Radially-expandable stent and delivery system

Abstract

The present invention provides radially-expandable stents that, in various embodiments, may reduce the bending stresses/strains associated with the compressed state of self-expanding stents and/or may prevent longitudinal expansion/contraction of radially expandable stents between the compressed and expanded states. In addition, stents according to the present invention preferably exhibit increased longitudinal flexibility in both the compressed and expanded states. The present invention also includes delivery systems in which threading of the guidewire through the delivery system may be simplified. In addition, the delivery systems according to the present invention may also incorporate a balloon to assist in radially expanding the stent and/or seating of the stent in the lumen during deployment without removing the stent delivery catheter. Further, the delivery systems may also include a support tube at the proximal end to assist in fixing the position of the stent relative to a guide catheter during deployment of the stent.

What is claimed is:  
     
         1 . A radially expandable stent for implantation within a body lumen comprising: 
 an elongated generally tubular body defining a passageway having a longitudinal axis;    the body comprising a plurality of circumferential support sections arranged successively along the longitudinal axis, each of the support sections having a length along the longitudinal axis;    each of the circumferential support sections comprising a plurality of primary bends interconnected by struts, the primary bends being located on alternating ends of the support section around the circumference of the body, each of the struts connecting successive primary bends on opposite ends of the support section and having a midpoint generally located therebetween; and    at least one longitudinal member connecting adjacent support sections in the body, the longitudinal member having a first end attached proximate the midpoint of one of the struts and a second end attached proximate the midpoint of one of the struts in the adjacent support section;    wherein the stent is radially compressible into a compressed state in which the struts are generally aligned with the longitudinal axis and radially expandable into an expanded state in which the struts and the primary bends in each of the support sections are arranged in a zigzag pattern, and further wherein the longitudinal length of the stent in the compressed state is substantially the same as the longitudinal length of the stent in the expanded state.    
     
     
         2 . A stent according to  claim 1 , wherein the body comprises first, second and third support sections, and further wherein each of the longitudinal members connecting the first support section to the second support section are circumferentially offset from each of the longitudinal members connecting the second support section to the third support section.  
     
     
         3 . A stent according to  claim 1 , further comprising two or more longitudinal members connecting adjacent support sections in the body.  
     
     
         4 . A stent according to  claim 1 , wherein all of the support sections are in phase with each other.  
     
     
         5 . A stent according to  claim 1 , wherein at least one pair of adjacent support sections are out of phase with each other.  
     
     
         6 . A stent according to  claim 1 , wherein the body comprises a nickel titanium alloy.  
     
     
         7 . A stent according to  claim 1 , wherein each primary bend of the plurality of primary bends connects a pair of struts in the support section, and further wherein each pair of struts abut at a point between the primary bend and the midpoint of each of the struts in the pair of struts when the stent is in the compressed state, whereby the bending stress is reduced at each primary bend of the plurality of primary bends.  
     
     
         8 . A stent according to  claim 7 , wherein at least one of the struts in each pair of struts associated with one of the primary bends comprises a secondary bend located between the midpoint and one end of the strut, the secondary bend including an apex facing the other strut in the pair of struts, and further wherein the point at which the pair of struts abut is at the apex of the secondary bend when the stent is in the compressed state.  
     
     
         9 . A stent according to  claim 7 , wherein each strut of the plurality of struts comprises two secondary bends, one of the secondary bends located on each side of the midpoint of the strut and each of the secondary bends being spaced from the ends of the strut, each of the secondary bends having an apex, wherein the apexes of each of the secondary bends face the opposing struts in each pair of struts associated with one of the primary bends in the support section, and further wherein the point at which each pair of struts associated with one of the primary bends abut when the stent is in the compressed state is at the apexes of the secondary bends of the struts.  
     
     
         10 . A stent according to  claim 7 , wherein at least one of the struts in each pair of struts associated with one of the primary bends comprises a protrusion located between the midpoint and one end of the strut, the protrusion facing the other strut in the pair of struts, and further wherein the point at which the pair of struts abut is at the protrusion when the stent is in the compressed state.  
     
     
         11 . A stent according to  claim 7 , wherein each strut of the plurality of struts comprises two protrusions, one of the protrusions located on each side of the midpoint of the strut and each of the protrusions being spaced from the ends of the strut, wherein the protrusions face the opposing struts in each pair of struts associated with one of the primary bends in the support section, and further wherein the point at which each pair of struts abut when the stent is in the compressed state is at the protrusions in each strut in the pair of adjacent struts.  
     
     
         12 . A self-expanding radially expandable stent for implantation within a body lumen comprising: 
 an elongated generally tubular body defining a passageway having a longitudinal axis, the body comprising at least one circumferential support section having a length along the longitudinal axis;    each of the circumferential support sections comprising a plurality of primary bends interconnected by struts, the primary bends being located on alternating ends of the support section around the circumference of the body, each of the struts connecting successive primary bends on opposite ends of the support section and having a midpoint generally located therebetween;    wherein the stent is radially compressible into a compressed state and radially expandable into an expanded state in which the struts and primary bends in each of the support sections are arranged in a zigzag pattern, and further wherein each pair of adjacent struts associated with each of the primary bends abut at a point between the primary bend and the midpoint of each strut in the pair of adjacent struts when the stent is in the compressed state, whereby the bending stress is reduced at each primary bend of the plurality of primary bends.    
     
     
         13 . A stent according to  claim 12 , wherein at least one of the struts in the pair of struts associated with each of the primary bends comprises a secondary bend located between the midpoint and one end of the strut, the secondary bend including an apex facing the other strut in the pair of struts, and further wherein the point at which the pair of struts abut is at the apex of the secondary bend when the stent is in the compressed state.  
     
     
         14 . A stent according to  claim 12 , wherein each strut of the plurality of struts comprises two secondary bends, one of the secondary bends located on each side of the midpoint of the strut and each of the secondary bends being spaced from the ends of the strut, each of the secondary bends having an apex, wherein the apexes of each of the secondary bends face the opposing struts in each pair of struts associated with one of the primary bends in the support section, and further wherein the point at which each pair of struts associated with one of the primary bends abut when the stent is in the compressed state is at the apexes of the secondary bends of the struts.  
     
     
         15 . A stent according to  claim 12 , wherein at least one of the struts in each pair of struts associated with one of the primary bends comprises a protrusion located between the midpoint and one end of the strut, the protrusion facing the other strut in the pair of struts, and further wherein the point at which the pair of struts abut is at the protrusion when the stent is in the compressed state.  
     
     
         16 . A stent according to  claim 12 , wherein each strut of the plurality of struts comprises two protrusions, one of the protrusions located on each side of the midpoint of the strut and each of the protrusions being spaced from the ends of the strut, wherein the protrusions face the opposing struts in each pair of struts associated with one of the primary bends in the support section, and further wherein the point at which each pair of struts associated with one of the primary bends abut when the stent is in the compressed state is at the protrusions in the struts.  
     
     
         17 . A self-expanding radially expandable stent for implantation within a body lumen comprising: 
 an elongated generally tubular body defining a passageway having a longitudinal axis, the body comprising at least one circumferential support section having a length along the longitudinal axis;    each of the circumferential support sections comprising a substantially continuous element including a plurality of primary bends interconnected by struts, the primary bends being located on alternating ends of the support section around the circumference of the body, each of the struts connecting successive primary bends on opposite ends of the support section and having a midpoint generally located therebetween, wherein the stent is radially compressible into a compressed state and radially expandable into an expanded state in which the struts and primary bends in each of the support sections are arranged in a zigzag pattern; and    means for reducing bending stress at the primary bends when the stent is in the compressed state.    
     
     
         18 . A stent according to  claim 17 , wherein the means for reducing bending stress causes each pair of struts associated with one of the primary bends to abut at a point between the midpoints of the pair of struts and the primary bend.  
     
     
         19 . A stent according to  claim 17 , wherein the body comprises a plurality of circumferential support sections arranged successively along the longitudinal axis, and further wherein the body comprises at least one longitudinal member connecting adjacent support sections in the body, the longitudinal member having a first end attached to one of the support sections and a second end attached to the adjacent support section.  
     
     
         20 . A stent according to  claim 19 , wherein the first end of each of the longitudinal members is attached proximate the midpoint of one of the struts in one of the support sections and the second end of each of the longitudinal members is attached proximate the midpoint of one of the struts in an adjacent support section; wherein the longitudinal length of the stent in the compressed state is substantially the same as the longitudinal length of the stent in the expanded state.  
     
     
         21 . A delivery system for implantation of a radially-expandable stent within a body lumen comprising: 
 an inner tube having a proximal end and a distal end, the inner tube having an inner tube lumen formed therein, the inner tube lumen having an opening at the distal end of the inner tube;    a cover sheath having a proximal end and a distal end, the cover sheath comprising a wall defining a cover sheath lumen, the inner tube located within the cover sheath lumen;    a stent positioned about the inner tube at the distal end of the cover sheath;    a first guidewire opening in the inner tube lumen, the first guidewire opening spaced from the distal end of the inner tube;    a second guidewire opening in the wall of the cover sheath, the second guidewire opening located proximate the first guidewire opening; and    a guide element having a distal end located within the inner tube lumen, the guide element extending between the first and second guidewire openings.    
     
     
         22 . A system according to  claim 21 , wherein the guide element comprises a proximal end located outside of the cover sheath lumen such that the guide element extends through the second guidewire opening.  
     
     
         23 . A system according to  claim 21 , wherein the guide element is removably positioned in the inner tube lumen and the first and second guidewire openings.  
     
     
         24 . A system according to  claim 21 , wherein the inner tube lumen terminates at the first guidewire opening.  
     
     
         25 . A system according to  claim 21 , wherein the first guidewire opening is formed in an inner tube wall.  
     
     
         26 . A system according to  claim 21 , wherein the guide element comprises a guide lumen formed in the distal end of the guide element.  
     
     
         27 . A system according to  claim 26 , wherein the guide lumen can receive only a portion of the guidewire.  
     
     
         28 . A system according to  claim 21 , wherein the stent is self-expanding and comprises: 
 an elongated generally tubular body defining a passageway having a longitudinal axis, the body comprising at least one circumferential support section having a length along the longitudinal axis;    each of the circumferential support sections comprising a plurality of primary bends interconnected by struts, the primary bends being located on alternating ends of the support section around the circumference of the body, each of the struts connecting successive primary bends on opposite ends of the support section and having a midpoint generally located therebetween;    wherein the stent is radially compressible into a compressed state and radially expandable into an expanded state in which the struts and primary bends in each of the support sections are arranged in a zigzag pattern, and further wherein each pair of adjacent struts associated with each of the primary bends abut at a point between the primary bend and the midpoint of each strut in the pair of adjacent struts when the stent is in the compressed state, whereby the bending stress is reduced at each primary bend of the plurality of primary bends.    
     
     
         29 . A system according to  claim 28 , wherein the stent is biased against the interior surface of the cover sheath in the compressed state, and further wherein the inner tube comprises a shoulder having an outside diameter greater than an inside diameter of the stent in the compressed state within the cover sheath, whereby movement of the cover sheath proximally forces the stent out of the cover sheath.  
     
     
         30 . A system according to  claim 28 , wherein at least one of the struts in the pair of struts associated with each of the primary bends comprises a secondary bend located between the midpoint and one end of the strut, the secondary bend including an apex facing the other strut in the pair of struts, and further wherein the point at which the pair of struts abut is at the apex of the secondary bend when the stent is in the compressed state.  
     
     
         31 . A stent according to  claim 28 , wherein at least one of the struts in each pair of struts associated with one of the primary bends comprises a protrusion located between the midpoint and one end of the strut, the protrusion facing the other strut in the pair of struts, and further wherein the point at which the pair of struts abut is at the protrusion when the stent is in the compressed state.  
     
     
         32 . A stent according to  claim 28 , wherein the body comprises a plurality of circumferential support sections arranged successively along the longitudinal axis, and further wherein the body comprises at least one longitudinal member connecting adjacent support sections in the body, the longitudinal member having a first end attached proximate the midpoint of one of the struts in one of the support sections and a second end attached proximate the midpoint of one of the struts in an adjacent support section; wherein the longitudinal length of the stent in the compressed state is substantially the same as the longitudinal length of the stent in the expanded state.  
     
     
         33 . A system according to  claim 32 , wherein the body of the stent comprises first, second and third support sections, and further wherein each of the longitudinal members connecting the first support section to the second support section are circumferentially offset from each of the longitudinal members connecting the second support section to the third support section.  
     
     
         34 . A system according to  claim 21 , further comprising: 
 an expandable balloon located on the inner tube; and    an inflation lumen in fluid communication with the balloon, the inflation lumen extending from the proximal end of the delivery system to the balloon.    
     
     
         35 . A system according to  claim 34 , wherein the balloon is located between the stent and the inner tube.  
     
     
         36 . A method of deploying a stent within a body lumen comprising: 
 a) providing a radially expandable stent on a delivery system comprising: 
 an inner tube having a proximal end and a distal end, the inner tube having an inner tube lumen formed therein, the inner tube lumen having an opening at the distal end of the inner tube and a first guidewire opening in the inner tube lumen, the first guidewire opening spaced from the distal end of the inner tube;  
 a stent positioned on the exterior surface of the inner tube at the distal end of the inner tube;  
 a cover sheath having a proximal end and a distal end, the cover sheath comprising a wall defining a cover sheath lumen, the inner tube and stent located within the cover sheath lumen, the cover sheath further including a second guidewire opening in the wall of the cover sheath, the second guidewire opening located proximate the first guidewire opening in the inner tube; and  
 a guide element having a distal end located within the inner tube lumen, the guide element extending between the first and second guidewire openings, wherein the guide element comprises a guide lumen formed in the distal end of the guide element;  
   b) positioning a guidewire within a body lumen, wherein a proximal end of the guidewire extends out of the body lumen;    c) inserting the proximal end of the guidewire into the inner tube lumen at the distal end of the inner tube;    d) advancing the proximal end of the guidewire through the inner tube lumen towards the first guidewire opening and the distal end of the guide element, wherein at least a portion of the proximal end of the guidewire is advanced into the guide lumen in the distal end of the guide element;    e) advancing the proximal end of the guidewire through the first and second guidewire openings;    f) advancing the distal end of the inner tube and the stent over the guidewire towards the distal end of the guidewire, wherein the stent is positioned at a desired location within the body lumen; and    g) deploying the stent at the desired location within the body lumen.    
     
     
         37 . A method according to  claim 36 , wherein the guide element is removably positioned in the inner tube lumen and the first and second guidewire openings, and further wherein the step of advancing the proximal end of the guidewire through the first and second guidewire openings further comprises moving the guide element out of the first and second guidewire openings.  
     
     
         38 . A method according to  claim 36 , wherein the guide lumen can receive only a portion of the proximal end of the guidewire.  
     
     
         39 . A method according to  claim 36 , wherein the guide element comprises a proximal end located outside of the cover sheath lumen such that the guide element extends through the second guidewire opening.  
     
     
         40 . A method of deploying a stent within a body lumen comprising: 
 a) providing a radially expandable stent on a delivery system comprising: 
 an inner tube having a proximal end and a distal end, the inner tube having an inner tube lumen formed therein;  
 a stent positioned on the exterior surface of the inner tube at the distal end of the inner tube;  
 an expandable balloon located on the inner tube;  
 an inflation lumen in fluid communication with the balloon, the inflation lumen extending from the proximal end of the delivery system to the balloon; and  
 a cover sheath having a proximal end and a distal end, the cover sheath comprising a wall defining a cover sheath lumen, the inner tube, stent, and balloon located within the cover sheath lumen;  
   b) positioning the inner tube, stent, balloon and cover sheath within a body lumen;    c) moving the cover sheath proximally relative to the distal end of the inner tube to deploy the stent with the body lumen; and    d) inflating the balloon within the stent.    
     
     
         41 . A method according to  claim 40 , wherein the balloon is located between the stent and the inner tube.  
     
     
         42 . A method of deploying a stent within a body lumen comprising: 
 a) providing a radially expandable stent on a delivery system comprising: 
 an inner tube having a proximal end and a distal end;  
 a stent positioned on the exterior surface of the inner tube at the distal end of the inner tube;  
 a cover sheath having a proximal end and a distal end, the cover sheath including a cover sheath lumen, the inner tube and stent located within the cover sheath lumen; and  
 a support tube having a proximal end and a distal end, the support tube including a support tube lumen containing at least a portion of the proximal end of the cover sheath, the cover sheath being movable in the proximal and distal directions within the support tube lumen and the position of the inner tube being fixed relative to the position of the support tube;  
   b) positioning a guide catheter within a body lumen;    c) advancing the distal ends of the inner tube and the cover sheath through the guide catheter;    d) fixing the position of the support tube relative to the guide catheter, wherein the positions of the distal end of the inner tube and the stent within the body lumen are also fixed relative to the guide catheter; and    e) moving the cover sheath proximally to release the stent on the distal end of the inner tube, thereby deploying the stent within the body lumen.    
     
     
         43 . A method according to  claim 42 , wherein the guide catheter includes a hemostasis valve and further wherein the step of fixing the position of the support tube relative to the guide catheter comprises closing the hemostasis valve on the support tube.  
     
     
         44 . A method according to  claim 42 , wherein the support tube and the inner tube are fixedly attached to a handle and the cover sheath is attached to an actuator, the actuator movable relative to the handle, and further wherein the step of moving the cover sheath comprises moving the actuator relative to the handle.