Negative pressure stent delivery system and related method

Abstract

To provide a stent delivery system and method for removing thrombus from a blood vascular system of a patient.SOLUTION: A first guide tube can be advanced through a blood vascular system of a patient. A frame configured to energize a covered stent to an expanded state when the covered stent is in a compressed state. The covered stent that can be expanded in a radial direction from a compressed state to the expanded state can be advanced through the first guide tube in a state that the inside of a lumen of the covered stent is decompressed. After the covered stent is advanced through the first guide tube, at least the covered stent is positioned with respect to the first guide tube so that at least a part of the covered stent is arranged at a distal position of a distal end of the first guide tube, and the pressure in the lumen of the covered stent is increased so that the covered stent can be expanded to the expanded state from the compressed state.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates generally to a stent delivery system and method for removing thrombus from a patient's vasculature. (CROSS-REFERENCE TO RELATED APPLICATIONS) This application is a non-provisional application claiming priority to U.S. Provisional Patent Application No. 63 / 627,915, filed February 1, 2024, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Blood clots (also called blood clots) can block blood flow through blood vessels, thereby depriving tissues of blood and oxygen and causing tissue damage. Blood clots are the leading cause of stroke and require prompt treatment to reduce the risk of long-term disability or death.

[0003] Thrombectomy is a common procedure for treating stroke. During thrombectomy, a guide catheter is inserted into the patient's vascular system through the groin and advanced toward the clot. A stent retriever can then be threaded through the guide catheter to entangle and capture the clot. Once the clot is captured, the stent retriever and catheter can be removed, restoring blood flow to the brain. Alternatively, a small-bore aspiration catheter can be threaded through the guide catheter, and when the distal end of the catheter reaches the clot, negative pressure can be applied at the proximal end of the catheter to attract the clot toward the aspiration catheter's port and remove it. Over the past decade, thrombectomy has improved the success rate of stroke treatment, achieving recanalization in approximately 85% of procedures.

[0004] However, the inventors have recognized a number of challenges that have hindered successful recanalization in all thrombectomy procedures, or at least made successful thrombectomy procedures more difficult. Some thrombectomy procedures utilize stent expansion within the vasculature to remove thrombi. For example, a stent retriever may require radial expansion to mechanically engage and properly capture the thrombus. Additionally, an expandable covered stent may be beneficial when thrombectomy relies on aspiration of the thrombus. This is because, in stroke cases, aspiration catheters must be able to access the vasculature containing the thrombus (typically the internal carotid artery or middle cerebral artery (e.g., its M1 portion)). Therefore, aspiration catheters are typically relatively thin, with a diameter less than 50% of the vessel diameter. Such thin aspiration catheters may not be able to retract the stroke-inducing thrombus that has spread through the vessel. As a result, thrombectomy using thin aspiration catheters is often performed by retracting the aspiration catheter with the majority of the thrombus outside the lumen, rather than using a vacuum source to draw the thrombus through the catheter's lumen. Exposed thrombus is at risk of detachment during catheter removal, potentially leading to failed recanalization. To address this challenge, attempts have been made to use expandable covered stents, which are advanced through a small-diameter sheath to the thrombus and then deployed distally from the sheath so that the distal portion of the stent expands radially into the arterial wall. In this way, the stent can retract the thrombus through its expanded port. One example of such a device is the ANCD Advanced Thrombectomy System from Anaconda Biomed SL.

[0005] Stent expansion may be achieved using a balloon catheter, where the stent typically has a frame comprised of stainless steel and is delivered to the target vessel while in a compressed state, after which it is expanded using the balloon catheter. This deforms the stent beyond its elastic range, causing it to plastically and permanently deform into an expanded state. This assumes that the vessel diameter is large enough to allow the stent to expand sufficiently to permanently deform; if the vessel is not large enough, the balloon catheter may not be able to successfully induce permanent expansion of the stent. This can be problematic given the variability in vessel diameter.

[0006] Self-expanding stents have the potential to overcome some of the challenges of balloon catheters. Self-expanding stents can include a frame containing a superelastic, shape-memory alloy, such as nitinol, that can bias the stent toward its expanded state when the stent is in a compressed state. To deliver a self-expanding stent to a thrombus, the stent is compressed and advanced through a sheath into the vasculature. Once deployed from the sheath, the self-expanding stent self-expands against the vessel wall with enough force to create a seal, which can draw the thrombus into the stent. While this self-expansion allows the stent to be used in vessels of various sizes, the radially outward bias of the stent can create friction between the stent and the sheath through which it passes, potentially impeding the stent's advancement through the vasculature. Although cooling a self-expanding stent, for example with liquid nitrogen, before advancing it through the vasculature can reduce the radially outward biasing force generated by the stent frame and mitigate the resulting friction, as the stent is advanced through the vasculature, the stent heats up due to higher body temperature, which in turn increases the force biasing the stent radially outward toward its expanded state due to the shape-memory alloy of the stent frame. Because the temperature of the stent rises relatively quickly and may reach body temperature before the self-expanding stent reaches the most tortuous parts of the vasculature, friction may still prevent the stent from advancing toward the thrombus, even with pre-advancement cooling. For this reason, self-expanding covered stents in current systems typically do not directly capture thrombus by suction. Instead, the self-expanding covered stent typically acts as a protective device, and a separate mechanism, such as a stent retriever, is advanced beyond the self-expanding stent to capture the thrombus and retract it back up to the self-expanding stent for removal. Summary of the Invention

[0007] To address these challenges, some of the stent delivery systems of the present invention can be configured to reduce the pressure within the lumen of a covered stent having a gas-impermeable membrane and a frame configured to bias the covered stent toward an expanded state when the covered stent is in a compressed state. The pressure within the lumen of the covered stent can be reduced before advancing the covered stent through the patient's vasculature. This reduces the pressure across the membrane of the covered stent, biasing the covered stent radially inward toward a compressed state and countering the radially outward force exerted by the frame of the covered stent. This can reduce friction between the covered stent and the surface(s) (e.g., of one or more tubes) over which the stent passes as it advances through the patient's vasculature when in a compressed state, thereby facilitating the advancement of the stent toward the thrombus. Therefore, the covered stent can more easily reach the thrombus. Here, the covered stent can be deployed by positioning at least a portion of the covered stent distal to any tube(s) through which the covered stent is threaded and increasing pressure within the lumen of the covered stent so that the frame can urge the covered stent radially outward into an expanded state for thrombus retraction.

[0008] The pressure within the lumen of the covered stent can be reduced using, for example, a delivery assist tube having a distal portion that can be configured to be positioned within the lumen of the covered stent when the covered stent is in a compressed state. The distal portion of the delivery assist tube can include multiple openings through the outer wall of the delivery assist tube, and the delivery assist tube can include a lumen extending from the proximal end of the delivery assist tube to the distal portion of the delivery assist tube. As a result, reducing the pressure at the proximal end of the delivery assist tube can cause gas to flow through the lumen from the distal portion to the proximal end of the delivery assist tube, thereby reducing the pressure within the distal portion. When the distal portion is positioned within the lumen of the covered stent, this reduced pressure can be transmitted to the lumen of the covered stent through the openings in the distal portion. As a result, the covered stent is drawn radially inward around the distal portion. A gas-impermeable membrane on the covered stent can seal the openings in the distal portion of the delivery assist tube to maintain a pressure reduction as the covered stent advances through the patient's vasculature.

[0009] In other embodiments, pressure within the lumen of the covered stent can be reduced using a pusher and a compliant bead coupled to the pusher. The compliant bead can be positioned within the lumen of the covered stent and form a seal with the inner surface of the covered stent within a distal portion of the covered stent such that gas cannot flow proximally within the lumen of the covered stent past the compliant bead when the covered stent is in a compressed state. Such a seal allows pressure to be reduced proximally of the covered stent, such as at the proximal end of a suction tube coupled to the proximal end of the covered stent, evacuating gas from the lumen of the covered stent and thereby reducing pressure within the lumen, thereby urging the covered stent radially inward toward a compressed state and facilitating advancement of the covered stent through the patient's vasculature.

[0010] Some details relating to these and other embodiments are described below.

[0011] The following drawings are illustrated by way of example, and not by way of limitation. For purposes of brevity and clarity, not every feature of a given structure is always labeled in every figure in which that structure appears. The same reference numbers do not necessarily indicate identical structures. Rather, the same or different reference numbers may be used to indicate similar features or features with similar functionality. [Brief explanation of the drawings]

[0012] [Figure 1A] 1 is a top view of a first embodiment of a stent delivery system of the present invention, including a stent assembly comprising a covered stent, a delivery assistance tube, and a first guide tube. [Figure 1B] 1B is a cross-sectional view of the stent assembly of the system of FIG. 1A taken along line 1B-1B of FIG. 1A when the covered stent is in an expanded state, and the proximal end of the covered stent is connected to a suction tube. [Figure 1C] FIG. 1C is a cross-sectional view of the delivery assist tube of the system of FIG. 1A taken along line 1C-1C in FIG. 1A, illustrating how the lumen of the delivery assist tube is in fluid communication with multiple openings that penetrate the outer wall of the distal portion of the delivery assist tube. [Figure 1D] 1D is a cross-sectional view of the first guide tube of the system of FIG. 1A taken along line 1D-1D in FIG. 1A. [Figure 1E] FIG. 1B is a top view of the system of FIG. 1A in an insertion configuration, with the covered stent of the stent assembly positioned within the lumen of the first guide tube and the distal portion of the delivery assistance tube positioned within the lumen of the covered stent. [Figure 1F] 1F is a cross-sectional view of the system of FIG. 1A taken along line 1F-1F of FIG. 1E. [Figure 1G] FIG. 1B is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A with the system in an insertion configuration, the covered stent of the stent assembly positioned within the lumen of the first guide tube, and the distal portion of the delivery aid tube positioned within the lumen of the covered stent. [Figure 2] FIG. 1C is a cross-sectional view of the stent assembly of FIG. 1B when the covered stent is in a compressed state. [Figure 3A] 3A-3C are cross-sectional views of stent assemblies of some stent delivery systems of the present invention that are substantially similar to the stent assembly of FIG. 1B, except that the assembly of FIG. 3A does not include a suction tube connected to the proximal end of the covered stent and the assembly of FIG. 3A includes a seal disposed around the proximal portion of the covered stent of FIG. 3A. The covered stent of FIG. 3A is in an expanded state. [Figure 3B] FIG. 3B is a cross-sectional view of the stent assembly of FIG. 3A when the covered stent is in a compressed state. [Figure 3C] 3C is a cross-sectional view of a second embodiment of a stent delivery system of the present invention, which is substantially the same as the stent delivery system of FIG. 1A, except that the system of FIG. 3C uses the stent assembly of FIG. 3A instead of the stent assembly of FIG. 1B. FIG. 3C shows the system in an insertion configuration, with a covered stent of the system positioned within the lumen of the first guide tube and a distal portion of the delivery assistant tube positioned within the lumen of the covered stent. [Figure 4] FIG. 4 is a cross-sectional view of a delivery assist tube in some stent delivery systems of the present invention, substantially similar to the delivery assist tube of FIG. 1B, except that the delivery assist tube of FIG. 4 includes two lumens, a first lumen that extends to a distal portion of the delivery assist tube and is in fluid communication with a plurality of openings in the delivery assist tube, surrounding a second lumen that extends from the proximal end of the delivery assist tube to the distal end of the delivery assist tube such that the distal end of the delivery assist tube includes an aperture. [Figure 5A] FIG. 1C is an enlarged top view of a distal portion of the delivery assist tube of FIG. 1B, illustrating how the multiple openings include multiple first slit pairs and multiple second slit pairs. [Figure 5B]FIG. 1C is an enlarged side view of a distal portion of the delivery assist tube of FIG. 1B, illustrating how the multiple openings include multiple first slit pairs and multiple second slit pairs. [Figure 5C] 5C-5C is a cross-sectional view of the delivery assist tube of FIG. 1B taken along line 5C-5C of FIG. 5A, illustrating how the outer wall of the delivery assist tube forms one of a first pair of slits. [Figure 5D] 5D is a cross-sectional view of the delivery assist tube of FIG. 1B taken along line 5D-5D of FIG. 5A, illustrating how the outer wall of the delivery assist tube forms one second pair of slits. [Figure 6A] 6A shows the system of FIG. 1A in an insertion configuration, with the proximal end of the delivery assist tube connected to a negative pressure source and a positive pressure source via a valve. In FIG. 6A, the valve is in a first state in which the negative pressure source is in fluid communication with the lumen of the delivery assist tube. [Figure 6B] 1A shows the system of FIG. 1A in an insertion configuration, with the proximal end of the delivery assist tube connected to a negative pressure source and a positive pressure source via a valve. In FIG. 6B, the valve is in a second state in which the positive pressure source is in fluid communication with the lumen of the delivery assist tube. [Figure 7A] 1B illustrates an embodiment of the system of FIG. 1A, with the covered stent positioned within the lumen of the introducer tube, where the covered stent is inserted into the lumen of the first guide tube of the system. [Figure 7B] 1B illustrates an embodiment of the system of FIG. 1A, with the covered stent positioned within the lumen of the introducer tube, where the covered stent is inserted into the lumen of the first guide tube of the system. [Figure 7C] 1B shows a covered stent of the system of FIG. 1A positioned in the proximal portion of the lumen of the first guide tube of the system of FIG. 1A after the introducer tube has been removed from the lumen of the first guide tube. [Figure 7D]FIG. 1B is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A, illustrating an embodiment in which the covered stent of the system is advanced to the distal end of the first guide tube of the system, with the distal portion of the delivery assist tube of the system positioned within the lumen of the covered stent. [Figure 7E] 1A , showing the system in a deployed configuration with the covered stent positioned relative to the first guide tube such that at least a portion of the covered stent is disposed distal to the distal end of the first guide tube and the distal portion of the delivery assist tube is disposed within the lumen of the covered stent. In FIG. 7E , a vacuum is applied within the lumen of the covered stent via the delivery assist tube, causing the covered stent to be in a compressed state. [Figure 7F] 1B is an enlarged cross-sectional view of a distal portion of the system of FIG. 1A with the system in a deployed configuration and the reduced pressure within the lumen of the covered stent released, causing the covered stent to be in an expanded state. [Figure 7G] 1B is an enlarged cross-sectional view of a distal portion of the system of FIG. 1A with the system in an aspiration configuration, the covered stent in an expanded state, and the delivery aid tube removed from the lumen of the covered stent. [Figure 8] 8 is an enlarged cross-sectional view of a distal portion of a third embodiment of a stent delivery system of the present invention, substantially similar to the system of FIG. 1A, except that the system of FIG. 8 does not include a delivery assist tube, but instead includes a pusher configured to be received in the lumen of the covered stent, and a compliant bead coupled to the pusher, the compliant bead configured to sealingly engage a distal portion of the covered stent when the covered stent is in a compressed state, thereby preventing gas from flowing from the distal end of the covered stent into the covered stent lumen proximal to the compliant bead. [Figure 9] FIG. 9 is an enlarged cross-sectional view of the distal portion of a fourth embodiment of the stent delivery system of the present invention, which is substantially the same as the system of FIG. 8, except that there is a lumen passing through the pusher and conformable bead of the system of FIG. [Figure 10A] FIG. 1 shows the vasculature of a patient with a thrombus located in the M1 segment of the middle cerebral artery. [Figure 10B] 10A shows the vasculature of FIG. 1A with the first guide tube of the system of FIG. 1A passing through the second guide tube and extending to the middle cerebral artery. In FIG. 10B, the distal end of the second guide tube is positioned proximal to the internal carotid artery. [Figure 10C] FIG. 10B is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A positioned within the vasculature of FIG. 10A, with the system in an insertion configuration and the distal ends of the first guide tube, the covered stent, and the delivery assistance tube positioned at the thrombus. [Figure 10D] FIG. 10B is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A deployed within the vasculature of FIG. 10A, with the system in a deployed configuration and pressure reduced within the lumen of the covered stent such that the covered stent is in a compressed state. [Figure 10E] 10A is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A deployed within the vasculature of FIG. 10A, showing the system in a deployed configuration with the reduced pressure within the lumen of the covered stent released, causing the covered stent to be in an expanded state. [Figure 10F] 10B is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A deployed within the vasculature of FIG. 10A, showing the system in an aspiration configuration with the delivery aid tube removed from the lumen of the covered stent. [Figure 10G] 10A is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A positioned within the vasculature of FIG. 10A with the system in an aspiration configuration, illustrating the aspiration of thrombus through the covered stent for removal. [Figure 10H] 10A is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A positioned within the vasculature of FIG. 10A with the system in an aspiration configuration, illustrating the aspiration of thrombus through the covered stent for removal. [Figure 10I]10A is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A positioned within the vasculature of FIG. 10A with the system in an aspiration configuration, illustrating the aspiration of thrombus through the covered stent for removal. [Figure 10J] 10B is an enlarged cross-sectional view of the distal portion of the system of FIG. 1A positioned within the vasculature of FIG. 10A with the system in an aspiration configuration, illustrating the aspiration of thrombus through the covered stent for removal. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1A-1G, a first embodiment 10a of a stent delivery system of the present invention is shown, which may include a covered stent 14 and one or more components, such as a delivery assistance tube 18 and / or a first guide tube 22, for facilitating delivery of the covered stent to a thrombus within a patient's vasculature.

[0014] 1B and with further reference to FIG. 2, covered stent 14 is radially expandable from a compressed state (FIG. 2) to an expanded state (FIG. 1B), and a maximum inner transverse dimension 42 (e.g., diameter) and a maximum outer transverse dimension 44 (e.g., diameter) of the covered stent (e.g., at distal end 38 b of the covered stent), measured perpendicular to a longitudinal axis 40 extending between proximal and distal ends 38 a, 38 b of the covered stent, are both greater when the covered stent is in the expanded state than when the covered stent is in the compressed state. By way of example, inner transverse dimension 42 and / or outer transverse dimension 44 of covered stent 14 when the covered stent is in the compressed state can be less than or equal to any one of, or between any two of, 80%, 70%, 60%, 50%, 40%, or 30% of the inner transverse dimension and / or outer transverse dimension, respectively, of the covered stent when the covered stent is in the expanded state. The expandability of the covered stent 14 allows the covered stent to be in a compressed state to facilitate advancement of the covered stent through the patient's vasculature when delivered to the thrombus, and then to be deployed and expanded to remove the thrombus through the covered stent, as described in further detail below.

[0015] When in the expanded state (1B), the covered stent 14 can be sized to contact the walls of a blood vessel within the patient's vasculature and attract thrombus, allowing thrombus to enter the covered stent through distal end 38b of the covered stent and pass through lumen 34 extending between proximal end 38a and distal end 38b of the covered stent. For example, when used within a patient's cerebral vasculature, the covered stent 14 when fully expanded may have a maximum internal transverse dimension 42 of any one or more of 0.25 centimeters (cm), 0.31 cm, 0.37 cm, 0.43 cm, 0.49 cm, 0.55 cm, or 0.61 cm, or any two between (e.g., at least 0.31 cm), and its external transverse dimension 44 may be any one or more of 0.38 cm, 0.44 cm, 0.50 cm, 0.56 cm, 0.62 cm, 0.68 cm, or 0.74 cm, or any two between (e.g., at least 0.445 cm). The covered stent 14 can also include a membrane 30 that can surround the lumen 34 of the covered stent, thereby blocking flow between portions of the patient's vasculature proximal and distal to the covered stent 14 when the covered stent is in an expanded state within the vasculature; thus, the membrane can facilitate the retraction of thrombus into the lumen of the covered stent. Suitable materials for the membrane 30 include polymers such as polytetrafluoroethylene (PTFE) and urethane. For example, PTFE advantageously exhibits low friction with other surfaces, thus facilitating insertion and deployment of the covered stent 14.

[0016] When in a compressed state (FIG. 2), the covered stent 14 is receivable into the lumen 154 of the first guide tube of the system 10a, which extends between the proximal end 158a and the distal end 158b of the first guide tube 22 (FIGS. 1D-1G), and the first guide tube can be sized to be advanced through the patient's vasculature, allowing the covered stent to be advanced through the first guide tube toward the thrombus, thereby facilitating advancement of the covered stent. For example, the internal transverse dimension 162 (e.g., diameter) of the first guide tube 22 can be any one or more of 0.10 cm, 0.11 cm, 0.12 cm, 0.13 cm, 0.14 cm, 0.15 cm, 0.16 cm, 0.17 cm, 0.18 cm, 0.19 cm, 0.20 cm, 0.21 cm, 0.22 cm, or 0.23 cm, or between any two of these (e.g., 0.13 cm or greater), and the external transverse dimension 166 (e.g., diameter) can be any one or less of 0.24 cm, 0.23 cm, 0.22 cm, 0.21 cm, 0.20 cm, 0.19 cm, 0.18 cm, 0.17 cm, or 0.16 cm, or between any two of these (e.g., 0.22 cm or less) (e.g., the first guide tube can be a 6F catheter).

[0017] Each component of system 10a may have a length that allows a user to advance covered stent 14 to the thrombus. For example, length 170 (FIG. 1D) of first guide tube 22, measured between proximal end 158a and distal end 158b, may be any one or more of 80 cm, 90 cm, 100 cm, 110 cm, 120 cm, 130 cm, or 140 cm, or any two between (e.g., at least 90 cm), sufficient to advance the first guide tube from an insertion point in the patient's groin to the internal carotid artery (ICA) or middle cerebral artery (MCA) (e.g., the M1 portion thereof). Thus, covered stent 14 may be advanced through first guide tube 22 from the groin to the ICA or MCA. Additionally, the covered stent 14 may have a length 46, measured between its proximal and distal ends 38a, 38b, sufficient to capture and retract thrombus (e.g., after retraction of the first guide tube 22, as described in further detail below). For example, the length 46 of the covered stent 14 (e.g., when the covered stent is in an expanded state) may be any one or more of 1.5 cm, 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm, 4.5 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm, 13 cm, or 14 cm, or any combination thereof. Furthermore, the covered stent 14 may be part of a stent assembly 50a having one or more extension elements 54 coupled to and positioned proximally of the covered stent. The total length 74 of the extension component(s) allows the covered stent to be reachable from the point of entry into the patient's vasculature to the thrombus through manipulation of the extension component(s).For example, the extension component(s) 54 can include a suction tube 58 and / or a pusher 70, and the length 74 of the extension component(s) (e.g., the length of the suction tube if the suction tube is the only component, the length of the pusher if the pusher is the only extension component, or the combined length of the suction tube and pusher if both are used) can be any one or more of 90 cm, 100 cm, 110 cm, 120 cm, 130 cm, 140 cm, or 150 cm, or between any two (e.g., at least 110 cm), thereby allowing the covered stent 14 to be advanced to the ICA or MCA, for example, by pushing the extension component(s). The most proximal of such extension component(s) 54 can remain accessible outside the patient's vasculature when the covered stent 14 is in the ICA or MCA (e.g., with the proximal end of the most proximal extension component positioned proximal to the proximal end 158a of the first guide tube 22 (in FIGS. 1E and 1F )), allowing a user to advance or retract the covered stent by pushing or pulling the most proximal extension component, respectively.

[0018] As shown, the extension component(s) 54 may include an aspiration tube 58 having a lumen 62 extending between a proximal end 66 a and a distal end 66 b of the aspiration tube, the distal end of which may be coupled to the proximal end 38 a of the covered stent 14, whereby thrombus drawn through the lumen 34 of the covered stent can then pass through the lumen of the aspiration tube. The interior transverse dimension 82 (e.g., diameter) of the aspiration tube 58 may be sufficiently large to facilitate such drawing, and the exterior transverse dimension 86 (e.g., diameter) of the aspiration tube may be sufficiently small to facilitate passage of the stent assembly 50 a through the patient's tortuous vasculature and for passage through any first guide tube 22. For example, the interior cross-sectional dimension 82 of the suction tube 58 can be any one or more of, or between any two of, 0.05 cm, 0.06 cm, 0.07 cm, 0.08 cm, 0.09 cm, 0.10 cm, 0.11 cm, 0.12 cm, 0.13 cm, 0.14 cm, 0.15 cm, or 0.16 cm (e.g., 0.09 cm or more), and the exterior cross-sectional dimension 86 can be any one or less of, or between any two of, 0.24 cm, 0.23 cm, 0.22 cm, 0.21 cm, 0.20 cm, 0.19 cm, 0.18 cm, 0.16 cm, 0.15 cm, 0.14 cm, or 0.13 cm (e.g., 0.16 cm or less, such as about 0.14 cm) (e.g., the suction tube can be a 4.2F catheter). Stent assembly 50a may also include a pusher 70 (e.g., a rod or guidewire) extending between proximal and distal ends 78a, 78b, the distal end of which is coupled to the proximal end of suction tube 58, such that pushing or pulling the pusher advances or retracts the suction tube and covered stent 14 relative to the thrombus while within the patient's vasculature. Thus, pusher 70 allows a user to move stent assembly 50a even when suction tube 58 extends only along a portion of the path between the insertion point and covered stent 14 within the patient's vasculature and is therefore inaccessible from outside the vasculature.In such a configuration, the smaller transverse dimension, and therefore more flexible, aspiration tube 58 can be more easily advanced deeper into the patient's vasculature than a larger transverse dimension, and therefore less flexible, tube (such as first guide tube 22) to aspirate the thrombus proximally through the aspiration tube lumen 62. The thrombus can then be advanced proximally through one or more larger transverse dimension tubes (e.g., at least the first guide tube) through which the thrombus can more easily pass (e.g., due to the larger transverse dimension).

[0019] In other embodiments, the extension component(s) 54 need not include the pusher 70, such as when the suction tube 58 is the only extension component and has a sufficient length to allow access to the suction tube from outside the vasculature when the covered stent 14 is in its target location within the vasculature (e.g., the ICA or MCA). Also, referring to FIGS. 3A and 3B , which illustrate a second embodiment 50b of the stent assembly of the present invention, the extension component(s) 54 need not include the suction tube 58 but may include only the pusher 70, for example. In some such embodiments, the stent assembly 50b may include a seal 90 disposed around the proximal portion of the covered stent 44 and coupled to the pusher 70, such that, as shown in FIG. 3C , the seal can sealingly engage the inner wall of the guide tube 22 when the covered stent 14 is positioned therein. In this manner, thrombus drawn through the lumen 34 of the covered stent 14 can travel directly to the lumen 154 of the guide tube 22, whose larger cross-sectional dimension may facilitate thrombus aspiration for removal.

[0020] To enable the covered stent 14 to expand from a compressed state to an expanded state to engage thrombus after being advanced through a patient's vasculature, the covered stent may have a frame 26 configured to bias the covered stent 14 toward the expanded state when the stent is in the compressed state. For example, the frame 26 may include braids and / or struts and may include a material that allows the frame to return to its original expanded shape when the covered stent 14 is in the compressed state. Such materials may include, by way of example, nitinol (i.e., an alloy containing nickel and titanium), which is superelastic and configured to expand when heated, and / or stainless steel. The frame 26 may be configured to bias the covered stent 14 toward the expanded state with sufficient force to form a seal with the vessel wall. For example, when the covered stent is in a compressed state and a surface surrounds the covered stent, the pressure that the covered stent exerts on the surface can be greater than or equal to any one of 60 kilopascals (kPa), 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, or 100 kPa (e.g., at least 85 kPa). The frame 26 can be coupled to the membrane 30 in any suitable manner, such as when the frame is adhered to the inner surface of the membrane or when it is embedded within the membrane.

[0021] If unopposed, the bias of frame 26, which tends to expand covered stent 14 when covered stent 14 is in a compressed state, can promote friction between the covered stent and the surface(s) it contacts as it is advanced through the patient's vasculature toward a thrombus (e.g., the inner surface of first guide tube 22), thereby potentially impeding such advancement. To counteract that bias during advancement of covered stent 14, system 10a can be configured to reduce the pressure within lumen 34 of the covered stent to create a pressure differential between the lumen and the environment outside the lumen (e.g., across membrane 30) that creates a radially inward force that counteracts the radially outward biasing force generated by frame 26.

[0022] With particular reference to FIG. 1C , such reduced pressure can be achieved at least via the delivery assist tube 18 of the system 10a. As shown, the delivery assist tube 18 can extend between a proximal end 94a and a distal end 94b and can include a distal portion 98. The distal portion 98 includes a distal end and can have a plurality of openings 102 extending through the outer wall of the delivery assist tube, such as, for example, any one or more of 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, or 300 openings, or any number between these numbers (e.g., at least 200 openings). As shown in FIGS. 1F and 1G , the distal portion 98 of the delivery assist tube 18 can be configured to be disposed within the lumen 34 of the covered stent 14 (e.g., when the covered stent is in a compressed state). For example, the maximum transverse dimension 106 (e.g., diameter) of the distal portion 98 of the delivery aid tube 18 can be equal to or less than any one of 0.20 cm, 0.19 cm, 0.18 cm, 0.17 cm, 0.16 cm, 0.15 cm, 0.14 cm, 0.13 cm, 0.12 cm, 0.11 cm, or 0.10 cm, or between any two (e.g., equal to or less than 0.16 cm), and the length 128 of the distal portion of the delivery aid tube can be equal to or less than, for example, 1.75 cm, 2.25 cm, 2.75 cm, 3.25 cm, 3.75 cm, 4.25 cm, or 5.25 cm. The length 124 of the delivery assist tube may be approximately the same as the length 46 of the covered stent when it is in a compressed state, such as any one or more of, or between any two of, 4.75 cm, 5.25 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, or 15 cm, and / or any one or less of, or between any two of, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, or 5% of the length 124 of the delivery assist tube. The delivery assist tube may include a lumen 110 extending from the proximal end 94 a of the delivery assist tube to the distal portion of the delivery assist tube such that applying a vacuum at the proximal end of the delivery assist tube will expel gas within the distal portion through the lumen and towards the proximal end of the delivery assist tube.When the distal portion 98 of the delivery assist tube 18 is positioned within the lumen 34 of the covered stent 14 and the delivery assist tube is compressed around the distal portion, the venting of gas can create a reduced pressure within the distal portion 98 of the delivery assist tube, which is transmitted to the lumen of the covered stent (via openings 102, which can be in fluid communication with lumen 110 through which the vented gas passes), creating a pressure differential that urges the covered stent radially inward around the distal portion of the delivery assist tube. Because the membrane 30 of the covered stent 14 can be gas impermeable, the openings 102 can be sealed to prevent the ingress of gas from outside the lumen 34, thereby maintaining the reduced pressure caused by the venting through the lumen 110 of the delivery assist tube 18. Additionally, when pressure is reduced at the proximal end 94a of the delivery assist tube, the distal end 94b of the delivery assist tube 18 can be closed so that there is no entry point for gas into the distal portion 98 and, therefore, the lumen 34 of the covered stent 14. Alternatively, and still referring to FIG. 4 , the lumen 110 of the delivery assist tube 18 can be the first lumen of the delivery assist tube, and the delivery assist tube can include a second lumen 118 that is surrounded by the first lumen and extends from the proximal end 94a to the distal end 94b of the delivery assist tube such that the distal end of the delivery assist tube includes an aperture 122. Because the second lumen extends to the proximal end of the delivery assist tube, when pressure is reduced at the proximal end of the delivery assist tube, gas that may enter the second lumen through an aperture in the distal end of the tube will not enter the lumen 34 of the covered stent 14. In such an embodiment, the second lumen 118 may be configured to receive, for example, a guidewire, such that the delivery assistance tube 18 may be advanced within the patient's vasculature along the guidewire extending through the second lumen.

[0023] The lumen 110 of the delivery aid tube 18 can be sized so that a sufficient amount of gas can be easily evacuated from the lumen, for example, using a syringe to create a pressure differential that can counteract the radially outward biasing force of the frame 26 of the covered stent 14. For example, the internal cross-sectional dimension 114 (e.g., diameter) of the lumen 110 can be equal to or less than any one of 0.18 cm, 0.17 cm, 0.16 cm, 0.15 cm, 0.14 cm, 0.13 cm, 0.12 cm, 0.11 cm, 0.10 cm, 0.09 cm, or 0.08 cm, or between any two (e.g., equal to or less than 0.14 cm), and the lumen can have a volume of 2 cubic centimeters (cm 3 ), 1.9cm 3 , 1.8cm 3 , 1.7cm 3 , 1.6cm 3 , 1.5cm 3 , 1.4cm 3 , 1.3cm 3 , 1.2cm 3 , 1.1cm 3 , or 1.0 cm 3 or between any two (e.g., 1.5 cm 3 (See below). Furthermore, the total area of the openings 102, which can affect the magnitude of the radially inward force resulting from a pressure differential, can be sufficient to counteract the radially outward biasing force of the frame 26 of the covered stent 14 due to reduced pressure. For example, the total area of the openings 102 can be any one or more of, or between any two of, 20%, 30%, 40%, 50%, 60%, 70%, or 80% (e.g., at least 40%) of the surface area of the inner surface of the gas impermeable membrane 30 of the covered stent 14 when the covered stent is in a compressed state.

[0024] The delivery assist tube 18 may have a length 124 that enables it to be advanced through the patient's vasculature to a desired location while maintaining access to the proximal end 94a of the delivery assist tube, with its distal portion 98 disposed within the lumen 34 of the covered stent 14. Such access to the proximal end 94a of the delivery assist tube 18 allows the user to control the pressure at the proximal end, and therefore the pressure within the lumen 34 of the covered stent 14, which is in fluid communication with the proximal end of the delivery assist tube via the opening 102 and lumen 110 of the delivery assist tube. For example, to allow advancement from an insertion point in the groin to the ICA or MCA, the length 124 of the delivery assist tube 18, measured between the proximal end 94a and the distal end 94b of the delivery assist tube, can be any one or more of 90 cm, 100 cm, 110 cm, 120 cm, 130 cm, 140 cm, 150 cm, or 160 cm, or between any two (e.g., at least 120 cm).

[0025] Preferably, the delivery assist tube 18 is relatively flexible so that it can be easily advanced through a patient's vasculature. For example, the delivery assist tube 18 may include a resilient material, such as nitinol, that promotes its flexibility. With further reference to FIGS. 5A-5D , the distal portion 98 of the delivery assist tube 18 may have a geometry that defines openings that, when the distal portion of the delivery assist tube is positioned within the lumen 34 of the covered stent 14, not only allows reduced pressure at the proximal end 94a of the delivery assist tube to draw the covered stent 14 radially inward, but also further promotes flexibility of the distal portion, thereby facilitating advancement of the delivery assist tube through a patient's tortuous vasculature. As shown, the openings 102 of the delivery assist tube 18 may include a plurality of slits, each of which may extend circumferentially substantially perpendicular to a longitudinal axis 142 extending between the proximal and distal ends 94a, 94b of the delivery assist tube. To form the slits 102, the outer wall of the delivery-assist tube 18 may include, at the distal portion 98, a plurality of circumferential segments 122 each extending in the circumferential direction, and a plurality of axial segments 126a-126d each extending in an axial direction 134 substantially parallel to the longitudinal axis 142 between two circumferential segments. Here, each of the plurality of slits (including substantially all of them) may be defined by two axial segments and two circumferential segments. To enhance flexibility, the width 146 (e.g., measured along the axial direction 134) of each circumferential segment 142 and the width 148 (e.g., measured along the radial direction) of each axial segment 126a-126d may each be relatively small, for example, 0.10 cm, 0.09 cm, 0.08 cm, 0.07 cm, 0.06 cm, 0.05 cm, 0.04 cm, 0.03 cm, or 0.02 cm or between any two of these (e.g., 0.05 cm or less).Each slit 102 can similarly be relatively narrow to balance the effective slit area for applying a radially inward force to the covered stent 14 and the strength of the distal portion 98, for example, each slit can have a width 150 (e.g., measured along the axial direction 134) that is equal to or less than any one of, or between, 0.10 cm, 0.09 cm, 0.08 cm, 0.07 cm, 0.06 cm, 0.05 cm, 0.04 cm, 0.03 cm, or 0.02 cm, which width can be approximately the same as the width 146 of each circumferential segment 142 and / or the width 148 of each axial segment 126a-126d, as desired.

[0026] To enhance multidirectional flexibility, subsets of axial segments 126a-126d may be present at different circumferential positions. For example, as shown, axial segments 126a-126d may include a plurality of first axial segments 126a, a plurality of second axial segments 126b, a plurality of third axial segments 126c, and a plurality of fourth axial segments 126d spaced at right angles. Centered on longitudinal axis 142, angular spacing 138a between each of the first and second axial segments is approximately 180° (FIG. 5C), angular spacing 138b between each of the third and fourth axial segments is approximately 180° (FIG. 5D), and angular spacings 138c between each of the first and third axial segments and 138d between each of the first and fourth axial segments are each approximately 90° (FIG. 5C). When viewed radially perpendicular to longitudinal axis 142, each first axial segment 126a is positioned across from a corresponding second axial segment 126b, and each third axial segment 126c is positioned across from a corresponding fourth axial segment 126d, resulting in multiple pairs of first and second axial segments and multiple pairs of third and fourth axial segments, with the first and second axial segment pairs and the third and fourth axial segment pairs alternating along axial direction 134. As a result, slit 102 can include multiple first slit pairs 130a and multiple second slit pairs 130b. FIG. 5C is a cross-sectional view taken along a line passing through one of the first slit pairs, and FIG. 5D is a cross-sectional view taken along a line passing through one of the second slit pairs.As shown, for each first pair of slits 130a of slits 102, two circumferential segments 122, one first axial segment 126a, and one second axial segment 126b may define each slit of the first pair, and for each second pair of slits 130b, two circumferential segments, one third axial segment 126c, and one fourth axial segment 126d may define each slit of the second pair of slits. Each first pair of slits 130a of slits 102 may be adjacent to at least one second pair of slits 130b, with the pairs of first and second axial segments 126a and 126b alternating with the pairs of third and fourth axial segments 126c and 126d along the axial direction 134. This geometry may enhance the flexibility of distal portion 98 in multiple directions perpendicular to axial direction 134, thereby facilitating advancement through a patient's vasculature.

[0027] Delivery assist tube 18 may be configured to be coupled to a negative pressure source, which may reduce pressure at delivery assist tube proximal end 94a, thereby forcing gas to escape through delivery assist tube lumen 110 and creating a pressure differential that urges covered stent 14 radially inward. With reference to FIGS. 6A and 6B, negative pressure source 182 may be coupled to delivery assist tube 18 proximal end 94a via valve 174. Valve 174 may have first, second, and third ports 178a-c and may be switched between a first state and a second state by turning valve handle 190. In a first state, the third port 178c can be in fluid communication with the first port 178a but not with the second port 178b ( FIG. 6A ), and in a second state, the third port can be in fluid communication with the second port but not with the first port ( FIG. 6B ). The third port 178c of the valve 174 can be coupled to the proximal end 94a of the delivery assist tube 18, and a negative pressure source 182 can be coupled to the first port 178a of the valve, such that the negative pressure source is in fluid communication with the lumen 110 of the delivery assist tube when the valve is in the first state. As a result, the negative pressure source reduces pressure at the proximal end of the delivery assist tube, thus evacuating gas through the lumen of the delivery assist tube and reducing pressure within the distal portion of the delivery assist tube and the lumen of the covered stent when the distal portion 98 of the delivery assist tube is within the lumen 34 of the covered stent 14. As shown, the negative pressure source 182 may include a syringe configured to draw a sufficient amount of gas from the lumen 110 to create the necessary vacuum to counteract the radially outward bias of the frame 26 of the covered stent 14, e.g., the syringe may have a capacity of 20 cm. 3 , 21cm 3 , 22cm 3 , 23cm 3 , 24cm 3 , 25cm 3 , 26cm 3 , 27cm 3 , 28cm 3 , 29cm 3 , 30cm 3 , 31cm 3, or 32cm 3 or between any two (e.g., at least 25 cm 3 ). In other embodiments, negative pressure source 182 may comprise a pump, such as an electromechanical pump. When negative pressure source 182 is in fluid communication with lumen 110 of delivery assist tube 18 and distal portion 98 of the delivery assist tube is disposed within lumen 34 of covered stent 14 (e.g., when the covered stent is in a compressed state), the negative pressure source may be configured to reduce the pressure within the lumen of the covered stent by any one or more of 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, or 105 kPa, or between any two (e.g., at least 90 kPa).

[0028] The proximal end 94a of the delivery assist tube 18 may also be coupled to a positive pressure source 186, such as a syringe or pump, such as through valve 174, whose second port 178b may be coupled to the positive pressure source, such that the positive pressure source is in fluid communication with the lumen 110 of the delivery assist tube when the valve is in its second state. The positive pressure source 186 may be configured to increase the pressure within the lumen 110 of the delivery assist tube, and thus within the lumen 34 of the covered stent 14, after depressurization (e.g., by introducing a liquid therein). This allows the covered stent to expand from a compressed state to an expanded state for deployment by being forced radially outward from at least its frame 26. As shown, two separate pressure sources, i.e., a negative pressure source 182 and a positive pressure source 186, may be coupled to the proximal end 94a of the delivery assist tube 18; however, in other embodiments, the negative pressure source may also function as a positive pressure source (e.g., configured to apply both vacuum and pressure at the proximal end of the delivery assist tube).

[0029] 7A-7G, a procedure is shown in which, when using a delivery assist tube 18, a covered stent 14 is advanced in a compressed state through a first guide tube 22, from which it is deployed and expanded to an expanded state. Prior to reducing the pressure at the proximal end 94a of the delivery assist tube 18 and prior to introducing the covered stent 14 into the lumen 154 of the first guide tube 22, the covered stent may be positioned within an introducer tube 192, such as a peelable sheath or dilator, with the distal portion 98 of the delivery assist tube positioned within the lumen 34 of the covered stent (FIG. 7A). In this configuration, the introducer tube 192 helps maintain the covered stent 14 in a compressed state, allowing its gas-impermeable membrane 30 to engage the distal portion 98 of the delivery assist tube 18 and form a seal with the opening 102. Thereafter, the pressure within the distal portion 98 of the delivery assist tube 18 can be reduced, e.g., by reducing the pressure at the proximal end 94a of the delivery assist tube using a negative pressure source 182, which may be coupled to the proximal end of the delivery assist tube via, e.g., valve 174, as described above, to radially bias the covered stent 14, creating a pressure differential that counteracts the radially outward biasing force generated by the covered stent frame 26. After the pressure has been reduced, the introducer tube 192 can be inserted into the lumen 154 of the first guide tube 22 with the covered stent 14 disposed within the introducer tube and the distal portion 98 of the delivery assist tube 18 disposed within the lumen 34 of the covered stent (FIG. 7B). The introducer tube can then be removed, leaving the covered stent and at least the distal portion of the delivery assist tube in place within the lumen of the first guide tube (FIG. 7C).

[0030] With covered stent 14 introduced into lumen 154 of first guide tube 22 and urged radially inward around distal portion 98 of delivery assist tube 18, the covered stent and delivery assist tube may be advanced through the lumen of the first guide tube toward distal end 158b of the covered stent (FIG. 7D). To deploy covered stent 14, the covered stent may be positioned relative to first guide tube 22 so that at least a portion of it is distal to distal end 158b of the first guide tube, such as by retracting the first guide tube and / or advancing the covered stent (FIG. 7E). With the covered stent 14 so positioned, pressure can be increased within the lumen 34 of the covered stent so that the pressure differential biasing the covered stent radially inward around the distal portion 98 of the delivery assist tube 18 is eliminated, thereby allowing the frame 26 of the covered stent to bias the covered stent radially outward toward its expanded state ( FIG. 7F ). The delivery assist tube 18 can then be withdrawn from the lumen 34 of the covered stent 14 and the lumen 154 of the first guide tube 22 ( FIG. 7G ), thereby providing a path for thrombus to be entrapped through the covered stent and removed proximally toward the proximal end 158 a of the first guide tube.

[0031] 8 and 9, in some embodiments, a mechanism other than the delivery assist tube 18 can be used to reduce pressure within the lumen 34 of the covered stent 14 to urge the covered stent radially inward toward the compressed state. For example, the embodiments shown in FIGS. 8 and 9 can each include a pusher 194 configured to be received within the lumen 34 of the covered stent 14 and a compliant bead 198 coupled to the pusher and configured to sealingly engage the inner surface of the distal portion of the covered stent when the covered stent is in the compressed state to prevent gas from flowing from the distal end 98b of the covered stent into the portion of the lumen of the covered stent proximal to the compliant bead. With such a seal formed by the compliant bead 198, reducing pressure at a location proximal to the compliant bead can evacuate gas from the lumen 34 of the covered stent 14, reducing the pressure within the lumen, resulting in a pressure differential that urges the covered stent radially inward. Illustratively, with the suction tube 58 connected to the proximal end 38a of the covered stent 14, gas can be evacuated from the lumen 34 of the covered stent 14 by reducing the pressure at the proximal end 66a of the suction tube, thereby reducing the pressure within the lumen (e.g., using a negative pressure source such as a syringe or pump connected to the proximal end of the suction tube, and optionally via the same valve arrangement that can connect the proximal end 94a of the delivery aid tube 18 to a negative pressure source (and, optionally, a positive pressure source)). The lumen 62 of the suction tube 58 can be of an appropriate volume to allow sufficient gas evacuation to create a reduced pressure that can urge the covered stent 14 radially inward, e.g., 2 cm. 3 , 1.9cm 3 , 1.8cm 3 , 1.7cm 3 , 1.6cm 3 , 1.5cm 3 , 1.4cm 3 , 1.3cm 3 , 1.2cm 3 , 1.1cm 3 , or 1.0 cm 3or a volume between any two of these (e.g., 1.5 cm 3 (See below). The pusher 194 allows the compliant bead 198 to be moved in and out of the lumen 34 of the covered stent 14 and may comprise, for example, a guidewire or rod (FIG. 8), or a microcatheter. In the case of a microcatheter, a lumen 202 extends from the proximal end of the microcatheter through the bead 198 to allow a guidewire to pass through the microcatheter and bead, thereby permitting advancement within the patient's vasculature along the guidewire (FIG. 9). The pusher 194 may be more flexible than the delivery aid tube 18, thereby facilitating advancement of the system through the patient's vasculature.

[0032] Referring to Figures 10A-10J, several methods for thrombus removal of the present invention are illustrated. As shown, a thrombus (e.g., 210) may be present in a patient's vasculature (e.g., 206), such as the patient's ICA (e.g., 214) or MCA (e.g., 218) (e.g., its M1 segment) (Figure 10A). Some methods include advancing a first guide tube (e.g., 22) (e.g., any of those described above) through the patient's vasculature, as needed, so that the distal end (e.g., 158b) of the first guide tube is positioned in the ICA or MCA (e.g., where the thrombus is located) (Figure 10B). Some systems of the present invention may include a second guide tube (e.g., 210) that is substantially identical to the first guide tube, with the primary exception that the lumen of the second guide tube is larger than the lumen of the first guide tube and is configured to receive the first guide tube. For example, the internal transverse dimension (e.g., diameter) of the lumen of the second guide tube can be equal to or less than any one of 0.18 cm, 0.19 cm, 0.20 cm, 0.21 cm, 0.22 cm, 0.23 cm, 0.24 cm, 0.25 cm, or 0.26 cm, or between any two of these (e.g., equal to or less than 0.22 cm) (e.g., the second guide tube can be a 6F catheter or a 6F sheath). As shown in FIG. 10B , in some methods using one of such systems, the second guide tube can be advanced through a patient's vasculature, and advancing the first guide tube through the patient's vasculature can include advancing the first guide tube through the second guide tube and beyond the distal end (e.g., 212b) of the second guide tube. Thus, the second guide tube can facilitate advancement of the first guide tube through a portion of the vasculature where a thicker, and therefore less flexible, second guide tube would have difficulty passing.For example, when the thrombus is within the ICA or MCA, the distal end of the thicker second guide tube can be positioned proximal to the ICA and / or MCA, and the thinner first guide tube can be advanced through the ICA and / or MCA until it reaches the thrombus beyond the distal end of the second guide tube.

[0033] Some methods include reducing the pressure in the lumen (e.g., 34) of a covered stent (e.g., 14) (e.g., any of those described above) so that a pressure differential urges the covered stent radially inward into a compressed state, and advancing the covered stent through the first guide tube while the pressure in the lumen of the covered stent is reduced and the covered stent is in a compressed state (FIG. 10C). The reduction in pressure in the lumen of the covered stent can be performed so that the pressure in the lumen is reduced by any one or more of 70 kilopascals (kPa), 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, or 105 kPa, or between two (e.g., at least 90 kPa). The pressure reduction and advancement can be achieved by any of the methods described above. For example, when using a delivery assist tube (e.g., 18) (any of those described above), pressure may be reduced by positioning at least a distal portion (e.g., 98) of the delivery assist tube (where the distal portion includes the distal end (e.g., 94b) of the delivery assist tube and a plurality of openings (e.g., 102) through the outer wall of the delivery assist tube) within the lumen of the covered stent, and reducing pressure at the proximal end (e.g., 94a) of the delivery assist tube (e.g., using a negative pressure source (e.g., 182) such as a syringe or pump) when the covered stent is in a compressed state so that gas flows from the distal portion of the delivery assist tube, through the lumen (e.g., 110), and to the proximal end. Alternatively, if a pusher (e.g., 194) having a compliant bead (e.g., 198) coupled thereto is used, the compliant bead may be positioned within the lumen of the covered stent to form a seal within its distal portion with the inner surface of the covered stent, and pressure may be reduced at the proximal end (e.g., 66a) of the suction tube (e.g., 58) coupled to the proximal end (e.g., 38a) of the covered stent such that gas flows from the lumen of the covered stent toward the proximal end of the suction tube. As explained above, the reduced pressure may be applied before the covered stent is positioned within the lumen of the first guide tube.Optionally, the first guide tube can receive the covered stent with the covered stent disposed within an introducer tube (e.g., 192), which can be removed from the first guide tube after the covered stent is received within the lumen of the first guide tube. The covered stent can then be advanced through the first guide tube (e.g., with a distal portion of a delivery aid tube or a compliant bead disposed within the lumen of the covered stent).

[0034] Some methods include expanding the covered stent from a compressed state to an expanded state within the patient's vasculature after advancing the covered stent through the first guide tube (FIGS. 10D and 10E). As described above, this can include positioning the covered stent relative to the first guide tube (e.g., by retracting the first guide tube by pulling it proximally and / or advancing the covered stent by pushing one or more extension component(s) (e.g., 54) of the stent assembly of the covered stent) so that at least a portion of the covered stent is disposed distal to the distal end of the first guide tube (FIG. 10D), and increasing pressure within the lumen of the covered stent so that the frame (e.g., 26) of the covered stent urges the covered stent radially outward toward the expanded state (FIG. 10E). Increasing the pressure in the lumen of the covered stent can include, for example, introducing a liquid, such as saline solution, into the lumen of the covered stent using a positive pressure source (e.g., 186) such as a syringe or pump. For example, if a delivery auxiliary tube is used, the liquid can be introduced into the lumen of the delivery auxiliary tube through its proximal end, flow to the distal portion of the delivery auxiliary tube, and enter the lumen of the covered stent through its opening. If a pusher with a compliant beat is used, the liquid can be introduced into the lumen of the suction tube through its proximal end and then flow into the lumen of the covered stent. In the expanded state, the covered stent can engage the patient's vasculature and block blood flow proximal and distal to the covered stent.

[0035] Some methods include retracting one or more components (such as a delivery assist tube or a pusher to which a compliant bead is connected) used to reduce the pressure within the lumen of the covered stent while the covered stent is in an expanded state (FIG. 10F), thereby drawing the thrombus into the distal end of the covered stent and aspirating it through the lumen of the covered stent (FIGS. 10G-10J). Aspirating the thrombus involves reducing pressure (e.g., using a syringe or pump) at the proximal end of the first guide tube and / or optional aspiration tube, creating a negative pressure difference between the distal end of the covered stent and the proximal end of the first guide tube and / or aspiration tube, which can draw the thrombus into the covered stent. Because the covered stent is in an expanded state, such retraction can occur easily. After passing through the lumen of the covered stent, the thrombus can travel proximally through one or more tubes of the system, such as the optional aspiration tube, the first guide tube, and / or the second guide tube, for removal from the vasculature.

[0036] Some of the stent delivery systems of the present invention include a covered stent including a lumen, and some of the methods of use for thrombus removal of the present invention include reducing the pressure within the lumen of the covered stent. In some embodiments, the covered stent is radially expandable from a compressed state to an expanded state, and the maximum transverse dimension of the lumen of the covered stent, measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the covered stent, is greater when the covered stent is in the expanded state than when the covered stent is in the compressed state.

[0037] In some embodiments, the covered stent comprises a frame configured to bias the covered stent to an expanded state when the covered stent is in a compressed state. In some embodiments, the frame is configured to bias the covered stent to an expanded state with a force such that when the covered stent is in a compressed state and the surface surrounds the covered stent, the pressure exerted by the covered stent on the surface is at least 85 kilopascals (kPa). In some embodiments, the frame comprises nitinol.

[0038] In some embodiments, the covered stent comprises a gas impermeable membrane coupled to a frame, hi some embodiments, the lumen of the covered stent is surrounded by a gas impermeable membrane.

[0039] Some stent delivery systems include a delivery assistant tube having a distal portion configured to be disposed within the lumen of the covered stent, and some methods of reducing pressure within the lumen of the covered stent include disposing the distal portion of the delivery assistant tube within the lumen of the covered stent. In some embodiments, the distal portion of the delivery assistant tube comprises a distal end of the delivery assistant tube and a plurality of openings extending through the outer wall of the delivery assistant tube. In some embodiments, the combined area of the openings is at least 40% of the surface area of the inner surface of the gas impermeable membrane. In some embodiments, the delivery assistant tube includes a lumen extending from the proximal end of the delivery assistant tube to the distal portion of the delivery assistant tube and in fluid communication with the openings. In some systems, the distal portion of the delivery assistant tube is disposed within the lumen of the covered stent, and the proximal end of the delivery assistant tube is coupled to a negative pressure source, such that the negative pressure source is in fluid communication with the lumen of the delivery assistant tube. In some methods, reducing the pressure within the lumen of the covered stent includes reducing the pressure at a proximal end of the delivery assist tube such that gas flows through the lumen of the delivery assist tube from a distal portion of the delivery assist tube to a proximal end of the delivery assist tube. In some methods, reducing the pressure within the lumen of the covered stent is performed such that the pressure within the lumen is reduced by at least 90 kilopascals (kPa).

[0040] In some embodiments, the opening in the distal portion of the delivery assist tube comprises a plurality of slits, each extending in a circumferential direction substantially perpendicular to a longitudinal axis extending between the proximal and distal ends of the delivery assist tube. In some embodiments, at the distal portion of the delivery assist tube, the outer wall of the delivery assist tube comprises a plurality of circumferential segments, each extending in a circumferential direction, and a plurality of axial segments, between two circumferential segments, each extending in an axial direction substantially parallel to the longitudinal axis extending between the proximal and distal ends of the delivery assist tube. In some embodiments, the axial segments include a plurality of first axial segments, a plurality of second axial segments, a plurality of third axial segments, and a plurality of fourth axial segments. In some embodiments, when centered on a longitudinal axis extending between the proximal and distal ends of the delivery assist tube, the angular spacing is approximately 180° between each of the first axial segments and each of the second axial segments, approximately 180° between each of the third axial segments and each of the fourth axial segments, and / or approximately 90° between each of the first axial segments and each of the third and fourth axial segments. In some embodiments, the slits include a plurality of first slit pairs and a plurality of second slit pairs. In some embodiments, for each first slit pair, two circumferential segments, one first axial segment, and one second axial segment define each slit of the first slit pair. In some embodiments, for each second slit pair, two circumferential segments, one third axial segment, and one fourth axial segment define each slit of the second slit pair. In some embodiments, each of the first pairs of slits is adjacent to at least one of the second pairs of slits when viewed axially.

[0041] In some embodiments, the distal end of the delivery assist tube is closed. In other embodiments, this lumen of the delivery assist tube is the first lumen of the delivery assist tube, and the delivery assist tube includes a second lumen extending from the proximal end of the delivery assist tube to the distal end of the delivery assist tube such that the distal end of the delivery assist tube includes an aperture. In some embodiments, the first lumen surrounds the second lumen.

[0042] In some embodiments, the delivery aid tubing comprises nitinol.

[0043] Some systems include a pusher configured to be received in the lumen of the covered stent and a compliant bead coupled to the pusher, wherein the compliant bead is configured to sealingly engage the inner surface of the distal portion of the covered stent when the covered stent is in a compressed state to prevent gas from flowing from the distal end of the covered stent into the portion of the lumen of the covered stent proximal to the compliant bead.

[0044] Some systems include a suction tube coupled to the proximal end of the covered stent. In some systems, a delivery aid tube is configured to move axially within the lumen of the suction tube. In some systems including a pusher, the pusher is configured to move axially within the lumen of the suction tube. In some such embodiments, the covered stent is in a compressed state, the pusher is disposed within the lumen of the suction tube and the lumen of the covered stent, the compliant bead is sealingly engaged with the inner surface of the distal portion of the covered stent, and the proximal end of the suction tube is coupled to a negative pressure source, which is in fluid communication with the lumen of the suction tube. In some systems, the volume of the lumen of the suction tube is 2 cubic centimeters (cm 3 ) or less, and / or the maximum external transverse dimension of the suction tube, measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the suction tube, is 1.6 millimeters (mm) or less.

[0045] Some systems include a guide tube. In some systems, the covered stent is configured to move axially within the lumen of the guide tube. In some systems, the guide tube has a maximum transverse dimension of 2.2 millimeters (mm) or less, measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the guide tube.

[0046] Some methods include advancing a first guide tube through a patient's vasculature, including advancing a covered stent through the first guide tube while the covered stent is in a compressed state with pressure in the lumen of the covered stent reduced. Some methods include advancing a second guide tube through the patient's vasculature such that a distal end of the second guide tube is positioned proximal to the patient's internal carotid artery and / or middle cerebral artery. In some such methods, advancing the first guide tube through the patient's vasculature includes advancing the first guide tube through and past a distal end of the second guide tube such that the distal end of the first guide tube is positioned within the internal carotid artery or the middle cerebral artery.

[0047] Some methods include advancing a covered stent through a first guide tube and then expanding the covered stent from a compressed state to an expanded state within the patient's vasculature. In some methods, expanding the covered stent from the compressed state to the expanded state includes positioning the covered stent relative to the first guide tube such that at least a portion of the covered stent is disposed distal to a distal end of the first guide tube and increasing pressure within a lumen of the covered stent. In some methods, increasing pressure within the lumen of the covered stent includes introducing a liquid into the lumen of the covered stent.

[0048] Some methods involve aspirating the thrombus into the distal end of the covered stent and through the lumen of the covered stent while the covered stent is in an expanded state.

[0049] The term "coupled" is defined as a connection, although not necessarily direct and not necessarily mechanical, and two items that are "coupled" may be integral to one another. The terms "a" and "an" are defined as one or more, unless the present disclosure expressly requires otherwise. The terms "substantially," "about," and "approximately" are all defined as and include the majority, but not necessarily the entirety, of what is specified, as will be understood by those skilled in the art. For example, substantially 90 degrees includes 90 degrees, and substantially parallel includes parallel. As used herein, "substantially parallel" means within 10 degrees of parallel, and "substantially perpendicular to" means within 10 degrees of perpendicular. In any of the disclosed embodiments, the terms "approximately" and "about" may be interpreted as "within a percentage" of what is specified, including 0.1 percent, 1 percent, 5 percent, and 10 percent.

[0050] The terms "comprise" and any of its forms "comprises," "comprising," etc., "have" and any of its forms "has," "having," etc., and "include" and any of its forms "includes," "including," etc., are open-ended linking verbs. Consequently, an apparatus or system that "comprises," "has," or "includes" one or more elements possesses, but is not limited to, possessing only those elements. Similarly, a method that "comprises," "has," or "includes" one or more steps possesses, but is not limited to, possessing only those steps.

[0051] Any embodiment of any product, system, and method may "consist of" or "consist essentially of" any of the described steps, elements, and / or features, rather than "comprising / including / having." Accordingly, in any claim, an open-ended linking verb may be substituted with the term "consisting of" or "consisting essentially of" to change the scope of a given claim to a different scope than would be the case if the open-ended linking verb above were used.

[0052] Also, a device or system configured in a certain way is at least so configured, but may be configured in other ways than that specifically described.

[0053] One or more features of one embodiment may be applied to other embodiments even if not described or shown, unless expressly prohibited by the nature of this disclosure or the embodiment.

[0054] The above description and examples provide a complete description of the structure and use of the illustrative embodiments. While certain embodiments have been described above in some detail, or with reference to one or more individual embodiments, those skilled in the art may make many modifications to the disclosed embodiments without departing from the scope of the present invention. Accordingly, the various illustrative embodiments of products, systems, and methods are not intended to be limited to the particular forms disclosed. Rather, they include all modifications and alternatives within the scope of the claims, and may include some or all of the features of the illustrated embodiments, except for embodiments other than those shown. For example, elements may be omitted or combined in a single structure, and / or connections may be substituted. Also, where appropriate, aspects of each example described above may be combined with aspects of other examples to form additional examples having similar or different characteristics and / or functionality and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to a single embodiment or to multiple embodiments.

[0055] The claims are not intended to, and should not be construed to, include means-plus-function or step-plus-function limitations unless expressly recited in a given claim using the phrase "means for" or "step for."

Claims

1. 1. A stent delivery system comprising:

1. A covered stent expandable from a compressed state to an expanded state, comprising: a frame configured to bias the covered stent toward the expanded state when the covered stent is in the compressed state; a gas impermeable membrane coupled to the frame; a lumen surrounded by the gas impermeable membrane; a covered stent, wherein a maximum transverse dimension of the lumen, measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the covered stent, is greater when the covered stent is in the expanded state than when the covered stent is in the compressed state; A delivery aid tube, comprising: a distal portion comprising a distal end of the delivery assistance tube and a plurality of openings extending through an outer wall of the delivery assistance tube, the distal portion of the delivery assistance tube being configured to be positioned within the lumen of the covered stent; a delivery auxiliary tube comprising: a lumen extending from a proximal end of the delivery auxiliary tube to the distal portion of the delivery auxiliary tube and in fluid communication with the opening; A stent delivery system comprising:

2. 2. The stent delivery system of claim 1, wherein the openings in the distal portion of the delivery assistance tube comprise a plurality of slits, each extending in a circumferential direction substantially perpendicular to a longitudinal axis extending between the proximal and distal ends of the delivery assistance tube.

3. Within the distal portion of the delivery assistance tube, the outer wall of the delivery assistance tube comprises: a plurality of circumferential segments each extending in the circumferential direction; a plurality of axial segments extending between two of the circumferential segments in an axial direction substantially parallel to the longitudinal axis extending between the proximal end and the distal end of the delivery assist tube, the plurality of axial segments including a plurality of first axial segments, a plurality of second axial segments, a plurality of third axial segments, and a plurality of fourth axial segments; The angular spacing about a longitudinal axis extending between the proximal and distal ends of the delivery auxiliary tube is: a distance of 180° between each of the first axial segments and each of the second axial segments; each of the third axial segments and each of the fourth axial segments is approximately 180°; each of the first axial segments and each of the third and fourth axial segments is approximately 90°; the slits include a plurality of first slit pairs and a plurality of second slit pairs; for each of the first pair of slits, two of the circumferential segments, one of the first axial segments, and one of the second axial segments define each slit of the first pair of slits; for each of the second pair of slits, two of the circumferential segments, one of the third axial segments, and one of the fourth axial segments define each slit of the second pair of slits; The stent delivery system of claim 2 , wherein each of the first pairs of slits is adjacent to at least one of the second pairs of slits when viewed in the axial direction.

4. The stent delivery system of claim 3 , wherein the total area of the openings is at least 40% of the surface area of the interior surface of the gas impermeable membrane.

5. The stent delivery system of claim 4 , wherein the distal end of the delivery aid tube is closed.

6. the lumen of the delivery auxiliary tube is a first lumen of the delivery auxiliary tube; the delivery auxiliary tube comprises a second lumen extending from the proximal end of the delivery auxiliary tube to the distal end of the delivery auxiliary tube such that the distal end of the delivery auxiliary tube includes an aperture; The stent delivery system of claim 4 , wherein the first lumen surrounds the second lumen.

7. a suction tube connected to the proximal end of the covered stent; The stent delivery system of claim 6 , wherein the delivery aid tube is configured to move axially within the lumen of the aspiration tube.

8. The stent delivery system of claim 7 , wherein the delivery aid tube comprises nitinol.

9. the distal portion of the delivery aid tube is disposed within the lumen of the covered stent; The stent delivery system of claim 8 , wherein the proximal end of the delivery assist tube is coupled to a negative pressure source such that the negative pressure source is in fluid communication with the lumen of the delivery assist tube.

10. 10. The stent delivery system of claim 9, wherein the frame is configured to bias the covered stent to an expanded state with a force such that when the covered stent is in the compressed state and a surface surrounds the covered stent, the covered stent exerts a pressure of at least 85 kilopascals (kPa) on the surface.

11. A method for use in removing a thrombus, comprising: advancing a first guide tube through the patient's vasculature; reducing the pressure within the lumen of the radially expandable covered stent from a compressed state to an expanded state; the covered stent comprises a frame configured to bias the covered stent to the expanded state when the covered stent is in the compressed state, and a gas impermeable membrane coupled to the frame and surrounding a lumen, wherein a maximum transverse dimension of the lumen measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the covered stent is greater when the covered stent is in the expanded state than when the covered stent is in the compressed state; The method further comprises: advancing the covered stent through the first guide tube while pressure within the lumen of the covered stent is reduced and while the covered stent is in the compressed state; After advancing the covered stent through the first guide tube, at least positioning the covered stent relative to the first guide tube such that at least a portion of the covered stent is disposed distal to the distal end of the first guide tube; and expanding the covered stent from the compressed state to the expanded state within the patient's vasculature by increasing pressure within the lumen of the covered stent.

12. 12. The method of claim 11, wherein reducing the pressure within the lumen of the covered stent is performed such that the pressure within the lumen is reduced by at least 90 kilopascals (kPa).

13. 13. The method of claim 12, wherein increasing the pressure within the lumen of the covered stent comprises introducing a liquid into the lumen of the covered stent.

14. advancing the second guide tube through the patient's vasculature so that a distal end of the second guide tube is positioned proximal to the patient's internal carotid artery and / or middle cerebral artery; 14. The method of claim 13, wherein advancing the first guide tube through the patient's vasculature comprises advancing the first guide tube through the second guide tube and over the distal end of the second guide tube such that the distal end of the first guide tube is positioned within the internal carotid artery or the middle cerebral artery.

15. 15. The method of claim 14, comprising aspirating thrombus into the distal end of the covered stent and through the lumen of the covered stent while the covered stent is in the expanded state.

16. Reducing pressure within the lumen of the covered stent comprises: placing a distal portion of a delivery assistant tube within the lumen of the covered stent, the distal portion comprising a distal end of the delivery assistant tube and a plurality of openings extending through an outer wall of the delivery assistant tube; 16. The method of claim 15, comprising reducing pressure at the proximal end of the auxiliary delivery tube such that gas flows through a lumen of the auxiliary delivery tube from the distal portion of the auxiliary delivery tube to the proximal end of the auxiliary delivery tube.

17. 17. The method of claim 16, wherein the opening in the distal portion of the delivery assistance tube comprises a plurality of slits, each extending in a circumferential direction substantially perpendicular to a longitudinal axis extending between the proximal and distal ends of the delivery assistance tube.

18. Within the distal portion of the delivery assistance tube, the outer wall of the delivery assistance tube comprises: a plurality of circumferential segments each extending in the circumferential direction; a plurality of axial segments extending between two of the circumferential segments in an axial direction substantially parallel to the longitudinal axis extending between the proximal end and the distal end of the delivery assist tube, the plurality of axial segments including a plurality of first axial segments, a plurality of second axial segments, a plurality of third axial segments, and a plurality of fourth axial segments; The angular spacing about a longitudinal axis extending between the proximal and distal ends of the delivery auxiliary tube is: each of the first axial segments and each of the second axial segments is approximately 180°; each of the third axial segments and each of the fourth axial segments is approximately 180°; each of the first axial segments and each of the third and fourth axial segments is approximately 90°; the slits include a plurality of first slit pairs and a plurality of second slit pairs; for each of the first pair of slits, two of the circumferential segments, one of the first axial segments, and one of the second axial segments define each slit of the first pair of slits; for each of the second pair of slits, two of the circumferential segments, one of the third axial segments, and one of the fourth axial segments define each slit of the second pair of slits; 18. The method of claim 17, wherein each of the first pairs of slits is adjacent to at least one of the second pairs of slits when viewed in the axial direction.

19. 20. The method of claim 18, wherein the total area of the openings is at least 40% of the surface area of the interior surface of the gas impermeable membrane.

20. 20. The method of claim 19, wherein the delivery aid tube comprises nitinol.

21. 1. A stent delivery system comprising:

1. A covered stent that is radially expandable from a compressed state to an expanded state, comprising: a frame configured to bias the covered stent toward the expanded state when the covered stent is in the compressed state; a gas impermeable membrane coupled to the frame; and a lumen surrounded by the gas-impermeable membrane; a covered stent, wherein a maximum transverse dimension of the lumen, measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the covered stent, is greater when the covered stent is in the expanded state than when the covered stent is in the compressed state; a pusher configured to be received within the lumen of the covered stent; a compliant bead connected to the pusher, the compliant bead configured to sealingly engage an inner surface of a distal portion of the covered stent when the covered stent is in the compressed state so as to prevent gas from flowing from the distal end of the covered stent into a portion of the lumen of the covered stent proximal to the compliant bead.

22. a suction tube connected to the proximal end of the covered stent; 22. The stent delivery system of claim 21, wherein the pusher is configured to move axially within the lumen of the aspiration tube.

23. The volume of the lumen of the suction tube is 2 cubic centimeters (cm ３ 23. The stent delivery system of claim 22, wherein:

24. 24. The stent delivery system of claim 23, wherein the maximum outer transverse dimension of the suction tube measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the suction tube is 1.6 millimeters (mm) or less.

25. the covered stent is in the compressed state; the pusher is disposed within the lumen of the suction tube and the lumen of the covered stent; the compliant bead is sealingly engaged with the inner surface of the distal portion of the covered stent; 25. The stent delivery system of claim 24, wherein a proximal end of the suction tube is coupled to a negative pressure source such that the negative pressure source is in fluid communication with the lumen of the suction tube.

26. 26. The stent delivery system of claim 25, wherein the frame is configured to bias the covered stent toward the expanded state with a force such that when the covered stent is in the compressed state and a surface surrounds the covered stent, the covered stent exerts a pressure of at least 85 kilopascals (kPa) on the surface.

27. A guide tube is provided, 27. The stent delivery system of claim 26, wherein the covered stent is configured to move axially within the lumen of the guide tube.

28. 28. The stent delivery system of claim 27, wherein the maximum transverse dimension of the guide tube measured perpendicular to a longitudinal axis extending between the proximal and distal ends of the guide tube is 2.2 millimeters (mm) or less.

29. 30. The stent delivery system of claim 28, wherein the frame comprises nitinol.

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