Patent Publication Number: US-2010125324-A1

Title: Catheter Inner Member

Description:
TECHNICAL FIELD 
     The technical field of this disclosure is medical devices, particularly, a catheter inner member for a rapid exchange catheter system for delivering a stent. 
     BACKGROUND 
     Catheters are used in a number of medical procedures to deliver medical devices to a target site within a body and other purposes. Catheters for delivering self expanding medical devices, such as stents, typically, have a tubular shaft defining an inner lumen with an inner wall of the catheter for a number of purposes, such as holding self expanding devices constrained or the like. Catheters for delivering self expanding stents also typically have a guidewire lumen fully or partially separate or apart from the inner lumen constraining the self expanding device to be delivered. Prior to insertion into the body, the catheter lumens should be flushed with a fluid, often saline, particularly in cases where the stent is to be implanted in the carotid artery which leads to the brain, where air bubbles may lead to brain injury, such as a stroke. Flushing a rapid exchange self expanding stent delivery catheter is currently a multi-step process where pressurized fluid sources are attached to the catheter handle or shaft through rudimentary or customized attachments to flush the catheter, and any devices attached to or contained in the catheter, such as stents. In an initial pre-flush configuration the guide wire lumen is plugged by a mandrel and fluid injected into the delivery system handle when it reaches the distal end of the catheter is prevented from flowing into the guidewire lumen by the mandrel and therefore flow around the guidewire lumen and bathes the stent with fluid. Once fluid is observed having crossed the stent and started leaking from the catheter sheath, the mandrel is removed and a finger is placed over the rapid exchange guidewire exit port, and further flushing is undertaken causing flushing fluid to flow into and through the guidewire lumen and out the end of the catheter Furthermore, a full flush of the catheter is difficult to achieve based on the small spaces and small diameter lumens into and through which the fluid must travel to achieve complete elimination of air from the catheter. Catheters are long, narrow structures, and ensuring that the fluid flows through and fills all appropriate structures can require an undesirably high level of force (pressure) to be applied (to an injection syringe, for example) or while maintaining a lower force (pressure) causes an undesirable delay for the fluid to reach and fill all catheter spaces during the pre-op routine. 
     Additionally, catheter design is plagued by the contrasting demands of sturdiness and flexibility. Often catheters are designed with a hypotube inner member to provide sturdiness and resistance to radial collapse and compressive buckling, but the ‘sturdy’ hypotube undesirably resists bending. This sturdiness translates into reduced navigability when traversing tortuous body vessels, such as vasculature. In contrast, polymeric inner members lack the structural strength of hypotubes, while featuring improved navigation capacity due to their flexibility and ability to bend. 
     It would be desirable to overcome the above disadvantages. 
     SUMMARY OF THE INVENTION 
     One aspect according to the present invention provides a catheter inner member that includes an inner member body, including a first side and a second side, the second side opposing the first side. The inner member body includes an inner surface defining an inner member inner lumen and an outer surface defining a surrounding environment. The inner member further includes at least a first flush port and a second flush port in the inner member body. The first flush port and second flush port provide fluid communication between the inner lumen and a surrounding environment. The first flush port disposed on the first side and the second flush port disposed on the second side, wherein the first flush port is axially displaced from the second flush port. 
     Another aspect according to the invention provides an inner member body defining an inner member inner lumen and a surrounding environment. The inner member body further includes at least a first partial circumferential cut providing fluid communication between the inner member inner lumen and a surrounding environment. 
     Another aspect according to the invention provides a catheter system that includes a catheter including a catheter body defining a catheter inner lumen and a surrounding environment. The system further includes an inner member maintained within the catheter inner lumen. The inner member includes an inner member body having a first side and a second side, the second side opposing the first side. The inner member body defines an inner member inner lumen and an outer surface. Furthermore, the inner member body includes at least a first flush port and a second flush port, the first flush port and second flush port providing fluid communication between the catheter inner lumen and the inner member inner lumen. The first flush port is disposed on the first side and the second flush port is disposed on the second side. The first flush port is axially displaced from the second flush port. 
     Yet another aspect according to the invention provides a catheter system that includes a catheter defining a lumen, and a dual lumen inner member within the catheter. The dual lumen inner member defines a first lumen and a second lumen, the first lumen parallel with the second lumen. The first lumen is in fluid communication with a distal tip of the catheter, and the second lumen is in fluid communication with a proximal end of the catheter. The second lumen includes at least a first flush port and a second flush port in the inner member body, the first flush port and second flush port providing fluid communication between the inner lumen and the surrounding environment, the first flush port disposed on the first side and the second flush port disposed on the second side, and wherein the first flush port is axially offset from the second flush port. 
     The foregoing and other features and advantages will become further apparent from the following detailed description, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top view of a portion of an inner member contained within the distal portion of a catheter; 
         FIG. 1B  is a cross section view of the inner member of  FIG. 1A  taken at A-A; 
         FIG. 1C  is a cross section view of the inner member of  FIG. 1A  taken at B-B; 
         FIG. 1D  is a cross section view of the inner member of  FIG. 1A  taken at C-C; 
         FIG. 1E  is a nominal cross section view of the inner member of  FIG. 1A ; 
         FIG. 1F  is a side cross sectional view of an inner member of  FIG. 1A  contained within a catheter, and lines with arrow heads illustrating fluid flow in and out of the inner member; 
         FIG. 1G  is a close-up view of a portion of  FIG. 1F  with lines and arrowheads illustrating fluid flow through and out of an inner member body; 
         FIG. 2  is a view of a first flush port; 
         FIG. 3  is a view of a second flush port; 
         FIG. 4A  is a side view of another embodiment of a catheter inner member; 
         FIG. 4B  is a schematic diagram with lines and arrowheads illustrating fluid flow in and out of the catheter inner member of  FIG. 4A ; 
         FIG. 5  schematically illustrates a cross sectional side view of a another catheter system; 
         FIG. 5A  illustrates the proximal portion of catheter of  FIG. 5 ; 
         FIG. 5B  illustrates the portion of catheter of  FIG. 5  immediately distal to the portion illustrated in  FIG. 5A ; 
         FIG. 5C  illustrates the portion of catheter of  FIG. 5  between that illustrated in  FIGS. 5B and 5D ; 
         FIG. 5D  illustrates the distal portion of catheter of  FIG. 5 , 
         FIG. 6  is a cross section view of a dual lumen inner member taken at A-A of  FIG. 5B ; 
         FIG. 7  is a cross section view of a dual lumen inner member taken at B-B of  FIG. 5C ; and 
         FIG. 8  is a flowchart of a method of flushing a catheter. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments according the invention will now be described by reference to the figures wherein like numbers refer to like structures. The terms “distal” and “proximal” are used herein with reference to the treating clinician during the use of the catheter system: “distal” indicates an apparatus portion distant from, or a direction away from the clinician and “proximal” indicates an apparatus portion near to, or a direction towards the clinician. 
       FIGS. 1A ,  1 B,  1 F, and  1 G illustrate one embodiment of an inner member  100 .  FIG. 1A  illustrates a top view, while  FIG. 1F  illustrates a side view within a catheter (sheath for a self expanding stent system),  FIG. 1B  illustrates a cross section taken at line A-A,  FIG. 1C  illustrates a cross section taken at line B-B, and  FIG. 1D  illustrates a cross section taken at line C-C. Inner member  100  includes an inner member body  110  and a rapid exchange entrance  130 . Inner member  100  includes a first side (top)  115  and a second side (bottom)  125 . The second side  125  is opposite the first side  115 . Inner member body  110  further includes an inner surface  165  ( FIG. 1B ) that defines an inner lumen  160  ( FIG. 1B ) and an outer surface  190  ( FIG. 1B ) defining the inner limits of a surrounding environment  195  ( FIG. 1B ). When a catheter (e.g., outer cover  109 ) surrounds the inner member  100 , the surrounding environment is the space between the inside wall of the catheter and the outer surface  190 . 
     Additionally, inner member body  110  includes at least a first flush port  140  and a second flush port  150 . The first flush port  140  and second flush port  150  provide fluid communication between the inner lumen  160  and a surrounding environment  195 . The first flush port  140  is disposed on the first side  115  and the second flush port  150  is disposed on the second side  125 . In one embodiment, the first flush port  140  is axially displaced from the second flush port  150  along axis  151 . The inner surface  165  can be coated with a polymer coating  191  ( FIG. 1E ), such as PEBAX, in certain embodiments. As an example, the inner member body  110  can be a hypotube, such as a metallic hypotube. 
     The inner member further includes a receptacle for receiving flushing fluid at the distal end of the inner member  110  at tip  158 . The flushing fluid can be any appropriate flushing fluid, such as saline. A portion of a catheter system for delivering a self expanding stent is schematically depicted in  FIG. 1F . The outer cover (catheter)  109  is disposed over a self expanding stent (not shown). To flush the system, fluid is provided to the tip  158  and flushing fluid flows through the inner member inner lumen until the fluid reaches the first opening, e.g., the first flush port  140  in the inner member and subsequent openings. A clinician can cover, or pinch, the rapid exchange entrance  130 , to force fluid to flow further through the inner member and into the catheter inner lumen outside the inner member to fill all the space in the inner member inner lumen and the catheter inner lumen with flushing fluid. To deploy the stent (not shown), the physician holds the handle (not shown) and retracts the thumb button, which is attached to the outer cover to retract it relative to the inner member and thereby release the stent as is well known in the art. 
       FIG. 1F  illustrates fluid flow through an inner member body, such as inner member body  110 , in accordance with one embodiment.  FIG. 1F  is specifically a cutaway side view showing detail of the fluid exit from the flush ports as well as the rapid exchange port. Included in  FIG. 1F  are three close-up views, including a close-up view of the rapid exchange port, and two close-up views at flush ports. Each flush port is located where a stent (not shown in  FIG. 1F ) would be positioned in the catheter prior to deployment such that the fluid flowing through each flush port will flush the stent. 
       FIG. 1G  illustrates fluid flow through an inner member body, such as inner member body  110 , in accordance with one embodiment of the invention. Specifically,  FIG. 1G  illustrates a cutaway side view illustrating a rapid exchange port.  FIG. 1G  illustrates block  149  disposed within the inner member and providing a fluid seal to reduce flow of the flushing fluid proximal of the rapid exchange port. The block  149  can be any appropriate material, such as an adhesive, polymer, or metal configured to substantially reduce fluid flow past the block. As fluid flows from the tip of the inner member through the lumen and out the rapid exchange port, the block  149  directs any fluid that traverses the distance from the tip to the rapid exchange port out of the inner member via the rapid exchange port.  FIG. 1G  also illustrates the fluid flow exiting the inner member via the rapid exchange port. 
       FIGS. 2 and 3  are plan views of flush ports such as  140  and  150  in  FIG. 1F . 
       FIG. 4A  is a side view of another embodiment of a catheter inner member  400  including an inner member body  410 . The inner member is, in one example, a hypotube, with or without an internal polymer coating, such as PEBAX. Inner member  400  includes rapid exchange port  405 . Inner member body  410  defines an inner lumen within the inner member body  410  and a surrounding environment outside the inner member body  410 . When inner member body  410  is within a catheter, the surrounding environment is defined by the space between the inner wall (surface) of the catheter and the outer surface of the inner member body. 
     Additionally, inner member body  410  includes at least a first incomplete circumferential cut  498 . An incomplete circumferential cut is a cut into the wall of the inner member body, but not around the whole circumference, thus leaving an un-cut connection between inner member body sections on each side of the cut. Any number of incomplete circumferential cuts may be included along the length of the inner member body. Such circumferential cuts may extend radially about the body, or extend spirally about the body. Such circumferential cuts can be through cuts, extending through the inner member body, providing fluid communication between the inner lumen and a surrounding environment. Alternatively, such circumferential cuts can extend from the outer surface radially a fraction of the thickness of the inner member so that the circumferential cuts do not provide fluid communication between the inner lumen and the surrounding environment, but do provide reduced resistance to bending. Furthermore, a single inner member body can have varying circumferential cuts, with some cuts radial, some cuts spiral, some cuts through cuts, and other cuts only partial. 
     Additionally, inner member body  410  includes a flush port portion  425  and a cut portion  435 , wherein the cut portion  435  is axially offset from the flush port portion  425 . Further, inner member body  410  includes a plurality of flush ports axially offset from each other and disposed on opposing sides of the inner member body  410 . For example, each flush port is implemented as flush ports  140 ′ or  150 ′, similar to flush ports  140  and  150  described with reference to  FIGS. 1A-1D  and inner member  100 . 
     The lumen of inner member body  410  is in fluid communication with a fluid source for providing a flushing fluid, such as a saline solution. The cut portion is disposed between the fluid source and the flush port portion. 
       FIG. 4B  is a schematic illustration where the arrows designate the direction of fluid flow through the inner member  400 , and through the flush port portion  425 . 
       FIG. 5  schematically illustrates a portion of another embodiment of a catheter system  500 . Catheter system  500  includes catheter body  510  ( FIG. 5D ) that defines a catheter inner lumen and a surrounding environment. Additionally, system  500  includes a dual lumen inner member  508  ( FIG. 6 ,  FIG. 7 ) disposed within the catheter inner lumen. 
     FIGS.  5  and  5 B- 5 D illustrate the distal portion of a catheter, including the distal tip  511 , the distal outer sheath  512 , outer guide wire exit port  513  and an inner guide wire exit port  514 . Specifically,  FIG. 5  illustrates a cross sectional side view of a catheter  500 , with  FIGS. 5A-5D  illustrating close up views of catheter  500 , such that  FIG. 5A  illustrates the proximal portion of catheter  500 ,  FIG. 5B  illustrates the portion of catheter  500  immediately distal to  FIG. 5A ,  FIG. 5D  illustrates the distal portion of catheter  500 , and  FIG. 5C  illustrates the portion of catheter  500  between  FIGS. 5B and 5D . The structures illustrated in FIGS.  5  and  5 A- 5 D are not to scale. Two flush ports  150 ′ and  150 ″ are illustrated in  FIG. 5C  although either fewer or more flush ports can be included. Additionally,  FIG. 5C  illustrates a stent  599  disposed in the catheter between the distal outer sheath  512  and inner member body  508 . 
     Dual lumen inner member  508  includes a first lumen  524  and a second lumen  526 . The first lumen  524  is parallel with the second lumen  526 . The first lumen  524  is in fluidic communication with a fluid receptacle at the distal tip  511 , so that when a flushing fluid is introduced into first lumen  524  at the distal tip of the catheter, the fluid displaces air from the guide wire lumen. Second lumen  526  is in fluid communication with a flush port in the handle and includes a hypotube  871 ′ ( FIG. 6 ) for at least a portion of the length, and is in communication with and each flush port  150 . Introduction of fluid at the handle then flushes the rest of the catheter. In the embodiment illustrated in  FIG. 5 , after a finger in placed over the (rapid exchange) outer guide wire exit port  513  the flushing fluid can be introduced at either or both the proximal and distal ends. 
       FIG. 6  illustrates a cross sectional view of catheter  500  taken at A-A, and  FIG. 7  illustrates a cross sectional view of catheter  500  taken at B-B in  FIG. 5C .  FIG. 6  and  FIG. 7  each show dual lumen inner member  508 . In  FIG. 6 , hypotube  871 ′ is seen lining the second lumen  526 . 
     The catheter  500  can be flushed in a one step flushing process, whereby a finger is placed over the outer guide wire exit port  513  flushing fluid is introduced either at the distal tip or at the proximal end. Catheter  500  is flushed in one step from either end of the catheter (from the tip or from the luer port at the handle) with a finger covering the RX wire exchange port. The flushing fluid flows from the tip through the guidewire lumen and around the stent and into the end of the hypotube as well as into the two flush ports  150 ′ and  150 ″ or alternately the flushing fluid flows from the luer fitting on the handle through the hypotube and out the end of the hypotube and the two flush ports  150 ′ and  150 ″ to bathe the stent and reach the guidewire lumen to pass through the guidewire lumen and out the end of the tip. Depending on the physical characteristics of the catheter (such as inner diameter and length), flushing performance may be improved by flushing from both the tip and luer ports. In such instances, each end can be flushed either simultaneously, or sequentially. 
       FIG. 8  illustrates the steps of a method  600  of flushing a catheter. Method  600  includes providing a catheter with an inner member during step  610 . The inner member is implemented as inner members  100 ,  400 , or  500 . The catheter is attached, at step  620 , to a flushing fluid supply, and the flushing fluid thereby flows under pressure, step  630 , into the lumen of the inner member. In one example, the fluid is supplied from a syringe placed into fluid communication with a distal tip of the catheter. As it flows, the flushing fluid passes through at least one of the flushing ports and/or circumferential cuts in step  640 . This passing of the flushing fluid flushes the catheter and inner member, as well as any stent or other medical device in the path of the fluid flow. 
     While specific embodiments according to the invention are disclosed herein, various changes and modifications can be made without departing from the spirit and scope of the invention.