Pusher arm and ball release mechanism for embolic coils

Abstract

The present invention relates to a release mechanism for medical implants, particularly embolic coils and the like, which utilizes a bulbous element and a receiving element for constraining the bulbous element. In some cases, the receiving element is sized and shaped to facilitate axial and / or radial constraining of the bulbous element and may cooperate with a constraining element and / or a release wire that may be selectively movable independently of the receiving element.

Description

[0001] priority

[0002] This application claims the benefit of priority under 35 USC §119 to U.S. Provisional Patent Application Serial No. 62 / 237,904, filed on October 6, 2015, the entire contents of which are incorporated herein by reference and for all purposes. Technical Field

[0003] The present application relates to the field of medical devices and medical procedures. More specifically, the present application relates to devices and methods for occluding body lumens, such as blood vessels. Background Art

[0004] The therapeutic embolization or occlusion of blood vessels can be used to treat a variety of vascular and non-vascular conditions, including cerebral and peripheral arterial aneurysms, arteriovenous malformations, uterine fibroids and various tumors. A common agent for embolizing blood vessels is an embolic coil, which is a permanently implanted winding structure that, when implanted in a blood vessel, occludes the blood vessel by causing thrombosis at its location. In order to be assembled into vascular structures of different sizes and occlude them, the embolic coil can have different lengths and / or cross-sectional diameters. In use, the coil is transported through a microcatheter (e.g., in order to be assembled in a 3Fr catheter lumen) in an elongated form with a narrow diameter. Once deployed in a blood vessel, the coil can present a complex 3-D shape, such as a spiral, helical, J-shaped or bird's nest shape, and can include thrombotic fibers or fiber bundles along its length. The embolic coil is highly flexible and can be transported through narrow or tortuous vascular structures, but when a relatively large vascular structure needs to be occluded, multiple coils may be required to achieve complete occlusion.

[0005] These coils are usually placed at the desired position using a catheter and a pusher. First, the position is approached by a catheter. In the treatment of peripheral or neurological disorders that require occlusion, the position is approached with a flexible small-diameter catheter, which can be guided to the position by using a guide wire and / or a guide tool (such as a balloon) at the distal end of the catheter. Once the position has been approached, the catheter lumen is cleared (i.e., if a guide wire has been used, the guide wire is removed), and the coil is placed at the proximal end of the catheter and pushed through the catheter with a pusher. When the coil reaches the distal end of the catheter, it is pushed into the blood vessel and unfolded. This technology of inserting the coil from the distal end of the catheter has undesirable limitations. First, due to the insertion action of the pusher during deployment, the positioning of the coil at the position cannot be controlled to an excellent degree of accuracy. Secondly, once the self-catheter is inserted, it is difficult to reposition or retrieve the coil if necessary. In fact, another device called a retriever must be passed through the catheter to circle the coil to reposition or retrieve it.

[0006] The coil is typically connected to a pusher or another structure within the catheter and must be detached. This detachment is typically facilitated by using an electrolytically severable connection or a mechanical coupling. While current detachment mechanisms are generally reliable, they may not release the coil when triggered 100% of the time. In particular, in the case of a mechanical detachment mechanism, improving the reliability of the detachment may involve undesirable tradeoffs, such as increasing the size and / or cost of the components used in the detachment mechanism. Summary of the invention

[0007] The present invention, in its various aspects, provides an improved mechanical coil separation system that achieves 100% separation and minimizes the tradeoff between 100% separation and increased size and / or expense.

[0008] In one aspect, the present invention relates to a system for treating a patient, comprising a catheter defining an inner lumen; a pusher assembly slidably disposed within the inner lumen; a constraining element slidably disposed within the inner lumen and movable independently of the pusher assembly, the constraining element having a tubular distal end that can be disposed about a distal portion of the pusher assembly; and an embolic coil having a proximal end that includes a bulbous element. In a preferred embodiment, the pusher assembly includes a distal receiving element having a first portion defining a radially extending first planar surface and a second portion defining an elongated planar surface substantially perpendicular to the planar surface and extending distally therefrom, the elongated planar surface having a protrusion extending away from the planar surface. In some embodiments, the inner diameter of the tubular distal end of the constraining element has a close tolerance to the combined outer diameter of the bulbous element of the embolic coil and the second portion of the distal receiving element (e.g., in some cases, the inner diameter is no greater than (a) the outer diameter of the bulbous element of the embolic coil plus (b) 133% of the thickness of the second portion of the distal receiving element). Similarly, in some embodiments, the protrusion extends from the elongated flat surface a distance that is less than 50% of the diameter of the bulbous element. More generally, in certain embodiments, the combination of the extension of the protrusion from the elongated flat surface and the second portion of the distal receiving element (i.e., the combined thickness) is greater than or equal to the difference between the inner diameter of the tubular distal end of the constraining element and the combined outer diameter of the bulbous element and the second portion of the distal receiving element of the embolic coil. In some cases, the bulbous element is connected to the embolic coil via one of a wire and a rod extending axially along the central axis of the coil, and wherein the wire or rod extends axially along the central axis of the embolic coil when the bulbous element and the receiving element are engaged and disposed within the lumen of the tubular distal end of the constraining element. The constraining element and the pusher assembly can be arranged within the lumen in several different ways to allow smooth catheter operation and / or minimize the possibility of mechanical interference between those components. For example, in some cases, the restraining element includes a wire or rod disposed proximally of the tubular distal end, the wire or rod extending parallel to the pusher assembly, and in this case the pusher assembly is coaxially disposed in the catheter lumen. In other cases, the restraining element includes a coiled segment disposed proximally of the tubular distal end, and in this case the pusher assembly is coaxially disposed in the lumen defined by the coiled segment. In other cases, the restraining element includes a wire or rod disposed proximally of the tubular distal end and coaxially disposed in the catheter lumen, and the pusher assembly includes an elongated portion extending parallel to the wire and through a proximal hole in the tubular distal end. In various cases, the distal receiving element is a single piece. In a preferred case, the embolic coil is fixed to the catheter by contacting a bulbous element and a distal receiving element and advancing the restraining element at least partially onto the bulbous element and the distal receiving element, and optionally, the coil is released by moving at least one of the pusher assembly and the restraining element relative to the other.In some cases, the pusher assembly and constraining element can be retracted from the catheter and replaced with the pusher assembly and constraining element in combination with a second embolic coil.Systems according to this aspect can be used in medicine, for example, for treatment of vascular disorders and can be included in kits for use by medical personnel.

[0009] In another aspect, the present invention is directed to a system for treating a patient, comprising a catheter defining a first lumen, a pusher assembly slidably disposed within the first lumen and having a tubular distal element defining a second lumen, the tubular distal element including a slot formed in a wall thereof; a release wire slidably disposed within the first lumen and movable independently of the pusher assembly; and an embolic coil having a proximal end including a bulbous element. In various embodiments according to this aspect, the tubular distal end has an inner diameter that is less than the combined diameter of the bulbous element plus the diameter of the release wire, and wherein the release wire is disposed (i.e., it can be positioned) proximate to an inner wall of the tubular distal element opposite the slot to cause the bulbous element to be displaced into the slot. In some cases, the pusher assembly can include a wire or rod disposed proximal to the tubular distal end and coaxially disposed within the lumen of the catheter, in which case the release wire extends parallel to the pusher assembly, or the pusher can include a coiled segment disposed proximal to the tubular distal end, in which case the release wire can be coaxially disposed within the lumen defined by the coiled segment.

[0010] In another aspect, the present invention is directed to a method of treating a patient by inserting into the patient a catheter having a pusher assembly, a distal receiving element, a restraining element, and an embolic coil having a bulbous element as described above. Once inserted, at least one of the pusher assembly and the restraining element is moved relative to the other, thereby allowing the bulbous element to separate from the distal receiving element. As described above, in some cases, the inner diameter of the tubular distal end of the restraining element is no greater than 133% of the outer diameter of the bulbous element of the embolic coil plus the thickness of the second portion of the distal receiving element, the protrusion extends from the elongated flat surface a distance that is less than 50% of the diameter of the bulbous element, and / or the combination of the extension of the protrusion from the elongated flat surface and the second portion of the distal receiving element is greater than or equal to the difference between the inner diameter of the tubular distal end of the restraining element and the combined outer diameter of the bulbous element of the embolic coil and the second portion of the distal receiving element. The bulbous element can be connected to the embolic coil by one of a wire and a rod extending axially along the central axis of the coil, so that when the bulbous element and the receiving element are engaged and disposed in the lumen of the tubular distal end of the constraining element, the wire or rod extends axially along the central axis of the embolic coil. The method can also include the step of retracting the pusher assembly and can also include the step of retracting the constraining element before retracting the pusher assembly. In some cases, the pusher assembly and the constraining element are retrieved from the catheter, and the pusher assembly and the constraining element engaged with the bulbous element of the second embolic coil are reinserted into the catheter. Finally, in some cases, the method includes positioning at least a portion of the embolic coil within the vascular structure to be occluded. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Various aspects of the present invention are described below with reference to the accompanying drawings, wherein like numerals represent like elements, and wherein:

[0012] Figure 1 A schematic diagram of a delivery catheter according to some embodiments of the present invention is shown;

[0013] Figure 2A , 2B and 2C show the three points in the separation process Figure 1 Schematic diagram of the catheter;

[0014] Figure 3 Shown as used Figure 1 Schematic diagram of a receiving element in a delivery catheter of 2;

[0015] Figure 4A , B, C, D, E and F illustrate in schematic form various alternative configurations of delivery catheters according to embodiments of the present invention.

[0016] The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention unless otherwise provided in the following description. DETAILED DESCRIPTION

[0017] As in Figure 1 As shown in , an exemplary catheter assembly 100 includes a generally tubular catheter 105, an embolic coil 110 having a ball or other bulbous element 111 at its proximal end (although any other similarly sized implantable medical device may also be used), a pusher assembly 115 slidably disposed within the catheter 105 and having a receiving element 116 at its distal end that is sized to engage the ball 111. The catheter assembly 100 also includes a restraining element 120 that is slidable within the catheter lumen independently of the pusher assembly 115 and that restrains the axial or radial movement of the ball 111 when it engages the receiving element 116.

[0018] exist Figure 1 The restraining element 120 shown in FIG. 2 has a generally tubular distal end and has an inner diameter slightly larger than the combined width of the ball 111 and the receiving element 115 when they are engaged (e.g., 10%, 20%, 30%, 40%, or 50% larger). Together with the lip or ridge 116a on the receiving element, the restraining element 120 helps limit the axial and radial movement of the ball 111 when the ball 111 is engaged with the receiving element 116 and contained within the lumen of the restraining element 120. This arrangement is shown in FIG. Figure 2A and is used to advance coil 110 through the distal end of catheter 105.

[0019] like Figure 2B As shown, when the coil 110 is advanced through the distal end of the catheter 105, the restraining element 120 remains positioned over the ball 111 and the receiving element 116 of the pusher assembly 115, which allows the coil 110 to be placed before it is released. When it is desired to release the coil, the restraining element 120 is retracted onto the pusher assembly 115, or alternatively, the pusher assembly 115 is advanced through the restraining element 120; in either case, the ball 111 is exposed ( Figure 2C ), thereby releasing the embolic coil 110.

[0020] exist Figure 1 The catheter assembly 100 shown in FIG. 2 has several advantageous features, including but not limited to the following: it is 100% removable, yet it still allows the user to recapture the coil 110 by engaging the receiving element 116 with the ball 111 and advancing the restraining element 120 over both. At the same time, the simple design has a small overall diameter that will tend to maintain the flexibility of the catheter assembly 100 and can be implemented using materials currently used to produce delivery catheters.

[0021] Now turn to Figure 3, the exemplary receiving element 116 includes a proximal axial constraint surface 116b and a radial constraint surface 116c, which in turn includes a ridge or lip 116a at its distal end for further constraining the ball 111 and thereby limiting axial movement of the coil 110 as the constraining element 120 extends over the ball 111 and the receiving element 116. Each of the proximal axial constraint surface 116b, the radial constraint surface 116c, and the lip or ridge 116a are generally continuous with one another (so that the receiving element 116 can be made in one piece) and preferably have relatively flat (in the case of the radial and axial constraint surfaces) and uniform surfaces.

[0022] exist Figure 3 The receiving element 116 shown in is superficially similar to the design of Engelson disclosed in U.S. Pat. No. 5,261,916 (the entire contents of which are incorporated herein by reference and available for all purposes), but skilled artisans will appreciate that Engelson used a pusher with an enlarged cylindrical tip having an axial hole and radial slots to receive the ball of the embolic coil so that the coil is constrained proximally and distally by a body having a diameter equal to or greater than the diameter of the ball. However, in Figures 1 to 3 In an embodiment, the lip 116a is significantly smaller than the diameter of the ball 111. For example, in one case, the ball 111 has a diameter of approximately 0.012" (0.30mm), and the lip or ridge 116a may have a convex curve with a radius of 0.0035" (0.09mm). More generally, the lip 116a preferably extends a distance equal to or preferably slightly greater than the difference between the inner diameter of the constraining element 120 and the combined outer diameter of the receiving element 116 and the ball 111 when both are engaged. This configuration limits radial displacement of the ball 111 and the proximal end of the embolic coil 110 during delivery, which facilitates accurate placement of the coil 110 with a relatively low risk of coil movement during release. At the same time, the distance is not so great as to reduce the mechanical clearance of the ball 111 or the connector between the ball 111 and the coil 110 when they are engaged with the receiving element 116 and the constraining element 120.

[0023] Although the embodiments given above illustrate certain aspects of the present invention, the scope of the present invention is not limited to these aspects. Figure 1 , 2 and 3 as a cylindrical body having constant inner and outer diameters and extending the entire length of the catheter assembly 100. This arrangement has the advantages described above, but the resulting catheter assembly 100 may be relatively stiff because the constraining element is preferably robust to deformation or "ovalization" that could potentially allow the ball 111 to migrate during delivery.

[0024] In situations where embolic coils are delivered through curved and / or narrow diameter vessels, a more flexible catheter may be desired; this is accomplished in various embodiments by varying the diameter, length, or rigidity of the constraining element 120 along the length of the catheter assembly 100. For example, in some cases, the diameter of the constraining element 120 is maximized at its distal end to surround the ball 111 and receiving element 116, and then decreases proximally. Alternatively, the distal portion of the constraining element 120 can be made stiffer than the proximal portion (e.g., by greater wall thickness, the addition of rigid materials such as reinforcing fibers or braids, or a rigid sleeve), which allows the distal end to resist ovalization while the proximal end remains flexible. Furthermore, in Figure 4A In another alternative shown in FIG. 1B , the distal restraining element 120 has a length that is significantly less than the catheter 105 and is connected at its proximal end to a wire or other structure 121 that enables the restraining element 120 to be pushed or pulled relative to the catheter 105 and / or the pusher assembly 115. Figures 1 to 3 In the embodiment shown in , the restraining element 120 and the pusher assembly are arranged coaxially along substantially the entire length of the catheter assembly 100 (ie, the pusher assembly 115 is centered); Figure 4A In the embodiment of FIG. 1 , the wire 121 is centered and the constraining element includes an eccentric proximal hole 122 to accommodate the pusher assembly 115. Alternatively, if the pusher assembly 115 is centered, the proximal hole 122 is located more centrally and the wire 121 is eccentric, as in FIG. Figure 4B as shown in .

[0025] In addition to improved flexibility, Figure 4A The relatively short restriction element 120 shown in FIG. 1B and the embodiments described below facilitate fluid injection through the delivery catheter 105: The use of a relatively short length tubular restriction element 120 can reduce the fluid pressure required to inject the fluid through the catheter 105 by providing a relatively large inner diameter over most of its length. In contrast, when the restriction element 120 is a tube extending the entire length of the catheter 105, the diameter of the lumen available for fluid flow decreases along the entire length of the catheter 105.

[0026] In certain embodiments, the embolic coil 110 will have a primary helical structure and a complex secondary structure, such as a spiral, an oval, a J-shape, etc., as described by Mariant et al. in U.S. Pat. No. 5,639,277, which is incorporated herein by reference for all purposes. Because the coil 110 tends to assume a secondary shape when unconstrained, it may expand when disposed within the lumen of the catheter 105, and it may twist when the coil 110 is advanced through the catheter 105. Figure 4AOne potential complication of the designs of FIG. 1B and those described below is that this twisting may cause the wire 121 to twist, potentially twisting around the pusher assembly 115. To prevent twisting of the wire 121 and the pusher assembly 115, the catheter optionally includes a restraining element, such as a small sleeve or wire loop, which limits the circumferential and / or radial movement of one or both of the wire 121 and the pusher assembly 115. These wires, sleeves, etc. are preferably positioned at multiple locations along the length of the catheter 105 to ensure that the wire 121 and the pusher assembly 115 do not mechanically interfere with each other along the length of the catheter 105 during the delivery process.

[0027] In another set of embodiments, a pusher assembly including a receiving element provides radial and axial restraint to the ball with the aid of a wire or other narrow body that pushes the ball and receiving element together. Figure 4C In Figure 4D, the catheter assembly 400 includes a catheter 405 for delivering an embolic coil 410 having a proximal ball 411, the catheter including a pusher assembly 415 having a tubular receiving element 416 having an axial hole defining an inner lumen and a slot 417 cut into the sidewall of the receiving element 416, the receiving element 416 being sized to accommodate part or all of the ball 111. The assembly also includes a release wire 420, independent of the pusher assembly 415, which is slidably disposed in the catheter 405. The release wire 420 is positioned to push the ball 411 toward the slot 417, providing axial and radial constraints to the ball 411 during delivery. As discussed above, either the pusher assembly 415 or the release wire 420 can be centered, in which case the other is eccentric. In either case, the release wire 420 and pusher assembly 415 may optionally be constrained to prevent entanglement or crossing at more than one point along the length of the catheter 405, such as by one or more wire loops, or by using a guidewire lumen or slit within the catheter 405 (not shown).

[0028] In use, the catheter assembly 400 is operated by "pull to release": to deploy the coil 410, the pusher assembly 415 and the release wire 420 are advanced distally relative to the catheter 405; once the coil is properly positioned, the release wire 420 is retracted proximally, thereby releasing the coil 410.

[0029] Now turn to Figure 4E To F, in some cases, the pusher assembly and the constraining element are coaxially arranged, with the pusher element 115 centered and extending through the hollow center portion 130 ( Figure 4E ). Or, as in Figure 4FAs shown in , the release wire 420 can extend through the hollow center portion 430 of the pusher assembly 416. The hollow center portion 130, 430 can be a coil or other suitable hollow body through which the pusher assembly 115 or the release wire 420, respectively, is slidably disposed.

[0030] As used herein, the phrase "and / or" should be understood to mean "any or all" of the elements so combined, i.e., elements that are present in combination in some cases and separately in other cases. In addition to the elements specifically identified by the "and / or" clause, other elements may optionally be present, whether related or unrelated to those specifically identified elements, unless expressly stated to the contrary. Thus, as a non-limiting example, when used in conjunction with open language such as "comprising," a reference to "A and / or B" can refer to A without B (optionally including elements other than B) in one embodiment; to B without A (optionally including elements other than A) in another embodiment; to A and B (optionally including other elements) in another embodiment; etc.

[0031] The term "consisting essentially of" means excluding other materials that contribute to the function, unless otherwise defined herein. However, these other materials may be present in minor amounts, either collectively or individually.

[0032] As used in this specification, the term "substantially" or "approximately" means plus or minus 10% (e.g., by weight or by volume), and in some embodiments, plus or minus 5%. References to "an instance," "an example," "an embodiment," or "an embodiment" throughout the specification mean that a particular feature, structure, or characteristic described in conjunction with the example is included in at least one example of the present technology. Therefore, the phrases "in an example," "in an example," "an embodiment," or "an embodiment" that appear throughout the specification do not necessarily all refer to the same example. In addition, specific features, structures, routines, steps, or characteristics may be combined in one or more examples of the present technology in any suitable manner. The titles provided herein are merely for convenience and are not intended to limit or explain the scope or meaning of the claimed technology.

[0033] Certain embodiments of the present invention have been described above. However, it is expressly pointed out that the present invention is not limited to these embodiments, but is intended to include additions and modifications to the contents explicitly described herein within the scope of the present invention. In addition, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and arrangements, even if such combinations or arrangements are not expressed herein, as long as they do not depart from the spirit and scope of the present invention. In fact, variations, modifications and other implementations of the contents described herein can be imagined by those of ordinary skill in the art without departing from the spirit and scope of the present invention. Thus, the present invention is not limited only by the foregoing illustrative description.

Claims

1. A system for treating a patient, comprising: a catheter defining an inner lumen; a pusher assembly slidably disposed within the inner cavity; a constraining element slidably disposed within the lumen, the constraining element having a tubular distal end displaceable about a distal portion of the pusher assembly; as well as an embolic coil having a proximal end including a bulbous element, wherein the pusher assembly includes a distal receiving element having an elongated planar surface having a protrusion extending away from the planar surface, the protrusion extending a distance from the elongated planar surface that is less than 50% of a diameter of the bulbous element; and wherein, when the bulbous element is engaged with the distal receiving element and contained within the tubular distal end of the constraining element, the inner diameter of the tubular distal end is no greater than 133% of the combined width of the bulbous element and the distal receiving element.

2. The system of claim 1 , wherein the extension of the protrusion from the elongated planar surface is greater than or equal to the difference between the inner diameter of the tubular distal end of the constraining element and the combined outer diameter of the bulbous element of the embolic coil and the elongated planar surface of the distal receiving element.

3. A system according to claim 1 or 2, wherein the bulbous element is connected to the embolic coil by one of a wire and a rod extending axially along the central axis of the coil, and wherein the wire or rod extends axially along the central axis of the embolic coil when the bulbous element and the receiving element are engaged and disposed within the inner cavity of the tubular distal end of the constraining element.

4. A system according to claim 1 or 2, wherein the restraining element comprises a wire or rod disposed proximal to the tubular distal end, the wire or rod extending parallel to the pusher assembly, and wherein the pusher assembly is coaxially disposed within the catheter lumen.

5. The system of claim 1 or 2, wherein the constraining element comprises a coiled segment disposed proximal to the tubular distal end, and wherein the pusher assembly is coaxially disposed within a lumen defined by the coiled segment.

6. A system according to claim 1 or 2, wherein the restraining element includes a wire or rod disposed proximal to the tubular distal end and coaxially disposed within the catheter lumen, and the pusher assembly includes a slender portion parallel to the wire and extending through a proximal hole in the tubular distal end.

7. The system of claim 1 or 2, wherein the distal receiving element is a single piece.

8. The system of claim 1 or 2, wherein the embolic coil is secured to the catheter by contacting the bulbous element and the distal receiving element and advancing the constraining element at least partially over the bulbous element and the distal receiving element.

9. The system of claim 8, wherein the embolic coil is released by moving at least one of the pusher assembly and the constraining element relative to the other.

10. The system of claim 9, wherein the pusher assembly and constraining element are retractable from the catheter and replaced with a pusher assembly and constraining element in combination with a second embolic coil.

11. System according to one of claims 1, 2, 9 and 10 for use in medicine.

12. The system according to one of claims 1, 2, 9 and 10 for use in the treatment of vascular disorders.

13. A kit for treating a patient comprising a system according to one of claims 1 to 10.

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