Ultraflexible open cell stent

Abstract

Disclosed is an open cell stent that has adjacent sets of circumferential struts connected by means of highly flexible, undulating, connecting struts. To decrease outward flaring of the circumferential struts when the pre-deployed stent is advanced through highly curved vessels, each unconnected strut of the sets of circumferential struts has a decreased longitudinal length as compared to the longitudinal length of the circumferential struts that are connected by the flexible connecting struts. To decrease the propensity for outward flaring of the end set of circumferential struts, the longitudinal length of the end set of circumferential struts is shorter than the longitudinal length of the interior set of circumferential struts. Also, the attachment point of the flexible connecting struts is off the center of the curved sections of the circumferential struts, thus also decreasing the tendency for outward flaring of the end set of circumferential struts.

What is claimed is:  
     
         1 . A stent in the form of a thin-walled, lace-like, cylindrical tube with a longitudinal axis, the stent comprising: 
 a multiplicity of interior circumferential sets of strut members and one end circumferential set of strut members at each of the two longitudinal ends of the stent;    each interior circumferential set of strut members including at least one connected strut member consisting of a long diagonal section having a longitudinal length L1 fixedly attached along a connecting line to a connected curved section, each connected curved section being joined by means of a longitudinal connecting link to one curved section of an adjacent circumferential set of strut members;    each interior set of strut members also including at least one unconnected strut member consisting of a short diagonal section having a longitudinal length L2 fixedly joined to an unconnected curved section; and    the stent being further characterized by having the length L1 of the long diagonal section being longer than the length L2 of the short diagonal section, i.e.; L1>L2, so that the unconnected strut members have a decreased tendency for flaring outward as the stent is advanced though a curved vessel.    
     
     
         2 . The stent of  claim 1  wherein the longitudinal connecting link is straight.  
     
     
         3 . The stent of  claim 1  wherein the longitudinal connecting link is an undulating, flexible, longitudinal connecting link that is adapted to change its length in the longitudinal direction as the stent is advanced through a curved vessel.  
     
     
         4 . The stent of  claim 3  wherein the place where each flexible longitudinal connecting link is joined to the interior set of strut members is near the connecting line where a connected curved section is joined to a diagonal section.  
     
     
         5 . The stent of  claim 3  wherein the flexible connecting link is in the general form of an “S”.  
     
     
         6 . The stent of  claim 1  wherein there are at most three longitudinal connecting links that join each adjacent pair of circumferential sets of strut members.  
     
     
         7 . The stent of  claim 1  wherein there are at most five longitudinal connecting links that join each adjacent pair of. circumferential sets of strut members.  
     
     
         8 . The stent of  claim 1  wherein there are at most eight longitudinal connecting links that join each adjacent pair of circumferential sets of strut members.  
     
     
         9 . The stent of  claim 3  wherein upon deployment to its deployed state, the flexible longitudinal connecting links extend in their longitudinal length thereby reducing the foreshortening of the stent.  
     
     
         10 . The stent of  claim 1  wherein the total length L4 in the longitudinal direction of each end circumferential set of strut members is shorter than the length L3 of each interior circumferential set of strut members, thus decreasing the propensity for flaring outward of the end circumferential set of strut members when the pre-deployed stent is advanced through a curved vessel.  
     
     
         11 . The stent of  claim 1  wherein the metal from which the stent is formed is stainless steel and the wall thickness of the pre-deployed stent is greater than 0.0045 inches so as to obtain acceptable radiopacity for the stent when it is being implanted into a human subject.  
     
     
         12 . The stent of  claim 1  wherein the metal from which the stent is formed is tantalum and the wall thickness of the pre-deployed stent is greater than 0.002 inches so as to obtain acceptable radiopacity for the stent when it is being implanted into a human subject.  
     
     
         13 . The stent of  claim 1  wherein the metals from which the stent is formed is a sandwich of three coaxial tubes having stainless steel as interior and exterior tubes and a central tube formed from a high density metal, the total wall thickness of the pre-deployed stent being greater than 0.003 inches so as to obtain acceptable radiopacity for the stent when it is being implanted into a human subject.