includes the step of rotating the stylet within the catheter by manually applying torque to the handle. The method may further include the step of rotating the catheter within the vascular structure by manually applying torque to the handle and the catheter.

[0022] This method may further include the steps of aligning the distal tip of the stylet with the distal tip of the catheter and transmitting an ECG signal along the conductive coil member of the coil. These and other features of the concepts provided herein will become apparent to those skilled in the art by considering the accompanying drawings illustrating in more detail specific embodiments of such concepts and the following description.

[0023] The present disclosure will be described in more detail by reference to the specific embodiments shown in the accompanying drawings. It should be understood that these drawings show only typical embodiments of the invention and thus should not be regarded as limiting its scope. Exemplary embodiments of the invention will be described and explained more specifically and in detail using the accompanying drawings.

Brief Description of the Drawings

[0024] [Figure 1] Schematic diagram of a catheter inserted into a patient with the assistance of a patient and an integrated system according to some embodiments. [Figure 2] Perspective view of a stylet used in connection with the integrated system of FIG. 1 according to some embodiments. [Figure 3A] Side view of the catheter engagement section of the stylet of FIG. 2 according to some embodiments. [Figure 3B] Detailed side view of a portion of the catheter engagement section at the junction point according to some embodiments. [Figure 3C] Side cross-sectional view of the transition portion of the catheter engagement section according to some embodiments. [Figure 3D] Side cross-sectional view of the distal tip portion of the catheter engagement section according to some embodiments. [Figure 4] Catheter assembly including the catheter and stylet of FIG. 1 according to some embodiments.

Modes for Carrying Out the Invention

[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 the specific embodiments disclosed herein can be easily separated from that specific embodiment and may have features that can be optionally combined or substituted with the features of any of the plurality of other embodiments disclosed herein.

[0026] Regarding the terminology used herein, it should be understood that each term is intended to describe a particular embodiment and does not limit the scope of the concepts presented herein. Ordinal numbers (e.g., 1st, 2nd, 3rd, etc.) are generally used to distinguish or identify features or processes that are different from each other within a group of features or processes, and do not impose any orderly or numerical limitations. For example, the "1st," "2nd," and "3rd" features or processes do not necessarily have to appear in this order, and a particular embodiment containing such features or processes does not necessarily have to be limited to three features or processes. Notations such as "left," "right," "up," "down," "front," and "back" are used for convenience and do not, for example, imply any particular fixed position, orientation, or direction. Rather, such notations are used to indicate, for example, relative position, orientation, or direction. Unless it is clearly indicated in the context that otherwise, singular forms represented by "a," "an," and "the" include plural forms.

[0027] The directional terms “proximal” and “distal” are used herein to refer to opposing positions in a medical device. The proximal end of the device is defined as the end of the device that is closest to the end user and furthest from the patient when the device is used by the end user. The distal end is the end of the device opposite the proximal end along its longitudinal direction, or the end that is furthest 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 those generally understood by those skilled in the art. Figure 1 shows various features of the catheter placement system (system) 10. System 10 generally relates to a catheter placement system configured to accurately place a catheter within the vascular structure of a patient 70. The catheter placement system 10 uses the following three modalities to improve catheter placement accuracy: 1) ultrasound-assisted guidance for introducing the catheter into the patient's vascular structure, 2) TLS (tip position / navigation system) for magnetic-based tracking of the catheter tip, and 3) ECG signal-based catheter tip guidance. The combination of these three modalities enables the catheter placement system 10 to place the catheter within the patient's vascular structure with a relatively high level of accuracy, i.e., to place the distal tip of the catheter at a predetermined desired position. Furthermore, ECG-based guidance of the catheter tip allows accurate tip placement to be confirmed without the need for X-rays for confirmation. This thus reduces the patient's exposure to potentially harmful X-rays, the costs and time associated with transporting the patient 70 to and from the X-ray department, and the costly and inconvenient catheter repositioning procedure.

[0029] The combined features of system 10 are integrated into a single device for use by a physician placing the catheter 72. Integrating the three modalities into a single device simplifies the catheter placement process and enables relatively fast catheter placement. The integrated catheter placement system 10 allows observation of ultrasound, TLS, and ECG activity from a single display of the integrated system. Several systems and methods of TLS and ECG-based guidance are described in U.S. Patent No. 9,220,432, entitled “Method and system of utilizing ECG signal for central venous catheter tip positioning,” and U.S. Patent No. 9,999,371, entitled “Integrated system for intravascular placement of a catheter,” each of which is incorporated in whole by reference in this application. Further disclosures of stylets and catheters for use with TLS systems and ECG-based guidance can be found in the following U.S. patents. U.S. Patent 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 these is incorporated in whole by reference in this application).

[0030] Figure 1 further illustrates the various components of the system 10, including the console 20, display 30, probe 40, and sensor 50. Figure 1 shows the general relationship of the components to the patient 70 in the procedure of placing the catheter 72 into the patient's vascular structure 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 is present within the patient's vascular structure after placement is complete. The system 10 is used to finally position the distal tip 76A of the catheter 72 at a desired location within the patient's vascular structure. In some embodiments, the desired location of the distal tip 76A of the catheter is close to the patient's heart, such as the lower one-third (1 / 3) portion of the SVC (superior vena cava). Naturally, the system 10 may be used to position the distal tip 76A of the catheter at other locations. The proximal portion 74 of the catheter further includes a hub 74A. The hub 74A forms a fluid communication between one or more lumens of the catheter 72 and one or more extension legs 74B that extend proximal to the hub 74A.

[0031] The stylet 130 is removably loaded into the catheter 72 and used during insertion to position the distal end 76A of the catheter at a desired location within the patient's vascular structure. In one embodiment, the stylet 130 may be pre-loaded into the lumen of the catheter 72 such that its distal end 130B is substantially coplanar with or at the same terminal as the catheter opening at its distal end 76A. Note that although 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] Figure 2 shows the stylet 130 removed from catheter 72. Various details of the stylet 130 are described below with reference to Figure 2. As shown, the stylet 130 includes an ECG sensor assembly 210 and a magnetic assembly 211, defining a proximal end 230A and a distal end 230B. A connector 232 is included in the proximal end 230A, and a tether 134 extends distally from the connector 232 and is attached to the handle 236. A core wire 238 extends distally from the handle 236. Each assembly and component of the stylet 130 is described in detail below.

[0033] The handle 236 is positioned to allow insertion / removal of the stylet 130 from the catheter 72. In embodiments in which the core wire 238 is rotatable, the handle 236 further assists in navigating the distal portion of the catheter through the vascular structure of the patient 70 by allowing the core wire 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. Thus, the tether 134 forms a conductive path from the distal portion of the core wire 238 to the tether connector 232 on the proximal end 230A of the stylet 130. The connector 232 may be configured for an operable connection to a TLS sensor 50 on the patient's chest to assist in navigating the distal tip 76A of the catheter to a desired position within the patient's vascular structure. The catheter engagement section 233 of the stylet 130 extends between the distal end 230B and the handle 236.

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

[0036] As described above, the stylet 130 includes a core wire 238 defining an elongated 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 will be 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-titanium 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 engagement section 233 to bias the distal portion of the catheter 72 to a similar corresponding pre-formed configuration. In other embodiments, the core wire 238 does not include pre-formation.

[0037] Figure 3B is a detail view of the catheter engagement section 233 at the junction 305. As shown in Figure 3B, the core wire 238 extends proximal to the junction 305, having a first cross-sectional diameter 311. The coil 320 and sheath 330 extend distally from the junction 305. As shown in Figure 3C, the distal portion of the core wire 238 extends distally from the junction 305 and is located within the lumen 327 of the coil 320. In some embodiments, the sheath 330 extends proximal to the junction 305, covering at least a portion of the core wire 238.

[0038] The coil 320 extends along the distal portion 302 from the joint 305 to the distal end 230B. The coil 320 defines the flexibility and rigidity of the distal portion 302 so that the stylet 130 follows the curved path of the vascular structure without damaging the inner wall of the vascular structure. The coil 320 may also define the robustness and / or fatigue resistance of the distal portion 302. In other words, the coil 320 may define the reliability of the stylet 130 against breakage in use. More specifically, the coil 320 may prevent breakage of the distal portion 302 if it is bent once or more times during use.

[0039] Referring to Figures 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 properties of the coil members 322 (i.e., cross-sectional shape and material) can at least partially define the flexibility and / or rigidity of the distal portion 302. For example, a coil member 322 with a thicker cross-section may define the flexibility and / or rigidity of the distal portion 302 more than a coil member 302 with a thinner (i.e., less thick) cross-section. The cross-sectional shape of the coil member 322 may be circular or non-circular. In the illustrated embodiment, the coil member has a rectangular cross-sectional shape with a width 323 and a thickness 324. In the illustrated embodiment, the width 323 of the coil member 322 may be about 0.01 mm to 0.5 mm. In other embodiments, the 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, the thickness 324 of the coil member 322 may be about 0.005 mm to 0.3 mm. In other embodiments, the 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, the coil member 322 may include 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, the coil member 322 may be formed from a plurality of wire filaments forming a cable, such as a braided cable.

[0040] The coil 320 also defines the pitch 325, i.e., the spacing between adjacent windings of the coil 320. In some embodiments, the coil 320 may be configured such that the windings of the coil 320 are directly adjacent to each other, i.e., adjacent windings are in contact with each other. In other embodiments, the coil 320 may be configured to define space or separation between adjacent windings. In some embodiments, the pitch 325 of the coil 320 may be about 0.01 mm to 1 mm, 0.01 mm to 0.5 mm, or 0.1 mm to 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 each other. 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 those skilled in the art, the width 323 combined with the pitch 325 may at least partially, and in some embodiments substantially, define the flexibility and / or rigidity of the stylet 130 along the distal portion 302. As the distal portion 302 advances along the vascular structure, the distal portion 302 may have a curved shape with different bending radii. For example, the bending radius along the distal tip portion 306 may be smaller than the bending radius along the transition portion 304. Therefore, it may be advantageous for the coil 320 to have a shorter width 323 and a corresponding shorter pitch 325 along the distal tip portion 306 than the transition portion 304, thereby defining greater flexibility and / or rigidity along the distal tip portion 306. By varying the width 323 and / or pitch 325 along the distal portion 302, stiffness, flexibility, and rigidity can be optimized along the distal portion 302. Similarly, by changing the width 323 of the coil member 322, stiffness, flexibility, and rigidity can be defined. Further explanations regarding pitch and width variations are given below with reference to Figure 3D.

[0042] In the illustrated embodiment, the coil 320 includes a single coil member 322 that forms 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, a single coil member 322 defines a single coil layer. In other embodiments, two or more coil members 322 may define a single coil layer by being wound together with each other. In other embodiments, two or more coil members 322 may define more than one layer by being wound together with each other or in opposite directions. 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 coil members 322 may be formed from a polymer material. In the illustrated embodiment, the coil 320 may be configured to conduct electricity from the proximal end to the distal end.

[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 the proximal end of the coil 320. In some embodiments, the coupling may include a radial tightening force on the coil 320 against the core wire 238, defined by the interfering dimensions. In other words, the inner diameter of the coil 320 may be less than the first diameter 311 of the core wire 238, such that in the free state, when the coil 320 is assembled, i.e., when the core wire 238 is placed within the lumen 327 of the coil 320, it exerts a radially inward tightening force on the core wire 238. In other embodiments, the coil 320 may be attached to the core wire 238 by adhesive. As can be understood by those skilled in the art, the coil 320 may be attached to the core wire 238 at one or more other locations along the overlapping length of the core wire 238 and the coil 320 by any other suitable mounting method.

[0045] Figure 3C shows a side view of the transitional portion 304 of the distal portion 302, with the coil 320 and sheath 330 shown in cross-section. As described above, the distal portion of the core wire 238 is located 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 transitional portion 304 and the bending stiffness of the coil 320. As can be understood by those skilled in the art, the stiffness of the core wire 238 decreases with decreasing diameter. In other words, the stiffness of the catheter engagement section 233 may gradually decrease along the transitional portion 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 positioned along the outside of the coil 320 from the junction 305 to the distal end 230B. The sheath 330 may allow the distal portion 302 to be inserted into the catheter 72 by forming a smooth outer surface and / or a low-friction outer surface of the distal portion 302. 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 so that the sheath 330 is formed when the sheath material hardens / solidifies. 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 inside the shrinkable tube and then shrinking the shrinkable tube over the coil 320. In yet another embodiment, 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 polymer material. In some embodiments, the sheath 330 may contribute to the rigidity of the distal portion 302. For example, the sheath 330 may enable the definition of the preform shape of the distal portion 302.

[0047] The diagram in Figure 3B shows the outer diameter of the sheath 330 being larger than the proximal first diameter 311, but in some embodiments, the catheter engagement section 233 may have a substantially constant cross-sectional size (e.g., diameter) beyond the junction 305. The outer diameter of the sheath 330 may be substantially equal to the first diameter 311 of the core wire 238. In such cases, the first diameter 311, taper 313, coil member thickness 324, and sheath thickness 334 may be sized and / or arranged longitudinally to define a substantially constant outer diameter beyond the junction 305.

[0048] Figure 3D is a detailed cross-sectional view of the distal tip portion 306. As described above, the stylet 130 includes a magnetic assembly 211 positioned adjacent to the distal end 230B and along the distal tip portion 306. The magnetic assembly 211 may be configured for use during the TLS mode of the system 10. The magnetic assembly 211 includes a plurality of magnetic elements 344 positioned within the lumen 327 of the coil 320. The plurality of magnetic elements 344 may form a linear array of magnetic elements 344 extending proximal from the distal end 230B. In the illustrated embodiment, the magnetic elements 344 include 20 solid cylindrical ferromagnetic magnets stacked end-to-end so that the end faces 346 of the magnetic elements 144 are positioned adjacent to each other. 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 position 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 the longitudinal displacement of the magnetic elements 344 relative to the lumen 327 can 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 a reduction in stress and / or strain on the coil 320 and / or sheath 330 when the distal tip portion 306 is arranged in a curved shape. The reduction in 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 so that the position of the distal end 230B of the stylet can be observed by a TLS sensor 50 (see Figure 1) placed 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 advances through the patient's vascular structure together with the catheter 72. In this way, the physician placing the catheter 72 can generally determine the position of the distal end 76A of the catheter within the patient's vascular structure and can also detect when catheter positional abnormalities occur, such as catheter advancement along an undesirable vein.

[0051] As shown in Figure 3D, the stylet 130 may include a distal tip member 350 positioned 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 welded 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 so as to improve the stylet 130's ability to detect ECG signals.

[0052] The connector 232, conductor 234, core wire 238, coil 320, and distal tip member 350 all communicate electrically with each other to define an ECG sensor assembly 210 that includes a conductive path for transmitting an ECG signal from the distal end 230B to the proximal end 230A of the stylet 130. Thus, the ECG sensor assembly 210 defines electrodes that enable the transmission of an ECG signal from the patient's body fluids (e.g., blood in the superior vena cava) to the ECG sensor 50. The ECG sensor assembly 210 enables the stylet 130, positioned within the lumen of the catheter 72 during insertion, to be used to detect intraatrial ECG signals generated by the patient's cardiac SA or other nodules. This allows the distal tip 76A of the catheter 72 to be navigated to a predetermined position within the vascular structure adjacent to the patient's heart. Thus, the ECG sensor assembly 210 serves as an aid in confirming the proper placement of the distal tip 76A of the catheter.

[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 positioned between the magnetic element 344 and the inner surface of the lumen of the coil 320. The core wire 238 is directly electrically coupled to the distal tip member 350, and therefore does not need to be electrically coupled to the coil 320.

[0054] As described above in relation to Figure 3B, the pitch of the coil 320 and / or the width of the coil member 322 may vary along the distal portion 302. Therefore, in some embodiments, the pitch may vary along the distal portion 302 between a pitch 325 adjacent to the joint 305 as shown in Figure 3B and a pitch 335 adjacent to the distal end 230B as shown in Figure 3D. In some embodiments, the pitch 335 may be smaller than the pitch 325 so as to define the flexibility and / or rigidity of the stylet 130 at the distal end 230B which is greater than the flexibility and / or rigidity of the stylet 130 adjacent to the joint 305. In some embodiments, the pitch 335 may increase along the distal tip portion 306, and the pitch 325 may gradually change toward the pitch 335 along the transition portion 304.

[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 to the joint 305 as shown in Figure 3B and a width 333 adjacent to the distal end 230B as shown in Figure 3D. In some embodiments, the width 333 may be smaller than the width 323 to define the flexibility and / or rigidity of the stylet 130 at the distal end 230B, which is greater than the flexibility and / or rigidity of the stylet 130 adjacent to the joint 305. In some embodiments, the width 333 may increase along the distal tip portion 306, and the width 323 may gradually change toward the width 333 along the transition portion 304.

[0056] Figure 4 shows a catheter assembly 400 including a catheter 72 having a stylet 130 positioned within the lumen of the catheter 72. In some embodiments, the stylet 130 may be positioned with the catheter 72 during manufacturing. In other embodiments, the physician may insert the stylet 130 into the catheter 72 before inserting the catheter into the patient's vascular structure. In the illustrated embodiment, the stylet 130 is positioned within the catheter 72 such that the distal end 230B of the stylet 130 is substantially terminally with the distal tip 76A of the catheter 72, thereby positioning the distal tips of both the stylet and the catheter substantially aligned with each other. In other embodiments, the distal end 230B of the stylet 130 does not have to be substantially terminally 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 the preformed curve of the stylet 130, the 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 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 vascular structure of the patient 70 by simultaneously applying 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 fully into the catheter 72 to position the connection point 305 within the catheter 72. In this embodiment, the entire coil 320 and sheath 330 are positioned within the catheter 72. In other embodiments, the connection point 305 may be positioned outside the catheter 72, i.e., proximal to the catheter hub 74A, so that only a portion of the coil 320 and sheath 330 are positioned 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 interchangeable. In other words, the order and / or use of any particular steps and / or actions may be changed unless a particular order of steps or actions is required for the embodiment to be properly carried out.

[0060] When in use, the stylet 130 may be loaded into the lumen of the catheter 72 to define the catheter assembly before catheter placement. Note that the stylet 130 may be pre-loaded into the catheter lumen at the manufacturer stage, or loaded into the catheter by a physician before catheter insertion. The stylet 130 is positioned in the catheter lumen such that its distal end 230B is substantially terminally adjacent to the distal tip 76A of the catheter 72, thereby substantially aligning the distal tips of both the stylet and the catheter. The fact that the catheter 72 and stylet 130 are terminally adjacent allows the magnetic assembly 211 to function with the TLS sensor 50 in TLS mode to track the position of the distal tip 76A of the catheter as it advances through the patient's vascular structure. However, note that for the tip confirmation function of the system 10, the distal end 230B of the stylet 130 does not need to be terminally adjacent to the distal tip 76A of the catheter. Specifically, it is only necessary to establish a conductive path between the vascular structure and the ECG sensor assembly 210 so that electrical impulses from the patient's cardiac SA node or other nodes can be detected. In one embodiment, this conductive path may include various components, such as saline solution or blood.

[0061] In one embodiment, once the catheter 72 is introduced into the patient's vascular structure through the insertion site 73 (Figure 1), the TLS mode of the system 10 can be used to advance the distal tip 76A of the catheter toward an intended destination approaching the SA node. As it approaches the region of the heart, an ECG signal may be transmitted to the system 10 via the ECG sensor assembly 210. As the catheter 72 and stylet 130 are advanced toward 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. Thus, the ECG sensor assembly 210 functions as an electrode for detecting the ECG signal.

[0062] The ECG sensor assembly 210 transmits the ECG signal to the TLS sensor 50. The ECG sensor assembly 210 is operably 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 (Figure 1). By monitoring the ECG signal received by the TLS sensor 50 and displayed on the display 30, the physician can observe and analyze changes in the signal as the distal tip 76A of the catheter advances toward the SA node.

[0063] The ECG sensor assembly 210 and the magnetic assembly 211 can work together to assist the physician in positioning the catheter 72 within the vascular structure. Generally, the magnetic assembly 211 of the stylet 130 assists the physician in generally navigating through the vascular structure from the initial catheter insertion so that the distal end 76A of the catheter 72 is positioned in a general area of ​​the patient's heart. The ECG sensor assembly 210 may then be used to guide the distal end 76A of the catheter to the desired position 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 nodule. Again, once a suitable ECG signal profile is observed, the physician can determine that both the distal ends of the stylet 130 and the catheter 72 have reached the desired position in the patient's heart. Once positioned, the catheter 72 may be secured in place and the stylet 130 may be removed from the catheter lumen.

[0064] While several specific embodiments are disclosed herein, and some embodiments are disclosed in some degree of detail, these 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 broader embodiments, these adaptations and / or modifications are also encompassed. Thus, one may deviate from specific embodiments disclosed herein without departing from the scope of the concepts provided herein.

Claims

1. A stylet for positioning a catheter within a patient's vascular structure, An ECG sensor assembly comprising an electrode extending from the proximal end to the distal end of the stylet, wherein the proximal end is configured to be coupled to an ECG sensor, A magnetic assembly positioned along the distal tip portion of the stylet, comprising a magnetic assembly that generates a magnetic field, A core wire extending proximal to the magnetic assembly, A coil for defining lumens, comprising a coil extending along the distal portion of the stylet, The distal portion of the core wire is positioned within the lumen. The magnetic assembly comprises a plurality of magnetic elements arranged within the lumen, A stylet in which one or more magnetic elements are attached to the coil.

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

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

4. The stylet according to any one of claims 1 to 3, wherein the electrode includes the core wire.

5. The stylet according to any one of claims 1 to 4, wherein the electrode includes the coil.

6. The stylet according to any one of claims 1 to 5, wherein each of the magnetic elements has a cylindrical shape, and the magnetic elements are arranged end to end in the lumen.

7. The stylet according to any one of claims 1 to 6, wherein the coil is attached to the core wire.

8. The stylet according to any one of claims 1 to 7, wherein the coil is electrically coupled to the core wire.

9. The stylet according to any one of claims 1 to 8, wherein the coil comprises a coil member that forms a first helix.

10. The stylet according to claim 9, wherein the coil member has a rectangular cross-sectional shape having width and thickness.

11. The stylet according to claim 10, wherein the width is 0.01 mm to 1 mm.

12. The stylet according to claim 10 or 11, wherein the thickness is 0.01 mm to 1 mm.

13. The stylet according to any one of claims 9 to 12, wherein the pitch of the first helix is ​​0.01 mm to 10 mm.

14. The stylet according to any one of claims 9 to 13, wherein the coil member is a first coil member, and the coil comprises at least a second coil member that forms at least a second helix.

15. The stylet according to claim 14, wherein the first coil member and the second coil member intersect each other.

16. The stylet according to any one of claims 1 to 15, wherein the coil comprises at least three coil members defining a braided structure or a woven structure.

17. The stylet according to any one of claims 1 to 16, further comprising a sheath extending along the distal portion, wherein the sheath covers the coil.

18. The stylet according to any one of claims 1 to 17, wherein the core wire includes a first thickness extending along the proximal portion of the core wire and a second thickness extending along the distal portion of the core wire, the second thickness being less than the first thickness.

19. The stylet according to claim 18, wherein the core wire includes a taper extending between the first thickness and the second thickness.

20. The stylet according to claim 18 or 19, wherein the distal portion of the core wire is circular.

21. The stylet according to any one of claims 18 to 20, wherein the distal portion of the core wire extends along the magnetic assembly.

22. The stylet according to any one of claims 1 to 21, further comprising a distal tip member coupled to the coil.

23. The stylet according to claim 22, wherein the distal tip member is formed from a conductive material.

24. The stylet according to claim 23, wherein the distal tip member is electrically coupled to the coil.

25. The stylet according to any one of claims 1 to 24, wherein the core wire extends distally beyond the magnetic assembly.

26. The core wire extends distally beyond the magnetic assembly, The stylet according to any one of claims 22 to 24, wherein the distal tip member is electrically coupled to the core wire.

27. The stylet according to any one of claims 1 to 26, further comprising a handle attached to the core wire at the proximal end of the core wire.

28. The stylet according to any one of claims 1 to 27, further comprising a tether coupled to the core wire at the proximal end of the core wire, wherein the tether comprises a conductor forming part of the electrode.

29. Intravascular catheter assembly A catheter equipped with a lumen, An intravascular catheter assembly comprising a stylet according to claim 1, disposed within the lumen of the catheter.

30. The catheter assembly according to claim 29, wherein the catheter is configured to position the tip of the catheter within the superior vena cava of a patient.

31. The catheter assembly according to claim 29 or 30, wherein the distal end of the catheter and the distal end of the stylet are substantially the same end.

32. The catheter assembly according to any one of claims 29 to 31, further comprising a preformed curve along the distal portion of the catheter assembly.

33. The catheter assembly according to claim 32, wherein the preformed curve is defined by the preformed curve of the stylet.

34. The catheter assembly according to any one of claims 29 to 33, wherein the entire coil of the stylet is positioned within the lumen.

35. The catheter assembly according to any one of claims 29 to 34, wherein the entire sheath of the stylet is positioned within the lumen.

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