Endovascular closure device

An aneurysm closure device that includes a retention assembly, adapted to retain the closure device in place on an aneurysm neck. Also, a seal has a wire frame, defining a set of eyeholes and thread, threaded through the set of eyeholes, to form a lattice. Finally, an expanse of silicone, is cured onto the thread, to form a barrier.

BACKGROUND

The present disclosure is directed to repairing blood vessel defects, such as aneurysms, and other physiological defects or cavities formed in lumens, tissue, and the like, and, more particularly, to an endovascular implantable device and related endoluminal delivery procedure and deployment techniques.

Cranial aneurysms occur when a weakened cerebral blood vessel (root vessel) locally expands to form a bulge or balloon-like enlargement in the vessel wall. These aneurysms can occur along a vessel wall or at locations of vessel branches, such as a T-intersection or V-intersection.

Currently, options for the treatment of brain aneurysms are limited. In one technique, the cranium is opened and a clip is placed at the aneurysm neck to cut off blood flow from the root vessel, thereby reducing swelling and stopping expansion. In another technique, the interior of the aneurysm is accessed by way of a cranial artery, which in turn is reached with a device inserted into the femoral artery. In this technique, coiling material is inserted into the aneurysm, thereby causing clotting which closes off the aneurysm. Both techniques have drawbacks. Opening the cranium always entails some risk. Some locations in the cranium are difficult or impossible to access from the outside. On the other hand, causing clotting in the aneurysm can increase the mass and size of the aneurysm, causing it to press against delicate and critical tissue, and causing further damage.

Devices and techniques have been developed to facilitate treatment of aneurysms. The application herein is a joint inventor on the following U.S. Patent Publication Nos. 2006/0264905 (“Improved Catheters”), 2006/0264907 (“Catheters Having Stiffening Mechanisms”), 2007/0088387 (“Implantable Aneurysm Closure Systems and Methods”), and 2007/0191884 (“Methods and Systems for Endovascularly Clipping and Repairing Lumen and Tissue Defects”). All of these published applications are incorporated by reference herein in their entirety, to the extent legally possible.

For example, referring toFIGS. 1A and 1B, which are reproduced from U.S. Patent Publication No. 2007/0191884, shown therein is a device130having a patch or closure structure131mounted to or associated with two anchoring structures132,133. The closure structure131is supported by a framework structure134that is provided at least in a perimeter portion and is attached to the closure structure131by means of bonding, suturing, or the like. The framework structure134is mounted to or associated with the wing-like anchoring structures132,133. These anchoring structures132,133in a deployed condition are designed so that at least a portion thereof contacts an inner wall of an aneurysm or an internal wall of an associated blood vessel following deployment.

As can be seen inFIG. 1A, the anchoring structures132,133are generally formed to curve outwardly from an attachment joint135to the framework structure134and then back inwardly toward one another at the end remote from the attachment point135. The anchoring loops132,133are generally of the same configuration and same dimension and are located opposite one another as shown inFIG. 1A.

FIG. 1Billustrates a similar device having a closure structure136with anchoring structures137,138that attach to or project from a framework structure139along opposed, lateral edges of the framework structure. The anchoring structures137,138as illustrated inFIG. 1Bare gently curved and, at their terminal sections, extend beyond corresponding terminal sections of the framework structure and the closure structure. The closure and framework structures in this embodiment are generally provided having a surface area that exceeds the surface area of the aneurysm neck, and the anchoring structures generally reside inside the aneurysm following placement of the device. In this configuration, the anchoring structures exert lateral and downward force on the closure structure so that it generally conforms to the profile of the vessel wall at the site of the aneurysm, thereby sealing the neck of the aneurysm from flow in the vessel and providing reconstruction of the vessel wall at the site of the aneurysm. Unfortunately, framework structure139and structures137and138are mismatched in length and are too stiff to apply the mutually opposing forces on interposed tissue, necessary to form an effective clip. In addition this structure is too stiff and expanded to be able to collapse into a configuration that can be fit into the space available in a placement device, small enough to be introduced into the smaller cranial blood vessels. Moreover, its boxy shape makes it difficult to maneuver as is necessary to effect placement into an aneurysm.

FIGS. 1C-1Fschematically illustrate the devices ofFIGS. 1A and 1Bdeployed at the site of an aneurysm. A bulge in the blood vessel B forms an aneurysm A. As shown inFIGS. 1C and 1D, when the device130is deployed across the neck of and within the aneurysm A, the closure structure131is positioned to cover the opening of the aneurysm and the anchoring structures132and133are retained inside and contact an inner aneurysm wall along at least a portion of their surface area. In this fashion, the closure structure131and the framework portion134are supported across the aneurysm opening and are biased against the neck of the aneurysm from outside the aneurysm.

In the embodiment illustrated inFIGS. 1C and 1D, the closure structure131and the framework portion134are deployed outside the internal space of the aneurysm. In an alternative embodiment illustrated inFIG. 1E, the closure structure131and the framework portion134are supported across the aneurysm opening and biased against the neck of the aneurysm from inside the aneurysm.

FIG. 1Fillustrates an alternative deployment system and methodology, wherein a device having at least two anchoring structures is deployed such that the closure structure131is positioned to cover the opening of the aneurysm, and the anchoring structures132,133are positioned outside the aneurysm and contact an inner blood vessel wall B in proximity to the aneurysm. In this embodiment, the anchoring structures132,133may be generally sized and configured to match the inner diameter of the vessel in proximity to the neck of the aneurysm so that following deployment the anchoring structures contact the vessel wall in a substantially continuous manner without straining or enlarging the vessel wall in the area of the aneurysm. In all of these embodiments, following placement of the device, the closure structure substantially covers the aneurysm neck to effectively repair the vessel defect. The anchoring structures do not substantially interfere with flow of blood in the vessel.

As can be seen in the foregoing, the structures may be difficult to place, particularly in the circuitous blood vessel network of the brain. For the typical aneurysm, extending in a perpendicular manner from its root blood vessel, it may be a challenge to insert the structure into the aneurysm. Moreover, for the device to seal or close the aneurysm, the anchoring structures must mutually press against the aneurysm sides. If one side wall of an aneurysm is not well suited for supporting an anchoring structure, the anchor for the opposite side will not be well supported to provide sufficient pressure on this opposite side wall. This problem drives the design of anchor structures132and133to be larger, to facilitate receiving sufficient support from the aneurysm interior surface. This, in turn, has the potential to create a mass effect problem, in which the mass of the structures132and133, plus any clotting that occurs around them, causes the aneurysm to become more massive, potentially pressing against delicate nervous system tissue as a result.

Moreover, the situation is even more difficult for aneurysms formed at the intersection of vessels, such as a T-intersection or V-intersection.FIG. 1Gillustrates a saccular bifurcation aneurysm150appearing at the intersection of two vessels152,154, branching from a stem vessel156. Cerebral bifurcation aneurysms are commonly found at the middle cerebral artery, internal carotid artery, anterior communicating artery, basilar artery, posterior communicating artery, and other locations.

Typically, to place device130into a blood vessel of the brain requires a number of steps. First, an incision is made into the femoral artery and a sheath is introduced, extending approximately to the aorta. A first guide catheter is inserted through the sheath and extended up into the carotid artery. A second guide catheter is coaxially introduced through the first guide catheter and extended up into the target aneurysm. Both guide catheters are introduced using a guide wire having a steerable tip of either stainless steel or nitinol. Then, microcatheter introducer is inserted through the guide catheter, to the aneurysm, and device130is placed at the aneurysm site. Heretofore, however, once reaching the aneurysm there has been no effective method for positioning a device that requires precise positioning. A device that would require a definite orientation, at least partially inside the aneurysm, presents particular challenges in positioning during implantation.

Another difficulty in delivering a complex implant into an aneurysm is the lack of space to pack such an implant in a lumen at the end of a microcatheter. Any such device must fold into a cylinder having an internal diameter on the order of 1 mm and a length of about 10 mm. Upon delivery it must expand to anchor itself in place and to seal an area that could be as large as 10 mm2. The seal over the neck of the aneurysm although thinner than 1 mm, must be strong enough to affirmatively occlude the aneurysm, with a very high degree of certainty.

SUMMARY

In a first separate aspect, the present invention may take the form of an aneurysm closure device that includes a retention assembly, adapted to retain the closure device in place on an aneurysm neck. Also, a seal has a wire frame, defining a set of eyeholes and thread, threaded through the set of eyeholes, to form a lattice. Finally, an expanse of silicone, is cured onto the thread, to form a barrier.

In a second separate aspect, the present invention may take the form of a method of making an aneurysm closure device, includes forming a wire frame that defines eyeholes and threading an ePTFE fiber through the eyeholes to form a lattice, which is coated with raw silicone. Finally, the silicone is cured to form a seal. In another preferred embodiment two sheets of silicone, cut to the correct dimensions, are adhered together about the ePTFE fiber.

In a third separate aspect, the present invention takes the form of a microcatheter assembly for implanting a medical device at a location in the blood vessel network of a patient. The assembly includes a flexible microcatheter that has a proximal single lumen portion, extending for at least 80% of the extent of the tube and a medial double lumen portion, immediately distal to the proximal single lumen portion, and being between 1 mm and 200 mm in length. A distal single lumen portion, holds the medical device in a contracted state. Also, first and second wires, extend through the tube and are separated into separate lumens in the medial double lumen portion and being connected to the medical device at two separate points. In addition, a control unit, having a first wire control handle affixed to the first wire and a second wire control handle affixed to the second wire. Each control handle is capable of pushing its affixed wire distally through the tube or retracting its wire proximally through the tube. Also, the first and second wire control handles can be rotated together to any rotational position. Accordingly, the wires may be advanced in a distal manner to push the medical device out of the distal lumen and the medical device may then be manipulated by changing relative position of the control handles both in translation and rotation to manipulate and implant the medical device.

In a fourth separate aspect, the present invention may take the form of a method of implanting a medical device at a blood vessel location in a patient that utilizes a microcatheter assembly that has a flexible microcatheter tube, including: a proximal single lumen portion, extending for at least 80% of the extent of the tube; a medial double lumen portion, immediately distal to the proximal single lumen portion, and being between 1 mm and 200 mm in length; a distal single lumen portion, holding the medical device in a contracted state; first and second wires, extending through the tube and separated into separate lumens in the medial double lumen portion and being connected to the medical device at two separate points, and wherein the two wires at the two separate points are detachable from said medical device. Also, a control unit has a first wire control handle affixed to the first wire and a second wire control handle affixed to the second wire, each control handle being capable of pushing its affixed wire distally through the tube or retracting its wire proximally through the tube, and where the first and second wire control handles can be rotated together to any rotational position. A guide catheter is introduced, extending from an incision into a blood vessel, to a target location for the medical device. Then the microcatheter tube is pushed through the guide catheter so that the distal portion is at the target location. Finally the medical device is pushed out of the microcatheter tube and control unit is used to manipulate the medical device until it is positioned correctly at the target location. Finally, detaching said two wires from said medical device and withdrawing the microcatheter tube and the guide catheter from the patient.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures or components or both associated with endovascular coils, including but not limited to deployment mechanisms, have not been shown or described in order to avoid unnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and variations thereof, such as “comprises” and “comprising” are to be construed in an open inclusive sense, that is, as “including, but not limited to.” The foregoing applies equally to the words “including” and “having.”

Reference throughout this description to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment.

Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The present disclosure is directed to closing a bulge or aneurysm formed in blood vessel, such as an artery or vein (referred to more generally herein as “vessel”), in a manner that does not suffer from some of the drawbacks of prior art methods. For example, in the prior art method involving the insertion of a wire coil into the aneurysm, the resultant blood clot can create problems through its mass and the possibility of pressing against nearby nerves. In addition, the wire coil can have the effect of keeping the neck open, possibly causing another aneurysm to form.

The embodiments of the present disclosure combine the closure structure and the anchoring structure into a single unit to improve compactness, allow delivery into the tortuous intracranial circulation system via a microcatheter, and to improve the aneurysm neck closure. In addition, the embodiments of the present disclosure provide enhanced rotation control and placement of the device within the aneurysm via two attachment points for a microcatheter. Moreover, markers can be used at the junctions of the device structure to aid in tracking the movement of the closure device during insertion and placement.

Referring toFIG. 2A, a preferred embodiment of an aneurysm closure device10is shown in its implanted environment of an aneurysm12attached to a root vessel14.FIG. 2Bshows the device10, implanted environment, on an aneurysm that has developed at a Y-intersection of blood vessels.FIG. 3shows a more detailed perspective view of closure device10. InFIG. 2A, aneurysm closure device10is held in place by four anchors: A first aneurysm anchor16A and a first root vessel anchor18A mutually anchor closure device10to a distal side of the aneurysm12, while a second aneurysm anchor16B and a second root vessel anchor18B, mutually anchor closure device10on a proximal side of the aneurysm12. Referring toFIG. 3, it is seen that in the installed state ofFIG. 2A, a seal20is placed over the neck of aneurysm12, thereby preventing further blood flow into aneurysm12and causing it to atrophy over time.

First anchors16A and18A act as a first clip, mutually applying gentle pressure toward each other, thereby clipping about the interposed tissue. In similar manner, second anchors16B and18B act as a second clip. Working together, anchors16A,18A,16B and18B hold the seal20in place, thereby blocking the flow of blood into aneurysm12.

Closure device10includes a wire frame22, which is made of nitinol, or some other shape-memory material. Prior to use, closure device10is maintained at a temperature below human body temperature, thereby causing wire frame to assume the shape shown inFIG. 3, when first pushed out of terminal lumen56. In one preferred embodiment, after warming to 37 C, however, anchors16A and18A, are urged together, as are anchors16B and18B, thereby more securely clipping to the interposed tissue. In another preferred embodiment, however, the natural spring force of the nitinol causes device10to expand when it is pushed out of fossa56, and it retains this shape during positioning and use. A set of eyeholes24are defined by frame22and expanded poly tetrafluoroethylene (ePTFE) thread or fiber26is threaded into these eyeholes24to form a lattice. The eyeholes24are filled with gold solder (FIG. 15B), thereby anchoring thread26and closing eyeholes24. Accordingly, although materials may be useable as thread26whatever material is used must be capable of withstanding the temperature of molten gold solder, which is typically 716° C. The ePTFE lattice work26is then coated with silicone28, which in one preferred embodiment is cured in situ to form the seal20. In another preferred embodiment, sheets of silicone are cut to the correct dimensions and adhered together about the ePTFE lattice26. In the embodiment shown, silicone28is placed on the aneurysm anchors16A and16B, but in an alternative embodiment, the ePTFE portion on anchors16A and16B are there to complete the threading arrangement, but are not coated with silicone. In another alternative preferred embodiment more, and smaller, eyeholes24are defined. In a preferred embodiment, two spots of radiopaque material30are placed at the tip of each aneurysm anchor16A and16B and one spot of radiopaque material30is placed at the tip of each root vessel anchor18A and18B. Accordingly, a surgeon placing closure device10can determine the position of closure device10, through a sequence of X-ray images, relative to the contours of the aneurysm12, which is shown by the use of a radiopaque dye, placed into the bloodstream.

In an alternative preferred embodiment at least some of the anchors, serving the function of anchors16A-18B, are made of a thin sheet of nitinol, or a thin sheet of nitinol covered with a biocompatible silicone, or polymeric material, for forming a good grip on the tissue it contacts. In yet another embodiment, at least some of the anchors are made entirely of polymeric material. In an additional preferred embodiment, ePTFE thread26lattice, is replaced with metal filigree, made of a metal such as gold, having a high melting point. In addition, there is a broad range of engineered materials that can be created for this type of purpose. In yet another preferred embodiment, anchors, serving the function of anchors16A-18B, are made of wire loops or arcs, some of which support an ePTFE reinforced silicone barrier, thereby providing a closure mechanism for an aneurysm.

Referring toFIGS. 4-14B, prior to installation, closure device10forms a part of a micro-catheter closure device installation assembly40, which although specifically adapted to install closure device10at an aneurysm also embodies mechanisms that could be used for other tasks, particularly in accessing tissue through a blood vessel. Assembly40comprises a micro-catheter subassembly42, and a user-control subassembly44. A first wire-head handle46A and a second wire-head handle46B, are attached to a first wire48A and a second wire48B, respectively.

Referring toFIGS. 7-14B, in micro-catheter subassembly42, wires48A and48B pass through a flexible tube50, which has an exterior diameter of about 1.5 mm, and which has a hydrophilic exterior surface, to aid in progressing toward a blood vessel destination. Tube50is divided into a proximal single lumen extent52, near-distal dual lumen extent54, and a distal fossa or wide-lumen extent56. This construction permits for the control of the shape and orientation of distal portion of tube50, and for the positioning of closure device10, after it has been pushed out of fossa56. As shown inFIGS. 13A and 13B, if the first wire-head handle46A is retracted relative to second wire-head handle46B, then distal fossa56bends towards handle46A. Likewise, as shown inFIGS. 14A and 14B, if the second wire-head handle46B is retracted relative to first wire-head handle46A, then distal fossa56bends towards handle46B. The orientation of fossa56, and the direction it turns to when handle46A or46B is retracted, can be changed by rotating the wire-head handles46A and46B, together. After closure device10is pushed out of fossa56, it responds in like manner, bending toward wire-head handle46A, when handle46A is retracted, and toward handle46B, when handle46B is retracted. It can be rotated, and the direction that it bends when wire46A or46B is pulled can be determined, by rotating the handles46A and46B, together. This freedom in positioning is important during the implantation process, when as shown inFIGS. 2A and 2Banchors16A and16B must be maneuvered through the neck of the aneurysm12, and positioned so that they extend along the same dimension as root vessel14. The radiopaque markings30(FIG. 3) are invaluable during this process.

Referring now toFIG. 6, subassembly42is threaded through an end cap60, and passes into a transparent chamber62, where wires48A and48B, emerge from tube50, pass through a slider64and are separately anchored in handles46A and46B, respectively. The travel extent of slider64is limited by a stop pin66and a slot68.

Wires48A and48B each include a region70(FIGS. 7 and 8) that is susceptible to electrolytic disintegration. To detach closure device10, after placement, an electric current is passed through wires48A and48B, causing regions70to electrolytically disintegrate, freeing closure device10from wires48A and48B, so that it can be left in place in its target location, sealing aneurysm12. In a preferred embodiment, handles46A and46B each includes an electrical contact connected to wire48A and48B, respectively, for attaching to a source of electricity for performing the above-described step.

Skilled persons will readily recognize, from the drawings and the above text, that a point on the region70of first wire48A constitutes a first attachment point to aneurysm seal20, which is a type of medical device. Likewise, a point on the region70of second wire48B, constitutes a second attachment point to seal20, which is spaced apart from the first attachment point. Such persons will further recognize that first wire48A can be used to either push or pull the first attachment point and second wire48B can be used to either push or pull the second attachment point.

Subassembly42is introduced into the femoral artery and guided through the carotid artery into the brain's arterial system, and further guided to the aneurysm12. At this point closure device10is pushed out of fossa56, anchors16A and16B are guided into aneurysm12, and anchors18A and18B are positioned in root artery14. Then a pulse of electricity severs closure device10from wires48A and48B and closure device10is installed in place.

Wires48A and48B are made of stainless steel alloy 304, which may also be referred to as alloy 18-8. This material is coated with poly tetrafluoroethylene, except for at detachment points70and the points where they are connected to a source of electricity. The nitinol alloy that frame22(FIG. 3) is made of is 54.5% to 57% nickel, with the remainder titanium, which forms a super-elastic alloy. The introducer tube50is made of high density polyethylene, coated at the distal tip with a hydrophilic coating. Finally, the silicone28of the closure device10is silicone MED 4820 or MED-6640, which is a high tear strength liquid silicone elastomer, having a Shore A durometer reading of 20-40. A MED6-161 Silicone Primer is used to attach silicone28to Nitinol frame22.