Electrolytically severable joint for endovascular embolic devices

- 28036 Madrid

ES 2 201 153 T3

DESCRIPTION

Electronically separable junction for endovascular embolic devices.

This invention is an apparatus for endovascular occlusion by forming thrombi in arteries, veins, aneurysms, vascular malformations, and arteriovenous fistulas. In particular, it concerns an improved sacrificial connection between an endovascular device that is inserted and intended to remain in the desired location for thrombus formation and the device used to insert the anterior device. The invention further includes a method for introducing the device and its electrolytic separation.

Approximately 25,000 ruptured intracranial aneurysms occur each year in North America. The primary purpose of treating a ruptured intracranial aneurysm is to prevent rebleeding. There are a variety of ways to treat ruptured and ruptured aneurysms.

Possibly the most widely known of these procedures is an extravascular method using surgery or microsurgery. This treatment is common with saccular intracranial aneurysms. The method comprises a step of placing a staple in the neck of the aneurysm, attaching a neck suture, or wrapping the entire aneurysm. Each of these procedures is performed by intrusive invasion of the body and performed from outside the aneurysm or target site. In these surgical procedures, general anesthesia, craniotomy, retraction of the brain, and placement of a staple around the neck of the aneurysm are usually required. The surgical procedure is often delayed while waiting for the patient to medically stabilize. For this reason, many patients die from the underlying disease or defect before the procedure begins.

Another procedure - the extra intravascular method - involves surgically exposing or stereotactically reaching an aneurysm with a catheter. The aneurysm wall is then pierced from the outside and various techniques are used to occlude the inside to prevent rebleeding. Techniques used to occlude the aneurysm include electrothrombosis, adhesive embolization, pig hair embolization, and ferromagnetic thrombosis. These procedures are discussed in US Patent No. 5,122,136 to Guglielmi et al.

Still another method is less invasive and is further described by Guglielmi et al. It is the endovascular method. In this method, the interior of the aneurysm is entered using a catheter such as those shown in Engelson (Catheter Guidewire) US Patent No. 4,884,579 and also in Engelson (Catheter for Guideware Tracking) US Patent No. 4,739,768. These patents describe devices that use metal guides and catheters that allow access to the aneurysm from remote points in the body. Specifically, with the use of catheters that have highly flexible distal areas and metal guides that can be directed to the aneurysm site, embolic devices that can be delivered through the catheter are an alternative to extravascular and extra-intravascular methods.

The endovascular method usually includes two main parts. The first part involves introducing the catheter at the site of the aneurysm using devices such as those shown in the Engelson patents. The second part often involves filling the aneurysm in one way or another. For example, a balloon can be inserted into the aneurysm from a distal part of the catheter where it is inflated, dislodged, and left to occlude the aneurysm. In this way, the main artery is protected. Balloons are beginning to have less going for them due to the difficulty of inserting the balloon into the aneurysm sac, the possibility of rupture due to overinflation of the balloon within the aneurysm, and the risk associated with traction produced when the balloon is dislodged .

A highly desirable embolism device that can be inserted into an aneurysm using endovascular site procedures is found in US Patent No. 4,994,069 to Ritchart et al. It describes a device - usually a platinum / tungsten alloy coil having a very small diameter that can be introduced into the aneurysm through a catheter such as those previously described by Engelson. These coils are often made of wire having a diameter of 0.051-0.152 mm (2-6 thousandths of an inch). The diameter of the spiral can be 0.254-0.762 mmm (10-30 thousandths of an inch). These soft, flexible coils can be of any length desired and appropriate for the site to be occluded. For example, coils can be used to fill saccular aneurysms. Within a short period of time after filling the aneurysm with the embolic device, a thrombus forms in the aneurysm and immediately thereafter is supplemented with a collagenous material that significantly reduces the potential for rupture of the aneurysm.

Spirals such as those shown in Ritchart et al. they can be transported to the vascular site in a variety of ways including, e.g. eg, its mechanical deposit from the transport device as shown in US Patent no. 5,250,071 from Palermo or by electrolytic deposition as shown in Guglielmi et al. (US Patent No. 5,122,136) as mentioned above.

Guglielmi et al. show an embolism-forming device and procedure for using this device. Specifically, Guglielmi et al. they fill a vascular cavity such as an aneurysm with an embolic device such as a platinum coil that has been endovascularly transported. The coil is then separated from the insertion instrument by applying a small electrical current. Desirably, the insertion device involves a metal guide that is secured at its distal end to an embolic device by an electrolytically sacrificial junction. Guglielmi et al. suggest that when the embolic device is a platinum coil, the platinum coil can be 1-50 cm or longer if necessary. The proximal metal guide of the embolic coil is often made of stainless steel. The metal guide is used to push the platinum embolic coil, obviously very carefully, to the vascular site to be occluded. The patent shows a variety of ways to attach the embolic coil to the metal push guide. For example, the metal guide is tapered at its distal end and the distal tip of the metal guide is welded at the proximal end.

ES 2 201 153 T3 of the embolic coil. Additionally, a stainless steel coil is coaxially wrapped around the sharp distal portion of the metal guide to provide strong support for the metal guide. This stainless steel coaxial wire is attached to both the metal guide and the embolic coil. Insulation can be used to cover a portion of the reinforcing stainless steel coil. This arrangement provides two areas that must be electrolytically separated before separating the embolic coil from the metal guide.

A further variation of the detachable Guglielmi coil is one in which the distal tip of the stainless steel wire guide is not welded to the proximal end of the embolic device. A simple stainless steel tapered wire is attached from the stainless steel wire guide to the embolic coil.

An additional variation found in Guglielmi et al. includes a thin, wire-like extension between the center of the wire guide and the proximal end of the embolic coil. In this way, the wire guide does not stretch the embolic coil, but instead relies on a separately inserted extension.

A continuation application in part to the Guglielmi et al. Patent. discussed above, Pat. US No. 5,354,295, "IMPROVEMENTS IN AN ENDOVASCULAR ELECTROLYTICALLY DETACHABLE WIRE AND TIP FOR THE FORMATION OF THROMBUS IN ARTERIES, VEINS, ANEURISMS, VASCULAR MALFORMATIONS AND ARTERIOVENOUS FISTULAS" issued October 11, 1994, describes the use mechanically separable embolic devices as well as those that are electrolytically separable. Embolic devices can be enlarged with attached filaments.

Dr. Taki has devised a variation of Guglielmi's detachable coil using a copper joint between the metal guide and the coil.

None of the cited procedures using electrolytically removable embolic devices suggest the structure of the sacrificial junctions described herein.

Document WO-A-95/12367 (EP-A-0 726,745 & EP-A-0 807,410) which is admissible only under Article 54 (3) EPC, discloses metal guides having the construction illustrated in Figures 1- 7 of the present case.

In accordance with the present invention there is provided a metallic guide for use in the formation of a vascular occlusion, in combination with a catheter, comprising:

a central wire, said central wire having a shaft and not being susceptible to electrolytic disintegration in the blood;

a discrete, sacrificial, separable junction having a diameter and which is susceptible to electrolytic disintegration in blood, distal and removably connected to said core wire, wherein said junction has a length no greater than the diameter of the junction, or the joint surface after disintegration is not substantially larger than a circle having the diameter of the joint would be, and wherein said core wire is insulated proximal to the junction with at least one layer of an adherent polymeric coating, said sacrificial joint being a notch produced by laser cutting in the adherent polymeric coating, and a vaso-occluder device that is extends distally from said central wire and adapted to form said occlusion at a selected point within a mammalian vasculature, Said vaso-occlusive device not being susceptible to electrolytic disintegration in blood and being detachable from the central wire after electrolytic disintegration of the sacrificial junction.

The sacrificial attachment of the wire guide allows clean and rapid separation of the vaso-occlusive device from the wire guide. Focusing the electrolysis on the sacrificial junction reduces the possibility of multiple electrolysis points occurring and large particles being released from these points.

An embodiment of the metal guide according to the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures 1 to 7 show known metal guides from WO-A-95/12367 representing prior art according to Article 54 (3) EPC.

Figures 1, 2, 3, 5, and 6 show partial cross-sectional side views of electrolytically susceptible sacrificial junction variations between a core wire and an embolic device. Figure 4 shows a cross section of the variation shown in Figure 3, Figure 7 shows a close-up side view of a variation as found in Figure 6, Figure 8 shows a side view of an assembly including the laser-marked sacrificial junction of the present invention, Figure 9 shows a side view of an assembly including the sacrificial junction shown in Figure 1; and Figures 10 and 11 schematically describe a method for deploying a vaso-occluder device using a metal guide that may or may not be in accordance with the present invention.

Each of the discrete sacrificial junctions discussed below can be used in the device shown in US Patent No. 5,122,136 to Guglielmi et al.

The first such variation is shown in Figure 1. The assembly 100 is generally composed of a central guide or wire 102 sharpened to a point at its distal end and is welded at its proximal end to a vaso-occluder device 104, which in this case is a spiral. The entire core wire 102 is covered with an insulating material such as polyfluorocarbons (eg Teflon^®), polyurethane, polyethylene, polypropylene, polyimides, or other appropriate polymeric materials, except the most distal junction shown or sacrificial junction 106. Junction 106 is not covered with electrical insulating material and is of a material susceptible to electrolyte dissolution in blood. Center wire 102 is typically 3-in-steel

ES 2 201 153 T3 oxidizable and may be disposed within a protective catheter not shown. The metal guide 102 typically has a diameter of about 0.2450.762 mm (10-30 thousandths of an inch). The wire guide is often 50-300 cm long, that is, from the exterior entry point of the body to the sacrificial junction 106.

The sacrificial junction 106 is a discrete junction. By "discrete" we preferably mean that the bond substantially dissolves upon releasing the vaso-occluder device 104. Alternatively, "discrete" may mean that the length of junction 106 is not greater than the diameter of sacrificial junction 106 or that the electrolytic surface present after the vaso-occluder device has been released is not substantially greater than it would have. a circle whose diameter is that of the sacrificial joint 106.

Also shown in Figure 1 is a coil 108 that is welded at its proximal end and is typically designed to provide some basic strength to the metal guide assembly while not adversely affecting the flexibility of the sharp portion of the center wire 102. Obviously In the area where the support coil 108 is welded to the core wire 102, there is no coating on 102 such that welding is allowed to adhere the metal surfaces. In addition, a pair of insulators can be found at the distal tip of the central wire 102: a sheath 110 and an obturator 112 that serve to further remove the stainless steel coil 108 from contact with blood while the electrolytic separation step is carried out. cape. Preferably, end plug 112 and sheath 110 are adhesively bonded to each other to form an electrical insulator or electrolysis tight housing around coil 108. End plug 112 and sheath 110 form a flat surface in the figure that is generally flat and perpendicular to the axis of center wire 102.

As noted above, the distal end of central wire guide 102 inserts into a welded joint 114 forming the proximal end of vaso-occluder device 104.

As will be discussed in more detail below, the discrete sacrificial junction 106 dissolves completely or substantially completely during electrolysis.

Figure 2 shows a more preferred variation of the device of Figure 1 having a central guide or wire 102 that may be tapered at its distal end and that is welded to the proximal end of a vaso-occluder device 104, which in this case it is a spiral. Similarly, the distal portion of wire guide 102 that has the stainless steel coil around it is encased in an end plug 107 and sheath 109 to provide additional protection to the wire guide and the enclosed stainless steel coil 108. The main difference between the device of Figure 1 and the joint assembly of Figure 2 is the use of a bevel formed in the distal area. The combination of end plug 107 and sheath 109 allows free access of blood (and thus electolytic current) to the sacrificial junction (106). End plug 107 and sheath 110 form a flat surface in the figure that is generally flat but not perpendicular to the axis of center wire 102.

Obviously, the shape of the surface, by itself, is not very critical except to the extent that it reasonably allows free access of blood to sacrificial junction 106. Curved, ribbed, and other variations of surface finish are also available. contemplated in this invention.

Figure 3 shows a variation of the device shown in Figures 1 or 2 in which the center wire 102 enters a point having a sacrificial joint 106 that is welded to the welded joint 114 in the vaso-occluder device 104. The coil 108 provided to give additional basic strength to center wire 102 is also present. The end plug 112 is also found in this device. The variation is in outer sleeve 116. In this variation, the outer sheath extends overhead and is in contact with the welded joint 114 at the end of the vaso-occluder device 104. To allow the sacrificial joint 106 to have electrical contact with the patient's blood, a sheath 116 has a number of holes there to allow blood to come into contact with the sacrificial junction 106. The holes 118 can be seen in both Figure 3 and the cross section found in Figure 4. The end plug 112 and the cross section of the sacrificial joint 106 can also be seen in Figure 4. The variation shown in Figure 3 may have slightly greater physical strength but due to the smaller area through the holes 118, the electrolysis step may be slightly slower.

Figure 5 shows another variation of the sacrificial gasket. The device again has a central wire or metal guide that is sharpened at a small point that is welded into the weld joint 114 at the end of the vaso-occluder device 104. Again, as does the device of Figures 1, 2 and 3, all but the most distal portion 122 of center wire 120 is covered with an insulating material such as Teflon polymer.^® or other suitable insulating polymers. In this case, however, the sacrificial junction 122 that forms the distal end of the center wire 120 is surrounded, as is a portion of the tapered in the metal guide 120, with a release spring 124. The release spring 124 is attached to the body. of the metal guide but is not attached to the weld joint 114 in the vaso-occluder device 104. The release spring 124 is slightly compressed. There is, however, some space between its adjacent coils when it is positioned on the central wire 120. In this way, the blood has access to the sacrificial junction 122 between the adjacent coils of the release spring 124. When the sacrificial junction 122 dissolves , the release spring 124 gently pushes the vaso-occluder device 104 off the tip of the central wire guide 120. The release spring 124 is fully insulated except, obviously, for the part that connects to the center wire 120, if the release spring 124 is fused or welded to the center wire 120.

Figure 6 shows a variation of the device of the invention in which the center wire is tapered downward and is either directly welded to the inside of spiral 128 at weld joint 130 or is connected to a joint which is then welded to the gasket 130. A support spring 132 inside coil 128 can be used in the same way as seen in Figures 1, 2 and 3. As a safety factor, coil 128 and support spring 132 are attached to the central wire. 126. Spiral 128 is also electrically connected to center wire 126. Center wire 126,

The coil 128, and the support spring 132 are all insulated to prevent electrolysis after applying voltage to the center wire 126. The exception to this insulation is a dotted line or mark 134 which forms the discrete sacrificial junction. Spot mark 134 is shown in more detail in Figure 7. Again, the effect of the dotted line or mark 134 is that the electrolysis takes place only in this small area and when the electrolysis has completely separated the spiral 128 at this point, the potential is too small for the electrolysis to take place elsewhere. center wire 126 or spring 128.

The vaso-occluder device 104 shown in each of the drawings cited above is a coil. It can be a spiral or a braid or other vaso-occlusive device as is already known. The vaso-occluder device can be covered or connected with fibrous material bonded to the outside of the coil or braided over the outer covering as desired. These fibrous adjunct materials can be found in US Patent Application No. 07 / 965,973, by Phelps et al. or in US Patent Application No. 07 / 771,013, entitled "Vasoocclusion Coil with Attached Fibrous Elements".

In addition to the use of shrink wrap tubes containing polyethylene, polypropylene, polyurethane, poly (ethylene terephthalate), poly (vinyl chloride), or similar insulators on the core wire, another attractive thermoplastic known generically as parylene can be used. There are a variety of polymers (eg polyxylylene) based on para-xylylene. These polymers are typically placed on a substrate by vapor phase polymerization of the monomer. Parylene N coatings are produced by vaporizing a di (p-xylylene) dimer, pyrolysis, and vapor condensation to produce a polymer that is maintained at a relatively lower temperature. In addition to N-parylene, C-parylene is obtained from di (monochloro-p-xylylene) and D-parylene is obtained from di (dichloro-p-xylylene). There are a variety of known ways to apply parylene to substrates. Its use in surgical devices has been shown, for example, in US Patent No. 5,380,320 (to JR Morris), in US Patent No. 5,174,295 (to Christian et al. ), in US Patent No. 5,067,491 (Taylor et al.) and the like. Since the device of the invention is a single-use device, several of the parylenes are suitable, particularly in the area of ​​the electrolytically separable joint as an outer insulating layer. This is especially true when the coated device is tempered.

A highly desirable variation of this invention is one in which at least the area near the electrolytically separable gasket is coated with parylene and a very narrow band has been removed using a laser to form the sacrificial gasket. Coatings of less than about 0.025mm (0.001 "), preferably less than about 0.019mm (0.00075") are highly desirable.

Specifically, in Figure 8, a joint similar to those shown in Figures 5 or 6 is highlighted. The device has a guide wire or center wire 137 sharpened towards a small point that is incorporated into the welded joint 114 at the end of the device. vaso-occluder 104. At least the part of the central wire 137, visible in Figure 8, is coated with parylene coating 139. The distal center wire 137 in the view shown in Figure 8 may also be parylene coated as needed or desired. A laser-traced area 141 is prepared by cutting, using a laser, the parylene precoat. A suitable power ultraviolet excimer laser is appropriate. The width of the laser-traced area 141 is very narrow, typically no more than about 0.254mm (0.010 inches) preferably no more than about 0.127mm (0.005 inches). The laser-traced area 141 may be adjacent to the weld joint 114 or fused joint; this will produce a clean "tail" of the coil after it is separated. However, the laser-traced area 141 can be located anywhere in this area.

This procedure has proven to be reliable and produces consistently good gaskets with predictable separation times.

We have also found that the use of a polyfluorocarbon sprayer, e.g. eg, PTFE solids in a suitable carrier solvent, is also useful in producing an insulating layer on the center wire portion of the assembly, particularly the portion of the center wire proximal to the sacrificial gasket.

In other words, at least a portion of the distal assembly area of ​​the sacrificial joint is coated with a polymeric coating selected from one or more of the polymers listed above; the zone usually need not extend beyond the bearing or welded joint of the spiral mentioned elsewhere. The central wire area of ​​the proximal sacrificial joint assembly may also be coated with a polymeric coating of one or more of the polymers listed above; The insulating zone usually does not need to extend much further into the catheter, but it can be as well.

Figure 9 shows a typical design including the discrete sacrificial gasket 106 as generally shown above in Figure 1. In Figure 9, a more or less conventional assembly of Teflon laminated stainless steel metal guide 140^® or similarly isolated can be placed within a protective catheter. As mentioned above, the stainless steel metal guide can have a diameter of 0.254-0.762 mm (10-30 thousandths of an inch). In the aforementioned embodiment of Figure 9, the metal guide assembly 140 is tapered at its distal end to form a tapered section 142 which joins a further section 144 which extends along the length of the metal guide. 146. Section 144 gradually narrows to a smaller section 148. The guidewire assembly 140, as noted above, can be positioned within a catheter body and is typically 50-200 cm in length to the sacrificial junction 106. As shown in Figure 1, the distal section of the assembly 140 of the metal guide has an external Teflon sleeve 150^® (or cover of other suitable insulating material). In addition, it has an end plug 152 to allow the metal guide to be electrically isolated from blood except at the discrete sacrificial junction 106. The proximal end of vaso-occluder device 104 is typically a welded tip or joint 114. Preferably, vaso-occluder device 104, when a coil, forms a secondary loop upon exit from the end of the catheter.

ES 2 201 153 T3 ter. The distal end of vaso-occluder device 104 may also have an end obturator or tip to prevent punctures of the aneurysm as it is inserted into the aneurysm sac.

As mentioned, the spiral or vasoocclusive device 104 may be pre-beveled to form a cylinder or conical shell. However, vaso-occluder device 104 is extremely soft and its overall shape can easily deform. When inserted into the catheter (not shown), vaso-occluder device 104 easily straightens such that it is positioned axially within the catheter. Once ejected from the catheter tip, the vaso-occluder device 104 may take the shape shown in Figure 9 or it may be loosely deformed to fit the interior shape of the aneurysm.

Figure 10 shows the placement of the devices of the invention shown above within a vessel 156 with the catheter tip 158 positioned near the neck 160 of the aneurysm 162. The vaso-occluder device 164 is inserted into the aneurysm 162 at least until sacrificial junction 106 is outside the distal tip of catheter 158. A positive electrical current of approximately 0.012 mA at 0.1-6 volts is applied to wire guide 166 to form a thrombus within aneurysm 162. Negative pole 168 of power supply 170 is typically located in electrical contact with the skin. .

After the thrombus has formed and the aneurysm has occluded, vaso-occluder device 164 is separated from metal guide 166 by electrolytic disintegration of the sacrificial junction 106.

After the sacrificial gasket 106 is dissolved at least for the most part by electrolytic action, typically in less than two minutes, more frequently in less than a minute, the wire guide 166 and catheter 158 are withdrawn from vessel 156, leaving the occluded aneurysm as shown in figure 11.

The process is typically performed under fluoroscopic control under local anesthesia. A transfemoral catheter is used to treat a brain aneurysm and is usually inserted into the groin. When the vaso-occluder device 164 is made of platinum, it is not affected by electrolysis. When the wire guide and relevant parts of the support coils at the distal tip of the wire guide are suitably coated with insulating coatings, only the exposed portion of the sacrificial gasket 106 is affected by electrolysis.

It should be understood that the shape of the tip of the platinum distal coil used in combination with the metal guide according to the invention can be supplied in a variety of shapes and shells.