The application for patent relates to medical devices. Exemplary embodiments described herein relate to valves that can be implanted in a body vessel or other suitable locations within the body of an animal, such as a human.
Many vessels in animal bodies transport fluids from one bodily location to another. Frequently, fluid flows in a unidirectional manner along the length of the vessel. Varying fluid pressures over time, however, can introduce a reverse flow direction in the vessel. In some vessels, such as mammalian veins, natural valves are positioned along the length of the vessel and act as one-way check valves that open to permit the flow of fluid in the desired direction and close to prevent fluid flow in a reverse direction, i.e., retrograde flow. The valves can change from an open position in response to a variety of circumstances, including changes in the cross-sectional shape of the vessel and the fluid pressure within the vessel.
While natural valves may function for an extended time, some may lose effectiveness, which can lead to physical manifestations and pathology. For example, venous valves are susceptible to becoming insufficient due to one or more of a variety of factors. Over time, the vessel wall may stretch, affecting the ability of the valve members to close. Furthermore, the valve members may become damaged, such as by formation of thrombus and scar tissue, which may also affect the ability of the valve members to close. Once valves are damaged, venous valve insufficiency may be present, which can lead to discomfort and possibly ulcers in the legs and ankles.
Current treatments for venous valve insufficiency include the use of compression stockings that are placed around the leg of a patient in an effort to force the vessel walls radially inward to restore valve function. Surgical techniques are also employed in which valves can be bypassed, eliminated, or replaced with autologous sections of veins having competent valves.
Minimally invasive techniques and instruments for placement of intraluminal medical devices have developed over recent years. A wide variety of treatment devices that utilize minimally invasive technology has been developed and includes stents, stent grafts, occlusion devices, infusion catheters and the like. Minimally invasive intravascular devices have especially become popular with the introduction of coronary stents to the U.S. market in the early 1990s. Coronary and peripheral stents have been proven to provide a superior means of maintaining vessel patency, and have become widely accepted in the medical community. Furthermore, the use of stents has been extended to treat aneurysms and to provide occlusion devices, among other uses. Recently, valves that are implantable by minimally invasive techniques have been developed. Frequently, a valve member is attached to a support frame and provides a valve function to the device. For example, the valve member can be in the form of a leaflet that is attached to a support frame and movable between first and second positions. In a first position, the valve is open and allows fluid flow to proceed through a vessel in a first direction, and in a second position the valve is closed to prevent fluid flow in a second, opposite direction. Examples of this type of valve are described in commonly owned U.S. Pat. No. 6,508,833 to Pavcnik for a MULTIPLE-SIDED INTRALUMINAL MEDICAL DEVICE, United States Patent Application Publication No. 2001/0039450 to Pavcnik for an IMPLANTABLE VASCULAR DEVICE, and U.S. patent application Ser. No. 10/642,372, filed on Aug. 15, 2003, each of which is hereby incorporated by reference in its entirety. In other examples of valve medical devices, a tube that terminates in valve members is attached to one or more support frames to form a valve. The valve members open to permit fluid flow in a first direction in response to fluid pressure on one side of the valve members, and close to prevent fluid flow in a second, opposite direction in response to fluid pressure on opposite sides of the valve members. An example of this configuration is provided in U.S. Pat. No. 6,494,909 to Greenhalgh for AN ENDOVASCULAR VALVE, which is hereby incorporated by reference in its entirety.
Natural valves can be somewhat ‘leaky,’ allowing a relatively small quantity of fluid to flow in a reverse direction, i.e., retrograde flow, when the valve is in a closed position. It is believed that this leakiness is beneficial for several reasons. For example, it is believed that a small amount of retrograde flow limits the pooling of blood around the natural valve during periods of low pressure, which can reduce the formation of thrombus adjacent the valve members and, therefore, increase the effective lifetime of the valve.
Prior art valve devices, however, do not permit a controlled amount of retrograde flow. Indeed, most prior art valves have been designed to prevent leakage as much as possible. Accordingly, there is a need for valve devices that permit a controlled amount of retrograde flow.
Medical devices comprising a valve for regulating fluid flow through a body vessel are described. The valves can be used in a variety of locations, including venous and cardiac applications, and include a leak path through which a controlled amount of retrograde flow can pass.
An implantable medical device according to one exemplary embodiment comprises a support frame having radially compressed and radially expanded configurations and a means for forming a leak path between the support frame and an interior wall of said body vessel. A valve member is attached to the support frame and is moveable between a first position that permits said fluid flow in a first direction and a second position that substantially prevents said fluid flow in a second direction. Any suitable means for forming a leak path can be used, including one or more channels, one or more projections, one or more contours, such as a series of scallops, and one or more support wings.
An implantable medical device according to another exemplary embodiment comprises a support frame having radially compressed and radially expanded configurations. A portion of the support frame defines a channel that forms a leak path with a portion of a body vessel and allows passage of a controlled amount of fluid flow. A valve member is attached to the support frame and is moveable between first and second positions to selectively allow fluid flow through a valve orifice.
Additional understanding of the invention can be obtained with review of the description of exemplary embodiments of the invention, appearing below, and the appended drawings that illustrate exemplary embodiments.
The following provides a detailed description of exemplary embodiments. The description is not intended to limit the scope of the invention, or its protection, in any manner, but rather serves to enable those skilled in the art to practice the invention.
Medical devices that can be used in a variety of applications are provided. For example, medical devices according to exemplary embodiments comprise valves that can be used to regulate fluid flow through a body vessel. The valves can be implanted in a body vessel, or in any other suitable environment, to regulate the flow of fluid. Valves according to the invention can also be implanted in ducts, canals, and other passageways in the body, as well as cavities and other suitable locations. Valves according to exemplary embodiments of the invention can be implanted in the vessels of the vasculature, such as veins, to regulate the flow of blood through the vessels. Valves according to the invention can also be implanted in the vessels of the heart, including the aorta, as a heart valve.
As used herein, the term “implanted,” and grammatically related terms, refers to the positioning of an item in a particular environment, either temporarily, semi-permanently, or permanently. The term does not require a permanent fixation of an item in a particular position.
The valve members 112, 114 comprise a section of material. The valve members 112, 114 can be formed of any suitable material, and need only be biocompatible or be able to be made biocompatible and be able to perform as described herein. The valve members 112, 114 advantageously can be formed of a flexible material. Examples of suitable materials for the valve members 112, 114 include natural materials, synthetic materials, and combinations of natural and synthetic materials. Examples of suitable natural materials include extracellular matrix (ECM) materials, such as small intestine submucosa (SIS), and other bioremodellable materials, such as bovine pericardium. Other examples of ECM materials that can be used in the medical devices of the invention include stomach submucosa, liver basement membrane, urinary bladder submucosa, tissue mucosa, and dura mater. Examples of suitable synthetic materials include polymeric materials, such as expanded polytetrafluoroethylene and polyurethane. ECM materials are particularly well-suited materials for use in the valve members 112, 114 at least because of their abilities to remodel and to provide a scaffold onto which cellular in-growth can occur, eventually allowing the material to remodel into a structure of host cells.
The valve members 112, 114 can be attached to the support frame 116 in any suitable manner. As illustrated in
Free edges 126, 128 of the valve members 112, 114 cooperatively define a valve orifice 122. The valve members 112, 114 are moveable between first and second positions. In the first position, the orifice 122 is open and allows fluid flow through the valve 110 in a first direction, represented by arrow 170. In the second position, the free edges 126, 128 of the valve members 112, 114 come together to close the orifice 122 and substantially prevent fluid flow through the valve 110 in a second, opposite direction, represented by arrow 172.
The leak path 120 permits a controlled amount of fluid flow through the valve 110. This controlled fluid flow can pass through the leak path 120 when the valve orifice 122 is in the open and/or closed position. It is expected, however, that fluid will flow through the leak path 120 more readily when the orifice 122 is closed because, in this configuration, the leak path 120 is the only path through which fluid can flow through the valve 110. As a result, the leak path 120 is expected to provide a path for retrograde flow to flow across the valve 110.
The support frame 116 can comprise any suitable support frame. A wide variety of support frames are known in the medical technology arts, and any suitable support frame can be utilized. The specific support frame chosen will depend on several considerations, including the nature of the valve member, the nature of the point of treatment at which the medical device will be implanted, and the medical condition for which the medical device is being used. The support frame 116 need only provide a surface to which the valve member can be attached and provide the structure needed to form the leak path 120.
The support frame 116 advantageously has radially compressed and radially expanded configurations. Such a support frame 116 can be implanted at a point of treatment within a body vessel by minimally invasive techniques, such as via delivery and deployment with an intravascular catheter. The support frame 116 can optionally provide additional function to the medical device 110. For example, the support frame 116 can provide a stenting function, i.e., exert a radially outward force on the interior wall 182 of the vessel 180 in which the medical device 110 is implanted. By including a support frame 116 that exerts such a force, a medical device according to the invention can provide both a stenting and a valving function at a point of treatment within a body vessel.
The support frame 116 can be self-expandable or balloon expandable. The structural characteristics of both of these types of support frames are known in the art, and are not detailed herein. Each type of support frame has advantages and, for any given application, one type may be more desirable the other based on a variety of considerations. For example, in the peripheral vasculature, vessels are generally more compliant and typically experience dramatic changes in their cross-sectional shape during routine activity. Medical devices for implantation in the peripheral vasculature should retain a degree of flexibility to accommodate these changes of the vasculature. Accordingly, medical devices according to the invention intended for implantation in the peripheral vasculature, such as venous valves, advantageously include a self-expandable support frame. These support frames, as known in the art, are generally more flexible than balloon-expandable support frames following deployment.
The support frame 116 can be formed of any suitable material and need only be biocompatible or able to be made biocompatible. The support frame 116 is advantageously made from a resilient material, preferably metal wire formed from stainless steel or a superelastic alloy, such as nitinol. While round wire is depicted in
As used herein, the term “resorbable” refers to the ability of a material to be absorbed into a tissue and/or body fluid upon contact with the tissue and/or body fluid. The contact can be prolonged, and can be intermittent in nature. A number of resorbable materials are known in the art, and any suitable resorbable material can be used. Examples of suitable types of resorbable materials include resorbable homopolymers, copolymers, or blends of resorbable polymers. Specific examples of suitable resorbable materials include poly-alpha hydroxy acids such as polylactic acid, polylactide, polyglycolic acid (PGA), and polyglycolide; trimethylene carbonate; polycaprolactone; poly-beta hydroxy acids such as polyhydroxybutyrate and polyhydroxyvalerate; and other polymers such as polyphosphazenes, polyorganophosphazines, polyanhydrides, polyesteramides, polyorthoesters, polyethylene oxide, polyester-ethers (e.g., polydioxanone) and polyamino acids (e.g., poly-L-glutamic acid or poly-L-lysine). There are also a number of naturally derived resorbable polymers that may be suitable, including modified polysaccharides, such as cellulose, chitin, and dextran, and modified proteins, such as fibrin and casein.
As described above, the support frame 116 defines a series of scallops 118 for formation of the leak paths 120. Any suitable size, configuration, and number of scallops 118 can be used, and the specific size, configuration, and number used in a medical device according to a particular embodiment of the invention will depend on several considerations, including the desired quantity of fluid flow through the leak paths 120. In the illustrated embodiment, the scallops 118 are defined by a portion of the support frame 116 that has a substantially sinusoidal configuration.
In this embodiment, the support frame 216 defines a projection 224. As best illustrated in
The projection 224 can have any suitable shape and configuration, and can be positioned at any suitable location on the support frame 216. As best illustrated in
In the embodiment illustrated in
In this embodiment of the invention, a portion of the support frame 316 defines a channel 324 that permits a controlled amount of fluid flow through the valve 310, including retrograde flow. The channel 324 cooperates with an interior wall 382 of a body vessel 380 to form a leak path.
Any suitable configuration can be used for the channel 324. Further, more than one channel can be included. The specific configuration and number chosen for any particular medical device according to the invention will depend on several considerations, including the type of support frame used and the quantity of flow needed to pass through a leak path.
In the embodiment illustrated in
To facilitate fluid flow through the channel 324, it may be advantageous to include a coating on the portions of the support frame 316 that define the channel 324. Any suitable coating can be used and should be chosen to facilitate, rather than hinder, fluid flow. Examples of suitable coatings include non-thrombogenic and thromboresistant coatings, such as heparin and suitable heparin-containing compounds and mixtures. Of course, any coating having desirable properties can be used.
In this embodiment, the valve members 312, 314 are attached to the support frame 316 in a manner that does not significantly obstruct fluid flow through the channel 324. As illustrated in
A first end 422 of the graft member 418 terminates in a valve orifice 424 that is supported by first 426 and second 428 upstanding arms formed by the second support frame 414. The valve orifice 424 opens and closes to permit and substantially prevent fluid flow through the valve 410 in first and second directions, respectively.
A second end 430 of the graft member 418 is attached to a circumferential support member 432 of the first support frame 412. The circumferential support member 432 defines a series of undulations 434. The second end 430 of the graft member 418 is attached to the circumferential support member 432 to substantially follow the series of undulations 434. As illustrated in
The circumferential support member 432 can have any suitable configuration, and the illustrated configuration is exemplary in nature. The circumferential support member 432 need only provide a configuration that facilitates formation of one or more leak paths between the graft member 418 and the interior vessel wall 482.
The graft member 418 can also include additional features that facilitate the passage of fluid flow that does not encounter the valve orifice 424, such as slits 438.
The graft member 418 is a flexible member and can be formed of any suitable material, including all materials described above for the valve members in other embodiments.
In this embodiment, first 550 and second 552 spacing wings are disposed on the first support frame 512. As illustrated in
In the illustrated embodiment, the spacing wings 550, 552 are integrally formed by the wire member of the first support frame 512. The wings 550, 552 can, however, comprise separately attached members or have any other suitable configuration. Also, while the illustrated embodiment includes two spacing wings 550, 552, any suitable number of spacing wings can be used. The number chosen for a medical device according to a particular embodiment of the invention will depend on several considerations, including the quantity of fluid flow desired to pass through the body vessel without encountering the valve orifice 524.
In the tubular valve embodiments illustrated in
The leak path in any embodiment can enable flow from any suitable location or locations along a length of the medical device. The location(s) chosen for a medical device according to a particular embodiment will depend on several considerations, including the environment in which the medical device is intended to be placed. For example, venous valves that include one or more valve members that form pockets with the vessel wall may benefit from a leak path that enables retrograde flow from the pocket region of the device. Adaptations, such as the scallops illustrated in
The inclusion of a leak path in medical devices in which a flexible material is used in the valve-forming element, such as the valve members illustrated in
The foregoing detailed description provides exemplary embodiments of and includes the best mode for practicing the invention. These embodiments are intended only to serve as examples of the invention, and not to limit the scope of the invention, or its protection, in any manner.
This application is a continuation of U.S. patent application Ser. No. 11/291,636, filed on Dec. 1, 2005 and which claims priority to U.S. Provisional Application Ser. No. 60/522,998, filed on Dec. 1, 2004. Each of these related applications is hereby incorporated by reference into this disclosure in its entirety.
Number | Date | Country | |
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60522998 | Dec 2004 | US |
Number | Date | Country | |
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Parent | 11291636 | Dec 2005 | US |
Child | 12688827 | US |