Patent Description:
Implant materials that facilitate tissue ingrowth, such as grafts, may be used in the medical arts, particularly in applications involving vascular replacement, augmentation, and/or repair. These materials may be naturally-derived or non-naturally-derived, and when they are implanted within a patient, cells and other bodily substances from the patient can infiltrate the material, leading to, for example, new tissue growth on, around, and/or within the implanted material. Tissue ingrowth may enhance the biocompatibility of such implants, but excessive tissue growth may result in unwanted complications.

Such grafts and graft anchoring devices may be used in implantable Ventricular Assist Devices (VAD) to create inflow and outflow conduits that interface with the circulatory system. Control of cellular ingrowth has been one of the main challenges for such devices when implanted for long periods of time.

<CIT> discloses an endoprosthesis including a stent structure having an elongate member longitudinal portions of which overlap to define the crossover structures.

<CIT> discloses an endoluminal prosthesis having a tubular graft comprising a first biocompatible material having a first weave density comprising yarns aligned in a first direction interwoven with yarns aligned in a second direction, and a second biocompatible material having a second weave density less than the first weave density comprising yarns aligned in a first direction interwoven with yarns aligned in a second direction, the second biocompatible material spirally positioned throughout the entire length of the tubular graft around a central axis with respect to the first biocompatible material. <CIT> discloses a system, apparatus, and method for treating, repairing, and/or replacing an aneurysm.

According to the invention, a vascular graft comprising the features of claim <NUM> is provided. The present disclosure provides, in certain aspects, unique methods and systems for anchoring graft materials to the walls of bodily structures. Some methods and systems involve anchoring a first graft component to a wall of a bodily structure, wherein new tissue growth on, around, and/or within the first graft is facilitated. The first graft component is intended to provide a cuff structure to allow the anchoring of a second graft component easily. The second graft and first graft component may have the same or substantially similar material, biological characteristics, mechanical characteristics, and/or dimensions. Alternatively, the second graft component may have distinct material, biological characteristics, mechanical characteristics, and/or dimensions from the first graft component. The graft could be formed of two or more similar or different components.

In another embodiment, the disclosure provides a graft formed by components that have different characteristics that could be joined together to give different characteristics to different parts of the graft.

In another embodiment, the disclosure provides techniques to limit cellular ingrowth to the proximal component of the graft but not to other components; therefore cellular propagation is limited to one or more components but not to all components.

In another embodiment, the disclosure provides techniques used to have different diameter grafts joined in such a way that a vortex could be formed in sections of the graft to enhance "washout" effect in certain sections of the graft and therefore limit any cellular growth or attachment in such sections of the graft.

In another embodiment, the disclosure provides techniques used to have a single graft that is equipped by internal deformity to intentionally create a vortex in the flow in order to disrupt any cellular buildup in such area.

In another embodiment, the disclosure provides techniques used to have a single graft having different internal structure or characteristics in different regions to enhance certain reaction or behavior in certain regions while other sections inhibit certain reactions and behaviors.

In one embodiment a vascular graft is provided. The vascular graft includes at least one conduit having a first conduit region and a second conduit region. The vascular graft further includes at least one perturbation formed in the conduit in the second conduit region, the perturbation configured to cause a vortex in the second conduit region.

The first conduit region may include a first material and the second conduit region may include a second material distinct from the first material. The first material may include silicone rubber. The second material may include porous ePTFE. The second material may include woven Dacron®.

The at least one perturbation may decrease the inner diameter of the conduit region. The at least one perturbation may be tapered.

The first conduit region and the second conduit region may have substantially the same diameter.

The vascular graft may include a blood flow assist system coupled to the at least one conduit.

Another embodiment provides a vascular graft that includes at least one conduit having a first conduit region and a second conduit region. The second conduit region includes a bulbous portion with respect to the first conduit region. The graft further includes at least one first support strut positioned in the first conduit region. The at least one first support strut is formed in a spiral configuration. The graft further includes at least one second support strut position in the second conduit region.

The at least one second support strut may be sutured to an outer wall of the bulbous portion of the second conduit region.

The at least one second support strut may be composed of stainless steel wires.

The system may include a blood flow assist system coupled to the at least one conduit.

The skilled artisan will understand that the drawings are primarily for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawing, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

The features and advantages of the inventive concepts disclosed herein will become more apparent from the detailed description set forth below when taken in conjunction with the drawings.

Following below are more detailed descriptions of various concepts related to, and exemplary embodiments of, inventive devices as well as systems, and methods for providing a graft anchor.

While the present disclosure may be embodied in many different forms, for the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications in the described embodiments and any further applications of the principles of the present disclosure as described herein are contemplated as would normally occur to one skilled in the art to which the disclosure relates.

The present disclosure provides, in certain aspects, a vascular graft <NUM> that comprises a first component <NUM> equipped with a suturing cuff <NUM> and a second component <NUM> equipped with another suturing cuff <NUM>. First component <NUM> could be attached to a vessel <NUM> using commonly practiced suturing techniques or any other mechanical or non mechanical anastomotic method. In some embodiments, first component <NUM> is made from a material that enhances cellular ingrowth in order to enhance graft biocompatibility. As such the material may by example be a porous EPTFE or a woven Dacron material.

The second component <NUM> may be smaller in diameter and equipped with a suturing cuff <NUM> to allow easy joining of first component <NUM> and second component <NUM> by means of commonly used sutures or any other mechanical or non-mechanical anastomotic methods.

The distal tip of the second component <NUM> typically protrudes inside the first component <NUM> and is somewhat concentric forming a gutter type circular annulus in between component <NUM> and component <NUM>. Blood cells may deposit in this gutter and will as intended define the transition/boundary/seam between the cell ingrown to the smooth non cell ingrown area. In addition, second component <NUM> is made out of material that within the inner lumen inhibits cellular ingrowth or attachment, e.g. by a smooth and thin Silicone layer; therefore cellular ingrowth will be limited to first component <NUM>. To further promote uninterrupted ingrowth defined by a smooth and thin layer of cells growing from the vessel into the first component <NUM>, the first component <NUM> has been designed by its stiffness and potentially bellowed structure to serve as a shock absorbing agent for any blood pumping device, which may be attached to component <NUM>. The shock absorbing agent manages to absorb any flow/pressure induced axial movement and as such helps to facilitate uninterrupted cell ingrowth in the preferred region. As such motion induced by the pumping device will not disturb the ingrowth, which may lead to continuous cell overgrowth, narrowing of the orifice and to irregular granular tissue, which also could dislodge and create ischemic events. While ingrowth into first component <NUM> is wanted, ingrowth onto the outside surface of first component <NUM> has to be avoided by cell inhibiting surface agents e.g. Silicone coating, since an overgrowth onto the outside of first component <NUM> could otherwise lead to target vessel deformation, which inherently may limit the orifice of the vessel near the anastomosis.

Due to the difference in lumen diameter between first component <NUM> and second component <NUM> a vortex is typically formed at vortex area <NUM> located in the proximity of the junction area of first component <NUM> and second component <NUM>. Vortex area <NUM> serves as an area to limit the continual ingrowth or cellular attachment at vortex area <NUM>.

In a different embodiment, the present disclosure provides, in certain aspects, a vascular graft <NUM> that is formed from a single or multiple tubular components that have similar inner diameter. Internal deformity <NUM> could be integral or added at a later stage of the graft manufacturing to form a "neck down" area in the inner lumen of graft <NUM>. Inner deformity <NUM> serves as a bump to create a vortex in its proximity to inhibit cellular ingrowths, cellular attachment, and/or cellular deposit. The two sections of graft <NUM> separated by inner deformity <NUM> could be similar or different in biological characteristics, mechanical characteristics, and/or physical reaction to blood contact. While the area of graft <NUM> distal to internal deformity <NUM> may be surface treated to inhibit cellular ingrowth, the proximal area is designed to promote cellular ingrowth from the vessel onto the graft.

In a different embodiment, the present disclosure provides, in certain aspects, a vascular graft <NUM> that is formed by one or multiple zones, for example first zone <NUM> and a second zone <NUM>, that make a single graft that possesses different biological characteristics, mechanical characteristics, and/or physical reaction to blood contact. In one embodiment zone <NUM> is infiltrated with Silicone rubber to inhibit cellular ingrowth, while zone <NUM> is of a porous/rough nature promoting ingrowth. The mating line between zone <NUM> and <NUM> is without a physical step, which avoids any unwanted overgrowth of cells from zone <NUM> onto zone <NUM>.

<FIG> illustrates a support stent for a conduit, e.g., for use as a graft with a counterpulsation device (CPD). The conduit includes end ports and a passage there between that includes an enlarged area, e.g., bulb shaped portion. In some embodiments, e.g., when used with a CPD, blood may flow through the conduit in alternating direction. The conduit <NUM> includes a spiral support structure <NUM> on a first conduit region. Conduit <NUM> includes a bulbous portion <NUM> having a plurality of support structure <NUM> coupled thereto. Support structures <NUM> and <NUM> may be composed of stainless steel wire and may be coupled to the conduit via sutures in accordance with exemplary embodiments. The bulbous portion <NUM> may be flexible inwardly and outwardly to permit washing of the transition region. The bulbous portion <NUM> may be fabricated using a graft, such as a <NUM> graft, that is cut and sewn into the bulb shape illustrated in <FIG>.

The conduit may be supported by a stent structure. In some embodiments, the support structure includes a first portion that includes one or more support struts shaped to form the bulb portion. In some embodiments, the outer surface of the material of the bulb portion of the conduit (e.g., PTFE or other suitable material), may be attached to the struts. In some embodiments, during use, this arrangement allows the bulb portion of the conduit to flex, e.g., to promote washing of the conduit passage.

In some embodiments, the support stent may include a second portion that supports a non-bulb shaped portion of the conduit (e.g., a portion with a substantially constant cross section). In some embodiments, the second portion may include a spiral shaped support structure. In some embodiments, the struts of the first portion of the support structure may be connected to the second portion of the support structure.

The support stent may be made of any suitable material (e.g., a biocompatible material with sufficient structural properties to support the conduit), including e.g., stainless steel or a shape memory material such as Nitinol.

In some embodiments, the conduit may be formed by one or multiple zones, for example first zone and a second zone, that make a single graft that possesses different biological characteristics, mechanical characteristics, and/or physical reaction to blood contact.

In one embodiment the first zone is infiltrated with Silicone rubber to inhibit cellular ingrowth, while the second zone is of a porous/rough nature promoting ingrowth. The mating line between zones may be without a physical step, which avoids any unwanted overgrowth of cells from the first zone to the second zone. Other embodiments may feature other transition shapes.

In some embodiments, the first zone may correspond to the bulb shaped portion while the second zone corresponds to the other portion, or vice versa.

One form of a counterpulsation system usable with inventive embodiments disclosed herein is shown in <FIG>. Here a pump <NUM> is implanted in a pacemaker pocket on the patient's right side. Blood fills the pump <NUM> on one side and air or other fluid fills a sac or bladder (not shown) on the other side of the pump <NUM>. An air drive line <NUM> is tunneled from the pacemaker pocket to a skin exit site <NUM>, so the entire pump <NUM> is under the skin and can remain there chronically. After the driveline <NUM> exits the skin. It is attached to a small air drive unit <NUM> that controls shuttling of pressurized air in and out of the pump <NUM>. A void in the pump <NUM> may be formed with the sac or bladder. The void fills with air as the heart beats (less cardiac work in ejecting blood) and empties to return blood into the circulation (more flow to the patient). The pump <NUM> is attached to the circulation with a conduit <NUM>. The conduit <NUM> shuttles blood between the patient's circulatory system and the pump <NUM>. This situation allows a patient to have chronic counterpulsation with full mobility. For a patient with severe and potentially non-reversible cardiac dysfunction, this is a great advantage as it is possible to live a relatively normal life, apart from the need to carry a small battery powered drive console <NUM>.

As described, the blood is shuttled in and out of the pump <NUM> with a conduit <NUM>, which is connected, to the circulation. There are a number of considerations related to implantation and use of this conduit <NUM>. First, almost every conduit has blood flowing in one direction, but this conduit <NUM> has blood alternating flow direction two times for each heart beat as the pump <NUM> fills and empties with each cardiac cycle. This creates a number of important issues, which will be described. A second potential difficulty with a conduit in this situation is that it will typically be sewn to the subclavian arte ly <NUM> or axillary artery which is located beneath the clavicle and often quite deep, so it is technically difficult for a surgeon to suture the end of the conduit <NUM> to the artery <NUM>.

The problem of a conduit with bidirectional flow relates to the responses of blood and tissues to the interfaces with synthetic materials and the response is dependent on the direction of blood flow. Many medical devices, such as blood pumps, are connected to the patient's circulation with artificial graft material such as polyester materials like Dacron(R) or expanded, porous Teflon(R) (ePTFE) that will promote tissue or ceil ingrowth. The inside of blood pumps is generally smooth and composed of metals or plastics. When blood flows from a smooth metal or plastic blood pump into a synthetic graft (such as polyester), the interface where the pump meets the conduit (plastic or metal to synthetic graft) is a stable junction and there tends to be little problem when blood flows forward through this junction.

Unfortunately, experience has shown that when blood instead flows from a synthetic graft such as polyester into a smooth surfaced blood pump, a deposit of blood elements including platelets and fibrin tends to deposit at the junction of the two materials-principally on the synthetic graft and overhanging the Inflow to the pump. These deposits, especially platelets, tend to attract more blood elements and large and often fragile deposits occur at this junction. These deposits can break tree from the junction and enter the blood pump and be sent through the patient's circulation. These deposits can flow anywhere, but if they arrive in an artery to the brain, a stroke can result. For this reason, many successful blood pumps employ a smooth synthetic conduit (such as silicone or urethane) for blood inflow into the pump.

The problem with counterpulsation is that blood is flowing in an alternating bi- directional manner. One solution would be to use a smooth silicone or urethane conduit, which would create a stable junction between the pump and the conduit where the blood enters into the pump. This solves the problem at the Inflow to the pump. However, when a silicone material is anastomosed (sewn) to an artery, the junction develops a heavy deposit of blood material (fibrin and platelets). So merely replacing the inflow conduit with a silicone surface is not satisfactory, it Is tempting to merely have a silicone conduit and add a fabric extension, but this merely moves the problem that occurs at the junction of the rough textured surface of the graft and the pump to the junction between the graft and the silicone tube or cannula.

<FIG> shows one exemplary solution in a cross-sectional view. The subclavian artery <NUM> is shown at the top of the figure. A "bubble" or enlarged area <NUM> of Dacron®, Teflon® or other material is sewn to the artery <NUM>. A silicone or other smooth material conduit portion <NUM> is connected to the other side of the enlarged area <NUM>. Rather than a direct junction, a special Interface is created. The smooth silicone surface portion <NUM> extends with a tip portion 26a several millimeters inside the enlarged area <NUM> of fabric or other material. The walls of the silicone tip portion 26a do not contact the fabric or material of the enlarged area or bubble <NUM>, this avoids a silicone-to-fabric (or smooth-to-rough) point of contact.

Heart valves have been constructed with arrangements to avoid tissue ingrowth into the valve by creating an elevation - so that there is not a continuous connection between the fabric surface and the smooth surface. This elevation prevents tissue from growing over into junction point and creating a point where platelets and fibrin are deposited. The use of a small washer of material may also be of use. <FIG> shows a small washer <NUM> around the base of the tip 26a that may help arrest the attachment of blood elements.

<FIG> shows that this arrangement of the "bubble" or enlarged area 24a of graft material is located away from the anastomosis. Specifically, enlarged area 24a is coupled to or includes an extension 24b that is anastomosed to the artery <NUM>. Other features may be as described previously.

<FIG> show a similar arrangement can be made at the junction of the pump <NUM>. Here, the plastic, metal or other smooth surfaced junction or tip portion 10a of the pump <NUM> is separated from the rough surface of the enlarged graft material by a bubble interface 24a. An extension 24b of the graft material is sewn on the artery <NUM> (<FIG>) as previously described. Another extension 24c on the opposite end may facilitate connection to the pump interface or tip portion 1Oa, along with a suitable connector <NUM>. The junction or Interface 10a, which serves as an inlet/outlet port that extends into, but does normally not contact, the graft material 24a in use.

These devices with bubbles or enlargements could be made in one piece. As described previously, the subclavian artery <NUM> is located fairly deep and the incision is small. So a surgeon who is trying to sew a graft with a bubble or enlargement on it is working in a deep hole. The bubble or enlargement on the end of a graft obscures his view of the artery. It would be useful to avoid this problem and also satisfy the need for maintaining the arrangement where the smooth and rough surfaces are not in direct linear contact.

Such a solution is shown in <FIG>. Here, a graft element form from material such as described above is sewn to the artery. The graft element <NUM> has a flange <NUM> at one end. The element <NUM> is small and easy to move around, so does not obscure the view of the surgeon. <FIG> shows that it is easy to sew this element <NUM> around an opening 22a on the artery <NUM>.

<FIG> shows how a junction between the silicone material portion <NUM> of the conduit <NUM> and the graft element <NUM> is recreated when a rim or flange <NUM> of sewing material or graft material, for example, of the conduit portion <NUM> is affixed to the flange <NUM> on the element <NUM> previously anastomosed to the artery <NUM>.

<FIG> shows how the two flanges <NUM>, <NUM> are sewn together. This is a very easy anastomosis to perform.

It will be appreciated that these flanges <NUM>, <NUM> could be joined not just by sutures but by staples, clips, glues, clamps etc..

<FIG> shows a side cross sectional view of the two flanges <NUM>, <NUM> coming together.

<FIG> shows how the bubble or enlarged connector <NUM> does not have to be flat - it could be beveled. Also the connector <NUM> does not have to be a generally spherical bubble as shown elsewhere herein. The key is only that the enlarged area keeps the silicone and graft surfaces (that is, smooth and rough flow surfaces) from direct contact at their junction during use.

The bubble or enlarged area <NUM> is quite useful as it allows the graft to move or "swivel" inside the bubble <NUM> and still not contact the wall of the bubble <NUM>.

<FIG> also shows clips or staples <NUM> attaching the connector <NUM> to the artery <NUM> and attaching the flanges <NUM>, <NUM> together.

The conduit portion <NUM> does not have to be entirely silicone. It could have any Inner core that presents a compatible surface to the exposed blood. For example, the inside could be metal, have a metal spiral reinforcement, etc. it could also have graft material inside like ePTFE or other polyester.

The smooth surface does not have to be silicone. This is used as representative of a smooth surface. The surface could be a metal or plastic (such as in the pump connection shown in <FIG>.

<FIG> shows a bubble or enlarged area <NUM> constructed by "splitting" the bubble In the middle of the hemisphere. It could be equally possible in form the junction <NUM> anywhere in this arrangement; the location at the hemisphere is merely an example.

Alternatively, a more complete bubble could be created and the silicone cannula could be slipped into a defect at the end to perform the same function.

It should be noted that the terms used are basically smooth (silicone, plastics, metals) and rough or textured surfaces (Dacron, Teflon, ePTFE). It is also possible to have a tightly woven or knitted material that is typically called a textile, but could function as a smooth surface.

Also, it is possible to create a tightly woven polyester that behaves like a smooth surface. It could be possible to bring a tightly woven sewable graft into direct contact with a silicone surface without an intervening "bubble" or step.

It may also be important to prevent these conduits from collapsing as they can be located below the skin and could be crushed by a patient lying on them. Reinforcement of the conduits with plastic or wire spirals or rings can be used here. In addition, extra thicknesses of polymer or plastic could be added make them stronger.

In various embodiments, any of the devices and techniques described herein may be used in any suitable combination with the devices and techniques described in the Appendices.

As utilized herein, the terms "approximately," "about," "substantially" and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and are considered to be within the scope of the disclosure.

For the purpose of this disclosure, the term "coupled" means the joining of two members directly or indirectly to one another. Such joining may be stationary or moveable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or may be removable or releasable in nature.

Claim 1:
A vascular graft comprising:
at least one conduit (<NUM>) having a first conduit region and a second conduit region, the second conduit region including a bulbous portion (<NUM>) with respect to the first conduit region;
at least one first support strut (<NUM>) positioned in the first conduit region, the at least one first support strut (<NUM>) formed in a spiral configuration; and
at least one second support strut (<NUM>) positioned in the second conduit region,
wherein the conduit (<NUM>) is formed by a first zone and a second zone which make a single graft,
characterised in that the first zone is infiltrated with silicone rubber to inhibit cellular ingrowth and the second zone is of a porous nature to promote ingrowth.