Occlusive device delivery system with mechanical detachment

A delivery system for an embolic coil including a delivery tube having a lumen. A proximal coil junction is disposed between the delivery tube and the embolic coil. Insertable through the lumen and extending proximally beyond the proximal end of the delivery tube is a detachable wire with a terminating feature disposed on its distal end. At least one stretch resistant member is disposed within a lumen formed by the embolic coil. A distal end of each of the at least one stretch resistant members is secured to a distal end of the embolic coil, while each of the at least one stretch resistant members is also secured proximate the proximal end of the embolic coil. The distal end of the delivery tube is retained by the wire physically against without being attached in any way to the proximal junction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to occlusive devices (e.g., embolic coils) for implantation within a blood vessel of a body. In particular, the present invention relates to an improved mechanical detachment for an embolic coil delivery system in the treatment of blood vessel disorders.

2. Description of Related Art

Vascular disorders and defects such as aneurysms and other arterio-venous malformations are especially difficult to treat when located near critical tissues or where ready access to malformation is not available. Both difficulty factors apply especially to cranial aneurysms. Due to the sensitive brain tissue surrounding cranial blood vessels and the restricted access, it is very challenging and often risky to surgically treat defects of the cranial vasculature.

Alternative treatments include vasculature occlusion devices, such as embolic coils, deployed using catheter delivery systems. In such systems used to treat cranial aneurysms, the distal end of an embolic coil delivery catheter is inserted into non-cranial vasculature of a patient, typically through a femoral artery in the groin, and guided to a predetermined delivery site within the cranium.

Multiple embolic coils of various lengths, generally approximately 1 cm to approximately 30 cm, and preselected stiffness often are packed sequentially within a cranial aneurysm to limit blood flow therein and to encourage embolism formation. Typically, physicians first utilize stiffer coils to establish a framework within the aneurysm and then select more flexible coils to fill spaces within the framework. Ideally, each coil conforms both to the aneurysm and to previously implanted coils. Each successive coil is selected individually based on factors including stiffness, length, and preformed shape which the coil will tend to assume after delivery.

During implantation, the physician manipulates each embolic coil until it is in a satisfactory position, as seen by an imaging technique such as fluoroscopic visualization, before detaching the coil from the delivery system. It is beneficial for both ends of each coil to remain positioned within the aneurysm after delivery; otherwise, a length of coil protruding into the main lumen of the blood vessel invites undesired clotting external to the aneurysm. After each successive coil is detached, the next coil is subject to an increasing risk of becoming entangled in the growing mass of coils, thereby restricting the depth of insertion for that coil into the aneurysm.

Difficulties may arise due to stretching of the embolic coils during repositioning or attempted retrieval of the coils, especially if the coil becomes entangled and complete insertion of the coil into the aneurysm is not accomplished. If pulling forces applied to a coil exceed its elastic limit, the coil will not return to its original shape. A stretched coil exhibits diminished pushability or retractability, and becomes more difficult to manipulate into an optimal position or to be removed. Moreover, a stretched coil occupies less volume than an unstretched coil, which increases the number of coils needed to sufficiently pack the aneurysm to encourage formation of a robust embolus positioned wholly within the aneurysm. To avoid such problems stretch resistance devices are used, such as that disclosed in U.S. Pat. No. 5,853,418, herein incorporated by reference in its entirety, having a primary coil and an elongated stretch-resisting member fixedly attached to the primary coil in at least two locations.

In order to deliver the vaso-occlusive coils to a desired site, e.g., an aneurysm, in the vasculature, it is well-known to first position a small profile, delivery catheter or micro-catheter at the targeted site using fluoroscopy, ultrasound, or other method of steerable navigation. A delivery or “pusher” wire is then passed through a proximal end of the catheter lumen, until a vaso-occlusive coil coupled to a distal end of the pusher wire is extended out of the distal end opening of the catheter and into the blood vessel at the targeted site. The vaso-occlusive device is then released or detached from the end pusher wire, and the pusher wire is withdrawn in a proximal direction back through the catheter. Depending on the particular needs of the patient, another occlusive device may then be pushed through the catheter and released at the same site in a similar manner.

Several conventional methods are used to detach the wire from the embolic coil once it has been properly positioned at the targeted site in the blood vessel. One known way to release a vaso-occlusive coil from the end of the pusher wire is through the use of an electrolytically severable junction, which is an exposed section or detachment zone located along a distal end portion of the pusher wire. The detachment zone is typically made of stainless steel and is located just proximal of the vaso-occlusive device. An electrolytically severable junction is susceptible to electrolysis and disintegrates when the pusher wire is electrically charged in the presence of an ionic solution, such as blood or other bodily fluids. Thus, once the detachment zone exits out of the catheter distal end and is exposed in the vessel blood pool of the patient, a current applied to the conductive pusher wire completes a circuit with an electrode attached to the patient's skin, or with a conductive needle inserted through the skin at a remote site, and the detachment zone disintegrates due to electrolysis.

One disadvantage of occlusive devices that are deployed using electrolytic detachment is that the electrolytic process requires a certain amount of time to elapse to effectuate release of the occlusive element. This time lag is also disadvantageous for occlusive delivery devices that utilize thermal detachment such as that described in U.S. Pat. No. 6,966,892, which is herein incorporated by reference in its entirety.

Another conventional detachment technique during delivery of a vaso-occlusive device involves the use of fluid pressure (e.g., hydraulic detachment) to release an embolic coil once it is properly positioned, as described in U.S. Pat. Nos. 6,063,100 and 6,179,857, each of which is herein incorporated by reference in their entirety.

The main problems associated with current detachment schemes are reliability of detachment, speed of detachment, convenience of detaching mechanism (e.g., hydraulic detachment requires a high pressure syringe, while electrolytic detachment requires a battery operated box), and length/stiffness of the distal section.

It is therefore desirable to develop an improved mechanical detachment for an embolic coil delivery system that solves the aforementioned problems associated with conventional devices.

SUMMARY OF THE INVENTION

An aspect of the present invention relates to an improved mechanical detachment system for delivery of an embolic coil that is simpler, more reliable, quicker, more convenient and having shorter stiff sections than that in conventional mechanical detachment systems.

Another aspect of the present invention is directed to a delivery system for an embolic coil including a delivery tube having a lumen defined axially therethrough. A proximal coil junction is disposed between the delivery tube and the embolic coil. Insertable through the lumen and extending proximally beyond the proximal end of the delivery tube is a detachable wire having a terminating feature disposed on its distal end. At least one stretch resistant member is disposed within a lumen formed by the embolic coil. A distal end of each of the at least one stretch resistant members being secured to a distal end of the embolic coil, while each of the at least one stretch resistant members is also secured proximate the proximal end of the embolic coil. The distal end of the delivery tube is retained by the wire physically against without being attached in any way to the proximal junction.

Yet another aspect of the present invention relates to a delivery system for an embolic coil including a delivery tube having a lumen defined axially therethrough. A proximal coil junction is disposed between the delivery tube and the embolic coil. The proximal coil junction is a joint made out of at least one of an adhesive, an epoxy and/or a polymer; and wherein a strength of the adhesive or epoxy, as well as a durometer of the polymer used for the joint is less than a buckling strength of the delivery tube. Insertable through the lumen and extending proximally beyond the proximal end of the delivery tube is a detachable wire having a terminating feature disposed on its distal end. At least one stretch resistant member is disposed within a lumen formed by the embolic coil. A distal end of each of the at least one stretch resistant members being secured to a distal end of the embolic coil, while each of the at least one stretch resistant members is also secured proximate the proximal end of the embolic coil. The distal end of the delivery tube is retained by the wire physically against without being attached in any way to the proximal junction.

Still another aspect of the present invention is directed to a method of using the delivery system in accordance with the preceding paragraph including the steps of pulling the proximal end of the wire with a sufficient predetermined force until either: (i) the terminating feature pulls out from the joint; or (ii) the wire severs at a targeted mechanically weakened section. Then the embolic coil is releasable from the wire.

While still another aspect of the present invention is directed to a delivery system for an embolic coil including a delivery tube having a lumen defined axially therethrough. A proximal coil junction is disposed between the delivery tube and the embolic coil. Insertable through the lumen and extending proximally beyond the proximal end of the delivery tube is a detachable wire having a terminating feature disposed on its distal end. At least one stretch resistant member is disposed within a lumen formed by the embolic coil. A distal end of each of the at least one stretch resistant members being secured to a distal end of the embolic coil, while each of the at least one stretch resistant members is also secured proximate the proximal end of the embolic coil. The distal end of the delivery tube is retained by the wire physically against without being attached in any way to the proximal junction. A coil connecting member is threaded through the terminating feature and secured to the proximal coil junction.

And yet another aspect of the present invention is directed to a method of using the delivery system in accordance with the preceding paragraph including the steps of pulling the proximal end of the wire with a sufficient predetermined force until the coil connecting member severs where it is threaded through the terminating feature. Then the embolic coil is releasable from the wire.

And in still another aspect of the present invention. The delivery system for an embolic coil includes a delivery tube having a lumen defined axially therethrough. A proximal coil junction is disposed between the delivery tube and the embolic coil. Insertable through the lumen and extending proximally beyond the proximal end of the delivery tube is a detachable wire having a terminating feature disposed on its distal end. The proximal coil junction comprises a two piece mating adapter including a first component secured to the distal end of the delivery tube and a second component secured to the proximal end of the embolic coil. The two-piece mating adapter has a first channel defined longitudinally therethrough for receiving therein the terminating feature of the wire and a second channel defined traverse to and intersecting with the first channel. The delivery system further includes a coil connecting member receivable in the second channel and threadable through the terminating feature of the wire. At least one stretch resistant member is disposed within a lumen formed by the embolic coil. A distal end of each of the at least one stretch resistant members being secured to a distal end of the embolic coil, while each of the at least one stretch resistant members is also secured proximate the proximal end of the embolic coil. The distal end of the delivery tube is retained by the wire physically against without being attached in any way to the proximal junction.

While yet another aspect of the present invention is directed to a method for using the delivery system in the preceding paragraph including the steps of removing the coil connecting member completely from the second channel of the two piece mating adapter and the terminating feature of the wire. Thereafter the wire is pulled in a proximal direction to separate the second component attached to the embolic coil from that of the first component attached to the delivery tube.

In yet another aspect of the present invention is directed to a delivery system for an embolic coil including a delivery tube having a lumen defined axially therethrough. A proximal coil junction is disposed between the delivery tube and the embolic coil. Insertable through the lumen and extending proximally beyond the proximal end of the delivery tube is a detachable wire having a terminating feature disposed on its distal end. At least one stretch resistant member is disposed within a lumen formed by the embolic coil. A distal end of each of the at least one stretch resistant members being secured to a distal end of the embolic coil, while each of the at least one stretch resistant members is also secured proximate the proximal end of the embolic coil. The distal end of the delivery tube is retained by the wire physically against without being attached in any way to the proximal junction. An aperture is defined longitudinally through the proximal coil junction. The terminating feature of the wire has a maximum diameter greater than a diameter of the aperture defined in the proximal coil junction forming a friction fit therebetween retaining the terminating feature of the wire therein.

While still yet another aspect of the present invention relates to a method for using the delivery system in the preceding paragraph by pulling the proximal end of the wire with a sufficient predetermined force to overcome the friction fit between the maximum diameter of the terminating feature of the wire and the aperture of the proximal coil junction. Thereafter, the wire along with its terminating feature is released from the embolic coil.

DETAILED DESCRIPTION OF THE INVENTION

The terms “proximal”/“proximally” and “distal”/“distally” refer to a direction closer to or away from, respectively, an operator (e.g., surgeon, physician, nurse, technician, etc.) who would insert the medical device into the patient, with the tip-end (i.e., distal end or leading end) of the device inserted inside a patient's body. Thus, for example, a “proximal direction” would refer to the direction towards the operator, whereas “distal direction” would refer to the direction away from the operator towards the leading or tip-end of the medical device.

FIG. 1Ais a cross-sectional view of a first exemplary mechanical detachment system for delivery of an embolic coil in accordance with the present invention. The detachment system5includes a flexible delivery tube10(e.g., hypotube, or catheter) having a proximal end15, an opposite distal end20and a lumen25defined axially therethrough. Tube10may be either a single integral construction or otherwise multiple components or sections such as a proximal section made of a first material (e.g., stainless steel) and a flexible distal section made of a second material (e.g., Nitinol), different from that of the first material, and connected to the proximal section of the tube.

A plurality of slits30substantially perpendicular to the longitudinal direction are defined in the tube10in a discontinuous, interrupted configuration to retain the integrity of the distal flexible section while enhancing flexibility and minimizing compression/buckling of the delivery tube when the wire is pulled proximally therefrom. Factors such as the arrangement, number and spacing between slits30determines the level or degree of stiffness/flexibility of the tube10. In the case of the tube10configured as multiple components or sections, the interrupted slits30are defined only in the distal section of the tube10. These interrupted slits30minimize the axial compression of the tube during actuation of the detachment system5.

An open proximal end of an occlusive device, typically a helical embolic coil35formed by a series of loops/windings defining a coil lumen65, is attached to the distal end20of the tube10by a proximal coil junction50(e.g., a relatively low strength and/or relatively low durometer adhesive, epoxy or polymer joint. That is, the relatively low strength of the epoxy/adhesive, or the relatively low durometer of the polymer used to fill that junction (which is related to its tear-out strength) is preferably less than the buckling strength of the delivery tube. Opposite its open proximal end40, a distal end45of the embolic coil35is closed off by a distal bead55. One or more stretch resistant (SR) members60, e.g., suture filaments, disposed in the coil lumen65provide stretch resistance when excessive pulling forces are applied to the embolic coil35during implantation in a patient. Preferably, each stretch resistant member60extends longitudinally the entire length of the coil lumen65from its proximal end40to its distal end45to minimize excessive elongation. In an embodiment of the present invention depicted inFIG. 1A, each stretch resistant suture filament60is threaded through the coil lumen65with its proximal end looped around an open proximal coil loop/winding of the embolic coil35and its opposite distal end is secured to the distal end45(e.g., distal bead55) of the embolic coil35. An alternative embodiment is shown inFIG. 1B, which differs from that inFIG. 1A, in that the proximal end of each stretch resistant suture filament60is embedded into the proximal coil junction50disposed between the tube10and embolic coil35, rather than looped in an open proximal winding of the embolic coil35.

Referring toFIG. 1C, is an enlarged view of an exemplary wire70having a free proximal end75and an opposite end with a distal terminating feature80(e.g., a closed shape (loop, lasso or ring) or an open shape (hook)). Wire70is freely movable through the lumen25of the delivery tube10with the distal terminating feature80secured within the proximal end of the proximal coil junction50(e.g., epoxy or adhesive joint) joining the delivery tube10to the embolic coil35. Wire70has a length that exceeds that of the tube10in a longitudinal direction so that its proximal end75extends proximally beyond the proximal end15of the tube10. Once the embolic coil35has been properly positioned at a desired location in a blood vessel, the embolic coil35is detachable from the delivery tube10by proximally pulling its free proximal end75until the terminating feature80disposed at its opposite end becomes detached/separates/pulls out from the proximal coil junction50(e.g., adhesive joint) thereby releasing the embolic coil35at the targeted site within the blood vessel. Instead of dislodging the terminating feature80from the adhesive proximal coil junction50, wire70may be designed to have a mechanically weakened section85(typically a section of wire having a reduced cross-section relative to the remaining part of the wire). Upon application of a predetermined force on the proximal end75of the wire70in the proximal direction, the wire70will separate at the location of the weakened section85thereby releasing the embolic coil (together with the proximal coil junction and distal terminating feature of the wire secured to the embolic coil). The degree of force required to separate the wire at the weakened section85depends on one more of factors including material selection and/or cross-sectional reduction in diameter.

An alternative embodiment is depicted in the sequential illustrations depicted inFIG. 2A-2Cin which the embolic coil is secured to the distal terminating feature of the wire via the proximal ends of SR members being threaded therethrough. Specifically, the wire270is introduced into the proximal end of the lumen225until its distal terminating feature280(closed shape (loop, lasso or ring) or open shape (hook)) is disposed between the distal end220of the delivery tube210and the proximal coil junction250. Once the wire270is properly positioned, the distal terminating feature280is secured, e.g., via an adhesive or epoxy, to the distal end220of the delivery tube210at an attachment point295, as shown inFIG. 2A. In contrast to the proximal coil junction50inFIG. 1A, the proximal coil junction250inFIG. 2Ais a mechanical structure having an opening defined axially therethrough. A distal end of each SR member260is secured to the distal bead255at the distal end of the embolic coil235. An intermediate section of each SR member260is secured (e.g., via an adhesive or epoxy) to the embolic coil235proximate its proximal end (i.e., proximate the proximal junction250). An opposite proximal end of each SR member260passes through the opening defined axially through the proximal coil junction250and is threaded through the distal terminating feature280.

In this embodiment depicted inFIGS. 2A-2D, proximal coil junction250has a multi-functional purpose of: (i) securing the SR members260to the embolic coil235; (ii) minimizing any slack on the SR members260between the proximal coil junction250and the distal terminating feature280; and (iii) retaining the stretch resistance characteristics of the embolic coil235post detachment from the wire270.

Detachment of the embolic coil235from the wire270is realized by pulling the proximal end of the wire270in a proximal direction, as identified by the arrow inFIG. 2B, until a mechanical severing occurs at one of: (i) the weakest point along the wire270, (ii) the attachment point295, or (iii) along the SR member260thereby releasing the embolic coil235, as shown inFIG. 2C. As previously noted, mechanical failure may be targeted to a predetermined weakened point (e.g., reduced diameter) disposed at a desired location along the wire270, SR member260or at the attachment point295.

InFIG. 2A, embolic coil235is attached to the wire270via SR member260being threaded through the terminating feature280(e.g., closed loop). Independent of the SR member260, the proximal end of the embolic coil235may, alternatively, be attached to the distal end of the wire270via a separate coil connecting member297(preferably U-shaped) that is threaded through the distal terminating feature280and secured within the proximal coil junction250, as shown inFIG. 2D. Coil connecting member297may be made of a polymer or any other material that breaks at forces less than those required to break the distal terminating feature280or to buckle the slotted delivery tube210. Also secured within the proximal coil junction250is the proximal end of each of the SR members260. Of course, the SR members260could otherwise be secured in place by threading its proximal ends through an open primary winding of the embolic coil235(as depicted inFIG. 1A).

In still a further variation of the embodiment shown inFIG. 2E, a two piece mating adapter290may be used to connect the distal end of the delivery tube210and the proximal end of the embolic coil235. In the exemplary embodiment illustrated inFIG. 2E, mating adapter290includes a first component291mounted to the distal end of the delivery tube210and a second component292mounted to the proximal end of the embolic coil235. The adapter290has a first channel293defined longitudinally therein. A second channel294is defined transverse therethrough the adapter290and intercepts that of the first channel293. Detachment wire270is introduced into the first channel291of the adapter290until its distal terminating feature280(e.g., a lasso, loop, ring or any other substantially closed shape) is substantially aligned with the second channel294. A coil connecting member297(e.g., a pin or rod) is then threaded through the second channel294and passes through the distal terminating feature280. The coil connecting member297is made of a polymer or other material which breaks or separates at forces lower than the forces required to break the distal terminating feature280. Detachment of the embolic coil235is achieved by pulling the proximal end of the wire270in a proximal direction until the coil connecting member297severs releasing the embolic coil235at its desired location within a blood vessel.

In the second embodiment depicted inFIG. 2A, the distal terminating feature280extends from the distal end of the delivery tube10but does not pass through the proximal coil junction250. In a third embodiment of the embolic coil delivery system in accordance with the present invention as shown inFIGS. 3A-3E, distal terminating feature380of the wire370is sized and shaped to be restrained by an interference, press or friction fit within the aperture396defined axially through the proximal coil junction350. One possible configuration for the distal terminating feature380, as illustrated in the figures, is a triangle tapered longitudinally with its distal end having a maximum diameter greater than its proximal end. Specifically, the maximum diameter of the distal terminating feature380is greater than the aperture396defined in the proximal coil junction330restraining it via an interference, press or friction fit from passing freely therethrough, except upon the application a predetermined pulling force on the wire in a proximal direction. The force required to pull the distal terminating feature380from the aperture396of the proximal coil junction330depends on such factors as the materials of each and the dimension interference therebetween. Taking such factors into consideration, a pull-out force is provided that is less than the buckling strength of the delivery tube310, but greater than typical manipulation forces exerted on the embolic coil235during placement.

The proximal coil junction350is adhered to the proximal end of the embolic coil335. In turn, the embolic coil335is secured to the distal end of the wire370by an interference fit between distal terminating feature380and the interior surface of aperture396defined in the proximal coil junction350. Prior to being introduced into a blood vessel, at least that portion of distal terminating feature380having its maximum diameter is preferably disposed within the lumen365of the embolic coil335beyond the distal end of the proximal coil junction350in a distal direction, as shown inFIG. 3A. It is also contemplated and with the intended scope of the present invention for at least that portion of distal terminating feature380having its maximum diameter be disposed only within the aperture396(without extending into the coil lumen365) of the proximal coil junction335as long as the provided pull-out force of the wire370in a proximal direction from that position exceeds typical manipulation forces during placement of the embolic coil335. An enlarged partial view of the interference, press or friction fit between the feature380and the interior surface of the lumen365of the embolic coil335is depicted inFIG. 3B. To insure an interference, press or friction fit the maximum diameter of the distal terminating feature380is greater than an inner diameter of the aperture396of the proximal coil junction350.

Detachment of the embolic coil335is achieved by pulling the proximal end of the wire370in a proximal direction with a predetermined sufficient force required to overcome the interference, press or friction fit of the distal terminating feature380with the aperture396of the proximal coil junction350allowing the distal terminating feature380to pass therethrough, as illustrated inFIG. 3C. Further pulling in a proximal direction on the wire370allows it to pass completely through the lumen325defined in the delivery tube310, as shown inFIG. 3D, releasing the embolic coil335together with the proximal coil junction350. In the exemplary embodiment shown inFIG. 3A, the proximal end340of the embolic coil335is attached to the distal end320of the delivery tube310via the proximal coil junction350(e.g., relatively low strength adhesive or epoxy joint) and the proximal ends of the SR members360are looped around an open proximal winding of the embolic coil335. As an alternative configuration, inFIG. 3Ethe proximal end340of the embolic coil335is attached to a separate intermediate coil junction397which, in turn, is connected to the delivery tube310via the proximal coil junction350. In this configuration the proximal ends of the SR members360are secured directly to the intermediate coil junction395(e.g., via an adhesive or epoxy).

Rather than completely removing the wire370(including its distal terminating feature380) from the embolic coil335, alternatively, a mechanically weakened section may be provided at a targeted location along the wire370to promote separation thereof upon applying a sufficient predetermined force.FIG. 3Fis an enlarged view of the wire370ofFIG. 3Awith a targeted mechanically weakened section385to allow separation of the wire securing the coil at the targeted location. When the embolic coil is released from the delivery device, at least the distal terminating feature380remains in the aperture396of the proximal coil junction350. The predetermined force necessary to separate the wire370at its targeted mechanically weakened section385is based on the material selection and/or cross-sectional reduction of the mechanically weakened section of the wire.

The present invention has been shown and described for delivery and detachment of an embolic coil. Other occlusive devices are contemplated and within the scope of the present invention.

Every issued patent, pending patent application, publication, journal article, book or any other reference cited herein is each incorporated by reference in their entirety.