Integrated expandable access for medical device introducers - Patent Application 20070122997

Abstract

To provide systems, devices and methods for insertion of a medical device (e.g., intravascular medical device).SOLUTION: An integrated sheath assembly 900 for inserting a medical device such as a percutaneous pump into a vessel can include a first sheath having a first lumen defining a first opening between proximal and distal ends of the first sheath for passage of a portion of the pump, and a second sheath having a second lumen defining a second opening between proximal and distal ends of the second sheath. The second lumen is expandable to allow passage of the first sheath containing the portion of the pump. The first sheath fills a space between the second sheath and the portion of the percutaneous pump when the first sheath containing the percutaneous pump is inserted into the second lumen. The first sheath has a first hub 410, and the second sheath has a second hub 210. A single sheath and a movable connector can be integrated on the medical device.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 558,507, filed September 14, 2017, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] background Medical devices, such as intracardiac heart pump assemblies, can be introduced into a patient's body in a variety of ways. Generally, a heart pump can be introduced into the heart to pump blood from the heart to the vasculature to support cardiac function. Once in the heart, the heart pump assembly draws blood from the left ventricle of the heart and ejects it into the aorta, or draws blood from the inferior vena cava (IVC), bypassing the right atrium and right ventricle, and ejecting it into the pulmonary artery. Heart pump assemblies can be introduced surgically or percutaneously through the vascular system during a cardiac procedure. In one common approach, the pump assembly is inserted through the femoral artery using a sheath, such as a peel-away introducer sheath, via a catheterization procedure. Alternatively, a sheath can be inserted into other locations, such as the femoral vein, or any route to deliver the pump for support of either the left or right heart.

[0003] A peel-away introducer sheath may be inserted into the femoral artery through an arteriotomy to create an insertion path for the pump assembly. A portion of the pump assembly is then advanced through the lumen of the introducer and into the artery. Once the pump assembly is inserted, the peel-away introducer sheath is peeled away. A repositioning sheath may then be advanced over the pump assembly and into the arteriotomy. Replacing the introducer sheath with a sheath that does not require peeling may prevent clot formation that might otherwise occur within the introducer sheath and, when used with a hemostatic valve, may improve fixation of the sheath to the patient, preventing or reducing bleeding at the skin and / or intravascular insertion site.

[0004] Because peel-away introducer sheaths are not radially stretchable, the inner diameter of the introducer sheath must always be large enough to accommodate the passage of the largest diameter cardiac pump inserted through the sheath, even if the diameter of other parts of the pump assembly, such as the catheter, is smaller. This means that once the pump is inserted, the peel-away introducer creates an opening with a larger outer diameter than necessary to allow passage of the pump catheter into the vasculature. Therefore, the peel-away introducer sheath is peeled away and replaced with a replacement sheath with a smaller cross-section. However, peel-away introducers have several disadvantages. For example, peel-away introducers can peel away too easily, risking premature tearing and leading to bleeding or vascular complications. On the other hand, peel-away introducers can also require excessive force to peel away. If the physician applies too much force, the physician may inadvertently shift the position of the pump within the heart when the introducer eventually breaks. Having to strip the introducer also complicates the design of the hemostatic valve located in the hub of the introducer, which must also be separated. Additionally, the stripping action is an additional step that the user must be aware of and trained on, and requires additional time to perform.

[0005] Some medical introducers for applications other than heart pump insertion have an expandable sheath body that can expand radially to allow percutaneous devices to be passed into a patient's vasculature. These introducers are inserted with an inner diameter smaller than the outer diameter of the device to be introduced. The introducer expands to allow the device to pass through the sheath into the vasculature and then retracts after the device has passed. Currently, these expandable introducers are intended for relatively short-term use and are stand-alone components. Because current expandable sheaths are intended for short-term use, they are not configured to prevent thrombosis between the sheath body and the indwelling catheter. Furthermore, current expandable sheaths do not include means for sealing the arteriotomy over the long term or for preventing migration (intravascular and extravascular) of the inserted device. Summary of the Invention

[0006] Systems, devices, and methods for inserting a medical device (e.g., an intravascular medical device) are presented. The device is delivered through an expandable introducer sheath. Use of an expandable introducer sheath allows for a smaller perforation size to be used for insertion, and may make it easier for the vessel to return to a smaller diameter after pump insertion. In addition, because the medical device only briefly passes through the vessel wall, the vessel opening is expected to be smaller than if a larger, non-expandable sheath were used. Furthermore, because the medical device also only briefly passes through the vessel, axial loads and stresses on the vessel are reduced if friction between the device, sheath, and vessel wall is minimized. That is, the sheath is smaller in size and does not push or pull the vessel along the axis of the insertion / removal path; instead, the vessel is stretched radially outward as the device passes through the vessel. The expandable introducer sheath of the present invention is configured to remain within the insertion path (e.g., arteriotomy) for a relatively long period of time (e.g., >1 hour, >2 hours, >6 hours, or any suitable period of time). To enable the introducer sheath to remain within the insertion path, the insertion sheath may be integrated with the percutaneous device being introduced or with a catheter associated with the percutaneous device. For example, the introducer sheath may connect to or interlock with a repositioning sheath of a mechanical assist device. In some embodiments, the expandable introducer sheath is included in a repositioning sheath assembly.

[0007] By allowing the introducer sheath to connect to the repositioning sheath and remain within the insertion path, disadvantages associated with peel-away introducers may be avoided. For example, because there is no need to remove the expandable introducer sheath, the risk of premature peeling is essentially eliminated and the risk of inadvertently shifting the introduced device (e.g., by using too much force during peeling) is reduced or eliminated. Furthermore, allowing the introducer sheath to remain within the insertion path simplifies use of the introduced device by reducing the number of steps in the insertion procedure, i.e., by eliminating the peeling process.

[0008] In a first aspect, a repositioning sheath assembly includes a first sheath having a first lumen defining a first opening between a proximal end and a distal end of the first sheath for passage of a portion of a medical device, the first sheath having a first hub coupled to its proximal end. The assembly further includes a second sheath having a second lumen defining a second opening between a proximal end and a distal end of the second sheath, the second lumen being expandable to allow passage of the first sheath containing the portion of the medical device, the second sheath having a second hub coupled to its proximal end. In this configuration, the first sheath fills the space between the second sheath and the portion of the medical device when the first sheath containing the portion of the medical device is inserted into the second lumen. Because the space between the second sheath and the portion of the medical device is occupied by the first sheath, there is little to no additional space in which blood can accumulate, which can cause thrombosis. Such an assembly may therefore reduce the risk of thrombus formation in the space between the first and second sheaths and in the space between the first sheath and the medical device. The assembly of the present invention is advantageous over conventional peel-away introducer sheaths in that it does not require separation or disassembly of the expandable second sheath to make way for the first sheath.

[0009] In certain embodiments, the sheath assembly includes a first port in fluid communication with the space between the first sheath and the portion of the medical device. In certain embodiments, the first port is located on the first hub. In certain embodiments, the sheath assembly includes a second port in fluid communication with the space between the second sheath and the first sheath when the first sheath is inserted into the second lumen. In certain embodiments, the second port is located on the second hub. In certain embodiments, the second hub includes an opening in fluid communication with the first lumen of the first sheath. In certain embodiments, the first sheath includes an additional lumen for passage of a guidewire, the additional lumen being parallel to the first lumen and extending from the proximal end to the distal end of the first sheath. In certain embodiments, the first hub includes a third port in communication with the additional lumen for passage of a guidewire.

[0010] In some embodiments, the first sheath is geometrically tapered from its proximal end to its distal end, with an outer diameter of the first sheath at its proximal end being larger than an outer diameter of the first sheath at its distal end. In certain embodiments, the first sheath comprises a expandable balloon for varying the diameter of the second lumen when the first sheath is inserted into the second lumen. In certain embodiments, the first hub comprises a balloon port connected to the expandable balloon.

[0011] In some embodiments, the first hub and the second hub are configured to couple to one another via at least one of a threaded connection, a press-fit connection, and a clip-lock connection. In certain embodiments, the first hub includes features configured for suturing to a patient. In certain embodiments, the first hub includes a pair of suturing wings, each wing having a plurality of ribs for securing sutures.

[0012] In certain embodiments, the first sheath body is sized to be introduced through a percutaneous access site of about 20 Fr (6.67 mm) or less. In certain embodiments, the second sheath comprises either a porous material or a mesh material. In certain embodiments, the outer surface of the first sheath comprises one of a radiopaque marker, a visible marker, and a marker for determining insertion depth. In certain embodiments, the outer surface of the first sheath is coated with one of an anti-thrombogenic coating and a coating that reduces the likelihood of clot formation between the first and second tubular sheaths. In certain embodiments, the outer surface of the first sheath is coated with one of a hydrophilic coating, a hydrophobic coating, and a coating that reduces friction. In certain embodiments, the outer surface of the first sheath is coated with one of an anti-microbial coating and a coating that reduces the likelihood of infection at the vascular opening.

[0013] In some embodiments, the first sheath and the second sheath are axially movable relative to each other's longitudinal axes. In certain embodiments, the sheath assembly includes a catheter, and both the first and second sheaths are slidably coupled to the catheter. In certain embodiments, the medical device is a percutaneous heart pump. In certain embodiments, the second sheath is expandable by blood pressure within the blood vessel to seal a space between the first sheath and the arteriotomy in the blood vessel.

[0014] In a further aspect, a repositioning sheath assembly includes a first rigid sheath having a first lumen defining a first opening between the proximal and distal ends of the first sheath for passage of a portion of a medical device. The assembly further includes a second sheath having a second lumen defining a second opening between the proximal and distal ends of the second sheath; the second lumen is expandable to allow passage of the first sheath containing the portion of the medical device; the second sheath has a second hub connected to its proximal end; and when the first sheath containing the portion of the medical device is inserted into the second lumen, the first sheath fills the space between the second sheath and the portion of the medical device. In this configuration, the sheath assembly facilitates delivery of the first and second sheaths and the portion of the medical device through a blood vessel, and the first sheath is configured to be peeled away once the medical device is positioned within the blood vessel.

[0015] In certain embodiments, the sheath assembly further includes a third sheath having a third lumen defining a third opening between a proximal end and a distal end of the third sheath for passage of the portion of the medical device, the third sheath having a third hub coupled to its proximal end, hi some embodiments, the third hub is configured to be in fluid communication with the second lumen when coupled to the second hub.

[0016] In yet another aspect, a repositioning sheath assembly includes a first hub fixedly connected to a medical device and a second sheath having a second lumen defining a second opening between a proximal end and a distal end of the second sheath. The second lumen is configured to be expandable to allow passage of a portion of the medical device, and the second sheath has a second hub coupled to its proximal end. The first hub is further configured to be in fluid communication with the second lumen when the first hub is coupled to the second hub. In certain embodiments, the first hub includes a first port that is in fluid communication with a space between the second sheath and the portion of the medical device when the first hub is coupled to the second hub. [The present invention 1001] 1. A sheath assembly for inserting a medical device into a blood vessel, comprising: a first sheath having a first lumen defining a first opening between a proximal end and a distal end of the first sheath for passage of a portion of the medical device, the first sheath having a first hub coupled to the proximal end; and a second sheath having a second lumen defining a second opening between a proximal end and a distal end of the second sheath, the second lumen being expandable to allow passage of the first sheath containing the portion of the medical device, the second sheath having a second hub coupled to its proximal end; Equipped with when the first sheath containing the portion of the medical device is inserted into the second lumen, the first sheath fills a space between the second sheath and the portion of the medical device; Sheath assembly. [The present invention 1002] The sheath assembly of the present invention 1001, comprising a first port in fluid communication with a space between the first sheath and the portion of the medical device. [The present invention 1003] The sheath assembly of the present invention 1002, wherein said first port is located on said first hub. [The present invention 1004] The sheath assembly of the present invention 1001, comprising a second port in fluid communication with the space between the second sheath and the first sheath when the first sheath is inserted into the second lumen. [The present invention 1005] The sheath assembly of the present invention 1004, wherein the second port is located on the second hub. [The present invention 1006] The sheath assembly of the present invention 1001, wherein the second hub has an opening in fluid communication with the first lumen of the first sheath. [The present invention 1007] 1001. A sheath assembly according to claim 10, wherein the first sheath comprises an additional lumen parallel to the first lumen and extending from the proximal end to the distal end of the first sheath for passage of a guidewire. [The present invention 1008] The sheath assembly of claim 1007, wherein said first hub comprises a third port communicating with said additional lumen for passage of said guidewire. [The present invention 1009] A sheath assembly of the present invention 1001, wherein the first sheath is geometrically tapered from its proximal end to its distal end, and the outer diameter of the first sheath at the proximal end is larger than the outer diameter of the first sheath at the distal end. [The present invention 1010] 1001. A sheath assembly according to claim 10, wherein the first sheath comprises an expandable balloon for varying the diameter of the second lumen when the first sheath is inserted into the second lumen. [The present invention 1011] The sheath assembly of the present invention 1010, wherein said first hub comprises a balloon port connected to said expandable balloon. [The present invention 1012] The sheath assembly of the present invention 1001, wherein the first hub and the second hub are configured to be coupled to each other by at least one of a threaded connection, a press-fit connection, and a clip-lock connection. [The present invention 1013] The sheath assembly of the present invention 1001, wherein the first hub includes features configured for suturing to a patient. [The present invention 1014] A sheath assembly according to claim 1013, wherein the first hub includes a pair of suture wings, each wing having a plurality of ribs for securing a suture thereto. [The present invention 1015] The sheath assembly of the present invention 1001, wherein the body of the first sheath is dimensioned to be introduced through a percutaneous access site of about 20 Fr (6.67 mm) or smaller. [The present invention 1016] The sheath assembly of the present invention 1001, wherein the second sheath comprises either a porous material or a mesh material. [The present invention 1017] The sheath assembly of the present invention 1001, wherein the outer surface of the first sheath comprises one of a radiopaque marker, a visible marker, and a marker for determining insertion depth. [The present invention 1018] A sheath assembly of the present invention 1001, wherein the outer surface of the first sheath is coated with one of an anti-thrombogenic coating and a coating that reduces the likelihood of blood clots forming between the first tubular sheath and the second tubular sheath. [The present invention 1019] The sheath assembly of the present invention 1001, wherein the outer surface of the first sheath is coated with one of a hydrophilic coating, a hydrophobic coating, and a friction-reducing coating. [The present invention 1020] The sheath assembly of the present invention 1001, wherein the outer surface of the first sheath is coated with one of an antibacterial coating and a coating that reduces the likelihood of infection occurring at the vascular opening. [The present invention 1021] The sheath assembly of the present invention 1001, wherein said first sheath and said second sheath are axially movable relative to each other's longitudinal axes. [The present invention 1022] The sheath assembly of claim 1021, wherein the sheath assembly further comprises a catheter, and both the first and second sheaths are slidably coupled to the catheter. [The present invention 1023] The sheath assembly of the present invention 1022, wherein the medical device is a percutaneous heart pump. [The present invention 1024] 1001. The sheath assembly of claim 10, wherein the second sheath is expandable by blood pressure in a blood vessel to seal a space between the first sheath and an arteriotomy in the blood vessel. [The present invention 1025] 1. A sheath assembly for inserting a medical device into a blood vessel, comprising: a first rigid sheath having a first lumen defining a first opening between a proximal end and a distal end of the first sheath for passage of a portion of the medical device; and a second sheath having a second lumen defining a second opening between a proximal end and a distal end of the second sheath, the second lumen being expandable to allow passage of the first sheath containing the portion of the medical device, the second sheath having a second hub coupled to its proximal end, the first sheath filling a space between the second sheath and the portion of the medical device when the first sheath containing the portion of the medical device is inserted within the second lumen; Equipped with the sheath assembly facilitates delivery of the first and second sheaths and the portion of the medical device through the blood vessel, and the first sheath is configured to be peeled away once the medical device is positioned within the blood vessel. Sheath assembly. [The present invention 1026] The sheath assembly of the present invention 1025 further comprising a third sheath having a third lumen defining a third opening between the proximal and distal ends of the third sheath for passage of the portion of the medical device, the third sheath having a third hub connected to its proximal end. [The present invention 1027] The sheath assembly of the present invention 1026, wherein the third hub is configured to be in fluid communication with the second lumen when coupled to the second hub. [The present invention 1028] 1. A sheath assembly for inserting a medical device into a blood vessel, comprising: a first hub fixedly connected to the medical device; and a second sheath having a second lumen defining a second opening between a proximal end and a distal end of the second sheath, the second lumen being expandable to allow passage of a portion of the medical device, the second sheath having a second hub coupled to its proximal end; Equipped with the first hub is configured to be in fluid communication with the second lumen when coupled to the second hub; Sheath assembly. [The present invention 1029] A sheath assembly according to claim 1028, wherein the first hub has a first port that is in fluid communication with the space between the second sheath and the portion of the medical device when the first hub is connected to the second hub. [Brief explanation of the drawings]

[0017] These and other objects and advantages will become apparent from the following detailed description considered in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout.

[0018] [Figure 1] 1 is a perspective view of an exemplary prior art medical device. [Figure 2] 1A and 1B are cross-sectional views of an exemplary prior art repositioning sheath for application to an opening (e.g., an arteriotomy) formed in a vessel. [Figure 3] 3 illustrates a cross-section of the exemplary repositioning sheath of FIG. 2 integrated with the medical device of FIG. 1. [Figure 4] 2A-2C illustrate cross sections of an exemplary expandable sheath for arterial access for a medical device such as the device of FIG. 1. [Figure 4A] 1A-1C illustrate cross sections of an exemplary expandable sheath comprising a sheet of compliant material rolled into a tubular configuration with overlapping ends. [Figure 5] 5A-5C illustrate an exemplary method for inserting a pump into an arteriotomy using the expandable sheath of FIG. 4. [Figure 6] 5 is a perspective view of the exemplary expandable sheath of FIG. 4 inserted into an insertion site using a vascular dilator. [Figure 7] 5 is a perspective view of the exemplary medical device of FIG. 1 inserted into the expandable sheath of FIG. 4. [Figure 8] 4A is a perspective view of the exemplary repositioning sheath of FIG. 3 inserted into the expandable sheath of FIG. 4 after the medical device of FIG. 1 has passed completely through the expandable sheath. [Figure 9] 2 is a diagram illustrating an exemplary expandable sheath assembly when the repositioning sheath of FIG. 2 is advanced toward the medical device of FIG. 1 and the hub on the proximal end of the repositioning sheath is coupled with the hub on the proximal end of the expandable sheath. [Figure 10] 5 is a perspective view of the exemplary expandable sheath of FIG. 4 inserted through an arteriotomy into a blood vessel. [Figure 11] 10A-10C illustrate an embodiment of an exemplary alternative configuration of an expandable sheath assembly for insertion into a blood vessel through an arteriotomy, in which the repositioning sheath of FIG. 3 includes a hub. [Figure 12] 5A-5C illustrate an embodiment of an exemplary alternative configuration of an expandable sheath assembly inserted into a blood vessel through an arteriotomy, in which the expandable sheath of FIG. 4 is inserted together with a rigid peel-away sheath. DETAILED DESCRIPTION OF THE INVENTION

[0019] Detailed Description Certain exemplary embodiments will be described so that the systems, methods, and devices described herein can be fully understood. While the embodiments and features described herein are specifically described for use in connection with a percutaneous cardiac pump system, it will be understood that all components and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to other types of medical devices, such as cardiac therapy devices and cardiac assist devices, including balloon pumps and cardiac assist devices implanted using a surgical incision.

[0020] The systems, methods, and devices described herein provide a sheath assembly for inserting a medical device (e.g., a percutaneous heart pump) into a blood vessel through a vascular opening. The sheath assembly includes a first sheath having a first lumen defining a first open passage between a proximal end and a distal end of the first sheath, allowing a portion of the medical device to pass through the first sheath. The first sheath has a first hub coupled to its proximal end for attachment to other components of the integrated sheath assembly. The sheath assembly also includes a second sheath having a second lumen defining a second open passage between a proximal end and a distal end of the second sheath, allowing the medical device and the first sheath to pass through a second lumen of the second sheath. The second sheath has a second hub coupled to its proximal end for mating with other components of the integrated sheath assembly, such as the first hub of the first sheath. Such mating of the hubs ensures fluid communication between the first lumen and the second lumen. The second lumen is constructed from an expandable material to allow the percutaneous pump and first sheath to pass smoothly through. In this manner, the space between the first and second sheaths and the space between the body of the percutaneous medical device and the second sheath are minimized. This reduces blood accumulation between (i) the first and second sheaths and (ii) the second sheath and the body of the percutaneous medical device, thus preventing or reducing thrombosis in these spaces. To prevent blood leakage between the sheath and the catheter, the connection between the expandable sheath and the repositioning sheath may be hemostatic and designed with sealing features such as an O-ring or interference fit.

[0021] Additionally, when the first sheath is inserted into the second lumen, the first sheath fills the space between the second sheath and the medical device, such as a percutaneous pump. This prevents or reduces blood accumulation between the second sheath and the percutaneous pump, further minimizing the risk of thrombosis. Once the hubs are connected, fluid may be passed through the integrated extendable sheath assembly to continuously flush blood from the space between the extendable sheath and the integrated sheath body.

[0022] FIG. 1 illustrates an exemplary mechanical assist device (MAD), such as a percutaneous pump 100, according to certain embodiments. The pump 100 includes a pump handle 110, a pump head 130, and a pump body 120 that connects the pump handle 110 to the pump head 130. The pump body 120 is tubular and has a substantially uniform outer diameter. The pump body 120 provides electromechanical communication between the pump head 130 and the pump handle 110. The pump handle 110 communicates with control circuitry that enables control of the pump head 130. The pump head 130 contains electromechanical components that enable the device to perform various tasks within a patient's body, such as pumping blood from a location within the body. The pump head 130 has a diameter 140 that is larger than the diameter 150 of the pump body 120. One example of such a percutaneous pump is the Impella 2.5™ system (Abiomed, Inc., Danvers, Massachusetts). It will be understood that although a percutaneous heart pump is described herein, any other percutaneous medical device may be used in connection with the present disclosure.

[0023] FIG. 2 illustrates an exemplary repositioning sheath 200 according to certain embodiments. The repositioning sheath 200 includes a sheath body 220 having a central longitudinal axis 201, a proximal portion 202, and a distal portion 204. The sheath body 220 has a substantially uniform cross-section and is sized for insertion into a blood vessel through a vascular opening. In certain embodiments, the sheath body 220 may be tubular with a circular or oval cross-section and may have a constant or varying wall thickness. In some embodiments, the sheath body 220 is sized for insertion into a femoral artery through an arteriotomy. Most sheath bodies 220 may have a substantially uniform outer diameter of approximately 10 Fr, 11 Fr, 12 Fr, 13 Fr, 14 Fr, 15 Fr, 16 Fr, 17 Fr, 20 Fr, or any other suitable diameter. The sheath body 220 may be sized to be introduced through a percutaneous access site of about 20 Fr (6.67 mm) or smaller (e.g., 19 Fr, 18 Fr, 17 Fr, 16 Fr, 15 Fr, 14 Fr, 13 Fr, 12 Fr, 10 Fr, 9 Fr, 8 Fr, 6 Fr, or smaller). The sheath body 220 may have a length of about 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, or any other suitable length. In some embodiments, the sheath body 220 may be tapered.

[0024] The sheath body 220 has a first lumen 230 that extends along the length of the sheath body 220 from the proximal portion 202 to the distal portion 204 and is substantially parallel to the longitudinal axis 201. The first lumen 230 is defined by an inner surface 222 of a wall 224 of the sheath body 220. The sheath body 220 has a diameter 208, and the first lumen 230 has a diameter 226. The distal portion 204 of the sheath body 220 includes a tapered surface 260 and a first opening 270 in fluid communication with the first lumen 230. The tapered surface 260 has an outer diameter that varies from 11 Fr to 15 Fr (3.667 mm to 5 mm). The varying outer diameter of the tapered surface 260 potentially allows the repositioning sheath 200 to be inserted to various insertion depths as needed to adequately close the gap between the percutaneous pump and the insertion site. The tapered surface 260 of the repositioning sheath 200 may allow the user to better seal the arteriotomy at various diameters (controlled by the length of the tapered surface 260 advanced into the arteriotomy). The user may advance the tapered surface 260 of the repositioning sheath 200 until oozing / bleeding stops. Arteriotomy sizes vary from patient to patient depending on, for example, calcification, scar tissue, vessel size, and elasticity. The tapered surface 260 of the repositioning sheath 200 allows for custom arteriotomy sealing as needed. The first lumen 230 is sized to allow a portion of the percutaneous pump 100 of FIG. 1 to pass therethrough, with the diameter 226 of the first lumen 230 being larger than the diameter 150 of the pump body 120. Additionally, the diameter 226 of the first lumen 230 is smaller than the diameter 140 of the pump head 130. Hub 210 is located at proximal portion 202 of repositioning sheath 200 and has a passageway 212 in fluid communication with first lumen 230. Passageway 212 is configured with a valve 216, such as a hemostatic valve as described in U.S. patent application Ser. No. 15 / 245,982, entitled "Hemostatic Valve for Medical Device Introducer," the entire contents of which are incorporated herein by reference. Passageway 212 and valve 216 allow at least a portion of a mechanical assist device, such as percutaneous pump 100 of FIG. 1, to pass through repositioning sheath 200.The sheath body 220 may be made of a flexible material, such as polyether block amide or any other suitable polymer, to reduce stress on the vascular opening. The material may be selected to meet the stiffness requirements for a particular medical procedure.

[0025] The outer surface 206 of the sheath body 220 may be coated with a hydrophilic coating or any other suitable coating to reduce frictional forces during insertion and removal of the repositioning sheath 200 into and from the vasculature. Only the distal portion of the sheath body 220 may be coated, or the coating may completely cover the outer surface 206 of the sheath body 220. The hydrophilic coating may also prevent adhesion to the vessel wall, which could damage the vessel if the sheath is removed after remaining within the vessel for an extended period of time (e.g., days). The risk of adhesion to the vessel wall may increase with increasing procedure duration. In some embodiments, the outer surface 206 of the wall 224 of the repositioning sheath body 220 includes an antimicrobial coating or any other suitable coating to prevent or reduce the risk of infection. Additionally, in some embodiments, the inner surface 222 of the first lumen 270 and the inner surface of the second lumen 280 include an antimicrobial coating or any other suitable coating to prevent or reduce the risk of infection. In further embodiments, the outer surface 206 of the sheath body 220 includes depth markings. The depth markings may be pad printed or laser etched onto the outer surface 206. In certain embodiments, the depth markings are radiopaque. The units of the depth markings may be centimeters, inches, millimeters, or any other suitable unit of measure, or a combination thereof.

[0026] In certain embodiments, the sheath body 220 may have a second lumen 250, such as the second lumen in the dual lumen sheath described in U.S. patent application Ser. No. 14 / 827,741, entitled "Dual Lumen Sheath for Arterial Access," the entire contents of which are incorporated herein by reference. The second lumen 250 extends along the length of the sheath body 220 from the proximal portion 202 to the distal portion 204. The second lumen 250 is located within the wall 224 of the sheath body 220 and is offset from and substantially parallel to the longitudinal axis 201. The second lumen 250 has an opening 280 on the tapered surface 260 of the distal portion 204 of the sheath body 220. The opening 280 is in fluid communication with the second lumen 250. In certain embodiments, the hub 210 has a first port 240 in fluid communication with the second lumen 250. The first port 240 is fitted with a valve (not shown).

[0027] Additionally, in certain embodiments, the repositioning sheath 200 may have an inflatable balloon attached to the outer surface 206 of the sheath body 220. The inflatable balloon may be in fluid communication with a second port located on the hub 210. The inflatable balloon may be in a collapsed state during insertion of the repositioning sheath 200. The balloon may be inflated with a fluid, such as saline, or air through the second port on the hub 210 to fix the position of the sheath at a specific insertion depth within the arteriotomy. The balloon may be formed from a flexible material, such as polyurethane or Teflon material, that can be inflated to a specific pressure corresponding to a specific outer diameter. In certain aspects, the first port located on the hub is the balloon port.

[0028] 3, the percutaneous pump 100 and the repositioning sheath 200 may be integrated to form a repositioning sheath assembly 300. The repositioning sheath 200 is secured onto the body 120 of the percutaneous pump 100 such that the pump body 120 is disposed within the first lumen 230. Because the diameter 226 of the first lumen 230 is smaller than the diameter 140 of the pump head 130, this allows the percutaneous pump 100 and the repositioning sheath 200 to be integrated during manufacturing such that the pump head 130 is located outside the first opening 270 and prevents the percutaneous pump 100 from becoming free of the repositioning sheath 200 prior to use. In this configuration, the pump 100 can move laterally (in the direction indicated by arrow A in FIG. 3) relative to the repositioning sheath 200, allowing the percutaneous pump 100 to be advanced into the blood vessel when the tapered surface 260 of the distal end 204 of the repositioning sheath 200 is inserted into an arteriotomy in the patient's femoral artery.

[0029] FIG. 4 illustrates an expandable sheath 400 according to certain embodiments. The expandable sheath 400 comprises an expandable body 420 having a proximal portion 402, a distal portion 404, and a lumen 430. The lumen 430 is open and connects the proximal portion 402 to the distal portion 404. A hub 410 is attached to the proximal portion 402 of the expandable body 420. The hub 410 has an opening 450 in fluid communication with the lumen 430. The opening 450 is configured with a valve 455, such as a hemostatic valve as described in U.S. patent application Ser. No. 15 / 245,982, the entire contents of which are incorporated herein by reference. The opening 450 has a diameter 405 designed to be larger than the diameter 208 of the sheath body 220 to allow the repositioning sheath assembly 300 to pass through the lumen 430. In some embodiments, the expandable body 420 may be tubular.

[0030] The expandable body 420 has a non-extended diameter 425. The expandable body 420 may be expanded by an object inserted into the lumen 430. The expandable body 420 may be made from an expandable material that has some degree of compliance. For example, a compliant material such as polyester or polytetrafluoroethylene (PTFE) may be used. In certain embodiments, the expandable material may be a mesh made from a compliant material. In alternative embodiments, the expandable sheath body 420 may comprise a porous material. In some embodiments, the expandable sheath body 420 may comprise a sheet of compliant material rolled into a tubular configuration with overlapping ends, as shown in FIG. 4A. In some embodiments, the non-extended diameter 425 of the expandable body 420 may be larger than the diameter 150 of the pump body 120. The non-extended diameter 425 of the expandable body 420 may be increased to accommodate the pump head 130 when the percutaneous pump 100 is inserted into the expandable sheath 400. The repositioning sheath 200 and the expandable sheath 400 form an expandable access assembly for advancing a percutaneous device such as the pump 100.

[0031] In some embodiments, the expandable sheath 400 may have an inflatable balloon attached to the sheath body 420. The balloon may be inflated with a fluid, such as saline, or air through a balloon port (not shown) on the hub 410. The balloon may be formed from a flexible material, such as polyurethane or Teflon material, that can be inflated to a specific pressure corresponding to a specific outer diameter. In certain aspects, the flushing port 440 located on the hub 410 is the balloon port.

[0032] In certain embodiments, the hub 410 has a flushing port 440 connected to a passageway 442. The flushing port 440 is fitted with a valve (not shown). The passageway 442 is in fluid communication with the lumen 430. The flushing port 440 therefore allows for the space between the extendable body 420 and the sheath body 220 to be flushed with fluid when the integrated repositioning sheath 300 is inserted within the extendable sheath 400. A pressurized bag may be connected to the flushing port 440 using any type of engagement mechanism (e.g., threads, clip lock, etc.). The pressurized bag may be used to flush the space between the extendable body 420 and the sheath body 220 with fluid to maintain patency of the space and thereby prevent the formation of blood clots. Such flushing may be instantaneous or continuous. An infusion pump may be used in combination with the pressurized bag to regulate the flow of fluid into the patient's body. For example, the flow rate may be limited to 1 mL / hr, 2 mL / hr, 5 mL / hr, 10 mL / hr, or any other suitable flow rate. The port may also be used to obtain blood pressure measurements if desired. Alternatively, any hub herein may not include a flushing port.

[0033] FIGURE 5 illustrates a method 500 for using an expandable access assembly. In step S510, an expandable sheath (e.g., expandable sheath 400 of FIGURE 4) is inserted into a patient through an insertion site (e.g., insertion site 650 of FIGURE 6) with the aid of a vascular dilator (e.g., vascular dilator 600 of FIGURE 600). Such an insertion site is created during surgery and may comprise, for example, a keyhole incision.

[0034] In step S520, a pump head (e.g., pump head 130) and a portion of a pump body (e.g., a portion of pump body 120) are threaded through an opening in the hub of the expandable sheath (e.g., opening 450 in hub 410). As the pump head advances through the lumen of the expandable sheath (e.g., lumen 430 of expandable sheath 400), it increases the diameter of the expandable body (e.g., expandable body 420). Due to its compliant nature, the expandable body conforms to the shape of the pump head as it is advanced through the lumen of the expandable sheath. Additionally, blood pressure within the patient may exert a compressive force on the expandable body, which may help the expandable body conform to the shape of the pump head. The pump head is advanced until it emerges from the distal end of the expandable body (e.g., from the distal end 404 of expandable body 420, as shown in FIG. 8 ). When the pump head exits the extensible body, the lumen of the extensible body returns substantially to its unextended diameter.

[0035] In step S530, after the percutaneous pump is advanced past the distal portion of the expandable body, a repositioning sheath (e.g., repositioning sheath 200) is advanced into the patient's vasculature, where the repositioning sheath is threaded along the body of the percutaneous pump with the distal portion inserted into an opening (e.g., opening 450) in the hub of the expandable sheath. A medical professional may use hub 210 of repositioning sheath 200 to advance the repositioning sheath into expandable sheath 400.

[0036] In step S540, the repositioning sheath hub (e.g., hub 210) is coupled to the expandable sheath hub (e.g., hub 410). Such coupling may be achieved using any type of engagement mechanism, such as a threaded connection, a press-fit connection, or a clip-lock connection. As illustrated in FIG. 9 , the expandable sheath hub 410 has an internal fit with the repositioning sheath hub 210; that is, when the hubs are coupled, the expandable sheath hub 410 fits within the repositioning sheath hub 210. In other embodiments (not shown), the repositioning sheath hub 210 has an internal fit with the expandable sheath hub 410; that is, when the hubs are coupled, the repositioning sheath hub 210 fits within the expandable sheath hub 410. Once coupled, the first lumen 230 of the repositioning sheath 200 may be in fluid communication with the lumen 430 of the expandable sheath 400.

[0037] In step S550, a distal portion of the repositioning sheath (e.g., distal portion 204) is advanced from within the lumen of the expandable sheath (e.g., lumen 430) into the arteriotomy. A transition in the tapered surface (e.g., tapered surface 260) is inserted to a desired depth, if necessary, to close the arteriotomy in the blood vessel (e.g., arteriotomy 1020 in FIG. 10). This seals the gap between the percutaneous pump and the arteriotomy and prevents blood from flowing out of the arteriotomy.

[0038] 5 thus ensures that the repositioning sheath fills the space between the expandable sheath and the percutaneous pump when the repositioning sheath is inserted into the lumen of the expandable sheath, which prevents or reduces blood accumulation between the second sheath and the percutaneous pump, thereby minimizing the risk of thrombus formation.

[0039] FIG. 6 shows a perspective view of the insertion of the exemplary expandable sheath 400 of FIG. 4 into an insertion site using a vascular dilator 600. The dilator 600 has a diameter smaller than the diameter 405 of the opening 450 in the proximal portion 402 of the expandable sheath 400. Prior to insertion into the insertion site 650, the dilator 600 is inserted into the expandable sheath through the opening 450 and advanced through the lumen 430 from the proximal portion 402 to the distal portion 404 of the expandable body 420. As the dilator 600 is inserted into the lumen 430 of the expandable sheath 400, the diameter 425 of the expandable body 420 increases so that the expandable sheath 400 conforms to the shape of the dilator 600. As shown in FIG. 6, the dilator 600 is fully inserted into the expandable sheath 400.

[0040] The outer surface of the dilator 600 may be coated with a hydrophilic coating or any other suitable coating to reduce frictional forces during insertion and removal of the dilator 600 from the expandable sheath 400. The outer surface of the dilator 600 may also be coated with a lubricating gel to facilitate insertion into the expandable sheath 400 and the insertion site 650. Once the dilator 600 is fully inserted into the expandable sheath 400, as shown in FIG. 6, the arrangement is inserted into the insertion site 650, as shown in FIG. 7. Once the body 420 of the expandable sheath 400 is inserted into the insertion site 650, the dilator 600 is removed from the expandable sheath 400. At this point, the expandable body 420 substantially returns to a non-expanded state within the patient's vasculature.

[0041] FIG. 7 shows a perspective view of the exemplary percutaneous medical device of FIG. 1 inserted within the expandable sheath of FIG. In the illustrated position, the hub 410 of the expandable sheath 400 remains outside the patient's body, while the expandable body 420 is within the patient's body. Figure 7 also shows that the integrated repositioning sheath 300 (not visible in this view) is advanced through the expandable sheath 400 and into the patient's vasculature. As previously described, the integrated repositioning sheath 300 comprises a repositioning sheath 200 secured onto the pump body 120 of the percutaneous pump 100. As shown in Figure 7, the pump head 130 increases the diameter of the expandable body 420 as it advances through the lumen 430 of the expandable sheath 400. Due to its compliant nature, the body 420 conforms to the shape of the pump head 130 as it is advanced through the lumen 430. Additionally, the pressure of the blood 750 within the patient may exert a compressive force on the extensible body 420, which may help the extensible body 420 conform to the shape of the pump head 130. The pump head 130 is advanced until it exits the distal portion 404 of the extensible body 420, as shown in FIG.

[0042] FIG. 8 shows a perspective view of insertion in which the exemplary repositioning sheath of FIG. 3 is inserted into the expandable sheath of FIG. 4 after the percutaneous medical device of FIG. 1 has passed completely through the expandable sheath of FIG. 4. FIG. 8 shows that the lumen 430 of the expandable body 420 has substantially returned to its unextended diameter 425 when the pump head 130 exits the expandable body 420. After the percutaneous pump 100 is advanced past the distal end portion 404 of the expandable body 420, the repositioning sheath 200 is advanced into the patient's vasculature. The repositioning sheath 200 is threaded along the body 120 of the percutaneous pump 100 with the distal end portion 204 inserted into the opening 540 of the hub 410 of the expandable sheath 400. The hub 210 of the repositioning sheath 200 may be used to advance the repositioning sheath into the expandable sheath 400.

[0043] FIG. 9 shows an exemplary expandable sheath assembly when the repositioning sheath of FIG. 2 is advanced toward the percutaneous medical device of FIG. 1 and the hub on the proximal end of the repositioning sheath is coupled with the hub on the proximal end of the expandable sheath.

[0044] 9 shows the expandable access assembly 900 after the repositioning sheath 200 has been fully inserted into the expandable sheath 400. The hub 410 of the expandable sheath 400 and the hub 210 of the repositioning sheath 200 are coupled together. Such a coupling may be achieved using any type of engagement mechanism, such as a threaded connection, a press-fit connection, or a clip-lock connection. In some embodiments, the coupling between the expandable sheath and the repositioning sheath may be hemostatic and designed with sealing features, such as an O-ring or interference fit, to prevent blood leakage between the sheath and the catheter. Once coupled, the first lumen 230 of the repositioning sheath 200 is in fluid communication with the lumen 430 of the expandable sheath 400.

[0045] The expandable access assembly 900 has advantages over conventional peel-away introducer sheaths in that it is not necessary to separate or disassemble the expandable sheath 400 to make way for the repositioning sheath 200. Such separation requires force, which can inadvertently displace the percutaneous pump 100. Additionally, the integrated expandable sheath assembly of the present disclosure can be secured in place on the patient's skin and can be reused when the percutaneous pump needs to be repositioned.

[0046] FIG. 10 shows a perspective view of the exemplary expandable sheath 400 of FIG. 4 inserted through an arteriotomy into a blood vessel. Once the hub 210 of the repositioning sheath 200 and the hub 410 of the expandable sheath 400 are coupled, the distal portion 204 of the repositioning sheath 200 is advanced through the lumen 430 of the expandable sheath 400 and into the arteriotomy. To close the arteriotomy 1020 in the blood vessel 1050, the gradual change in the tapered surface 260 may be inserted to a desired depth, if necessary. This seals the gap between the percutaneous pump 100 and the arteriotomy 1020 and prevents blood from flowing out of the arteriotomy. Once the expandable access assembly 900 is in place, the percutaneous pump 100 (not shown) can be repositioned within the blood vessel as needed without having to move the assembly 900. This can be accomplished by simply sliding the pump body 120 proximally and / or distally along the first lumen 230 of the repositioning sheath 200 while the assembly 900 is fixed in place relative to the patient's body.

[0047] Once the assembly 900 is in place, the hub 210 of the repositioning sheath 200 may be anchored to the patient. As previously mentioned, the hub 210 may include features for attaching sutures, such as wings (e.g., feature 950 in FIG. 9 ) and suture holes (not shown). The suture holes allow the wings to be sutured to the patient to stabilize the assembly 900. Any suitable number of suture holes may be used. The hub 210 is also designed to be easily attached to a vascular graft with umbilical tape or sutures. This is beneficial during axillary insertion or any other insertion requiring placement of a pump through a vascular graft. In certain embodiments, other stabilizing devices may be coupled to the hub 210, such as surgical tape, a STATLOCK® stabilizing device (Bard Access Systems, Inc., Salt Lake City, UT), or any other suitable adhesive stabilizing device.

[0048] It should be noted that the geometry of the arteriotomy 1020 may be such that a fluid-tight seal is not formed, potentially leading to blood seepage from the blood vessel 1050 to the exterior of the arteriotomy 1020. Such a geometry may be non-uniform, such as a non-circular opening in the blood vessel. This may lead to undesirable blood emboli and clot formation. In accordance with the present disclosure, the expandable body 220 of the sheath 200 is expandable as needed by internal blood pressure and thus can conform to the non-circular arteriotomy, thereby preventing blood seepage. In certain embodiments in which the repositioning sheath 200 has an inflatable balloon attached to the exterior surface 206 of the sheath body 220 (as described above), the balloon may be inflated to anchor the assembly 200. Additionally, the inflated balloon may further inhibit blood seepage from irregular arteriotomy by adjusting the diameter of the expandable sheath as needed.

[0049] To further prevent clot formation within the expandable access assembly 900, ports 440 on the hub 410 allow for connection of a pressurized bag to flush the assembly 900 with fluid to maintain patency of the system. As previously described, the pressurized bag may be connected to these ports using any type of engagement mechanism (e.g., threads, press-fit, clip lock, etc.). An infusion pump may be used in combination with the pressurized bag to regulate the flow rate of fluid into the patient. For example, the flow rate may be limited to 1 mL / hr, 2 mL / hr, 5 mL / hr, 10 mL / hr, or any other suitable rate. Specifically, the space between the expandable sheath 400 and the repositioning sheath 200 may be flushed with fluid introduced into the assembly via port 440. Such flushing may be instantaneous or continuous. Flushing these spaces with fluid also flushes out any clots in the insertion path of the percutaneous pump 100. The port may also be used to obtain blood pressure measurements, if desired. Alternatively, the hub may not include this port.

[0050] In certain embodiments, the repositioning sheath 200 may include only the second hub 210, which is fixedly attached to the pump body 120. In such a configuration, when the percutaneous pump 100 is inserted into the expandable sheath 400, the expandable body 420 collapses completely onto the pump body 120. The fixed second hub 210 allows the pump 100 to be manipulated within the patient's vasculature for intravascular placement. The second hub 210 is then coupled to the hub 410 of the expandable sheath 400 so that the hubs are in fluid communication with each other, and more specifically, so that the second hub 210 is in fluid communication with the lumen 430 of the expandable sheath 400, as shown in FIG. 11 . In some embodiments, the second hub 210 includes a port or side arm that is in fluid communication with the space between the expandable body 420 and the portion of the percutaneous pump 100 when the hub 410 is coupled to the second hub 210. Such a port may be used to flush with fluid the space between the expandable body 420 and said portion of the transdermal pump 100. Alternatively, the port may be used to measure blood pressure.

[0051] In other embodiments, an expandable sheath 400 is not required. Instead, the body 220 of the repositioning sheath 200 may be expandable. This allows the user to tailor the diameter of the sheath body 220 to fill the gap between the arteriotomy and the percutaneous pump 100.

[0052] 12, the expandable access assembly 1200 additionally includes a removable component, such as a peel-away sheath 1210. In such a configuration, the peel-away sheath 1210 is a rigid sheath that can be torn or peeled away, where the rigid sheath 1210 acts as a stiffening structure for delivery within the vessel while positioned within the expandable sheath 400. The rigid sheath 1210 is then peeled away without disturbing the position of the medical device 100 relative to the patient. Once the rigid sheath 1210 is peeled away, the repositioning sheath 200 may then be advanced along the body 120 of the medical device 100 to fill the opening in the vessel.

[0053] Additionally, guidewire access through the second lumen 250 of the repositioning sheath 200 is also possible when the assembly 900 is in place within the patient's vasculature.

[0054] In light of the above, it will be apparent that the present disclosure provides a means for securing a mechanical assist device in place within an integrated expandable sheath that is tethered to the patient, thereby preventing migration of the device once inserted into the heart.

[0055] The foregoing is merely illustrative of the principles of the present disclosure, and the systems, methods, and devices of the present invention may be practiced in other ways than those described herein; the embodiments described herein are presented for purposes of illustration and not limitation. It should be understood that the systems, methods, and devices disclosed herein, while shown for use in a system for a percutaneous heart pump, may also be applied to systems, methods, and devices for other implantable heart pumps or implantable cardiac assist devices.

[0056] Variations and modifications will occur to those skilled in the art after reviewing this disclosure. The various features described or illustrated above, including any components thereof, may be combined or integrated into other systems. Additionally, certain features may be omitted or not implemented. The various embodiments described or illustrated above may be combined in any manner.

[0057] Examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope of the information disclosed herein. All references cited herein are incorporated by reference in their entirety and made a part of this application.

Claims

1. 1. A sheath assembly comprising: a medical device configured to be inserted into a blood vessel, wherein a first portion of the medical device has a first width and a second portion of the medical device has a second width that is smaller than the first width, the second portion of the medical device being proximal to the first portion of the medical device; a first sheath configured to allow passage of the second portion of the medical device, the first sheath having a first lumen extending between a proximal end and a distal end of the first sheath and tapering from the proximal end to the distal end; a first hub coupled to the proximal end of the first sheath; a second sheath sized to be inserted into the femoral artery through the arteriotomy, the second sheath having a second lumen extending between a proximal end and a distal end of the second sheath, the second lumen having a first inner diameter at rest and configured to be resiliently expandable from the first inner diameter to a second inner diameter; and a second hub coupled to the proximal end of the second sheath; Equipped with the second lumen is configured to expand to a second inner diameter during the passage of the first portion of the medical device and to resiliently contract from the second inner diameter during the passage of the second portion of the medical device; and a sheath assembly wherein the second sheath is inserted into the blood vessel through the arteriotomy and the tapered first sheath is inserted into the second sheath to an insertion depth required to seal the arteriotomy corresponding to a diameter of the arteriotomy, such that when the second sheath is inserted into the second lumen over the second portion of the medical device, the tapered first sheath forms a seal between the inner surface of the second sheath and the second portion of the medical device and substantially prevents blood from the blood vessel from migrating past the seal.

2. 10. The sheath assembly of claim 1, further comprising a port configured to allow fluid delivery between an inner surface of the first sheath and the outer surface of the second portion of the medical device when the second portion of the medical device is housed within the first lumen.

3. The sheath assembly of claim 2 , wherein the port is located on the first hub.

4. 10. The sheath assembly of claim 1, further comprising a port configured to allow delivery of a fluid between the inner surface of the second sheath and the outer surface of the first sheath when the first sheath is inserted into the second lumen.

5. The sheath assembly of claim 4 , wherein the port is located on the second hub.

6. 10. The sheath assembly of claim 1, wherein the first hub further comprises a port configured to allow delivery of a fluid into the second lumen of the second sheath when the first sheath is inserted into the second lumen.

7. 10. The sheath assembly of claim 1, wherein the first sheath further comprises an auxiliary lumen configured to allow passage of a guidewire, the auxiliary lumen being substantially parallel to the first lumen and extending from the proximal end to the distal end of the first sheath.

8. The sheath assembly of claim 1 , wherein the first sheath further comprises an expandable balloon configured to allow variation in the diameter of the second lumen when the first sheath is inserted within the second lumen.

9. The sheath assembly of claim 1 , wherein the first hub and the second hub are configured to couple to one another by at least one of a threaded connection, a press-fit connection, or a clip-lock connection.

10. The sheath assembly of claim 1, wherein the outer diameter of the second sheath is sized for introduction through a percutaneous access site of 20 Fr (6.67 mm) or smaller.

11. The sheath assembly of claim 1 , wherein the second sheath comprises either a porous material or a mesh material.

12. The sheath assembly of claim 1 , wherein the second sheath comprises a sheet rolled into a tubular configuration with overlapping ends when the second lumen is at the first inner diameter.

13. The sheath assembly of claim 1 , wherein an outer surface of the first sheath comprises one of a radiopaque marker, a visible marker, or a marker for determining insertion depth.

14. 10. The sheath assembly of claim 1, wherein an outer surface of the first sheath is coated with one of an anti-thrombogenic coating or a coating configured to reduce the likelihood of blood clot formation between the first sheath and the second sheath upon insertion into the blood vessel.

15. The sheath assembly of claim 1 , wherein the outer surface of the second sheath is coated with one of a hydrophilic coating, a hydrophobic coating, or a friction-reducing coating.

16. 10. The sheath assembly of claim 1, wherein an outer surface of the second sheath is coated with one of an antimicrobial coating or a coating configured to reduce the likelihood of infection occurring within a blood vessel when the second sheath is inserted into the blood vessel.

17. 2. The sheath assembly of claim 1, wherein the first sheath is configured to be inserted into the second sheath by axially moving the first sheath and the second sheath relative to one another along a longitudinal axis of the first sheath and the second sheath.

18. The sheath assembly of claim 17 , wherein both the first sheath and the second sheath are configured to be slidably coupled to the second portion of the medical device.

19. The sheath assembly of claim 18 , wherein the medical device is a percutaneous heart pump.

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