Patent Application
20220126012
When performing hemodialysis, a vascular access device functions as an access point through which blood is removed and returned to the patient. The vascular access allows large amounts of blood to flow during hemodialysis treatments to filter as much blood as possible per treatment. An arteriovenous (“AV”) fistula is one type of vascular access improvement and is a connection, made by a vascular surgeon, of an artery to a vein. An AV fistula causes added pressure and blood to flow into the vein making it grow and become stronger for easy and reliable access.
Coronary artery bypass grafting (“CABG”) is a surgical procedure that uses a blood vessel from another part of the body, such as, for example, the great saphenous vein from the leg, and connects it to blood vessels above and below a narrowed or blocked coronary artery or arteries, thereby bypassing the narrowed or blocked coronary artery or arteries.
There is a need to provide stronger AV fistulas and coronary artery bypass grafts having less stressed venous tissue that allow for the natural expansion of the blood vessel(s) while also supporting the blood vessel(s).
In one aspect of the present disclosure, a method of establishing an anastomosis is provided and includes connecting a blood vessel and an artery, thereby forming an anastomosis therebetween; and wrapping an outer surface of the blood vessel with a first tubular support, whereby the first tubular support exerts a radially-inward force on the blood vessel.
In other aspects of the present disclosure, wrapping the outer surface of the blood vessel may include covering both a portion of the blood vessel and the anastomosis with the first tubular support.
In other aspects of the present disclosure, the method may further include positioning an end of the artery through an opening defined in a side of the first tubular support.
The method may further include connecting the artery end to another blood vessel. The blood vessel may be a vein.
In other aspects of the present disclosure, the end of the artery may be positioned through the opening prior to connecting the vein and the artery and prior to wrapping the outer surface of the vein with the first tubular support.
In other aspects of the present disclosure, the method may further include wrapping an outer surface of the artery with a second tubular support.
In other aspects of the present disclosure, the method may further include connecting an end of the second tubular support with the side of the first tubular support.
In other aspects of the present disclosure, the method may further include positioning a segment of the blood vessel and a segment of the artery in parallel relation to one another. In aspects, the method may further include completing a vascular anastomosis of the artery and vein in the parallel region. The method may include wrapping the first tubular support around an outer surface of the connecting segment of the artery as the first tubular support is then also wrapped around the outer surface of the connecting segment of the vein.
In other aspects of the present disclosure, the method may further include ligating side branches from the blood vessel at a plurality of ligation sites; and aligning the ligation sites with respective open cells defined in the tubular support.
In other aspects of the present disclosure, wrapping the first tubular support may include transitioning the first tubular support from a substantially planar configuration to a cylindrical configuration. In the cylindrical configuration, a pair of longitudinal edges of the first tubular support may be disposed adjacent one another. Any degree of overlap between the longitudinal edges may be permitted to further strengthen the external support effect to limit the extent of radial expansion of an enclosed blood vessel.
In other aspects of the present disclosure, wrapping the first tubular support may include helically winding the first tubular support around the outer surface of the blood vessel. The first tubular support may surround the entire outer surface of the blood vessel or to any suitable extent needed to strengthen the external support effect.
In accordance with another aspect of the disclosure, a medical implant for providing external support to an arteriovenous fistula or coronary artery bypass graft is provided. The medical implant includes a main tubular body configured to transition between an opened configuration and a closed configuration. In the closed configuration, the main tubular body defines a longitudinally-extending main passageway therethrough configured to receive a first blood vessel. The main tubular body is resiliently biased toward the closed configuration and includes a proximal end portion, a distal end portion, and an intermediate portion disposed between the proximal and distal end portions. Each of the proximal and distal end portions defines an opening in communication with the main passageway. The intermediate portion defines a side opening in communication with the main passageway and configured to receive and support a second blood vessel therein.
In other aspects of the present disclosure, the main tubular body may have a pair of longitudinal edges configured to be disposed adjacent one another when the main tubular body is in the closed configuration.
In other aspects of the present disclosure, the pair of longitudinal edges may together define a seam that extends along a length of the main tubular body. The seam and the side opening may be disposed in opposing relation to one another.
In other aspects of the present disclosure, the side opening may have a circular shape. The circular shape may be a circle, an oval, or the like.
In other aspects of the present disclosure, the distal end portion of the main tubular body may have a distal edge that extends at a non-perpendicular angle relative to a longitudinal axis of the main tubular body.
In other aspects of the present disclosure, the medical implant may further include a branching tubular body configured to transition between an opened configuration and a closed configuration, in which the branching tubular body defines a longitudinally-extending branching passageway therethrough. The branching passageway may be in communication with the main passageway and may be configured to receive and support the second blood vessel. The branching tubular body may be resiliently biased toward the closed configuration and may include a branching proximal end portion and a branching distal end portion. The branching proximal end portion may define an opening in communication with the branching passageway and the branching distal end portion may define an opening in communication with the branching passageway.
In other aspects of the present disclosure, the main tubular body and the branching tubular body may be fabricated from a mesh that defines a plurality of discrete cells. Each of the discrete cells may have a smaller diameter than the side opening and may be sized to accommodate all or a portion of a ligated side branch on the exterior of the supported vein.
In other aspects of the present disclosure, the main tubular body and the branching tubular body may be fabricated from a shape memory material.
In accordance with another aspect of the disclosure, a method of establishing an arteriovenous fistula graft is provided and includes wrapping an outer surface of a vein with a tubular support; positioning an end of an artery through an opening defined in a side of the tubular support; and connecting the end of the artery to a side of the vein, thereby forming a fluid connection therebetween.
In other aspects of the present disclosure, the tubular support may define a longitudinally-extending passageway. The passageway may have an inner diameter that approximates an outer diameter of the vein or artery, whereby the tubular support exerts a radially-inward force on the vein or artery.
In other aspects of the present disclosure, wrapping the outer surface of the vein with the tubular support includes transitioning the tubular support from a substantially planar configuration to a cylindrical configuration. In the cylindrical configuration, a pair of longitudinal edges of the tubular support may be disposed adjacent one another. In other aspects, wrapping the outer surface of the vein with the tubular support may include helically winding the tubular support around the outer surface of the vein.
As used herein, the terms parallel and perpendicular are understood to include relative configurations that are substantially parallel and substantially perpendicular up to about + or −10 degrees from true parallel and true perpendicular.
Embodiments of the present disclosure are described herein with reference to the accompanying drawings, wherein:
Embodiments of the disclosed medical implants and methods are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein the term “distal” refers to that portion of the medical implant, or component thereof, farther from the user, while the term “proximal” refers to that portion of the medical implant, or component thereof, closer to the user.
As will be described in detail below, a method of forming and supporting an arteriovenous (“AV”) fistula graft is provided utilizing a tubular structure that surrounds a portion of a venous and/or arterial portion of the AV fistula. The tubular structure may be a mesh tube having a longitudinal seam with improved radial compliance and openings that mitigate the stenosis caused by side branch ligature. Further provided herein is a method of forming and supporting an autologous vein coronary artery bypass graft (“CABG”) utilizing the tubular structure that surrounds the anastomosis between the coronary artery and the vein graft and/or the anastomosis between the aortic arch and the vein graft. Other features and benefits of the disclosed medical implants and methods of use thereof are further detailed below.
With reference to
In aspects, the medical implant 10 may be coated with or have embedded therein one or more therapeutic agents or delivery to a blood vessel after implantation. The therapeutic agent may be applied via dipping, ultrasonic spraying, electrostatic spraying, inkjet coating, and the like. The therapeutic agent may be capable of providing enhanced healing to the blood vessel and/or producing a beneficial effect against one or more conditions including coronary restenosis, cardiovascular restenosis, angiographic restenosis, arteriosclerosis, hyperplasia, and other diseases or conditions. The therapeutic agent may include, but are not limited to, an antisense agent, an antineoplastic agent, an antiproliferative agent, an antithrombogenic agent, an anticoagulant, an antiplatelet agent, an antibiotic, an anti-inflammatory agent, a steroid, a gene therapy agent, an organic drug, a pharmaceutical compound, a recombinant DNA product, a recombinant RNA product, a collagen, a collagenic derivative, a protein, a protein analog, a saccharide, a saccharide derivative, any suitable pharmaceutical drug or therapeutic substance, or a combination thereof. In certain aspects, the medical implant 10 may also be coated with a polymer for improved biocompatibility. The polymer coating may or may not be biodegradable. In embodiments, the polymer coating may include the therapeutic agent.
The medical implant 10 may be machined or laser cut from a solid tube of material to form the interconnected strands according to the present disclosure. In other aspects, the medical implant 10 may formed by braiding metal wire, polymer filaments, or combinations thereof, into desired shapes described in the disclosure. In aspects, the medical implant 10 may be laser cut from a flat metal sheet. To get the medical implants 10 in the desired tube form, the implants 10 are heat set while wrapped around a mandrel. When the mandrel has the form of a straight tube, and the laser cut device is wrapped around the mandrel and then heat set. The result is a perfect tubular-shaped device with parallel longitudinal seams. When the mandrel has different diameters at either end, i.e., a long tapered conical-shaped mandrel, and the device is wrapped around the mandrel and heat set, the resultant device maintains the shape of a tapered cone with non-parallel seams and different diameters at either end.
The medical implant 10 may be configured to transition, either manually or automatically, between an opened configuration and the closed configuration (
The tubular body 12 defines a longitudinally-extending passageway 14 therethrough dimensioned to receive a blood vessel, such as, for example, a vein of an AV fistula or a saphenous vein CABG. With a blood vessel, such as a saphenous vein, disposed within the passageway 14, the tubular body 12 is configured to exert a radially-inward force on the vein to restrict the outer diameter of the vein maximally to its venous physiological outer diameter while under venous or arterial pressure, or, restrict the outer diameter of the vein minimally to the outer diameter of a connecting artery. In the latter case, the tubular body 12 allows an isodiametric anastomotic connection. Intermediate levels of vein restriction between these extremes are also contemplated.
The tubular body 12 includes a proximal end portion 12a, a distal end portion 12b, and an intermediate portion 12c disposed between the proximal and distal end portions 12a, 12b. Each of the proximal and distal end portions 12a, 12b defines an opening 18, 20 in communication with the passageway 14 to allow for ends of a vein of an AV fistula to extend respectively therethrough or ends of a coronary artery bypass graft (see
With brief reference to
With reference to
The connection between adjacent filaments 25 forms a plurality of discrete or enclosed cells 26 each having a 1:1 width to height ratio. In aspects, the width and height of each of the cells 26 may be from about 1 mm to about 5 mm, which in embodiments may be from about 2 mm to about 4 mm. Other dimensions and ratios for the cells 26 are also contemplated, such as the cells 326, 426 of the medical implants 300, 400 shown in
The tubular body 12 has a pair of longitudinal edges 16a, 16b (
With reference to
The tubular body 102 has a proximal end portion 102a, a distal end portion 102b, and an intermediate portion 102c disposed between the proximal and distal end portions 102a, 102b. The intermediate portion 102c defines a side opening 108 in communication with the passageway 104 and configured to receive and support an end of an arterial or venous portion of the AV fistula, as will be described in further detail below. The side opening 108 may have a circular shape, such as, for example, an oval (as shown in
As shown in
For the medical implants of
With reference to
With reference to
The common initial step in each of the four procedures may include dissection and freeing up of the vein and artery segments identified for creation of the AV fistula. During this process, the vessels are typically minimally disturbed in their in situ position while ligating and cutting off any small interfering side branches. The flush removal of all side branches may be performed. Minimal trauma dissection and freeing up of the vessel segments prevents any damage to the intimal layers and subintimal layers of the vein or artery before application of the selected medical implant, where such damage may override one of the main functions of the medical implant of preventing intimal and subintimal damage to the delicate cellular and extracellular components of the vessel wall.
When performing the AV fistula of
More specifically before re-establishing blood flow/cross clamp release, the medical implant 10 is positioned over the vein “V.” To position the medical implant 10 over the vein “V,” the medical implant 10 may be transitioned toward the opened configuration by manually separating the longitudinal edges 16a, 16b of the medical implant 10 and then wrapping the medical implant 10 around the vein “V” by allowing the medical implant 10 to return to its unbiased, closed configuration about the vein “V.” The medical implant 10 may have a length of about 10× the external diameter of the vein “V.” In aspects, the clinician may trim the medical implant 10 to the appropriate length using a fine sharp surgical scissor. The thin struts of the medical implant 10 allow for such ease of trimming including the removal of any protruding partial struts.
In another aspect, the medical implant 10 may be positioned over the vein “V” by first inserting a spreading device, such as, for example, a C-shaped tube 21 (
When positioning the medical implant 10 over the vein “V,” each of the side branch ligatures of the vein “V” is aligned with a respective cell 26 of the medical implant 10 to prevent/minimize luminal encroachment due to ligature and side branch tissue being pinned between the tubular body 12 and the vein “V.” With the medical implant 10 disposed about the vein “V,” the distal end portion 12b of the medical implant 10 is directly coupled to the side “AS” of the artery “A” to cover the anastomosis “0” site and fix the medical implant 10 in place. When directly connecting the medical implant 10 to the artery “A,” the distal end portion 12b of the medical implant 10 may be sutured to the artery “A.” Other mechanisms for fastening the medical implant 10 to the artery “A” are contemplated.
With the medical implant 10 in place, blood flow may be re-established, whereby the vein “V” is permitted by the medical implant 10 to expand radially-outward. The medical implant 10 exerts a threshold force oriented in a radially-inward direction to limit the amount of radial expansion of the vein “V.”
When forming the AV fistula of
When forming the AV fistula of
When forming the AV fistula of
Another method of utilizing the medical implant 100 of
As shown in
In aspects, medical implant 200 may be utilized instead of or in addition to medical implants 10, 100 to cover any of the AV fistulas described above by wrapping, in a helical manner, the medical implant 200 about the venous portion “V” and/or arterial portion “A” of the AV fistula.
With reference to
In one embodiment, an initial step in the surgical procedure involves dissection and freeing of a saphenous vein “SV.” The saphenous vein “SV” may be dissected free in standard fashion, leaving it in situ while ligating and cutting off all side branches. Since side-branch ligations that leave behind excessive tissue “stumps” may create sites of significant luminal encroachments when the medical implant is applied, the flush removal of all side branches is preferred, as noted above with respect to dissecting the vein used for an AV fistula. The second step involves testing the excised vein “SV” for potential leaks. The isolated saphenous vein “SV” may be tested by injecting cold heparinized blood or appropriate physiological buffer between 2-37 degrees Celsius to inflate the vein “SV” with a syringe from one end while the other end is occluded. Such inflation of the vein “SV” using a standard syringe can create extreme non-physiological pressures, for example, greater than about 350 mmHg, and is often a main cause of traumatic damage to the vein wall. Therefore, a modified pressure-limiting syringe may be used—one that limits the inflation pressure to a level suitable for detecting leaks, but not sufficient to cause tissue stretch damage. In embodiments, a pressure-limiting syringe that allows up to about 15 mmHg pressure, a typical physiological pressure for veins, may be used. Using this approach, observed leaks in the vein wall are readily identified and safely repaired, and the vein “SV” remains free of injury due to excessive pressurization. Lower pressure leak testing avoids damage to the intimal and subintimal layers in the vein “SV” which can occur without precaution during vein harvesting even before application of the medical implant 10. Such damage during leak testing would potentially override one of the main functions of the medical implant 10, which is to prevent intimal and subintimal damage to the vein “SV.”
The next step involves assembling the harvested vein segment and the medical implant 10, which may be done before or after suturing the vein “SV” to a coronary artery “CA” and an aortic arch “AA” of the patient. During this step, with appropriate cross clamps in place to prevent blood flow into the vein “SV,” the medical implant 10 may be gently opened along the seam 18 with a clinician's fingers, and the vein “SV” is placed within the passageway 14 of the medical implant 10. The medical implant 10 will naturally fold around the vein graft “SV” upon release of the opened seam 18. Here, care may be taken at each site of a vein side branch to align the side branch ligature with the nearest pore (open cell) 26 of the medical implant 10. This prevents and/or minimizes luminal encroachment due to ligature and side branch tissue being pinned between a stent strut of the medical implant 10 and the vein “SV.” Alternatively, opening the medical implant 10 may be assisted with the C-shaped tube 21 (
The C-shaped tube 21 is then removed axially, leaving the medical implant 10 and vein “SV” in contact to form the externally-supported venous graft. Care may be taken that the medical implant 10 externally supports/covers the entire vein graft from the aortic arch “AA” to the coronary artery anastomosis “CAA” (leaving from about 0 mm to about 1 mm gap of non-externally-supported vein “SV”). At this point, with the anastomoses complete and the medical implant 10 in place, cross clamps may be removed, and the vein “SV” is then inflated under arterial blood pressures of about 80-120 mmHg, causing the vein “SV” to contact the inner annular surface of the medical implant 10. Optional anchoring sutures may be added at the anastomoses and elsewhere to help fix the medical implant 10 in place. Any of the components described herein may be fabricated from either metals, plastics, resins, composites or the like taking into consideration strength, durability, wearability, weight, resistance to corrosion, ease of manufacturing, cost of manufacturing, and the like.
It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques).
