Preloaded Catheter And Clot Retrieval Systems And Methods For Treatment Of Ischemic Stroke

Abstract

The invention describes systems and methods for retrieving blood clots (thrombi) from patients undergoing endovascular/neurointervention procedures following ischemic stroke. More specifically, a preloaded catheter and clot retrieval system (PCS) effective in positioning a clot retrieval system (CRS) or stent adjacent a clot and ensnaring and removing the clot are described as well as methods of utilizing these devices.

Claims

1. A preloaded catheter system (PCS) for carrying a stent within a vasculature to a deployment site comprising: an outer catheter system (OCS) having a distal tip section having a distal lumen diameter for operative containment of a microwire; a stent holding section proximal to the distal tip section, the stent holding section having a lumen volume and diameter for reversibly retaining a compressible wire stent and enabling operative use of a microwire through the stent holding section; a proximal section having a proximal lumen diameter for operative containment of a microwire; a stent operatively retained within the stent holding section; where the microwire includes a microwire lock adjacent a distal tip of the microwire and where the microwire lock is operatively engageable with a stent lock adjacent a proximal end of the stent; and where the microwire lock and the stent lock are engageable through application of a proximal pressure applied to the microwire and where, once engaged, application of a distal pressure enables deployment of the stent from the distal tip of the OCS.

2. The system as in claim 1 where the OCS includes a distal outer surface taper between the distal tip section and stent holding section.

3. The system as in claim 1 where the OCS includes a proximal outer surface taper between the proximal section and the stent holding section.

4. The system as in claim 2 where the distal outer tapered surface has dimensions to facilitate advancement of the OCS and a distal access catheter (DAC) through a tortuous section of a human vasculature.

5. The system as in claim 2 where the proximal outer tapered surface has outer dimensions to facilitate advancement of a distal access catheter (DAC) through a tortuous section of a human vasculature without separation of a distal tip of the DAC from an outer surface of the stent holding section.

6. The system as in claim 1 where the stent is a clot retrieval stent.

7. The system as in claim 6 where the stent includes a plurality of wire frame openings defining separate zones and where each zone has wire frame openings of a different average diameter.

8. A stent for operative deployment from a preloaded catheter system as in claim 1 comprising: a compressible wire body expandable within the stent holding section, the wire body defining a plurality of wire openings; a proximal stent lock engageable with a corresponding microwire lock; where prior to engagement, the proximal stent lock enables operative movement of a microwire within the stent holding section; and, where after engagement of the stent lock with microwire lock, the stent is deployable in distal direction from the stent holding section.

9. The stent as in claim 8 where the stent lock includes a hollow ring enabling operative containment of a microwire within the hollow ring and where the hollow ring includes at least one surface for locking engagement with the microwire lock.

10. A microwire for operative use within an outer catheter system (OCS) as described in claim 1 comprising: a microwire body having a distal tip; a microwire lock adjacent the distal tip for engagement with a stent lock; wherein the microwire lock has dimensions for operative movement within the OCS.

11. A lock system for locking a microwire to a stent comprising: a microwire lock operatively connected to a microwire adjacent a distal tip of the microwire, the microwire lock having at least one microwire locking surface; a stent lock operatively connected to a proximal end of an expandable stent, the stent lock including a ring surrounding a microwire and having at least one stent locking surface for engagement with the at least one microwire locking surface; and where the microwire lock and stent lock are engageable by application of a proximal pressure to the microwire lock to draw the at least one microwire locking surface into the ring to engage the at least one microwire locking surface with the at least one stent locking surface.

12. A method of conveying a stent through a vasculature from an entry point to a deployment site utilizing a preloaded catheter system (PCS) having: a distal tip section having a distal lumen diameter for operative containment of a microwire; a stent holding section proximal to the distal tip section, the stent holding section having a lumen volume and diameter for reversibly retaining a compressible wire stent and enabling operative use of a microwire through the stent holding section; a proximal section having a proximal lumen diameter for operative containment of a microwire; a stent operatively retained within the stent holding section; where the microwire includes a microwire lock adjacent a distal tip of the microwire and where the microwire lock is operatively engageable with a stent lock adjacent a proximal end of the stent and where the microwire lock and the stent lock are engageable through application of a proximal pressure applied to the microwire and where, once engaged, application of a distal pressure enables deployment of the stent from the distal tip of the OCS, the method comprising the steps of: a. introducing the PCS into the vasculature; b. successively advancing the microwire and OCS through the vasculature to a deployment site; c. partially withdrawing the MW proximally to engage the MW lock with the stent lock; and, d. deploying the stent by withdrawing the OCS relative to the stent to effect deployment of the stent from the distal tip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention; however, the scale of the drawings may be relied upon for supporting the relative position of described components with respect to one another. Similar reference numerals indicate similar components.

[0052] FIG. 1A is a schematic sketch of a portion of brain vascular anatomy showing the ophthalmic artery (OA), intracranial internal carotid artery (IICA), anterior cerebral artery (ACA), M1 segment of the middle cerebral artery and M2 segment of the middle cerebral artery.

[0053] FIGS. 1B and 1C are schematic sketches as in FIG. 1A showing a stent device entangled with and withdrawing a clot; FIG. 1C shows a common issue of a stent dropping a clot when negotiating a tortuous region of the cerebral anatomy.

[0054] FIG. 2 is a schematic diagram of a catheter system in accordance with the prior art where the catheter system has an expanded tapered section adjacent the distal tip to assist in negotiating tortuous regions of the cerebral anatomy.

[0055] FIG. 3 is a schematic diagram in accordance with the invention showing a preloaded catheter system (PRS).

[0056] FIG. 3A is a schematic diagram in accordance with the invention showing a preloaded catheter system with the stent lock engaged.

[0057] FIG. 3B is a schematic diagram in accordance with the invention showing a preloaded catheter system with the stent lock engaged and partially emerged from the distal tip of the PRS.

[0058] FIG. 3C is a schematic diagram in accordance with the invention showing a preloaded catheter system with the stent lock engaged and emerged from the distal tip of the PRS.

DETAILED DESCRIPTION OF THE INVENTION

5. Introduction

[0059] With reference to the figures, systems and methods for retrieving blood clots via endovascular intervention are described. More specifically, systems adapted for advancing and deploying stents within a patient's vasculature following ischemic stroke are described.

[0060] FIG. 1A is a schematic diagram of brain vascular anatomy showing the intracranial internal carotid artery (IICA), anterior cerebral artery (ACA), M1 segment of the middle cerebral artery and M2 segment of the middle cerebral artery. A clot Y is shown within the M1 MCA with arrow 12 showing the direction of blood flow prior to any procedure. FIG. 1A also shows a tortuous region (e.g. the ophthalmic artery (OA)) which is a region that can be difficult both to advance and withdraw catheter systems through.

[0061] FIG. 1B illustrates a simplified example of a surgeon withdrawing a stent 13 that has entangled clot Y. For the purposes of illustration, the stent 13 may be flattened as it is drawn through a tortuous section resulting in the partial or complete release of the clot Y (FIG. 10) as the wires of the stent move with respect to one another thus changing/enlarging the stent openings.

[0062] FIG. 2 shows a catheter system in accordance with the prior art and described in US patent application Ser. No. 14/809,867, incorporated herein by reference. As shown, this catheter system 10 includes a distal tip section 12, an expanded section 14 and a proximal support section 16. The catheter system may include a distal access catheter 18 where a middle portion 14b has a diameter that fits into and supports a distal end 18a of the DAC.

[0063] Various aspects of the invention will now be described with reference to the figures. For the purposes of illustration, components depicted in the figures are not necessarily drawn to scale. Instead, emphasis is placed on highlighting the various contributions of the components to the functionality of various aspects of the invention. A number of possible alternative features are introduced during the course of this description. It is to be understood that, according to the knowledge and judgment of persons skilled in the art, such alternative features may be substituted in various combinations to arrive at different embodiments of the present invention.

6. Preloaded Catheter System Overview

[0064] The invention provides a catheter system that enables problems identified above to be overcome. In particular, the invention describes a system/assembly of a preloaded stent, microwire, and catheter system, referred to herein as a preloaded catheter system (PCS) 20 that can be effective in reducing the number of steps and hence time required to effect stent deployment, clot capture and recovery.

[0065] As shown in FIGS. 3, 3A, 3B and 3C, the PCS 20 includes a microwire (MW) 22, a stent 24 and an outer catheter system (OCS) 26. Generally, during a surgical procedure and after the surgeon has gained access to the appropriate carotid artery, the PCS is advanced towards a clot, via sequential and iterative movement of the MW and OCS. That is, the surgeon will sequentially steer and advance the MW towards the clot and follow the MW with the OCS.

[0066] When the clot is reached, the MW is positioned distal to the clot and the distal tip of the OCS also advanced past the clot. As will be explained in greater detail below, the MW is partially withdrawn to lock and engage with the stent, which is retained within the OCS. After the MW locks and engages the stent (FIG. 3A) by applying a distal pressure to the MW, the OCS is withdrawn such that the stent is deployed from the distal tip of the OCS (FIG. 3B).

[0067] After the stent has been deployed, the surgeon waits a period of time to allow the clot to entangle with the stent. When the clot has become entangled with the stent, both the OCS and stent carrying the clot will be withdrawn proximally into an aspiration catheter to substantially complete the procedure.

[0068] Further description of each component follows:

7. Outer Catheter System (OCS) 26

[0069] As shown in FIG. 3 (not to scale), the OCS is generally comprised of 3 zones including a distal tip zone (A), a stent preload zone (B) and a proximal zone (C).

[0070] 7.1. Distal Tip Zone (A)

[0071] The distal tip zone generally functions as a microcatheter, that is zone A is characterized as having an outer diameter of 1.5-2.5 F and inner dimensions enabling passage of a MW 22 and compressed stent through this zone. Zones A and C will typically have an inner diameter D1A, D3A of about 0.6 mm. The MW will typically have an outer diameter (MWD) of about 0.35 mm.

[0072] Zone A will be typically be 6-8 cm in length from the distal tip 31.

[0073] 7.2. Stent Preload Zone (B)

[0074] The stent preload zone (B) generally functions to provide a) tapered outer surfaces 27a, 27b to facilitate movement of the OCS through tortuous regions and b) an inner stent cavity 26c to hold a stent 24 during distal movement of the PCS.

[0075] The distal taper zone 27b tapers from the zone A diameter D1 (1.2-2.5 F) to the zone B diameter D2 (typically 6-8 F). Zone B is preloaded with a stent 24 within stent chamber 26c that operatively retains the stent in a partially expanded state. The proximal side of zone B tapers from D2 to D3 in zone C. The inner diameter D2A of the lumen of zone B is in the range of 1 mm.

[0076] The typical length of a stent is about 2-4.5 cm and will have a OD of about 4-6 mm when fully expanded; hence, the stent chamber will have a substantially corresponding length and a lumen diameter large enough to accommodate both the MW and partially collapsed stent; thus, will be in the range of 1 mm or roughly about 25% of the expanded diameter of the stent. Importantly, the distal and proximal ends of the stent chamber will have tapered surfaces to enable the stent to smoothly expand and compress as the stent is placed within or transitioned out of the stent chamber.

[0077] Once placed within the stent chamber, the stent will thus expand radially against the inner walls of the stent chamber thus maintaining a void volume within the interior of the stent chamber.

[0078] 7.3. Stent and Microwire

[0079] A stent 24 is configured for functional placement within the stent chamber. Initially, that is at the beginning of a procedure, the stent is not engaged or locked with the MW. Immediately prior to deployment, the stent is connected to the MW (explained below) and can thereafter be a) collapsed and deployed from the OCS through zone A and b), if necessary withdrawn back into the OCS through zone A.

[0080] The MW is substantially a typical MW having the length and properties to function as a MW within a microcatheter including a tip 33 that may be of a fixed shape or formable by the surgeon. Other properties of torqueability and steerability will be present in the MW without interfering with the stent in zone B. The MW will include a MW lock 30b configured to the MW approximately 7-10 mm from the distal tip of the MW. The MW lock will not interfere with the normal operation of the MW within zone A.

[0081] In order to enable the catheter positioning procedure and the lock connection, during advancement of the PCS the MW and OCS can be moved with respect to one another where the stent remains statically fixed within the stent chamber from radial pressure exerted by its wire frame against the inner walls of the lumen of zone B.

[0082] At the time of stent deployment, the surgeon draws back on the MW to engage lock components 30a, 30b on the stent and MW.

[0083] As shown, the stent has a proximal end 28a and a distal end 28b. In order to enable proximal movement of a deployed stent and to pull an engaged clot proximally, the proximal end of the stent must engage with the MW lock. Accordingly, in one embodiment, the MW includes a stent lock 30a and a MW lock 30b that can engage together to lock the two pieces together. The MW lock 30b may be an expanded volume on the MW that engages with a corresponding and mating stent lock 30a on the proximal end of the stent.

[0084] In operation, by gently pulling the MW proximally, the MW lock 30b passes through the interior of the stent and is guided into the stent lock 30a. As the two pieces engage, proximal pressure on the stent lock will draw the stent proximally and against the inside proximal taper 27a of the OCS. Various resistive forces can be utilized to effect permanent engagement of the MW and stent lock together.

[0085] Once engaged, the MW can be held and the OCS can then be pulled proximally such that the stent will collapse forwardly into zone A. As proximal pressure on the OCS is maintained, the stent will fully compress within zone A, progress through zone A and emerge from the distal tip 31 as shown in FIGS. 3B and 3C.

[0086] If clot capture is successful, the PCS, deployed stent and clot are withdrawn to an aspiration catheter (not shown).

[0087] If clot capture is not successful, and/or it becomes necessary to withdraw the stent back into the OCS, proximal pressure on the MW will pull and collapse the stent back into zone A of the OCS.

[0088] The locking system may be implemented in a number of ways.

[0089] It is important that the stent does not separate from the MW after deployment. Hence, the locking system should provide greater security against failure of the lock in the proximal direction rather than the distal direction.

[0090] Suitable locking systems may include various combinations of forces to ensure connection and may include devices incorporating systems having positive displacement detents, latches, twist-locks and others. These can include proximal pressure and torque via the MW as well as distal pressure provided by the OCS proximal tapered surface (including potentially additional interior surfaces) and/or an external pressure provided by a tertiary catheter external to the proximal tapered surface that could be used to effect a squeezing pressure against the proximal tapered surface to narrow the proximal tapered surface and thus provide a greater resistive force to the locking system.

[0091] The stent may have a plurality of zones as described in Applicant's co-pending application 62/696,641, incorporated herein by reference.

[0092] Further still, the OCS may enable the use of different stents having properties that would otherwise be limited by introducing a sheathed stent and having to push that stent the full distance from the extracorporeal access point to the clot site.

8. Factory Assembly

[0093] As described, the OCS includes a stent chamber (zone B) having an outer diameter D2 and adjacent zones A and C, having outer diameters D1 and D3.

[0094] Generally, the PCS is assembled in accordance with the following general steps: [0095] a. A loading MW (not shown) is threaded through a stent. The loading MW has a non-locking surface that can apply a proximal force against the distal side of the stent lock. [0096] b. The loading MW with threaded stent is fed into the distal end of an empty OCS and fully pushed to the proximal end of the OCS. [0097] c. The loading MW is continued to be pulled proximally to gently draw the stent into the OCS through the distal tip 31 and into the stent chamber. [0098] d. When correctly seated, the loading MW is fully withdrawn from the OCS through the distal tip. [0099] e. The MW 22 (having a MW lock) is loaded into the distal tip and pushed fully through to proximal end of the OCS. Markers on the proximal and/or distal end of the OCS and MW will ensure the correct linear position of the MW lock. [0100] f. Additional catheters (guide, balloon guide, aspiration) may be loaded from the proximal end of the PCS in some embodiments or packaged alongside the PCS.

[0101] It is understood that the system may be manufactured with a number of sizes and/or catheter performance features as understood by those skilled in the art.

[0102] In another aspect, the PCS may be used for the placement of stents used in the treatment of aneurysms, as described in Applicant's co-pending U.S. provisional application 62/616,980, incorporated herein by reference. In these procedures, the OCS would be adapted to carry an aneurysm stent. In this case, as aneurysm stents are left in place, a MW would be used to push the stent from zones B and A of the OCS. Accordingly, in this case, a push surface would be positioned proximal to the proximal end of the stent. In this case, after positioning the tip of the OCS at the location of deployment, the original MW (i.e. a standard MVV) may be withdrawn and a separate pushing MW may be introduced. Importantly, it should be noted that as aneurysm treatment procedures are not emergency procedures, the extra step of withdrawing a MW and introducing a pushing MW is not significant.

[0103] Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.