Apparatus with visual marker for guiding deployment of implantable prosthesis

An apparatus for use by an operator in a cavity of a mammalian body with a scope having a distal face providing a field of view. The apparatus includes a flexible elongate member having a distal extremity adapted for extending into the cavity and a proximal extremity accessible from outside of the mammalian body when the distal extremity is disposed in the cavity. An expandable prosthesis is releaseably secured to the distal extremity of the flexible elongate member. A visual marker capable of being seen by the operator in the field of view is secured to one of the distal extremity of the flexible elongate member and the prosthesis for facilitating placement of the prosthesis in the mammalian body.

SCOPE OF THE INVENTION

The present invention relates to apparatus for deploying implantable prostheses within mammalian bodies and more particularly to apparatus for deploying stents within human bodies.

BACKGROUND

Delivery systems have been provided for the deployment of stents and other prostheses. Such delivery systems, for example, have been used for the percutaneous implantation of vascular prostheses. See in this regard U.S. Pat. No. 5,653,748 issued Aug. 5, 1997, the entire content of which is incorporated herein by this reference. Delivery systems have also been provided for esophageal stenting. See in this regardUltraflex™ Esophageal Stent System, The Total Approach to Esophageal Stenting, copyrighted in 1998 by Boston Scientific Corporation, the entire content of which is incorporated herein by this reference (the “Ultraflex Article”).

Endoscopically placed stents are often delivered with the aid of fluoroscopy. For example, radiopaque markers can be affixed to the delivery system or the stent itself and aligned with external radiopaque markers placed on the body of the patient. Unfortunately, fluoroscopically aided delivery systems can undesirably expose the patient and the operating physician to x-rays. In addition, such systems require the use of expensive equipment that can require further expense to set up for a procedure. It would thus be desirable to provide a delivery system which overcomes these disadvantages.

Stents have previously been encased in colored gelatin to bind the stent to the delivery system in place of a crocheted suture or other stent securement means.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for use by an operator in a cavity of a mammalian body with a scope having a distal face providing a field of view. The apparatus includes a flexible elongate member having a distal extremity adapted for extending into the cavity and a proximal extremity accessible from outside of the mammalian body when the distal extremity is disposed in the cavity. An expandable prosthesis and means for releaseably securing the prosthesis to the distal extremity of the flexible elongate member are provided. A visual marker capable of being seen by the operator in the field of view is secured to one of the distal extremity of the flexible elongate member and the prosthesis for facilitating placement of the prosthesis in the mammalian body.

DESCRIPTION OF THE INVENTION

In general, apparatus21of the present invention is for use in deploying a prosthesis22in a cavity23of a mammalian body24(seeFIGS. 1-3). The apparatus21includes an elongate device26and the prosthesis22is mounted on a distal portion of the device26. In one preferred embodiment, the body24is a human body and cavity23is any suitable lumen, passage or passageway in the body, for example the gastrointestinal tract23extending from the mouth27to the anus (not shown). A portion of the gastrointestinal tract is shown inFIG. 1and includes the esophagus28, formed by a tubular wall29, and the stomach30.

Device26can be of the type described in the Ultraflex Article. In general, device26comprises a flexible elongate member or shaft31having a proximal extremity31aand a distal extremity31b(seeFIG. 2). A handle32is formed on proximal extremity31aand the shaft31is provided with at least one lumen or passageway33extending from the proximal extremity31ato the distal extremity31bthereof.

A stent22or other suitable prosthesis is removably mounted on distal extremity31bof shaft31(seeFIGS. 3-9). Stent22can be of the type disclosed in U.S. Pat. No. 5,662,713 issued Sep. 3, 1997, the entire content of which is incorporated herein by this reference. In general, stent22includes at least one mesh36formed from at least one wire37made from metal or any other suitable material and having a length ranging from six to 15 centimeters. The wire37is preferably made from a shape memory alloy such as Nitinol. As illustrated inFIG. 7, wire37is knitted into a plurality of overlapping loops38. The elongate stent22extends along a longitudinal axis41and has a first or proximal end portion22aand a second or distal end portion22b, one or both of which can be flared, and corresponding first and second ends42,43. The stent can optionally include a membrane44extending around at least a portion of the length of the wire mesh36and preferably between the proximal and distal end portions22aand22bof the stent. Membrane44can be a semi-permeable compliant membrane made from any suitable material such as expanded polytetrafluoroethylene (teflon), latex or silicone and preferably silicone. Stent22, as shown inFIG. 9, has a proximal end portion22awhich is flared, a distal end portion which is not flared and a membrane44extending therebetween.

Means is included within apparatus21for releaseably securing prosthesis22to distal extremity31bof device26. One preferred means is a mesh51extending along at least a portion of the length of the prosthesis22(seeFIGS. 2-3). The mesh51is preferably formed of a crocheted material such as of the type disclosed in U.S. Pat. No. 5,653,748. In this regard, mesh51can be formed from a thread52having a plurality of loops53extending around the prosthesis. The thread52is preferably black in color and is secured to shaft31at one end of the mesh51by any suitable means such as a flexible band54made from an elastomeric or other suitable material (seeFIGS. 3-5). Band54is shown inFIGS. 3-5as being located adjacent the proximal end portion22aof the stent, the end at which release of the stent from device26commences. Threaded mesh51preferably extends along the entire length of the stent22and more preferably beyond each of the ends.42and43of the stent22, as illustrated inFIG. 3with respect to the proximal end of the stent. One end of the thread52extends proximally of stent22along the outside of shaft31before passing through an opening, porthole or skive56provided in the side of shaft31and communicating with an internal passage, such as passage33, extending to proximal extremity31aof the device26. The proximal end of thread52is connected to a suitable finger actuatable member such as pull ring57, illustrated inFIGS. 1 and 2, which can be pulled away from handle32to commence the unraveling of the crocheted material of mesh51in a manner described in U.S. Pat. No. 5,653,748. Such unraveling of the mesh causes the expandable stent22to commence disengaging from device26in the manner disclosed in the Ultraflex Article. Thread52is thus included within the releasing means of apparatus21which is operable from the proximal extremity of shaft31.

A visual marker61capable of being seen under direct vision is secured to one or both of the distal extremity31bof the shaft31and the stent22for facilitating placement of the stent in the body24. Visual marker61can be of any suitable type and is preferably secured or otherwise coupled to the stent22or mesh51and preferably to the mesh51. Apparatus21is preferably utilized with a scope62that is extendable into the body cavity23alongside the device26to permit direct visualization of the marker61within the cavity23. As illustrated inFIG. 2, scope62has a distal face63providing a field of view to the operator so as to permit such visualization of the marker61. In addition, the scope is preferably coupleable to a light source and includes an optical fiber for illuminating the field of view.

In the embodiment of apparatus21shown inFIGS. 1-9, the visual marker61is in the form of a colored band66extending around mesh51, which binds down stent22prior to the stent's deployment. Band66can be placed at any suitable position along the length of prosthesis22and can have a length, that is in the longitudinal direction of the stent22, ranging from two to fourteen millimeters and preferably from nine to fourteen millimeters. The band66can be of any suitable color, such as black, blue, green, yellow, red or purple, which preferably contrasts with the color of the threaded mesh51and further preferably contrasts with the color of stent22and is easily seen under the light from scope62. The colored band66can be made of any suitable material such as silicone or another polymer. Band66is preferably a tubular member that is more preferably single walled, and can be extruded from a Silastic material sold by Dow Corning Corporation of Midland, Mo. When such Silastic material is used, band66can be swelled in a suitable solvent such as Forane 141B, Heptane or HCFC and then slipped over the distal end of device26and stent22for placement at the desired position on the stent. Before contraction of the Silastic material of the band66, the free end of thread52can be looped between the band66and stent22or between the band66and the mesh51before extending the thread52proximally through skive56.

Band66is preferably placed a distance from one end42or43of the stent22equal to the length to which the stent shrinks, contracts or foreshortens when released from the device26. In this regard, the wire mesh body36of stent22is moveable from a first or contracted position in which the stent has an expanded length and a reduced diameter, as shown inFIGS. 1-6, and a second or expanded position in which the stent has a reduced length and an expanded diameter, as shown inFIG. 9. As such, the stent22has a first or extended length when secured to the shaft31, as shown inFIGS. 1-6, and a second or reduced length shorter than the first length when fully released from the device26and expanded against the wall of the cavity23, as shown inFIG. 9. Actuation of pull ring57and the subsequent release of thread52from band54results in the outward expansion of wire mesh36and the simultaneous reduction in length of stent22in a wave-like or sequential manner along longitudinal axis41(seeFIGS. 7-9). As discussed above, the release of stent22commences at its proximal end portion22a, and thus stent22contracts distally in length during its release sequence. Colored band66is placed a distance from the distal end22bof the contracted stent22equal to the length that the stent22will assume when fully released from device26.

Radiopaque or other markers can be placed on device26and/or stent22to permit fluoroscopic visualization, in addition to the direct visualization through scope62, of the markers and/or stent22during deployment. For example, radiopaque markers67can be provided on shaft31of the device26.

In operation and use, distal extremity31bof the shaft31of apparatus21is adapted for extending into the cavity23of the body24. Proximal extremity31aof the shaft is accessible from outside of the body24when the distal extremity31bis disposed in the cavity23. In one preferred method of using apparatus21, scope62is advanced through mouth27and esophagus28to the vicinity of a stricture71having opposite first or proximal and second or distal margins71aand71band formed by a cancerous or other growth72in the wall29of the esophagus28to locate the proximal and distal margins71aand71bof the stricture. In this step, the scope is advanced to the distal margin71band the depth of insertion from the patient's incisors recorded. The scope is then retracted to the proximal margin71aand the position recorded. The difference of these two measurements is the length of the stricture. With the distal extremity of the scope62located at the proximal margin71aof the stricture, the distal extremity of device26is then introduced (seeFIGS. 1-9). As part of the method for introducing device26into body24, a guide wire (not shown) can be first placed in the esophagus28and thereafter apparatus21advanced over the guide wire to the desired location. The guide wire is pulled from the proximal extremity of apparatus21leaving device26and stent22within the esophagus28. The operator utilizes handle32of device26to move shaft distal extremity31band align visual marker61with the distal extremity of the scope62and thus the proximal margin71aof stricture71. The movement of visual marker61can be visualized by the operator by means of scope62.

Once visual marker61has been so desirably aligned relative to the wall29forming esophagus28, and the growth72formed in the wall29, the distal extremity of scope62is retracted to a position proximal of stent22so as to be out of the way during stent deployment. For example, the distal extremity of the scope62can be retracted to skive56. The operator pulls ring57to commence the removal of marker61from the bound down stent22and the subsequent deployment of the stent22from shaft distal extremity3lb. The pulling of ring57and thread52attached thereto causes colored band66to fold back on itself and roll proximally along the stent22after the band66is moved from its initial or home position ofFIG. 3.FIG. 4shows colored band66after it has been moved from its home position on the stent. InFIG. 5, the colored band66has been moved further proximally on stent22and is approaching the proximal end of wire mesh51.FIG. 6shows the colored band66after it has been pulled completely off mesh51and thread52has been released from securing band54. InFIG. 7, the colored band66has moved further proximally on shaft31by the continued pulling of thread52and the proximal end portion of the crocheted mesh51has been released to permit expansion of the proximal end portion22aof the stent22.FIG. 8shows stent22and device26within esophagus28after the stent has been further released from the position ofFIG. 7. InFIG. 9, the stent22has been fully deployed and the distal end of thread52is shown free from the stent22and distal extremity31bof shaft of31. Membrane44and the base of proximal end portion or flare22aand distal end portion22bare shown covering the stricture71. The expanded stent22forces the wall29of esophagus28outwardly at stricture71so as to increase the size of the opening or passageway of the esophagus28at stricture71and thus enhance flow through the growth72.

Once expandable stent22has been fully deployed within esophagus28, device26is pulled upwardly through the stent22and out of esophagus28. Colored band66is appropriately sized so as to remain on shaft31during the removal of device26from human body24.

As can be seen, visual marker61facilitates placement of the stent22within esophagus28by permitting the operator to longitudinally position the stent within the esophagus28at a position which anticipates the foreshortening of the stent during deployment. When the stent is deployed from its proximal end, for example, marker61permits the operator to predict where the proximal end42of the stent will rest on the esophageal wall29after the stent has been deployed and can thus make proper placement of the stent in the stricture71easier. Apparatus21allows placement of stent22without the need of fluoroscopy. As such, the patient and operator are not exposed to undesirable x-rays during the placement procedure. Apparatus21eliminates inaccuracies associated with stent placement relative to external markers, which can move during the procedure, by not requiring the use of such external markers. Savings in the cost of a stent placement apparatus may be achieved by apparatus21. Further, stents22and other prostheses can be placed in outpatient surgery centers that do not have fluoroscopic equipment available.

Although stent22has been described and disclosed as being released from its proximal end portion22aso as to expand in a distal direction, it should be appreciated that the stent can be released from its distal end portion22band expand in a proximal direction and be within the scope of the present invention. In this embodiment and procedure, the stent22contracts proximally in length during its release sequence. Colored band66would be placed a distance from the proximal end22aof the contracted stent22equal to the length that the stent22will assume when fully released from device26.

The visual marker of the present invention can be broadly defined as any characteristic or feature included in the apparatus21, whether on the prosthesis22, device26and/or elsewhere on the apparatus21, which can be observed under direct visualization so as to facilitate placement of the stent or other prosthesis within the mammalian body. Accordingly, other embodiments of the visual marker can be provided. For example, the visual marker of the present invention can be a colored marker81looped around thread52and bound to stent22by thread52(seeFIG. 10). In one preferred embodiment, colored marker81is a flat piece of paper, polymer or other plastic having a fold82around thread52, for example at one of loops53of the thread52. Marker or flag81can have a size similar to the size of marker61and can extend around all or less than all of the circumference of the stent22. The folded halves of colored marker81, extending from fold82, are secured together by any suitable means such as an adhesive. The colored marker81is then flattened against the outer cylindrical surface of stent22and such flattened portioned secured to the stent by other loops53of the thread52so as to be positioned under mesh51.

The operation and use of apparatus21having colored marker81thereon is substantially similar to the operation of apparatus21discussed above. The colored marker81is removed from stent22by the unraveling of threaded mesh51. Fold82serves to retain the colored marker81on thread52after the marker81is freed from stent22. Colored marker81is pulled with thread52up to skive56, which is smaller than the colored marker81and thus precludes the marker81from being pulled through device26. As mesh51is further unraveled, thread52is pulled through fold82. A knot or other suitable means is formed at the end of thread52for precluding the thread from being pulled through the colored marker81. As a result, the colored marker81is removed from body24with the removal of device26.

In a further embodiment, visual marker91is formed by an additional thread92which is tightly wound around a portion of the stent22to form a plurality of closely spaced loops at the desired location of the marker. Visual marker91is illustrated inFIG. 11, where additional thread92has been colored so as to distinguish it from thread52. Marker91can have a size similar to the size of marker61. Additional thread92is preferably of a different color than thread52and stent22, such as white or green, so as to be easily viewed by the operator looking through scope62of apparatus21. In one preferred embodiment, a pair of adjacent loops53of threaded mesh51are spaced apart a sufficient distance, for example a distance ranging from two to twenty millimeters and preferably ranging from two to ten millimeters, so as to permit a sufficient length of the additional thread92to be tightly wound between the adjacent loops53. One end of thread92is secured to threaded mesh51or device26any suitable means. For example, such end of thread92can be secured to shaft31proximal of the stent22by a band similar to band54or can be releaseably tied to or tucked under the thread52of mesh51. The other end of the thread92extends proximally, for example along the thread52, before entering skive56and traveling to proximal extremity31a of shaft31and handle32. The proximal end of the additional thread92can be wound within the shaft31to the thread52and, like the thread52, can be secured to pull ring57.

In operation and use, apparatus21having visual marker92thereon can be utilized in the manner discussed above with respect to markers61and81. In a preferred method of operation, the operator pulls ring57to commence the simultaneous unraveling of thread92and thread52. As a result of a difference in length of threads52and92, that is the length of thread52from ring57to the proximal loop53adjacent visual marker91is greater than the length of thread92from ring57to visual marker91, the marker91unravels before the portion of threaded mesh51in the vicinity of marker91unravels so that the stent22is not released until after the visual marker91has been removed from the stent. Entanglement of thread52with thread92in the vicinity of visual marker91is thus minimized.

In a further embodiment, shown inFIG. 12, a portion of mesh51in the location where a visual marker is desired, is tightly spaced around stent22so as to create a densely spaced portion of the threaded mesh51which is visually distinct from the remainder of the mesh51by virtue of the tight or close spacing of successive loops. Such a visual marker101can be further distinguished from the remainder of threaded mesh51by applying a colored ink to such tightly wound portion of the mesh51. Different printing methods can be used, for example pad printing, jet printing or straight painting, to apply the colored ink to the tightly wound portion of mesh51forming marker101. The types of inks used include fluorescent dyes and inks approved for medical devices.

An apparatus21having visual marker101thereon can be utilized in the manner discussed above with respect to markers61,81and91. Visual marker101is removed from the stent22by unraveling threaded mesh51during the release of the stent.

In another embodiment, a visual marker106can be provided on stent22by applying a bioabsorbable material around the threaded mesh51and stent22at the desired location on the contracted stent. The bioabsorbable material of marker106can optionally be applied over one or more of the loops53of mesh51or merely in between adjacent loops53. Although visual marker106is shown inFIG. 13as being applied circumferentially around the stent22, it should be appreciated that the material of visual marker106can be applied less then circumferentially around the stent22and/or as a plurality of longitudinally spaced-apart arcuate strips to form the visual marker. The bioabsorbable material forming the visual marker can be of any suitable type, for example a gelatin, and is preferably of a color that is different than the color of thread52and stent22.

In operation of apparatus21having visual marker106thereon, once distal extremity31bof shaft31and stent22thereon have been placed within cavity23, the dissolving of the material of visual marker106commences. The dissolving rate is slow enough to allow the operator to visualize the marker106and desirably position the stent22. In one preferred method of operating apparatus21with marker106thereon, the operator waits a sufficient period of time for marker106to dissolve before releasing threaded mesh51and permitting stent22to open in the cavity23.

Radiopaque material can be included within the material of stent22, such as membrane44thereof, and/or within the material of any of the visual markers hereof and, as discussed above, radiopaque markers can be placed elsewhere on device26and/or stent22to permit fluoroscopic visualization of the markers and/or stent22during deployment. In addition, any of the visual markers of the present invention can be provided with a colorant to enhance visualization.

In a further embodiment of the invention (not shown), a visible marker can be attached directly to device26or other delivery system beneath the stent or other prosthesis22. Such an embodiment can be particularly advantageous when the stent or other prosthesis22permits visualization of such marker beneath the stent or prosthesis.

Although the visual markers of the present invention have been described for use with a stent deployed in the esophagus, such markers are equally suitable for use with any other implant, prosthesis or device that is placed, delivered or deployed under endoscopic or direct visualization. For example, the visual markers hereof can also be used with pulmonary and colonic stents, urethral stents, duodenal stents, any other stent that can be deployed under endoscopic or direct visualization, endoscopic devices and any crochet or other type of delivery system.

As can be seen from the foregoing, the visual markers of the present invention advantageously permit the placement of a prosthesis without the need of fluoroscopy. As a result, fluoroscopic equipment set up and film preparation can be eliminated and operator exposure to x-rays minimized. The visual marker facilitates accurate placement of the prosthesis. Where the prosthesis is a stent or other device that contracts in length during deployment, the visual marker can be utilized to anticipate such contraction in length.