Dialyzer sheath assembly having an interlock arrangement

Abstract

A sheath assembly (100) is provided, including an expandable introducer sheath (130) and a dilator assembly (200). The sheath assembly (100) includes an expandable sheath (130) having a stepped feature (360) inside its distal opening; the dilator assembly (200) includes a dilator body (210) and an interlock (240) including a gripping surface (244) configured to engage with the stepped feature of the expandable sheath. Upon engagement with the gripping surface, the stepped feature resists further relative motion, preventing the dilator body from exiting the distal end of the expandable sheath. The nature of the interlocking engagement between the stepped feature and the gripping surface allows the dilator to be used to extend and maintain tension on the expandable sheath during insertion into a patient, and then be retracted from the expandable sheath simply by pulling the dilator in the opposite direction. The dilator assembly (200) also includes a dilator hub (230) having a spring mechanism (270) configured to achieve and maintain a desired tension on the expandable sheath and prevent overextension of the expandable sheath when the dilator (210) is inserted into the expandable sheath. TIFF2023513485000002.tif85157

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 62 / 969,318, filed on February 3, 2020, the disclosure of which is incorporated herein by reference in its entirety. This application is related to U.S. Patent Application Publication No. 2019 / 0247627A1, entitled "Expandable Introducer Sheath for Medical Device", filed on February 15, 2019, as U.S. Patent Application No. 16 / 277,378, the disclosure of which is incorporated herein by reference. This application is also related to U.S. Patent Application Publication No. 2018 / 0256859A1, entitled "Expandable Introducer Sheath for Medical Device", filed on March 9, 2018, as U.S. Patent Application No. 15 / 917,042, the disclosure of which is incorporated herein by reference.

Background Art

[0002] Background Intracardiac heart pump assemblies can be introduced surgically or percutaneously into the heart and used to pump blood from one location in the heart or circulatory system to another location in the heart or circulatory system. For example, when deployed within the heart, an intracardiac pump can pump blood from the left ventricle of the heart into the aorta or from the inferior vena cava into the pulmonary artery. The intracardiac pump can be driven by a motor (and associated drive cable) located outside the patient's body or an on - board motor located within the patient's body. Some intracardiac blood pump systems can operate in parallel with the native heart to supplement cardiac output and partially or completely relieve the load on the components of the heart. Examples of such systems include devices of the IMPELLA® family (Abiomed, Inc., Danvers Mass).

[0003] In one common approach, an intracardiac blood pump is inserted into the femoral artery by a catheter procedure that uses a sheath, such as a peel-away introducer sheath. Alternatively, the sheath can also be inserted into any other location, such as a location in the femoral vein or any path for delivering a pump to support either the left or right side of the heart.

[0004] The introducer sheath can be inserted into the femoral artery from the arteriotomy to create an insertion path for the pump assembly. Then, a portion of the pump assembly is advanced through the lumen of the introducer and into the artery. Once the pump assembly is inserted, the introducer sheath is peeled away. Next, a repositioning sheath is advanced from above the pump assembly and into the arteriotomy. Exchanging the introducer sheath for a repositioning sheath during insertion of the medical device can reduce limb ischemia and bleeding at the skin insertion site (and / or the intravascular insertion site) because the sheath is better secured to the patient when used with a hemostatic valve.

[0005] Commercially available tear-away introducer sheaths are not radially expandable, so the inner diameter of the introducer sheath must always be large enough to receive the largest diameter portion of the pump assembly, e.g., the pump head (even if other parts of the pump assembly, such as the catheter, have a significantly smaller diameter). In this example, the introducer creates an opening with an outer diameter wider than necessary to pass the pump catheter into the blood vessel. The introducer sheath is then peeled away or torn away and replaced with a repositioning sheath of smaller profile. Removing the introducer sheath by peeling away presents several challenges. For example, if the introducer is detached too easily and / or too early, it may cause bleeding or vascular complications. Some introducers may also require excessive force to tear away for removal. If the physician applies too much force, there is a risk of inadvertently moving the position of the pump within the heart when the introducer is finally detached. This configuration also complicates the design of the hemostatic valve located in the hub of the introducer, which also needs to be detached. Additionally, the peel-away introducer sheath may create a larger vascular opening after the system is removed, which can make vascular sealing difficult.

[0006] Medical introducers for uses other than the insertion of a heart pump have an expandable sheath body that can expand radially to permit passage of a percutaneous device into a patient's vasculature. These existing expandable introducers are for relatively short-term use and can be designed to prevent thrombus formation between the sheath body and the indwelling catheter.

[0007] These introducers are inserted in a state having an inner diameter smaller than the outer diameter of the device to be introduced. The introducer, when expanded, enables passage of the device through the sheath into the vasculature and can then contract again after the device has passed through. At the state of the art, these expandable introducers require unique expandable features, such as longitudinal folds or creases or lumens for injecting a fluid (e.g., saline) to transition from a compressed state to an expanded state. Since these existing expandable introducers are intended for relatively short-term use, it can be said that thrombus formation outside the introducer sheath is unlikely to occur. However, if left in for a longer time (e.g., more than 1 hour, more than 2 hours, more than 6 hours, more than 1 day, more than 2 days, more than 1 week), there is a risk that thrombus will form on the outer surface of the expandable sheath mesh and will later be carried into the bloodstream. In addition, some commercially available expandable sheaths are completely flexible and thus do not provide any rigidity within their structure, thereby causing kinking or buckling during the insertion or removal of a percutaneous medical device. Summary of the Invention

[0008] Summary The present technology relates to an expandable introducer sheath having an interlock dilator. More specifically, the present technology provides an expandable sheath having a stepped shape inside its distal opening and a dilator having an interlock including a gripping surface configured to engage the stepped shape of the expandable sheath. The stepped shape, when engaged with the gripping surface, resists further relative movement and prevents the body of the dilator from exiting the distal end of the expandable sheath. The nature of the interlock engagement between the stepped shape and the gripping surface allows the dilator to be used to extend the expandable sheath during insertion into a patient and maintain tension thereon, and then be withdrawn from the expandable sheath by simply pulling the dilator in the opposite direction. The present technology also provides a dilator hub having a spring mechanism configured to achieve a desired tension on the expandable sheath, maintain the tension, and prevent overextension of the expandable sheath when the dilator is inserted into the expandable sheath.

[0009] One aspect of the present disclosure relates to an apparatus including an expandable sheath and a dilator. The expandable sheath includes a cylindrical or substantially cylindrical expandable frame having a proximal opening, a distal opening, an inner surface, and an outer surface. The expandable sheath further includes a material covering an outer surface of the expandable frame and a portion of the inner surface of the expandable frame and forming a stepped shape within the distal opening, the stepped shape having a first surface that abuts the inner surface of the expandable frame and is oriented at a first angle with respect to the inner surface of the expandable frame. The dilator includes a cylindrical or substantially cylindrical body, a tapered tip, and an interlock between the body and the tapered tip. The interlock has a first cylindrical section having a first outer diameter, a second cylindrical section having a second outer diameter smaller than the first outer diameter, and a gripping surface that abuts the first cylindrical section and is oriented at a second angle with respect to the first cylindrical section. The dilator is configured to be inserted into the expandable sheath through the proximal opening of the expandable frame. The gripping surface is configured to engage the first surface to prevent the body of the dilator from exiting the expandable frame through the distal opening.

[0010] In some aspects, the device may further include a sheath hub configured to secure an expandable sheath proximate to a distal opening of the expandable frame, and a dilator hub. The dilator hub includes a dilator insert mold configured to secure a body of the dilator; a spring configured to engage the dilator insert mold and resist movement of the dilator insert mold within the dilator hub; and one or more latches configured to lock the dilator hub to the sheath hub.

[0011] In some aspects, the interlock further includes a tapered section that abuts the second cylindrical section. In some aspects, the tapered section is further configured to engage a portion of the material proximate to the distal opening of the expandable frame.

[0012] In some aspects, the first angle is 90°. In other aspects, the first angle is less than 90°.

[0013] In some aspects, the second angle is 90°. In other aspects, the second angle is less than 90°.

[0014] In some aspects, the step shape has a radial height of 0.1 mm to 5 mm.

[0015] In some aspects, the material is a polymer such as thermoplastic polyurethane.

[0016] In some aspects, the expandable frame is a braided material and may include nitinol strands.

[0017] In some aspects, the expandable sheath further includes a coating applied to the expandable frame and the material, such as a lubricious coating.

[0018] In some aspects, the interlock is formed of stainless steel and may further be coated with a polymer. In other aspects, the interlock is formed of a polymer.

[0019] In some aspects, the tapered tip is formed of a polymer such as a polyether block amide.

Brief Description of the Drawings

[0020]

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Modes for Carrying Out the Invention

[0021] Detailed Description Aspects of the present disclosure are described in detail with reference to the drawings, in which like reference numerals identify like or identical elements. It should be understood that the disclosed aspects are merely examples of the present disclosure, which can be embodied in various forms. To avoid obscuring the present disclosure with unnecessary detail, well-known functions or structures are not described in detail. Accordingly, the specific structural and functional details disclosed herein should not be construed as limiting, but rather as a representative basis for teaching one skilled in the art how to use the present disclosure in fact any appropriately detailed structure in various ways for the purpose of claims and.

[0022] To provide an overall understanding of the systems, methods, and devices described herein, specific exemplary aspects are described. The aspects and features described herein are specifically described with respect to use in connection with an intracorporeal heart pump system, but it will be understood that all of the components and other features outlined below may be combined with each other in any suitable manner and adapted and applied to other types of medical devices, such as electrophysiology research and catheter ablation devices, angioplasty and stent placement devices, angiography catheters, peripheral access central catheters, central venous catheters, midline catheters, peripheral catheters, inferior vena cava filters, abdominal aortic aneurysm treatment devices, thrombectomy devices, TAVR delivery systems, cardiac treatment and cardiac assist devices, such as balloon pumps, surgically implanted cardiac assist devices, and other venous or artery-based introducer catheters and devices.

[0023] The systems, methods, and devices described herein provide an expandable sheath assembly for inserting a medical device (e.g., an intracardiac pump) into a blood vessel through a vascular opening. The expandable sheath assembly includes a dilator assembly and a sheath body having an inner surface and an outer surface, the inner surface defining a lumen that extends between a proximal end and a distal end of the sheath. Optionally, the expandable sheath assembly may include a hemostasis stylet. The expandable sheath assembly (including the sheath body, the dilator assembly, and optionally the hemostasis stylet) is particularly advantageous over existing expandable sheath assemblies for patients with coronary artery disease (CAD) and peripheral artery disease who exhibit arterial calcification and tortuosity, which make the delivery of introducer sheaths and catheters difficult. The expandable sheath assembly herein is easier to insert than conventional assemblies due to a reduced insertion profile, increased flexibility, reduced friction, and reduced risk of kinking under load. The reduced insertion profile minimizes insertion-related complications, minimizes elongation and loading on the vascular opening, and minimizes the risk of limb ischemia. The structure of the sheath body described herein provides sufficient axial stiffness for pushability and buckling resistance while maintaining bend flexibility and kink resistance, reduces frictional forces to prevent "finger trapping", and further provides an improvement over existing introducer sheath bodies by having a smooth inner surface with a thin coating thickness that reduces the force required to expand the sheath (compared to the force required to expand a sheath having no coating bias) and / or reduces the risk of thrombus formation during longer-term use while allowing the sheath to expand and contract as desired, and by having a smooth outer surface that reduces friction between the sheath body and the device inserted therein. Additionally, the structure of the sheath body described herein is capable of interfacing with the dilator assembly to hold the sheath body in a fixed position for insertion into a body cavity by longitudinally restraining or capturing a portion of the sheath body.This restraint or capture of the sheath body facilitates the insertion of an expandable sheath body combined with a dilator assembly without damaging the expandable sheath body or changing its properties.

[0024] The sheath body can expand between different states to receive a medical device. For example, the sheath body extends to a first smaller diameter state during insertion and relaxes to a second larger diameter state once the desired position is reached, allowing a portion of the medical device (a portion having a cross-sectional area larger than the cross-sectional area of the lumen in the first state) to pass through the lumen. In different configurations, the sheath further expands between its resting state when in its desired position and a larger diameter state when the medical device is passed through. In any configuration, the expandable sheath assembly herein does not require additional elements compared to a standard introducer: no external balloon, no creases in the expandable sheath body, no second sheath for delivery. This can be advantageous over existing expandable sheath assemblies by simplifying the use of the expandable sheath assembly (e.g., reducing the necessary steps, shortening the time).

[0025] In addition, the instantaneous expansion of the sheath body from the extended state to the relaxed state (or from the relaxed state to the expanded state) minimizes the size of the opening required when inserting the sheath into the patient's vasculature, such as the arteriotomy. Minimizing the time the sheath body is in the expanded state also results in a smaller opening required to receive the sheath body in the relaxed or collapsed state, minimizing damage to the vessel wall and thereby minimizing thrombotic occlusion of the vessel. The smaller opening also minimizes the time to achieve hemostasis after removal of the medical device. Such expandable sheaths obviate the need for a conventional setup having multiple sheaths, such as peel-away introducer sheaths and repositioning sheaths for introducing a medical device (e.g., an intracardiac pump) into a vessel. Such expandable sheaths also permit, if desired, the use of such conventional setups therewith. If the expandable sheath is placed within the opening of the patient's vessel, it maintains access to the vessel even after the medical device has been removed (if such access is required for other medical procedures). This increases the efficiency of any medical procedure because there is no need to obtain an alternative access or reinsert a second sheath at the same access site. The effective integration of the introducer sheath and repositioning sheath into one device reduces the costs incurred during a medical procedure. Further, because only one sheath is required to obtain arteriotomy access to the vessel, bleeding associated with the long-term use of a percutaneous medical device, such as a heart pump, will be reduced. The integration of the sheath body and dilator assembly with a hemostasis stylet enables titrated hemostasis at the vessel opening. In some embodiments, the hemostasis stylet can be the repositioning sheath that is also used to inhibit blood flow along the expandable sheath and minimize bleeding.

[0026] In addition, the expandable sheath assembly herein is advantageous over existing expandable sheath assemblies in that it allows the user to always remove the pump with the sheath in a fixed position, thereby maintaining guidewire access throughout the procedure.

[0027] An expandable sheath can be delivered into a patient with a small outer profile if it is held in an axially tensioned (extended) state prior to insertion. This has the following major advantages: i) extension to a small insertion profile to minimize insertion-related complications (i.e., bleeding, vascular injury, high insertion forces); and ii) allowing minimization of small-diameter closure and bleeding by minimizing vessel recoil during use by maintaining a "soft" sheath body and instantaneous expansion for interaction at the arteriotomy.

[0028] Conventional expandable sheath delivery systems require a complex mechanism for capturing the distal end of the sheath, locking the sheath to the sheath hub, and extending the sheath. This requires at least two user operations, which are typically device-specific. Since such delivery systems are different from "typical" introducer systems, they may require specific training to use and are at risk of misuse.

[0029] A "typical" introducer system arrives packaged with a separate sheath, a separate dilator, and accessories. The user generally removes the sheath and dilator and pre-flushes each separately with saline to remove air. The user then assembles the introducer system by inserting the dilator into the proximal end of the sheath. The introducer assembly is then ready for use.

[0030] What is described herein is a modification of the distal end of a sheath that enables "locking" a dilator through an "interlock" configuration. By locking the dilator to the sheath in such a manner, an expandable sheath introducer assembly can be inserted into a patient like a typical introducer and retain the advantages of the expandable introducer sheath. This interlock-type expandable introducer sheath assembly is easier to manufacture than those described above and is easier to use because it can be operated in the same manner as a typical introducer sheath assembly.

[0031] FIG. 1 shows a sheath assembly 100 according to aspects of the present technology. The sheath assembly has a hub 110 that locks the sheath in place if the sheath is inserted. The hub 110 operates in cooperation with a cap 120 to secure the sheath body 130 in place. The hub 110 also has a detent 112 (only one is visible) to assist in attaching the hub 110 to a dilator hub 230, as will be further described below. A butterfly / suture pad 140 is configured to assist in attaching the sheath assembly 100 to a patient (e.g., by suturing the assembly to the patient). As can be seen, the distal end of the sheath body 130 has a tapered sheath tip 150. The sheath tip 150 can have a linear taper, a convex taper, a concave taper, or a taper composed of one or more linear, convex, and / or concave sections. The sheath tip 150 can be of any suitable length. In some embodiments, the sheath tip 150 can be 0.1 mm to 5 mm in length. As used herein, the proximal end of the assembly is at the hub / cap end, and the distal end of the assembly is at the tip end. Fluid can be introduced into the assembly via a side arm channel 160, and the flow rate of the fluid into the device can be controlled by a stopcock 170. Also, a hemostatic valve (not shown) may be included within the hub 110 and is configured to prevent blood from leaking out of the patient during insertion and / or removal of an intracardiac blood pump or other components. Any suitable hemostatic valve can be used, an example of which is described and illustrated in U.S. Provisional Patent Application No. 62 / 935,300, which is incorporated herein by reference. Additionally, in some embodiments, the hub 110 can include a foam insert (not shown) disposed immediately adjacent to the hemostatic valve that can be immersed in a lubricant such as silicone, and the components can be lubricated as they are inserted through the foam into the sheath body 130.

[0032] The expandable sheath body 130 includes at least one frame and one coating. The coating can be applied to the outer surface of the sheath body 130 to facilitate passage within the patient, as is known as an outer-diameter biased approach. In some embodiments, the coating can be a polymer such as the polymer material 312 shown and described with reference to FIGS. 8-10. This outer-diameter biased coating advantageously reduces the risk of thrombus formation when inserting the device into the expandable sheath and provides a smooth outer surface that minimizes friction. For example, the use of a smooth outer surface advantageously minimizes the risk of thrombus formation on the surface of the expandable sheath body 130, and the corrugated inner surface minimizes the surface area of the expandable sheath that contacts the device being pushed through, thereby minimizing the associated frictional force. In some embodiments, the corrugated inner surface can be a braided material such as the braided material 314 shown and described with reference to FIGS. 8-10. In some embodiments, an additional lubricious coating can be applied to the inner and / or outer surface of the sheath body 130, i.e., coating the polymer material 312 and / or the braided material 314. The outer-diameter biased coating further advantageously provides a thin coating thickness and requires relatively little force to expand the sheath body 130 compared to the force required to expand a sheath having a non-biased coating. The outer-diameter biased coating also advantageously allows the sheath frame to expand and contract freely. That is, the thin coating thickness is such that the coating does not cover the portions of the frame where the frame elements intersect, so the outer-diameter biased coating does not fix the frame to a constant diameter. For example, in the case of a braided frame having an over-under braiding pattern of braided elements and an outer-diameter biased coating, the outer-diameter biased coating is advantageously thin enough not to cover the overlapping portions of the braided elements. That is, the outer-diameter biased coating does not extend down to the braided elements located under other braided elements in the over-under braiding pattern.

[0033] In some embodiments, the expandable sheath frame may have an expansion mechanism that assists the frame in expanding and / or contracting. For example, the strands of a braided sheath frame may be configured with a bias for expanding and / or contracting from a rest position. In accordance with some embodiments, the expansion mechanism allows the strands to slide relative to each other as the frame expands and contracts.

[0034] The expandable sheath body 130 and the sheath tip 150 can be formed in a variety of ways, including using the configurations and manufacturing methods described in U.S. Patent Application Publication Nos. 2019 / 0247627A1 and 2018 / 0256859A1, which are incorporated herein by reference. For example, the expandable sheath body 130 (and the sheath tip 150) can be manufactured using heat adhesion or an immersion biased towards the outer diameter that can retain its desired spring-like expandability while providing a smooth outer surface to the sheath body 130. Specific details of possible configurations of the sheath body 130 and methods of manufacturing them are included in the referenced published applications and are not all repeated herein.

[0035] By using the frame and coating assembly in the above and referenced applications, the expandable sheath body 130 is kink resistant while being able to expand and collapse. This allows the sheath body 130 to expand to allow insertion or retrieval of a medical device and then, after deformation, return to its original shape. Additionally, configuring an expandable sheath for compatibility with a dilator assembly and a stylet assembly aids dilator insertion and removal and improves hemostatic performance. Advantageously, the combination of a dilator assembly, an expandable sheath, and a hemostatic stylet provides a synergistic system that can be used relatively early during a procedure, such as in a catheterization laboratory, rather than later during the procedure, such as during surgery, when pump movement can lead to more serious consequences for the patient. Since the system can be used relatively early during the procedure, potential pump misalignment can be addressed earlier and vascular damage can be reduced.

[0036] Such an expandable sheath body 130 can also eliminate the need for a conventional setup that must have multiple sheaths, such as peel-away introducer sheaths and repositioning sheaths, for introducing a medical device (e.g., an intracardiac pump) into a vascular opening (e.g., an arteriotomy). In that regard, once the expandable sheath body 130 is positioned, it maintains access to the blood vessel even after the medical device has been removed (if such access is needed for other medical procedures). This increases the treatment efficiency of any medical procedure and simplifies the process of inserting components into the patient because it is not necessary to peel away the introducer sheath for insertion of the repositioning sheath each time access to the vascular opening is required. In addition, since it is not necessary to remove the expandable introducer sheath body 130 and replace it with a second repositioning sheath, the risk of premature detachment / separation is essentially eliminated, and the risk of inadvertently (e.g., by overexertion) moving the introduced device is reduced or eliminated. Furthermore, since the expandable introducer sheath is fixed in position once inserted, more accurate repositioning of the medical device can be achieved using the expandable introducer sheath, whereas insertion of a separate repositioning sheath requires multiple steps that increase the likelihood of misplacement of the medical device. Nevertheless, the expandable sheaths described herein may still be used with a repositioning sheath.

[0037] FIG. 2 shows a dilator assembly 200 according to aspects of the present technology. The dilator assembly 200 has a dilator hub 230 at its proximal end, a dilator body 210, an interlock 240, and a dilator tip 220 at its distal end. As can be seen, the dilator tip 220 tapers towards its distal end to facilitate insertion into the patient's vasculature. The dilator hub 230 is configured to engage with the hub 110 of the sheath assembly 100, as further described below.

[0038] Figures 3A and 3B show a cross-sectional view and a perspective view of a portion of the dilator assembly 200 according to aspects of the present technology. In that regard, FIG. 3A is a side cross-sectional view showing how the interlock 240 is attached to the dilator tip 220 and the dilator body 210, and FIG. 3B is an enlarged isometric perspective view of the same assembly. As shown in FIGS. 3A and 3B, the distal end of the interlock 240 is connected to the dilator tip 220 via a flange 241. The flange 241 extends into the proximal end of the dilator tip 220. In some embodiments, the dilator tip 220 may be formed directly on the flange 241. The proximal end of the interlock 240 is connected to the dilator body 210 via a threaded connection. In that regard, the proximal end of the interlock has a threaded male connector 242, which is received by a corresponding threaded female connector 212 on the distal end of the dilator body 210. The threaded male connector 242 and the threaded female connector 212 may have any suitable diameter, pitch, specification, etc. For example, the threaded male connector 242 and the threaded female connector 212 may use standard metric threads such as M1, M2, etc. Moving from proximal to distal, the outer contour of the interlock 240 is defined by a tapered body portion 246 that starts from or near the outer diameter of the dilator body 210 and increases in diameter until it reaches a cylindrical section 247 of a constant diameter. Continuing in the distal direction, a recess 245 with a smaller outer diameter follows the cylindrical section 247, and the transition between the cylindrical section 247 and the recess 245 forms a gripping surface 244. The gripping surface 244 and the recess 245 are configured to engage with a step 316 of the sheath tip 150, as further described below. The lengths of the tapered body portion 246, the cylindrical section 247, and the recess 245 may be any suitable lengths. In some embodiments, the cylindrical section 247 may be 0.5 mm to 20 mm in length. The proximal end of the dilator tip 220 has a transition edge 222. The transition edge 222 may have any suitable outer shape and angle.For example, the transition edge 222 may be a chamfered portion or a combination of flat edges at two or more different angles, may be curved in a concave or convex direction, or may be composed of one or more straight sections, concave sections, and / or convex sections.

[0039] The dilator tip 220, the interlock 240, and the dilator body 210 can be made of any suitable material. In some embodiments, the dilator tip 220 can be formed of a flexible material, such as a polyether block amide (「PEBA」) with a durometer hardness of 40D. In some embodiments, the dilator tip 220 can be formed of other flexible materials, such as PEBA with other hardness ratings, silicone, thermoplastic polyurethane (「TPU」), or other thermoplastic elastomers (「TPE」). In some embodiments, the dilator tip 220 can further include a hydrophilic lubricious coating, such as polyvinylpyrrolidone (「PVP」) or hyaluronic acid (「HA」), or a hydrophobic coating, such as silicone or polytetrafluoroethylene (「PTFE」). In some embodiments, the dilator tip 220 may not have a coating.

[0040] In some embodiments, the dilator body 210 can be formed of a semi-rigid material, such as a PEBA with a durometer hardness of 70D. In some embodiments, the dilator body 210 can be other semi-rigid materials, such as PEBA with other hardness ratings, polyethylene, polypropylene, or polyurethane. In some embodiments, heat can be applied to the threaded female connector 212 of the dilator body 210 to increase its tensile strength and torque resistance.

[0041] In some embodiments, the interlock 240 may be formed of a hard material such as 304 stainless steel. In some embodiments, the interlock 240 may be formed of other hard metals, such as 316 stainless steel, or hard polymers, such as polyetheretherketone ("PEEK"), acrylonitrile butadiene styrene ("ABS"), or polycarbonate. In some embodiments, the interlock 240 may be fully or partially coated, for example, with a polymer. In some embodiments, the interlock 240 may have a coating that is 0.025 to 0.2 mm. In some embodiments, the interlock 240 may have a coating with a durometer hardness of 40A to 70D. In some embodiments, the interlock 240 may have a coating with a coefficient of friction greater than the coefficient of friction of the stainless steel and / or the material selected for the dilator tip 220 or the dilator body 210. In some embodiments, the interlock 240 may not have a coating.

[0042] FIG. 4 shows an isometric view of a dilator hub 230 according to an aspect of the present technology, in which the outer housing 231 (composed of two halves) is shown in a transparent state. As can be seen, the dilator hub 230 has a toothed latch 250 that secures it to the hub 110 of the introducer sheath assembly 100. The proximal end of the dilator body 210 is coupled to a dilator insert mold 280. The dilator insert mold 280 has a flange 282 configured to engage a spring 270 mounted within the proximal end of the dilator hub 230. The spring 270 is configured to allow the dilator insert mold 280 to move proximally during attachment of the dilator hub 230 to the hub 110 of the sheath assembly 100. In that regard, the spring constant of the spring 270 can be selected based on the modulus of elasticity of the sheath body 130 to optimize the amount of tension applied to the sheath body 130 when the dilator hub 230 and the hub 110 are pushed together and attached, and thus the sheath tip 150 is pulled distally. Similarly, the spring 270 can be preloaded to a certain tension or compression to optimize the amount of tension applied to the sheath body 130 when the dilator hub 230 and the hub 110 are pushed together and attached. In that regard, in some embodiments, the spring constant of the spring 270 can be between 0.1 N / mm and 3 N / mm, and the spring can have a stroke of between 1 mm and 20 mm. In some embodiments, the force (including any preload) provided by the spring during attachment of the dilator hub 230 to the hub 110 can be between 5 N and 30 N.

[0043] As shown in FIG. 4, the dilator hub 230 also has a lock 260 configured to engage with a dilator insert mold 280. When the lock 260 engages with the dilator insert mold 280, it prevents the dilator insert mold 280 from moving in the proximal or distal direction. By preventing movement in the proximal direction, the lock 260 prevents the spring 270 from being compressed when the dilator and sheath are inserted into the patient. Advantageously, by matching the spring constant and preload of the spring 270 to the modulus of elasticity of the sheath body 130, when the dilator hub 230 is attached to the hub 110, the sheath body 130 is properly extended, stretched, and thus, the lock 260 (if engaged) maintains the sheath body 130 at this desired extended and stretched location. The lock 260 is configured to automatically "close" or lock when the dilator hub 230 and the sheath body 130 are attached. However, in some embodiments, the lock 260 may alternatively be configured to be manually actuated, such as by a button or switch. Additionally, since the tension of the sheath body 130 naturally resists further movement of the dilator 210 in the distal direction, in some embodiments, the lock 260 may be configured to prevent only movement in the proximal direction.

[0044] FIG. 5 is a cross-sectional view of the dilator hub 230 of FIG. 4 taken along plane A-A of FIG. 4. As can be seen, the lock 260 has teeth 261 and the dilator insert mold 280 has teeth 281. FIG. 5 shows the lock 260 in an "open" position such that the dilator insert mold 280 can move within the dilator hub 230. Although FIG. 5 shows a toothed locking mechanism, the lock 260 can utilize any suitable mechanism for preventing movement of the dilator insert mold 280.

[0045] FIG. 6 is a side cross-sectional view of the dilator hub 230 of FIG. 4 in the process of being attached to the hub 110 of the sheath assembly 100 according to an aspect of the present technology. As can be seen from FIG. 6, all of the toothed latches 250 of the dilator hub 230 are in the open position and are not yet engaged with the detent 112 of the hub 110. Similarly, the lock 260 is shown in the "open" position such that the dilator insert mold 280 can move within the dilator hub 230. In that regard, the dilator insert mold 280 is shown in a state where the dilator hub 230 and the hub 110 are pushed together and attached, and thus the spring 270 has begun to be compressed in the proximal direction as occurs when the sheath tip 150 is pulled distally.

[0046] FIG. 7 shows the dilator hub 230 of FIG. 4 locked to the hub 110 of the sheath assembly 100 according to an aspect of the present technology. As can be seen from FIG. 7, the toothed latch 250 is engaged with the detent 112 in the hub 110 and thus provides a clamping force that prevents the dilator hub 230 from being pulled away from the hub 110. In addition, the lock 260 is shown in the "closed" position where its teeth 261 have moved radially inward within the dilator hub 230 such that the teeth 261 engage the teeth 281 of the dilator insert mold 280. The engagement of the teeth 261 and 281 provides resistance to further pushing of the dilator insert mold 280 proximally into the dilator hub 230. As described above, by tuning the spring constant and preload of the spring 270 relative to the modulus of elasticity of the sheath body 130, the assembly can be configured such that the sheath body 130 receives a desired tension at the point where the dilator hub 230 locks to the hub 110. The lock 260 is then applied (e.g., manually or automatically, as a result of the dilator hub 230 locking to the hub 110), thereby maintaining the sheath body 130 at its desired tension and preventing the dilator insert mold 280 from moving proximally when the dilator and sheath are inserted into the patient.

[0047] FIG. 8 is a side cross-sectional view of the distal end of the sheath assembly 100 showing an example of how the distal end of the sheath body 130 and the sheath tip 150 can be configured. The structure of FIG. 8 will be described with respect to three parts 302, 304, and 306. In the first part 302, the sheath body 130 has a cavity 308 with an inner diameter 310. The outer surface of the first part 302 is a polymer material 312. The inner surface of the first part 302 is a braided material 314. The braided material 314 can be any suitable material as described in the publications above and referenced. In some embodiments, the braided material 314 can be composed of strands of a flexible metal such as nitinol. As described above, in some embodiments, an additional lubricious coating (not shown) may be applied to the inner and / or outer surfaces of the sheath body 130, i.e., covering the polymer material 312 and / or the braided material 314. In some embodiments, the polymer material 312 is thermoplastic polyurethane (“TPU”) and is bonded to the braided material 314 using a thermoforming process. There is a step 316 on the inner surface of the sheath body 130 between the first part 302 and the second part 304. The step 316 forms an angle 324 with the inner surface of the first part 302 and creates a cavity 318 having a second inner diameter 320 that is smaller than the inner diameter 310 of the cavity 308. In FIG. 8, the angle 324 is shown as a right angle, i.e., 90°. However, the angle 324 can be any angle that allows the step 316 to properly engage with the gripping surface 244 of the interlock 240, as further described below. Thus, in some embodiments, the angle 324 can be an obtuse or acute angle (e.g., as shown and described below with reference to FIG. 9). The step 316 can be any suitable height. In some embodiments, the step 316 can be from 0.1 mm to 1 mm.

[0048] In the second portion 304, the braided material 314 of the sheath tip 150 is sandwiched between the polymeric materials 312. As a result, the polymeric materials 312 form both the inner and outer surfaces of the second portion 304. Additionally, as can be seen, at the transition of the sheath body 130 to the sheath tip 150, the outer diameter begins to taper. This tapering begins near the distal end of the first portion 302 and continues through the second portion 304 and the third portion 306. Similarly, the braided material 314 also has both a cylindrical section and a tapered section. As shown in FIG. 8, the tapered section of the braided material 314 begins at the split point between the first portion 302 and the second portion 304. However, in other embodiments, the tapered section of the braided material 314 may begin more proximally (i.e., anywhere within the first portion 302) or distally (i.e., anywhere within the second portion 304 or the third portion 306) than shown in FIG. 8.

[0049] In the third portion 306, the sheath tip 150 is entirely composed of the polymeric material 312. As shown in FIG. 8, the inner surface of the third portion 306 has a transition edge 322 at its distal end. The transition edge 322 is shown as a chamfer in FIG. 8. However, the transition edge 322 may be a fillet or any other suitable contour. Additionally, the transition edge 322 is optional. Thus, in some embodiments, the third portion 306 may have a constant inner diameter equal to the inner diameter 320, and the transition edge 322 may be replaced with a square corner.

[0050] In some embodiments, the surface of the lumen 318 and / or the transition edge 322 may be textured or otherwise configured to reduce friction and adhesion between the sheath tip 150 and other devices passing therethrough, such as the dilator tip 220, the interlock 240, and intervention devices introduced into the sheath assembly 100, such as an intracardiac heart pump. The texturing may be applied to the surface of the lumen 318 and / or the transition edge 322 in any suitable manner. For example, the texturing may be applied to the sheath tip 150 by forming it using a mandrel that is itself textured, such as by machining, sandblasting, shot peening, chemical etching, laser surface texturing, or the like. In that regard, in some examples, the surface of the lumen 318 and / or the transition edge 322 may be crosshatched, knurled, or dimpled. In some examples, the surface of the lumen 318 and / or the transition edge 322 may have a pattern composed of dashed or solid lines that extend in any direction, such as longitudinally, circumferentially, or at any angle therebetween. In some examples, the surface of the lumen 318 and / or the transition edge 322 may have a pattern of lines that extend in any direction, such as longitudinally, circumferentially, or at any angle therebetween, that are curved, sinusoidal, serrated, or any combination thereof. In some examples, the surface of the lumen 318 and / or the transition edge 322 may have one or more convex or concave grooves that extend in any direction, such as longitudinally, circumferentially, or at any angle therebetween. Similarly, in some examples, the surface of the lumen 318 and / or the transition edge 322 may be coated or otherwise composed of a material that reduces friction or adhesion. For example, the surface of the lumen 318 and / or the transition edge 322 may have a lubricious coating, or the polymeric material 312 may be a material having an appropriately low coefficient of friction, such as PTFE. The surface of the lumen 318 and / or the transition edge 322 may incorporate any combination of the various options described above, including combinations of textured shapes, as well as lubricious coatings and / or low friction materials.

[0051] FIG. 9 is a side cross-sectional view of the distal end of the sheath assembly 100 showing a further example of how the distal end of the sheath body 130 and the sheath tip 150 can be configured. All features of the embodiment of FIG. 9 are the same as those shown in FIG. 8, except for the transition between the inner diameters 310 and 320. In that regard, in FIG. 9, the angle 324 between the inner surface of the first portion 302 and the step 316 is an acute angle, i.e., less than 90°. Again, the angle 324 can be any angle that allows the step 316 to properly engage with the gripping surface 244 of the interlock 240, as further described below. For example, in some embodiments, the angle 324 can be an acute angle, such as between 30° and 89°.

[0052] Figure 10A is a cross-sectional view of an embodiment of a dilator body 210, an interlock 240, and a dilator tip 220 according to aspects of the present technology. Figure 10B shows an enlarged cross-sectional view of the components of Figure 10A engaged with the sheath tip 150 of Figure 8. Figures 10A and 10B show a generalized aspect in which the flange 241 and threaded male connector 242 of the interlock 240 and the threaded female connector 212 of the dilator body 210 are omitted. One of ordinary skill in the art will understand that the dilator body 210, the interlock 240, and the dilator tip 220 can be coupled to each other in a variety of ways, including those shown in Figures 3A and 3B above. In that regard, the dilator body 210, the interlock 240, and the dilator tip 220 can be coupled, adhered, or welded to each other. Similarly, the dilator body 210, the interlock 240, and the dilator tip 220 may be coupled using additional fasteners. In some embodiments, one or more of the dilator body 210, the interlock 240, and the dilator tip 220 may be formed as a unitary structure or joined as a result of overmolding. To reach the assembly of Figure 10B, the dilator tip 220 is pushed through the distal end of the sheath tip 150. As described above, the sheath tip 150 can be configured to expand when the tapered dilator tip 220 is passed through it. Thus, the sheath tip 150 can be configured to expand to pass over the transition edge 222 of the dilator tip 220 and then contract naturally again when it reaches the narrower recess 245 of the interlock 240. As the dilator tip 220 is continuously pushed in the distal direction, the step 316 of the sheath tip 150 contacts the gripping surface 244 of the interlock 240 as shown in Figure 10B. The gripping surface 244 abuts the surface of the recess 245 at an angle 248. Similar to angle 324, angle 248 can be any angle that allows the step 316 to properly engage the gripping surface 244 of the interlock 240 as described above. Thus, in some embodiments, angle 248 can be a right angle. In some embodiments, angle 248 can be an acute angle, for example, between 30° and 89°.In some embodiments, angle 248 may be an obtuse angle. In some embodiments, as in FIG. 10B, angle 248 may be different from angle 324. In some embodiments, as in FIG. 11 showing an enlarged cross-sectional view of the component of FIG. 10A engaged with the sheath tip 150 of FIG. 9, angle 248 may be the same as or substantially the same as angle 324. All features of the embodiment of FIG. 11 are the same as those shown in FIG. 10B, except that angle 248 is the same as or substantially the same as angle 324 in the embodiment of FIG. 11.

[0053] As shown in FIGS. 10B and 11, if the gripping surface 244 of the interlock 240 engages the step 316 of the sheath tip 150, further pushing the dilator tip 220 distally pulls the sheath tip 150 and, in turn, begins to apply tension to the sheath body 130, stretching and narrowing it. Stretching the sheath body 130 in this way advantageously reduces its insertion profile, which helps to minimize patient complications (such as bleeding, vascular injury, high insertion force). At this point, the dilator assembly 200 can be used to insert the sheath tip 150 and the sheath body 130 into the patient's vasculature.

[0054] If the sheath body 130 is properly positioned within the patient's vasculature, the toothed latch 250 can be pushed and the dilator hub 230 pulled proximally to unlock the dilator hub 230 from the hub 110 of the sheath assembly 100. By continuing to retract the dilator assembly 200 proximally with the sheath tip 150 remaining stationary, the engagement surface 244 is disengaged from the step 316, and the transition edge 222 of the dilator tip 220 passes beyond the sheath tip 150, allowing the dilator assembly 220 to be fully withdrawn from the patient. The sheath assembly 100 can then be used to introduce an intracardiac blood pump and / or other components into the patient's vasculature as further described above. In particular, after the dilator assembly 200 has been removed, the sheath body 130 is no longer under tension and can relax into a shorter, wider configuration that aids in the insertion of such components.

[0055] From the foregoing and with reference to the various drawings, those skilled in the art will understand that specific changes can be made to the present disclosure without departing from the scope thereof. Although some aspects of the present disclosure are shown in the drawings, the present disclosure is intended to be broad as permitted by the art and as such is not intended to be limited thereto. Accordingly, the above description should not be construed as limiting, but rather as merely illustrative of particular aspects. Those skilled in the art will envision other changes within the scope and spirit of the claims appended hereto.

Claims

**Claim 1**: An expandable sheath comprising: a cylindrical or substantially cylindrical expandable frame having a proximal opening, a distal opening, an inner surface, and an outer surface; and a material covering a portion of the outer surface of the expandable frame and a portion of the inner surface of the expandable frame, the material having a stepped shape with a first surface that abuts the inner surface of the expandable frame and is oriented at a first angle with respect to the inner surface of the expandable frame, the stepped shape being formed within the distal opening; an expandable sheath including the material; a dilator comprising: a cylindrical or substantially cylindrical body, a tapered tip, and an interlock between the body and the tapered tip, the interlock having a first cylindrical section having a first outer diameter, a second cylindrical section having a second outer diameter smaller than the first outer diameter, and a gripping surface that abuts the first cylindrical section and is oriented at a second angle with respect to the first cylindrical section; a dilator including the interlock; an apparatus including: the dilator configured to be inserted into the expandable sheath through the proximal opening of the expandable frame; the gripping surface configured to engage the first surface to prevent the body of the dilator from exiting the expandable frame through the distal opening. **Claim 2**: The apparatus of claim 1, further comprising: a sheath hub configured to fix the expandable sheath in proximity to the distal opening of the expandable frame; a dilator hub comprising: a dilator insert mold configured to fix the body of the dilator, a spring configured to engage the dilator insert mold and resist movement of the dilator insert mold within the dilator hub, and one or more latches configured to lock the dilator hub to the sheath hub. a dilator hub including the components; The apparatus of claim 1, further including the dilator hub. **Claim 3**: The apparatus of claim 1, wherein the interlock further includes a tapered section that abuts the second cylindrical section. **Claim 4**: The apparatus of claim 3, wherein the tapered section is configured to engage a portion of the material proximate the distal opening of the expandable frame. **Claim 5**: The apparatus of claim 1, wherein the first angle is 90°. **Claim 6**: The apparatus of claim 1, wherein the first angle is less than 90°. **Claim 7**: The apparatus of claim 1, wherein the second angle is 90°. **Claim 8**: ​ ​ ​ ​ ​ The apparatus according to claim 1, wherein the second angle is less than 90°.

9. The apparatus according to claim 1, wherein the step shape has a radial height of 0.1 mm to 5 mm.

10. The apparatus according to claim 1, wherein the material is a polymer.

11. The apparatus according to claim 10, wherein the material is thermoplastic polyurethane.

12. The apparatus according to claim 1, wherein the expandable frame is a braided material.

13. The apparatus according to claim 12, wherein the braided material includes nitinol strands.

14. The apparatus according to claim 1, wherein the expandable sheath further includes a coating applied to the expandable frame and the material.

15. The apparatus according to claim 14, wherein the coating is a lubricious coating.

16. The apparatus according to claim 1, wherein the interlock is formed of stainless steel.

17. The apparatus according to claim 16, wherein the interlock is coated with a polymer.

18. The apparatus according to claim 1, wherein the interlock is formed of a polymer.

19. The apparatus according to claim 1, wherein the tapered tip is formed of a polymer.

20. The apparatus according to claim 18, wherein the tapered tip is formed of a polyether block amide.

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