Stents and catheters having improved stent deployment

Abstract

An implant delivery system and method comprises an implant, for example, a stent, and a delivery catheter. The stent has a scaffold with a coating or a shell that retains the scaffold in a collapsed configuration. The coating or shell is made of a material that dissolves or biodegrades upon exposure to a dissolution or biodegradation media. The stent is used with an implant delivery system which has a catheter with a catheter, wherein the stent is mounted on the catheter shaft. The catheter shaft is configured to be withdrawn through the patient's vessel when the scaffold is in its expanded configuration. Advantageously, the implant is thereby prevented from changing length during implant delivery and implant deployment.

1 . A stent for insertion into a body lumen, comprising:
 a scaffold having a collapsed and a diametrically expanded configuration; and   a coating or a shell surrounding the scaffold that retains the scaffold in its collapsed configuration, said coating or shell made of a material that dissolves or biodegrades upon exposure to a dissolution or biodegradation media;   wherein the scaffold is expanded from its collapsed to its expanded configuration through exposure of the coating or shell to the dissolution or biodegradation media.   
   
   
       2 . The stent of  claim 1 , wherein the coating comprises a material selected from the group consisting of sugar, carbowax, polyethylene oxide, and poly vinyl alcohol. 
   
   
       3 . The stent of  claim 1 , wherein the coating or shell comprises a bioactive material selected from the group consisting of antirestenotic agents, anti-inflammatory agents, antithrombotic agents, antiatheromatic (antiatheroma) agents, and antioxidative agents. 
   
   
       4 . The stent of  claim 1 , wherein the shell comprises a material selected from the group consisting of sugar, carbowax, polyethylene oxide, poly vinyl alcohol, poly lactic acid (PLA), poly glycolic acid (PGA), poly lactic glycolic acid (PLGA), poly (ε-caprolactone) copolymers, polydioxanone, poly(propylene fumarate) poly(trimethylene carbonate) copolymers, polyhydroxy alkanoates, polyphosphazenes, polyanhydrides, poly(ortho esters), poly(amino acids), or “pseudo”-poly(amino acids). 
   
   
       5 . The stent of  claim 1 , wherein the shell comprises tubing into which the scaffold is inserted, or a film which is wrapped around the compressed scaffold. 
   
   
       6 . The stent of  claim 5 , wherein the shell comprises a longitudinal slit or is perforated. 
   
   
       7 . The stent of  claim 1 , wherein the scaffold is self-expanding. 
   
   
       8 . The stent of  claim 1 , wherein the scaffold is balloon-expandable. 
   
   
       9 . An implant delivery system for deploying a stent in a patient's vessel, the system comprising:
 a catheter having a catheter shaft;   a stent mounted on the catheter shaft, said stent comprising a scaffold having a collapsed configuration and a diametrically expanded configuration; and   a coating or a shell surrounding the scaffold and retaining the scaffold in its collapsed configuration, said coating or shell made of a material that dissolves or biodegrades upon exposure to a dissolution or biodegradation media;   wherein the scaffold is expanded from its collapsed to its expanded configuration through exposure of the coating or shell to the dissolution or biodegradation media and wherein the catheter shaft is configured to be withdrawn through the patient's vessel when the scaffold is in its expanded configuration.   
   
   
       10 . The system of  claim 9 , wherein the stent is self-expanding. 
   
   
       11 . The system of  claim 9 , further comprising a slidable tubular sheath surrounding the stent in the collapsed configuration on the catheter shaft, said tubular sheath protecting the coating or a shell from exposure to the dissolution or biodegradation media. 
   
   
       12 . The system of  claim 9 , further comprising an inflatable balloon disposed between the stent and the catheter shaft, said balloon fracturing the coating or shell upon inflation. 
   
   
       13 . The system of  claim 12 , wherein the balloon is sealingly attached to both a proximal end and a distal end of the catheter shaft. 
   
   
       14 . The system of  claim 12 , further comprising a slidable tubular sheath surrounding the stent in the collapsed configuration on the catheter shaft, wherein the balloon is constructed such that a force of friction of the balloon in contact with the stent is greater than a force of friction of the sheath in contact with the stent. 
   
   
       15 . A method for delivering a stent to a treatment site, comprising the steps of:
 providing an implant delivery system having a stent mounted on a catheter shaft, said stent having a scaffold with a coating or a shell surrounding the scaffold and retaining the scaffold in its collapsed configuration, and a tubular sheath surrounding the stent in the collapsed configuration on the catheter shaft;   advancing the implant delivery system to the treatment site;   withdrawing the tubular sheath to expose the coating or shell to a dissolution or biodegradation media; and   withdrawing the catheter shaft from the treatment site.   
   
   
       16 . The method of  claim 15 , wherein the stent is self-expanding. 
   
   
       17 . The method of  claim 15 , wherein the delivery system further comprises a balloon interposed between the stent and the catheter shaft, the method further comprising the step of inflating the balloon to cause expansion of the stent before withdrawing the catheter shaft. 
   
   
       18 . The method of  claim 17 , wherein inflating the balloon comprises pressurizing a balloon inflation lumen with fluid or gas until a force of sliding friction of the stent against the balloon exceeds a force of sliding friction of the stent against the tubular sheath. 
   
   
       19 . A method for delivering a stent to a treatment site, comprising the steps of:
 providing an implant delivery system having a stent mounted on a catheter shaft, a balloon interposed between the stent and the catheter shaft, and a tubular sheath surrounding the stent in the collapsed configuration on the catheter shaft;   advancing the implant delivery system to the treatment site;   inflating the balloon to cause expansion of the stent before withdrawing the tubular sheath;   withdrawing the tubular sheath; and   withdrawing the catheter shaft from the treatment site.   
   
   
       20 . The method of  claim 19 , wherein the stent is self-expanding. 
   
   
       21 . The method of  claim 19 , wherein inflating the balloon comprises pressurizing a balloon inflation lumen with fluid or gas until a force of sliding friction of the stent against the balloon exceeds a force of sliding friction of the stent against the tubular sheath.