Patent Description:
An artificial shunt serves as a hole or small passage that allows movement of fluid from one part of a patient's body to another, or, more specifically, from one body lumen to another body lumen. Such body lumens can be associated with virtually any organ in the body but are most commonly associated with lumens in the heart, lungs, cranium and the liver.

Shunts can be used to treat many different conditions. Such conditions include, but are not limited to, pulmonary hypertension, heart failure, hypertension, kidney failure, volume overload, hypertrophic cardiomyopathy, valve regurgitation, and numerous congenital diseases.

Numerous prior art shunt designs exist as exemplified by <CIT>. As is appreciated by one of skill in the art, the efficacy and safety of a shunt in its intended application largely depends on such attributes as precise shunt placement, secure shunt fixation, shunt durability, minimization of regions of possible fluid stasis, ease of deployment, and adjustability over time, to name a few. <CIT> discloses an elongate anastomosis shunt having compressed and radially expanded configurations, the shunt comprising a central portion and two flared end portions.

As such, there is a need to constantly improve and refine prior art shunt designs to arrive at a shunt that effectively and safely treats multiple conditions while at the same time allows for ease of use and reduced costs.

The present invention is directed to a shunt that expands to an hourglass shape. As the shunt expands, both of its ends radially flare outwards relative to its middle section. Additionally, the length of the shunt foreshortens which causes the flared ends to engage the tissue surrounding a puncture or aperture within a patient's tissue, not unlike a rivet.

The shunt achieves this shape by having a laser-cut body that forms a plurality of cells. The cells near the middle of the shunt have a smaller size (e.g., length, width) than the remaining cells. The cells near both the proximal and distal ends of the shunt have a larger size (e.g., length, width) than the middle cells, causing them to radially expand to a greater diameter. Further, as the cells radially expand, they increase in width, which causes their length to decrease. The decreased cell length causes the shunt, as a whole, to foreshorten or decrease in length.

The shunt can be deployed with a balloon catheter. The shunt is compressed over the balloon catheter and, when inflated, causes the shunt to expand.

The balloon catheter has a balloon that inflates to an hourglass shape. In other words, the balloon's proximal and distal regions expand to a larger diameter relative to the middle portion.

In one example method not covered by the appended claims, a distal end of a balloon catheter has a shunt disposed over its balloon. The shunt and balloon are positioned about halfway through an opening in a patient's tissue. The balloon is inflated to an hourglass shape, causing the shunt to similarly expand to an hourglass shape while also foreshortening. The flared ends of the shunt are thereby caused to engage the tissue surrounding the opening.

The method can further include a later, secondary expansion of the shunt to further increase its diameter. This can be achieved by advancing a second balloon catheter into the shunt and expanding its balloon to a desired shunt passage diameter.

In another embodiment of the present invention, the shunt includes barbs, hooks or similar anchoring mechanisms on its outer surface.

These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which.

The present invention is generally directed to a shunt. More specifically, the shunt radially expands to an hourglass or rivet shape while also longitudinally foreshortening. The shunt is initially positioned within a tissue opening and then expanded, which causes the distal and proximal ends of the shunt to flare radially outwards and move towards each other. When fully expanded, these radially flared ends engage the tissue surrounding the opening, creating a smooth transition between either side of the tissue.

This shunt design provides several advantages over prior shunt designs. For example, the shunt may "self-position" itself within the tissue opening due to its flared shape and therefore provides increased precision in its positioning than prior designs. The flared portions also provide strong attachment to the surrounding tissue as compared with prior shunt designs. Finally, the shunt may have a small collapsed profile and yet can expand to a consistent inner diameter with high radial force. This allows the use of low-profile balloons to assist in the expansion of the shunt to achieve consistent and reliable implantation results.

A stent design that can be modified for use as a shunt in accordance with the principles of the present invention as explained herein is disclosed in <CIT>.

As discussed in greater detail in this specification, the foreshortening and hourglass shape can be achieved in several different ways and the shunts themselves may have several different features. It should be explicitly understood that the features shown in the different embodiments of this specification can be interchangeably used with features of other embodiments in this specification. In other words, it is intended that the features of the embodiments can be "mixed and matched" with each other.

<FIG> illustrate the change in shape of one embodiment of a tubular shunt <NUM> of the present invention. In <FIG>, the shunt <NUM> is shown in a radially compressed configuration having a relatively long length <NUM> and a relatively small, uniform diameter <NUM>. As the shunt <NUM> is deployed, its length substantially decreases to <NUM>' and its diameter increases. More specifically, end portions 100A increase to a maximum radial diameter of <NUM>' and then decrease in diameter towards a middle region 100B, which has a diameter of <NUM>".

In one example, when compressed, the shunt <NUM> has a length <NUM> of about <NUM> and a diameter <NUM> of about <NUM>, and when expanded the shunt <NUM> has a diameter <NUM>' of the end portions 100A of about <NUM> and a diameter <NUM>" of the middle region 100B of about <NUM>.

In another example, when compressed, the shunt <NUM> has a length <NUM> of about <NUM> and a diameter <NUM> of about <NUM>, and when expanded the shunt <NUM> has a diameter <NUM>' of the end portion 100A of about <NUM> and a diameter <NUM>" of the middle region 100B of about <NUM>.

As seen in <FIG>, this embodiment of the shunt <NUM> includes a plurality of tubular radial bands <NUM> that are each formed from a plurality of uniform, alternating waves that create the shunt passage 100C. Put another way, and referring particularly to <FIG>, each radial band <NUM> comprises a plurality of straight regions 107B joined together to create a pattern of triangular peaks 107A that alternate their longitudinal directions. The peaks 107A of each radial band <NUM> are aligned with each other and connected via a small, straight portion <NUM>, which effectively creates diamond-shaped cells <NUM> when radially compressed. As a result of this design, the angle of each peak 107A increases as the shunt <NUM> is radially expanded and the radial bands <NUM> become closer together to each other, which causes longitudinal foreshortening (i.e., a decrease in length of the shunt <NUM>).

One mechanism for causing the radial flaring of the ends 100A of the shunt <NUM> can be seen in <FIG> and <FIG>, which illustrate the pattern of the shunt <NUM> as if it were longitudinally cut and flattened. Specifically, a pattern of cells <NUM> can be created in which some cells 102A, 102B, 102C, 102D are longer in their proximal-to-distal length than other cells (i.e., they have longer straight regions 107B). Preferably, cells <NUM> in the middle of the shunt <NUM> have the smallest length and each row of cells <NUM> progressively increase in length the further away from the middle they are. Alternately, larger length cells <NUM> can be located only near the ends of the shunt <NUM>.

For example, middle cell 102A has a first length; longitudinally adjacent cell 102B has a second, longer length than cell 102A; longitudinally adjacent cell 102C has a third, longer length than cell 102B; and longitudinally adjacent cell 102D has a fourth, longer length than cell 102C.

To better see this distinction, <FIG> comparatively illustrates cells 102A and 102D next to each other. In a compressed configuration, the larger cell 102D will have longer straight portions 107B and a smaller angle of peak 107A relative to cell 102A. However, when expanding, the larger straight portions 107B allow those cells to expand to a larger diameter and foreshorten more than cell 102A. In this manner, the expanded shape and amount of foreshortening can be determined.

The size and ratio of the cells <NUM> and straight portions 107B can vary, depending on the desired expanded shape of the shunt <NUM>. For example, having dramatically larger end cells (e.g., cells 102C and 102D) may cause the expanded configuration of the shunt <NUM> to have a larger flare diameter size relative to its middle portion. In one specific example, the size increases of the straight portion 107B (i.e., struts) of each radial band <NUM> can be seen in the following listing, which begins with the straight portion 107B in the middle cell 102A and progresses towards the end of the shunt <NUM>. For a shunt with flaring on both ends, the progression of size increase would be the same on either side of the center region of the shunt. It will be appreciated that through creative configurations of the size progression described herein, one flare could be a different size or configuration from its opposite flare and thus the shunt can be specifically tailored to the particular use and location in the patient's body. Note, this specific example illustrates a greater number of straight portions 107B and therefore cells <NUM> than that shown in <FIG>. However, the shunt <NUM> may include a variety of different cell numbers. Straight portion 107B example sizes: <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

In addition to the variable size of the cells <NUM> along the length of the shunt <NUM>, the shunt <NUM> can be heat set to an hourglass shape when unconstrained to provide additional expansion force, either with or without the assistance of a balloon catheter.

Notwithstanding the above cell design, it is noted that multiple cell variations are contemplated in accordance with the present invention. In this regard, a key design parameter is that each "row" or band in the shunt body reaches maximum expansion at a particular diameter to achieve the final desired shape.

The shunt <NUM> can be delivered and expanded via a balloon catheter <NUM>, as seen in <FIG>. In one embodiment, a balloon <NUM> is disposed on its distal end of a tubular catheter body <NUM>. The interior of the catheter body <NUM> has an inflation lumen 112A that opens to proximal and distal inflation ports 112B within the balloon <NUM>. A guidewire lumen <NUM> is located within the catheter body <NUM>, opening on the proximal and distal ends of the body <NUM>.

As seen in <FIG>, the balloon <NUM> may inflate to an hourglass shape that has a smaller diameter middle region 114C than the proximal region 114A and distal region 114B of the balloon <NUM>. There are several different techniques to achieve this inflated shape of the balloon <NUM>. For example, the balloon <NUM> can be composed of a compliant material and a non-compliant band (not shown) can be positioned around the middle region 114C. In another example, the proximal region 114A and distal region 114B can be composed of a material with different expansion properties than the middle region 114C (e.g., a compliant middle region with noncompliant proximal/distal regions, or a noncompliant middle region with compliant proximal/distal regions).

<FIG> illustrate the shunt <NUM> positioned over the balloon <NUM>. Preferably, the shunt <NUM> is loaded onto the balloon <NUM> so that the middle region 100B of the shunt <NUM> is aligned with the middle region 114C of the balloon <NUM>. In that regard, as the balloon <NUM> expands, the proximal region 114A and distal region 114B cause the end regions 100A of the shunt <NUM> to expand to a larger diameter than the middle region 100B.

<FIG> illustrate how the shunt <NUM> may be delivered relative to an area of target tissue <NUM>. First, an initial puncture is made at the desired location (e.g., with a needle). Next, the distal end of the delivery catheter <NUM> is advanced through the puncture in the tissue <NUM> such that there are roughly equal portions of the shunt <NUM> on either side of the tissue <NUM>. Either the shunt <NUM> or the delivery catheter <NUM> can include radiopaque markers at various known locations to assist a physician with achieving a desired alignment.

When the desired alignment is achieved, the balloon <NUM> is inflated, causing the shunt <NUM> to increase in radial diameter to an hourglass shape and to foreshorten. The shunt <NUM> is configured such that the foreshortening causes the flared end regions 100A to engage and press into the tissue <NUM>. These flared end regions 100A, as well as the proximal region 114A and distal region 114B of the balloon help "self-center" the shunt <NUM> to an appropriate position. The end result is an opening in the tissue <NUM> with a smooth, funnel-like transition on each side of the tissue.

One variation on this delivery technique allows for the passage through the shunt <NUM> (i.e., the narrowed middle region 110B) to be resized after delivery, if needed. Specifically, the shunt <NUM> can be delivered as previously described, but the narrowed middle region 110B is expanded to an initial diameter that is smaller than the middle region 110B is capable of expanding to. This may be achieved, for example, by limiting the expansion size of the middle region 114C of the balloon <NUM>. If the physician determines that increasing the size of the middle region 100B of the shunt <NUM> would be beneficial, the middle region 100B can be further expanded in diameter by either a different portion of the balloon (e.g., 114A or 114B) or by a second balloon catheter that inflates to a desired passage diameter.

Alternately, if the physician determines that the middle region 100B of the shunt <NUM> was initially deployed with a diameter that is larger than desired, a second delivery catheter may be used to deliver a tubular spacer having a thickness that reduces the size of the passage through the middle region 100B. In one example, the tubular spacer may be a second shunt <NUM>, similar to the shunt initially deployed but deployed inside of the first shunt.

This ability to resize the shunt <NUM> after delivery allows a physician to customize the amount of shunted fluid for each individual patient. It also allows the shunt <NUM> to be modified at a later date if the patient's hemodynamic needs change.

In an alternate embodiment, the balloon catheter may include two or three separate, independently inflatable balloons that can be inflated to different sizes to achieve a similar hourglass shape. This may allow the physician to limit expansion of the middle of the shunt <NUM> to a desired diameter while ensuring the ends of the shunt <NUM> radially expand sufficiently to engage the surrounding tissue.

In another alternate embodiment, a mechanical device on a catheter can be used to expand the shunt <NUM> instead of using a balloon. For example, such a catheter may include two cone shaped structures that can be longitudinally slid towards each other. The shunt <NUM> may be positioned between these two structures so that when the cone shaped structures are moved toward each other, they cause the shunt <NUM> to expand.

As previously discussed, the shunt <NUM>' may be composed of a shape-memory material and heat set to the expanded hourglass shape when unconstrained. In such an embodiment, a balloon catheter <NUM> may not be necessary. <FIG> illustrate a similar delivery procedure with a delivery catheter <NUM> configured for deployment of a heat-set shunt <NUM>. The catheter <NUM> includes an elongated catheter body <NUM> with a retractable sheath <NUM> disposed over the shunt <NUM>'. Similar to the previously described deployment procedure, a distal end of the catheter <NUM> is positioned through the opening in the tissue <NUM> such that roughly equal portions of the shunt <NUM> are positioned on each side of the tissue <NUM>. When the desired alignment has been achieved (e.g., by referencing radiopaque markers of a known position), the sheath <NUM> is proximally retracted, causing the shunt <NUM>' to radially expand to an hourglass shape and foreshorten as shown in <FIG>.

In one embodiment, the shunt <NUM> may include a plurality of barbs <NUM>, hooks, or similar fastening structures, as seen in <FIG>. These may be positioned on the outside of the flared regions such that they pierce into the tissue of the patient when the shunt <NUM> is expanded. Alternately, the barbs <NUM> or similar anchoring structure can be located at various locations along the length of the shunt <NUM>, pointing radially outwards.

In one embodiment, the shunt <NUM> lacks any type of cover and acts to maintain the opening through the tissue by mechanical force. <FIG> illustrates another embodiment of a shunt <NUM> having a similar laser-cut structure <NUM> as shunt <NUM> but also a cover layer <NUM> that is attached to the laser-cut structure <NUM> (either on the outside or inside of the structure <NUM>) and forms a similar tubular and hourglass shape. To accommodate the tubular-to-hourglass shape change, part or all of the material <NUM> may be elastic or stretchable. Alternately, a tubular cover layer <NUM> can be included only at the middle region of the laser-cut structure <NUM> of the shunt <NUM>, as seen in <FIG>.

In another embodiment, either of the shunts may have two laser-cut structural layers that are positioned on the inner and outer surfaces of the cover layer so as to "sandwich" the cover layer.

It is sometimes desirable to occlude an existing shunt (e.g., a naturally occurring tissue passage) or chamber such as a left atrial appendage. In that regard, any of the shunt embodiments in this specification may include a material that extends across and occludes the central lumen of the shunt. For example, the material can be a polymer sheet that is attached to an end of the device with a small hole in the center. The polymer sheet may be elastic so that the enter hole expands with the balloon from the delivery catheter and then recovers back down to effectively seal the opening once the balloon is removed.

While the shunt <NUM> and its variations have been previously described to expand to a flared, hourglass style shape, other variations of the expanded shape, not covered by the appended claims, are possible. For example, <FIG> illustrates a shunt <NUM> in which only one end is radially flared outwards while the opposite end 180C maintains a diameter similar to that of the middle region 180B. Since the shunt <NUM> foreshortens in length, it may be beneficial to have barbs or other anchoring mechanisms along the middle region 180B and end 180C to help anchor the shunt <NUM> during radial expansion.

In another example, not covered by the appended claims, neither end of the shunt expands to a flared shape.

The shunts of this specification can be composed of biocompatible materials such as Nitinol or similar alloys, or bioabsorbable materials such as magnesium, PLA, or PLA-PGA. The shunts of this specification may also have features to promote endothelization, such as open surface pores around <NUM> microns in diameter or a polymer coating known to promote tissue growth.

While the shunt <NUM> was previously described with a specific pattern, it should be appreciated that other patterns and designs are possible to achieve similar functionality. For example, <FIG> illustrate a shunt <NUM> comprising a plurality of rings <NUM> comprising a plurality of alternating peaks. These rings <NUM> are fixed to a cover <NUM> and may either be free of connection to each other (other than the cover) or may have connection members <NUM> that connect to longitudinally adjacent peaks. The ends of the shunt <NUM> each include end rings <NUM> that are composed of a plurality of alternating peaks that are larger than those of rings <NUM>. As seen in <FIG>, when radially expanded, the peaks <NUM> longitudinally compress together and fit within each other.

With respect to <FIG>, in one embodiment, the shape depicted therein may be achieved by over-expanding the shunt by a balloon, which would cause the ends to flare open as shown and the central section expansion would be limited by the cover <NUM>.

In addition to having different laser-cut patterns, alternate embodiments may instead be comprised of a plurality of braided wires, such as the shunt <NUM> shown in <FIG>. The shunt <NUM> can be braided on an hourglass-shaped mandrel with a plurality of shape-memory wires. After braiding, the shunt <NUM> can be heat-set on the mandrel and then removed, allowing it to compress to a tubular shape and radially expand to the hourglass shape (i.e., flared end regions 180A and a smaller diameter middle region 180B).

As previously discussed, the delivery catheters <NUM> and <NUM> can include radiopaque markers to help a physician align the shunt <NUM>. However, other positioning devices can also be used to aid in positioning.

For example, <FIG> illustrates a delivery device <NUM> that includes elongated arms <NUM> that are connected to the catheter body at their proximal ends and are configured to radially expand away from the shunt <NUM> at their distal ends <NUM>. The arms <NUM> are preferably of a length that the blunt distal ends contact the tissue <NUM> when the shunt <NUM> is positioned at a desired alignment position (e.g., roughly halfway through the opening). This contact by the arms <NUM> provides the user with tactile feedback in addition to the visualization of the radiopaque markers. To prevent damage to the tissue <NUM>, the arms <NUM> are preferably composed of flexible material, such as nitinol, stainless steel, pebax, nylon, polyurethane, or other plastics. The arms <NUM> can be relatively straight or can form a plurality of waves to provide further flexibility and compression.

<FIG> illustrates another embodiment of a delivery device <NUM> that includes an annular ring <NUM> located over the shunt <NUM> to assist with a desired alignment of the shunt <NUM>. The annular ring <NUM> preferably has a thickness such that it is larger than the opening of the tissue <NUM> when the shunt <NUM> is compressed. The ring <NUM> is longitudinally positioned on a proximal side of the shunt <NUM> such that when contact is made between the ring <NUM> and tissue <NUM>, the shunt <NUM> will have achieved a desired longitudinal alignment through the tissue opening. The ring <NUM> can be composed of cloth, polymer, or bioabsorbable material.

Alternately, instead of an annular ring <NUM>, the shunt <NUM> itself may include structures <NUM> on the shunt <NUM> that are heat-set to radially expand, as seen on device <NUM> in <FIG>. For example, the structures may be a loop, flap, or similar structure that radially pops up when an overlying sheath is withdrawn from the shunt. Similar to the ring <NUM>, these structures <NUM> are positioned at a location so as to provide tactile feedback to the physician to indicate a desired alignment of the shunt <NUM> within the tissue opening.

While the specification has focused on various embodiments of a shunt that are used for creating a shunt within a patient or closing a hole between two vessels or heart chambers, other uses are also possible. For example, the shunt <NUM> may be used an anchor and/or attachment point for additional structures (e.g., tubes, other shunts, etc.). In another example, the shunt <NUM> may be used as an anchoring point for artificial valves, such as a mitral valve or aortic valve. In another example, the shunt <NUM> may be used to help restore a circular shape to a structure (e.g., aortic coarctation).

The shunts and delivery methods described in this specification can be used for a wide variety of shunt procedures. One example is a right-to-right shunt between the right pulmonary artery to superior vena cave, between the pulmonary artery to right atrial appendage, between the pulmonary artery or right ventricle to the venous system, or between the azygous vein to the inferior vena cava. These techniques can be seen in more detail in application number <CIT>. Other possible uses include the creation of shunts between chambers of the heart, such as atrial septostomy, arteriovenous shunt creation for treating hypertension, arteriovenous shunt for fistula creation for dialysis patients, left atrium to coronary sinus, pulmonary artery to left aortic artery, or aorta to pulmonary artery.

Claim 1:
A shunt (<NUM>) for treatment of a patient, comprising:
a tubular structure (<NUM>) having a radially compressed configuration and a radially expanded configuration; and,
said radially expanded configuration comprising a flared state of distal and proximal ends and a foreshortened length;
said flared state and said foreshortened length being sufficient to secure said tubular structure between tissue of two lumens of a patient;
said tubular structure (<NUM>), in its radially compressed configuration, comprising:
a plurality of tubular radial bands (<NUM>), each of which having a plurality of straight regions (107B) joined together to form a pattern of triangular peaks (107A);
said triangular peaks (107A) of each tubular radial band (<NUM>) aligned with each other and connected via a portion (<NUM>) so as to form tubular radial bands (<NUM>) of a plurality of diamond-shaped cells (<NUM>);
characterised in that
said bands of said plurality of diamond-shaped cells (102A, 102B, 102C. 102D) comprising a middle band, a plurality of proximal bands, and a plurality of distal bands;
wherein said plurality of diamond-shaped cells of said plurality of proximal bands and said plurality of distal bands (102D) progressively increase in proximal-to-distal length further away from said middle bands in said radially compressed configuration, causing said plurality of proximal bands and said plurality of distal bands to foreshorten and progressively increase in radial diameter such that said middle band, said plurality of proximal bands, and said plurality of distal bands reach maximum expansion at diameters to achieve said flared state of said distal end and said proximal end, and said foreshortened length.