Multi-layer coaxial vaso-occlusive device

Abstract

A vaso-occlusive device includes inner, intermediate, and outer elements arranged coaxially. The inner element is a filamentous element, preferably a microcoil. The intermediate element is made of a non-metallic material, preferably an expansile polymer. The outer element is substantially non-expansile and defines at least one gap or opening through which the intermediate element is exposed. In a preferred embodiment, when the intermediate element is expanded, it protrudes through the at least one gap or opening in the outer element and assumes a configuration with an undulating, convexly-curved outer surface defining a chain of arcuate segments, each having a diameter significantly greater than the diameter of the outer element. The expanded configuration of the intermediate element minimizes friction when the device is deployed through a microcatheter, thereby reducing the likelihood of buckling while maintaining excellent flexibility. The result is a device with enhanced pushability and trackability when deployed through a microcatheter.

1 . A vaso-occlusive device, comprising: 
 an elongate, flexible, filamentous inner element;    a non-metallic intermediate element coaxially surrounding the inner element and in intimate contact therewith; and    an outer element coaxially surrounding the intermediate element, the outer element defining an open area through which the intermediate element is exposed;    wherein along a substantial predetermined portion of the length of the device, the open area constitutes at least about 20 percent of the surface area of device within the predetermined portion of its length.    
   
   
       2 . The vaso-occlusive device of  claim 1 , wherein the intermediate element includes an expansile polymeric material  
   
   
       3 . The vaso-occlusive device of  claim 1 , wherein the outer element includes a helical coil having a pitch that defines the open area through which the intermediate element is exposed.  
   
   
       4 . The vaso-occlusive device of  claim 3 , wherein the coil is formed of a helically-wound filament, and wherein the pitch of the coil is greater than the diameter of the filament.  
   
   
       5 . The vaso-occlusive device of  claim 4 , wherein the pitch of the coil is between about 5 percent and about 100 percent greater than the diameter of the filament.  
   
   
       6 . The vaso-occlusive device of  claim 2 , wherein the expansile polymeric material comprises a hydrogel.  
   
   
       7 . The vaso-occlusive device of  claim 6 , wherein the expansile polymeric material consists essentially of a hydrogel.  
   
   
       8 . The vaso-occlusive device of  claim 7 , wherein the hydrogel is of a type that expands in response to a change in an environmental parameter.  
   
   
       9 . The vaso-occlusive device of  claim 8 , wherein the environmental parameter is selected from the group consisting of temperature and pH.  
   
   
       10 . The vaso-occlusive device of  claim 1 , wherein the inner element comprises at least two concentric microcoils.  
   
   
       11 . The vaso-occlusive device of  claim 1 , wherein the inner element defines a lumen containing a hollow, tubular core element.  
   
   
       12 . The vaso-occlusive device of  claim 1 , wherein the inner element defines a lumen containing a substantially solid core element.  
   
   
       13 . The vaso-occlusive device of  claim 1 , wherein at least one of the inner element and the intermediate element includes a material selected from the group consisting of at least one of a drug, a bioactive agent, a therapeutic compound, cellular material, genes, collagen, and protein.  
   
   
       14 . A vaso-occlusive device comprising: 
 a filamentous inner element;    a non-metallic intermediate element coaxially surrounding the inner element and in intimate contact therewith; and    an outer element coaxially surrounding the intermediate element and having an open area through which the intermediate element is exposed, the outer element comprising a helically-wound filament defining a helical coil having a pitch that is greater than the diameter of the filament.    
   
   
       15 . The vaso-occlusive device of  claim 14 , wherein at least one of the inner and intermediate elements is made at least in part of a non-metallic biocompatible material.  
   
   
       16 . The vaso-occlusive device of  claim 15 , wherein the pitch of the coil is between about 5 percent and about 100 percent greater than the diameter of the filament.  
   
   
       17 . The vaso-occlusive device of  claim 14 , wherein the inner element comprises a microcoil made of a biocompatible material selected from the group consisting of metal wire and polymeric filament, and wherein the intermediate element is formed of a biocompatible polymeric material  
   
   
       18 . The vaso-occlusive device of  claim 14 , wherein the intermediate element includes an expansile polymeric material  
   
   
       19 . The vaso-occlusive device of  claim 14 , wherein along a substantial predetermined portion of the length of the device, the open area constitutes at least about 20 percent of the surface area of device within the predetermined portion of its length.  
   
   
       20 . The vaso-occlusive device of  claim 18 , wherein the expansile polymeric material comprises a hydrogel.  
   
   
       21 . The vaso-occlusive device of  claim 20 , wherein the expansile polymeric material consists essentially of a hydrogel.  
   
   
       22 . The vaso-occlusive device of  claim 21 , wherein the hydrogel is of a type that expands in response to a change in an environmental parameter.  
   
   
       23 . The vaso-occlusive device of  claim 22 , wherein the environmental parameter is selected from the group consisting of temperature and pH.  
   
   
       24 . The vaso-occlusive device of  claim 14 , wherein the inner element has proximal and distal ends, and wherein the outer element comprises an open-wound helical coil portion extending between proximal and distal end sections that are respectively attached to the inner element adjacent to the proximal and distal ends of the inner element, wherein the open-wound portion defines the open area.  
   
   
       25 . The vaso-occlusive device of  claim 14 , wherein at least one of the inner element and the intermediate element includes a material selected from the group consisting of at least one of a drug, a bioactive agent, a therapeutic compound, cellular material, genes, collagen, and protein.