False lumen occluder

An endoluminal device for repairing an aortic dissection and preventing future aortic dissections, the device including a plurality of struts with at least one of the plurality of struts having a mid-strut portion having two or more secondary struts, the device being configured to be secured within a false lumen of the aorta and contain filler material in order to encourage thrombosis within the false lumen.

BACKGROUND

Aortic dissection is a condition that affects the aorta, which is the largest artery in the body. This condition is caused by the separating/dissection of the individual layers of the aorta, where the inner layer of the aortic wall tears, or peels, away from the adjacent layer of the aorta. This separation of the layers creates an area, or a pathway, between the torn-away layer and the remainder of the aortic wall. The area created by the two layers is called a false lumen. As blood flows through the aorta, it travels through its normal pathway, referred to as the true lumen, but a portion of the blood also is directed into the false lumen.

The false lumen is a secondary flow path that does not provide any blood delivery to the remainder of the body. As blood continues to be diverted into the false lumen, the rate of blood flow and volume of diverted blood into the false lumen can result in the exertion of large forces against the aortic wall. These forces result in the further propagation of the tear, thereby creating a larger false lumen and greater associated forces. The propagation of the tear can eventually lead the aorta wall to rupture, which can result in death.

The type of treatment for this condition depends on the severity and location of the aortic tear. Medical therapy, such as blood pressure and cholesterol-lowering drugs, are typically provided as one method of treatment for this condition. Medical therapy is designed to limit further propagation of the tear and to reduce the chances of aortic rupture. This type of treatment is adequate when the condition is in its early stages and no significant tear exists. However, it is not designed to prevent the further propagation of a dissected portion of the aortic wall.

In situations where the condition has progressed to a point where the risk of aortic rupture or further propagation is higher, more aggressive types of treatment may be required. Such additional types of treatment include endovascular intervention and open surgical repair. Endovascular intervention is a minimally invasive procedure where a stent graft is placed within the damaged area. When expanded, the stent graft exerts a radial force along the damaged area, thereby forcing the dissected layer of the aorta against the adjacent layer of the aortic wall. In theory, retaining the dissected layer of the aorta against the adjacent layer of the aortic wall prevents blood from flowing into the dissected layer, thereby minimizing the blood flow into the false lumen. This type of treatment, however, only covers the dissected layer and sometimes does not fully occlude the false lumen formed between the dissected layer and the adjacent layer of the aortic wall. As a result, and typically in chronic aortic dissection cases, there is a likelihood that blood will continue to flow between the dissected layer and the adjacent aortic layer, thereby causing the dissected portion of the aortic wall to further separate from the adjacent layer of the aortic wall which allows additional blood to reenter the false lumen. Another disadvantage of this type of treatment is that it does not prevent the chances of future tears in the damaged area. As a result, endovascular repair is an inadequate method of treatment for patients suffering from chronic aortic dissection.

Open surgical repair is another type of treatment used to cure aortic dissection. This highly invasive procedure requires the replacement of the diseased portion of the aorta with a Dacron/ePTFE graft. The graft is sewn in the place of the removed portion of the aorta and on average requires a two-month recovery period. As true with other highly invasive medical procedures, open surgical repair is a lengthy procedure and subjects patients to a higher risk for stroke, ischemia, and other medical complications. As a result, this type of procedure is not recommended to treat aortic dissection cases unless no other treatment is available and carries a high likelihood of post-surgical complications.

Therefore, there is a need for another type of medical treatment to prevent against chronic aortic dissection while minimizing the complications related to open surgical treatment.

BRIEF SUMMARY

In one embodiment of the present invention, the intraluminal device comprises a first end, a second end, and a central longitudinal axis between the first and second ends and expanded and compressed configurations, where a plurality of struts extend from the first to second end of the intraluminal device with at least one of the struts having a proximal strut portion, a distal strut portion, and a mid-strut portion between the proximal strut portion and the distal strut portion, where the mid-strut portion has at least two struts, and when the intraluminal device is in the expanded configuration, the plurality of struts are biased away from the longitudinal axis.

In another embodiment of the present invention, the intraluminal device comprises a first end, a second end, and a central longitudinal axis between the first and second ends and a expanded and compressed configurations, where a plurality of struts made from the same piece of material extend from the first to second end of the intraluminal device with at least one of the struts having a proximal strut portion, a distal strut portion, and a mid-strut portion between the proximal strut portion and the distal strut portion, where the mid-strut portion has at least two struts, and when the intraluminal device is in the expanded configuration, the plurality of struts are biased away from the longitudinal axis and the at least two struts of the mid-strut portion have an arcuate shape.

In yet another embodiment of the present invention, the intraluminal device comprises a first end, a second end, and a central longitudinal axis between the first and second ends and expanded and compressed configurations, where a plurality of struts made from the same piece of material extend from the first to second end of the intraluminal device with at least one of the struts having a proximal strut portion, a distal strut portion, and a mid-strut portion between the proximal strut portion and the distal strut portion, where the mid-strut portion has at least two struts made out of the same material as the plurality of struts, and when the intraluminal device is in the expanded configuration, the plurality of struts are biased away from the longitudinal axis and the at least two struts of the mid-strut portion have an arcuate shape.

To help understand this invention, the following definitions are provided with reference to terms used in this application.

Throughout this specification and in the appended claims, when discussing the application of this invention with respect to the aorta or other blood vessels, the term “distal” with respect to such a device, or false lumen occluder, is intended to refer to a location that is, or a portion of the device that when implanted, is further downstream with respect to blood flow; the term “distally” means in the direction of blood flow or further downstream. The term “proximal” is intended to refer to a location that is, or a portion of the device that when implanted is, further upstream with respect to blood flow; the term “proximally” means in the direction opposite to the direction of blood flow or further upstream.

The term “intraluminal” describes objects that are found or can be placed inside a lumen in the human or animal body. A lumen can be an existing lumen or a lumen created by surgical intervention. This includes lumens such as blood vessels, such as an aorta, parts of the gastrointestinal tract, ducts such as bile ducts, parts of the respiratory system, etcetera. “Intraluminal device” is thus a device that can be placed inside one of these lumens. An expandable device having a plurality of struts is a type of intraluminal device.

The embodiments below are described with reference to the drawings in which like elements are referred to by like numerals. The relationship and functioning of the various elements are better understood by the following detailed description. However, the embodiments as described below are by way of example only, and the invention is not limited to the embodiments illustrated in the drawings.

This invention relates to an intraluminal device having a plurality of struts extending from a first end of the device to the second end of the device. Along at least one of the struts is a mid-strut portion having two secondary struts. The method of delivery and placement of the intraluminal device within a lumen is also part of the invention described herein.

In the preferred embodiment, shown inFIG. 1, an intraluminal device10in an expanded configuration is shown. The intraluminal device10includes a first end12and a second end14, where the first end12and second end14are along a central longitudinal axis A. A plurality of struts16extend from the first end12to the second end14and are made out of a single piece of material. Each of the plurality of struts16include a proximal portion18that is adjacent to the first end12and a distal portion20that is adjacent to the second end14of the intraluminal device10. In this embodiment, there are16struts16, however the number of struts16in a particular embodiment may vary and can range anywhere between 10 and 25.

As further shown inFIG. 1, each of the plurality of struts16further includes a mid-strut portion22. The mid-strut portion22is located between the proximal strut portion18and the distal strut portion20for each strut16of the plurality of struts. In this embodiment, the mid-strut portion22of the strut16comprises two secondary struts24that diverge from the proximal portion18of the strut16and converge into the distal portion20of the same strut16. The number of secondary struts24per each mid-strut portion22can vary anywhere between two, which is shown in the embodiment disclosed inFIG. 1, up to, and including, six. Moreover, a single strut16may also have more than one mid-strut portion22, with each midstrut having two or more secondary struts24extending therefrom.

The secondary struts24permit expansion of the intraluminal device10to significantly larger diameters than would otherwise be possible with just a single strut, and also reduce the extent of foreshortening the intraluminal device10undergoes upon expansion. The secondary struts24also contribute to enhanced stiffness of the intraluminal device10during loading, deployment and in vivo. Further, the secondary struts24increase the amount of metal in the intraluminal device10without contributing to the overall stiffness.

It can be appreciated that the number of secondary struts24in a particular embodiment may also vary. For example, it is contemplated that in one embodiment of the intraluminal device10, one strut16may have zero secondary struts24, another strut16may have two secondary struts24, and yet another strut16may have four secondary struts24, and so forth.

The relative locations and lengths of the mid-strut portion22with respect to the proximal stent portion18and distal stent portion20may vary and is application dependent. For example, depending on the desired location of secondary struts24relative to the first end12and the second end14of the intraluminal device10, the mid-strut portion22may be closer to one of the ends12,14. In addition, the length of each of the secondary struts24may also vary depending on the intended application. For example, in the embodiment shown inFIG. 1, the mid-strut portion22is approximately one half the overall length of the strut16. This ratio may change depending on a particular application.

The struts16of the intraluminal device10are configured to expand and compress such that the struts16are substantially parallel to the longitudinal axis A when in the compressed configuration.FIG. 2depicts the intraluminal device10shown inFIG. 1in a compressed configuration, where the struts16are substantially parallel to one another. When in the expanded configuration, the intraluminal device10may have a length anywhere between 10-80 mm and an outer diameter of anywhere between 5-50 mm. When in the compressed configuration, the length can vary from anywhere between 10-150 mm and have a compressed outer diameter of anywhere between about 5-18 Fr. The intraluminal device10is intended to have minimal radial force (just enough to enable deployment within the false lumen). The pattern shown in the preferred embodiment disclosed inFIG. 1lends itself to this design goal. Specifically, the pattern shown inFIG. 1is laser cut from a drawn, seamless tube, expanded to its final diameter and heat-set to retain the expanded shape. The pattern consists of a series of struts16that run parallel to the long axis of the intraluminal device10, without any circumferential interconnections. The struts16are bifurcated at approximately ⅓rd the distance from either end12,14of the intraluminal device10to form a pair of secondary struts24, intended to enhance stability. The lack of circumferential interconnections is intended to reduce radial force and crush resistance.

In addition, the forces required to compress the pattern into its compressed configuration (during loading) are minimized as well. In its operational state, the intraluminal device10is intended to have radial and flat plate crush resistance less than a typical stent graft (e.g., less than 15 N) used for treatment of aortic aneurysms or dissections. This is essential to promote thrombosis of the false lumen and stabilization and opening of the true lumen as the blood flow increases through the lumen.

The size and shape of the struts16and secondary struts24may vary depending on a particular application. In the preferred embodiment shown inFIGS. 1 and 2, each strut16has a length of 20 mm and a width of 220 μm and each of the two secondary struts24has a length of approximately 25 mm and a width of approximately 92 μm. When in the expanded configuration, each of the two secondary struts24and form a 40 mm opening, or luminal diameter, 66 therebetween.

It can be appreciated that the dimensions of the secondary struts24of a particular strut16may depend on the number of secondary struts24for that particular embodiment. For example, if a particular strut16has two secondary struts24, the width of each secondary strut will approximately be one half of the width of the strut16. And if a particular strut16has three secondary struts24, the width of each secondary strut24will approximately be one third of the width of the strut16. However, this relationship between the number of secondary struts24and the width of the primary strut16is not required and there also may be instances where the width of each of the secondary struts24for a particular strut16may be not be equal to one another.

In the embodiment shown inFIGS. 1 and 2, the intraluminal device10is made out of a single piece of material. The types of material from which the intraluminal device10may be manufactured include a shape memory alloy comprised of Nickel and Titanium, which is commonly referred to as Nitinol, and Teritary alloys. As shown inFIG. 3, the intraluminal device10in this embodiment is manufactured out of a single cylindrical tube26. The cylindrical tube26has a plurality of primary cuts28formed along the longitudinal axis A. The primary cuts28form the struts16of the intraluminal device10. Between each primary cut28is a secondary cut30, which also extends along the longitudinal axis A. As shown inFIG. 3, the secondary cuts30are not as long and wide as the primary cuts28and form the secondary struts24of the intraluminal device10. In this embodiment, the struts16and the secondary struts24have a rectangular-shaped cross-section.

The dimensions of the cuts28,30may vary between embodiments and within a single embodiment. For example, the respective lengths of each of the primary cuts28and secondary cuts30may vary in a single embodiment and the width of the cuts28,30may vary along a single cut, such that the width of the cut28,30may increase from the first end12as it approaches the mid-strut portion22and then decrease as it approaches the second end14, or vice versa, thereby affecting the shape and width of the struts16,24. As shown inFIG. 3, the path, or pattern, along which the cuts28,30are made is substantially parallel to the longitudinal axis A. However, it is contemplated that the cuts28,30may have a helical or a spiral-type path, or pattern, about the cylindrical tube26.

FIG. 4is the intraluminal device10shown inFIG. 3in the expanded configuration. As shown in this figure, when in the expanded configuration, the struts16have an arcuate shape that bows away from the longitudinal axis A, and the secondary struts24of each strut16bias or bend away from one another. The secondary struts24may bias away from each other in directions relative to the longitudinal axis, for example radially inward and outward. For example, one secondary strut24may bias toward the axis and the other away from the axis. Alternatively, and preferably, the secondary struts24may bias away from the longitudinal axis A and from one another in a radial direction. When in the expanded configuration, the intraluminal device10is ellipsoidal in shape. It is contemplated that the intraluminal device10may have other shapes, such as a spherical shape, depending on the geometry and pattern of the struts16,24. When in the expanded configuration, the overall length of the intraluminal device10is less than when in the compressed configuration, and the maximum outside diameter of the intraluminal device10is greater than when in the compressed configuration.

In an alternative embodiment, shown inFIG. 5, the intraluminal device10is made of a plurality of independent struts32, each having a first end34and a second end36. In this embodiment, each of the first ends34of the independent struts32are held together via a first hub38and each of the second ends36of the independent struts32are held together via a second hub40. The independent struts32in this embodiment may also have a mid-strut portion with secondary struts that is substantially the same as the mid-strut portion22and secondary struts24described above with respect to the first embodiments.

The intraluminal device10is intended to be placed into false lumen42of an aorta44, a pictorial representation of which is shown inFIG. 6. The false lumen42is a pocket created by a tear in the lining46of the aortic wall. A portion of the aortic lining46separates from an adjacent portion of the aortic lining47thereby forming a pocket. Blood flow is partially diverted into this pocket thereby creating a false lumen42. The pressure of the blood flow and collection of blood in this lumen42can cause the torn portion of the aortic lining46to propagate and eventually lead to the rupture of the aortic wall.

As shown inFIG. 7, the intraluminal device10is loaded onto a deployment device48for insertion into a vessel. The deployment device48includes a guide wire catheter50having a first end60with a nose cone dilator52attached thereto. The intraluminal device10is located along a body62of the guide wire catheter50and may be radially compressed and secured thereto by two trigger wires58, which form loops around the intraluminal device10. A sheath56is disposed over the guide wire catheter50and intraluminal device10. The sheath56assists the trigger wires58in retaining the intraluminal device10in the compressed configuration prior to deployment. Note that the sheath56alone may be sufficient to retain the intraluminal device10to the body62of the catheter50. The superelastic property of Nitinol allows the struts16,24of the intraluminal device10to undergo considerable deformation, such as radial compression, yet return to their original shape when the compression force is removed. In the preferred embodiment, a formulation of Nitinol comprising about 49.5% to 51.5% Nickel (atomic %) and about 50.5% to 48.5% Titanium is used (atomic %). Preferably, an equiatmoic formulation of Nitinol is used. Additional formulations, consisting of ternary alloys (e.g. Nitinol doped with 0.25 at % Chromium) may be used. As a result of the superelastic property, the intraluminal device10may be placed in a compressed or collapsed configuration as shown inFIG. 9, yet expand back to its original configuration when deployed from the deployment device48within the vessel.

In an another embodiment, the deployment device48, as shown inFIG. 8, includes a guide wire catheter68having a first end70and a second end72and a reduced diameter portion76adjacent to the second end72. A cap74is disposed on the second end72and forms part of the guide wire catheter68. The cap74forms a cavity78between it and the second end72in which a portion of the intraluminal device10may reside in the compressed configuration. Prior to deployment, the intraluminal device10is positioned along the reduced diameter portion76and is retained by a sheath56and the cap74such that the intraluminal device10is retained in the compressed configuration.

FIGS. 9-11depict the deployment of the intraluminal device10within a blood vessel, which in this instance is the aorta44. As shown inFIG. 9, a guide wire54is inserted through a femoral artery and is positioned within or adjacent to the false lumen42. Alternatively, the guide wire54may be introduced via the subclavin artery into the aortic arch and positioned within or adjacent to the false lumen42. In either scenario, the deployment device48is inserted along the guide wire54and positioned at a point of deployment within the false lumen42. Once the deployment device48reaches the desired point of deployment, the sheath56is retracted, as shown inFIG. 10. Finally, the trigger wires58securing the intraluminal device10to the body62of the guide wire catheter48are disengaged from the intraluminal device10.

As the sheath56retracts, the intraluminal device10expands from its compressed configuration to its expanded configuration, as shown inFIG. 11. In an alternative method of deployment, the sheath56may be retracted before the trigger wires58disengaged from the intraluminal device10. In this scenario, the disengagement of the trigger wires58from the intraluminal device10will cause the intraluminal device10to expand into its expanded configuration as shown inFIG. 11. As discussed above, the outside diameter of the intraluminal device10when in the expanded configuration can range between about 5-50 mm, and the exact diameter is determined by the size of the false lumen42, which can vary anywhere between 5-20 mm. The radial force exerted by the struts16,24of the intraluminal device10ranges from 0.1 to 10 N and helps secured the intraluminal device10within the false lumen42.

Once the intraluminal device10is in the expanded configuration and secured within the false lumen42, a filler material64may be inserted into the void formed by the expanded struts16,24. Examples of the filler material64include: embolization coils, small intestinal submucosa (SIS), hydrogels, PETE, such as Dacron®, and microspheres. MReye® is one type of embolization coil that may be inserted into the intraluminal device10. MReye® is used for arterial and venous embolization in the peripheral vasculature and is manufactured by Cook Medical Inc., located in Bloomington, Ind. The filler material64may be inserted into the cavity by a second catheter or through the same deployment device48that deployed the intraluminal device10within the false lumen42. In the alternative, the filler material64may be disposed within the intraluminal device10prior to being loaded onto the deployment device48.

The filler material64within the intraluminal device10encourages the thrombotic process to occur within the false lumen42. In some instances, once the intraluminal device10is placed within the false lumen42, an endovascular stent or a stent graft may be placed in the true lumen43in order to retain the patency of the true lumen43and encourage the thrombotic process. Thrombosis will occur as a result of the filler material64causing turbulence and/or stagnation in the blood flow in the false lumen42. Over time, the thrombosed area will grow, with the goal being to completely occlude the false lumen42from any pressurized blood blow. The blood flow will then be restored to the normal vessel pathway. As the vessel begins to heal, it will begin to remodel and strengthen and the true lumen43will stabilize and begin to expand. The expansion of the true lumen43will cause the false lumen42to collapse. The intraluminal device10has a low plate stiffness in the range of 0.1 to 10 N, which is far less than the radial force generated by the increased blood pressure exerted (or a stent graft that may be placed) within the true lumen43. As a result, the intraluminal device10will begin to collapse as a result of the increased blood flow. The intraluminal device10will eventually achieve a low profile compressed configuration, as shown inFIG. 12.

In an alternate embodiment, the intraluminal device10is wrapped in a membrane80, as shown inFIG. 13. In this embodiment, the membrane80is made out of a Dacron polymer fiber. The fibers are applied to the struts16of the intraluminal device10through a method referred to as electrospinning.

The membrane80prevents additional blood from entering the false lumen42and thereby decreasing the further propagation of the tear. The membrane80may be made out of any suitable fiber, or material, that exhibits substantially the same properties as Dacron, including a hemostatic type of collagen or SIS. The wrapping, or covering, process occurs via electrospinning when the intraluminal device10is in a compressed configuration. It is desired to perform the covering process when the intraluminal device10is in this configuration in order to prevent the covering to split apart when the intraluminal device10is compressed as it is loaded onto the deployment device. Otherwise, if the covering process was performed when the intraluminal device10was in a non-compressed configuration, the individual layers, or strands, of the membrane80would not be taught and would increase the likelihood of separating from one another during the loading process. In addition, a hemispherical ground plate is used during the electrospinning process to help attract fibers to the intraluminal device10being coated with the membrane80. The hemispherical ground plate provides improved control of the location the fibers of the membrane80are coated on the intraluminal device10.

While the present invention has been described in terms of preferred examples, and it will be understood that the invention is not limited thereto since modifications may be made to those skilled in the art, particularly in light of the foregoing teachings