Abstract:
An improved apparatus for delivering and deployment of an expandable stent with a protection sheath within a blood vessel is provided. The system comprises a fluid pressure device which is coupled with a retraction device for the protection sheath such that after retraction of the protection sheath the stent is automatically deployed by the fluid pressure device. The advantage of the invention is an easy and simple operation of the apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 10/523,596, filed Dec. 2, 2005, now U.S. Pat. No. 7,875,067, which is a 371 of International Application No. PCT/EP03/08795 filed Aug. 7, 2003, which claims priority to European Application No. 02017696.2 filed Aug. 7, 2002, which prior applications are hereby incorporated by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a system for delivering a stent into a blood vessel for use e.g. by a physician in a well-known manner for supporting and/or reinforcing the vessel walls and maintaining the vessel in an open, unobstructed condition. It is well-known in the prior art that the stent can be covered and secured in a catheter by a sheath during tracking and delivery in the blood vessel. 
       BACKGROUND OF THE INVENTION 
       [0003]    Furthermore, it is known that the sheath is retracted before positioning the stent within the vessel. A stent delivery system according to U.S. Pat. No. 6,168,617 comprises a catheter with a balloon for inflating a stent which is covered during delivering by a sheath. The sheath is axially moveable on the shaft of the catheter and can be retracted in proximal direction by pull-back means. 
         [0004]    U.S. Pat. No. 5,113,608 discloses a stent delivery device which comprises a hydraulically actuated retractable sheath. A pressurising fluid is either supplied by an inflation volume to a portion of a piston housing or is withdrawn from a portion of a piston housing, thereby actuating a piston. As the piston moves the sheath is retracted. 
         [0005]    It is the object of the invention to provide an improved stent delivery system with a protection sheath on the stent wherein its handling is simplified. 
         [0006]    The object is achieved by the features of the claims. 
         [0007]    In order to achieve the object, the invention is based on the following basic ideas. 
       BRIEF SUMMARY 
       [0008]    A device for retracting the sheath is coupled with a fluid pressure device for the inflation and deflation of expandable means (balloon) for deploying the stent. A pressurised fluid, e.g. a liquid or a gas, is supplied from the fluid pressure device to the refraction device and causes the retraction of the sheath. After or during the refraction of the sheath, the pressurised fluid of the cylinder is directed to the expandable means for expansion and deployment of the stent. According to the invention, the expansion of the stent is controlled by the position of the piston within the cylinder. Thus, an automatic inflation of the expandable means after or during retraction of the sheath can be achieved. 
         [0009]    The invention has the following advantages. The protection sheath is withdrawn by activating the fluid pressure device, which also controls the expansion of the stent by means of the expansion means. Furthermore, stent-loss and pop-open by using bi-stable stent designs such as Biflex-stents do not occur. There is also no flaring of stainless steel stents and no significantly increased profiles (sheath thickness 0.01 to 0.02 mm). If a drug coated stent is used, no drug will be lost during handling. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the following, the invention will be explained in more detail with respect to the figures. 
           [0011]      FIG. 1   a  is a schematic illustration of a first inventive embodiment, 
           [0012]      FIG. 1   b  shows the partial proximal end of the cylinder  15  in  FIG. 1   a  after refraction of the sheath, 
           [0013]      FIG. 2  is a schematic illustration of a second inventive embodiment, 
           [0014]      FIGS. 3-10  show steps of the method of operation of the second inventive embodiment, 
           [0015]      FIG. 11  is a schematic illustration of a third inventive embodiment, and 
           [0016]      FIGS. 12-19  show steps of the method of operation of the third inventive embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    In the first inventive embodiment of  FIG. 1   a , a sheath  1  is arranged on a stent  2  supported by an expandable means  3 , preferably an inflatable balloon. The arrangement  1 ,  2  and  3  is supported by a catheter (not shown) and inserted into a blood vessel. Furthermore, a sheath retraction device  5  to  9 ,  11  and  13  to  15  and a fluid pressure device  11  to  14  are connected with the arrangement  1  to  3  by a wire  4  and a tube  10 , respectively. The wire  4  connects the sheath  1  with a first piston  5  in a cylinder  15  comprising a cylinder housing  9 . A hook  6  is connected at the proximal side of the piston  5 . The cylinder  15  further comprises a floating second piston  7  with an opening  18  which can be penetrated by the hook  6 . The floating piston  7  closes an outlet  17  in the cylinder  15 . The tube  10  connects the expandable means  3  with a tube  16  mounted at the outlet  17  of the cylinder  15 . A tube  14  is connected to a inflation/deflation device schematically shown as double-arrow  13  at the one end and via a unidirectional valve (check valve)  11  with the cylinder  15  at the other end. Furthermore, the tube  14  is connected via a unidirectional valve (check valve)  12  with the tube  10 . 
         [0018]    The first inventive embodiment operates as follows. In the arrangement of  FIG. 1   a  the expandable means  3  is in a deflated state and the sheath  1  covers the stent  2 . The floating second piston  7  is positioned so that the opening  17  of the cylinder housing  9  and, thus, the tube  16  are closed. An operator (physician) applies pressure from the inflation/deflation device  13  to the tube  14 . The pressure shuts the unidirectional valve  12  and opens the unidirectional valve  11 . Thus, the pressurised fluid flows into the cylinder  15  and shifts the first piston  5  with the wire  4  and the sheath  1  in proximal direction, i.e. the sheath  1  is retracted from the stent  2 . The pressure necessary for moving the piston  5  is very low. When the first piston  5  reaches the floating second piston  7 , the proximal end of the wire  4  with the hook  6  penetrates the opening  18  in the piston  7 , and the piston  5  moves the piston  7  to the proximal end of the cylinder  15 . Thereby, the hook  6  engages the hook holder  8  wherein the piston  5  with the wire  4  and the sheath  1  is fixed at the proximal end. This fixed position of the pistons  5  and  7  is shown in  FIG. 1   b . In this position, the sheath is completely removed (not shown) from the stent  2 , and the outlet  17  of the cylinder  15  is open towards the cylinder chamber. In this manner, the pressurized fluid from the inflation/deflation device  13  flows via the tube  14  and the left side of the cylinder  15  through the outlet  17 , the tube  16  and the tube  10  to the expandable means  3 , inflates it and deploys the stent  2 . The pressure is applied until a required stent diameter is reached. Then, the operator applies a vacuum from the inflation/deflation device  13  via the unidirectional valve  12  and the tube  10  to the expandable means  3 . During this suction, the unidirectional valve  11  is closed. At the end of the stent delivery and deployment process, the catheter with the expandable means and the sheath is removed from the blood vessel and the stent remains in the desired position within the blood vessel. 
         [0019]    In the second inventive embodiment of  FIG. 2  as in  FIG. 1   a , a protective cover sheath  101  is arranged on a stent  102  supported by an expandable means  103  being an inflatable balloon. As in  FIG. 1   a , the arrangement  101 ,  102  and  103  is supported by a catheter (not shown) and is inserted into a blood vessel. The arrangement  101 ,  102  and  103  is connected via a pull-wire  104  to a cylinder-piston arrangement  105 ,  106 ,  108 ,  110 ,  110   a,    112  and  114 . The cylinder-piston arrangement is connected to an inflation/deflation device schematically shown as an arrow  113 . A piston  105  with a connector ball  106  is arranged in the cylinder  115  at its distal end  115   a.  The wire  104  is fixed at the piston. At the proximal end  115   b  of the cylinder  115   a  receiving socket  108  is located, into which the connector ball engages when the piston arrives at the end, i.e. the right-hand side in  FIG. 2 , of the cylinder  115 . Furthermore, the cylinder-piston arrangement comprises a unidirectional valve  112 , fluid pressure lines  114 ,  110 ,  110   a  and an inlet/outlet  117  as connection to the inflation/deflation device  113 . 
         [0020]    With respect to  FIGS. 3-10 , the steps of operation of the second inventive embodiment are shown. In the second and subsequently in the third inventive embodiment, the fluid F is illustrated by black colour. 
         [0021]    Firstly, vacuum from the inflation/deflation device  113  is applied ( FIG. 3 ) in order to purge air from the catheter and the sheath retraction apparatus. In this state, the unidirectional valve  112  is opened and all parts of the apparatus are in connection with the vacuum. After removing the air from the apparatus, pressurized fluid F (e.g. liquid) is introduced from the inflation/deflation device  113  via the inlet/outlet  117 . The pressurized fluid F shuts the unidirectional valve  112  and enters the cylinder  115  at its distal end  115   a  behind the piston  105  (i.e. at the left-hand side of the piston in  FIG. 4 ). The pressurized fluid F moves the cylinder  105  in proximal direction wherein the wire  104  retracts the protective cover sheath  101  from the stent  102  (arrow A in  FIG. 5 ). During this procedure, the liquid is prevented from entering the catheter and the expandable means  103 . As shown in  FIG. 6 , after arrival of the piston  105  at the proximal end  115   b  of the cylinder  115 , the cover sheath  101  is completely removed from the stent  102 , the connector ball  106  is engaged in the receiving socket  108  and a opening  110   a,  which penetrates the cylinder wall to the fluid pressure line  110  is opened. The pressurized fluid F from the inflation/deflation device  113  via the line  114  and the cylinder  115  enters the line  110  and inflates the expandable means  103  ( FIG. 7 ). The expandable means (balloon)  103  expands and the stent  102  is deployed and contacts the wall of the blood vessel ( FIG. 8 ). Thereafter, the fluid is withdrawn and a vacuum is again applied by means of the inflation/deflation device  113  to deflate the balloon while the piston  105  and the cover sheath  101  remain fixed ( FIG. 9 ). In  FIG. 10 , the system is fully purged of fluid (e.g. liquid) and the balloon  103  can be re-inflated if necessary, or the expandable means and sheath may be removed from the blood vessel while the stent remains in the desired position within the blood vessel. 
         [0022]      FIG. 11  shows a third inventive embodiment, which differs from the first and second embodiment in the structure of the cylinder-piston arrangement. A two-position valve  207  is located in the cylinder  215 ; the valve  207  abuts via a spring  207   a  at the proximal end  215   b  (right hand side in  FIG. 11 ) of the cylinder  215 . In the position shown in  FIGS. 11 to 14 , the valve  207  shuts two channels  216   a,    216   b  which penetrate the wall of the cylinder  215 ; channel  216   a  connects a fluid pressure line  214  from the fluid pressure device  213  with a fluid pressure line  210  which applies the fluid pressure to the expandable means (balloon)  203 . When the piston  205  starting from the space  215   a  at the distal end of the cylinder  215  arrives at the two-position valve  207 , it pushes the valve (to the right in  FIG. 15 ) and opens the channels  216   a  and  216   b.  Thus, pressurized fluid F from the inflation/deflation device  213  enters the balloon  203  via the line  214 , the channels  216   a  and  216   b  and the line  210  ( FIGS. 15 to 17 ). 
         [0023]    The steps of the method of operation of the third inventive embodiment are shown with respect to  FIGS. 12-19 . 
         [0024]    Before operating, a vacuum is applied in order to purge air from the catheter and the sheath retraction apparatus by means of the inflation/deflation device  213 . Thereby, the unidirectional valve  212  is opened and the unidirectional valve  211  is closed so that space  215   a  at the distal end of the cylinder  215  at the left-hand side of the piston  205  remains open ( FIG. 12 ). In  FIG. 13 , pressurized fluid F from the inflation/deflation device  213  enters the space  215   a  of the cylinder  215  behind the piston  205  via the line  214  and the unidirectional valve  211 , while the unidirectional valve  212  and the channels  216   a  and  216   b  are closed. Thereafter, the piston  205  moves in proximal direction (to the right in  FIG. 14 ) and withdraws the protective cover sheath  201  from the stent  202  in the direction of arrows A ( FIG. 14 ). After the protective cover sheath  201  is fully retracted, the piston  205  pushes the valve  207  against the force of the spring  207   a  into an open position, and the connection between the line  214  and the line  210  via the channels  216   a  and  216   b  is opened ( FIG. 15 ). As shown in  FIG. 16 , pressurized fluid F flows via the line  214 , the channels  216   a  and  216   b  and the line  210  to the balloon  203 . While the unidirectional valve  211  remains open and pressurized fluid F acts against the piston  205  and pushes it to the right in  FIG. 17 , the two-position valve  207  remains in its open position. The balloon  203  expands in the direction of arrows B and the stent is deployed ( FIG. 17 ) and contacts the wall of the blood vessel (not shown). Thereafter, vacuum is again applied from the inflation/deflation device  213  and the balloon  203  deflates in the direction of arrows C ( FIG. 18 ). The unidirectional valve  211  is closed and the pressurized fluid behind the piston  205  acts on the piston  205  such that the piston  205  and the sheath  201  remain fixed ( FIG. 18 ). In the final state shown in  FIG. 19 , the catheter is fully purged and the balloon can be re-inflated if necessary. The pressurized fluid F holds the two-position valve  207  open and locks the sheath  201  in the retracted position. If the retraction apparatus will be used one time only, it can be removed. If the retraction apparatus will be re-used, the fluid F is purged from the cylinder  215  by opening the unidirectional valve  211  and pulling the piston  205  to the distal end  215   a.    
         [0025]    The fluid pressure for operating the refraction device and the expandable means can be controlled in such a manner that the retraction device and the expandable means work concurrently or sequentially, e.g. in order to control the correct position of the stent. 
         [0026]    It is an essential feature of the invention that the refraction of the sheath  1 ,  101  and  201 , respectively, namely at the end of the retraction step, automatically controls the deployment (expansion) of the stent  2 ,  102  and  202 , respectively. An operator can easily deploy a stent with a protection sheath simply by activating the inflation/deflation device.