Aortic pressure loss reduction apparatus and methods

Abstract

Apparatus and methods are described including an aortic pressure-loss-reduction device (20) configured to be delivered to and implanted inside an ascending aorta of a subject using a delivery device. The aortic pressure-loss-reduction device (20) includes a frame and a layer of material (54) coupled to at least a portion of the frame, the material layer configured to impede blood flow therethrough. A retrieval element (240), configured to facilitate retrieval of the aortic pressure-loss-reduction device (20) from the ascending aorta back into the delivery device, is coupled to an outside of the aortic pressure-loss-reduction device (20) and is configured to be disposed externally to the aortic pressure-loss-reduction device (20).

Description

[0001] AORTIC PRESSURE LOSS REDUCTION APPARATUS AND METHODS

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application claims priority from US Provisional Application 63 / 709,595 to Karavany et al., filed October 21, 2024, entitled "Aortic pressure loss reduction apparatus and method," which is incorporated herein by reference.

[0004] TECHNICAL FIELD

[0005] Some applications of the present disclosure generally relate to medical apparatus. Specifically, some applications of the present disclosure relate to an aortic pressure-loss-reduction device and methods of use thereof.

[0006] BACKGROUND

[0007] Aortic valve stenosis is a common disease in which calcification of the cusps of the aortic valve causes the flexibility of the valve to be compromised and the open valve area to diminish. Once aortic valve stenosis develops, due to the reduction in the aortic valve diameter, blood flow is compromised. Aortic valve stenosis often progresses to heart failure and other life-threatening conditions.

[0008] SUMMARY

[0009] In accordance with some applications of the present disclosure, an aortic pressure-loss-reduction device is implanted in a subject's ascending aorta. The device typically includes a frame and a material that is configured to impede blood flow therethrough coupled to at least a portion of the frame. Typically, in a non-constrained configuration of the device, the frame defines (a) an upstream anchor portion configured to radially expand against the inner wall of the ascending aorta, such as to anchor an upstream end of the aortic pressure-loss-reduction device to the subject's ascending aorta, (b) an intermediate portion that defines a conduit therethrough, such that blood is configured to flow through the device via the conduit, at least a portion of the conduit diverging, such that a downstream end of the diverging portion has a greater cross-sectional area than an upstream end of the diverging portion, and (c) a downstream anchor portion configured to radially expand against the inner wall of the ascending aorta, such as to anchor the downstream end of the aortic pressure-loss-reduction device to the subject's ascending aorta. In accordance with some applications of the present disclosure, the aortic pressure-loss-reduction device is delivered to the ascending aorta using a delivery device, while the aortic pressure-loss-reduction device is in a radially-constrained configuration within the delivery device. When implanted within the subject’s ascending aorta, the aortic pressure-loss-reduction device assumes the non-radially-constrained configuration defining the upstream anchor portion, the intermediate portion, and the downstream anchor portion. For some applications, the frame of the aortic-pressure-loss-reduction device comprises a braided stent. For some applications, the material layer that is coupled to the braided stent and impedes blood flow therethrough is arranged in a set of folds that comprise excess material in the non-radially-constrained configuration of the aortic-pressure-loss-reduction device. The folds are configured to unfold to thereby provide additional material to allow the aortic-pressure-loss-reduction device to elongate while assuming its radially-constrained configuration within the delivery device.

[0010] Additionally, or alternatively, in accordance with some applications, the aortic pressure-loss-reduction device includes a retrieval element coupled to the aortic pressure-loss-reduction device and configured to facilitate retrieval of the device from inside the subject's ascending aorta. The retrieval element is coupled to the outside of the aortic pressure-loss-reduction device and is configured to be disposed externally to the aortic pressure-loss-reduction device, typically such that upon the device being implanted within the subject’s ascending aorta, the retrieval element is disposed within a region between the conduit (defined by the intermediate portion) and the inner wall of the subject’s aorta. By being disposed outside an outer surface of the aortic pressure-loss-reduction device, the retrieval element generally does not interfere with operation of the device. For example, the retrieval element does not occupy space within the conduit through which the blood flows, thereby not disrupting blood flow through the conduit. Additionally, since blood flow is generally directed through the aortic pressure-loss-reduction device and impeded in the region that is between the outer surface of the device and the inner wall of the aorta, the retrieval element being positioned in that region generally does not interfere with functioning of the aorta, subsequent to aortic pressure-loss-reduction device being deployed.

[0011] There is therefore provided, in accordance with some applications of the present disclosure, apparatus for use with a delivery device including:

[0012] an aortic pressure-loss-reduction device configured to be delivered to and implanted inside an ascending aorta of a subject using the delivery device, the aortic pressure-loss-reduction device including:

[0013] a frame that is configured, in a non-constrained configuration thereof, to define: an upstream anchor portion configured to radially expand against an inner wall of the subject's ascending aorta, such as to anchor an upstream end of the aortic pressure-loss- reduction device to the subject's ascending aorta;

[0014] an intermediate portion configured to define a conduit therethrough, such that blood is configured to flow through the device via the conduit, at least a portion of the conduit diverging, such that a downstream end of the diverging portion has a greater cross-sectional area than an upstream end of the diverging portion;

[0015] a downstream anchor portion configured to radially expand against the inner wall of the subject's ascending aorta, such as to anchor a downstream end of the aortic pressure- loss-reduction device to the subject's ascending aorta;

[0016] at least one layer of material coupled to at least a portion of the frame, the material layer configured to impede blood flow therethrough; and

[0017] a retrieval element configured to facilitate retrieval of the aortic pressure-loss-reduction device from the ascending aorta back into the delivery device, the retrieval element being coupled to an outside of the aortic pressure-loss-reduction device and configured to be disposed externally to the aortic pressure-loss-reduction device.

[0018] In some embodiments, the retrieval element is coupled to the outside of the aortic pressure-loss-reduction device and configured to be disposed externally to the aortic pressure-loss-reduction device, such that upon aortic pressure-loss-reduction device being implanted within the subject’s ascending aorta, the retrieval element is disposed within a region between the conduit and the inner wall of the subject’s aorta.

[0019] In some embodiments, the retrieval element is coupled to the outside of the aortic pressure-loss-reduction device at a downstream end of the aortic pressure-loss-reduction device.

[0020] In some embodiments, the retrieval element is coupled to the outside of the aortic pressure-loss-reduction device at a downstream end of the intermediate portion of the frame.

[0021] In some embodiments, the retrieval element includes a metallic spiral retrieval element. In some embodiments, the retrieval element includes a metallic braided retrieval element. In some embodiments, the retrieval element is coupled to the aortic pressure-loss-reduction device by suturing.

[0022] In some embodiments, the retrieval element is coupled to the aortic pressure-loss-reduction device by laser welding. In some embodiments, the retrieval element includes a free end that is not coupled to the aortic pressure-loss-reduction device, and that is configured to be pulled to cause crimping of the aortic pressure-loss-reduction device.

[0023] There is further provided, in accordance with some embodiments of the present invention, apparatus for use with a delivery device including:

[0024] an aortic pressure-loss-reduction device configured to be delivered to an ascending aorta of a subject using the delivery device, while the aortic pressure-loss-reduction device is in a radially-constrained configuration within the delivery device, the aortic pressure-loss-reduction device being configured to become implanted within the subject’s ascending aorta in a non-radially-constrained configuration, the aortic-pressure-loss-reduction device including:

[0025] a braided stent that is configured, in the non-radially-constrained configuration of the aortic-pressure-loss-reduction device, to define:

[0026] an upstream anchor portion configured to radially expand against an inner wall of the subject's ascending aorta, such as to anchor an upstream end of the aortic pressure-loss- reduction device to the subject's ascending aorta;

[0027] an intermediate portion configured to define a conduit therethrough, such that blood is configured to flow through the device via the conduit, at least a portion of the conduit diverging, such that a downstream end of the diverging portion has a greater cross-sectional area than an upstream end of the diverging portion;

[0028] a downstream anchor portion configured to radially expand against the inner wall of the subject's ascending aorta, such as to anchor a downstream end of the aortic pressure- loss-reduction device to the subject's ascending aorta;

[0029] at least one layer of material coupled to at least a portion of the braided stent, the material layer configured to impede blood flow therethrough, the material layer being arranged in a set of folds that include excess material in the non-radially-constrained configuration of the aortic-pressure-loss-reduction device, the folds being configured to unfold to thereby provide additional material to allow the aortic-pressure-loss-reduction device to assume its radially-constrained configuration.

[0030] In some embodiments, lengths of each of the folds at the intermediate portion of the braided stent are between 1 and 8 mm.

[0031] In some embodiments, the covering material covers an inside of at least a portion of the braided stent. In some embodiments, at least a portion of the braided stent is embedded within the covering material.

[0032] In some embodiments, the material layer covers an inside of the intermediate portion of the braided stent and an outside of the upstream anchor portion of the braided stent.

[0033] In some embodiments, at least a portion of the material layer covers an inside of the intermediate portion of the braided stent, and the folds in the portion of the material layer that covers the inside of the intermediate portion of the braided stent are folded in a direction corresponding to a direction of systolic blood flow.

[0034] There is further provided, in accordance with some embodiments of the present disclosure, apparatus including:

[0035] an aortic pressure-loss-reduction device configured to be implanted inside an ascending aorta of a subject, the aortic pressure-loss-reduction device including:

[0036] a frame that is configured, in a non-constrained configuration thereof, to define: an upstream anchor portion configured to radially expand against an inner wall of a subject's ascending aorta, such as to anchor an upstream end of the aortic pressure-loss-reduction device to the subject's ascending aorta;

[0037] an intermediate portion configured to define a conduit therethrough, such that blood is configured to flow through the device via the conduit, at least a portion of the conduit diverging, such that a downstream end of the diverging portion has a greater cross-sectional area than an upstream end of the diverging portion;

[0038] a downstream anchor portion configured to radially expand against an inner wall of a subject's ascending aorta, such as to anchor a downstream end of the aortic pressure-loss-reduction device to the subject's ascending aorta;

[0039] a set of undulating struts disposed between the upstream anchor portion and the intermediate portion, the undulating struts being configured such that, in response to a diameter of the upstream anchor portion changing by an absolute amount, an absolute change in a diameter of the upstream end of the intermediate portion is less than the absolute amount by which the diameter of the upstream anchor portion changes; and

[0040] a material layer coupled to at least a portion of the frame, the material layer configured to impede blood flow therethrough.

[0041] The present disclosure will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figs. 1A and IB are schematic illustrations of an implantable pressure-loss-reduction device configured to be deployed inside a subject's aorta, in accordance with some applications of the present disclosure;

[0043] Figs. 2A, 2B, and 2C are schematic illustrations of frames of a pressure-loss-reduction device configured to assume a curved configuration upon being deployed within a subject's ascending aorta, in accordance with some applications of the present disclosure;

[0044] Figs. 3A and 3B are schematic illustrations of frames of a pressure-loss-reduction device configured such that, in the event that the diameter of an upstream anchor of the device changes, the diameter of the upstream end of a conduit of the device does not change by the same amount, in accordance with some applications of the present disclosure;

[0045] Figs. 4A and 4B are schematic illustrations of frames of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, the device including anchor extensions on one or more anchors of the device, in accordance with some applications of the present disclosure;

[0046] Figs. 5A and 5B are schematic illustrations of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, the device including anchor extensions on one or more anchors of the device, in accordance with additional applications of the present disclosure;

[0047] Figs. 5C and 5D are schematic illustrations of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, the device including anchor extensions on one or more anchors of the device, in accordance with additional applications of the present disclosure;

[0048] Fig. 5E is a schematic illustration of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, the device including anchor extensions on one or more anchors of the device, in accordance with additional applications of the present disclosure;

[0049] Figs. 5F and 5G are schematic illustrations of a frame of a pressure-loss-reduction device and a pressure-loss-reduction device for implanting inside a subject's ascending aorta, in accordance with some applications of the present disclosure;

[0050] Fig. 5H is a schematic illustration of a frame of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, the frame including anchor extensions on one or more anchors of the device, in accordance with some applications of the present disclosure;

[0051] Figs. 6A, 6B, 6C and 6D are schematic illustrations of a general outline showing a contour of a frame of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, including anchor extensions on one or more anchors of the device, in accordance with some applications of the present disclosure;

[0052] Figs. 7A, 7B, 7C, 7D, and 7E are schematic illustrations of optional configurations of a pressure-loss-reduction device for implanting inside a subject's ascending aorta, in accordance with additional applications of the present disclosure;

[0053] Fig. 8 is a schematic illustration of pressure-reduction-loss device that includes a retrieval element configured for facilitating retrieval of the device from inside the subject's ascending aorta, in accordance with some applications of the present disclosure; and

[0054] Figs. 9A and 9B are schematic illustrations of a pressure-loss-reduction device including a stent graft having a material layer which is shaped to define a plurality of folds, in accordance with some applications of the present disclosure.

[0055] DETAILED DESCRIPTION OF EMBODIMENTS

[0056] Reference is made to Figs. 1 A and IB, which are schematic illustrations of an implantable pressure-loss-reduction device 20 deployed inside a subject's ascending aorta 22, in accordance with some applications of the present disclosure. Fig. 1A shows the device deployed inside the ascending aorta, and Fig. IB shows a slice view of the device in a non-constrained configuration (i.e., in the absence of any external force acting upon the device). As shown, device 20 defines an intermediate portion 23 that has an inner surface 24 that defines a conduit 26 through the device, from the upstream end of the device to the downstream end of the device. At least a portion of the conduit diverges in a direction from an upstream end 30 of the conduit to a downstream end 34 of the conduit, such that the cross-sectional area of the conduit at the downstream end is greater than the cross-sectional area of the conduit at the upstream end. In addition, the device is configured such that at least upon being placed inside the subject's ascending aorta, the conduit is curved (i.e., the conduit defines a curved longitudinal axis), such as to conform at least partially to the curvature of the ascending aorta.

[0057] Typically, the device is configured such that in its non-constrained configuration at least a portion of the conduit 26 diverges, but the conduit 26 is not curved, as shown in Fig. IB. For such applications, the intermediate portion of the device is typically configured to be flexible, such that upon being deployed within the ascending aorta, the intermediate portion of the device becomes curved such as to conform at least partially to the curvature of the ascending aorta. For some applications, the device is configured such that even in its non-constrained configuration, at least a portion of conduit 26 diverges, and conduit 26 is also curved. For some applications, the device is configured such that in its non-constrained configuration, a portion of conduit 26 diverges, and is not curved, but rather is disposed at an angle with respect to an upstream anchor 33 of the device (i.e., such that a longitudinal axis of the conduit is disposed at an angle with respect to the longitudinal axis of the upstream anchor).

[0058] Pressure-loss-reduction device 20 is typically placed in the ascending aorta of a subject suffering from aortic valve stenosis, in the vicinity of the stenosed aortic valve 27 (e.g., such that the upstream end of the conduit is downstream of the aortic valve, and within 25 mm from the aortic valve tip when the valve is in an open configuration, during systole). The blood exiting the subject's left ventricle, during systole, is directed into conduit 26. The divergence of the conduit is configured to reduce pressure loss of blood flowing through the conduit, relative to the loss of pressure of the blood flowing through the longitudinal portion of the blood vessel in the absence of the device. The conduit reduces blood pressure loss by reducing the area of flow separation. During diastole, blood flows back toward coronary arteries 38 via conduit 26.

[0059] The device is typically deployed within a longitudinal portion of the aorta, such that blood flow through the longitudinal portion of the aorta, via any flow path other than through the conduit, whether in the antegrade or retrograde direction, is less than 20 percent (e.g., less than 10 percent, or less than 5 percent) of the total blood flow through the longitudinal portion of the blood vessel. (In the present application, when used with reference to blood flow, the term "antegrade" refers to blood flowing in the forward directions, and the term "retrograde" refers to blood flowing in a backward direction.) Typically, by directing the blood to flow in the above-described manner, loss of pressure and energy of the blood flow exiting the left ventricle into the ascending aorta is reduced relative to the loss of pressure and energy of the blood flow in the absence of the device. Thus, placement of device 20 in the subject's ascending aorta may decrease the subject's left ventricular pressure, reduce afterload, and / or improve the subject's cardiac output. For some applications, regulating the blood flow from the aortic valve in the above-described manner may postpone or stop the degradation process leading to further aortic valve stenosis. An unhealthy flow regime in the ascending aorta can cause sequential deposits of thrombi on the valve surface that can cause further valve thickening, deformation and calcification leading to severe stenosis. Device 20, by changing the flow regime, may reduce the inflammatory process that causes the calcification. Thus, device 20 may decrease the degradation of the medical situation of the subject.

[0060] It is noted that, typically, device 20 does not include a prosthetic valve disposed within the conduit or at any other location within the device. The device typically performs the functions described herein, without requiring the use of a prosthetic valve of any type. Typically, the pressure-loss-reduction device includes a downstream anchor 31 at the downstream end of the device that is configured to appose the inner wall of the aorta, and to anchor the downstream end of the device with respect to the aorta by exerting outward radial pressure against the inner wall of the aorta. The device typically defines at least one downstream outer surface 32 that extends from the outside of the conduit to the downstream anchor, which is in contact with the inner wall of the blood vessel. Typically, the at least one surface extends radially outward, around the full circumference of the conduit, from the conduit to the downstream anchor.

[0061] Pressure-loss-reduction device 20 typically includes an upstream anchor 33 at the upstream end of the device that is configured to appose the inner wall of the aorta, and to anchor the upstream end of the device with respect to the aorta by exerting outward radial pressure against the inner wall of the aorta. The device typically defines one or more upstream outer surfaces 28 that surround a, upstream portion of conduit 26, and that extend at least from outside the conduit to the upstream anchor. Typically, the at least one upstream outer surface is disposed around the conduit at a longitudinal location such that at least a portion of the upstream surface is within the upstream-most 30 percent (e.g., the upstream-most 20 percent) of the length of the conduit.

[0062] Typically, upstream and downstream outer surfaces 28 and 32 are configured such that, when pressure-loss-reduction device 20 is deployed inside a longitudinal portion of the subject's aorta, the surfaces substantially impede blood flow through the longitudinal portion, via any flow path other than through conduit 26. For example, the upstream and downstream surfaces may be configured such that, when the device is deployed inside the longitudinal portion of the subject's aorta, flow via flow paths other than through conduit 26, whether in the antegrade or retrograde direction, is less than 20 percent (e.g., less than 10 percent, or less than 5 percent) of total blood flow through the longitudinal portion of the subject's aorta. Typically, the upstream and downstream surfaces are configured such that, when the device is deployed inside the longitudinal portion of the subject's aorta, there is no blood flow through the longitudinal portion of the subject's aorta via any flow path other than through the conduit defined by the inner surface of the device, whether in the antegrade or retrograde direction. For some applications, each of downstream outer surface 32 and upstream outer surface 28 is configured to impede the backflow of blood around the outside of conduit 26 as well as to impede antegrade blood flow around the outside of conduit 26. For some applications, the device includes a single one of the upstream and downstream outer surfaces, and the single surface is configured to impede both antegrade and retrograde blood flow around the outside of conduit 26. For some applications (not shown), intermediate portion 23 (which has inner surface 24 that defines conduit 26) is disposed eccentrically with respect to one or both of upstream anchor 33 and downstream anchor 31.

[0063] Typically, intermediate portion 23 (which has inner surface 24 that defines conduit 26), as well as upstream anchor 33, downstream anchor 31, and surfaces 28 and 32 are all defined by a single continuous portion of stent graft 50, that is shaped such as to define the respective components of pressure-loss-reduction device 20, as shown in Fig. IB. The stent graft material is typically formed from a combination of a metal or alloy frame 52 (e.g., a stent made of stainless steel or nitinol or cobalt chromium) and a covering layer of material 54, e.g., a fabric and / or a polymer (such as expanded polytetrafluoroethylene (ePTFE), or woven, knitted and / or braided polyester), which is typically coupled to the frame via stitching, spray coating, encapsulation, electrospinning, dip molding and / or a different technique. In accordance with some applications, a layer of the material is coupled to the inside of at least a portion of the frame, the outside of at least a portion of the frame, and / or at least a portion of the frame is embedded within a layer of the material. Material 54 is typically configured to impede blood flow therethrough, as described in further detail hereinbelow. For some applications, the frame of the stent graft material is a braided stent. For some applications, the braided stent provides flexibility to the device that facilitates insertion of the device via curved portions of the vasculature. For some applications, using a braided stent allows the device to be radially constrained to a narrower diameter than would be possible using a non-braided stent.

[0064] For some applications, material 54 is impermeable and prevents blood from flowing back toward the aortic valve during systole (and / or during diastole), outside of the conduit. Alternatively, material 54 is not impermeable, but has a permeability that is sufficiently low as to substantially prevent any blood from flowing through the longitudinal portion of the aorta, via any flow path other than through the conduit defined by the inner surface of the device, in the manner described hereinabove. For some applications, the material has permeability per unit length of less than 0.25 micrometers (i.e., between 0 and 0.25 micrometers), where the permeability per unit length is defined based upon the following equation, which is based upon Darcy's Law: k / Ax = Vfi / Ap, where k is permeability, Ax is length (in meters), V is average velocity (in meters per second), u is fluid viscosity (measured in Pascal-seconds), and AP is the pressure differential measured in Pascals).

[0065] For some applications, material 54 is structured such that there are open spaces between portions of the material. For example, the material may be arranged in a lattice structure, a braided structure, a crisscross structure, a woven structure, a cellular structure, a stitched structure, or a similar structure. Typically, even for such applications, more than 20 percent of the area of each of the surfaces is filled with material, and less than 80 percent of the area of each of the surfaces is open space between the material. Further typically, more than 50 percent, e.g., more than 80 percent, of the area of each of the surfaces is filled with material. For some applications, there are no open spaces within the surfaces (i.e., the entirety of each of the surfaces is filled with material).

[0066] For some applications, inner surface 24 that defines conduit 26 is rough. The rough surface of the conduit is configured to act as a turbulator on the boundary layer between the blood and the surface of the conduit, such as to increase adhesion, excite the boundary layer, and delay flow separation.

[0067] For some applications, by virtue of having both upstream and downstream outer surfaces, pressure-loss-reduction device 20 is configured to trap any blood that is disposed within a region 36 (Fig. 1 A) between the conduit and the inner wall of the aorta within the longitudinal portion of the aorta in which the device is placed. In this manner, the device is configured to prevent any thrombi that develop within region 36 from exiting the region and entering the subject's bloodstream.

[0068] For some applications, the device is configured to promote coagulation of blood that is disposed within region 36 between the conduit and the inner wall of the aorta within the longitudinal portion of the aorta in which the device is placed, by substantially reducing blood flow through this region relative to blood flow through this region in the absence of the device. Typically, the material that defines the upstream outer surface, the downstream outer surface and / or the inner surface is configured to prevent any thrombi that develop within the region from exiting the region and entering the subject's bloodstream. For some applications, by promoting the coagulation of blood within the region, the device causes blood entering the region to become coagulated, such that the region becomes filled with coagulated blood within a given time period of the device being placed within the aorta (e.g., within one week, one month, or three months of the device being placed within the aorta), such that the coagulated blood impedes (e.g., blocks) the flow of blood through the region.

[0069] For some applications, the blood that becomes coagulated within the region is blood that became trapped within the region immediately upon deployment of the device. Alternatively or additionally, blood enters the region subsequent to the device having been deployed, and the blood that subsequently enters the region becomes coagulated. It is noted that, even for such applications, the upstream and downstream surfaces are configured such that, even when the device is first deployed and before coagulated blood has formed inside the region, flow via flow paths other than through the conduit defined by the inner surface of the device is less than 20 percent (e.g., less than 10 percent, or less than 5 percent) of total blood flow through the longitudinal portion of the subject's aorta. For some applications, techniques are applied in order to coagulate blood that is trapped within region 36. For example, coil compaction techniques may be applied in order to cause the blood to coagulate.

[0070] Typically, when device 20 is deployed inside the subject's ascending aorta, blood is supplied to the subject's coronary arteries 38 via backflow of blood through conduit 26 during diastole, and / or via blood flowing directly from the aortic valve to the coronary arteries without passing into conduit 26 (not shown). For some applications, a portion of the blood supply to the coronary arteries is provided by antegrade blood flow from the aortic valve to the coronary arteries (e.g., during systole). Typically, most of the blood supply to the coronary arteries is via the backflow of blood through conduit 26 during diastole.

[0071] As described hereinabove, at least a portion of conduit 26 diverges in a direction from upstream end 30 of the conduit to downstream end 34 of the conduit. Due to the divergence of the portion of the conduit, the cross-sectional area of the downstream end of the diverging portion of the conduit is greater than the cross-sectional area of the upstream end of the conduit. Typically, the conduit is divergent over more than 50 percent, e.g., more than 75 percent, or more than 90 percent, of the total length of the conduit, (i.e., the diverging portion comprises more than 50 percent, e.g., more than 75 percent, or more than 90 percent, of the total length of the conduit). Further typically, the conduit is divergent over more than 50 percent, e.g., more than 75 percent, or more than 90 percent, of the total length of the device, (i.e., the diverging portion comprises more than 50 percent, e.g., more than 75 percent, or more than 90 percent, of the total length of the device). For some applications, the divergence of the conduit is at a constant angle along the length of the diverging portion of the conduit, for example, such that the diverging portion of the conduit defines a frustoconical shape. For some applications, the angle of the divergence of the conduit along the diverging portion of the conduit changes along the length of the diverging portion of the conduit. For example, the angle of the divergence may increase from the upstream end of the portion to the downstream end of the portion, such that inner surface 24 has a convex cross-section along the diverging portion of the conduit. For some applications, the diverging portion of the conduit defines a Stratford ramp shape. Typically, the upstream and downstream ends of the diverging portion of the conduit define circular cross-sections. Alternatively, the upstream and downstream ends of the diverging portion of the conduit define elliptical crosssections, polygonal cross-sections, or differently shaped cross-sections. For some applications, at each of the upstream and downstream ends of the aortic pressure-loss-reduction device, frame 52 of the device defines a folded portion 56U and 56D at the transition between the intermediate portion 23 of the device (which has inner surface 24 that defines conduit 26) and, respectively, the upstream anchor 33 and the downstream anchor 31. For example, as shown, the frame of the device may form folded portions 56UF and 56DF that have sinusoidal (i.e., S-shaped) cross-sectional shapes.

[0072] Typically, due to folded portion 56U, along the longitudinal direction of the device, there is partial overlap between upstream anchor 33, and conduit 26. For some applications (not shown), upstream folded portion 56U is such that the upstream end of conduit 26 extends proximally beyond the upstream end of upstream anchor 33. Typically, the upstream end of upstream anchor 33 is placed within the aorta downstream of the aortic sinuses. For some applications, the upstream end of the conduit extends proximally beyond the upstream end of upstream anchor, such that the upstream end of the conduit is closer to the aortic valve than the upstream end of the upstream anchor. For some applications (not shown), the upstream anchor extends distally such that it overlaps with most of (e.g., all of) conduit 26. Typically, due to folded portion 56D, along the longitudinal direction of the device, there is partial overlap between downstream anchor 31, and conduit 26. For some applications (not shown), downstream folded portion 56D is such that the downstream end of conduit 26 extends distally beyond the downstream end of downstream anchor 31. For some applications (not shown), downstream anchor 31 extends proximally such that it overlaps with most of (e.g., all of) conduit 26.

[0073] For some applications, the folded portions enhance sealing between the anchors of the device and the aorta (relative to if the device did not include folding portions, ceteris paribus), by enhancing the radial force that the anchors of the device exert upon the inner wall of the aorta. For example, the folded portions may enhance the radial force since, at the folded portions there are effectively two or more layers applying a radial force to the inner wall of the aorta, and / or due to the shape of the fold itself adding to the outward radial force that is exerted upon the inner wall of the aorta. Moreover, at the folded portions there is typically a portion of frame 52 that extends in the radial direction, or at least extends at an angle that includes a strong radial component. Typically, this portion of the frame enhances the radial force that the anchors of the device exert upon the inner wall of the aorta, in a similar manner to how a spoke of a wheel enhances the radial strength of the wheel.

[0074] For some applications, due to the both the upstream and downstream ends of device 20 including folded portions, intermediate portion 23 of the device, which defines conduit 26, is (a) on the one hand, longitudinally fixed with respect to the aorta by the upstream and downstream portion exerting radial forces against the inner wall of the aorta (the radial forces being reinforced by the folded portions), but (b) on the other hand, able to adjust the angle that the longitudinal axis of the intermediate portion makes with the longitudinal axis of the upstream and downstream portions, by the folded portions acting as hinges about which the intermediate portion can flex. In this manner, the intermediate portion of the device is able to adjust its angular position with respect to the aorta, and / or be disposed at an angle with respect to the local longitudinal axis of the aorta at the longitudinal locations at which the upstream and / or downstream portions are fixed to the aorta.

[0075] For some applications, by virtue of the intermediate portion being separated from the upstream and downstream portions, the length of the intermediate portion typically does not change even if the distance between the upstream and downstream portion changes (e.g., due to movement of the wall of the aorta). For some applications, frame 52 is configured such that in the event that the diameter of the upstream anchor changes, the diameter of conduit 26 does not change by the same amount, as provided, for example, by the configuration described in further detail hereinbelow with reference to Figs. 2A-B.

[0076] Typically, upstream folded portion 56U of frame 52 with material 54 coupled thereto acts as upstream outer surface 28, as described hereinabove, and is configured to impede antegrade and / or retrograde blood flow around the outside of the upstream end of the conduit. Further typically, downstream folded portion 56D of frame 52 with material 54 coupled thereto acts as downstream outer surface 32, as described hereinabove, and is configured to impede antegrade and / or retrograde blood flow around the outside of the downstream end of the conduit. It is noted that folded portion 56D is typically configured such that at any given radial location along the folded portion, there is only one layer of the stent graft material (a layer of stent graft material typically including a frame and a material layer, as described hereinabove) impeding blood flow around the outside of the downstream end of the conduit. Similarly, folded portion 56U is typically configured such that at any given radial location along the folded portion, there is only one layer of the stent graft material impeding blood flow around the outside of the upstream end of the conduit.

[0077] Reference is now made to Figs. 2A, 2B, and 2C, which are schematic illustrations of frames 52 of pressure-loss-reduction device 20, in accordance with some applications of the present disclosure. Each of Figs. 2A-2C shows a flattened profile of the device frame, in accordance with some applications of the present disclosure. As described hereinabove, for some applications, device 20 is formed from a single continuous portion of graft material. The graft material is typically formed from a combination of frame 52, which is typically a metal or alloy frame (e.g., a stent made of stainless steel or nitinol or cobalt chromium), and layer of material 54, e.g., a fabric and / or a polymer (such as expanded polytetrafluoroethylene (ePTFE), or woven, knitted and / or braided polyester), which is typically coupled to the inside of the frame via stitching, spray coating, encapsulation, electrospinning, dip molding and / or a different technique. In accordance with some applications, a layer of the material is coupled to the inside of at least a portion of the frame, the outside of at least a portion of the frame, and / or at least a portion of the frame is embedded within a layer of the material. The profiles shown in Figs. 2A-C depict (for illustrative purposes) how the frame of the device would appear if, prior to shape setting the frame, a longitudinal incision was to be made along the length of the frame at a given circumferential location of the frame, and the frame were to then be laid out flat upon a surface.

[0078] As shown in each of Figs. 2A-C, the frame typically comprises an upstream anchor frame portion 33F (corresponding to upstream anchor 33), a downstream anchor frame portion 3 IF (corresponding to downstream anchor 31), and intermediate frame portion 23F (corresponding to the intermediate portion of the device, inner surface 24 of which defines conduit 26). Typically, at frame portion 56UF and 56DF corresponding to folded portions 56U and 56D (i.e., between upstream anchor frame portion 33F and intermediate frame portion 23F, and between downstream anchor frame portion 3 IF and intermediate frame portion 23F), the frame defines sinusoidal struts 60. Typically, the folded portions are formed by shape setting the sinusoidal struts into the desired folded shape. For some applications, the sinusoidal struts facilitate shape setting the frame of device 20 to include folded portion 56U and 56D, such that the radius of curvature of the curve made by the folded portion is smaller than if the folded portion were to be formed solely by shape setting a straight strut. For some applications, the folded portion can thereby be longer, such as to enhance sealing with respect to the aorta that is provided by the folded portion, as described hereinabove. For some applications, allowing upstream folded portion 56U to be longer facilitates placement of the upstream end of the conduit closer to the orifice of the aortic valve, by allowing greater overlap between the conduit and the upstream anchor.

[0079] As indicated in Figs. 2A-C, typically sinusoidal struts 60 at frame portion 56UF corresponding to the upstream folded portion 56U are longer than those at frame portion 56DF corresponding to downstream folded portion 56D. For example, the ratio of the lengths of the sinusoidal struts corresponding to the upstream folded portion 56U to lengths of the sinusoidal struts corresponding to downstream folded portion 56D may be more than 5:4, or more than 3:2, or more than 2:1. Referring again to Fig. IB, the difference between the diameter of the conduit at the upstream end and the diameter of the upstream anchor, is greater than the difference between the diameter of the conduit at the upstream end and the diameter of the upstream anchor. Therefore, the struts corresponding to the upstream folded portion are longer than those corresponding to the downstream portion. Furthermore, as described hereinabove, it is typically desirable for the upstream end of the conduit to overlap with the upstream anchor, such that the upstream end of the conduit is placed as close as possible to the orifice of the aortic valve. For some applications, the sinusoidal struts corresponding to the upstream folded portion are configured to have a length that is such as to facilitate the requisite degree of overlap between the conduit and the upstream anchor.

[0080] A portion 23F of the frame that corresponds to intermediate portion 23 of pressurereduction-loss device 20 (i.e., the portion of the device that defines conduit 26) is typically configured to provide the characteristics described hereinabove. Namely, that (a) at least a portion of the conduit diverges in a direction from an upstream end of the conduit to a downstream end of the conduit, such that the cross-sectional area of the conduit at the downstream end is greater than the cross-sectional area of the conduit at the upstream end, and (b) at least upon being placed inside the subject's ascending aorta, the conduit is curved (i.e., the conduit defines a curved longitudinal axis), such as to conform at least partially to the curvature of the ascending aorta. In the examples of frame 52 as shown in Figs. 2A, 2B, and 2C, portion 23F of the frame corresponding to intermediate portion 23 is configured to provide these functionalities, but the examples shown in each of the figures differ from each other. In particular, portion 23F of the frame in the examples shown in Figs. 2A-2C is configured to be flexible, such that upon being placed within the ascending aorta, the intermediate portion of device 20 curves to conform with the shape of the ascending aorta.

[0081] With reference to Figs. 2A and 2B, for some applications, device 20 is configured to curve, such as to conform with curvature of the ascending aorta, at least partially by virtue of portion 23F of frame 52 (i.e., the portion of the frame that corresponds to intermediate portion 23 of pressure-loss-reduction device 20) being cut such that the portion defines alternating rows of struts. A density of the struts (i.e., the number of struts per unit circumference of the frame) in a first set 62 of the alternating rows of struts is greater than the density of the struts in the second set 64 of the alternating rows of struts, with the first set and second set of struts alternating with each other along the length of the portion of frame 52 corresponding to intermediate portion 23. For example, as shown in Fig. 2A, in the second set of the alternating rows of struts, there may be one strut 66 corresponding to every 4 struts 68 of the first set of the alternating rows of struts. Or, as shown in Fig. 2B, in the second set of the alternating rows of struts, there may be one strut 70 corresponding to every 6 struts 72 of the first set of the alternating rows of struts. For some applications, the struts of the second set of the alternating rows of struts are shaped differently from the struts of the first set of alternating rows of struts. For example, as shown, the struts of the second set of the alternating rows of struts may be sinusoidal, whereas the struts of the first set of alternating rows of struts may be straight. Typically, the lower strut density of the struts within the second set of alternating rows of struts, and / or the shapes of the struts within the second set of alternating rows of struts facilitates curving of intermediate portion 23F of frame 52, such as to conform with curvature of the ascending aorta, by providing flexibility to the portion of the frame. Alternatively or additionally, other techniques are used to provide the second set of the alternating rows of struts with greater flexibility than the first set of the alternating rows of struts. For example, the widths of the struts in the second set of the alternating rows of struts may be less than that of the first set of the alternating rows of struts.

[0082] For some applications (not shown), device 20 is configured in a generally similar manner to that described with reference to Figs. 2A-B, except that at locations corresponding to the second set of the alternating rows of struts, there are no struts, and the stent graft at those locations comprises only the material layer (e.g., the fabric layer), without any frame. In general, for some applications, the material layer of the stent graft is configured to cause the frame to curve in a manner that conforms with the curvature of the aorta. For example, the material layer may be shaped in a curved shape, and / or may be coupled to the frame in a manner that causes the frame to curve in a manner that conforms with the curvature of the aorta.

[0083] With reference to Fig. 2C, for some applications, device 20 is configured to curve, such as to conform with curvature of the ascending aorta, at least partially by virtue of portion 23F of frame 52 (i.e., the portion of the frame that corresponds to intermediate portion 23 of pressure-loss-reduction device 20) including a spiraling set of struts 76. For example, as shown, portion 23F may define a zigzag strut configuration that spirals around the portion of the frame that corresponds to intermediate portion 23 of the device. For some applications, at either end of portion 23F of the frame (i.e., at the locations that are adjacent to sinusoidal struts corresponding to folded portions 56U and 56D), the frame includes complete rows 78 of struts. For such applications, the spiraling set of struts extends from the upstream complete row of struts to the downstream complete row of struts. The complete rows of struts at either end of the intermediate portion typically provide the ends of the portion with radial strength, such that the ends of the portion do not become radially compressed, while the spiraling set of struts provides the intermediate portion with flexibility. Typically, along the spiraling set of struts, each row of struts in the spiral is not connected to adjacent rows of the spiral, such that each row of struts is able to flex with respect to the adjacent row.

[0084] For some applications (not shown), frame 52 is cut such that the frame is non-axisymmetric about its longitudinal axis. For example, the frame may be cut such that a side of the frame that is configured to be placed on the inside of the curve of the aorta is shorter than the side of the frame that is configured to be placed on the outside of the curve. For some such applications, the frame is constructed from struts that are arranged in closed cells and / or struts that are shaped as described with any one of Figs. 2A-2C, or 3A-3B, such as sinusoidal struts, spiral struts, and / or zigzagging struts. By cutting the frame such that the frame is non-axisymmetric about its longitudinal axis and then applying shape-setting techniques to the frame, the frame is typically configured such that, in the non-constrained configuration of the device, intermediate portion 23 of the device (which has inner surface 24 that defines conduit 26) is configured to be curved. For some applications, by cutting the frame such that the frame is non-axisymmetric about its longitudinal axis and then applying shape setting techniques to the frame, the frame is configured such that, in the non-constrained configuration of the device, intermediate portion 23 of the device (which has inner surface 24 that defines conduit 26) is configured to be disposed at an angle with respect to upstream anchor 33 (i.e., such that the longitudinal axis of the conduit forms an angle with respect to the longitudinal axis of the upstream anchor), but the conduit is not curved. For some applications, device 20 is configured such that the conduit becomes curved upon being placed in the ascending aorta, such as to conform to the curvature of the ascending aorta.

[0085] Reference is now made to Figs. 3 A and 3B, which are schematic illustrations of frames 52 of a pressure-loss-reduction device 20. For some applications, frame 52 is configured such that in the event that the diameter of upstream anchor 33 of the device changes, the diameter of the upstream end 30 of conduit 26 of the device does not change by the same amount, in accordance with some applications of the present disclosure. The frame as shown in Figs. 3A and 3B is generally similar to that shown in Fig. 2C, except for the differences described hereinbelow. Typically, device 20 is configured to curve, such as to conform with curvature of the ascending aorta, at least partially by virtue of portion 23F of frame 52 (i.e., the portion of the frame that corresponds to intermediate portion 23 of pressure-loss-reduction device 20) including a spiraling set of struts 76. For example, as shown, portion 23F may define a zigzag strut configuration that spirals around the portion of the frame that corresponds to intermediate portion 23 of the device. For some applications, at the downstream end of portion 23F of the frame (i.e., at the location that is adjacent to sinusoidal struts corresponding to folded portion 56D), the frame includes a complete row 78 of struts, as described hereinabove, with reference to Fig. 2C. For some applications, at the upstream end of portion 23F of the frame (i.e., at the location that is adjacent to sinusoidal struts corresponding to folded portion 56U), the frame includes a complete row 79 of closed cells.

[0086] It is typically desirable that the diameter of upstream end 30 of conduit 26 does not change substantially, since the diameter of the upstream end of the conduit is typically sized to correspond to the orifice of the subject's aortic valve. However, the upstream anchor typically undergoes variations in its diameter, for example, due to variations in pressure that is exerted upon the upstream anchor over the course of the subject's cardiac cycle. Therefore, for some applications, at the upstream end of portion 23F of the frame, the frame is reinforced relative to at least some of the rest of portion 23F (e.g. relative to a longitudinally-central portion of the intermediate portion). For example, as shown in Figs. 3A and 3B, the frame may include a complete row 79 of closed cells at the upstream end of portion 23F of the frame. In this manner, the diameter of the upstream end of the conduit is stabilized and less susceptible to changes.

[0087] Experiments were conducted by inventors of the present application, in which they measured the ratio between the change of diameter that the upstream end of the device underwent in response to changes in the diameter of the upstream anchor. It was found that when using a device as shown in Figs. 3 A-B in which the upstream anchor had an initial diameter of 30 mm and the upstream end of the conduit has an initial diameter of 14.5 mm, then in response to the diameter of the upstream anchor being reduced by 5 mm (to 25 mm), the diameter of the upstream end of the conduit decreased by less than 2 mm, and in some cases as little as 1.5 mm. Thus, in accordance with some applications of the present disclosure, the upstream end of intermediate portion 23F of the frame is reinforced, such that, a ratio of the decrease in the absolute diameter of the upstream end of conduit 26 to the decrease in the absolute diameter of the upstream anchor is less than 1:2, e.g., less than 1:3, less than 1:4, or less than 1:5.

[0088] For some applications, alternative or additional techniques to those shown in Figs. 3A and 3B are used to reinforce the upstream end of intermediate portion 23F of the frame, relative to at least some of the rest of portion 23F (e.g. relative to a longitudinally-central portion of the intermediate portion). For example, struts that are shorter and / or wider than those used in the rest of intermediate portion 23F may be used at the upstream end of intermediate portion 23F. Alternatively or additionally, a greater number of cells and / or struts may be used in the upstream-most row (or the first number of upstream-most rows) of intermediate portion 23F, than are used in other rows of intermediate portion 23F.

[0089] For some applications, the flexibility of the sinusoidal struts 60 in portion 56UF of the frame is configured such that the decrease in the absolute diameter of the upstream end of conduit 26 in response to a decrease in the absolute diameter of the upstream anchor is less than the decrease in the absolute diameter of the upstream anchor. That is to say that the sinusoidal struts are made to be flexible such that they absorb at least some of the change in the diameter of the upstream anchor, without conveying the entire change in the diameter to the upstream end of the conduit. It is noted that, typically, by increasing the flexibility of the sinusoidal struts, the radial force that the anchor exerts on the inner wall of the aorta is decreased. As such, by using the flexibility of the sinusoidal struts to stabilize the diameter of the upstream end of the conduit, there is a tradeoff between the stabilization of the diameter of the upstream end of the conduit, and the radial force that the anchor is able to exert on the inner wall of the aorta. By contrast, reinforcing the upstream end of portion 23F of the frame as described hereinabove typically results in the diameter of the upstream end of the conduit being stabilized as well as the radial force that the anchor exerts on the inner wall of the aorta being increased. Therefore, for some applications, the diameter of the upstream end of the conduit is stabilized by reinforcing the upstream end of portion 23F of the frame, as described hereinabove.

[0090] For some applications, device 20 includes one or more projections 43 that project from an upstream end of portion 33F of frame 52 (which corresponds to upstream anchor 33), as shown in Fig. 3A-3B. For example, the projections may be T-shaped projections, as shown in Figs. 3A-B. Typically, the upstream anchor 33 is placed in close proximity to the subject's aortic valve. Therefore, the length of each of projections 43 is typically less than 8 mm, e.g., less than 3 mm, in order to avoid the projections causing trauma to the aortic valve leaflets. For some applications, each of the projections has a length of more than 0.5 mm, e.g., more than 1 mm. For example, the projections may have lengths of 0.5-8 mm, or 1-3 mm. Typically, the upstream ends of the projections are configured to be atraumatic. For example, the upstream ends of the projections may be curved, as shown.

[0091] Reference is now made to Figs. 4A-B, which are schematic illustrations of respective views of frame 52 of pressure-loss-reduction device 20, the device including anchor extensions 90 on one or more anchors of the device (e.g., upstream anchor 33 and / or downstream anchor 31), in accordance with some applications of the present disclosure.

[0092] As described with reference to Figs. 2A-C, Figs. 4A and 4B show a flattened profile of device frame 52, which depicts (for illustrative purposes) how the frame of the device would appear if, prior to shape setting the frame, a longitudinal incision was to be made along the length of the frame at a given circumferential location of the frame, and the frame were to then be laid out flat upon a surface. For some applications, anchor extensions 90 are sinusoidal, as shown in Fig. 4A. For some applications, anchor extensions 90 extend from both frame portion 33F that defines upstream anchor 33, and frame portion 3 IF that defines downstream anchor 31, again as shown in Fig. 4A. As described hereinabove, for some applications, at folded portions of the device, the frame of the device defines sinusoidal struts 60. For some applications, the frame is cut from a tube of the metal or alloy, and sinusoidal anchor extensions are cut from tube at the same longitudinal portion of the tube as a portion of the frame that defines the sinusoidal struts. The sinusoidal anchor extensions are shape set, such that when the device is deployed within the subject's aorta, the sinusoidal anchor extensions exert an outward radial force upon the inner wall of the aorta, to thereby anchor the device within the aorta. For some applications, the sinusoidal shape of the anchor extensions provides the anchors with greater flexibility than if the anchors were formed from straight struts.

[0093] For some applications, sinusoidal struts 60 that form upstream folded portion 56U of device 20 are configured to extend from inter-strut junctions 92 of portion 33F of the frame that corresponds to upstream anchor 33. For some applications anchor extensions 90 extend from struts of portion 33F of the frame, between the inter-strut junctions, as shown in Fig. 4B. As described with reference to Fig. 4A, the anchor extensions are shape set, such that when the device is deployed within the subject's aorta, the anchor extensions exert an outward radial force upon the inner wall of the aorta, to thereby anchor the device within the aorta.

[0094] Reference is now made to Figs. 5A-5E, which are schematic illustrations of respective views of frame 52 of pressure-loss-reduction device 20, the device including anchor extensions 90 on one or more anchors of the device (e.g., upstream anchor 33 and / or downstream anchor 31), in accordance with additional applications of the present disclosure. Figs. 5A and 5C show a flattened profile of device frame 52 as explained hereinabove, and Figs. 5B, 5D and 5E show frame 52 in a in a non-constrained configuration (i.e., in the absence of any external force acting upon the device), in accordance with some applications of the present. Fig. 5B shows material 54 as well as frame 52 of the device, whereas Figs. 5D and 5E show frame 52 of the device in the absence of material 54, for illustrative purposes.

[0095] Figs. 5A and 5B are an example of a configuration of frame 52 comprising anchor extensions 90 extending from frame portion 33F that defines upstream anchor 33. Anchor extensions 90 are shown extending from the struts frame portion 33F between sinusoidal struts 60, which correspond to folded portions 56U and 56D. For some applications, as shown in Figs 5A and 5B, anchor extensions 90 are shaped to define curved anchor extensions. For some applications, anchor extensions 90 are cut (e.g., laser cut) from the same tube of the metal or alloy as sinusoidal struts 60 and at the same longitudinal portion of the tube as a portion of the frame that defines the sinusoidal struts. Alternatively, anchor extensions 90 are coupled to frame 52 by laser welding. Further alternatively, anchor extensions 90 are coupled to frame 52 by suturing anchor extensions 90 to material 54, e.g., a fabric, which is coupled to frame 52 as described hereinabove with reference to Fig. IB.

[0096] Anchor extensions 90 are shape set, such that when the device is deployed within the subject's aorta, the anchor extensions exert an outward radial force upon the inner wall of the aorta, to thereby anchor the device within the aorta. Typically, the addition of anchor extensions 90 to device 20, increases the ratio of the length of portion of device 20 that contacts the wall of the ascending aorta to the diameter of device 20, thereby increasing stability and anchoring of device 20 in the aorta.

[0097] Figs. 5C and 5D show an additional example of a configuration of frame 52 comprising anchor extension 90, in accordance with some applications of the present disclosure. Figs. 5C and 5D show a double row of anchor extensions comprising a first set of anchor extensions 90A and anchor extensions 90B. Anchor extensions 90 A extend from frame portion 33F that defines upstream anchor 33. Sinusoidal struts 60 extend from the strut junctions of portion 33F to row 78 of struts of portion 23F of the frame, between anchor extensions 90A. Anchor extensions 90B extend from extensions 90A toward intermediate portion 23F. Fig. 5D is a schematic illustration of frame 52 in an unconstrained assembled configuration, showing anchor extensions 90A extending from upstream anchor 33 and anchor extensions 90B extend from anchor extensions 90A such that when the device is deployed within the subject's aorta, the anchor extensions exert an outward radial force upon the inner wall of the aorta, to thereby anchor the device within the aorta. As shown, sinusoidal struts 60 form the folded portion between upstream anchor 33 and intermediate portion 23, and the folded portion between downstream anchor 31 and intermediate portion 23.

[0098] Figs. 5A-5D show anchor extensions 90 extending from upstream anchor portion 33F of frame 52 toward intermediate portion 23F. It is noted that in accordance with applications of the present disclosure, anchor extensions 90 may be added to enhance anchoring of pressure-loss-reduction device 20 either extending from upstream anchor portion 33F, or from downstream anchor portion 3 IF or both (as described hereinbelow with reference to Fig. 5E).

[0099] Fig. 5E is a schematic illustration of an additional example of a configuration of frame 52, in accordance with some applications of the present disclosure. As shown, for some applications, anchor extensions 90 extend from both upstream anchor portion 33F and downstream anchor portion 3 IF. Frame 52 shown in Fig. 5E comprises double anchor extensions 90A and 90B extending from upstream anchor portion 33F of frame 52 (as described hereinabove with reference to Figs. 5C-5D). Additionally, frame 52 shown in Fig. 5E comprises anchor extensions 90C extending from downstream anchor portion 3 IF. Anchor extensions 90A, 90B and 90C are configured such that when device 20 is deployed within the subject's aorta, the anchor extensions exert an outward radial force upon the inner wall of the aorta, to thereby anchor the device within the aorta.

[0100] Reference is now made to Figs. 5F and 5G, which are schematic illustrations of additional examples of, respectively, a configuration of frame 52 and the corresponding configuration of pressure-loss-reduction device 20, in accordance with some applications of the present disclosure. As shown, for some applications, frame 52 comprises a set of undulating (e.g., sinusoidal) struts 61 disposed between upstream anchor portion 33F of the frame corresponding to upstream anchor 33 and the upstream end of intermediate portion 23F of the frame corresponding to intermediate portion 23 of the device. The undulating struts form folded portion 56U of the frame, which is configured to be shaped such as to have a sinusoidal (i.e., S-shaped) cross-sectional shape, as described hereinabove. The plane in which the struts themselves undulate is within the plane of the surface of the aortic pressure-loss-reduction device and perpendicular to the plane in which the sinusoidal (i.e., S-shaped) cross-sectional shape of the folded portion is defined. For some applications (not shown), downstream folded portion 56D is configured in a similar manner.

[0101] Typically, undulating struts 61 are configured such that, in the event that the diameter of upstream anchor 33 of the device changes, the diameter of the upstream end 30 of conduit 26 of the device does not change by the same amount, as described in further detail herein with reference to Fig. 2A-B and 3A-B. For example, undulating struts 61 may be configured such that, in the event that the diameter of upstream anchor 33 of the device decreases, the diameter of the upstream end 30 of conduit 26 of the device decreases by a smaller absolute amount than the absolute decrease in the diameter of the upstream anchor. Or, undulating struts 61 may be configured such that, in the event that the diameter of upstream anchor 33 of the device decreases, the diameter of the upstream end 30 of conduit 26 of the device increases.

[0102] As described above, it is typically desirable that the diameter of upstream end 30 of conduit 26 (which is defined by the upstream end of the intermediate portion of the frame) does not change substantially, since the diameter of the upstream end of the conduit is typically sized to correspond to the orifice of the subject's aortic valve. However, the upstream anchor may undergo variations in its diameter, for example, due to variations in pressure that is exerted upon the upstream anchor over the course of the subject's cardiac cycle. In addition, device 20 is configured to be placed in aortas of different sizes and for the upstream anchor to become anchored to the aorta. For some applications, undulating struts 61 are configured such that in the event that the diameter of upstream anchor portion of the frame (which defines upstream anchor 33) of the device changes (or is placed in an aorta having a greater or smaller cross-sectional area), the diameter of the upstream end of the intermediate portion of the frame (which defines the upstream end of conduit 26) of the device does not change by the same amount.

[0103] For some applications, downstream folded portion 56D is configured to provide alternative or additional functionalities as described hereinabove, e.g., with reference to Fig. 2A-B and 3A-B. For some applications (not shown), struts that define downstream folded portion 56D are also shaped as undulating (e.g., sinusoidal) struts in a similar manner to that described with reference to struts 61.

[0104] Reference is now made to Fig. 5H, which shows frame 52 as configured in the embodiment shown in Fig. 3G, in accordance with some applications of the present disclosure. For some applications, frame 52 comprises anchor extensions 90 in addition to undulating struts 61 disposed between upstream anchor portion 33F of the frame corresponding to upstream anchor 33 and the upstream end of intermediate portion 23F of the frame corresponding to intermediate portion 23 of the device. As shown, anchor extensions 90 extend from upstream anchor portion 33F and undulating struts 61 are disposed between anchor extensions 90.

[0105] Reference is now made to Figs. 6A, 6B, 6C and 6D, which are schematic illustrations of a general outline of a contour of frame 52 of pressure-loss-reduction device 20 for implanting inside a subject's ascending aorta, device 20 including anchor extensions 90 to the upstream and / or downstream anchors of device 20, in accordance with some applications of the present disclosure. In accordance with some applications of the present disclosure, anchor extensions 90 at each or both of the upstream anchors 33 or downstream anchors 31 may be shaped to define cylindrical or tapered anchor extensions. For some applications, entire upstream anchor 33 (including anchor extension 90) or downstream anchor 31 (including anchor extension 90) is shaped to define a cylindrical or tapered anchor portion. For some applications, the upstream anchor and downstream anchor may be shaped to define any combination of anchors that are cylindrical, tapered in a first direction (e.g., diverging) or tapered in a second direction (e.g., converging).

[0106] For example, Fig. 6A is a schematic general outline of pressure-reduction-loss device 20 having cylindrical-shaped upstream anchor 33 and downstream anchor (including cylindricalshaped anchor extensions 90). Fig. 6B is a schematic general outline of pressure-reduction-loss device 20 having tapered upstream anchor 33 and a tapered downstream anchor 31 (including anchor extensions 90) tapered such that both the upstream anchor and the downstream anchor diverge from the respective ends of the device toward the center of the device. Fig. 6C is a schematic general outline of pressure-reduction-loss device 20 having tapered upstream anchor 33 and a tapered downstream anchor 31 (including anchor extensions 90) tapered such that both the upstream anchor and the downstream anchor converge from the respective ends of the device toward the center of the device. Fig. 6D is a schematic general outline of pressure-reduction-loss device 20 having upstream anchor 33 and anchor extensions 90 extending from anchor 33, and downstream anchor 31 and anchor extensions 90 extending from anchor 31, in which the anchors 33 / 31 and anchor extensions 90 are tapered in different directions. In the example shown, the upstream anchor and the downstream anchor converge from the respective ends of the device toward the center of the device, while both the upstream and downstream anchor extensions diverge from the respective ends of the device toward the center of the device.

[0107] Reference is now made to Figs. 7A, 7B, 7C, 7D, 7E, and 7F, which are schematic illustrations of optional configurations of pressure-loss-reduction device 20 for implanting inside a subject's ascending aorta, the device typically including anchor extensions 90 on one or more anchors of the device, in accordance with some applications of the present disclosure.

[0108] As described hereinabove, for some applications, device 20 is formed from a single continuous portion of graft material. The stent graft material is typically formed from a combination of a metal or alloy frame 52 (e.g., a stent made of stainless steel or nitinol or cobalt chromium) and material 54, e.g., a fabric and / or a polymer (such as expanded polytetrafluoroethylene (ePTFE), or woven, knitted and / or braided polyester), which is typically coupled to the frame. Typically, material 54 is impermeable and inhibits blood from flowing back toward the aortic valve during systole (and / or during diastole), outside of the conduit. In such a manner, material 54 creates a lumen within the blood vessel into which the blood is directed and through which the blood flows. Thus, any segment of the upstream or downstream ends of device 20 that form the lumen within the aorta may be covered.

[0109] Additionally, for some applications, as described hereinabove with respect to Figs. 4A-5E, pressure-loss-reduction device 20 comprises anchor extensions on one or more anchors of the device (e.g., extending from upstream anchor 33 and / or from downstream anchor 31). The anchor extensions typically enhance anchoring of device 20 in the aorta by exerting an outward radial force upon the inner wall of the aorta, to thereby anchor the device within the aorta. Figs. 7A, 7B, 7C, 7D, 7E and 7F show various configurations of device 20 comprising anchor extensions 90 on one or more anchors of the device. For some applications, the benefit of adding anchor extensions 90 is twofold. First, the addition of anchor extensions 90 provides additional anchoring of device 20 in the aorta. An additional advantage of the anchor extensions is such that covering of the anchor extensions with material 54, provides, on the one hand, coverage of the stent in a manner that creates the lumen within the aorta, and on the other hand, enables use of non-covered upstream anchor 33 and / or downstream anchor 31. In such a manner, the risk of blocking the coronary arteries or the brachiocephalic artery by material 54 covering the upstream or downstream anchors, is avoided (coronary arteries 38 are shown in Fig. 1A and brachiocephalic artery 39 is shown in Fig. 7E).

[0110] For some applications, covering of the anchor extensions with material 54 allows for elimination of the upstream anchor 33 and / or downstream anchor 31 from device 20 (i.e., manufacturing of device 20 without an upstream anchor 33 that extends axially beyond the upstream end of the intermediate portion and / or without a downstream anchor 31 that extends axially beyond the downstream end of the intermediate portion). In such a manner, conduit 26 can be placed at greater proximity to the aortic valve through which blood flows into device 20 while maintaining proper anchoring of device 20. Typically, covering of the anchor extensions with material 54 allows for a reduced distance between the vessel sealing segments (in this case the anchor extensions), when compared to anchors 33 / 31, thereby allowing for a longer intermediate portion 23 (corresponding to conduit 26), while still preventing the risk of blocking the coronary arteries or the brachiocephalic artery by material 54.

[0111] For some applications, as shown in Fig. 7A, device 20 comprises anchor extensions 90 extending from upstream anchor 33, the anchor extensions being covered by material 54, while the struts of upstream anchor 33 are bare (i.e., not covered by material 54).

[0112] For some applications, as shown in Fig. 7B, device 20 comprises anchor extensions 90 extending from both upstream anchor 33 and downstream anchor 31, the anchor extensions being covered by material 54, while the struts of upstream anchor 33 and downstream anchor 31 are bare (i.e., not covered by material 54).

[0113] For some applications, as shown in Fig. 7C, device 20 comprises a double row of anchor extensions 90A and 90B, each double row extending from both the upstream and downstream ends of device 20. In the configuration of device 20 shown in Fig. 7C, anchor extensions 90A are covered by material 54, while anchor extensions 90B remain uncovered. Additionally, in the configuration of device 20 shown in Fig. 7C, device 20 does not comprise upstream anchor 33, and downstream anchor 31 is not covered by material 54.

[0114] For some applications, as shown in Fig. 7D, device 20 comprises anchor extensions 90 extending from both upstream anchor 33 and downstream anchor 31, the anchor extensions being covered by material 54. In the configuration shown in Fig. 7D, the upstream anchor extensions include a double row of anchor extensions 90 A and 90B. Additionally, in the configuration of device 20 shown in Fig. 7D, device 20 does not comprise upstream anchor 33.

[0115] Figs. 7E and 7F shows device 20 of Fig. 7D implanted in the aorta, in accordance with some applications of the present disclosure. (Fig. 7E shows a three-dimensional view of device 20 implanted within the aorta and Fig. 7F shows a cross-sectional view of device 20 implanted in the aorta.) In the configuration of device 20 shown in Figs. 7D-F, device 20 does not comprise upstream anchor 33 thereby bringing conduit 26 into close proximity to the aortic valve. Additionally, material-covered anchor extensions at both the upstream and downstream ends of device 20, allow for maximization of the length of conduit 26 in relation to distance between vessel sealing areas (the upstream and downstream anchor extensions). Additionally, downstream anchor 31 is not covered thereby allowing blood flow through anchor 31 and preventing the risk of material 54 impeding blood flow to the brachiocephalic artery.

[0116] Reference is now made to Fig. 8, which is a schematic illustration of pressure-reduction-loss device 20 comprising a retrieval element 240 configured for facilitating retrieval of device 20 from inside the subject's ascending aorta, in accordance with some applications of the present disclosure. Retrieval element 240 is coupled to device 20 in a manner that enables recapturing of device 20 into a delivery device, (such as a catheter that is configured to deploy device 20 in a subject's ascending aorta), from a deployed state of device 20 in the aorta. For example, device 20 may be removed from the aorta using retrieval element 240 in cases of suboptimal positioning of the device. In such cases, device 20 is removed and redeployed. In other cases, retrieval element 240 facilitates permanent removal of device 20 from the aorta. Fig. 8 shows retrieval element 240 shaped to define a metallic spiral / braided retrieval element. Alternatively, retrieval element 240 may define any other suitable shape.

[0117] Typically, the retrieval element is coupled to the outside of device 20 and is configured to be disposed externally to device 20. As shown, for some applications, downstream end 244 of retrieval element 240 is coupled to device 20 at the downstream end of device 20, e.g., by being attached to struts disposed at the downstream end of portion 23 of the frame. Retrieval element 240 may be coupled to device 20 by attaching end 244 to the frame of device 20 by suturing, laser welding or any other suitable mechanical coupling technique. An upstream end 242 of retrieval element 240 is a free end that is not coupled to device 20 and is disposed at the upstream end of portion 23 of the frame. Pulling of free end 242 causes retrieval element 240 to be retrieved back into the delivery device, which in turn causes crimping of device 20, allowing its safe removal from the aorta.

[0118] As shown in Fig. 8, retrieval element 240 is disposed externally to device 20, such that when deployed in the aorta, retrieval element 240 is positioned within region 36 (shown in Fig.

[0119] 1 A) defined between conduit 26 and the inner wall of the aorta within the longitudinal portion of the aorta in which device 20 is placed. As described hereinabove, with reference to Figs. 1A andlB, blood flow through region 36 is generally impeded by upstream and downstream outer surfaces 28 and 32 of pressure-loss-reduction device 20. By being disposed externally (i.e., outside an outer surface of device 20), retrieval element 240 generally does not interfere with operation of device 20 (for example, retrieval element 240 does not occupy space within conduit 26 thereby not disrupting blood flow through the conduit). Additionally, since blood flow is generally directed through device 20 and impeded in region 36, retrieval element 240, being positioned in region 36 generally does not interfere with functioning of the aorta, subsequent to device 20 being deployed.

[0120] Reference is now made to Figs. 9A and 9B, which are schematic illustrations of pressure-loss-reduction device 20 comprising stent graft 50 comprising a frame 52 that is a braided stent and a layer of material 54 which is shaped to define a plurality of folds 58, in accordance with some applications of the present disclosure. Fig. 9A shows the material in the absence of frame 52. As described hereinabove with reference to Fig. IB, device 20 is formed from a stent graft material, which is typically formed from a combination of a metal or alloy frame 52 (e.g., a stent made of stainless steel or nitinol or cobalt chromium) and material 54, e.g., a fabric and / or a polymer (such as expanded polytetrafluoroethylene (ePTFE), or woven, knitted and / or braided polyester), which is typically coupled to the frame via stitching, spray coating, encapsulation, electrospinning, dip molding and / or a different technique. For some applications, frame 52 of the stent graft material is a braided stent. For some applications, the braided stent provides flexibility to the device that facilitates insertion of the device via curved portions of the vasculature. For some applications, using a braided stent allows the device to be radially constrained to a narrower diameter than would be possible using a non-braided stent. As shown in Figs. 9A and 9B, for some applications, material 54 covering the braided stent is arranged in a set of folds 58 (e.g., pleated portions), folds 58 comprising excess material 54. In such a manner, the braided stent is allowed to assume an elongated configuration while being loaded into the delivery device (e.g., a catheter) for delivery to the desired location in the ascending aorta. When the braided stent of frame 52 is radially constrained (i.e., the frame is crimped into a reduced diameter and an elongated configuration for fitting into the delivery device), folds 58 are allowed to unfold to thereby provide additional material allowing the braided stent to elongate, such that the aortic-pressure-loss-reduction device is able to assume its radially-constrained configuration. In other words, by providing folds 58 having excess material, material 54 is not a limiting factor in the elongation of frame of the braided stent.

[0121] For some applications, folds 58 are fixated by thermal processing e.g., ironing, such that in a non-constrained configuration of frame 52, a location, position, and / or shape of folds 58 can be controlled and pre-determined. Typically, lengths of each of folds 58 at intermediate portion 23 are between 1 and 8 mm.

[0122] For some applications, material 54 covers the inside of at least a portion of frame 52, such that blood flowing through the device contacts the material. Alternatively or additionally, the material is disposed outside at least a portion of the frame, for example, in order to facilitate retraction of the device back into a delivery device. For example, a first layer of material may be disposed inside the frame, and a second layer of the material may be disposed outside the frame. For some applications, at least a portion of the frame is embedded within the material. For some applications, material 54 is disposed inside the frame at intermediate portion 23 (corresponding to conduit 26) and disposed outside the frame at the upstream anchor portion of device 20 (corresponding to upstream anchor 33), as shown in Fig. 9A. Typically, folds 58 at intermediate portion 23 (corresponding to conduit 26) are folded in a direction corresponding to the direction of systolic blood flow, in order to maximize streamlining of the blood flow pattern.

[0123] It will be appreciated by persons skilled in the art that the present disclosure is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present disclosure includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.

Claims

CLAIMS1. Apparatus for use with a delivery device comprising:an aortic pressure-loss-reduction device configured to be delivered to and implanted inside an ascending aorta of a subject using the delivery device, the aortic pressure-loss-reduction device comprising:a frame that is configured, in a non-constrained configuration thereof, to define:an upstream anchor portion configured to radially expand against an inner wall of the subject's ascending aorta, such as to anchor an upstream end of the aortic pressure-loss- reduction device to the subject's ascending aorta;an intermediate portion configured to define a conduit therethrough, such that blood is configured to flow through the device via the conduit, at least a portion of the conduit diverging, such that a downstream end of the diverging portion has a greater cross-sectional area than an upstream end of the diverging portion;a downstream anchor portion configured to radially expand against the inner wall of the subject's ascending aorta, such as to anchor a downstream end of the aortic pressure- loss-reduction device to the subject's ascending aorta;at least one layer of material coupled to at least a portion of the frame, the material layer configured to impede blood flow therethrough; anda retrieval element configured to facilitate retrieval of the aortic pressure-loss-reduction device from the ascending aorta back into the delivery device, the retrieval element being coupled to an outside of the aortic pressure-loss-reduction device and configured to be disposed externally to the aortic pressure-loss-reduction device.

2. The apparatus according to claim 1, wherein the retrieval element is coupled to the outside of the aortic pressure-loss-reduction device and configured to be disposed externally to the aortic pressure-loss-reduction device, such that upon aortic pressure-loss-reduction device being implanted within the subject’s ascending aorta, the retrieval element is disposed within a region between the conduit and the inner wall of the subject’s aorta.

3. The apparatus according to claim 1, wherein the retrieval element is coupled to the outside of the aortic pressure-loss-reduction device at a downstream end of the aortic pressure-loss-reduction device.

4. The apparatus according to claim 1, wherein the retrieval element is coupled to the outside of the aortic pressure-loss-reduction device at a downstream end of the intermediate portion of the frame.

5. The apparatus according to claim 1, wherein the retrieval element comprises a metallic spiral retrieval element.

6. The apparatus according to claim 1, wherein the retrieval element comprises a metallic braided retrieval element.

7. The apparatus according to claim 1, wherein the retrieval element is coupled to the aortic pressure-loss-reduction device by suturing.

8. The apparatus according to claim 1, wherein the retrieval element is coupled to the aortic pressure-loss-reduction device by laser welding.

9. The apparatus according to claim 1, wherein the retrieval element comprises a free end that is not coupled to the aortic pressure-loss-reduction device, and that is configured to be pulled to cause crimping of the aortic pressure-loss-reduction device.

10. Apparatus for use with a delivery device comprising:an aortic pressure-loss-reduction device configured to be delivered to an ascending aorta of a subject using the delivery device, while the aortic pressure-loss-reduction device is in a radially-constrained configuration within the delivery device, the aortic pressure-loss-reduction device being configured to become implanted within the subject’s ascending aorta in a non-radially-constrained configuration, the aortic-pressure-loss-reduction device comprising:a braided stent that is configured, in the non-radially-constrained configuration of the aortic-pressure-loss-reduction device, to define:an upstream anchor portion configured to radially expand against an inner wall of the subject's ascending aorta, such as to anchor an upstream end of the aortic pressure-loss- reduction device to the subject's ascending aorta;an intermediate portion configured to define a conduit therethrough, such that blood is configured to flow through the device via the conduit, at least a portion of the conduit diverging, such that a downstream end of the diverging portion has a greater cross-sectional area than an upstream end of the diverging portion;a downstream anchor portion configured to radially expand against the inner wall of the subject's ascending aorta, such as to anchor a downstream end of the aortic pressure- loss-reduction device to the subject's ascending aorta;at least one layer of material coupled to at least a portion of the braided stent, the material layer configured to impede blood flow therethrough, the material layer being arranged in a set of folds that comprise excess material in the non-radially-constrained configuration of the aortic-pressure-loss-reduction device, the folds being configured to unfold to thereby provide additionalmaterial to allow the aortic-pressure-loss-reduction device to assume its radially-constrained configuration.

11. The apparatus according to claim 10, wherein lengths of each of the folds at the intermediate portion of the braided stent are between 1 and 8 mm.

12. The apparatus according to claim 10, wherein the covering material covers an inside of at least a portion of the braided stent.

13. The apparatus according to claim 10, wherein at least a portion of the braided stent is embedded within the covering material.

14. The apparatus according to claim 10, wherein the material layer covers an inside of the intermediate portion of the braided stent and an outside of the upstream anchor portion of the braided stent.

15. The apparatus according to claim 10, wherein at least a portion of the material layer covers an inside of the intermediate portion of the braided stent, and wherein the folds in the portion of the material layer that covers the inside of the intermediate portion of the braided stent are folded in a direction corresponding to a direction of systolic blood flow.

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