Patent Application
20080046092
The stretch resistant embolic device 31 is disposed within the lumen 26 of the distal section 30 of the deployment catheter 14. The stretch resistant embolic device 31 includes a cylindrical embolic coil 32 having an atraumatic distal bead 36 bonded to the distal end of the coil 32. Also included is a stretch resistant fiber 40 which has a proximal end 48 bonded to the proximal end of the coil 32 and extends cylindrically around the outer surface of the embolic coil 32. The distal end 46 of the stretch resistant fiber 40 is attached to the distal end 38 of the coil 32. Additionally, a headpiece 44 is mounted on the proximal end 42 of the coil 32 which, in turn, is disposed in fluid tight engagement within the lumen 26 of the distal section 30 of the deployment catheter 14.
When the embolic coil 32 is at the desired treatment site, the handle 24 is manipulated to advance the threaded piston 22, which thereby infuses fluid into the lumen 26 of the deployment catheter 14. The fluid is advanced through the lumen 26 of the deployment catheter 14 and pressure is applied to the proximal end of the headpiece 44 to thereby displace it from its position within the distal section 30 of the deployment catheter 14.
If desired, the distal section 30 of the deployment catheter 14 may be formed from a material having a different durometer from that used to form the proximal section 18. For example, the proximal section 18 of the deployment catheter 14 may be formed of Pebax material having a durometer in the range of about 62 D to 75 D. The proximal section 18 will then be sufficiently flexible to traverse the vasculature of the human body, but also sufficiently rigid such that when a fluid pressure of approximately 300 psi is applied to the interior of this end of the deployment catheter there is little, if any, radial expansion of the walls of this section of the deployment catheter. In contrast, the distal section 30 of the deployment catheter 14 may be formed from a polymer material with a relatively low durometer. The distal section 30 of the deployment catheter 14 is preferably formed from a block copolymer, such as Pebax, having a durometer in a range of 25 D to 55 D with a preferred durometer of 40 D.
The lower durometer material used to form the distal section 30 of the deployment catheter 14 exhibits the characteristic that when a fluid pressure of approximately 300 psi is applied to the interior, the walls of the distal section 30 expand radially, somewhat similar to the action of a balloon inflating, to thereby release the headpiece 44 of the embolic coil 32.
More particularly, the cylindrical embolic coil 32 is preferably formed of helical turns 34 and is constituted from a platinum tungsten alloy. The atraumatic distal bead 36 has a generally hemispherical shape and is formed of a plasma bead or a solder weld. The stretch resistant fiber 40 preferably takes the form of a coil having helical turns and being constituted from a platinum tungsten alloy. In order to impart stretch resistance, the stretch resistant fiber 40 taking the form of a coil has fewer helical turns than the cylindrical embolic coil 32 and is therefore of a length that is shorter than that of the cylindrical embolic coil 32. Alternately, the fiber 40 may take the form of a nitinol wire or polymer braid or filament. Further, the stretch resistant fiber 40 in the form of a coil may have a diameter that differs from that of the cylindrical embolic coil. Additionally, the fiber 40 may be welded to the points of attachment at the proximal end 42 and distal end 38 of the cylindrical embolic coil 32 and at any additional points along the length of the cylindrical embolic coil 32. The headpiece 44 is formed from a metallic or polymeric material and preferably takes a generally hemispherical shape.
During placement of the cylindrical embolic coil 32 at the treatment site, fluid pressure is applied to the headpiece 44 to dislodge the headpiece and thereby the stretch resistant embolic device 31 from the deployment system 10. An important advantage of the present invention is that if it is determined that the embolic device 31 is improperly positioned the embolic device may then be withdrawn from that location and placed at another location, or even removed from the body altogether. The stretch resistant fiber 40 facilitates repositioning of the embolic device 31 because it prevents the cylindrical coil 32 from stretching when it is pulled proximally from the improper position. Once the embolic device 31 is released at the appropriate location, the stretch resistant fiber 40 has a limited mobility, which in part dictates a secondary shape for the embolic device 31 after it is released and no longer constrained by the deployment catheter.
Another important advantage of the present invention is that the stretch resistant fiber 40, taking the form of a coil, extends around the outer surface of the cylindrical embolic coil 32 and thus provides stretch resistance without compromising the flexibility of the device by adding bulk. The flexibility of the device is further maintained by having two different diameters and separate mobility for the cylindrical embolic coil 32 and the stretch resistant fiber 40. The two different diameters and separate mobility of the cylindrical embolic coil 32 and the stretch resistant fiber 40 also allows the stretch resistant fiber to better fit within the interstices between subsequently deployed devices.
As is apparent, there are numerous modifications of the preferred embodiment described above which will be readily apparent to one skilled in the art, such as many variations and modifications of the embolic coil including numerous coil winding configurations. There are also variations in the materials used to form the various components. Additionally, the diameters of the embolic coil and the stretch resistant fiber can be varied or can be the same, and the frequency of attachment between the embolic coil and the stretch resistant fiber can be varied to increase or decrease the stretch resistance. These modifications would be apparent to those having ordinary skill in the art to which this invention relates and are intended to be within the scope of the claims which follow.
