Patent Description:
Various endovascular devices, including without limit central venous catheters ("CVC"), may be inserted into the vasculature of a patient to detect and/or treat various health issues. CVCs are endovascular devices including any catheter designed to utilize the central veins (e.g., subclavian and superior vena cava) or right sided cardiac chambers for the delivery and/or withdrawal of blood, blood products, therapeutic agents, and/or diagnostic agents. CVCs also include catheters inserted into the central veins or right sided cardiac chambers for the acquisition of hemodynamic data. Standard central venous catheters for intravenous access, dialysis catheters, percutaneously introduced central catheters ("PICC" lines), and right heart catheters are examples of CVCs. In some applications, an endovascular device, e.g., a central venous catheter (CVC), may be inserted into the superior vena cava (SVC) of a patient.

The specific location placement of an endovascular device is very important and can have a significant impact on the health of the patient. For example, a central venous catheter (CVC) with its tip located in the ideal position provides reliable vascular access with optimal therapeutic delivery, while minimizing short and long-term complications.

While CVCs have been used for many years, determining the position of the tip of the CVC has always been problematic. Further, in addition to the need to know where the tip is during initial placement, the CVC may migrate or otherwise move after the initial placement and require re-positioning. Therefore, the operator must monitor or periodically reevaluate the location of the tip.

Electrocardiogram (ECG) based guidance can be used as a positioning technique for catheter tip placement and confirmation. The electrical conduction system of the heart creates specific electrical signals, electrical energy distributions and behaviors thereof which are indicative of specific locations in the thoracic cavity and/or of specific heart functions or conditions. When measured endovascularly or intravascularly, i.e., from within blood vessels or from within the heart, certain parameters of the electrical activity of the heart can be used to identify specific locations in the cardiovascular system and/or functional conditions, normal or abnormal.

Some catheter guidance systems may also include a tip location/navigation system ("TLS") modality for magnetically-based tracking of the catheter tip. Such system may include magnetic elements coupled to a stylet within the catheter to be placed within the vasculature of the patient. In some instances, the magnetic elements may potentially become decoupled from the stylet exposing the patient to particulate emboli.

<CIT> relates to a stylet for use in guiding a distal tip of a catheter to a predetermined location within the body of a patient. In one embodiment the stylet is configured for use within a lumen of the catheter and comprises a core wire, an ECG sensor, and a magnetic assembly. In one embodiment a distal segment of the stylet includes a tubing inside which is disposed a distal portion of the core wire, terminating at the core wire distal end. A conductive wire proximally extends within the tubing from the stylet distal end to the proximal end of the stylet for connection with a suitable ECG sensor module. The magnetic assembly, including a plurality of permanent magnets or other suitable magnetic/electromagnetic elements, is disposed distally to the core wire. A conductive coil proximally extends within the tubing and about the magnetic assembly from the stylet distal end to a connection point with the core wire at the proximal end of the coil.

Disclosed herein are new devices and methods for enhancing the reliability of stylets for use with magnetically-based tracking systems thereby reducing the probability of magnetic elements becoming decoupled from the stylet and providing enhanced safety for the patient against exposure to particulate emboli.

Disclosed herein is a stylet for placing a catheter in a vasculature of a patient. The stylet includes an ECG sensor assembly having an electrode extending from a proximal end to a distal end of the stylet and the proximal end is configured to couple with an ECG sensor. The stylet further includes a magnetic assembly disposed along a distal portion of the stylet and the magnetic assembly producing a magnetic field. The stylet further includes a core wire extending proximally away from the magnetic assembly and a coil defining a lumen. The coil extends along a distal portion of the stylet, and a distal portion of the core wire is disposed within the lumen of the coil.

The stylet may be configured to be inserted within a lumen of the catheter and the stylet may also be configured for placement of the catheter within a superior vena cava of the patient. The electrode may include the core wire and the coil.

The magnetic assembly includes a plurality of magnet elements disposed within the lumen of the coil. Each magnet element may have a cylindrical shape, and the magnet elements may be arranged end to end within the lumen. One or more of the magnet elements are attached to the coil.

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

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 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.

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 and the second thickness may be less than the first thickness. The core wire may include a taper extending between the first thickness the second thickness. The distal portion of the core wire may be round, and in some embodiments, the distal portion of the core wire extends along the magnet assembly.

The stylet may include a distal tip member coupled with the coil and the distal tip member may be formed of an electrically conductive material. The distal tip member may also be electrically coupled with the coil.

The distal portion of the core wire may extend distally beyond the magnet assembly, and the core wire may be electrically coupled with the core wire.

The stylet may further include a handle attached to the core wire at a proximal end of the core wire and the stylet may also further include a tether coupled with the core wire at the proximal end of the core wire, where the tether includes an electrical conductor forming a portion of the electrode.

The stylet may have a width is between <NUM> and <NUM> and a thickness between <NUM> and <NUM>. A pitch of the helix may be between <NUM> and <NUM>.

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 an electrode extending from a proximal end to a distal end of the stylet and the proximal end is configured to couple with an ECG sensor. The stylet further includes a magnetic assembly disposed along a distal portion of the stylet and the magnetic assembly producing a magnetic field. The stylet further includes a core wire extending proximally away from the magnetic assembly and a coil defining a lumen. The coil extends along a distal portion of the stylet, and a distal portion of the core wire is disposed within the lumen of the coil.

The catheter assembly may be configured for placement of a tip of the catheter within superior vena cava of a patient and a distal end of the catheter may be substantially co-terminal with a distal end of the stylet.

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 preform curve of the stylet.

The coil of the stylet may be entirely disposed within the lumen and a sheath of the stylet may also be entirely disposed within the lumen.

Also disclosed herein is method a placing a catheter within a superior vena cava of a patient. The method includes inserting a stylet within a lumen of the catheter. The stylet includes an ECG sensor assembly including an electrode extending from a proximal end to a distal end of the stylet, where the electrode is configured to transmit ECG signals to an ECG system. The stylet further includes a magnetic assembly producing a magnetic field and an elongate coil extending proximally away from the distal end of the stylet. The coil defines a lumen that contains the magnetic assembly.

The method further includes connecting the ECG sensor assembly to an ECG system, advancing the catheter along a vasculature of the patient, discontinuing advancement of the catheter upon an indication via an ECG signal that a tip of the stylet is disposed within the superior vena cava, and removing the stylet from the lumen of the catheter.

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.

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.

The directional terms "proximal" and "distal" are used herein to refer to opposite locations on a medical device. The proximal end of the device is defined as the end of the device closest to the end-user and further 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 longitudinal direction of the device, or the end furthest from the end-user and more near the patient.

<FIG> depicts various features of a catheter placement system ("system") <NUM>, which is generally directed to a catheter placement system configured for accurately placing a catheter within the vasculature of a patient <NUM>. The catheter placement system <NUM> employs three modalities for improving catheter placement accuracy: <NUM>) ultrasound-assisted guidance for introducing the catheter into the patient's vasculature; <NUM>) a tip location/navigation system ("TLS") for magnetically-based tracking of the catheter tip; and <NUM>) ECG signal-based catheter tip guidance. The combination of the three modalities above enables the catheter placement system <NUM> to facilitate catheter placement within the patient's vasculature with a relatively high level of accuracy, i.e., placement of the distal tip of the catheter in a predetermined and desired position. Moreover, because of the ECG-based guidance of the catheter tip, correct tip placement may be confirmed without the need for a confirmatory X-ray. This, in turn, reduces the patient's exposure to potentially harmful x-rays, the cost and time involved in transporting the patient <NUM> to and from the x-ray department, costly and inconvenient catheter repositioning procedures, etc..

The combined features of the system <NUM> are integrated into a single device for use by a clinician placing the catheter <NUM>. Integration of the three modalities into a single device simplifies the catheter placement process and results in relatively faster catheter placements. The integrated catheter placement system <NUM> enables ultrasound, TLS, and ECG activities to be viewed from a single display of the integrated system. Some systems and methods of TLS and ECG based guidance are described in <CIT>, titled "Method and system of utilizing ECG signal for central venous catheter tip positioning," and <CIT>, titled "Integrated system for intravascular placement of a catheter. " Additional disclosure of stylets and catheters for use with a TLS system and ECG based guidance can be found in the following <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

<FIG> further depicts various components of the system <NUM>, including a console <NUM>, display <NUM>, probe <NUM>, and sensor <NUM>. <FIG> shows the general relation of these components to a patient <NUM> during a procedure to place a catheter <NUM> into the patient vasculature through a skin insertion site <NUM>. The catheter <NUM> generally includes a proximal portion <NUM> that remains exterior to the patient <NUM> and a distal portion <NUM> that resides within the patient vasculature after placement is complete. The system <NUM> is employed to ultimately position a distal tip 76A of the catheter <NUM> in a desired position within the patient vasculature. In some embodiments, the desired position for the catheter distal tip 76A is proximate the patient's heart, such as in the lower one-third (<NUM>/3rd) portion of the Superior Vena Cava ("SVC"). Of course, the system <NUM> can be employed to place the catheter distal tip 76A in other locations. The catheter proximal portion <NUM> further includes a hub 74A that provides fluid communication between the one or more lumens of the catheter <NUM> and one or more extension legs 74B extending proximally from the hub.

A stylet <NUM> is removably loaded into the catheter <NUM> and employed during insertion to position the distal tip 76A of the catheter in a desired location within the patient vasculature. The stylet <NUM> may be pre-loaded within a lumen of the catheter <NUM> in one embodiment such that the distal end 130B is substantially flush, or co-terminal, with the catheter opening at the distal end 76A thereof. Note that, though described herein as a stylet, in other embodiments a guidewire or other catheter guiding apparatus could include the principles of the embodiment described herein.

<FIG> shows the stylet <NUM> removed from the catheter <NUM>. Reference is now made to <FIG> in describing various details of the stylet <NUM>. As shown, the stylet <NUM> defines a proximal end 230A and a distal end 230B and includes an ECG sensor assembly <NUM> and a magnetic assembly <NUM>. A connector <NUM> is included at the proximal end 230A, and the tether <NUM> extends distally from the connector <NUM> and attaches to a handle <NUM>. A core wire <NUM> extends distally away from the handle <NUM>. Each of the assemblies and components of the stylet <NUM> are described in detail below.

The handle <NUM> is provided to enable insertion/removal of the stylet <NUM> from the catheter <NUM>. In embodiments where the core wire <NUM> is torqueable, the handle <NUM> further enables the core wire <NUM> to be rotated within the lumen of the catheter <NUM>, to assist in navigating the catheter distal portion through the vasculature of the patient <NUM>.

The handle <NUM> attaches to a distal end of the tether <NUM>. In the present embodiment, the tether <NUM> is a flexible, shielded cable housing one or more conductors <NUM> (e.g., wires) electrically connected to both the core wire <NUM> and the connector <NUM>. As such, the tether <NUM> provides a conductive pathway from the distal portion of the core wire <NUM> through to the tether connector <NUM> at proximal end 230A of the stylet <NUM>. The connector <NUM> may be configured for operable connection to the TLS sensor <NUM> on the patient's chest for assisting in navigation of the catheter distal tip 76A to a desired location within the patient vasculature. A catheter engagement section <NUM> of the stylet <NUM> extends between the distal end 230B and the handle <NUM>.

<FIG> illustrate details of the catheter engagement section <NUM> of stylet <NUM>. <FIG> illustrates a side view of the catheter engagement section <NUM>. As shown in <FIG>, the catheter engagement section <NUM> includes a proximal portion <NUM> and a distal portion <NUM>. The proximal portion <NUM> extends distally from the handle <NUM> to a junction point <NUM> and the distal portion <NUM> extends distally from the junction point <NUM> to the distal end 230B. The distal portion <NUM> includes a distal tip portion <NUM> extending proximally away from the distal end 230B and a transition portion <NUM> extending distally away from the junction point <NUM>.

As described above, the stylet <NUM> includes a core wire <NUM> defining an elongate shape extending distally away from the handle <NUM> along the proximal portion <NUM> and at least partially along the distal portion <NUM>. A coil <NUM> and a sheath <NUM> extend along the distal portion <NUM> as further described in detail below. The core wire <NUM> is composed of a suitable stylet material including stainless steel or a memory material such as, in one embodiment, a nickel and titanium-containing alloy commonly known by the acronym "nitinol. " Although not shown here, in some embodiments, the stylet <NUM> may include one or more pre-shaped (e.g., curved) configurations along the catheter engagement section <NUM> so as to urge the distal portion of the catheter <NUM> into similar corresponding pre-shaped configurations. In other embodiments, the core wire <NUM> includes no pre-shaping.

<FIG> is a detail view of the catheter engagement section <NUM> at the junction point <NUM>. As shown in <FIG>, the core wire <NUM> extends proximally away from the junction point <NUM> having a first cross-sectional diameter <NUM>. The coil <NUM> and the sheath <NUM> extend distally away from the junction point <NUM>. A distal portion of the core wire <NUM> extends distally away from the junction point <NUM> and is disposed within a lumen <NUM> of the coil <NUM> (as shown in <FIG>). In some embodiments, the sheath <NUM> extend proximally away from the junction point <NUM> covering at least a portion of the core wire <NUM>.

The coil <NUM> extends along the distal portion <NUM> from the junction point <NUM> to the distal end 230B. The coil <NUM> defines flexibility and stiffness characteristics of the distal portion <NUM> so that the stylet <NUM> may follow a curved pathway of the vasculature without causing injury to the internal wall of the vasculature. The coil <NUM> may also define robustness and/or fatigue resistance characteristics of the distal portion <NUM>. In other words, the coil <NUM> may define a reliability of the stylet <NUM> against breakage during use. More specially, the coil <NUM> may prevent breakage of the distal portion <NUM> should the distal portion <NUM> be bent one or more times during use.

Referring to <FIG> and <FIG>, the coil <NUM> is formed of a coil member <NUM>. In some embodiments, the coil <NUM> may include two or more coil members <NUM>. The structural properties (i.e., the cross-sectional shape and material) of the coil member <NUM> may at least partially define the flexibility and/or robustness of the distal portion <NUM>. For example, a coil member <NUM> having a thick cross-section may define a flexibility and/or robustness of the distal portion <NUM> that is less than a coil member <NUM> having a thin (i.e., less thick) cross-section. A cross-sectional shape of the coil member <NUM> may be round or non-round. In the illustrated embodiment, the coil member includes a rectangular cross-sectional shape having a width <NUM> and a thickness <NUM>. In the illustrated embodiment, the width <NUM> of the coil member <NUM> may be between about <NUM> and <NUM>. In other embodiments, the width <NUM> may be between about <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>. In the illustrated embodiment, the thickness <NUM> of the coil member <NUM> may be between about <NUM> and <NUM>. In other embodiments, the thickness <NUM> may be between about <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM> or <NUM> and <NUM>. In some embodiments, the coil member <NUM> may include a round shape. In such embodiments, the diameter may be between about <NUM> and <NUM>. In other embodiments, the diameter may be between about <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>. In some embodiments, the coil member <NUM> may be formed of multiple wire filaments forming a cable, such as a braided cable, for example.

The coil <NUM> also defines a pitch <NUM>, i.e., spacing of adjacent windings of the coil <NUM>. In some embodiments, the coil <NUM> may be configured so that windings of the coil <NUM> are located immediately adjacent one another, i.e., so that adjacent windings are in contact with each other. In other embodiments, the coil <NUM> may be configured to define a space or separation between adj acent windings. In some embodiments, the pitch <NUM> of the coil <NUM> may be between about <NUM> and <NUM>. In other embodiments, the pitch <NUM> may be between about <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>.

In some embodiments, the width <NUM> and/or pitch <NUM> of the coil <NUM> may vary along the distal portion <NUM>, i.e., the length of the coil <NUM>. In some embodiments, the width <NUM> and/or pitch <NUM> may be inter-related. For example, a longer width <NUM> may define a longer pitch <NUM> and a shorter width <NUM> may define a shorter pitch <NUM>. As may be appreciated by one of ordinary skill, the width <NUM> combined with the pitch <NUM> may at least partially, and in some embodiments substantially define, a flexibility and/or robustness of the stylet <NUM> along the distal portion <NUM>. As the distal portion <NUM> is advanced along the vasculature, the distal portion <NUM> may assume a curved shape having different bending radii. For example, the bending radius along the distal tip portion <NUM> may be shorter than a bending radius along the transition portion <NUM>. As such, it may be advantageous for the coil <NUM> to have a shorter width <NUM> and a corresponding shorter pitch <NUM> along the distal tip portion <NUM> than along the transition portion <NUM> to define a greater flexibility and/or robustness along the distal tip portion <NUM>. By varying the width <NUM> and/or pitch <NUM> along the distal portion <NUM>, the stiffness, flexibility, and robustness may be optimized along the distal portion <NUM>. In a similar fashion, varying the width <NUM> of the coil member <NUM> may also define stiffness, flexibility, and robustness. Further description regarding varying pitch and varying width is provided below in relation to <FIG>.

In the illustrated embodiment, coil <NUM> includes a single coil member <NUM> forming a single helix. In other embodiments, the coil <NUM> may include two, three, four, or more coil members <NUM> arranged in helical orientations. In the illustrated embodiment, the single coil member <NUM> defines a single coil layer. In other embodiments, two or more coil members <NUM> may be co-wound with respect to each other defining a single coil layer. In other embodiments, two or more coil members <NUM> may be co-wound or counter-wound with respect to each other defining more than one layer. In some embodiments, three or more coil members <NUM> may be arranged to define a braided or woven structure of the coil <NUM>.

The coil member <NUM> may be formed of a metallic material such as stainless steel or nitinol (see above). In some embodiments, one or more coil members <NUM> may be formed for a polymeric material. In the illustrated embodiment, the coil <NUM> may be configured to conduct electricity from a proximal end to a distal end of the coil <NUM>.

The coil <NUM> is physically coupled with the core wire <NUM>. The coupling between the coil <NUM> and the core wire <NUM> may define an electrical connection between the coil <NUM> and the core wire <NUM>. In the illustrated embodiment, the coil <NUM> may be attached to the core wire <NUM> via a weld <NUM> at a proximal end of the coil <NUM>. In some embodiments, the coupling may include a radial clamping force of the coil <NUM> on the core wire <NUM> defined by interfering dimensions. In other words, in a free state, an inside diameter of the coil <NUM> may be less than the first diameter <NUM> of the core wire <NUM> so that the coil <NUM> exerts a radial inward clamping force on the core wire <NUM> when assembled, i.e. when the core wire <NUM> is disposed within the lumen <NUM> of the coil <NUM>. In other embodiments, the coil <NUM> may be attached to the core wire <NUM> via an adhesive. As may be appreciated by one of ordinary skill, the coil <NUM> may be attached to the core wire <NUM> via any other suitable attachment method and at one or more other locations along an over lapping length of the core wire <NUM> and the coil <NUM>.

<FIG> illustrates a side view of the transition portion <NUM> of the distal portion <NUM> with portions of the coil <NUM> and sheath <NUM> shown in cross-section. As stated above, a distal portion of the core wire <NUM> is disposed within the lumen <NUM> of the coil <NUM>. Along the distal portion, the core wire <NUM> may distally transition from the first diameter <NUM> to a second diameter <NUM>. In the illustrated embodiment, the transition may be defined by a taper <NUM>. In some embodiments, the flexibility and or stiffness of the distal portion <NUM> may be defined by a combination of a flexural stiffness of the core wire <NUM> and a flexural stiffness of the coil <NUM> along the transition portion <NUM>. As may be appreciated by one of ordinary skill, the stiffness of the core wire <NUM> decreases with a decrease in diameter of the core wire <NUM>. In other words, the stiffness of the catheter engagement section <NUM> may gradually decrease along the transition portion <NUM>. The first diameter <NUM> of the core wire <NUM> may be between about <NUM> and <NUM>. In other embodiments, the first diameter <NUM> may be between about <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>. Similarly, the second diameter <NUM> may be between about <NUM> and <NUM>. In other embodiments, the second diameter <NUM> may be between about <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>. A longitudinal taper length <NUM> of the taper <NUM> may be between about <NUM> and <NUM>. In other embodiments, the taper length <NUM> may be between about <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>.

The sheath <NUM> is disposed along an exterior of the coil <NUM> from the junction point <NUM> to the distal end 230B. The sheath <NUM> may provide for a smooth outside surface and/or a low-friction outside surface of the distal portion <NUM> to facilitate insertion of the distal portion <NUM> within the catheter <NUM>. The sheath <NUM> may be formed of an extruded tube into which the coil <NUM> is inserted during assembly. In some embodiments, sheath material may be applied to the coil <NUM> in a liquid state so that the sheath <NUM> is formed upon curing/hardening of the sheath material. In other embodiments, the sheath <NUM> may be formed of a shrinkable tube. In such an embodiment, the assembly process may include placing the coil <NUM> within the shrinkable tube and thereafter shrinking the shrinkable the tube onto the coil <NUM>. In still other embodiments, the sheath <NUM> may be formed of a tape wrapped around the coil <NUM>. The sheath material may include polyethylene, polypropylene, polytetrafluoroethylene, polyimide or any other suitable polymeric material. In some embodiments, the sheath <NUM> may contribute to the stiffness of the distal portion <NUM>. For example, the sheath <NUM> may facilitate defining a preform shape of the distal portion <NUM>.

While the illustration of <FIG> shows an outside diameter of the sheath being greater than the first diameter <NUM> proximal of the sheath <NUM>, in some embodiments, the catheter engagement section <NUM> may include a substantially constant cross-sectional size (e.g., diameter) across the junction point <NUM>. An outside diameter of the sheath <NUM> may be substantially equal to the first diameter <NUM> of the core wire <NUM>. In such instances, the first diameter <NUM>, the taper <NUM>, the coil member thickness <NUM>, and a sheath thickness <NUM> may be sized and/or longitudinally positioned to define a substantially constant outside diameter across the junction point <NUM>.

<FIG> is a cross-sectional detail illustration of the distal tip portion <NUM>. As stated above, the stylet <NUM> includes the magnetic assembly <NUM> disposed along distal tip portion <NUM> proximate the distal end 230B. The magnetic assembly <NUM> may be configured for use during TLS mode of the system <NUM>. The magnetic assembly <NUM> includes a plurality of magnetic elements <NUM> disposed within the lumen <NUM> of the coil <NUM>. The plurality of magnetic elements <NUM> may form a linear array of magnetic elements <NUM> extending proximally away from the distal end 230B. In the illustrated embodiment, the magnetic elements <NUM> include <NUM> ferromagnetic magnets of a solid cylindrical shape stacked end-to-end such that end faces <NUM> of the magnetic elements <NUM> are disposed adjacent one another. In other embodiments, however, the magnetic element <NUM> may vary from this design in not only shape, but also composition, number, size, magnetic type, and position within the lumen <NUM> and along the distal tip portion <NUM>. One or more magnetic elements <NUM> are attached to the coil <NUM> so that longitudinal displacement of the magnetic elements <NUM> with the lumen <NUM> may be constrained.

In some embodiments, the magnetic assembly <NUM> may include a space or separation <NUM> between adjacent end faces <NUM> of the magnetic elements <NUM>. The space <NUM> may facilitate a reduced stress and/or strain of the coil <NUM> and/or the sheath <NUM> when the distal tip portion <NUM> is disposed in a curved shape. A reduction in stress or strain along the distal tip portion <NUM> may inhibit breakage of the stylet <NUM> along the distal tip portion <NUM> thereby enhancing reliability of the stylet <NUM>. In some embodiments, the space <NUM> may be defined by a centralized extension <NUM> extending away from one or both end faces <NUM> of one or more magnetic elements <NUM>. In some embodiments, the centralized extension <NUM> may take the form of a radius or chamfer on one or both end faces <NUM>.

The magnetic elements <NUM> are employed along the distal tip portion <NUM> to enable the position of the stylet distal end 230B to be observable relative to the TLS sensor <NUM> placed on the patient's chest (see <FIG>). The TLS sensor <NUM> is configured to detect the magnetic field of the magnetic elements <NUM> as the stylet <NUM> advances with the catheter <NUM> through the patient vasculature. In this way, a clinician placing the catheter <NUM> is able to generally determine the location of the catheter distal end 76A within the patient vasculature and detect when catheter malposition is occurring, such as advancement of the catheter along an undesired vein, for instance.

As illustrated in <FIG>, the stylet <NUM> may include a distal tip member <NUM> disposed at the distal end 230B. The distal tip member <NUM> may extend beyond distal ends of one or both of the coil <NUM> and the sheath <NUM>. The distal tip member <NUM> may be attached to the coil <NUM>. The distal tip member <NUM> may also be electrically coupled with the coil <NUM>. The distal tip member <NUM> is formed of an electrically conductive material. In some embodiments, the distal tip member <NUM> may be formed of a metallic material such as stainless steel or any other suitable metallic material. In such embodiments, the distal tip member <NUM> may be welded to the coil <NUM>. In other embodiments, the distal tip member <NUM> may be formed of a non-metallic material having electrical conduction properties. For example, the distal tip member <NUM> may include a conductive epoxy. The distal tip member <NUM> may at least partially define and/or increase a conductive surface of the distal end 230B of the stylet <NUM> so as to improve the ability of the stylet <NUM> to detect ECG signals.

The connector <NUM>, the conductors <NUM>, the core wire <NUM>, the coil <NUM>, and the distal tip member <NUM> are all in electric communication with each other to define the ECG sensor assembly <NUM> including an electrical conduction pathway for transmission of ECG signals from the distal end 230B to the proximal end 230A of the stylet <NUM>. As such, ECG sensor assembly <NUM> defines an electrode to facilitate transmission of EGC signals from a fluid of the patient <NUM> (e.g., blood within the superior vena cava) to the ECG sensor <NUM>. The ECG sensor assembly <NUM> enables the stylet <NUM>, disposed in a lumen of the catheter <NUM> during insertion, to be employed in detecting an intra-atrial ECG signal produced by an SA or other node of the patient's heart, thereby allowing for navigation of the distal tip 76A of the catheter <NUM> to a predetermined location within the vasculature proximate the patient's heart. Thus, the ECG sensor assembly <NUM> serves as an aide in confirming proper placement of the catheter distal tip 76A.

In some embodiments, the core wire <NUM> may extend distally to the distal end 230B. In such embodiments, a portion of the core wire <NUM> may be disposed between the magnetic elements <NUM> and an inside luminal surface of the coil <NUM>. The core wire <NUM> is electrically coupled with the distal tip member <NUM> directly and as such, the core wire <NUM> need not be electrically coupled with the coil <NUM>.

As discussed above in relation to <FIG>, the pitch of the coil <NUM> and/or the width of the coil member <NUM> may vary along the distal portion <NUM>. As such, in some embodiments, the pitch may vary along the distal portion <NUM> between the pitch <NUM> adjacent the junction point <NUM> as shown in <FIG> and a pitch <NUM> adjacent the distal end 230B as shown <FIG>. In some embodiments, the pitch <NUM> may be less than the pitch <NUM> to define a flexibility and/or a robustness of the stylet <NUM> at the distal end 230B that is greater than the flexibility and/or robustness adjacent the junction point <NUM>. In some embodiments, the pitch <NUM> may extend along the distal tip portion <NUM> and the pitch <NUM> may gradually transition toward the pitch <NUM> along the transition portion <NUM>.

Similarly, in some embodiments, the width of the coil member <NUM> may vary along the length of the distal portion <NUM> between the width <NUM> adjacent the junction point <NUM> as shown in <FIG> and a width <NUM> adjacent the distal end 230B as shown <FIG>. In some embodiments, the width <NUM> may be less than the width <NUM> to define a flexibility and/or a robustness of the stylet <NUM> at the distal end 230B that is greater than the flexibility and/or the robustness adjacent the junction point <NUM>. In some embodiments, the width <NUM> may extend along the distal tip portion <NUM> and the width <NUM> may gradually transition toward the width <NUM> along the transition portion <NUM>.

<FIG> illustrates a catheter assembly <NUM> including the catheter <NUM> having the stylet <NUM> disposed within a lumen of the catheter <NUM>. In some embodiments, the stylet <NUM> may be disposed with the catheter <NUM> during manufacturing. In other embodiments, the clinical may insert the stylet <NUM> within the catheter <NUM> prior to inserting the catheter into the patient vasculature. In the illustrated embodiment, the stylet <NUM> is disposed within the catheter <NUM> such that the distal end 230B of the stylet <NUM> is substantially co-terminal with the distal tip 76A of the catheter <NUM>, thus placing 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 <NUM> may not be substantially co-terminal with the distal tip 76A of the catheter <NUM>.

In the illustrated embodiment, the catheter assembly <NUM> includes a preformed curve <NUM>. The preformed curve <NUM> may be defined by a preformed curve of the stylet <NUM>, a preformed curve of the catheter <NUM>, or both. In some embodiments of use, the clinician may apply a torque to the handle <NUM> to rotate the stylet <NUM> with respect to the catheter <NUM>. Doing so, may orient the curve <NUM> in a different direction with respect to the hub 74A of the catheter <NUM>. In other embodiments of use, the clinician may simultaneously apply a torque to the handle <NUM> and to the catheter <NUM> to rotate the catheter assembly <NUM> within the vasculature of the patient <NUM>, thereby reorienting the curve <NUM> with respect to the patient <NUM>. In some embodiments, the catheter assembly <NUM> may include more than one preformed curve <NUM>. In other embodiments, the preformed curve <NUM> may be omitted.

In the illustrated embodiment, the stylet <NUM> is inserted within the catheter <NUM> sufficiently to dispose the junction point <NUM> within the catheter <NUM>. In this embodiment, the coil <NUM> and the sheath <NUM> are entirely disposed within the catheter <NUM>. In other embodiments, the junction point <NUM> may be disposed external to the catheter <NUM>, i.e., proximal the catheter hub 74A, so that only a portion of the coil <NUM> and the sheath <NUM> are disposed within the catheter <NUM>.

Any methods disclosed herein include one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified.

In use, the stylet <NUM> may be loaded into a lumen of the catheter <NUM> to define a catheter assembly before catheter placement. Note that the stylet <NUM> can come preloaded in the catheter lumen from the manufacturer, or loaded into the catheter by the clinician prior to catheter insertion. The stylet <NUM> is disposed within the catheter lumen such that the distal end 230B of the stylet <NUM> is substantially co-terminal with the distal tip 76A of the catheter <NUM>, thus placing the distal tips of both the stylet and the catheter in substantial alignment with one another. The co-terminality of the catheter <NUM> and stylet <NUM> enables the magnetic assembly <NUM> to function with the TLS sensor <NUM> in a TLS mode to track the position of the catheter distal tip 76A as it advances within the patient vasculature. Note, however, that for the tip confirmation functionality of the system <NUM>, the distal end 230B of the stylet <NUM> need not be co-terminal with the catheter distal end 76A. Rather, all that is required is that a conductive path between the vasculature and the ECG sensor assembly <NUM> be established such that electrical impulses of the SA node or other node of the patient's heart can be detected. This conductive path in one embodiment can include various components including saline solution, blood, etc..

In one embodiment, once the catheter <NUM> has been introduced into the patient vasculature via the insertion site <NUM> (<FIG>) the TLS mode of the system <NUM> can be employed to advance the catheter distal tip 76A toward its intended destination proximate the SA node. Upon approaching the region of the heart, ECG signals may be transmitted to the system <NUM> via the ECG sensor assembly <NUM>. As the catheter <NUM> and the stylet <NUM> are advanced toward the patient's heart, the electrically conductive ECG sensor assembly <NUM>, including the distal tip member <NUM>, begins to detect the electrical impulses produced by the SA node. As such, the ECG sensor assembly <NUM> serves as an electrode for detecting the ECG signals.

The ECG sensor assembly <NUM> conveys the ECG signals to the TLS sensor <NUM>. The ECG sensor assembly <NUM> is operably connected to the TLS sensor <NUM> via the tether connector <NUM>. As described, the ECG signal can then be processed and depicted on the system display <NUM> (<FIG>). Monitoring of the ECG signal received by the TLS sensor <NUM> and displayed by the display <NUM> enables a clinician to observe and analyze changes in the signal as the catheter distal tip 76A advances toward the SA node.

The ECG sensor assembly <NUM> and magnetic assembly <NUM> can work in concert in assisting a clinician in placing a catheter <NUM> within the vasculature. Generally, the magnetic assembly <NUM> of the stylet <NUM> assists the clinician in generally navigating the vasculature from initial catheter insertion so as to place the distal end 76A of the catheter <NUM> in the general region of the patient's heart. The ECG sensor assembly <NUM> can then be employed to guide the catheter distal end 76A to the desired location within the SVC by enabling the clinician to observe changes in the ECG signals produced by the heart as the ECG sensor assembly <NUM> approaches the SA node. Again, once a suitable ECG signal profile is observed, the clinician can determine that the distal ends of both the stylet <NUM> and the catheter <NUM> have arrived at the desired location with respect to the patient's heart. Once it has been positioned as desired, the catheter <NUM> may be secured in place and the stylet <NUM> removed from the catheter lumen.

Claim 1:
A stylet (<NUM>) for placing a catheter (<NUM>) in a vasculature of a patient, comprising:
an ECG sensor assembly (<NUM>) including an electrode extending from a proximal end (230A) to a distal end (230B) of the stylet (<NUM>), the proximal end (230A) configured to couple with an ECG sensor (<NUM>);
a magnetic assembly (<NUM>) disposed along a distal tip portion (<NUM>) of the stylet (<NUM>), the magnetic assembly (<NUM>) producing a magnetic field;
a core wire (<NUM>) extending proximally away from the magnetic assembly (<NUM>); and
a coil (<NUM>) defining a lumen (<NUM>), the coil (<NUM>) extending along a distal portion (<NUM>) of the stylet (<NUM>),
wherein a distal portion of the core wire (<NUM>) is disposed within the lumen (<NUM>),
wherein the magnetic assembly (<NUM>) comprises a plurality of magnet elements (<NUM>) disposed within the lumen (<NUM>),
wherein one or more magnet elements (<NUM>) are attached to the coil (<NUM>).