Patent Application
20090264988
The present invention relates generally to methods and systems for delivering a graft through a body lumen for the treatment of vascular disease.
Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts constructed of biocompatible materials, such as Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing, have been employed to replace or bypass damaged or occluded natural blood vessels. In general, endovascular grafts typically include a graft anchoring component that operates to hold the tubular graft in its intended position within the blood vessel. Most commonly, the graft anchoring component is one or more radially compressible stents that are radially expanded in situ to anchor the tubular graft to the wall of a blood vessel or anatomical conduit. Thus, endovascular grafts are typically held in place by mechanical engagement and friction due to the opposition forces provided by the expandable stents.
In general, rather than performing an open surgical procedure to implant a bypass graft that may be traumatic and invasive, stent grafts are preferably deployed through a less invasive intraluminal delivery. More particularly, a lumen or vasculature is accessed percutaneously at a convenient and less traumatic entry point, and the stent graft is routed through the vasculature to the site where the prosthesis is to be deployed. Intraluminal deployment is typically effected using a delivery catheter with coaxial inner and outer tubes arranged for relative axial movement. For example, a self-expanding stent graft may be compressed and disposed within the distal end of an outer catheter tube distal of a stop fixed to the inner member. The catheter is then maneuvered, typically routed though a body lumen until the end of the catheter and the stent graft is positioned at the intended treatment site. The stop on the inner member is then held stationary while the outer tube of the delivery catheter is withdrawn. The inner member prevents the stent graft from being withdrawn with the sheath. As the sheath is withdrawn, the stent graft is released from the confines of the sheath and radially self-expands so that at least a portion of it contacts and substantially conforms to a portion of the surrounding interior of the lumen, e.g., the blood vessel wall or anatomical conduit.
Grafting procedures are also known for treating aneurysms. Aneurysms result from weak, thinned blood vessel walls that “balloon” or expand due to aging, disease and/or blood pressure in the vessel. Consequently, aneurysmal vessels have a potential to rupture, causing internal bleeding and potentially life threatening conditions. Grafts are often used to isolate aneurysms or other blood vessel abnormalities from normal blood pressure, reducing pressure on the weakened vessel wall and reducing the chance of vessel rupture. As such, a tubular endovascular graft may be placed within the aneurysmal blood vessel to create a new flow path and an artificial flow conduit through the aneurysm, thereby reducing if not nearly eliminating the exertion of blood pressure on the aneurysm.
While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries. Depending on the region of the aorta involved, the aneurysm may extend into areas of bifurcation or segments of the aorta from which smaller “branch” arteries extend. Various types of aortic aneurysms may be classified on the basis of the region of aneurysmic involvement. For example, thoracic aortic aneurysms include aneurysms present in the ascending thoracic aorta, the aortic arch, and branch arteries that emanate therefrom, such as subclavian arteries. Thoracoabdominal aortic aneurysm include aneurysms present in the descending thoracic aorta and branch arteries that emanate therefrom, such as thoracic intercostal arteries and/or the suprarenal abdominal aorta and branch arteries that emanate therefrom, such as renal, superior mesenteric, celiac and/or intercostal arteries. Lastly, abdominal aortic aneurysms include aneurysms present in the pararenal aorta and the branch arteries that emanate therefrom, such as the renal arteries.
Unfortunately, not all patients diagnosed with aortic aneurysms are presently considered candidates for endovascular grafting. This is largely due to the fact that most of the endovascular grafting systems of the prior art are not designed for use in regions of the aorta from which side branches extend. The deployment of endovascular grafts within regions of the aorta from which branch arteries extend present additional technical challenges because, in those cases, the endovascular graft must be designed, implanted and maintained in a manner which does not impair the flow of blood into the branch arteries.
In order to accommodate side branches, a stent graft having a fenestration or opening in a side wall thereof is utilized. The fenestration is positioned to align with the ostium of the branch vessel after deployment of the stent graft. In use, the proximal end of the graft having one or more side openings is securely anchored in place, and the fenestrations or openings are configured and deployed to avoid blocking or restricting blood flow into the side branches. In some cases, another stent graft, often referred to as a branch graft, may then be deployed through the fenestration into the branch vessel to provide a path for blood flow to the branch vessel. One issue that exists in such a procedure is how to accurately position a fenestration creating element in relation to the branch vessel. If the position of a fenestration is offset with respect to a branch vessel when the stent graft is deployed, it may be difficult to deploy guidewires and catheters from the stent graft into the branch vessel to enable correct positioning of the branch vessel stent graft, which in turn may result in the branch graft being deployed in such a manner that it kinks to such an extent that blood flow will not occur therethrough. Thus, there remains a need in the art for the development of new endovascular grafting systems and methods for providing perfusion to side branch vessels.
A system and method in accordance with an embodiment hereof includes a graft delivery system for delivering a stent graft within a segment of a body vessel having a branch vessel extending therefrom. The graft includes an intermediate, unsupported or stent-free body portion positionable across the branch vessel with one or more self-expanding stents provided at a proximal and/or distal end thereof for anchoring the graft to a vessel wall. The delivery system includes an expandable fenestration support structure at the distal end thereof that is positioned within the graft during delivery. Once the graft has been delivered and expanded into apposition with the vessel wall, the fenestration support structure may be expanded therein to press the otherwise unsupported body portion of the graft against the branch vessel, such that a separate puncture device may be delivered to create a fenestration in the side of the graft for perfusion of the branch vessel. The unsupported body portion of the graft is thus temporarily held in place by the expanded fenestration support structure until the fenestration is created. Thus, the expanded fenestration support structure of the graft delivery system facilitates fenestration in situ by providing radial support to the graft for branch fenestration operations. In addition, the expanded fenestration support structure models or reduces the wrinkles of the graft without a secondary procedure.
The foregoing and other features and advantages will be apparent from the following description as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of embodiments according to the present invention. The drawings are not to scale.
Specific embodiments are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician. For the graft the proximal end refers to the end of the graft material nearest the heart by way of blood flow path, while distal is the end farthest from the heart by way of blood flow path.
The following detailed description is merely exemplary in nature. Although the description herein is in the context of treatment of blood vessels such as the coronary, carotid and renal arteries, embodiments according to the present invention may also be used in any other body passageways where it is deemed useful. Further details and description of embodiments are provided below with reference to
As shown in
In an un-retracted, distally extended position, retractable sheath 106 restrains a self-expanding graft in a constrained diameter or delivery configuration within distal end 110 thereof. Retractable sheath 106 extends to proximal portion 102 of system 100 and is movable in an axial direction along and relative to intermediate shaft 114 via an actuator, such as a handle 112, to selectively release the graft located about distal portion 104 of system 100. Handle 112 may be a push-pull actuator that is attached or connected to proximal end 108 of retractable sheath 106. In order to allow expansion of the graft, handle 112 is pulled proximally relative to intermediate shaft 114 to retract sheath 106. Alternatively, the actuator may be a rotatable knob (not shown) that is attached or connected to proximal end 108 of retractable sheath 106, such that when the knob is rotated retractable sheath 106 is retracted in a proximal direction to allow expansion of the graft. Thus, when the actuator is operated, i.e., manually turned or pulled, retractable sheath 106 is proximally retracted relative to intermediate shaft 114.
Inner shaft 122 is also movable in an axial direction along and relative to intermediate shaft 114 and extends to proximal portion 102 of system 100 where it may be controlled via a handle 128 to selectively expand an expandable fenestration support structure 132. Expandable fenestration support structure 132 is located at distal portion 104 of system 100, and includes a tubular braided structure or mesh 134. As explained in more detail herein with reference to
A proximal end 136 of fenestration support structure 132 is attached to distal end 118 of intermediate shaft 114, and a distal end 138 of fenestration support structure 132 is attached to distal end 126 of inner shaft 122. While holding proximal end 116 of intermediate shaft 114 fixed, inner shaft 122 may be proximally retracted via handle 128 within intermediate shaft 114. When inner shaft 122 is proximally retracted, the attachment point between fenestration support structure 132 and intermediate shaft 114 remains fixed such that fenestration support structure 132 radially expands. Fenestration support structure 132 may be attached to intermediate shaft 114 and inner shaft 122 in any suitable manner known in the art. For example, the connection may be formed by welding, such as by resistance welding, friction welding, laser welding or another form of welding such that no additional materials are used to connect fenestration support structure 132 to shafts 114, 122. Alternatively, fenestration support structure 132 can be connected to shafts 114, 122 by soldering, by the use of an adhesive, by the addition of a connecting element there between, or by another mechanical method.
Similar to handle 112 explained above, handle 128 may be a push-pull actuator that is attached or connected to proximal end 124 of inner shaft 122 to expand fenestration support structure 132 such that when handle 128 is pulled while holding proximal end 116 of intermediate shaft 114 fixed, inner shaft 122 is retracted in a proximal direction to expand fenestration support structure 132. Similarly, when handle 128 is pushed while holding proximal end 116 of intermediate shaft 114 fixed, inner shaft 122 is advanced in a distal direction to elongate or unexpand fenestration support structure 132 to allow for removal. Alternatively, the actuator may be a rotatable knob (not shown) that is attached or connected to proximal end 124 of inner shaft 122 such that when the knob is rotated, inner shaft 122 operates to expand or elongate fenestration support structure 132. Thus, when the actuator is operated, i.e., manually turned or pulled, inner shaft 122 is proximally retracted within intermediate shaft 114. Although embodiments are described with inner shaft 122 being movable relative to intermediate shaft 114 to expand fenestration support structure 132, it should be apparent to one of ordinary skill in the art that fenestration support structure 132 is expanded by shortening the distance between ends 136, 138 thereof. Thus, in another embodiment, fenestration support structure 132 may be expanded by distally advancing intermediate shaft 114 while holding inner shaft 122 stationary.
Referring now to
As shown in
Stents for use herein are preferably self-expanding spring members that are deployed by release from a restraining mechanism such as retractable sheath 106. For example, the stents may be constructed of a superelastic material such as nitinol. The stents may have any suitable configuration. For example, the stents may be wavelike or sinusoidal patterned wire rings, a series of connected compressible diamond structures or other compressible spring members biased in a radially outward direction, which when released, bias the prosthesis into conforming fixed engagement with an interior surface of the vessel. Examples of such annular support members are described, for example, in U.S. Pat. No. 5,713,917 and U.S. Pat. No. 5,824,041, which are incorporated by reference herein in their entirety. When used in an aneurysm exclusion device, the stents have sufficient radial spring force and flexibility to conformingly engage the prosthesis with the body lumen inner wall, to avoid excessive leakage, and prevent pressurization of the aneurysm, i.e., to provide a leak-resistant seal. Although some leakage of blood or other body fluid may occur into the aneurysm isolated by the graft prosthesis, an optimal seal will reduce the chances of aneurysm pressurization and resulting rupture.
Similarly,
Retractable sheath 106, intermediate shaft 114, and inner shaft 122 may be constructed of any suitable flexible polymeric material. Non-exhaustive examples of material for the catheter shafts are polyethylene terephalate (PET), nylon, polyethylene, PEBAX, or combinations thereof, either blended or co-extruded. Optionally, a portion of the catheter shafts may be constructed as a composite having a reinforcement material incorporated within a polymeric body to enhance strength, flexibility, and/or toughness. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. In an embodiment, the proximal portions of the catheter shafts may in some instances be constructed from a reinforced polymeric tube, for example, as shown and described in U.S. Pat. No. 5,827,242 to Follmer et al. which is incorporated by reference herein in its entirety. The catheter shafts may have any suitable working length, for example, 550 mm-600 mm, to extend to a target location where a graft is to be implanted.
Fenestration support structure 132 has sufficient mechanical strength to press at least a portion of the graft to a vessel wall of a body lumen. In another embodiment, fenestration support structure 132 may be constructed from a tubular braided structure including a plurality of metallic wires or polymeric filaments woven together to form a tubular structure. Non-exhaustive examples of metallic materials for fenestration support structure 132 are stainless steel, cobalt based alloys (605L, MP35N), titanium, tantalum, ceramic, and superelastic nickel-titanium alloy, such as nitinol. Non-exhaustive examples of polymeric materials for fenestration support structure 132 are polyurethane, polyethylene terephalate (PET), nylon, polyethylene, PEBAX, or combinations thereof, either blended or co-extruded.
The fenestration support structure can be used with electrically conductive or high temperature graft puncture devices whose use is described below. In instances where an electrically conductive puncture device such as RF or plasma utilizing wires or electrodes as are used to create a localized area or volume of graft material vaporizing energy, or resistive heating elements which provide a localized melt cutting of the graft material, the wires and or other elements of the fenestration support structure can be coated to prevent grounding or errant conduction of electricity or electric fields or currents away from the wire or electrodes. Such coatings may be non-conductive ceramic, polyimide Kapton, hi-temp Parylene, or other heat resistant dielectric material which can form a coating. Coating thicknesses of approximately 0.001 inches have been found to be sufficient. A source for useful parylene coatings is Specialty Coating Systems, of Indianapolis, Ind.
Graft 540 is a tubular synthetic graft constructed from a suitable biocompatible material such as DACRON or other polyester fabric, or PTFE (polytetrafluoroethylene). The graft material is thin-walled so that graft 540 may be compressed into a small diameter, yet is capable of acting as a strong, leak-resistant fluid conduit when expanded to a cylindrical tubular form. In one embodiment, unsupported intermediate portion 544 of graft 540 may include a printed pattern of radiopaque markings to delineate the surface of the graft cloth radiographically as described in U.S. patent application Ser. No. ______, filed ______ (Atty Docket No, P30242), which is herein incorporated by reference in its entirety. Such radiopaque markings will assist in creating the fenestration in the graft to allow blood flow into the side branch vessels.
Referring now to
When a distal portion of the graft delivery system is located at the deployment site, retractable sheath 106 is proximally retracted to allow the graft to self-expand into apposition with the vessel wall. As shown in
As shown in
The expanded fenestration support structure 132 provides support for unsupported body portion 544 of graft 540 such that a fenestration may be created in situ to perfuse side branch vessels 868. As shown in
If desired, puncture device 1170 may then moved to a second side branch vessel in need of perfusion, and the process is repeated to create additional fenestrations in the side wall of graft 540. Once fenestrations have been created in graft 540 as desired, puncture device 1170 is removed. Fenestration support structure 132 may then be collapsed to an unexpanded straightened configuration by distally advancing the inner shaft as described above, and the graft delivery system may be retracted and removed from the patient. Graft 540 remains expanded in the vessel against the vessel wall to provide an artificial lumen for the flow of blood.
While various embodiments have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope thereof. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.
