Patent ID: 12251300

DETAILED DESCRIPTION

FIG.1shows a diametrically adjustable endoprosthesis10, according to some embodiments. As shown, the endoprosthesis10includes a stent12, also described as a stent element or support. The stent12has a first segment14and a second segment16. As shown, a base graft18, also described as a first graft portion, a cover or a liner, is provided along the length of the first segment14, while a portion of the second segment16extends beyond the base graft18and is left largely uncovered. The terms “graft,” “cover,” and “liner” are used interchangeably herein, and are not meant to require a certain relative position with respect to the stent12. A “liner” may surround the stent12, a “cover” may be received entirely within the stent12, and a “lined region” corresponds to a portion of an endoprosthesis including a graft layer, regardless of whether the graft resides inside, outside, sandwiches, or is otherwise positioned relative to a stent element. The endoprosthesis10also includes a controlled expansion element20, also described as a second graft portion. InFIGS.1and3, the controlled expansion element20is called out with cross-hatching inFIGS.1and3for ease of visualization. The controlled expansion element20extends along at least a portion of the base graft18and optionally enhances or augments one or more functions of the base graft18, for example serving as a functional graft component of the base graft18. As shown, the endoprosthesis10has a proximal end22and a distal end24and defines an inner lumen26(FIG.2). In order to facilitate placement of the endoprosthesis10, radiopaque markers are provided along the length of the endoprosthesis10as desired.

As shown inFIG.1, the assembled endoprosthesis10includes a graft-lined region28and an unlined region30, although in other designs the entire endoprosthesis10is lined and is characterized by an absence of an unlined region. In intrahepatic portosystemic shunt configurations, the graft-lined region28corresponds to an intrahepatic region and the unlined region30corresponds to a portal region. The graft-lined region28defines a first end portion32, a middle portion34, and a second end portion36. The border between the graft-lined region28and the unlined region30is indicated by a circumferential radiopaque gold marker band38proximate, or just proximal to, the border. An additional radiopaque gold marker is optionally located on the proximal end22of the endoprosthesis10.

The middle portion34of the graft-lined region28, and in particular the portion of the endoprosthesis10corresponding to the controlled expansion element20, forms a diametrically controlled portion of the endoprosthesis10. As shown, the diametrically controlled portion of the endoprosthesis10(the middle portion34inFIG.1), extends for less than an entire length of the endoprosthesis10, and in particular less than a full length of the graft-lined region28, although in other embodiments the controlled expansion extends for any desired length, including the full endoprosthesis length as desired.

As shown, the middle portion34corresponding to the controlled expansion portion of the endoprosthesis10has a first flared end40, a central portion42, and a flared second end44. The first and second flared ends40,44taper in different directions and at taper angle relative to the longitudinal axis of the endoprosthesis10(e.g., at a relative angle from about 10-80 degrees, including any value therebetween, such as about 60 degrees). Although the flared ends40,44are shown with generally linear tapers, curved tapers, re-curved tapers, combined linear and curved tapers, and others are contemplated. The first and second flared ends40,44help provide a smooth transition to the adjacent, first and second end portions32,36when the endoprosthesis10is in an unconstrained state following initial deployment. Although the central portion42is shown as having a substantially uniform diameter, the central portion42optionally includes one or more tapers as desired, as can any of the other portions of the endoprosthesis10.

The middle portion34of the graft-lined region28is constrained with the controlled expansion element20such that the endoprosthesis10exhibits an initial diametric expansion limit at the middle portion34to which the endoprosthesis10is deployed and which the endoprosthesis maintains prior to one or more subsequent mechanical adjustment steps. As shown inFIG.1, the expansion element20causes the middle portion34to take on a dog-bone shape or hourglass shape, although any of a variety of shapes are contemplated. As shown inFIG.1, the endoprosthesis10defines a minimum inner diameter (ID) at a boundary46between the central portion42and the first flared end40.

The diameter of the endoprosthesis10in the middle portion34is smaller than the adjacent portions of the endoprosthesis10because the controlled expansion element20diametrically constrains self-expansion of the stent12, but is able to be mechanically adjusted by a distensive force (e.g., using a balloon catheter) to allow diametric adjustment. To that end, if the controlled expansion element20was removed from the endoprosthesis10the stent12and base graft18would tend to self-expand to a maximum diametric expansion limit. In particular, the stent-graft12,18is configured to expand to a maximum diameter (e.g., the manufactured diameter of the stent-graft) at which point further expansion is significantly resisted (e.g., resistance of 1000 ATM or more) and may even result in failure if an attempt to force the stent-graft18beyond that diameter is attempted. The stent12, the graft18, or the combination of the stent-graft12,18can be configured to set this maximum diametric adjustment limit, beyond which the endoprosthesis10is not intended to be diametrically adjusted. In the same way, if balloon dilation is used to diametrically expand the controlled expansion element20, middle portion34will expand correspondingly, up to a diameter of the adjacent, first and second end portions32,36(e.g., as shown inFIG.3) which represent the fully expanded diameter of the stent—graft12,18.

FIG.3shows the endoprosthesis10expanded to a maximum diametric expansion limit imparted by the remainder of the endoprosthesis10, for example imparted by the base graft18. As shown, the lined region28has a maximum diametric expansion limit corresponding to the base graft18having a continuous cylindrical profile through the first end portion32, the middle portion34, and the second end portion36. As previously referenced, the stent-graft12,18may have an “as manufactured” diameter, beyond which the stent-graft12,18is not meant to expand in typical use, whether under physiological conditions or by balloon expansion.

In one example, the ID of the endoprosthesis10upon deployment at the middle portion34is approximately 8 mm and is expandable to approximately 10 mm. In some examples, the ID of the endoprosthesis10at the middle portion34(e.g., as measured at the minimum ID location46) is expandable by 12% to 40%, for example. In still other embodiments, the endoprosthesis10at the middle portion34is expandable greater than 40%, such as up to 70% or even more.

For application in a TIPS procedure, the endoprosthesis10would typically have dimensions as follows: a length of about 5 to 12 cm, with a length of about 6 to 10 cm being more typical; a deployed diameter of about 5 to 14 mm, with a diameter of about 8 to 12 mm being more typical; and a total wall thickness of about 0.1 to 1.0 mm, with about 0.1 to 0.6 mm being more typical. While the dimension “diameter” is used herein, it should be understood that this dimension is intended to define an average cross-sectional dimension and is not intended to limit designs to circular cross-sectional shapes. Moreover, as shown inFIG.1, the endoprosthesis10may be configured to exhibit multiple average cross-section dimensions along the length of the endoprosthesis10, including tapers along different portions of the endoprosthesis10.

In some embodiments, the endoprosthesis10itself has a compacted dimension suitable for endoluminal deployment, such as less than or equal to 16 French (5.3 mm), although a variety of dimensions are contemplated depending upon the treatment in which it is applied. In some embodiments, in order to be delivered percutaneously, the endoprosthesis10and its deployment apparatus have a diameter of less than about 13 French (4.3 mm), for example, although a variety of dimensions are contemplated. “French” measurements as used herein define the size of a hole through which a device will pass. For example, a device with a measurement of “10 French” will pass through a 10 French hole (which has a diameter of 3.3 mm). Again, the device need not have a circular cross-section in order to pass through a circular 10 French hole so long as the hole is large enough to accommodate the widest cross-sectional dimension of the endoprosthesis10.

The first segment14of the endoprosthesis10will typically comprise about 50 to 90 percent of the entire length of the endoprosthesis10. Accordingly, the first segment14will typically be about 4 to 8 cm in length and the second segment16will typically be about 1 to 3 cm in length, although a variety of dimensions are contemplated. The middle portion34of the graft lined region28corresponding to the controlled expansion element20typically has a total length of about 1 to 11.5 cm, where the first flared end40has a length of about 0.25 to 1.5 cm, more typically 0.5 cm, the central portion42has a length of about 0.5 to 8.5 cm, with 1.5 to 5.5 cm being more typical, and the flared second end44has a length of about 0.25 to 1.5 cm, with 0.5 cm being more typical, although a variety of dimensions are contemplated.

The stent12optionally includes any number of segments and configurations, according to various embodiments. As shown inFIG.1, the first segment14has an undulating, helical stent pattern, although other configurations are contemplated. In turn, the second segment16optionally employs a different stent pattern from that of the first segment14. For example, the second segment16is shown with an interlocked (or “chain-linked”) stent pattern that helps prevent the second segment16from excessively longitudinally elongating beyond a predetermined desired length, although other configurations are contemplated. In some interlocked designs, a single wire is employed for the second segment16, where the wire is wrapped from the cover18to a distal end24of the endoprosthesis10and then back to the cover18such that the wire terminates within the cover18and avoids having a loose end of the wire exposed at the distal end24of the endoprosthesis10.

In some methods of forming the interlocked (or “chain-linked”) stent pattern of the second segment16a single wire is wrapped from the first segment14to the distal end24of the endoprosthesis10and then back to the first segment14. Along the length of the second segment16the wire is provided with a second undulated pattern along a first pass and a third undulating pattern, interlocking with the second undulating pattern along a second pass. By interlocking the second undulating pattern and the third undulating pattern, the stent pattern permits the second segment16to be longitudinally compressed, thus imparting flexibility; but the stent pattern prevents the second segment16from being longitudinally elongated beyond a predetermined maximum length. It should be noted that the interlocked stent pattern also imparts columnar support when the device is in a radially compressed configuration and less so when it is deployed. Examples of suitable stent patterns and associated methods of manufacture for the first and second segments are also described in U.S. Pat. No. 6,673,102 to Vonesh et al.

The first and second segments14,16of the stent12may be formed from a variety of wire materials, including stainless steel, nickel-titanium alloy (nitinol), tantalum, elgiloy, various polymer materials, such as poly(ethylene terephthalate) (PET) or polytetrafluoroethylene (PTFE), or bioresorbable materials, such as levorotatory polylactic acid (L-PLA) or polyglycolic acid (PGA). In various examples, the stent12is self-expanding and exerts a self-expansion force on the endoprosthesis10when constrained. As such, in various designs the first and second segments14,16of the stent12are formed of superelastic materials, such as nitinol metal, that will withstand tight compression in a compacted configuration (diameter) and then self-expand to a deployed configuration (diameter) once released in place, such as those described in U.S. Pat. No. 6,673,102 to Vonesh et al.

Although the endoprosthesis10is generally described as including a self-expanding stent12, it should be understood that the stent12may include one or more balloon expandable portions (e.g., the second segment16may be balloon expandable) or the entire stent12may be balloon expandable with the endoprosthesis10being free of any self-expanding stent components. For example, the controlled expansion element20is optionally employed with a balloon expandable stent-graft and allows diametric adjustment beyond an initial deployment diameter through a plurality of adjusted diameters up to a maxim diametric expansion limit of the balloon expandable stent-graft.

In general terms, the cover18helps provide the endoprosthesis10with a flow lumen. In intrahepatic shunt applications, the cover18performs a number of functions in the endoprosthesis10, including preventing extrusion of liver tissue through the stent12, maintaining the maximum diametric dimensions of the endoprosthesis10, preventing uncontrolled elongation of the stent12, reducing or eliminating bile from permeating into the shunt, and facilitating bending without kinking, for example. As previously described, the controlled expansion element20optionally enhances or augments one or more functions of the base graft18beyond diametric adjustability. For example, the controlled expansion element20optionally provides enhanced impermeability performance, longitudinal strength, or others.

As shown inFIG.2, the preferred material for the base graft18includes a base tube48a, an inner film48b, and an outer film48c. The base tube48amay be a fluoropolymer material and especially expanded polytetrafluoroethylene (PTFE). The inner film48bis also optionally a fluoropolymer, and especially expanded PTFE. For example, the base tube48amay be an extruded, thin-walled expanded PTFE base tube and the inner film48ba plurality of layers of expanded PTFE film helically wrapped over the base tube. The outer film48cis also optionally a fluoropolymer, such as a porous composite film of FEP and expanded PTFE. Examples of suitable materials for base tube48a, inner film48b, and outer film48care described in U.S. Pat. No. 6,673,102 to Vonesh et al. As shown, the base graft18is substantially continuous and uninterrupted in that the wall does not have any apertures or holes of sufficient size to remain patent in vivo, although grafts18with apertures or openings (not shown) configured to remain patent in vivo are also contemplated in other applications. The inner and/or outer film layers48b,48coptionally lend increased radial, or hoop strength to the base graft18and help to set the maximum diametric expansion limit of the stent-graft12,18at the as manufactured diameter of the stent-graft12,18.

The stent12and the base graft18are secured together to provide a stent-graft12,18. For example, the first segment14is secured to the base graft18and an end of the second segment16is optionally secured to the base graft18and/or first segment14. As shown, one or more layers of the base graft18is positioned interior of the stent12to define the inner lumen26, although the base graft18is optionally positioned entirely outside of the stent element12or with the stent12embedded into the base graft18, for example. As shown, a majority of the second segment16of the stent12is left uncovered, with an end of the second segment16secured to the base graft18(e.g., a single “row”) and a remainder of the second segment16extending from the base graft18. As shown, none of the interstices of the second segment16are covered such that fluid is able to flow through the interstices. In an intrahepatic shunt application, the second segment16is left uncovered to facilitate perfusion of portal venous branches via blood flow through the interstices of the second segment16.

The base graft18is preferably attached to the stent12by bonding or otherwise attaching the two together through use of a suitable adhesive, such as fluorinated ethylene propylene (FEP), polyurethane, cyanoacrylates, or others. Additionally, the materials may be bonded or otherwise attached together through heat treatment (such as, sintering of the materials together) or through use of a wrap (for instance a tube, tape, or membrane) around the outside of the stent and cover (either continuous or discontinuous) that is adhered through either a thermoplastic or thermoset adhesive to the stent and cover. Alternatively, the stent12may also be coated with a thermopolymer or thermoset adhesive and the cover bonded or otherwise attached by reflowing or setting the polymer coating. In still other embodiments, the stent12and base graft18are mechanically attached (e.g., using sutures).

In some methods of making the endoprosthesis10, the stent12is positioned as desired over a portion of the base graft18(e.g., over a base tube and layers of wrapped expanded PTFE) and a porous composite film of FEP and expanded PTFE is wrapped over the construction with the side of the film containing FEP toward the lumen of the base graft18. The first segment14of the stent12is optionally coated with an adhesive, such as FEP, placed around the base tube48aand inner film48b, and is in turn covered by the outer film48c. The assembly can then be heated at one or more points in the assembly process to bond or otherwise attach the various layers together as described in U.S. Pat. No. 6,673,102 to Vonesh et al.

In some embodiments, the controlled expansion element20is configured to be mechanically adjustable under pressure greater than typical biological pressures (e.g., typically circulatory pressures) and any expansion force exerted by the stent12. For example, the controlled expansion element20is optionally mechanically adjustable by causing controlled expansion material forming one or more portions of the element20to yield or plastically deform, by causing reorganization of a fibrillary or other microstructure of such controlled expansion material, by release of fasteners or folds of the element20, or other mechanical adjustment of the controlled expansion element20. The pressure required to mechanically adjust the controlled expansion element20is greater than typical physiologic conditions (e.g., typical maximum blood pressures) such that the controlled expansion element20is able to maintain the adjusted diameter at less than a pressure that would tend to cause the stent-graft12,18to catastrophically fail by exceeding the maximum diametric expansion limit of the stent-graft12. The controlled expansion element20is preferably configured to maintain a diameter to which it is mechanically adjusted without substantial diameter creep or spontaneous diametric expansion over time under typical biological conditions. The controlled expansion element20optionally includes one or more layers and may be formed from a variety of materials, including fluoropolymer materials such as the distensible, expanded PTFE tube described in U.S. Pat. Nos. 3,953,556, 3,962,153, 4,096,227, 4,187,390, and 4,902,423, to Gore or the distensible lattices of U.S. 2013/0204347 to Armstrong, et al.

In some embodiments, the controlled expansion element20is formed of controlled expansion material including a bilayer compressed composite material formed of layers each including unsintered expanded PTFE and a stabilizing layer, such as a continuous layer of FEP. In some embodiments, the unsintered aspect of the expanded PTFE contributes to the expandability of the controlled expansion material. Unsintered expanded PTFE can be manufactured by extrusion followed by concurrent heating and stretching. Sintered expanded PTFE is manufactured by extrusion, concurrent heating and stretching, and sintering (heating to above the PTFE crystalline melting point temperature). Because unsintered expanded PTFE is heated to a lesser extent than sintered expanded PTFE, unsintered expanded PTFE material has greater conformability and greater stretchability than sintered expanded PTFE. The unsintered expanded PTFE has nonbent fibrils that can elongate approximately 40% or more before rupture, for example.

In some methods of manufacture, one or more wraps of the unsintered expanded PTFE/FEP composite material are overlapped to comprise the controlled expansion element20. The FEP bonds together the multiple wraps of unsintered expanded PTFE to create a monolithic sleeve structure, for example, although a variety of configurations are contemplated (e.g., rings, collars, cylinder segments). For example, the controlled expansion element is optionally formed by cutting the unsintered and compressed, or densified, controlled expansion material into strips that are helically wound onto a cylindrical mandrel. One or more layers are formed in one or more passes to form a sleeve. In some embodiments, the material is wound so that the FEP side of the controlled expansion material faces outward. Any number of additional layers (e.g., an attachment or bonding layer) may also be applied over the controlled expansion element20as desired at any point in the process of forming the controlled expansion element20and/or during assembly of the endoprosthesis10. The diameter of the cylindrical mandrel determines the initial inner diameter of the controlled expansion element20.

In some methods, the controlled expansion element20is then heated, while still on the mandrel, to activate the FEP adhesive. The heat causes the FEP to flow, thereby creating a functionally unitary multi-layered sleeve of unsintered expanded PTFE. After cooling, the controlled expansion element20is removed from the mandrel and the ends of the controlled expansion element20are trimmed to create a sleeve of a desired length. The controlled expansion element20also optionally has a substantially continuous and uninterrupted wall characterized by the absence of apertures or holes configured to remain patent in vivo.

In some methods of assembly, the controlled expansion element20is placed onto an underlying portion of the endoprosthesis10, such as the stent12and base graft18(collectively, “stent-graft12,18”), although a variety of configurations are contemplated, including the controlled expansion element20being secured inside of the stent-graft12,18. In some methods of assembly, the pre-assembled stent-graft12,18is pulled through a loading funnel and into a tube with an outer diameter that is smaller than the inner diameter of the controlled expansion element20. The tube containing the stent-graft12,18is placed within the controlled expansion element20and the tube is removed from the stent-graft12,18. Upon emergence from the tube, the stent-graft12,18self-expands to conform to the inner diameter of the controlled expansion element20. As shown inFIG.1, the controlled expansion element20has a length selected to be shorter than the base graft18such that a partial segment of the base graft18corresponding to the middle portion34is covered by the controlled expansion element20.

In some embodiments, the controlled expansion element20is coupled to a portion of the remaining endoprosthesis10mechanically (e.g., by interference fit, friction fit, sutures, or others). In other embodiments, the controlled expansion element20is alternatively or additionally secured to the endoprostheses using a bonding agent (e.g., an adhesive such as FEP) between the endoprosthesis and the controlled expansion element20. The bonding agent is optionally applied as a continuous layer or a discontinuous layer over substantially all the interface between the controlled expansion element20and the remaining endoprosthesis10or over only one or more portions of the interface between the controlled expansion element20and the remaining endoprosthesis10. Though less desirable in controlled expansion elements20in which it is desirable for the material to remain unsintered, in some embodiments the controlled expansion element20is alternatively or additional coupled to the graft by a heating operation (e.g., by a global sintering or localized sintering at one or more selected portions of the interface between the controlled expansion element20and the remaining endoprosthesis10).

In some embodiments, an inner diameter set process is performed for coupling the controlled expansion element20to the stent-graft12,18prior to collapsing the endoprosthesis10into a delivery configuration. Some set processes include pulling the stent-graft12,18with controlled expansion element20placed on it over a mandrel (not shown) having a larger outer diameter than the initial ID of the assembled endoprosthesis10. The mandrel has an outer diameter (OD) corresponding to the shape of the middle portion34and the desired initial diametric expansion limit of the endoprosthesis10(the ID to which the endoprosthesis self-expands to in vivo following deployment prior to mechanically adjusting the controlled expansion element20). For example, in an endoprosthesis adjustable between 8-10 mm, the controlled expansion element20would cause the endoprosthesis10to have an ID less than 8 mm and the OD of the mandrel would be 8 mm such that after the set process the controlled expansion element20is mechanically adjusted and the endoprosthesis10exhibits an 8 mm ID. In some embodiments, the mandrel has flared ends corresponding to the ends of the controlled expansion element20to provide flared ends to the controlled expansion element20and a smoother transition between the segment of the stent-graft12,18constrained by the controlled expansion element20and adjacent segments of the stent graft12,18. Although the mandrel may have a continuous diameter between flared ends, any number of flares, tapers, curves, or other features are contemplated for imparting corresponding features to the portion of the endoprosthesis10corresponding to the controlled expansion element20.

The set process causes the controlled expansion element20to conform to the outer surface of the endoprosthesis10, which is believed to help hold the controlled expansion element20in place through subsequent processing, deployment, and implantation of the endoprosthesis10without the use of thermal and/or adhesive bonding. In some embodiments, the absence of thermal and/or adhesive bonding or other attachment along at least a portion of the interface between the controlled expansion element20and the stent-graft12,18defines a sliding interface that helps allow the controlled expansion element20to slide on the surface of the stent-graft12,18when ballooned, thus limiting the amount of foreshortening the controlled expansion element20translates to the stent-graft12,18. For example, an interference fit between the stent graft12,18and controlled expansion element20provides a sliding interface between the components, according to some embodiments. In different terms, during diametric expansion of the endoprosthesis10, the sliding interface between the controlled expansion element20and the stent-graft12,18permits at least a portion of the controlled expansion element20to change in longitudinal dimension (e.g., contract during radial expansion) at a different rate than the stent-graft12,18at the sliding interface.

In some other embodiments, a portion of the interface between the controlled expansion element20and stent-graft12,18is adhesively bonded. For example, in some embodiments a fluoropolymer adhesive is used, such as tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) described in U.S. Pat. No. 7,462,675 to Chang et al., FEP (fluorinated ethylene propylene), or PFA (perfluoroalkylvinyl ether/tetrafluoroethylene copolymer), for example. The adhesive is optionally applied on the inner diameter of the controlled expansion element20, for example at each end of the controlled expansion element20but not at the central region, although a variety of configurations are contemplated. After the controlled expansion element20is placed on the stent-graft12,18the adhesive is activated by applying heat thereto, for example without causing sintering, or at least without causing significant sintering, of the controlled expansion material20.

In still other embodiments, the controlled expansion element20is adhered along the entire interface or a majority of the interface the controlled expansion element20forms with the remaining endoprosthesis10. For example, in some embodiments including a controlled expansion element having an outer layer of FEP, the controlled expansion element20is everted prior to applying it over the stent-graft12,18. The eversion of the controlled expansion element20repositions the FEP that was previously on the outer diameter (abluminal surface) of the controlled expansion element20to the inner diameter (luminal surface).FIGS.4and5illustrate a distal portion of a delivery system50for delivering and deploying the endoprosthesis10to a desired location for treatment, according to some embodiments. The delivery system50is a catheter-based, multi-staged deployment system including various features such as those described in U.S. Pat. No. 6,673,102 to Vonesh et al. As shown, the delivery system50includes an introducing (or packaging) constraint52, a delivery constraint54, a distal catheter shaft56, and a proximal catheter shaft58(partially shown and extending proximally inFIGS.4and5).FIGS.4and5also show a cut off view of a deployment line60attached to a delivery constraint54having a sufficient length to be externally manipulated to release the delivery constraint54from the endoprosthesis10. During endovascular deployment, the delivery system50is passed through an introducing catheter (not shown) extending to a target location in the body of a patient.

In some embodiments, the introducing constraint52is a tube slidably received over the endoprosthesis and functions to maintain the second segment16of the stent12in a compacted, delivery profile. As described below, the introducing constraint52assists with transferring the endoprosthesis10into an outer catheter tube (e.g., an introducer) with the second segment16maintained in the compacted, delivery profile in the catheter tube (not shown).

For example,FIG.4corresponds to a state in which the endoprosthesis10is fully constrained at a delivery diametrical dimension andFIG.5shows the endoprosthesis10partially deployed, and in particular with the second segment16of the stent12allowed to deploy (e.g., via self-expansion). When the second segment16of the endoprosthesis10is unconstrained, the second segment16will expand to close to its fully deployed diameter. The remainder of the endoprosthesis10, however, is contained within a delivery constraint54at a delivery diametrical dimension. In operation, the constrained endoprosthesis10will pass from the introducing constraint52into a catheter tube of approximately equal inner diameter (not shown) extending past the ultimate deployment site. Deployment of the second segment16will occur when the endoprosthesis10is extended from the catheter tube (not shown) at the deployment site (e.g., by retracting the catheter tube, extending the second segment16from the catheter tube, or a combination thereof).

The delivery constraint54maintains the first segment14, base graft18, and controlled expansion element20in a collapsed state at a delivery diametrical dimension. In some embodiments, the delivery constraint54, also described as a constraining element, comprises a plurality of interwoven threads that are capable of being unwoven upon pulling the deployment line60at which point the delivery constraint54is deconstructed and pulled from the away from the endoprosthesis10through the delivery system50. For example, the deployment line60extends through the proximal shaft58toward a proximal end of the system50where it can be manipulated externally to a patient by a user. Examples of knit, or interwoven delivery constraints are disclosed in U.S. Pat. No. 6,673,102 to Vonesh et al. and U.S. Pat. No. 6,224,627 to Armstrong et al. In other embodiments, the delivery constraint54is a sheet of material having two ends secured together that are able to be released upon actuation of a deployment line. In still other embodiments, the delivery constraint54is a distal end of a catheter sheath that is able to be actuated and removed from the stent-graft12,18to permit self-expansion to the initial deployed state of the stent-graft12,18.

FIG.6shows the endoprosthesis deployed in an intrahepatic portosystemic shunt. Methods of operating the delivery system and deploying the endoprosthesis that follow are made with reference toFIGS.4-6in the contact of an intrahepatic shunt procedure, although a variety of applications are contemplated.

A catheter tube (not shown) is advanced into a portal vein P of a patient though a pathway formed through the liver from the haptic vein H to the portal vein P. A compacted endoprosthesis10, mounted within the introducing constraint52is inserted into a proximal end of the catheter tube by manipulating the proximal shaft58to cause the second segment16to become transferred from the introducing constraint52into the catheter tube. The endoprosthesis10is then advanced through the catheter tube through the inferior vena cava, the hepatic vein H, the intrahepatic tract (shunt) formed in the liver, and well into the portal vein P. Radiopaque tip64can be aligned with the end of the catheter tube. Radiopaque markers associated with the endoprosthesis10, such as the band38(FIG.1) can be used to position the end of the base graft18adjacent to the intrahepatic juncture site Y such that the second segment16extends into the portal vein P. The catheter tube is withdrawn proximally, which permits the second segment16to fully expand within the portal vein P. The proximal catheter shaft58is then withdrawn through the catheter tube to seat the endoprosthesis10so that the unlined portal region is in the portal vein P of the liver and the graft-lined region28is engaged with the ostium of the tunnel in which the endoprosthesis10is being deployed, corresponding to the intrahepatic juncture Y. Alignment can be confirmed fluoroscopically by correct orientation of one or more radiopaque markers. In some embodiments, the endoprosthesis10is optionally deployed into the lumen of a previously deployed endoprosthesis (not shown) forming the shunt to augment or correct the performance of a previously deployed endoprosthesis, for example.

Once the endoprosthesis10is properly aligned, the delivery constraint54is removed by actuating deployment line60, allowing the first segment14of the endoprosthesis10to enlarge in place in a tip-to-hub direction. As is illustrated inFIG.6, the deployment procedure aligns the covered portion of the endoprosthesis10within the intrahepatic tract (shunt). Further, the uncovered second segment16permits blood flow both to enter the endoprosthesis10and to continue through the portal vein P. The result is that excess pressure can be relieved from the portal system (through the shunt formed by the endoprosthesis10) without completely eliminating normal blood flow through portal vein P. The broken lines inFIG.6illustrate the endoprosthesis expanded to the initial diametric expansion limit pre-set into the controlled expansion element20. If desired, touch-up of the endoprosthesis10can be performed by subsequent balloon dilation of the endoprosthesis10at balloon diameters below those required to mechanically adjust the controlled expansion element20to an adjusted diameter.

Some methods of forming an intrahepatic portosystemic shunt include positioning the endoprosthesis10in the liver of the patient at a delivery diametrical dimension. The endoprosthesis10is fully deployed such that the endoprosthesis self-expands in situ and is fully seated in the liver of the patient to form the intrahepatic portosystemic shunt, where the controlled expansion element20limits expansion of a partial segment of the stent-graft12,18to an initial deployed diametrical dimension as shown inFIG.6. This limited expansion restricts fluid flow through the shunt and impacts the pressure gradient between the portal vein P and the systemic venous circulation. The first end portion32(FIG.1) and a second end portion36(FIG.1) help anchor and seal the endoprosthesis10against the anatomy and prevent migration of the endoprosthesis10. If a user (e.g., a clinician) wishes to increase the fluid flow to adjust the pressure gradient, the user can apply a distending force on controlled expansion element20, for example by using a balloon catheter80(FIG.7), to mechanically adjust the controlled expansion element20a desired amount (e.g., up to the maximum diametric expansion limit of the base graft18, which is represented in solid lines inFIG.6).

FIG.8is a schematic illustration of dilation of a portion of the endoprosthesis10using the balloon catheter80. In the schematic illustration, the stent12and base graft18are indicated collectively as a layer. As generally indicated, the entire middle portion34which corresponds to the controlled expansion portion of the endoprosthesis10need not be dilated or otherwise diametrically adjusted in a single step (e.g., where balloon length is less than the middle portion34).

The diameter of the segment of stent-graft12,18corresponding to the controlled expansion element20is able to be adjusted to any diameter between the initial delivery expansion limit and the maximum expansion limit by selection of maximum balloon diameter and/or balloon pressure. In other words, the diameter (e.g., including the minimum inner diameter (ID) at the location46) is able to be selectively enlarged to an enlarged diametrical dimension, also described as an enlarged or adjusted diameter. The controlled expansion element20maintains the endoprosthesis10at the enlarged diametrical dimension and does not permit creep of the ID under typical physiologic conditions. Thus, the controlled expansion element20helps the endoprosthesis10maintain the enlarged diametrical dimension to permit increased fluid flow through the shunt (e.g., up to the maximum diametric expansion limit of the base graft18, which then limits any further expansion).

Various methods of treatment include taking one or more pressure measurements and adjusting the endoprosthesis10according. For example, in an intrahepatic shunt procedure, portal hypertension may be assessed and treated using one or more of such pressure measurements and adjustments. Portal hypertension is an increase in the blood pressure within the portal venous system. Wedged hepatic venous pressure (WHVP), is used to estimate the portal venous pressure by reflecting not the actual hepatic portal vein pressure but the hepatic sinusoidal pressure. The hepatic venous pressure gradient (HVPG) is a clinical measurement of the pressure gradient between the WHVP and the free hepatic venous pressures, and thus is an estimate of the pressure gradient between the portal vein and the inferior vena cava.

In some embodiments, a user takes at least one pressure measurement after fully deploying the endoprosthesis to determine the pressure gradient between the portal vein and the systemic venous circulation, determines that adjustment is needed, and adjusts the diameter of the partial segment of the base graft18corresponding to the controlled expansion element20. Any number of subsequent pressure measurements and enlarging adjustments are contemplated as part of a single procedure or multiple procedures. For example, in some treatment methods at least 24 hours pass between one or more pressure measurements and/or adjustments of the endoprosthesis10, or an even greater amount of time. For example, it is contemplated that a diametric adjustment may occur as a separate procedure from the initial delivery procedure and formation of the shunt or as a separate adjustment procedure subsequent to a prior diametric adjustment procedure (e.g., performed at a later day, month, or even year).

In addition to, or as an alternative to being formed of controlled expansion material, the controlled expansion element20optionally includes one or more physical features, such as pleats, folds, or creases (FIG.8) that are selectively secured in a closed configuration (e.g., by a bonding agent or material) and which can later be opened or separated by application of a distending force, thereby allowing the features to expand to mechanically adjust the diameter of the controlled expansion element20. For exampleFIG.9shows a controlled expansion element120usable with any of the various features described above in association with endoprosthesis10. The controlled expansion element120is generally sleeve-like, or cylindrical in configuration, is mechanically adjustable at distending forces greater than typical physiologic conditions (e.g., blood pressure), and can correspond to the diametrically controlled portion of the endoprosthesis10, which is not shown inFIG.8. As indicated inFIG.8, the controlled expansion element120includes one or more layers forming a sleeve122that defines one or more expansion features124in the form of longitudinal pleats or folds. One or more securing elements126, for example a tape material, such as ePTFE coated with FEP, secures the expansion features124in a closed state. Upon application of a distending force (e.g., balloon dilation), the securing elements126allow the expansion features124to expand (e.g., they plastically deform, break, or release) resulting in diametric adjustment of the diametrically controlled portion of the endoprosthesis10.

Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.