VASCULAR TREATMENT DEVICES AND ASSOCIATED SYSTEMS AND METHODS OF USE

Abstract

The present technology relates to devices for treating arteries. In several embodiments, for example, the present technology comprises an expandable structure configured to be intravascularly positioned within a lumen of the artery at a treatment site, where the artery has a substantially circular cross-sectional shape at the treatment site prior to deployment of the expandable structure therein. When the expandable structure is in an expanded state and positioned in apposition with the arterial wall at the treatment site under diastolic pressure, the expandable structure may force the artery into a non-circular cross-sectional shape. A cross-sectional area of the artery in the non-circular cross-sectional shape may be less than a cross-sectional area of the artery in the substantially circular cross-sectional shape.

Claims

1. A device for treating an artery of a human patient, the device comprising: an expandable structure configured to be intravascularly positioned within a lumen of the artery at a treatment site, wherein the artery has a substantially circular cross-sectional shape at the treatment site prior to deployment of the expandable structure therein, and wherein, when the expandable structure is in an expanded state and positioned in apposition with the arterial wall at the treatment site under diastolic pressure, the expandable structure forces the artery into a non-circular cross-sectional shape, wherein a cross-sectional area of the artery in the non-circular cross-sectional shape is less than a cross-sectional area of the artery in the substantially circular cross-sectional shape.

2. The device of claim 1, wherein, when the expandable structure is in the expanded state and in apposition with the arterial wall at the treatment site under systolic pressure, the arterial wall deforms in response to the increase in blood pressure towards a more circular cross-sectional shape, thereby deforming the expandable structure as well.

3. The device of claim 2, wherein a cross-sectional area of the artery in the more circular cross-sectional shape is greater than a cross-sectional area of the artery in the non-circular cross-sectional shape.

4. The device of claim 1, wherein the non-circular cross-sectional shape is one of an oval, an ellipse, a rhomboid, or an hourglass.

5. The device of claim 1, wherein the expandable structure comprises two relatively rigid linear elements with curved cross-sections, separated by one or more springs which hold them apart.

6. The device of claim 5, wherein a preload and a geometry of the springs cause a force holding the linear elements apart to decrease as the two linear elements are pressed closer together.

7. The device of claim 1, wherein the artery is the aorta.

8-11. (canceled)

12. The device of claim 1, wherein the expandable structure comprises a superelastic material.

13. The device of claim 1, wherein the expandable structure is non-circular in the expanded state.

14. The device of claim 1, wherein the expandable structure is non-circular when positioned in the arterial lumen in the expanded state.

15-52. (canceled)

53. A device for treating an artery, the device comprising: an expandable structure comprising a first elongated element, a second elongated element, and a spring extending between the first and second elongated elements, the expandable structure being configured to be intravascularly positioned within a lumen of the artery at a treatment site such that the first elongated element is positioned in apposition with the arterial wall at a first position about a circumference of the arterial wall, the second elongated element is positioned in apposition with the arterial wall at a second position about the circumference of the arterial wall spaced apart from the first position, and the expandable structure exerts a radially outward force on the arterial wall, wherein, in response to an increase in pressure within the arterial lumen, a distance between the first and second elongated elements decreases and the radially outward force decreases and wherein, in response to a decrease in pressure within the arterial lumen, the distance and the radially outward force increase.

54. The device of claim 53, wherein, under diastolic pressure, the expandable structure forces the artery into a cross-sectional shape having a cross-sectional area less than a cross-sectional area of the artery prior to deployment of the expandable structure therein.

55. The device of claim 54, wherein under systolic pressure, the arterial wall deforms the expandable structure such that the artery assumes a cross-sectional shape having a cross-sectional area greater than the cross-sectional area of the cross-sectional shape of the artery under diastolic pressure.

56. The device of claim 55, wherein the cross-sectional shape of the artery under systolic pressure is substantially circular and the cross-sectional shape of the artery under diastolic pressure is substantially oblong.

57. The device of claim 53, wherein, the expandable structure is configured to be positioned within the arterial lumen such that the first and second elongated elements extend from first ends to second ends along a longitudinal axis of the artery.

58. The device of claim 53, wherein at least one of the first elongated element or the second elongated element has a curved cross-sectional shape.

59. The device of claim 53, wherein the expandable structure has circumferentially discontinuous cross-sectional shape.

60. The device of claim 53, wherein the spring extends from a first end at the first elongated element to a second end at the second elongated element in a zig-zag pattern.

61. The device of claim 60, wherein the spring is a first spring, the expandable structure further comprising a second spring a first end at the first elongated element to a second end at the second elongated element in a zig-zag pattern.

62. The device of claim 53, wherein the artery is an aorta of the patient.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0238] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure.

[0239] FIGS. 1A and 1B are conceptual diagrams demonstrating arterial compliance during the cardiac cycle.

[0240] FIGS. 2A and 2B schematically depict a test setup for estimating the forces required to change the cross-sectional shape of an aorta from a circle to an ellipse.

[0241] FIG. 3 is a plot of major diameter versus force per linear inch obtained using the test setup of FIGS. 2A and 2B.

[0242] FIGS. 4A and 4B schematically depict a test setup for estimating the forces exerted by an ovular stent on the surrounding aorta when the stent is compressed along its major axis.

[0243] FIG. 5 is a plot of major diameter versus force per linear inch obtained using the test setup of FIGS. 4A and 4B. In FIG. 5, the plot is shown superimposed on the plot of FIG. 3.

[0244] FIG. 6 is a plot of major diameter versus force per linear inch obtained using the test setup of FIGS. 2A and 2B. In FIG. 6, the plot is shown superimposed on the plot of FIG. 3.

[0245] FIG. 7A is a side view of a mesh configured in accordance with several embodiments of the present technology.

[0246] FIG. 7B is a cross-sectional end view of the mesh shown in FIG. 7A, taken along line 7B-7B.

[0247] FIG. 7C is an enlarged, isolated view of a strut of the device shown in FIG. 7A.

[0248] FIG. 7D is an enlarged, isolated view of a strut of the device shown in FIG. 7B.

[0249] FIGS. 8A and 8B show the device of FIGS. 7A and 7B positioned within an artery during systole and diastole, respectively, in accordance with several embodiments of the present technology.

[0250] FIGS. 9A and 9B depict a method for forming a preloaded device in accordance with several embodiments of the present technology.

[0251] FIGS. 10A-10D depict a method for forming a preloaded device in accordance with several embodiments of the present technology.

[0252] FIGS. 11A and 11B depict a method for forming a preloaded device in accordance with several embodiments of the present technology.

[0253] FIGS. 12A-12F are end views of several devices of the present technology that have different cross-sectional shapes.

[0254] FIGS. 13A and 13B are an end view and a side view, respectively, of a device configured in accordance with several embodiments of the present technology.

[0255] FIGS. 14A-14D are end views of several devices of the present technology having different supports.

[0256] FIG. 15A is a side view of a device configured in accordance with several embodiments of the present technology.

[0257] FIG. 15B is an axial cross-sectional view of the device shown in FIG. 15A taken along line 15B-15B.

[0258] FIG. 15C is an axial cross-sectional view of the device shown in FIG. 15A taken along line 15B-15B.

[0259] FIG. 15D is an axial cross-sectional view of the device shown in FIG. 15A taken along line 15B-15B.

[0260] FIG. 16 is an isometric view of a device configured in accordance with several embodiments of the present technology.

[0261] FIGS. 17A-17D show examples of different cross-sectional shapes for the device of FIG. 16.

[0262] FIG. 18A-18E show examples of different cross-sectional shapes for a non-circumferential device configured to apply force to two opposing walls of the aorta.

[0263] FIG. 19 is an isometric view of a non-circumferential device configured in accordance with several embodiments of the present technology.

[0264] FIGS. 20A-20C depict a portion of a device comprising a continuous wire configured in accordance with several embodiments of the present technology.

[0265] FIGS. 21A and 21B are cross-sectional shapes of a device at different blood pressures configured in accordance with several embodiments of the present technology.

[0266] FIGS. 22A and 22B show cross-sectional views of delivery balloons configured in accordance with several embodiments of the present technology.

DETAILED DESCRIPTION

[0267] The present technology relates to devices, systems, and methods for treating blood vessels. According to some embodiments, the device comprises an expandable structure configured to be positioned within the lumen of an artery to influence the cross-sectional shape of the arterial wall during the cardiac cycle. Under diastolic pressure, the expandable structure exerts an elongating force on the arterial wall sufficient to deform the arterial wall into a cross-sectional shape having a cross-sectional area that is less than the natural cross-sectional area of the artery during diastole. The elongating force exerted by the expandable structure, however, may be low enough such that under systolic pressure, the expandable structure allows the artery to deform into a more circular cross-sectional shape.

[0268] The inventors of the present application conducted an experiment to better understand the forces required for a device positioned within the aortic lumen (such as a stent) to change the cross sectional shape of the aorta from substantially circular to elongated under systolic and diastolic pressures. In the experiment, the aorta was approximated by a substantially cylindrical tube having a 1 inch diameter, which is similar to that of the aorta. As shown in FIG. 2A, two pairs of rigid rods were positioned at opposing sides of the tube. As shown in FIG. 2B, the pairs of rods were pulled in opposite directions to simulate forces exerted on the aortic wall by a stent having an elongated cross-sectional shape positioned within the aorta. While the force was applied, water was pumped through the tube at two pressures-88 mmHg (1.7 psi) to simulate diastolic pressure, and 120 mmHg (2.3 psi) to simulate systolic pressure. Force applied versus major diameter was recorded for both pressures as graphically depicted in FIG. 3.

[0269] The inventors hypothesized that deformation of the aorta between a substantially circular cross-sectional shape in systole and an ovular cross-sectional shape in diastole would improve compliance. The hypothesis was based on the premise that the greater the change in cross-sectional shape of the aorta between diastole and systole, the greater the change in cross-sectional area, and hence the greater the system compliance. However, if the stent exerts too much lateral force along the major diameter, the aorta may take the ovular cross-sectional shape in diastole but may not be able to achieve a cross-sectional shape in systole that is sufficiently circular to provide the change in volume necessary to meaningfully improve compliance. Conversely, if the stent is too flexible, the aorta will take a circular cross-sectional shape in systole, but may not be able to achieve a cross-sectional shape in diastole that is ovular enough to provide the change in volume necessary to meaningfully improve compliance. Without being bound by theory, it is believed that the optimal stent characteristics such that the stent would exhibit a lateral force of A (see FIG. 3B) at the given diameter and a force of B (see FIG. 3B) at the other given diameter.

[0270] A second experiment was conducted by the inventors to better understand the forces exerted on a stent deployed within the aortic lumen by the aortic wall as the aortic wall pushes the stent from its heat set, ovular cross-sectional shape to a more circular cross-sectional shape. As shown in FIGS. 4A and 4B, a heat set, ovular stent was placed in a tensile tester between two force plates. The stent was compressed along its major axis to simulate the forces exerted on the short ends 42 of the stent by the aorta during systole. Force applied versus major diameter was recorded and is graphically represented by curve C in FIG. 5. In FIG. 5, curve C is shown superimposed on the diastolic and systolic plots of FIG. 3.

[0271] As shown in FIG. 5, as the ovular stent is compressed along its major diameter towards a more circular shape, the major diameter decreases but the force per linear inch increases. In other words, the more the aorta squeezes an ovular stent toward a more circular cross-sectional shape, the more the ovular stent resists. Because of this, curve C decreases in the direction of the non-circular shape and intersects the systolic pressure curve at point 52 and the diastolic pressure curve at point 54. The resulting difference 50 in major diameter between systole and diastole is minimal (less than 1/20 of an inch), thus providing little additional compliance.

[0272] As detailed herein, the expandable structures of the present technology may have preloaded bend regions that exert a spring force that is generally constant when the expandable structure is compressed along the long dimension. Such a configuration enables the expandable structures of the present technology to follow curve D shown in FIG. 6, thereby providing a greater change in major diameter between diastole and systole and thus improved compliance.

[0273] FIG. 7A is a side view of an expandable, generally tubular structure 100 configured in accordance with several embodiments of the present technology and having preloaded bend regions A and C. FIGS. 8A and 8B show the device of FIGS. 7A and 7B positioned within an artery during systole and diastole, respectively, in accordance with several embodiments of the present technology. As shown, the device 100 may be configured to be intravascularly delivered in a low-profile state to a treatment site within the lumen of an artery. The device 100 may be expanded at the treatment site, thereby assuming a pre-set, non-circular shape.

[0274] The device may comprise an expandable structure configured to be intravascularly positioned within the artery to improve arterial compliance. the aorta at a treatment site. The artery may have a substantially circular cross-sectional shape at the treatment site prior to deployment of the expandable structure, and wherein, when the expandable structure is in an expanded state and positioned in apposition with the arterial wall at the treatment site under diastolic pressure, the expandable structure forces the artery into a non-circular cross-sectional shape, wherein a cross-sectional area of the artery in the non-circular cross-sectional shape is less than a cross-sectional area of the artery in the substantially circular cross-sectional shape.

[0275] As described in further detail below, the device 100 can comprise a plurality of interconnected struts 104, each having a length, a width, and a thickness. As shown in the enlarged view of FIG. 7D, The thickness T can be measured as a dimension that is orthogonal to a central axis when the device 100 is considered in a tubular shape, or as a dimension that is orthogonal to a plane of the device 100 when represented as laid-flat. The length can be measured as a distance extending between ends of a strut, where the ends connect to another structure.

[0276] The minor diameter of the expandable structure may be as small as possible to maximize the volume change as it becomes round. However, the ends of the major diameter should not be sharp enough to cause damage to the aorta walls, and the minor diameter should be large enough that flow through the aorta is not impeded and there is no chance of thrombosis or other occlusion of the aorta. Therefore, the average minor diameter might be in the range of 6 mm-12 mm, and more preferably in the range of 8-10 mm. The expandable structure may increase compliance by 25-50 mL.

[0277] As the volume and pressure of the aorta increases, this will naturally tend to move the aortic walls facing the minor diameter of the stent outwards. As these walls move outwards, the aortic walls facing the major diameter of the stent will be pulled inwards, again since the circumference of the aorta is relatively fixed. As the major diameter of the stent is pulled inwards, the minor diameter will be pushed outwards, since deflecting the stent from an oval cross-section to a more rounded shape will require less force than it would take to compress and reduce the circumference of the stent. Therefore, the stent will become rounder as the aorta becomes rounder, and the stent walls and aorta walls should remain opposed throughout the cardiac cycle. This should lead to the stent healing into the wall over time.

[0278] The stent should be designed so that once deployed in the aorta, an aortic pressure somewhere between diastolic and systolic pressures is enough to distend the aorta from a flattened shape to a rounded shape. This will maximize the effect of the stent in increasing aortic compliance. Therefore with the stent in place, the aorta should preferably deform between an aortic pressure of 60 and 150 mmHg, and more preferably between 90 and 120 mmHg.

[0279] A rough calculation suggests that this device should provide enough compliance to have a significant effect. The typical stroke volume of the heart is 70 ml. Roughly ⅓ of that volume flows through the distal capillaries and organs in systole, leaving ⅔ or about 50 ml to flow during diastole.

[0280] If a perfectly round aorta with an inner diameter of 20 mm were flattened to a flat shape with a minor diameter of 8 mm, then it would have a major diameter of about 26.8 mm. The round aorta would have a cross-section of ˜314 square mm, and the flattened aorta would have an area of ˜201 square mm. Thus, each cm of flattened stent length would provide a potential accommodation of 1.13 ml. A 25 cm stent would provide potential accommodation of 28 mL. This would provide a significant additional compliance to the aorta, enough to provide at least half of the total compliance needed. This should significantly reduce systolic pressure and increase diastolic pressure, allowing the heart to do less work while at the same time improving tissue perfusion.

[0281] FIGS. 9A-11B depict a method for forming a preloaded device in accordance with several embodiments of the present technology. According to some embodiments, for example as shown in FIGS. 9A and 9B, a stent with pre-loaded bend regions can be formed from a plurality of strut regions 902-908. FIG. 9A shows an axial cross-sectional view of the plurality of strut regions 902-908. The plurality of strut regions can comprise a strut region 902 corresponding to a bend region A, a strut region 904 corresponding to a bend region B, a strut region 906 corresponding to a bend region C, and/or a strut region 908 corresponding to a bend region D. Each of the strut regions can include two ends and a bend region having a curvature therebetween. For example, strut region 902 can comprise a first end 1 and a second end 8 with bend region A therebetween. In some embodiments, the strut regions 902 and 906 can be oriented such that the bend regions A and C extend toward each other and the apices of strut region 902 extends away from the ends of strut region 906. Strut regions 904 and 908 can be oriented such that the bend regions B and D extend away from each other and the ends of strut region 904 extend toward the ends of strut region 908. A strut region can be heat treated to form the curvature of the strut region. In some embodiments, strut regions 902 and 906 have equivalent curvatures and strut regions 904 and 908 have equivalent curvatures.

[0282] In some embodiments, the stent can be formed from the plurality of strut regions by joining adjacent apices of neighboring strut regions, such as the stent depicted in FIG. 9B. For example, end 1 can be joined to end 2, end 3 can be joined to end 4, end 5 can be joined to end 6, and/or end 7 can be joined to end 8. The adjacent ends can be joined by laser-welding, resistance-welding, or another suitable method. FIG. 9B shows an end view of an example stent 900 formed from a plurality of strut regions 902-908. Each bend region can comprise an angle defining the degree of biasing of the bend region. In some embodiments, bend regions A and C can comprise an angle φ. Bend regions B and D can comprise an angle θ. In some embodiments, a thickness of the struts in a strut region can be based at least in part on a corresponding angle of the strut region. For example, struts in strut regions 904 and 908 can be narrower and/or thinner than struts in strut regions 902 and 906 because the angle φ of strut regions 904 and 908 is greater than the angle θ of strut regions 902 and 906.

[0283] FIGS. 10A-10D depict a method for forming a preloaded device through heat treatment in accordance with several embodiments of the present technology. FIG. 10A shows an end view of a stent 1000 with a first cross-sectional shape having a long dimension and a short dimension that is orthogonal to the long dimension. In some embodiments, the first cross-sectional shape can be set by a heat treatment process. The stent 1000 can comprise strut regions with corresponding bend regions (e.g., bend region A, B, C, and/or D). According to some embodiments, one or more portions of the stent 1000 can be heat treated to create preloaded bend regions. For example, as depicted in FIG. 10B, the stent 1000′ can be attached to a heat treatment fixture 1002 such that a portion of the stent corresponding to bend region A 1004 is configured to be exposed to heat and a portion of the stent corresponding to bend region C 1006 is insulated. A heat treatment process can be used to set a preloaded shape of bend region A. FIG. 10C depicts the stent 1000″ attached to the heat treatment fixture 1002 such that a portion of the stent corresponding to bend region A 1004 is insulated and a portion of the stent corresponding to bend region C 1006 is configured to be heat treated. In some embodiments, one or more portions of the stent can be heat treated in the same process step. Alternatively, or in addition, portions of the stent can be heat treated individually and/or sequentially. As depicted in FIG. 10D, after heat treatment, the stent 1000′ can comprise a cross-sectional shape that is different from first cross-sectional shape of the stent 1000 before heat treatment (see FIG. 10A). For example, the stent 1000 can comprise a generally ovular cross-sectional shape before heat treatment, as depicted in FIG. 10A. The stent 1000′ can comprise a generally hourglass cross-sectional shape with preloaded bend regions A and C after heat treatment, as depicted in FIG. 10D.

[0284] In some embodiments, a stent can be configured to have one cross-sectional shape in an initial state and another cross-sectional shape in an inverted state. For example, FIG. 11A shows an end view of a stent 1100 in an initial state with an inner surface 1102, and an outer surface 1104. The stent 1100 can comprise bend regions A, B, C, and D and an angle can be defined for each bend region. For example, FIG. 11A shows the stent 1100 with preloaded bend regions B and D. The stent 1100 can be inverted to bend the initial angles of each bend region by about 180 degrees and obtain a stent 1100 in an inverted state, as depicted in FIG. 11B. The stent 1100 in the inverted state can comprise different preloaded bend regions from the stent 1100 in the initial state. For example, as depicted in FIG. 11B, the stent 1100 in the inverted state can comprise preloaded bend regions A and C.

[0285] A cross-sectional shape of a stent as described herein can be defined by a perimeter of the stent. According to some embodiments, a cross-sectional shape can have a long dimension and a short dimension orthogonal to the long dimension. The stent can comprise first portions at either side of the long dimension and second portions at either side of the short dimension. Each of the first portions and the second portions can have a radius of curvature. In some embodiments, a radius of curvature of one first portion is the same as a radius of curvature of the other first portion. A radius of curvature of one second portion can be the same as a radius of curvature of the other second portion.

[0286] FIGS. 12A-12F show end views of several devices of the present technology with different cross-sectional shapes. FIG. 12A depicts an end view of a stent 1200 with a perimeter 1202 that defines a generally ovular cross-sectional shape with a long dimension 1204 and a short dimension 1206. The stent 1200 can comprise first portions 1208a and 1208b that are generally parallel to a long dimension of the stent and second portions 1210a and 1210b. First portions 1208a and 1208b can each be connected to opposite ends of second portions 1210a and 1210b to form the generally ovular cross-sectional shape. In some embodiments, first portions 1208a and 1208b can comprise preloaded bend regions that are biased toward a lumen of the stent (see FIG. 12B). The preloaded bend regions can be convex towards the lumen according to some aspects of the present technology. In some embodiments, the preloaded bend regions of first portions 1208a and 1208b are concave to the lumen, as shown in FIG. 12D. A radius of curvature of one or more portions can be adjusted based on a desired cross-sectional shape of a stent. For example, FIG. 12E depicts a stent 1200 with first portions 1208a and 1208b and second portions 1210a and 1210b that each have a radius of curvature that is greater than a radius of curvature of the stents depicted in FIGS. 12A-12C. As shown in FIG. 12C, in some embodiments, first portions 1208a and 1208b and second portions 1210a and 1210b can have preloaded bend regions biased towards the lumen of the stent 1200. In some embodiments, second portions 1210a and 1210b can have preloaded bend regions biased towards the lumen of the stent 1200 and first portions 1208a and 1208b can have preloaded bend regions biased away from the lumen of the stent 1200 (see FIG. 12F).

[0287] According to some embodiments of the present technology, a stent 1300 can be configured to include one or more torsion springs to facilitate a change in cross-sectional shape of the stent 1300 in response to a change in blood pressure, as depicted in FIGS. 13A and 13B. A torsion spring 1304 can have at least end portion 1306 positioned proximate to a first portion and/or a second portion of the stent 1300. For example, torsion springs 1304 are positioned proximate to the first portions of the stent 1300 corresponding to bend regions B and D in FIG. 13A. In some embodiments, an intermediate portion 1308 of the torsion spring 1304 can be configured to receive a force when an arterial wall exerts a force on the stent 1300 during systole. The force can be transferred from the intermediate portion 1308 to the end portion 1306 and the end portion 1306 can be configured to apply the force to a portion of the stent 1300 to facilitate a change in cross-sectional shape of the stent 1300 in response to the force exerted by the arterial wall. For example, the torsion springs 1304 proximate to bend regions B and D in FIG. 13A can facilitate second portions moving away from one another along a short dimension of the stent during systole. Torsion springs 1304 can be positioned along a length of a stent 1300 as depicted in FIG. 13B.

[0288] A stent in accordance with several embodiments of the present technology can include one or more supports within a lumen of the stent. For example, FIG. 14A shows an end view of a stent 1400 with a first support 1402a proximate to one first portion of the stent corresponding to bend region A and a second support 1402b proximate to another first portion of the stent corresponding to bend region C. As depicted in FIG. 14A, in some embodiments a first support 1402a can be configured to engage a second support 1402b to prevent a short dimension of the stent 1400 from decreasing below a minimum distance. According to some embodiments, for example in FIG. 14B, a stent can comprise first supports 1402a proximate one second portion of the stent corresponding to bend region D and a second support 1402b proximate another second portion of the stent corresponding to bend region B. The first and second supports 1402a and 1402b can be configured to extend into the lumen of the stent 1400. In some embodiments, a stent 1400 can comprise supports 1402a and 1402b proximate first portions of the stent and supports 1402c and 1402d proximate second portions of the stent, as shown in FIG. 14C. According to some embodiments, first and second supports 1402a and 1402b can comprise a first end portion attached to the stent and a second end portion spaced apart from an opposing portion of the stent, as depicted in FIG. 14D. FIG. 14E shows an axial cross-sectional view of a stent 1400 with C-shaped first and second supports 1402a and 1402b positioned proximate to second portions of the stent 1400. The first and second supports 1402a and 1402b can include a projection 1404 positioned at an apex of the support configured to attach to the stent 1400. The projection 1404 can permit a radius of curvature of bend regions B and D of the stent 1400 to increase in response to forces exerted by the arterial wall, while the first and second supports 1402a and 1402b prevent a short dimension of the stent from decreasing below a minimum distance.

[0289] According to some embodiments, for example as shown in FIGS. 15A-15D, a stent 1500 can comprise end portions 15B and 15D with one cross-sectional shape and an intermediate portion 15C with another cross-sectional shape. For example, as shown in FIGS. 15B and 15D, the end portions can comprise a generally ovular cross-sectional shape while the intermediate portion can comprise a generally hourglass cross-sectional shape. In some embodiments, one or more portions of a stent can comprise one cross-sectional shape and one or more remaining portions can comprise another cross-sectional shape. Alternatively, or in addition, all portions of a stent can comprise the same cross-sectional shape and/or all portions of a stent can comprise different cross-sectional shapes.

[0290] The present technology relates to devices, systems, and methods for treating blood vessels. In particular, the present technology relates to devices, systems, and methods for treating arteries. In some embodiments, for example, the devices of the present technology are configured to increase aortic compliance. A device of the present technology is an expandable structure 1600, for example as shown in FIG. 16. The expandable structure 1600 can be configured to have a low-profile state for delivery of the device to a treatment site within an artery and/or an expanded state corresponding to a device that has been deployed within an artery. The expandable structure 1600 can comprise a first end portion 1600a, a second end portion 1600b, an intermediate portion, and a length extending between the first and second end portions 1600a, 1600b along a longitudinal axis L (see FIG. 16) of the expandable structure 1600. According to some embodiments, the expandable structure 1600 has a non-circular cross-sectional shape.

[0291] A device of the present technology can comprise an expandable structure 1600 comprising a plurality of strut regions 1602 extending circumferentially about the expandable structure 1600. Each strut region 1602 can comprise a plurality of struts 1604 and a plurality of apices 1608. In some embodiments, the longitudinal struts 1606 can extend between adjacent strut regions 1602. A lumen 1612 of the expandable structure 1600 can be defined by the struts 1604. In some embodiments, the strut regions 1602 can comprise continuous circumferential rings as depicted in FIG. 16. The struts 1604 of a strut region 1602 can be connected at apices 1608 such that the struts 1604 are disposed in a zig-zag pattern to facilitate radial compression and expansion of the expandable structure 1600. The struts 1604 of a strut region 1602 can be connected in a pattern to enhance longitudinal flexibility of the expandable structure 1600. The stent may have radiopaque markers positioned at the first end portion, at the second end portions, and/or therebetween, as shown in FIG. 16. Radiopaque markers 1610 can be positioned on the expandable structure 1600 to facilitate visualization of the device during delivery. For example, the expandable structure 1600 can include radiopaque markers located on anterior and posterior portions of the stent to visualize the device with a direct anterior-posterior fluoroscopy view.

[0292] According to some embodiments, for example as shown in FIGS. 17A-17D, the expandable structure can have a non-circular cross-sectional shape. The cross-sectional shape can have a long dimension 1702 and a short dimension 1704. In some embodiments, the short dimension 1704 can be between about 6 mm and 12 mm and the long dimension 1702 can be between about 15 mm and 40 mm. The non-circular cross-sectional shape can have parallel major walls as shown in FIG. 17A, slightly curved walls as shown in FIG. 17B, a generally oval shape as shown in FIG. 17C, a generally rhomboidal shape as shown in FIG. 17D, or a variation of these shapes. The cross-sectional shape of the expandable structure 1600 can be configured such that a wall of an artery conforming to the cross-sectional shape of the expandable structure 1600 has the same cross-sectional shape as the expandable structure 1600. In some embodiments, the cross-sectional shape of the expandable structure 1600 can be configured to flatten a cross-sectional shape of an artery in an anterior-posterior direction, a lateral direction, and/or at an oblique angle. An angle can be selected to minimize any impact on surrounding organs, structures, and/or branch vessels. In some embodiments, the angle varies over a length of the stent. In some embodiments, an end portion of the expandable structure 1600 comprises a generally circular cross-sectional shape and an intermediate portion of the stent between the end portions comprises a generally non-circular cross-sectional shape, as shown in FIG. 16. A generally circular cross-sectional shape of end portions of the expandable structure 1600 can facilitate a smooth transition in cross-sectional shape between a portion of an artery conforming to the expandable structure 1600 and a portion of the artery without the expandable structure 1600. Additionally, or alternatively, a stiffness of the end portions of the expandable structure 1600 can be less than a stiffness of the intermediate portion of the expandable structure 1600 to facilitate a smooth transition between various portions of the artery.

[0293] A device of the present technology can be configured to be positioned at a treatment site within a lumen of an artery, such as an aorta. An expandable structure 1600 of the device can comprise a low-profile state for delivery of the device to the treatment site and/or an expanded state with a non-circular cross-sectional shape for maintaining a cross-sectional shape of the artery at the treatment site. In the expanded state, the expandable structure 1600 can be configured to be positioned in apposition with an arterial wall at the treatment site. Under diastolic pressure, the expandable structure 1600 can cause the arterial wall to conform to the non-circular cross-sectional shape of the expandable structure 1600. A cross-sectional area based on the non-circular cross-sectional shape of the artery can be less than a cross-sectional area of a circular cross-sectional shape of the artery. For example, the expandable structure 1600 can comprise a long dimension and a short dimension, and the expandable structure 1600 can comprise first portions at either end of the long dimension and second portions at either end of the short dimension. When positioned within the artery in the expanded state, the expandable structure 1600 can cause a radius of curvature of portions of the arterial wall proximate to the second portions of the expandable structure 1600 to increase. By decreasing the cross-sectional area of the artery during diastole, the artery can undergo a greater change in volume throughout a cardiac cycle. Reducing the cross-sectional area of the artery can thereby increasing a compliance of the arterial system without stretching the arterial wall. Such increase in compliance can be advantageous in arteries with reduced capacity to stretch (e.g., arteries with calcification).

[0294] During systole, blood pressure within an artery can increase and cause the artery to deform. As the volume and pressure of an artery increases during systole, the artery can exert forces on second portions of the expandable structure 1600. In response to the exerted forces, opposing second portions of the expandable structure 1600 can be configured to move toward each other and opposing first portions of the expandable structure 1600 can be configured to move away from each other. As a result, the expandable structure 1600 and artery can assume a second cross-sectional shape and a second cross-sectional area. In some embodiments, the second cross-sectional shape is generally circular, and the second cross-sectional area is generally greater than a cross-sectional area of the first cross-sectional shape. The change in cross-sectional shape can thereby absorb and reduce energy transmitted to the arterial system from the left ventricle during systole. In some embodiments, a circumference of the artery and/or the expandable structure 1600 does not change during systole.

[0295] In some embodiments, it may be advantageous for the expandable structure 1600 to be configured to assume a second cross-sectional shape different from a first cross-sectional shape at a predetermined pressure or range of pressures. For example, a device configured to be placed in an aorta can be configured to expand at an aortic pressure between diastolic and systolic pressure to increase the compliance of the aorta. The expandable structure 1600 can be configured to deform between an aortic pressure of about 60 and about 150 mmHg. In some embodiments, the expandable structure 1600 can be configured to deform between an aortic pressure of about 90 and about 120 mmHg.

[0296] According to some embodiments, the device is configured to be position in a portion of the aorta such as the ascending aorta, the aortic arch, the descending thoracic aorta, the abdominal aorta, or even the iliac arteries. One or more devices can be deployed in multiple sections of the aorta. A size, shape, or taper of the device can be determined based on the portion of the aorta that the device is configured to be positioned within. During deployment of the device, it may be advantageous to include a distal filter to capture emboli. In some embodiments, the expandable structure 1600 of the device includes long struts to permit fluid flow to a branching artery such as a celiac artery, a renal artery, a mesenteric artery, a vertebral artery, a brachiocephalic artery, a carotid artery, and/or a subclavian artery.

[0297] According to some embodiments of the present technology, an expandable structure is configured to maintain a non-circular cross-sectional shape of an artery during diastole and expand to assume a circular cross-sectional shape during systole. In some embodiments, the expandable structure can have a non-circumferential design. Alternative, non-circumferential cross-sectional shapes are shown in FIGS. 18A-18E. The expandable structure can comprise a C-shaped cross-sectional shape 1800 and 1802, an hourglass cross-sectional shape 1804, a dog-bone cross-sectional shape 1806 and/or a cross-sectional shape comprised of multiple round strut regions 1808. In some embodiments, an expandable structure 1900 can have multiple curved sections 1902 configured to engage an arterial wall and one or more support struts 1904 configured to maintain a distance between the curved sections 1902, as shown in FIG. 19.

[0298] In some embodiments, an expandable structure may be formed by laser-cutting a desired pattern into a tubular sheet of material. In certain embodiments, the expandable structure may be initially formed as a flat sheet of material having a pattern of struts. The struts may be formed by depositing a thin film on a flat surface in the desired pattern, or by laser-cutting a desired pattern into the flat sheet of material. The flat pattern may then be curled up into a generally tube-like shape such that the longitudinal edges of the flat pattern are positioned adjacent to or in contact with one another. The longitudinal edges can be joined (e.g., via laser welding) along all or a portion of their respective lengths. In some embodiments, the struts may be formed by depositing a thin film on the surface of a tubular frame in a desired pattern (e.g., via thin film deposition, vapor deposition, or combinations thereof). As depicted in FIGS. 20A-20C, in some embodiments an expandable structure can comprise strut regions 2000 formed of a single, continuous wire. The strut regions 2000 can comprise a plurality of struts and a plurality of apices 2002 and 2004. Apices of one strut region 2000 can be connected to apices of another adjacent strut region 2000 (e.g., via laser welding) to form an expandable structure comprising multiple strut regions 2000.

[0299] In some embodiments, it may be advantageous to for an expandable structure to be configured to remain in direct contact with a portion of an arterial wall throughout a full cardiac cycle. To maximize contact of an expandable structure with an arterial wall throughout the cardiac cycle, in some embodiments the expandable structure has resilient bend regions configured to expand under systolic blood pressure such that a cross-sectional area of the expandable structure changes throughout the expansion and compression of a circumference of the stent is minimized (see FIGS. 21A and 21B). According to some embodiments of the present technology, an expandable structure 2100 can have a first cross-sectional area associated with a first, non-circular cross-sectional shape of the expandable structure 2100 (see FIG. 21A) and a second cross-sectional area associated with a second, expanded cross-sectional shape (see FIG. 21B). The second cross-sectional shape can be configured to maximize contact with an arterial wall throughout a cardiac cycle.

[0300] As shown in FIGS. 21A and 21B, an expandable structure 2100 can have a generally rhomboidal cross-sectional shape with resilient bend regions A at either side of a short dimension of the cross-sectional shape and/or either side of a long dimension of the cross-sectional shape. Generally straight regions B can extend between neighboring bend regions A. A stiffness of a straight and/or bend region can be based on a width, a thickness, a length, and/or a material property of struts of the region. For example, the generally straight regions B can be configured to be stiffer than the generally bent regions A by using wider, thicker, and/or shorter struts. The generally bent regions A can be configured to be less stiff than the generally straight regions B by using, less wide, thinner, and/or longer struts. A material the struts are formed of can be selected based on a desired stiffness of the portions. Based on relative stiffnesses of the bent and straight regions A and B, the bent regions A can bend under systolic pressure in response to forces exerted on the expandable structure 2100 by the arterial wall. A pattern of strut regions can be selected to prevent crack formation at the bent regions A.

[0301] According to some aspects of the present technology, a flexible delivery catheter and/or catheter system can be used to deliver the device to an artery. The delivery catheter can be inserted into a patient's femoral artery, carotid artery, and/or any other vessel suitable for percutaneous or vascular surgical techniques. In some embodiments, the delivery catheter can include a guidewire lumen and can be configured to be advanced over a guidewire. The delivery catheter can have a tapered distal end to mitigate traumatic injury to a vessel from advancement of the catheter. An expandable structure of a device of the present technology can be compressed to assume a low-profile state by a cover sleeve. In some embodiments, the cover sleeve can be withdrawn to allow the expandable structure to expand from the low-profile state to the expanded state. The cover sleeve can be advanced over the stent after having been previously withdrawn to compress the expandable structure to the low-profile state for repositioning and/or retrieval.

[0302] In any of the embodiments detailed herein, the device structure may be self-expanding. A self-expanding device can be formed of a shape memory alloy such as nitinol, for example. In some embodiments, the device can be balloon-expandable and formed of a stainless-steel alloy, a cobalt-chromium alloy, and/or other similar materials. Balloon catheters for expanding balloon-expandable devices typically have a circular volume when inflated. In some embodiments, it may be advantageous to configure a balloon catheter comprising a non-circular volume when inflated to maintain a corresponding non-circular cross-sectional shape of the expandable structure of the device. FIGS. 22A and 22B show example balloons configured for use in a balloon catheter to expand a device with a non-circular cross-sectional shape. For example, as depicted in FIG. 22A, a balloon comprising an ovular inflated volume can comprise a plurality of tubular balloons 2202 joined by a balloon wall 2200 surrounding the plurality of tubular balloons 2202. A balloon with an ovular inflated volume can comprise a balloon wall 2200 surrounding a plurality of chambers 2104 separated by chamber walls 2106.

[0303] In some embodiments, a device in accordance with the present technology may be coated with an anti-proliferative and/or an anti-thrombotic coating to prevent thrombosis of the treatment site and/or a healing response that increases a stiffness of the artery being treated. The device can include a coating, surface texture, and/or covering member disposed on a radially outer surface and/or a radially inner surface of the expandable structure. For example, a covering member comprising polyester fibers can be disposed on a radially outer surface of the expandable structure to promote ingrowth of arterial wall tissue into the expandable structure. Ingrowth can be advantageous to mitigate device fatigue and/or aneurysm formation in the arterial wall. Additionally, the device can be configured to promote ingrowth such that the device is incorporated into arterial and configured to reduce the stress experienced by the arterial wall throughout the cardiac cycle. In some embodiments, the device comprises a plurality of cells in the expandable structure to permit fluid flow in branch vessels. In some embodiments, a device can be sized to be slightly larger than an artery of the treatment site such that one or more portions of an arterial wall are in contact with the device for a desired portion of the cardiac cycle.