WO2024194603A1

WO2024194603A1 - Apparatus and methods for providing embolic protection during a transcatheter operation

Info

Publication number: WO2024194603A1
Application number: PCT/GB2024/050689
Authority: WO
Inventors: Giovanni Luigi DE MARIA; Yunlan ZHANG; Mohammad ALKHALIL; Zhong You; Yunfang YANG
Original assignee: Oxford University Innovation Limited
Priority date: 2023-03-21
Filing date: 2024-03-14
Publication date: 2024-09-26

Abstract

Methods and apparatus for providing embolic protection during a transcatheter operation are disclosed. In one arrangement, an apparatus comprises an elongate sheath insertable through the vascular system to a target site. A filter arrangement extends from a distal end of the sheath. The sheath is switchable between a radially contracted state and a radially expanded state. The sheath in the radially expanded state defines a central lumen for allowing insertion of a device for performing a transcatheter operation. The filter arrangement comprises a porous membrane switchable between a radially contracted state and a radially expanded state. The radially expanded state is such as to span a cross-section of a blood vessel to block debris from travelling past the porous membrane. A filter actuation system switches the porous membrane between the radially contracted state and the radially expanded state.

Description

APPARATUS AND METHODS FOR PROVIDING EMBOLIC PROTECTION DURING A TRANSCATHETER OPERATION

The present disclosure relates to apparatus and methods for providing embolic protection during a transcatheter operation. Disclosed arrangements are particularly suited for use in the aorta during interventional cardiac surgery, such as during Transcatheter Aortic Valve Implantation (TAVI).

TAVI, which is sometimes referred to as TAVR (Transcatheter Aortic Valve Replacement), is a minimally invasive procedure to replace a narrowed aortic valve that fails to open properly, a condition known as aortic valve stenosis. The procedure is being used increasingly due to safety advantages relative to open heart surgery alternatives.

TAVI procedures have been associated with silent ischaemic cerebral embolism and even clinical stroke caused by procedural debris reaching the cerebral vasculature during TAVI prosthesis deployment. In recent large-scale trials, around 5-6% of cases ended up with the occurrence of stroke or a transient ischemic attack, and stroke is associated with a 3.5-fold increase of mortality rates during the first month after TAVI. Aortic debris may be generated, for example, due to the use of large-sized catheters and rigid delivery systems in the calcified native valve and aortic wall. Additional balloon aortic valvuloplasty can be required in TAVI prosthesis deployment, with further risk of dislodgement and embolization of aortic debris and crushed calcified native valves. These embolic particles may enter the bloodstream and embolize to the brain or other organs downstream. Cerebral embolism can lead to occlusion of blood vessels, resulting in neuropsychological deficits, stroke and even death.

The risk of embolism has led to the development of Cerebral Embolic Protection Devices (CEPDs) to protect patients from these risks and thereby improve the outcome of relevant surgical procedures. CEPDs usually comprise a filter or protective sheath designed to capture or deflect emboli traveling to the brain during TAVI procedures in order to prevent embolic debris from reaching the supra-aortic vessels. In a typical TAVI procedure, a CEPD may be inserted percutaneously through the radial or femoral artery before deployment of the TAVI prosthesis. The CEPD may, for example, be placed across the origin of supra-aortic vessels. In some known CEPD devices, filters are deployed that cover some or all the branches of the aortic arch (the brachiocephalic artery, left common carotid artery and left subclavian artery) to prevent debris from entering cerebral circulation. Such devices may protect the brain region vessels, but they cannot prevent debris going to non-cerebral regions. Another type of device aims to provide full circumferential coverage of the aortic arch, protecting all supra-aortic vessels and preventing migration of debris to both cerebral and non-cerebral regions. However, such devices use a free-standing woven mesh filter, which is relatively costly and considerable skills are needed to master deployment of the device.

CEPD devices such as those discussed above provide varying levels of embolic protection and/or can be costly and/or complex to manufacture and/or use. They furthermore require a dedicated vascular access to be inserted in addition to the vascular access required to deliver the TAVI prosthesis, which places stress on the patient and complicates the surgical procedure.

It is an object of the present disclosure to at least partly address one or more of the challenges discussed above.

According to an aspect of the invention, there is provided an apparatus for providing embolic protection during a transcatheter operation, the apparatus comprising: an elongate sheath insertable through the vascular system of a subject to bring a distal end of the sheath to a target site in the vascular system; and a filter arrangement configured to extend from the distal end of the sheath, wherein: the elongate sheath is switchable between a radially contracted state and a radially expanded state, wherein the sheath in the radially expanded state defines a central lumen for allowing insertion to the target site, through the central lumen, of a device for performing a transcatheter operation; the filter arrangement comprises a porous membrane switchable between a radially contracted state and a radially expanded state, wherein the radially expanded state is such as to span a cross-section of a blood vessel at the target site to block debris generated upstream from travelling past the porous membrane through the porous membrane while allowing blood to flow past the porous membrane through the porous membrane; and a filter actuation system configured to switch the porous membrane between the radially contracted state and the radially expanded state. Thus, an apparatus is provided that uses a switchable porous membrane that can be inserted to a target site in a radially contracted state before being switched into a radially expanded state to provide protection against unwanted migration of debris downstream from a transcatheter operation generating the debris. The elongate sheath can adopt a radially contracted state to enable efficient insertion into the subject and then be switched into a radially expanded state to allow devices to be fed through the central lumen of the sheath to perform the transcatheter operation. Thus, the same sheath is used both to provide protection against debris (by accommodating the porous membrane and associated actuation system) and to provide access for performing the trancatheter operation. Multiple functions can thus be performed with requiring multiple corresponding incisions in the subject and associated operational complexity and added trauma. The porous membrane can span completely across the blood vessel, for example at a distal position in the ascending aorta, thereby allowing whole body protection against debris to be achieved (i.e., the porous membrane can prevent debris from entering branch vessels as well the descending aorta).

In an embodiment, the filter actuation system comprises one or more drive wires extending through the sheath and out of the distal end of the sheath; and the filter actuation system is configured such that longitudinal movement of the drive wires contributes to or causes the switching of the porous membrane between the radially contracted state and the radially expanded state. The use of drive wires configured in this way has been found to provide flexibility of operation, high reliability, and is not excessively complex or expensive to implement.

In an embodiment, each of one or more of the drive wires is a resilient drive wire mechanically coupled, directly or indirectly, to the porous membrane; and the filter arrangement comprises a constraining arrangement configured to constrain the resilient drive wire such that the longitudinal movement of the resilient drive wire causes the resilient drive wire to deform in a manner that radially expands the porous membrane. This configuration is structurally simple and compact because the drive wires provide dual functionality, allowing the actuation process to occur via their longitudinal movement while also providing resilience to push open the porous membrane 18.

In an embodiment, the constraining arrangement comprises one or more pairs of tubular members corresponding to each drive wire, each pair comprising: a first tubular member having a first lumen and a first distal opening; and a second tubular member having a second lumen a second distal opening, and the drive wire of each pair is threaded through the respective first lumen, forms a protruding loop extending between the respective first distal opening and the respective second distal opening, and is threaded through the respective second lumen. This configuration provides the required functionality efficiently while maintaining a robust and reliable structure.

In an embodiment, the first and second tubular members of each pair are configured to be aligned with each other parallel to a longitudinal axis of the sheath at the distal end when the filter arrangement is in the radially contracted state, and diverge from each other in the distal direction when the porous membrane is in the radially expanded state. This configuration has been found to be particularly simple to implement from a structural perspective while providing efficient switching between the radially contracted and radially expanded states.

In an embodiment, the constraining arrangement comprises a plurality of resilient constraining wires fixedly connected to the sheath and mechanically coupled to the porous membrane; each drive wire is connected to a respective constraining wire in a distal connection region spaced apart from the distal end of the sheath, the connection at the distal connection region being such as to constrain the drive wire to deform in a radially outwards direction when the drive wire is longitudinally advanced out of the sheath and thereby radially expand the porous membrane. The provision of the constraining wires has been found to provide a high degree of flexibility and control over the switching of the porous membrane between the radially contracted and radially expanded states.

In an embodiment, the filter arrangement comprises a plurality of resilient support wires fixedly connected to the sheath and mechanically coupled to the porous membrane; and the filter actuation system comprises a plurality of the drive wires coupled to the support wires and configured such that longitudinal movement of the drive wires drives the plurality of support wires to deform in a manner that radially expands the porous membrane. This configuration has been found to provide a high degree of flexibility and control over the switching of the porous membrane between the radially contracted and radially expanded states using a simple and robust structure. In an embodiment, the plurality of support wires comprises one or more pairs of support wires; the support wires of each pair are fixedly connected to each other at a distal connection region spaced apart from the distal end of the sheath and spaced apart from each other in a deformation region longitudinally between the connection region and the distal end of the sheath. Using support wires in pairs in this manner promotes mechanically balanced and reliable actuation.

In an embodiment, the filter actuation system further comprises a plurality of guiding wires and a corresponding plurality of sliding couplings configured to slide longitudinally along respective guiding wires; and the connection region of each pair of support wires is fixedly connected to the respective sliding coupling such that the longitudinal movement of the drive wire causes a corresponding movement of the sliding coupling and an associated guiding by the guiding wire of the deformation of the pair of support wires. The provision of guiding wires enhances mechanical robustness and promotes reliable and controllable actuation.

In an embodiment, the sheath comprises a tubular body defining the internal lumen, the body having a cross-section profile in which a stiffness of the body varies as a function of azimuthal angle to promote folding inwards of the body in one or more predetermined ranges of azimuthal angle, the body being configured to be more folded inwards in the one or more ranges when the sheath is in the radially contracted state than when the sheath is in the radially expanded state. This configuration provides the required functionality while maintaining reliable operation and a robust structure.

According to an alternative aspect, there is provided a method of providing embolic protection during a transcatheter operation, comprising: inserting an elongate sheath through the vascular system of a subject to bring a distal end of the sheath to a target site in the vascular system, wherein a porous membrane in a radially contracted state extends from the distal end of the sheath during the insertion; switching the porous membrane into a radially expanded state such that the porous membrane spans a cross-section of a blood vessel at the target site to block debris generated upstream from travelling past the porous membrane through the porous membrane while allowing blood to flow past the porous membrane through the porous membrane; switching the sheath from a radially contracted state to a radially expanded state to define a central lumen and inserting a device for performing a transcatheter operation through the central lumen to the target site..

Embodiments of the disclosure will now be further described, merely by way of example, with reference to the accompanying drawings.

Figures 1 and 2 schematically depict features of the human anatomy relevant to apparatus and methods of the present disclosure.

Figure 3 is a perspective view of a distal portion of an apparatus for providing embolic protection having a sheath and a porous membrane in a radially contracted state.

Figure 4 depicts the apparatus of Figure 3 with the porous membrane in a radially expanded state.

Figure 5 depicts deployment of the apparatus of Figures 3 and 4 at a target site in the aortic arch.

Figures 6 to 8 depict example pore structures of the porous membrane 18.

Figures 9 and 10 are front and side views of a single pair of support wires and associated drive wire of the apparatus of Figure 3 in a radially contracted state corresponding to the porous membrane being in the radially contracted state.

Figures 11 and 12 are front and side views of a single pair of support wires and associated drive wire of the apparatus of Figure 3 in a radially expanded state corresponding to the porous membrane being in the radially expanded state.

Figure 13 is an axial end view of the apparatus of Figures 3 and 4 showing support wires in a radially contracted state.

Figure 14 is an axial end view of the apparatus of Figures 3 and 4 showing support wires in a radially expanded state.

Figure 15 is a perspective view of a variation on the apparatus of Figure 3 comprising guiding wires and associated sliding couplings in the radially contracted state.

Figure 16 depicts the apparatus of Figure 15 in a radially expanded state.

Figures 17 and 18 are axial end views of the apparatus of Figures 15 and 16.

Figure 19 is a perspective view of a variation on the apparatus of Figure 3 comprising tubular members and protruding loops of resilient drive wires in a radially contracted state.

Figure 20 depicts the apparatus of Figure 19 in a radially expanded state. Figure 21 is a perspective view of a variation on the apparatus of Figure 3 comprising resilient constraining wires in the radially contracted state.

Figure 22 depicts the apparatus of Figure 21 in a radially expanded state.

Figure 23 is an end view of a sheath in a radially contracted state for use with the apparatus of Figure 3.

Figure 24 is an end view of the sheath of Figure 23 in a radially expanded state.

Figure 25 is an end view of a sheath in a radially contracted state for use with the apparatus of Figures 15 and 16.

Figure 26 is an end view of the sheath of Figure 25 in a radially expanded state.

Figure 27 is an end view of a sheath in a radially contracted state for use with the apparatus of Figures 19 and 20.

Figure 28 is an end view of the sheath of Figure 27 in a radially expanded state.

Figure 29 is an end view of a sheath in a radially contracted state for use with the apparatus of Figures 21 and 22.

Figure 30 is an end view of the sheath of Figure 29 in a radially expanded state.

Figures 31 to 37 depict example method steps in the context of a surgical operation comprising introduction of a prosthetic valve into a subject’s native aortic valve.

Figures 38 and 39 depict example configurations for an self-sealing inlet arrangement for allowing lateral access into the sheath 12 for a catheter, such as a contrast catheter.

The present disclosure relates to methods and apparatus 10 for providing embolic protection during a transcatheter operation. The transcatheter operation may comprise any cardiac operation that may generate potentially problematic (e.g., embolism causing) debris, including for example deployment of a prosthesis such as an aortic valve prosthesis or aortic valve valvuloplasty.

Figures 1 and 2 depict relevant features of the human anatomy. Figures 3 and 4 depict an example apparatus 10. The apparatus 10 comprises an elongate sheath 12. Only a distal portion of the sheath 12 is shown in Figures 3 and 4. The sheath 12 is insertable through the vascular system of a subject to bring a distal end 14 of the sheath 12 to a target site 3 in the vascular system. The target site 3 may be in the aorta. Referring to Figure 1, the sheath 12 may, for example, be inserted via transfemoral access 1 through the descending aorta 2 to a target site 3 in, or in the vicinity of, the aortic arch 4 above the heart 5. The target site 3 may be adjacent to arteries 6, including the brachiocephalic artery, left common carotid artery and left subclavian artery. The sheath 12 may thus be sufficiently long to extend for example from the upstream iliac bifurcation of the abdominal aorta to the aortic arch.

The apparatus 10 comprises a filter arrangement 16. The filter arrangement 16 is configured to extend from the distal end 14 of the sheath 12. In some arrangements, the filter arrangement 16 is attached, for example rigidly attached, to the distal end 14 of the sheath 12.

The filter arrangement 16 comprises a porous membrane 18. The porous member 18 is switchable between a radially contracted state and a radially expanded state. The filter arrangement 16 is thus configured to allow switching of the porous membrane 18 between the radially contracted state and the radially expanded state.

Figure 3 depicts the porous membrane 18 in the radially contracted state. In an arrangement, the radially contracted state is such as to allow the sheath 12 and the filter arrangement 16 to be inserted through the vascular system (e.g., from the transfemoral access 1 to the target site 3 in the aortic arch 4) while the porous membrane 18 is in the radially contracted state.

Figure 4 depicts the porous membrane 18 in the radially expanded state. The radially expanded state may be such as to span a cross-section of a blood vessel at the target site 3 to block debris generated upstream, for example by a transcatheter operation, from travelling past the porous membrane 18 through the porous membrane 18 (i.e., through pores of the porous membrane 18) while allowing blood to flow past the porous membrane 18 through the porous membrane 18 (i.e., through pores of the porous membrane 18).

Figure 5 schematically depicts a distal portion of the apparatus 10 deployed in the aortic arch. In this example, debris generated below the distal end of the porous membrane 18 in the left part of the figure will be prevented by the porous membrane 18 from being carried past the porous membrane 18 into any of the arteries 6 or down the descending aorta 2. The porous membrane 18 may be in contact with the adjacent walls, optionally continuously along a closed loop path, and/or press radially outwardly against the walls to minimise or remove any path past the porous membrane 18 that does not involve passing through the porous membrane 18 (e.g., through pores in the porous membrane 18). The porous membrane 18 in the radially expanded state may have a frusto-conical form or similar, with an opening at the distal end that is larger than an opening at a proximal end.

The porous membrane 18 may take various forms. The porous membrane 18 may for example comprise a porous mesh material such as a fabric of knitted, braided, woven, or nonwoven fibres, filaments, or wires. The porous membrane 18 may comprise pores 19. Sizes of the pores 19 may be chosen to prevent emboli over a predetermined size from passing through the pores 19. In some arrangements, a pore size of at least a subset of the pores 19 is in the range of about 50-250 pm when the porous membrane 18 is in the radially expanded state. The pores 19 may be sized to allow other catheters, such as a contrast catheter, to pass through the pores 19, for example from the brachiocephalic artery, left common carotid artery, or left subclavian artery. Example pore structures for the porous membrane 18 are depicted in Figures 6-8.

In some arrangements, the porous membrane 18 is configured to be resilient. The porous membrane 18 may comprise a fabric made of a resilient metal, a polymer material, a malleable material, a plastically deformable material, a shape-memory material, or combinations thereof. In some arrangements, the porous membrane 18 comprises an anti- thrombogenic coating. The porous membrane 18 may be configured to form folds, for example by being pleated, when in the radially contracted state. The pleats may be longitudinal pleats.

When it is time to withdraw the apparatus 10, the porous membrane 18 can be switched back into the radially contracted state. Any debris collected in the porous membrane 18 is retained safely in the porous membrane 18 and can be removed from the body along with the porous membrane 18.

The apparatus 10 comprises a filter actuation system configured to switch the porous membrane 18 between the radially contracted state and the radially expanded state.

In some arrangements, the filter actuation system comprises one or more drive wires 21 extending through the sheath 12 and out of the distal end 14 of the sheath 12. The filter actuation system is configured such that longitudinal movement of the drive wires 21 contributes to or causes the switching of the porous membrane 18 between the radially contracted state and the radially expanded state.

A single drive wire 21 or each of one or more drive wires 21 may extend along the whole or a majority of the length of the sheath 12. The drive wire 21 may for example be configured such that the drive wire 21 can be driven (e.g., to move longitudinally) from outside of the subject while the distal end 14 of the sheath 12 is at the target site 3. The drive wire 21 may for example extend from the proximal end of the sheath 12 to the target site 3. The or each drive wire 21 may extend beyond the distal end 14 of the sheath 12. A portion (which may be referred to as an “extending portion”) of each drive wire 21 that extends beyond the distal end 14 may have a length in the range of about 50mm to about 150mm.

In some arrangements, including the example of Figures 3 and 4, the filter arrangement comprises a plurality of resilient support wires 22 fixedly connected to the sheath 12 (e.g., embedded within the sheath 12) and mechanically coupled to the porous membrane 18. Each of one or more of the support wires 22 and/or drive wires 21 may, for example, be provided radially inwardly of the porous membrane 18 such that radial expansion of the support wires 22 (e.g., splaying outwards) mechanically pushes the porous membrane 18 outwards from the inside (e.g., into a cone-like shape). Alternatively, each of one or more of the support wires 22 and/or drive wires 21 may be provided radially outside of the porous membrane 18 but mechanically connected thereto such that radial expansion of the support wires 22 (e.g., splaying outwards) pulls the porous membrane 18 outwards from the outside (e.g., into a cone-like shape).

In such arrangements, the filter actuation system comprises a plurality of the drive wires 21 coupled to the support wires 22 and configured such that longitudinal movement of the drive wires 21 drives the plurality of support wires 22 to deform (e.g., bend, for example as shown in Figure 4) in a manner that radially expands the porous membrane 18.

In an arrangement, the plurality of support wires 22 comprises one or more pairs of support wires 22. In the example shown in Figures 3 and 4, the filter actuation system comprises three pairs of support wires 22 and three respective drive wires 21. Figures 9 to 12 depict one of the pairs of support wires 22 and the associated drive wire 21 of the apparatus of Figure 3 to illustrate how each pair of support wires 22 operates. Figures 9 and 10 are front and side views showing the support wires 22 in a radially contracted state corresponding to the porous membrane 18 being in the radially contracted state. Figures 11 and 12 are front and side views showing the support wires 22 in a radially expanded state corresponding to the porous membrane 18 being in the radially expanded state.

The support wires 22 of each pair are fixedly connected to each other at a distal connection region 24. The distal connection region 24 is spaced apart from the distal end 14 of the sheath 12. The support wires 22 of each pair are spaced apart from each other in a deformation region 26. The deformation region 26 is longitudinally between the connection region 24 and the distal end 14 of the sheath 12. The plurality of drive wires 21 comprises a drive wire 21 connected to the connection region 24 of each pair of support wires 22. Each pair of support wires 22 is configured such that longitudinal movement of the drive wire 21 connected to the connection region 24 of the pair causes radially outward deformation of the pair of support wires 22. As an example, the transition from the state shown in Figures 9 and 10 to the state shown in Figures 11 and 12 may be achieved by pulling the drive wire 21 downwards (i.e., in a longitudinally proximal direction). This causes the support wires 22 to bend over towards the left in the orientation shown in Figure 12. Where a plurality of pairs are configured in this manner and positioned at different angular locations around the axis of the sheath (e.g., in three azimuthal angular ranges centred at locations that are 120 degrees apart in the example of Figures 3 and 4), the deformation of the support wires 22 can radially expand the porous membrane 18 (for example to splay outwards) and thereby span appropriately across a blood vessel.

Figures 13 and 14 are axial end views showing example radial expansion of the support wires 22 of Figures 3 and 4 achieved by pulling drive wires 21 to deform the three pairs of support wires 22. In Figure 13, the sheath 12 is in the radially contracted state (in this case forming a threefold symmetric S-shape) with the drive wires 21 and the support wires 22 straight. In Figure 14, the sheath 12 is in the radially expanded state, with the drive wires 21 and support wires 22 bent and pointing outwards under tension. The drive wires 21 may be pulled simultaneously and/or by the same amount, thereby achieving azimuthally uniform expansion of the porous membrane 18. Alternatively, two or more of the drive wires 21 may be pulled differently in order to expand the porous membrane 18 less symmetrically, for example to achieve a better fit within a curved portion of the subject’s anatomy. Figures 15 to 18 depict a variation on the apparatus 10 of Figures 3, 4 and 9 to 14 in which the filter actuation system further comprises a plurality of guiding wires 28 and a corresponding plurality of sliding couplings 30 configured to each slide longitudinally along respective guiding wires 28. In the example shown, there are three guiding wires 28 and three corresponding sliding couplings 30 (one sliding coupling 30 for each guiding wire 28). The connection region of each pair of support wires 22 is fixedly connected to the respective sliding coupling 30 such that the longitudinal movement of the drive wire 21 (e.g., downwards in the orientation shown in Figures 15 and 16) causes a corresponding movement of the sliding coupling 30 and an associated guiding by the guiding wire 28 of the deformation of the pair of support wires 22.

In some arrangements, each of one or more of the drive wires 21 is a resilient drive wire 21 mechanically coupled, directly or indirectly, to the porous membrane 18. In such arrangements, the filter arrangement may comprise a constraining arrangement configured to constrain the resilient drive wire 21 such that the longitudinal movement of the resilient drive wire 21 causes the resilient drive wire 21 to deform in a manner that radially expands the porous membrane 18. Examples of such arrangements are shown in Figures 19-22.

In some arrangements, as exemplified in Figures 19 and 20, the resilient drive wires 21 are configured such that portions of the drive wires 21 extending beyond the distal end 14 of the sheath 12 are substantially aligned with each other parallel to a longitudinal axis of the sheath 12 at the distal end when the porous membrane 18 is in the radially contracted state, and diverge from each other in the distal direction (i.e., such that a separation between them increases as a function of distance from the distal end 14 of the sheath 12) when the porous membrane 18 is in the radially expanded state.

In some arrangements, as shown in Figures 19 and 20, the constraining arrangement comprises one or more pairs of tubular members 32 corresponding to each drive wire 21. Each pair of tubular members 32 comprises a first tubular member and a second tubular member. The first and second tubular members can be selected arbitrarily and may be identical to each other. An example of a first tubular member is labelled 32A in Figures 19 and 20. The first tubular member 32 A has a first lumen and a first distal opening 34A. An example of a second tubular member is labelled 32B in Figures 19 and 20. The second tubular member 32B has a second lumen a second distal opening 34B. The drive wire 21 of each pair is threaded through the respective first lumen (e.g., through the first tubular member 32A), forms a protruding loop 36 extending between the respective first distal opening 34A and the respective second distal opening 34B, and is threaded through the respective second lumen (e.g., through the second tubular member 32B). In the example of Figures 19 and 20, three pairs of tubular members 32 can be identified, each with a single protruding loop 36 extending between the tubular members 32 of the pair. In the example shown, each pair shares its tubular members with azimuthally neighbouring pairs (such that the total number of tubular members 32 is equal to the total number of pairs of tubular members 32) but this is not essential.

The tubular members 32 and drive wires 21 are configured such that displacing a drive wire 21 longitudinally in the distal direction (e.g., pushing the drive wire 21 in the distal direction) causes an increase in the length of the protruding loop 36. The increase in length of the protruding loop 36 (and the resilient nature of the drive wire 21 forming the protruding loop 36) forces apart portions of the drive wire 21 within the tubular members 32, thereby deforming the drive wire 21 in a manner that radially expands the porous membrane 18. In some arrangements, the first and second tubular members 32 A, 32B of each pair are configured to be aligned with each other parallel to a longitudinal axis of the sheath 12 at the distal end 14 when the filter arrangement is in the radially contracted state, and diverge from each other in the distal direction (i.e., such that a separation between them increases as a function of distance from the distal end 14 of the sheath 12) when the porous membrane 18 is in the radially expanded state. In the examples of Figures 19 and 20, it can be seen that the three protruding loops 36 are relatively short in Figure 19, with the tubular members 32 aligned in the axial direction of the sheath 12, and are relatively long in Figure 20, with the tubular members 32 pushed apart by the resilience of the drive wires 21 in the protruding loops 36 so as to radially diverge (splay outwards).

In some arrangements, as exemplified in Figures 21 and 22, the constraining arrangement comprises a plurality of resilient constraining wires 38 fixedly connected to the sheath 12 and mechanically coupled to the porous membrane 18. In the example of Figures 21 and 22 the constraining wires 38 are substantially linear but other shapes could be used. Each drive wire 21 is connected to a respective constraining wire 38 in a distal connection region 40 spaced apart from the distal end 14 of the sheath 12. The connection at the distal connection region 40 is such as to constrain the drive wire 21 to deform in a radially outwards direction when the drive wire 21 is longitudinally advanced out of the sheath 12 and thereby radially expand the porous membrane 18. Advancing each drive wire 21 distally increases a length of a portion of the guide wire 21 between the sheath 12 and the connection region 40. The resilience of the guide wire 21 forces the connection region 40 and the porous membrane 18 radially outwards. In some arrangements, as exemplified in Figures 21 and 22, the constraining wires 38 are configured to be aligned with each other parallel to a longitudinal axis of the sheath 12 at the distal end (e.g., as shown in Figure 21) when the porous membrane 18 is in the radially contracted state and to radially diverge in the distal direction (as shown in Figure 22) when the porous membrane 18 is in the radially expanded state.

In any of the arrangements described above and/or in other arrangements, the elongate sheath 12 may be switchable between a radially contracted state and a radially expanded state. Examples of such radially contracted and radially expanded states are shown in Figures 23-30. The sheath 12 may comprise any suitable material for achieving the required functionality and biocompatibility, such as FEP, PTFE, polyimide, polyamide, polyethylene, polypropylene, polyurethane, silicone elastomer, C-Flex, and/or latex rubber. In some arrangements, the sheath 12 comprises reinforcement, such as coils, stents or expandable rings. The reinforcement may assist with maintaining a shape of the sheath 12 during radial expansion and contraction.

The sheath 12 in the radially contracted state may define a central lumen 44 that is relatively small in cross-section. This allows an overall outer dimension of the sheath 12 to be relatively small, thus facilitating insertion and advancement of the sheath 12 into a subject and through the vascular system to a target site 3. The central lumen 44 may, however, be large enough to accommodate a guide wire even when the sheath 12 is in the radially contracted state. The sheath 12 in the radially expanded state may define a central lumen 44 that is significantly larger. The larger central lumen 44 may be suitable, for example, to allow insertion of a device through the central lumen 44 to the target site 3 for performing a transcatheter operation. For example, the sheath 12 may be configured to have an outer cross-sectional diameter in the radially contracted state (twice the radius Rf) that is smaller than an inner diameter (twice the radius R_e) of the central lumen 44 (e.g., a radius) in the radially expanded state.

The porous membrane 18 in the radially expanded state may comprises a proximal opening leading to the central lumen 44 and a distal opening that is larger than the proximal opening. The central lumen 44 thus opens out distally into a region within the porous membrane 18 (e.g., within the cone-like shape defined by the porous membrane 18).

The sheath 12 may be configured to self-expand from the radially contracted state to the radially expanded state. Alternatively or additionally, the sheath 12 may be configured to be expanded by longitudinal movement through the sheath 12 of the device for performing the transcatheter operation. As depicted in Figures 23-30, the sheath 12 may comprise a tubular body 46 defining the internal lumen 44. The body 46 may have a cross-sectional profile in which a stiffness of the body 46 varies as a function of azimuthal angle to promote folding inwards of the body 46 in one or more predetermined ranges of azimuthal angle. The body 46 may be configured to be more folded inwards in the one or more ranges when the sheath 12 is in the radially contracted state than when the sheath 12 is in the radially expanded state. The variation of the stiffness of the body 34 with azimuthal angle may at least partially be defined by a corresponding variation in radial thickness of the body 46 with azimuthal angle.

In the examples shown in Figures 23-30, the body 46 is configured to fold inwards in three azimuthal regions to form three respective folds 48 when the sheath 12 is in the radially contracted state (Figures 23, 25, 27 and 29). The radial thickness of the body 46 of the sheath 12 can be seen to be smaller in each of the three azimuthal regions corresponding to the folds 48 than elsewhere around the circumference of the sheath 12. For example, the radial thickness of the wall portions labelled 46 A corresponding to the folds 48 can be seen to be smaller than the radial thickness of the walls portions labelled 46B that do not fold inwards.

The sheath 12 defines one or more peripheral lumens 50 formed in the body 46 outside of the central lumen 44. The central lumen 44 contains the longitudinal axis of the sheath 12 whereas the peripheral lumens are located laterally outside of the axis and do not contain the axis. The peripheral lumens 50 may be blind (i.e., have an opening only at one end) or continuous (i.e., having an opening at both ends, for example at the proximal and distal ends of the sheath 12). The peripheral lumens 50 may be configured to accommodate respective drive wires 21, support wires 22, guiding wires 28, tubular members 32, and/or constraining wires 38. In the example of Figures 23 and 24, the sheath 12 may comprise peripheral lumens 50A for drive wires 21 and 50B for support wires 22. In the example of Figures 25 and 26, the sheath 12 may comprise peripheral lumens 50A for drive wires 21, 50B for support wires 22, and 50C for guiding wires 28. In the example of Figures 27 and 28, the sheath 12 may comprise peripheral lumens 50D for tubular members 32. In the example of Figures 29 and 30, the sheath 12 may comprise peripheral lumens 50A for drive wires 21 and 50E for constraining wires 38.

Any of the apparatus arrangements disclosed herein may be used in a method of providing embolic protection during a surgical operation. The method may comprise inserting an elongate sheath 12 through the vascular system of a subject to bring a distal end 14 of the sheath 12 to a target site 3 in the vascular system. A porous membrane 18 in a radially contracted state may extend from the distal end 14 of the sheath 12 during the insertion. The method comprises switching the porous membrane 18 into a radially expanded state such that the porous membrane 18 spans a cross-section of a blood vessel at the target site 3 to block debris generated upstream from travelling past the porous membrane 18 through the porous membrane 18 while allowing blood to flow past the porous membrane 18 through the porous membrane 18. The switching of the porous membrane 18 from the radially contracted state to the radially expanded state may be performed using any of the apparatus elements and techniques discussed above. The method may further comprise switching the sheath 12 from a radially contracted state to a radially expanded state to define a central lumen 44 and inserting a device for performing the transcatheter operation through the central lumen 44 to the target site 3. The method may further comprise performing the transcatheter operation using the device while the porous membrane 18 is in the radially expanded state. The method may further comprise trapping debris generated by the transcatheter operation in the porous membrane 18 by switching the porous membrane 18 from the radially expanded state to the radially contracted state after the performing of the transcatheter operation. The sheath 12 and porous membrane 18 may subsequently be withdrawn from the subject. Example method steps are depicted in Figures 31-37 in the context of a surgical operation comprising introduction of a prosthetic valve 64 into a subject’s native aortic valve.

Figure 31 schematically depicts the relevant region of the aortic arch and surrounding blood vessels before introduction of the apparatus 10.

In a first step of the method, as depicted in Figure 32, the apparatus 10 is introduced from a transfemoral access and advanced to a target position with the filter arrangement 16 and associated porous membrane 18 in the ascending aorta. An introducer 60 with a tapered tip may be advanced through a central lumen 44 of the sheath 12 to protrude ahead of the filter arrangement 16 during the insertion process to make the insertion process smoother.

In a subsequent step, as depicted in Figure 33, the introducer 60 is removed and the porous membrane 18 is switched from the radially contracted state to the radially expanded state to span across the blood vessel.

In a subsequent step, as depicted in Figure 34, a device 62 for performing a transcatheter operation, in this case installation of a prosthetic valve 64, is inserted through the central lumen 44 of the sheath 12 to the target site. The device 62 expands the central lumen 44 as it is pushed along the central lumen 44, thereby switching the sheath 12 into a radially expanded state.

In a subsequent step, as depicted in Figure 35, the device 62 installs the prosthetic valve 64 in the aortic valve. A contrast catheter may be used to inject a contrast agent into the target site to assist visualisation (e.g., via an inlet arrangement 66 as discussed below with reference to Figures 38 and 39), for example to facilitate observation of a position of the valve. The device 62 is withdrawn and the sheath 12 folds back into the radially contracted state due to elasticity.

In a subsequent step, as depicted in Figure 36 and 37, the porous membrane 18 is switched back into the radially contracted state ready for removal of the apparatus 10 from the aorta. During this process, debris particles collected inside the porous membrane 18 during the installation of the prosthetic valve 64 may be trapped in the porous membrane 18. The debris particles can thus be safely removed from the subject when the apparatus 10 is removed. In some arrangements, as depicted in Figures 38 and 39, the sheath 12 comprises a self-sealing inlet arrangement 66. The inlet arrangement 66 is provided at an intermediate location between a proximal end of the sheath 12 and the distal end 14 of the sheath 12. The inlet arrangement 66 is configured to allow insertion of a catheter, such as a contrast catheter 68, into the sheath 12 through the inlet arrangement 66 when the distal end 14 of the sheath 12 is at the target site in the vascular system. The intermediate location can be in various places, for example in a region of the transfemoral artery 70 or in a region of the left subclavian artery 80 (as depicted in Figure 38). In an arrangement, the inlet arrangement 66 comprises a flexible membrane 76 and a plurality of cuts 78 formed in the membrane 76. Each cut 78 may be configured to allow a catheter to be inserted into the sheath 12 through the cut 78 and to self-seal when the catheter is withdrawn from the sheath 12. The selfsealing of the inlet arrangement may prevent debris that has entered the sheath 12 (e.g., generated from a transcatheter operation) from leaking out.

In an arrangement, the inlet arrangement 66 comprises six inlet sub-sections distributed circumferentially in three groups of two. Figure 38 (left) shows one of the groups (consisting of inlet sub-sections 74A and 74B) in a sectional view. Each inlet sub-section comprises a portion of the flexible membrane 76 and cuts 78.

The flexible membrane 76 can comprise any suitable material, including for example thin PTFE, polyimide, polyamide, polyethylene, polyurethane, and/or silicone elastomer. In some arrangements, the flexible membrane 76 is formed from the same material as the sheath 12 but with a smaller thickness to increase the flexibility. A plurality of the cuts 78 may be provided in the flexible membrane 76 to make it easier to find a cut 78 when inserting a catheter 68. A catheter to be inserted can be inserted through any of the cuts 78. Various shapes of cut 78 can be used, including for example a cross (as depicted), asterisk, and/or star. The cuts 78 may be configured to be closed in their relaxed (natural) states to provide the self-sealing functionality. The cuts 78 may thus define resilient folds that are biased towards as state in which the folds fit flushly against each other and prevent debris from passing through any of the cuts 78.

Claims

1. An apparatus for providing embolic protection during a transcatheter operation, the apparatus comprising: an elongate sheath insertable through the vascular system of a subject to bring a distal end of the sheath to a target site in the vascular system; and a filter arrangement configured to extend from the distal end of the sheath, wherein: the elongate sheath is switchable between a radially contracted state and a radially expanded state, wherein the sheath in the radially expanded state defines a central lumen for allowing insertion to the target site, through the central lumen, of a device for performing a transcatheter operation; the filter arrangement comprises a porous membrane switchable between a radially contracted state and a radially expanded state, wherein the radially expanded state is such as to span a cross-section of a blood vessel at the target site to block debris generated upstream from travelling past the porous membrane through the porous membrane while allowing blood to flow past the porous membrane through the porous membrane; and a filter actuation system configured to switch the porous membrane between the radially contracted state and the radially expanded state.

2. The apparatus of claim 1, wherein the target site is in within the aorta of the subject.

3. The apparatus of claim 1 or 2, wherein the transcatheter operation comprises a cardiac operation associated with generation of debris, optionally deployment of a prosthesis such as an aortic valve prosthesis or aortic valve valvuloplasty.

4. The apparatus of any of claims 1 to 3, wherein the sheath is configured to selfexpand and/or is configured to be expanded by longitudinal movement through the sheath of the device for performing the transcatheter operation.

5. The apparatus of any preceding claim, wherein: the filter actuation system comprises one or more drive wires extending through the sheath and out of the distal end of the sheath; and the filter actuation system is configured such that longitudinal movement of the drive wires contributes to or causes the switching of the porous membrane between the radially contracted state and the radially expanded state.

6. The apparatus of claim 5, wherein: each of one or more of the drive wires is a resilient drive wire mechanically coupled, directly or indirectly, to the porous membrane; and the filter arrangement comprises a constraining arrangement configured to constrain the resilient drive wire such that the longitudinal movement of the resilient drive wire causes the resilient drive wire to deform in a manner that radially expands the porous membrane.

7. The apparatus of claim 6, wherein the resilient drive wires are configured such that portions of the drive wires extending beyond the distal end of the sheath are substantially aligned with each other parallel to a longitudinal axis of the sheath at the distal end when the porous membrane is in the radially contracted state, and diverge from each other in the distal direction when the porous membrane is in the radially expanded state.

8. The apparatus of claim 6 or 7, wherein: the constraining arrangement comprises one or more pairs of tubular members corresponding to each drive wire, each pair comprising: a first tubular member having a first lumen and a first distal opening; and a second tubular member having a second lumen a second distal opening, the drive wire of each pair is threaded through the respective first lumen, forms a protruding loop extending between the respective first distal opening and the respective second distal opening, and is threaded through the respective second lumen, and the apparatus is configured such that displacing the drive wire longitudinally in the distal direction causes an increase in the length of the protruding loop, the increase in length forcing apart portions of the drive wire within the tubular members, thereby deforming the drive wire in a manner that radially expands the porous membrane.

9. The apparatus of claim 8, wherein the first and second tubular members of each pair are configured to be aligned with each other parallel to a longitudinal axis of the sheath at the distal end when the filter arrangement is in the radially contracted state, and diverge from each other in the distal direction when the porous membrane is in the radially expanded state.

10. The apparatus of claim 6, wherein: the constraining arrangement comprises a plurality of resilient constraining wires fixedly connected to the sheath and mechanically coupled to the porous membrane; each drive wire is connected to a respective constraining wire in a distal connection region spaced apart from the distal end of the sheath, the connection at the distal connection region being such as to constrain the drive wire to deform in a radially outwards direction when the drive wire is longitudinally advanced out of the sheath and thereby radially expand the porous membrane.

11. The apparatus of claim 10, wherein the constraining wires are configured to be aligned with each other parallel to a longitudinal axis of the sheath at the distal end when the porous membrane is in the radially contracted state and to radially diverge in the distal direction when the porous membrane is in the radially expanded state.

12. The apparatus of claim 5, wherein: the filter arrangement comprises a plurality of resilient support wires fixedly connected to the sheath and mechanically coupled to the porous membrane; and the filter actuation system comprises a plurality of the drive wires coupled to the support wires and configured such that longitudinal movement of the drive wires drives the plurality of support wires to deform in a manner that radially expands the porous membrane.

13. The apparatus of claim 12, wherein: the plurality of support wires comprises one or more pairs of support wires; the support wires of each pair are fixedly connected to each other at a distal connection region spaced apart from the distal end of the sheath and spaced apart from each other in a deformation region longitudinally between the connection region and the distal end of the sheath.

14. The apparatus of claim 13, wherein: the plurality of drive wires comprises a drive wire connected to the connection region of each pair of support wires; and each pair of support wires is configured such that longitudinal movement of the drive wire connected to the connection region of the pair causes radially outward deformation of the pair of support wires.

15. The apparatus of claim 14, wherein: the filter actuation system further comprises a plurality of guiding wires and a corresponding plurality of sliding couplings configured to slide longitudinally along respective guiding wires; and the connection region of each pair of support wires is fixedly connected to the respective sliding coupling such that the longitudinal movement of the drive wire causes a corresponding movement of the sliding coupling and an associated guiding by the guiding wire of the deformation of the pair of support wires.

16. The apparatus of any preceding claim, wherein the sheath comprises a tubular body defining the internal lumen, the body having a cross-section profile in which a stiffness of the body varies as a function of azimuthal angle to promote folding inwards of the body in one or more predetermined ranges of azimuthal angle, the body being configured to be more folded inwards in the one or more ranges when the sheath is in the radially contracted state than when the sheath is in the radially expanded state.

17. The apparatus of claim 16, wherein the variation of the stiffness of the body with azimuthal angle is at least partially defined by a corresponding variation in radial thickness of the body with azimuthal angle.

18. The apparatus of claim 16 or 17, wherein the sheath defines one or more peripheral lumens formed in the body outside of the central lumen, the peripheral lumens being configured to accommodate respective drive wires, support wires, guiding wires, tubular members, and/or constraining wires.

19. The apparatus of any preceding claim, wherein the sheath comprises a self-sealing inlet arrangement at an intermediate location between a proximal end of the sheath and the distal end of the sheath, the inlet arrangement being configured to allow insertion of a catheter into the sheath through the inlet arrangement when the distal end of the sheath is at the target site in the vascular system.

20. The apparatus of claim 19, wherein the inlet arrangement comprises a flexible membrane and a plurality of cuts formed in the membrane, each cut being configured to allow a catheter to be inserted into the sheath through the cut and to self-seal when the catheter is withdrawn from the sheath.

21. The apparatus of preceding claim, wherein an outer diameter of the sheath in the radially contracted state is less than an inner diameter of the central lumen in the radially expanded state.

22. A method of providing embolic protection during a transcatheter operation, comprising: inserting an elongate sheath through the vascular system of a subject to bring a distal end of the sheath to a target site in the vascular system, wherein a porous membrane in a radially contracted state extends from the distal end of the sheath during the insertion; switching the porous membrane into a radially expanded state such that the porous membrane spans a cross-section of a blood vessel at the target site to block debris generated upstream from travelling past the porous membrane through the porous membrane while allowing blood to flow past the porous membrane through the porous membrane; switching the sheath from a radially contracted state to a radially expanded state to define a central lumen and inserting a device for performing a transcatheter operation through the central lumen to the target site.

23. The method of claim 22, further comprising performing the transcatheter operation using the device while the porous membrane is in the radially expanded state.

24. The method of claim 23, further comprising: trapping debris generated by the transcatheter operation in the porous membrane by switching the porous membrane from the radially expanded state to the radially contracted state after the performing of the transcatheter operation; and withdrawing the sheath and porous membrane from the subject.