Patent Application
20180185178
The disclosure relates to implantable medical devices, such as segmented stent grafts having bifurcated segments and fenestration assemblies, and the like, and, more particularly, to implantable medical devices that include magnet arrays configured to manipulate the articulation of the stent segments.
Implantable medical devices are known in many forms and for treating many medical conditions. Examples include stents, grafts, filters, occluders, valve replacement prostheses and so on. Such devices are generally introduced into the patient endoluminally through a remote percutaneous entry point. In order to achieve this, the medical device is loaded onto a carrier at a distal end of an introducer assembly with the device being held in a radially compressed configuration. The introducer assembly is fed into the patient's vasculature from the percutaneous entry point until its distal end is located at the treatment site. Once so positioned, the medical device is released from the carrier and expanded until the device engages the vessel wall to be held thereby. The device can be of a type which expands automatically, achieved by use of a spring material, shape memory material and so on. Other types of device are plastically deformable and expanded by a separate mechanism, for instance by inflation of a delivery balloon on which the device is held in crimped form.
Stent grafts are used for treatment of vasculature in the human or animal body to bypass a repair or defect in the vasculature. For instance, a stent graft may be used to span an abdominal aortic aneurism. In many cases, however, such damaged or defected portion of the vasculature may include a branch vessel, such as a mesenteric artery or a renal artery. Bypassing such an artery without providing blood flow into the branch artery can cause problems and hence fenestration assemblies are provide in the wall of a stent graft which, when the stent graft is deployed, is positioned over the opening to the branch vessel. Another stent graft can be deployed through the fenestration into the branch vessel to provide a blood flow path to the branch artery.
Typically the stent grafts must be custom made to conform to the unique branching vasculature of the patient. Custom made devices require a long lead time and extreme precision in the design and fabrication of the device. Further, such custom manufacturing requires considerable to time from the first stages of device manufacturer to delivery to the physician/patient. Accordingly, a need existed for an implantable medical device in which the configuration of the device can be customized to a particular patient more rapidly than is now allowed by current methods.
The present disclosure provides an implantable medical device that incorporates magnetic elements, such that the device has the ability to be readily adapted a patient's anatomic configuration.
In accordance with an embodiment of the disclosed subject matter, an implantable medical device includes a first section and a second section, and an interface region between the first and second sections. A magnet array overlies each of opposing surfaces of each of the first and second sections at least at the interface region. The magnet arrays include a plurality of magnetic elements arranged in a predetermined pattern, each of the plurality of magnetic elements having a north and a south pole. The predetermined pattern is such that the north and south poles of the magnetic elements in each magnetic arrays are conjugated with one another so as to define a variable magnetic field between the first and second sections.
In accordance with another embodiment of the disclosed subject matter, a stent graft includes a first section and a second section. The second section has a preferred rotational position with respect to the first section. An interface region resides between the first and second sections. A magnet array overlies each of opposing surfaces of each of the first and second sections at least at the interface region. The magnet arrays include a plurality of magnetic elements arranged in a predetermined pattern, each of the plurality of magnetic elements having a north and a south pole. The predetermined pattern is such that the north and south poles of the magnetic elements in each of the magnetic arrays are conjugated with one another so as to define a variable magnetic field between the first and second sections. The magnetic field is such that the second section assumes the preferred rotational position with respect to the first section upon contact of the first and second sections.
The zig-zag stents are also well known as Gianturco Z-stents commercially available from William A Cook Australia Pty Ltd, Brisbane, Australia or Cook Inc, Bloomington, Ind., USA. The graft material is typically DACRON™ material available from a number of medical graft manufacturers.
The zig zag stent within the proximal end 16 of the first graft portion 2 assists with sealing of the graft against the walls of the aorta and the external zig zag stents provide a smooth inner surface for the flow of blood through the graft. The internal zig zag stent section 14 at the distal end section 12 provides an outer surface of the tubular body 8, which is smooth and can seal within the proximal end of the second graft portion 4 when it is deployed within the second graft portion 4.
The second graft portion 4 comprises a fabric material graft body 26 and has an internal zig zag stent 22 at its proximal end 24 so that the outer surface of its tubular body 26 is smooth and can seal within the distal end of the first graft portion 2 when it is deployed within the first graft portion 2. The external zig zag stents 25 provide a smooth inner surface for the flow of blood through the graft. The second graft portion 4 is bifurcated and has a leg graft portion 6.
Towards the distal end of the second graft portion 4 the tubular body 26 bifurcates into a longer leg section 28 and a shorter leg 30 each of which has a zig zag stent section 29 on its outside surface except the terminal zig zag stent section 32 on the longer leg.
The leg graft portion 6 which is adapted to extend into the contralateral-iliac artery is comprised from a tubular fabric material body 34 with outside zig zag stents 36 along its length except for internal zig zag stents 38 at its proximal and distal ends. Those skilled in the art will appreciate that the bifurcated graft segment has a preferred orientation with respect to the first segment, depending upon the particular tortuosity of the patient's vasculature.
As will subsequently be described in more detail, in one embodiment, magnet arrays 40 and 42 overlie opposing surfaces at the distal end 12 of the first graft portion 2 and at the proximal end 24 of the distal graft portion 4. Further, magnet arrays 44 and 46 overlie opposing surfaces at the distal end the shorter leg 30 and at the proximal end 37 of leg graft portion 6.
Those skilled in the art will appreciate that, in addition to the examples illustrated in the composite stent graft of
The graft in
The principal of operation of the magnet arrays will now be described in connection with schematic representation of graft segments.
The arrangement described above is only one of number of different polarity patterns that can be employed depending upon the particular application. Also, the magnetic elements can be arranged such that the segments will align with each other in a preferred orientation. For example, the number of magnetic elements having opposing polarity in each of the rows in magnet arrays 40 and 42 can be varied, such that when graft portions 2 and 4 are deployed by placing distal graft portion 4 in the aorta with proximal end 24 of the distal graft portion 4 inside distal end 12 of graft portion 2, graft portion 4 can assume a preferred rotational orientation with respect to graft portion 2. Accordingly, the magnetic field strength between the magnet arrays can be determined by the particular arrangement of the relative position of the magnetic elements in the magnet arrays.
Further, in accordance with another embodiment, the magnetic strength of the magnetic elements can vary between one another. By varying the relative magnetic strength among the magnetic elements, the strength of the magnetic field between the magnet arrays can be specifically designed to have a particular contour, such that a controlled degree of flexibility between the segments of the stent graft is attained. Those skilled in the art will appreciate that a variation in the magnetic field strength can provide stress compensation between the segments of the stent graft that will accommodate the natural motion of the patient's body and any on-going geometric changes that increase vessel tortuosity.
In yet another embodiment, the arrays illustrated in
The inner ring 80 can move angularly with respect to the outer ring 78 so as to allow for misalignment of the fenestration with the branch vessel when the stent graft 72 is positioned within a body lumen.
It will be noted, that the open aperture in the smaller ring is directed towards one end of the stent graft. This can be varied to face towards one end or the other of the stent graft depending upon what direction the physician is intending to approach the fenestration. For instance in deployment into the aorta a physician may use either a brachial or a femoral approach.
Those skilled in the art will recognize that the fenestrated stent graft illustrated in
Those skilled in the art will recognize that numerous different vascular branching structures exist. For example, T-branch stent grafts are known in the art with up to four external branches in a downward (caudal) pointing direction. A stent graft incorporating the disclosed magnet arrays can better angulate to accommodate challenging anatomies and widen the scope of use (inclusion/IFU criteria). The magnetically connected branches being more flexible to optimize the alignment with the branch vessel and allow a larger alignment margin for placement of the device. Further, migration or movement of the T-branch stent graft would not immediately compromise the branches either due to the ability of the magnetically attached branches to accommodate movement and continue to facilitate optimal flow to the branch vessels.
In the left hand side of
As can be seen on the left hand side of the drawing, the fenestration assembly has its inner ring 80 and hence its opening facing slightly towards the distal end 104 of the stent graft so that when a physician is attempting to deploy a guide wire from the aorta into the side branch through the stent graft 72 it will be somewhat easier to guide the guide wire through the aperture in the fenestration assembly 74.
A bridging stent graft 106 is deployed in the right hand fenestration assembly 74. After the bridging stent graft 106 has been deployed, the inner ring 80 of the fenestration assembly is engaged around the outside of the bridging stent graft 106 and the inner ring 80 has hinged to a more vertical position which means that the graft material 82 joining the inner ring 80 and the outer ring 76 of the fenestration assembly 74 is now not taut but in this condition still provides a leak proof seal for the fenestration.
The resilient inner ring provides a good sealing and retention surface for the proximal end of the bridging stent graft 106. The bridging stent graft 106 may have stents of a balloon expandable or of a self-expanding type. The bridging stent graft 106 includes a number of self-expanding zig zag or Z stents 108 of the well-known Gianturco type.
In accordance with an exemplary embodiment, arrays of magnetic elements are included in an interface region 110 between abutting portions of stent graft 72 and bridging stent graft 106. A magnet arrays overlie both the periphery of fenestration 92 and the circumferential end of bridging stent graft 106 in interface region 110. A schematic diagram of fenestration assembly 74 is illustrated in
A magnet array 112 overlies an end surface 114 of bridging stent graft 106. A magnet array 116 overlies the periphery of fenestration 92 in stent graft 72. The magnetic elements in each array are conjugated so as to provide a magnetic field at the interface region 110. An exemplary embodiment of magnet arrays 112 and 116 is illustrated in
While the p-branch devices such as that schematically illustrated in
Another embodiment of the magnet arrays of
The arrays of magnetic elements can be incorporated into the walls of the stent graft segments in a number of different configurations. For example, the magnetic elements can be incorporated into a polymer cover material. A number of different biocompatible graft materials can be used to cover the stents. Examples of graft materials include polyesters, such as Dacron™ (polyethylene teraphthalate or PET), fluorinated polymers, such as PTFE (polytetrafluoroethylene) and Teflon™ (expanded polytetrafluoroethylene or ePTFE); polyurethanes such as THORALON™; polyamides such as nylon; or any other suitable material such as coliagenous extracellular matrix (ECM) material including small intestine submucosa (SIS), which is commercially available from Cook Biotech, West Lafayette, Ind., U.S.A. Besides SIS, examples of ECM's include pericardium, stomach submucosa, liver basement membrane, urinary bladder submucosa, tissue mucosa, and dura mater.
Graft materials may include sheets containing a biocompatible polymer. Examples of biocompatible polymers from which sheets can be formed include polyesters, such as polyethylene terephthalate, polylactide, polyglycolide and copolymers thereof; fluorinated polymers, such as polytetrafluoroethylene (PTFE), expanded PTFE and poly(vinylidene fluoride); polysiloxanes, including polydimethyl siloxane; and polyurethanes, including polyetherurethanes, polyurethane ureas, polyetherurethane ureas, polyurethanes containing carbonate linkages and polyurethanes containing siloxane segments. In addition, materials that are not inherently biocompatible may be subjected to surface modifications in order to render the materials biocompatible. The graft material may include a biocompatible polyurethane.
A variety of other biocompatible polyurethanes/polycarbamates and urea linkages (hereinafter “CON type polymers”) may also be employed. These include CON type polymers that preferably include a soft segment and a hard segment. The segments can be combined as copolymers or as blends. For example, CON type polymers with soft segments such as PTMO, polyethylene oxide, polypropylene oxide, polycarbonate, polyolefin, polysiloxane (i.e. polydimethylsiloxane), and other polyether soft segments made from higher homologous series of diols may be used. Mixtures of any of the soft segments may also be used. The soft segments also may have either alcohol end groups or amine end groups. The molecular weight of the soft segments may vary from about 500 to about 5,000 g/mole.
Other applicable biocompatible polyurethanes include those using a polyol as a component of the hard segment. Polyols may be aliphatic, aromatic, cycloaliphatic or may contain a mixture of aliphatic and aromatic moieties. For example, the polyol may be ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, propylene glycols, 2,3-butylene glycol, dipropylene glycol, dibutylene glycol, glycerol, or mixtures thereof. Biocompatible CON type polymers modified with cationic, anionic and aliphatic side chains may also be used. See, for example, U.S. Pat. No. 5,017,664. Other biocompatible CON type polymers include: segmented polyurethanes, such as BIOSPAN; polycarbonate urethanes, such as BIONATE; and polyetherurethanes, such as ELASTHANE; (all available from POLYMER TECHNOLOGY GROUP, Berkeley, Calif.). Other biocompatible CON type polymers can include polyurethanes having siloxane segments, also referred to as a siloxane-polyurethane.
Graft materials also may be woven (including knitted) textiles or nonwoven textiles. Nonwoven textiles are fibrous webs that are held together through bonding of the individual fibers or filaments. The bonding can be accomplished through thermal or chemical treatments or through mechanically entangling the fibers or filaments. Because nonwovens are not subjected to weaving or knitting, the fibers can be used in a crude form without being converted into a yarn structure. Woven textiles are fibrous webs that have been formed by knitting or weaving. The woven textile structure may be any kind of weave including, for example, a plain weave, a herringbone weave, a satin weave, or a basket weave. A textile material contains fibers and interstices between the fibers.
The graft material may be a reconstituted or naturally-derived collagenous material. Such materials that are at least bioresorbable will provide advantage in the present invention, with materials that are bioremodelable and promote cellular invasion and ingrowth providing particular advantage. Suitable bioremodelable materials can be provided by collagenous extracellular matrix materials (ECMs) possessing biotropic properties, including in certain forms angiogenic collagenous extracellular matrix materials. For example, suitable collagenous materials include ECMs such as submucosa, renal capsule membrane, dermal collagen, dura mater, pericardium, fascia lata, serosa, peritoneum or basement membrane layers, including liver basement membrane. Suitable submucosa materials for these purposes include, for instance, intestinal submucosa, including small intestinal submucosa, stomach submucosa, urinary bladder submucosa, and uterine submucosa.
Preferably, the magnetic elements are laminated into, bonded with, or attached to a polymer material or a graft material. In one example, a magnetic pattern is printed on a ferromagnetic material. Methods for producing an array of magnetic elements or a wire including the magnetic elements are known in the art. See for example, U.S. Pat. No. 7,800,471, which is incorporated by reference herein. The polarity of the magnets, the magnetic strength, and the pattern of magnets in the ferromagnetic material can be computer programmed to produce a desired pattern in the ferromagnetic material. The ferromagnetic material can then be assembled with one of more of the graft materials described above. Further, the ferromagnetic material can be formed as a wire and the wire integrated with or attached to the graft material.
In accordance with the disclosed subject matter the magnet arrays can be attached to stent graft segments in a variety of attachment configurations. For example, the magnet array can be laminated between layers of a polymer film. Alternatively, the magnet arrays can be directly bonded to the graft material. In yet another configuration, the magnet arrays can be fabricated in the form of ferromagnetic wires and bonded or sutured to the graft material. Still further, the magnet arrays can be contained within material pouches, formed a polymer film or from grant material, and bonded or sutured to the stent graft segments.
By providing graft segments having magnet arrays or wires containing magnetic elements, as described above, standardized stent graft segments can be supplied and the particular geometric aspects of the articulated stent segments determined by specifically programmed magnet arrays that are appropriately positioned in the stent segments. The arrays are programmed to cause the graft segments to articulate in such a way as to correspond to the vascular tortuosity of a particular patient. This technique reduces the manufacturing time to produce a graft section, as compared with the time required to manufacture customized graft segments.
Those skilled in the art will recognize that the magnet arrays and graft segments schematically illustrated in
Thus, is apparent that there has been described an implantable medical device including magnetic elements that fully provides the advantages set forth above. Those skilled in the art will recognize that numerous modifications and variations can be made without departing from the spirit of the invention. For example, the magnet arrays can be arranged in a stent graft so as to hold open the stent segment, or alternatively, to unfold a stent segment before or during delivery. Accordingly, all such variations and modifications are within the scope of the appended claims and equivalents thereof.
