Surgery – Instruments
Reexamination Certificate
1998-12-15
2001-02-20
Dawson, Glenn K. (Department: 3731)
Surgery
Instruments
C606S151000, C606S200000, C606S213000
Reexamination Certificate
active
06190373
ABSTRACT:
FIELD OF THE INVENTION
This invention is a surgical instrument and specifically is a device for delivering embolic coils to a selected site within the vasculature of the human body via use of a catheter. In particular, the device involves an embolic coil having a radially enlarged member attached to one end, which coil is released by forcing the radially enlarged member axially through a distendible aperture situated on the distal end of a pusher assembly.
BACKGROUND OF THE INVENTION
The endovascular treatment of a variety of vascular maladies throughout the body is an increasingly more important form of therapy. Catheters have been used to place various treatment materials, devices, and drugs within arteries and veins in the human body. Examples of these devices and their use in such treatments are shown in U.S. patent application Ser. Nos. 07/806,898 (“Detachable Pusher-Vasoocclusive Coil Assembly with Threaded Coupling”) and 07/806,912 (“Detachable Pusher-Vasoocclusive Coil Assembly with Interlocking Ball and Keyway Coupling”). These show methods and devices for delivery of coils or wires within the human body to sites such as aneurysms, to occlude those sites. Coils such as are discussed in those two documents (as well as in U.S. Pat. No. 4,994,069), may be of a regular or helical configuration or may assume a random convoluted configuration at the site. The coils normally are made of a radiopaque, biocompatible metal such as platinum, gold, tungsten, or alloys of these and other metals. In treating aneurysms it is common to place a number of coils within the aneurysm. The coils occlude the site by posing a physical barrier to blood flow and by promoting thrombus formation at the site.
Coils have typically been placed at the desired site within the vasculature using a catheter and a pusher. The site is first accessed by the catheter. In treating peripheral or neural conditions requiring occlusion, the sites are accessed with flexible, small diameter catheters such as those shown in U.S. Pat. Nos. 4,739,768 and 4,813,934 may be used. The catheter may be guided to the site through the use of guidewires (see U.S. Pat. No. 4,884,579) or by the use flow-directed means such as balloons placed at the distal end of the catheter. Use of guidewires involves the placement of relatively long, torqueable proximal wire sections within the catheter attached to more flexible distal end wire sections designed to be advanced across sharp bends at vessel junctions. The guidewire is visible using x-ray and allows a catheter to be placed in vessels taking extremely tortuous paths, even when those vessel are surrounded by soft tissue such as the brain.
Once the chosen site has been reached, the catheter lumen is cleared by removing the guidewire (if a guidewire has been used), and the coil is placed into the proximal open end of the catheter and advanced through the catheter with a pusher. Pushers are wires having a distal end that is adapted to engage and push the coil through the catheter lumen as the pusher is advanced through the catheter. When the coil reaches the distal end of the catheter, it is discharged from the catheter by the pusher into the vascular site. This technique of discharging the coil from the distal end of the catheter has a number of undesirable limitations. First, because of the plunging action of the pusher and the coil, the positioning of the coil at the site cannot be controlled to a fine degree of accuracy. Second, once the coil has left the catheter, it is difficult to reposition or retrieve the coil if such is desired.
Several techniques have been developed to enable more accurate placement of coils within a vessel. In one technique (U.S. Pat. No. 5,122,136, issued Jun. 16, 1992) the coil is bonded via a metal-to-metal joint to the distal end of the pusher. The pusher and coil are made of dissimilar metals. The coil-carrying pusher is advanced through the catheter to the site and a low electrical current is passed through the pusher-coil assembly. The current causes the joint between the pusher and the coil to be severed via electrolysis. The pusher may then be retracted leaving the detached coil at an exact position within the vessel. In addition to enabling more accurate coil placement, the electric current may facilitate thrombus formation at the coil site. The only perceived disadvantage of this method is that the electrolytic release of the coil requires a period of time so that rapid detachment of the coil from the pusher does not occur.
Another technique for detaching an embolic coil is shown in U.S. patent application Ser. No. 07/806,912. In that document, a coil having an enlarged portion is mated with a pusher having a keyway adapted to receive the enlarged portion of the coil in an interlocking relationship. The junction between the pusher and the coil is covered by a coaxial member. The coaxial member is movable by sliding the member axially. As the coaxial member is moved away from the junction where the coil's member engages the keyway of the pusher, the coil disengages and the pusher may be removed.
Another device for placement of coils is shown in U.S. patent application Ser. No. 07/806,898. This device includes a coil having a helical portion at one end and a pusher which is threaded to the inside of the helical coil by the use of a threaded section on the outside of the pusher. The device operates to discharge the coil by engaging the proximal end of the coil with a sleeve while the pusher is unthreaded. Once the pusher is free, the sleeve may be used to push the coil out into the treatment area.
Another method of placing an embolic coil is shown in U.S. Pat. No. 5,108,407. This patent shows the use of a device in which embolic coils are separated from the distal end of a catheter by the use of heat-releasable adhesive bonds. The coil adheres to the therapeutic device via a mounting connection. Laser energy is transferred through a fiber optic cable which terminates at the connector. The connector becomes warm and releases the adhesive bond between the connector and the coil.
U.S. Pat. No. 3,334,629, to Cohn, suggests the use of a pusher having a socket to push an occlusive device within the inferior vena cava. However, the device's rounded end is not used to retain the occlusive device within the end of the inserter.
None of these disclosed devices suggest the use of a distendible aperture to precisely place embolic coils having the enlarged member on their ends within the vasculature by axially pressing the member through the aperture.
SUMMARY OF THE INVENTION
This invention is a device for placing detachable coils at a site within the vasculature of the human body so to occlude that site using the coils. The device includes a coil that carries an enlarged member (such as a ball or other rounded shape) at its proximal end; a pusher housing which has a distendible receiver, e.g., a socket, at its distal end having a throat or aperture which is smaller in diameter than the diameter of the member on the coil but which will distend to allow the ball to pass therethrough. The device also includes a plunger which is situated within the pusher housing and will press the coil's receiver through the distendible throat and thereby uncouple the coil from the pusher. This invention also includes the apparatus used to refit the distal end of the pusher with additional coils.
Another portion of the invention is a method for occluding a selected site within a vessel comprising the steps of: (a) accessing the site with a distal end of a catheter; (b) advancing the assembly described above through the catheter with the assembly situated at the proximal end of the pusher housing's throat to a position out the end of the distal end of the catheter; (c) activating the plunger to push the member axially through the distendible throat and thereby detach the coil from the pusher; and (d) withdrawing the catheter and pusher from the vessel. An alternative to step (d) may include the step of removing the pusher and reloading it with a coil while le
Palermo Thomas J.
Pham Pete Phong
Dawson Glenn K.
Morrison & Foerster / LLP
Sci-Med Life Systems, Inc.
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