WO2010014447A2

WO2010014447A2 - Embolectomy stroke device

Info

Publication number: WO2010014447A2
Application number: PCT/US2009/051124
Authority: WO
Inventors: Nana Amiridze
Original assignee: University Of Maryland, Baltimore
Priority date: 2008-07-29
Filing date: 2009-07-20
Publication date: 2010-02-04
Also published as: WO2010014447A3

Abstract

Devices and methods for removing an obstruction from a blood vessel are described. The devices are deployed in a collapsed condition and are then expanded within the body. The devices are then manipulated to engage and remove the obstruction. A system for removing an obstruction from a blood vessel includes an obstruction engaging element and an expandable capture element. The capture element preferably has a flexible cover and an expandable support structure. The engaging element engages the obstruction and moves the obstruction into the capture element. The capture element protects the obstruction when the obstruction is moved into the catheter.

Description

Embolectomy Stroke Device

Technical Field

The present invention relates generally to medical methods and devices, and more particularly to methods and devices for removing obstructions from blood vessels. Background Art

Various types of thromboembolic disorders, such as stroke, pulmonary embolism, peripheral thrombosis, atherosclerosis, and the like, are known to affect many people. Such thromboembolic disorders are typically characterized by an occlusion of a blood vessel. The occlusion is typically caused by a clot (i.e., a viscoelastic (jelly like) blood clot comprised of platelets, fibrinogen and other clotting proteins) that has become lodged at a specific location in a blood vessel.

In cases where the embolism is located in a vein, the obstruction created by the embolus may give rise to a condition of blood stasis, with the development of a condition known as thrombophlebitis within the vein. Moreover, peripheral venous embolisms may migrate to other areas of the body where even more serious untoward effects can result. For example, the majority of pulmonary embolisms are caused by emboli that originate in the peripheral venous system, and which subsequently migrate through the venous vasculature and become lodged with the lung.

In cases where the embolism is located within an artery, the normal flow of arterial blood may be blocked or disrupted, and tissue ischemia (lack of available oxygen and nutrients required by the tissue) may develop. In such cases, if the embolism is not relieved, the ischemic tissue may become infarcted (i.e., necrotic). Depending on the type and location of the arterial embolus, such tissue infarction can result in death and amputation of a limb, myocardial infarction, or stroke. Notably, strokes caused by emboli that become lodged in the small blood vessels of the brain continue to be a leading cause of death and disability, throughout the world.

In modern medical practice, thromboembolic disorders are typically treated by one or more of the following treatment modalities: a) pharmacologic treatment wherein thrombolytic agents (e.g., streptokinase, urokinase, tissue plasminogen activator (TPA)) and/or anticoagulant drugs (e.g., heparin, warfarin) are administered in an effort to dissolve and prevent further growth of the clot; b) open surgical procedures (e.g., surgical embolectomy or clot removal) wherein an incision is made in the blood vessel in which the clot is lodged and the clot is removed through such incision-sometimes with the aid of a balloon-tipped catheter (e.g., a "Fogarty Catheter") which is passed through the incision and into the lumen of the blood vessel where its balloon is inflated and used to extract the clot out of the incision; and, c) transluminal catheter-based interventional procedures wherein a clot removing/disrupting catheter (e.g., a suction-type catheter having a suction tip, clot-capturing type catheter having a clot capturing receptacle (e.g., a basket, coil, hook, etc.), or clot-disrupting catheter having a clot disrupting apparatus (e.g., an ultrasound probe or laser)) is percutaneously inserted and advanced through the patient's vasculature to a location adjacent the clot. The suction tip, clot-capturing receptacle, or clot disrupting apparatus is used to aspirate, capture & remove, disrupt or ablate the offending clot.

Each of the above-listed treatment modalities has its own set of advantages and disadvantages. For example, pharmacologic treatment has the advantage of being noninvasive and is often effective in lysing or dissolving the clot. However, the thrombolytic and/or anticoagulant drugs used in these pharmacologic treatments can cause untoward side effects such as bleeding or hemorrhage. Also, in cases where time is of the essence, such as cases where an arterial thromboembolism is causing severe tissue ischemia (e.g., an evolving stroke or an evolving myocardial infarction) the time which may be required for the thrombolytic drugs to fully lyse or dissolve the blood clot and restore arterial blood flow may be too long to avoid or minimize the impending infarction.

Open surgical thrombus -removing procedures can, in many cases, be used to rapidly remove clots from the lumens of blood vessels, but such open surgical procedures are notoriously invasive, often require general anesthesia, and the use of such open surgical procedures is generally limited to blood vessels which are located in surgically accessible areas of the body. For example, many patients suffer strokes due to the lodging of blood clots in small arteries located in surgically inaccessible areas of their brains and, thus, are not candidates for open surgical treatment.

Transluminal, catheter-based interventional procedures are minimally invasive, can often be performed without general anesthesia, and can in some cases be used to rapidly remove a clot from the lumen of a blood vessel. However, such catheter-based interventional procedures are highly operator-skill-dependent, and can be difficult or impossible to perform in small or tortuous blood vessels. Thus, patients who suffer strokes due to the presence of clots in the small, tortuous arteries of their brains may not presently be candidates for catheter-based, transluminal removal of the clot, due to the small size and tortuosity of the arteries in which their clots are located.

In concept, the transluminally deployable clot capturing type of catheters could be useable in ischemic strokes, because they are typically capable of removing an offending blood clot without the need for suction or application of energy (e.g., laser, ultrasound) which could be injurious to the delicate, small blood vessels of the brain. However, none of the prior art transluminally deployable clot capturing type of catheters are believed to be of optimal design for use in the small blood vessels of the brain because they are a) not equipped with appropriate guide wire passage lumens to allow them to be passed over previously inserted, small-diameter (e.g., 0.006-0.018 inch) guide wires, b) they are not adapted for rapid exchange over a guide wire of standard length (e.g., a guide wire which is less than twice the length of the catheter) and c) the clot capturing receptacles of these catheters are not optimally constructed and configured for removal of clots from very small blood vessels as are typically found in the brain.

One such system for removing obstructions in a blood vessel is described in U.S. Pat. No. 5,102,415 to Guenther et al. The system has a balloon catheter and a catheter having an expandable tip that receives the obstruction. The balloon catheter is passed through the obstruction while the balloon is deflated. The balloon is then inflated and the tip of the catheter is expanded. The balloon is then moved proximally so that the obstruction is pulled into the expanded tip of the catheter. A problem with this system is that the interaction between the balloon catheter and the leading edge of the catheter may tend to shear off portions of the obstruction. This can cause obvious problems when working in sensitive vascular areas. Other examples of transluminally deployable clot-capturing type embolectomy catheters of the prior art include those described in U.S. Pat. No. 4,706,671 to Weinrib, and U.S. Pat. Nos. 4,873,978 and 5,011,488 both to Ginsburg, describe the use of a coiled section for the removal of thromboembolic material. Several methods are known for mechanically removing clots to treat cerebral occlusions. For example, U.S. Pat. No. 5,895,398 to Wensel et al. discloses a clot capture device where a small catheter is first passed in a distal direction through a viscoelastic clot. The coil is contracted to a reduced profile state within the lumen of a delivery catheter, and the catheter is used to cross a clot. The coil is then advanced through the catheter and deployed on the distal side of the clot. Once the coil is disposed distal to the clot, the coil is deployed and retracted proximally to engage and remove the clot. The clot capture coil may be a plurality of wires having shape memory, which radially expand into a variety of shapes that, when the insertion mandrel is retracted, ensnare the clot for removal.

A primary drawback associated with the device described in the Wensel patent is that the deployed coil contacts the intima of the vessel, and may damage the vessel wall when the coil is retracted to snare the occlusion. Additionally, the configuration of the coil is such that the device may not be easily retrieved once it has been deployed. For example, once the catheter has been withdrawn and the coil deployed distal to the occlusion, it may be difficult or impossible to exchange the coil for another of different dimensions.

U.S. Pat. No. 5,972,019 to Engelson et al. describes a deployable cage assembly that may be deployed distal to a clot. Like the Wensel device, the device described in the Engelson patent is depicted as contacting the intima of the vessel, and presents the same risks as the Wensel device. In addition, because the distal end of the device comprises a relatively large profile, the risk of dislodging emboli while crossing the clot is enhanced, and maneuverability of the distal end of the device through tortuous vasculature may be reduced.

Despite extensive development in this area, for the reasons stated above and/or other reasons, none of the prior art embolectomy catheters are believed to be optimally designed for treating ischemic stroke. In the initial stages of stroke, a CT scan or MRI may be used to diagnose the cerebral occlusion, which commonly occurs in the middle cerebral arteries. Many current technologies position a catheter proximal to the occlusion, and then deliver clot-dissolving drugs to treat the lesion. A drawback associated with such technology is that delivering drugs may require a period of up to six hours to treat the occlusion adequately. Another drawback associated with lytic agents

(i.e., clot dissolving agents) is that they often facilitate bleeding.

When removing a thrombus using a mechanical embolectomy device, it is beneficial to engage the thrombus and remove it as cleanly as possible, to reduce the amount of emboli that are liberated. However, in the event that emboli are generated during mechanical disruption of the thrombus, it is imperative that they be subsequently removed from the vasculature.

In view of these drawbacks of previously known devices, it would be desirable to provide apparatus and methods for removal and recovery of thrombi and/or emboli from the vessels affecting cerebral circulation (carotid and vertebro-basilar systems) above the carotid bifurcation.

It also would be desirable to provide apparatus and methods that quickly and efficiently treat cerebral occlusions while reducing trauma imposed upon cerebral vessels. It further would be desirable to provide apparatus and methods for an embolectomy device that may be used to snare and hold an occlusion.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide an embolectomy device that avoids the disadvantages of the prior art.

It is further an object of the present invention to provide apparatus and methods for removal and recovery of thrombi and/or emboli from the vessels affecting cerebral blood flow above the carotid bifurcation.

It also is an object of the present invention to provide apparatus and methods that quickly and efficiently treat cerebral occlusions while reducing trauma imposed upon cerebral vessels.

It is another object of the present invention to provide apparatus and methods for an embolectomy device that may be used to snare and hold an occlusion.

These and other objects of the present invention are accomplished by providing an embolectomy device having a self-expandable stent with an expandable membrane disposed near the distal end. The membrane can be pulled over the stent to capture and hold an occlusion for removal.

Brief Description of the Drawings

The above and other features, aspects, and advantages of the present invention are considered in more detail, in relation to the following description of embodiments thereof shown in the accompanying drawings, in which:

Figure 1 is a side view of an embolectomy device according to a first embodiment of the present invention. Figure 2 is a view of the embolectomy device of Figure 1 , with a membrane covering the stent.

Figures 3 and 4 are a side view of two versions of a retrieval device according to another embodiment of the present invention. Figure 5 is a side view of a covered stent according to another embodiment of the present invention.

Best Mode(s) for Carrying Out the Invention

Referring to the drawings, Figure 1 shows an embolectomy device, indicated generally as 10, according to the present invention. The embolectomy device 10 has a retrievable stent 13 comprising a substantially cylindrical body 15 and a basket 18, 19 on both ends. In a preferred embodiment, the stent 13 has a closed cell configuration and even more preferably is of the self-expanding type. The retrievable stent 13 may be approximately 10 - 20 mm in length and 2.5 - 4.5 mm in diameter. The basket 18 on a distal aspect 21 of the device 10 is covered by an expandable semi-permeable membrane 24. At least one tether 27 may be attached to an edge of the semi-permeable membrane

24, extending to the proximal aspect 30 of the device 10. The tether 27 is sized and configured to enable the semi -permeable membrane 24 to be pulled over the stent 13.

The closed cell structure of the stent 13 provides the necessary scaffolding to hold the semi-permeable membrane 24 in a deployed configuration as illustrated in Figure 2. The semi-permeable membrane 24 helps to prevent the escape of collected emboli.

The semi-permeable membrane 24 may be comprised of any appropriate material such as polyethylene, and may be drilled (for example, formed by known laser techniques) or otherwise include one or more openings. The holes or openings can be sized to allow blood flow therethrough but restrict flow of solids, debris, or emboli. In one preferred embodiment, the semi-permeable membrane 24 has openings or pores in a range of about 20 to 400 microns in diameter, and more preferably, about approximately 80 microns. These pore sizes permit blood cells (which have a diameter of approximately 5 to 40 microns) to easily pass through, while capturing thrombus or emboli. Other pore numbers and sizes may be empirically selected with regard to the potential trade-offs in efficacy, ease of use, and other related factors that will be apparent to one of skill in the art. Alternatively, the semi-permeable membrane 24 may comprise a woven material, for example, formed from the above-mentioned polymers, having a pore diameter determined as a function of the pattern and tightness of the weave.

Additionally, the semi-permeable membrane 24 may be coated with a lubricious coating that incorporates anti-coagulant agents, such as heparin. The lubricious coating, such as a hydrophobic or hydrophilic thin layer, however, should not occlude the pores of the semi-permeable membrane 24. Advantageously, such a lubricious coating may decrease friction between the semi -permeable membrane 24 and the delivery sheath to enable a lower delivery profile for the embolectomy device 10.

In use, the embolectomy device 10 is useful for performing mechanical embolectomy. After placement of the embolectomy device 10 in a delivery catheter, the retrievable stent 13 will be advanced through a clot within the intracranial vessel. The stent 13 will be deployed within the clot and unsheathed from the catheter to allow opposition of the stent 13 along the vessel wall, with the clot inside the stent 13. The semi-permeable membrane 24, mounted on the distal aspect 21 of the stent 13, will then be pulled by the tethers 27 over the stent 13 to secure the clot within the embolectomy device 10. Next, the stent 13, with the clot inside, is pulled out of the intracranial vessel.

In another embodiment, a two-piece embolus retrieval device can be used to retrieve a blood clot from intracranial vessels. The first part is a mechanical embolectomy device 10 as described above with reference to Figure 1; that is, a self- expanding, retrievable stent 13 with a distal part 21 covered by a semi -permeable membrane 24. In this embodiment, the semi-permeable membrane does not have tethers attached thereto. In a preferred embodiment, the embolectomy device 10 is approximately 10 - 20 mm in length and 2.5 - 4.5 mm in diameter and uses a no. 10 or 14 wire.

Referring to Figure 3, the second part of the device is a retrieval portion, indicated generally as 40. The retrieval portion 40 comprises a substantially cylindrical body 42 and a basket 44 on the proximal end 47. The distal end 48 is open. In a preferred embodiment, the body 42 comprises a self-expanding, retrievable stent having a closed cell configuration. A semi -permeable membrane 24 covers the basket 44 and body 42 of the retrieval portion 40. In a preferred embodiment, the retrieval portion 40 is slightly longer and narrower than the embolectomy device 10; approximately 12 - 25 mm in length and 2 - 4 mm in diameter.

In use, the two-piece embolus retrieval device can be used to retrieve a blood clot from intracranial vessels. After placement of the embolectomy device 10 in a delivery catheter, the stent 13 will be advanced through a clot within the intracranial vessel. The stent 13 will be deployed within the clot and unsheathed from the catheter to allow opposition of the stent 13 along the vessel wall, with the clot inside the stent 13. The retrieval portion 40 is placed over the stent wire and pushed over the stent 13 to cover the stent 13, with the clot inside. The retrieval portion 40 is then locked to the stent 13, and both devices are then pulled out together.

As shown in Figure 4, an alternate retrieval portion, indicated generally as 50, can be used. In the alternate embodiment, the retrieval portion 50 is a mirror-image of retrieval portion 40 and comprises a substantially cylindrical body 52 and a basket 54 on the distal end 57. The proximal end 58 is open. In a preferred embodiment, the body 52 comprises a self-expanding stent having a closed cell configuration. A semi-permeable membrane 24 covers the basket 54 and body 52 of the retrieval portion 50. In a preferred embodiment, the retrieval portion 50 is slightly longer and narrower than the embolectomy device 10; approximately 12 - 25 mm in length and 2 - 4 mm in diameter.

In use, after the stent 13 has been deployed within the clot and unsheathed to allow opposition of the stent 13 along the vessel wall, with the clot inside the stent 13. The retrieval portion 50 is pulled over the stent 13 to cover the stent 13, with the clot inside. The retrieval portion 50 is then locked to the stent 13, and both devices are then pulled out together.

Referring to Figure 5, another embodiment of the invention is shown. A covered stent, indicated generally as 63, can be used to assist in intracranial aneurysm embolization. The covered stent 63 comprises a substantially cylindrical body 66. In some embodiments, the covered stent 63 may include a basket 68, 69 on one or both ends. In a preferred embodiment, the stent 63 has a closed cell configuration and even more preferably is of the self-expanding type. The body 66 is covered with a membrane 72. In a typical embodiment, the membrane 72 will not cover the baskets 68, 69. In some embodiments, the membrane 72 will be semi-permeable, as described above, but the membrane 72 need not be such. Preferably, the covered stent 63 is a retrievable stent. To use the covered stent 63 for aneurysm embolization, initially a microcatheter will be placed in the aneurysm 75. The covered stent 63 will then be placed in the intracranial vessel 77 across the neck 80 of the aneurysm 75. After embolization with coils, liquid embolic agent, or other method, the stent 63 can be recovered and removed.

The stent 63 prevents displacement of the embolic material or blood clot from the aneurysm 75 during embolization and does not occlude blood flow in the vessel 77 during the procedure. Industrial Applicability

The present invention is applicable to providing a device for removing an obstruction from a blood vessel. The invention discloses an embolectomy device having a self-expandable stent with an expandable membrane disposed near an end of the stent.

The membrane can be pulled or pushed over the stent to capture and hold an occlusion for removal. The stent can also be used to assist in the embolization of an aneurysm.

Claims

Claims What is claimed is: 1. A mechanical embolectomy device, comprising: a first stent having a first basket on a first end and a second basket on a second end; and an expandable membrane covering the first basket.

2. The embolectomy device of claim 1 wherein said first stent comprises a retrievable stent.

3. The embolectomy device of claim 1 wherein said first stent is self expandable.

4. The embolectomy device of claim 1 wherein said first stent has a closed cell configuration.

5. The embolectomy device of claim 1 wherein said first stent comprises an intracranial stent.

6. The embolectomy device of claim 1 wherein said membrane is semi-permeable.

7. The embolectomy device of claim 1, further comprising: at least one tether to pull said membrane over said first stent.

8. The embolectomy device of claim 7 wherein said at least one tether is attached to an edge of the membrane.

9. The embolectomy device of claim 1 , further comprising: a stent retrieval device comprising: a substantially cylindrical body having a basket on one end and being open on the other end.

10. The embolectomy device of claim 9 wherein said body further comprises a second stent.

11. The embolectomy device of claim 10 wherein said second stent comprises a self- expandable stent.

12. The embolectomy device of claim 10 wherein said second stent has a closed cell configuration.

13. The embolectomy device of claim 9, further comprising: a membrane covering said body.

14. The embolectomy device of claim 13 wherein said membrane is semi-permeable.

15. The embolectomy device of claim 9 wherein said body is longer than said first stent.

16. The embolectomy device of claim 9 wherein said body is narrower than said first stent.

17. An intracranial stent, comprising: a body; and a membrane covering the body.

18. The intracranial stent of claim 17 wherein said stent is retrievable.

19. The intracranial stent of claim 17 wherein said stent is self-expandable.

20. The intracranial stent of claim 17 wherein said stent has a closed cell configuration.

21. The intracranial stent of claim 17 wherein said membrane comprises a semi- permeable membrane.

22. The intracranial stent of claim 17, said intracranial stent further comprising a basket on each end of said stent.

23. The intracranial stent of claim 22 wherein said membrane does not cover said baskets.

24. A method of removing a clot from a vessel of a patient, comprising the steps of: placing an embolectomy device in a delivery catheter wherein said embolectomy device comprises: a first stent having a first basket on a first end and a second basket on a second end; and an expandable membrane covering the first basket; advancing the first stent through a clot within an intracranial vessel; deploying the first stent from the catheter to allow opposition of the first stent along the vessel wall, with the clot inside the first stent; expanding the membrane to cover the first stent and the second basket; and removing the first stent from the intracranial vessel, with the clot inside.

25. The method of removing a clot of claim 24, said embolectomy device further comprising at least one tether attached to said membrane, said steps of expanding the membrane to cover the first stent and the second basket further comprising, pulling said at least one tether to pull said membrane over said first stent.

26. The method of removing a clot of claim 24 wherein said membrane is semi- permeable.

27. A method of removing a clot from a vessel of a patient, comprising the steps of: placing an embolectomy device in a delivery catheter wherein said embolectomy device comprises: a first stent having a first basket on a first end and a second basket on a second end; and a first membrane covering the first basket; advancing the first stent through a clot within an intracranial vessel; deploying the first stent from the catheter to allow opposition of the first stent along the vessel wall, with the clot inside the first stent; advancing a retrieval device toward the first sent wherein said retrieval device comprises: a second stent having a basket on one end and being open on the other end; and a second membrane covering said second stent; moving said second stent to cover the first stent with the clot inside; locking the first stent and second stent together; and pulling the first stent and second stent out together

28. The method of removing a clot of claim 27 wherein said second stent is longer than said first stent.

29. The method of removing a clot of claim 27 wherein said second stent is narrower than said first stent.

30. The method of removing a clot of claim 27 wherein said first membrane and said second membrane are semi-permeable.