Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent in combination with graft
Reexamination Certificate
1999-06-21
2002-06-04
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent in combination with graft
C606S108000
Reexamination Certificate
active
06398802
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to endoluminal grafts or “stents” and, more specifically, to a stent delivery system or “introducer” for deploying a stent inside of a prosthetic graft without interrupting fluid flow during deployment and a method for such deployment.
BACKGROUND OF THE INVENTION
A stent is an elongated device used to support an intraluminal wall. In the case of a vascular stenosis, a stent provides an unobstructed conduit for blood in the area of the stenosis. An intraluminal prosthesis may comprise a stent that carries a prosthetic layer of graft material. Such a prosthesis may be used, for example, to treat a vascular aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Typically, an intraluminal stent or prosthesis is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called “minimally invasive techniques” in which the stent, restrained in a radially compressed configuration by a sheath or catheter, is delivered by a stent deployment system or “introducer” to the site where it is required. The introducer may enter the body through the patient's skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. When the introducer has been threaded into the body lumen to the stent deployment location, the introducer is manipulated to cause the stent to be released from the surrounding sheath or catheter in which it is restrained (or alternatively the surrounding sheath or catheter is retracted from the stent), whereupon the stent expands to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stents are typically expanded by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration.
Referring now to a stent deployment system of the prior art in
FIG. 1
, there is shown an endoluminal prosthesis
10
comprising a wire stent
12
affixed along its length to an outer graft cover
14
, the graft and stent compressed inside outer sheath
16
(shown in cross-section). During the deployment process of endoluminal prosthesis
10
in a body lumen
20
, such as a blood vessel, outer sheath
16
is retracted, and stent
12
expands against the walls
19
of the lumen
20
(shown in cross-section). During the expansion process, the partially-deployed, covered section
22
at distal end
23
and middle section
25
of integral stent/graft prosthesis
10
can block the flow of blood along arrow A temporarily until proximal end
24
is released from the sheath. As used herein, “proximal” is defined as meaning “closer to the end of the introducer remaining outside the body”, whereas “distal” is defined as meaning “farther from the end of the introducer remaining outside the body”. During deployment, the pressure of obstructed blood flow at covered section
22
may cause the prosthesis to migrate away from its intended location or become longitudinally compressed. If for some reason the deployment procedure becomes protracted, the blood flow blocked by covered section
22
may impart serious stress upon the patient. Thus, it is desirable to provide for unobstructed blood flow throughout the stent deployment process.
A construction known to the inventor prior to this invention comprises a device shown in
FIG. 2
comprising stent
12
′ and outer graft cover
14
′ joined by a connection
30
to stent
12
′ proximal the distal end
23
thereof. Prior to deployment, stent
12
′ and graft liner
14
′ are restrained in a compressed configuration by an outer sheath
16
′ surrounding both the stent and the liner, and by an inner sheath
38
disposed between stent
12
′ and liner
14
′ proximally of connection
30
. Deployment of this prosthesis is effected by first retracting outer sheath
16
′, allowing distal portion of stent
12
′ and then cover
14
′ to fully expand independently. Stent
12
′ is subsequently fully expanded proximal of the connection point by retracting inner sheath
38
. During deployment of this device, blood flow can continue as indicated by arrows B.
The introducer construction having two sheaths as described above necessarily requires an introducer of somewhat larger diameter and lesser flexibility than most such introducers known in the art having only a single sheath.
SUMMARY OF THE INVENTION
The present invention provides a flexible, single-sheath, low-profile delivery system for deployment of a stent inside of a biocompatible graft cover in a distal deployment location in a body lumen from a proximal access location outside the body lumen. The delivery system comprises a stent sheath having a distal end located upstream relative to the fluid flow; a compressed stent underlying the stent sheath, the stent having a proximal end housed within the stent sheath and a distal end; and a compressed biocompatible graft cover overlying the stent sheath along the length of the stent and releasably retained in a compressed state surrounding the sheath. The graft has a distal end attached to the stent at or proximal the stent distal end and an outer surface exposed to the interior space of the lumen during deployment. The stent distal end may be spaced distally from the stent sheath distal end and graft attachment, in which case the delivery system may further comprise a tip sheath overlying the stent distal end and an inner core, optionally having a guidewire lumen therein, attached to the tip and extending axially through the stent. A pusher underlies the stent sheath proximal the stent. The pusher distal end may be rounded. The inner core and attached tip sheath may be attached distally to the pusher, or the pusher may have an inner lumen extending axially therethrough, wherein the inner core extends axially through the pusher inner lumen.
The stent delivery system further may comprise a temporary, protective wrapper over the biocompatible graft, the wrapper adapted to be removed prior to insertion of the delivery system into the body lumen. The compressed biocompatible graft may further comprise a proximal end attached to the stent sheath by a releasable attachment, such as a suture, adapted to be released during deployment of the stent. The suture may be adapted for release by being secured with a slip-knot adapted to be untied during stent deployment, by the delivery system further comprising a balloon adapted for breaking the suture upon inflation of the balloon, or by the pusher further comprising a cutter, such as a sharpened hypotube, adapted for severing the suture upon movement of the pusher relative to the stent sheath.
Specifically, the stent sheath may have a suture connection point, such as a pair of tie-holes, in its circumference and radially-opposite first and second through-holes, with the pusher having a window in its distal end aligned with the stent sheath through-holes and having the cutter proximally located therein. In such a configuration, the opposite ends of the suture are attached to the suture connection point, and an intermediate section of the suture is threaded through the graft in one or more locations, through the sheath through-holes, and through the pusher window.
The invention further comprises a method for endoluminally deploying a stent and overlying biocompatible graft cover without obstructing fluid flow during deployment, as follows. First, the stent and graft are compressed and loaded into a single-sheath-profile stent delivery system as described herein. Then, the stent delivery system is inserted into a body lumen and navigated through the lumen until the stent is at a desired deployment location. Next, the stent sheath is proximally displaced relative to the stent distal end, the stent distal end becomes expanded, and endoluminal fluid flows between the stent sheath and the graft so that the graft becomes radially distanced from the stent sheath. Finally,
McDermott Corrine
Phan Hieu
Ratner & Prestia
Scimed Life Systems Inc.
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