Systems and methods for maintaining perfusion of branch vessels

An endoluminal prosthesis comprises a graft having a tubular body comprising proximal and distal ends, inner and outer surfaces, and partially and fully deployed states. A temporary channel is disposed external to the outer surface of the graft in the partially deployed state. The temporary channel begins at one of the proximal and distal ends of the graft, and extends along only a portion of a longitudinal length of the graft. The temporary channel is removed when the graft is in a fully deployed state.

BACKGROUND

The present embodiments relate to implantable medical devices and methods, and more particularly to systems and methods for maintaining perfusions of branch vessels.

The aortic valve functions as a one-way valve between the heart and the rest of the to body. Blood is pumped from the left ventricle of the heart, through the aortic valve, and into the aorta, which in turn supplies blood to the body. Between heart contractions the aortic valve closes, preventing blood from flowing backwards into the heart.

Damage to the aortic valve can occur from a congenital defect, the natural aging process, and from infection or scarring. Over time, calcium may build up around the aortic valve causing the valve not to open and close properly. Certain types of damage may cause the valve to “leak,” resulting in “aortic insufficiency” or “aortic regurgitation.” Aortic regurgitation causes extra workload for the heart, and can ultimately result in weakening of the heart muscle and eventual heart failure.

After the aortic valve becomes sufficiently damaged, the valve may need to be replaced to prevent heart failure and death. One approach involves an invasive open procedure. However, patients undergoing such procedure are subjected to a heart-lung bypass, induced cardiac arrest, and extensive trauma to the valve and ascending aorta, and therefore morbidity and mortality rates are relatively high.

A more recent approach involves endovascularly introducing an aortic valve replacement. However, current endovascular approaches do not allow for sufficient repair of both the aortic valve and the ascending aorta, due to the complex anatomy in this region including the valvular sinus and the coronary arteries. Moreover, attempts to endovascularly repair the aortic valve and the ascending aorta may encompass risks of temporary blocking flow to the coronary arteries during the procedure, which can cause significant complications for a patient.

SUMMARY

An endoluminal prosthesis comprises a graft having a tubular body comprising proximal and distal ends, inner and outer surfaces, and partially and fully deployed states. A temporary channel is disposed external to the outer surface of the graft in the partially deployed state. The temporary channel begins at one of the proximal and distal ends of the graft, and extends along only a portion of a longitudinal length of the graft. The temporary channel is removed when the graft is in the fully deployed state.

In one embodiment, the temporary channel may begin at the distal end of the graft and terminate before the proximal end of the graft. At least one fenestration may be disposed in a sidewall of the graft between the proximal and distal ends of the graft, and a proximal end of the temporary channel may be aligned with the fenestration. A valve replacement may be disposed between the proximal and distal ends of the graft. The temporary channel may comprise a “U”-shape.

In one embodiment, a shape of the temporary channel may be maintained by securement of a first portion of the graft to a second portion of the graft, for example, using at least one suture. In other embodiments, a shape of the temporary channel may be maintained by securement of a portion of the graft to a delivery system, for example, by securing a wire extending along the delivery system to a coupling member of the graft.

In other embodiments, the temporary channel comprises a sheath having an aperture. The aperture is disposed distal to the distal end of the graft in the partially deployed state, and a portion of the sheath is disposed adjacent to the outer surface of the graft in the partially deployed state. In a further alternative, the temporary channel may comprise a removable stent framework disposed exterior to the graft.

Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be within the scope of the invention, and be encompassed by the following claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present application, the term “proximal” refers to a direction that is generally closest to the heart during a medical procedure, while the term “distal” refers to a direction that is furthest from the heart during a medical procedure.

Referring toFIGS. 1-5, an endoluminal prosthesis10is shown and described. The prosthesis10comprises a graft20having a tubular body comprising proximal and distal ends22and24, and a lumen18extending therebetween.

The prosthesis10comprises a valve60disposed between the proximal end22and the distal end24of the graft20. In one example, the valve60can be coupled to the graft20with sutures.

In one non-limiting example, the valve60may comprise an aortic valve designed to replace the function of the recipient's native damaged or poorly performing aortic valve. In other examples, the prosthesis10may be deployed in other arterial locations, i.e., other than the aortic annulus and ascending aorta, or alternatively may be deployed in a patient's venous system, or any suitable duct, passageway or vessel.

In the non-limiting example of an aortic valve, the valve60may be located at the proximal end22of the graft20, closest to the heart. The valve60preferably includes one or more leaflets62, as shown inFIGS. 2A-2B. In this non-limiting example, the valve60includes three leaflets62, though only two leaflets may be used in a “bicuspid” arrangement. The leaflets are arranged in the prosthesis such that the leaflets mimic a naturally occurring aortic valve. The valve60“opens” to allow blood flow when the pressure on the proximal side of the valve60is greater than pressure on the distal side of the artificial valve. Thus, the valve60regulates the unidirectional flow of fluid from the heart into the aorta.

The leaflets of the valve60can be fabricated from any at least substantially biocompatible material including such materials as polyester fabrics, polytetrafluoroethylene (PTFE), expanded PTFE, and other synthetic materials known to those of skill in the art. Preferably, the leaflets are fabricated from naturally occurring biomaterials. The leaflets can include a derived collagen material, such as an extracellular matrix. The extracellular matrix can be small intestinal submucosa, stomach submucosa, pericardium, liver basement membrane, urinary bladder submucosa, tissue mucosa, dura mater, or the like.

The prosthesis10further comprises at least one stent coupled to the graft20that has a contracted delivery state and further has an expanded state for maintaining patency within a portion of the graft. In the exemplary embodiment depicted inFIGS. 1 and 5, five exemplary stents16a-16eare provided. The stents16may be placed on the outer surface and/or inner surface of the graft20. The exemplary stents16of the prosthesis10may comprise zig-zag stents or another suitable structure, and may be either self-expanding or balloon expandable.

In the embodiment ofFIG. 1, a first stent16ais located at the proximal end of the graft20. In use, the first stent16aoverlaps with an aortic annulus97, as shown inFIG. 5. The first stent16amay comprise a radial force configured to facilitate fixation within the aortic annulus97and prevent migration of the proximal end22of the graft20. One or more barbs25may be coupled to the first stent16ato reduce migration of the prosthesis10.

In the example ofFIG. 1, the endoluminal prosthesis10comprises second and third z-stents16band16c, which are coupled to the graft20such that the distal apices of the second stent16bare aligned with the proximal apices of the third stent16c. The fifth stent16emay be configured to engage a healthy portion of a patient's ascending aorta98, as depicted in the deployed state ofFIG. 5.

The endoluminal prosthesis10further comprises at least one fenestration12disposed in a sidewall74of the graft20. The one or more fenestrations12may be positioned between a proximal apex of the second stent16band a distal apex of the third stent16c. In the embodiment ofFIGS. 1-5, first and second fenestrations12aand12bare disposed in the sidewall74at locations distal to the valve60, as seen in the top view ofFIG. 2A.

The first and second fenestrations12aand12bmay be provided in accordance with pivoting fenestrations described in detail in U.S. Patent Application Publication Number 2012/0046728, which is hereby incorporated by reference in its entirety. Accordingly, at least one of the fenestrations12aand12bis pivotable in any direction away from an axis perpendicular to a longitudinal axis of the prosthesis. In the non-limiting example ofFIG. 1, the first and second fenestrations12aand12bare disposed in the graft20at locations between about 90 and about 270 degrees apart, though the positioning may be greater or less. In the deployed state, a first branch vessel prosthesis92amay extend between the first fenestration12aand a first coronary artery95ain a deployed state, and a second branch vessel prosthesis92bmay extend between the second fenestration12band a second coronary artery95b, when the prosthesis10is used to repair an aortic valve, as shown inFIG. 5.

In the examples ofFIGS. 1-5, the deployment of the prosthesis10into the state shown inFIG. 5may be achieved in different manners. In one example, the deployment may be made using a transapical or transeptal approach, in which case the prosthesis10may be secured to an exemplary delivery system70as shown inFIG. 3. In the transapical or transeptal approach, an atraumatic tip72of the delivery system is advanced in an antegrade fashion, i.e., in a direction from the aortic annulus97towards the ascending aorta98.

In another example, the deployment may be made using a femoral, carotid, subclavian or axiliary approach, in which case the prosthesis10may be secured to the exemplary delivery system70as shown inFIG. 4. In this approach, the atraumatic tip72of the delivery system70is advanced in a retrograde fashion, i.e., in a direction from the ascending aorta98towards the aortic annulus97. In either delivery approach, as shown inFIGS. 3-4, the graft20may comprise one or more regions73that are radially restrained.

Access to the branch vessels95aand95b, such as the coronary arteries, may be provided through the use of a delivery device, such as a catheter. Once a catheter is placed within the branch vessel95a, a distal portion of the branch vessel prosthesis92amay be deployed within the branch vessel95avia balloon expansion or self-expansion into engagement with the branch vessel95a. Then, a proximal end of the branch vessel prosthesis92a, remaining within the interior surface of the prosthesis10, may be flared in order to provide a proper seal between the fenestration12aand the branch vessel95a. The second branch vessel prosthesis92bmay be coupled between the prosthesis10and the second branch vessel95bin a similar manner.

Further, the prosthesis10may be provided as part of a preloaded system that includes a guide wire75. In this example, a first end segment76of the guide wire75may enter the lumen18through a proximal or distal end of the prosthesis10, depending on the delivery orientation of the prosthesis shown inFIG. 3as compared toFIG. 4. The first end segment76exits the graft20through the first fenestration12a. An intermediate segment of the guide wire75may extend external of the graft20and reenter the lumen18of the prosthesis10through the second fenestration12b. A second end segment77of the guide wire75may extend distally within the lumen18and may extend distally to the distal end of the delivery device70. The first end segment76of the guide wire75may enable introduction of the first branch prosthesis92ainto the first fenestration12ato couple the prosthesis10to the right coronary artery, and the second end segment77of the guide wire75may enable introduction of the second branch prosthesis92binto the second fenestration12bto couple the prosthesis to the left coronary artery.

Further details of such a preloaded wire, and how it may facilitate deployment of stent-grafts into branch vessels, are described in further detail in U.S. Utility patent application Ser. No. 13/718,915, filed Dec. 18, 2012, which is hereby incorporated by reference in its entirety. While one exemplary delivery system has been shown, it will be appreciated that a number of delivery systems and techniques may be used to deploy the prosthesis10.

In the deployed state, the first branch vessel prosthesis92aextends between the first fenestration12aand the first coronary artery95a, and the second branch vessel prosthesis92bextends between the second fenestration12band the second coronary artery95b, as depicted inFIG. 5. Advantageously, if the first and second fenestrations12aand12bare not exactly aligned with their respective coronary arteries95aand95bfor any reason, such as variable patient anatomy, then the pivoting features of the fenestrations12aand12bprovide the requisite flexibility to allow the branch vessel prostheses92aand92bto deploy into the desired position.

The branch vessel prostheses92aand92bmay be formed from biocompatible materials and may comprise covered stents. Alternatively, they may comprise bare stents. The covered or bare stents may be either self-expanding or balloon expandable. In one embodiment, the branch vessel prostheses92aand92bmay have both self-expanding and balloon expandable components. If either of the branch vessel prostheses92aand92bcomprises a covered stent, the graft material used may comprise one or more of the biocompatible materials are discussed above.

Referring now toFIGS. 6A-6C, a first embodiment of a system100for maintaining perfusion of branch vessels is shown and described. The prosthesis10and the delivery system70, described inFIGS. 1-5above, may be used in conjunction with the system100ofFIGS. 6A-6C. It should be noted that in the embodiment ofFIGS. 6A-6C, as well as the embodiments ofFIGS. 7-9below, the stents16a-16ecoupled to the prosthesis10—have been omitted for illustrative purposes to show further features associated withFIGS. 6-9.

In the embodiment ofFIGS. 6A-6C, the system100comprises at least one temporary channel120, which is formed external to the graft20. In the example ofFIGS. 6A-6C, two temporary channels120are shown, one being aligned with the fenestration12aand the first coronary artery95a, and the other being aligned with the fenestration12band the second coronary artery95b, as shown inFIG. 6A.

Each temporary channel120is disposed external to the outer surface of the graft20when the graft20is in a partially deployed state, i.e., other than the fully deployed state ofFIG. 6C. The temporary channel120begins at one of the proximal and distal ends22and24of the graft20, and extends along only a portion of a longitudinal length of the graft20. In the example ofFIGS. 6-9, the temporary channel120begins at the distal end24of the graft20, and is disposed at a location between the distal end24of the graft20and one of the fenestration12. The temporary channel120is removed when the graft20is in a fully deployed state as shown inFIG. 6C.

The temporary channels120may be formed by coupling a portion of the graft20to a portion of the delivery system70. For example, a coupling member131in the form of a loop may be secured to the distal end24of the graft20, and a wire132may be releasably coupled to the coupling member131, e.g., disposed through the loop. In one example, the wire132may extend along a full length of the delivery system70, within a catheter71, and may exit the catheter71through a first aperture79a, then engage the coupling member131, and then enter back into the catheter71through a second aperture79bthat is disposed proximal to the first aperture79a, as depicted inFIG. 6B. By holding a portion of the graft20to the delivery system70, via the coupling member131, the temporary channel120is formed and may comprise a generally “U”-shaped channel external to the graft20, as shown inFIG. 6A.

In use, the prosthesis10is generally delivered and at least partially deployed into the state shown inFIG. 6A, as described above with respect toFIG. 5. Prior to coupling the branch vessel prostheses92aand92bbetween their respective fenestrations12aand12band coronary arteries95aand95b, the temporary channels120provide perfusion pathways for fluid flow into the coronary arteries95aand95b. In particular, blood may flow in an antegrade manner through the valve60and the graft20, and then flow in a retrograde manner into the temporary channels120and into the coronary arteries95aand95b. Advantageously, flow may be maintained to the coronary arteries during the endovascular procedure, even though the branch vessel prostheses92aand92bhave not yet been set in place.

When a physician is ready to introduce or deploy the branch vessel prostheses92aand92bto complete the procedure, then the temporary channels120may be removed. In the example ofFIGS. 6A-6B, the wire132may be withdrawn distally beyond the coupling member131, thereby allowing the associated portion of the graft20to self-expand without restraint into full engagement with the ascending aorta98, as shown inFIG. 6C. Final placement of the branch vessel prostheses92aand92binto their respective coronary arteries95aand95bthen may be completed as described above.

Alternatively, the physician may fully deploy the branch vessel prostheses92aand92binto their respective coronary arteries95aand95b, even before removing the temporary channels120. If the system100comprises a preloaded delivery system as described above, then it may be easier to deploy the branch vessel prostheses92aand92beven when the temporary channel120occupies a portion of the ascending aorta98.

Referring now toFIGS. 7A-7B, an alternative system200for maintaining perfusion of branch vessels is shown and described. The system200is similar to the system100ofFIGS. 6A-6B, with a main exception that the graft20is secured to itself to form one or more temporary channels120, as opposed to being secured to the delivery system70in the example ofFIGS. 6A-6B.

In one non-limiting example, the system200comprises at least one suture231that is secured to the graft20in a manner that forms the shape of the temporary channel120. For example, the suture231may be secured near the distal end24of the graft20between spaced-apart first and second locations233and234, as depicted inFIG. 7B. The dimensions of the suture231and its placement relative to locations233and234produces a tension that maintains the temporary channel120until the suture231is released. In one embodiment, multiple sutures231may be longitudinally spaced apart between the distal end24of the graft20and the fenestration12b, thereby maintaining the temporary channel120for a desired longitudinal distance between these locations. The temporary channel120may comprise a generally “U”-shaped channel external to the graft20, as shown inFIGS. 7A-7B.

As an alternative placement, the suture231may extend across the lumen18of the prosthesis10, e.g., sewn to distal ends of the graft20at two locations spaced apart about 180 degrees. Such a suture across the lumen18may hold opposing sides of the graft20at a tension that maintains two temporary channels120in place, in the manner shown inFIG. 7A, until the suture is released.

As with the prior embodiment ofFIGS. 6A-6C, flow may advantageously be maintained to the coronary arteries during the endovascular procedure, even though the branch vessel prostheses92aand92bhave not yet been set in place. When a physician is ready to introduce or deploy the branch vessel prostheses92aand92bto complete the procedure, then the temporary channel120may be withdrawn by removal of the suture231. In one embodiment, the delivery system70may comprise a balloon, and radially outward expansion of the balloon against the suture231may cause breakage of the suture231, thereby allowing the associated portion of the graft20to self-expand without restraint into full engagement with the ascending aorta98, as shown inFIG. 6C. Alternatively, the suture231may comprise a biodegradable material and may dissolve after a predetermined period of time, thereby allowing the associated portion of the graft20to self-expand without restraint into full engagement with the ascending aorta98. As a further alternative, a trigger wire may be used to remove the suture231, in a manner similar to that shown inFIGS. 6A-6Babove. In any of these techniques, flow is advantageously maintained to the coronary arteries in the interim period required to ensure placement of the branch vessel prostheses92aand92b.

Moreover, in the embodiment ofFIGS. 7A-7B, in the event that the branch vessel prostheses92aand92bcannot be placed into their respective coronary arteries95aand95bduring an initial procedure, it is possible that the branch vessel prostheses92aand92bmay be deployed at a later time in a subsequent procedure. In the interim, one or more sutures231may maintain the temporary channel120to allow sufficient retrograde flow into the coronary arteries95aand95bto help sustain the patient while awaiting implantation of the branch prostheses92aand92b.

Referring now toFIG. 8, an alternative system300for maintaining perfusion of branch vessels is shown and described. The system300comprises at least one sheath310having a proximal end314, and a distal end (not shown) extending outside of the patient's body. At least one aperture312is formed between the proximal and distal ends of the sheath310. The proximal end314of the sheath310may be advanced into one of the patient's coronary arteries, as depicted inFIG. 8. The sheath310may be delivered via any suitable vessel, including but not limited to the brachiocephalic artery.

The aperture312of the sheath310is disposed distally beyond the distal end24of the graft20, as the prosthesis10is being implanted. At least a portion of the sheath310is disposed adjacent to an exterior surface of the graft20while the prosthesis10is being implanted, and before the branch vessel prostheses95aand95bare introduced into their respective coronary arteries. In this manner, blood may flow through the valve60, through the graft20, and into the aperture312, and then flow in a retrograde manner through the sheath310and into the coronary artery.

As with the prior embodiments ofFIGS. 6-7, flow may advantageously be maintained to the coronary arteries during the endovascular procedure, even though the branch vessel prostheses92aand92bhave not yet been set in place. When a physician is ready to introduce or deploy the branch vessel prostheses92aand92bto complete the procedure, or after the branch vessel prostheses92aand92bhave been fully implanted, then the sheath310may be withdrawn from the patient.

Referring now toFIG. 9, an alternative system400for maintaining perfusion of branch vessels is shown and described. The system400comprises at least one external support410. In this embodiment, the external support410is in the form of a stent framework411having proximal and distal ends412and414, respectively. The stent framework411is disposed adjacent to the outer surface of the graft20in a manner such that it forms the shape of the temporary channel120. For example, the distal end414of the stent framework411may be disposed near the distal end24of the graft20, and the proximal end412of the stent framework411may be disposed a short distance distal to the fenestration12b, as depicted inFIG. 9. The external support410may be deployed in conjunction with, or before, the partial deployment of the graft20as shown inFIG. 9.

In this manner, at least a portion of the external support410is disposed adjacent to an exterior surface of the graft20while the prosthesis10is being implanted, and before the branch vessel prostheses95aand95bare introduced into their respective coronary arteries. Accordingly, blood may flow through the valve60, through the graft20, and then flow in a retrograde manner through the support410and into the coronary artery.

As with the prior embodiments ofFIGS. 6-8, flow may advantageously be maintained to the coronary arteries during the endovascular procedure, even though the branch vessel prostheses92aand92bhave not yet been set in place. When a physician is ready to introduce or deploy the branch vessel prostheses92aand92bto complete the procedure, or after the branch vessel prostheses92aand92bhave been fully implanted, then the support410may be withdrawn from the patient.

The support410may be removed using a suitable technique such as pulling on a drawstring-like element to induce contraction of the support410to a smaller diameter and subsequent capture by a removal sheath. Alternatively, the distal end414of the support410may extend distally beyond the graft20such that the distal end414remains secured to the delivery device70throughout the procedure at a location distal to the graft20, and then distal removal of the delivery device70(after placement of the branch vessel prostheses92aand92b) achieves a corresponding distal removal of the support410.

In the embodiment ofFIG. 9, as with the embodiment ofFIGS. 7A-7Babove, in the event that the branch vessel prostheses92aand92bcannot be placed into their respective coronary arteries95aand95bduring an initial procedure, it is possible that the branch vessel prostheses92aand92bmay be deployed at a later time in a subsequent procedure. In the interim, the support410may maintain a temporary channel to allow sufficient retrograde flow into the coronary arteries95aand95bto help sustain the patient's health.

As noted above, while one exemplary use of the prosthesis10has been shown with regard to the aortic annulus and ascending aorta for maintaining flow into the coronary arteries, the prosthesis10alternatively may be deployed in other parts of a patient's arterial or venous system, or any suitable duct, passageway or vessel, and the various systems100,200,300and400may maintain flow into branch vessels other than the coronary arteries depending on use of the prosthesis10.

While various embodiments of the invention have been described, the invention is not to be restricted except in light of the attached claims and their equivalents. Moreover, the advantages described herein are not necessarily the only advantages of the invention and it is not necessarily expected that every embodiment of the invention will achieve all of the advantages described.