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Cea system and method for delivering a self-expanding stent

Cea system and method for delivering a self-expanding stent description/claims

This application is a divisional application of U.S. application Ser. No. 11/304,256 filed on Dec. 15, 2005, and claims priority thereto under 35 U.S.C. 121.

1. Field of the Invention

The invention generally relates to a delivery system for emplacing a self-expanding stent within a vessel or other passageway of a patient.

2. Related Art

Stents for maintaining or restoring the patency of an anatomical passageway of a patient are commonly used to minimize the invasiveness otherwise associated with a surgical exposure of a treatment site. In the case of endovascular implantation of a stent into a blood vessel, percutaneous deployment is initiated by an incision into the vascular system of the patient, typically via the femoral or carotid artery. A tubular or sheath portion of an introducer is inserted through the incision and into the artery. A central lumen through the introducer provides a passageway through the patient's skin and artery wall into the interior of the artery. An outwardly tapered hub portion of the introducer remains outside the patient's body to prevent blood from leaking out of the artery along the outside of the sheath. A valve provided on the introducer is manipulated to block blood flow out of the artery through the introducer passageway. A distal end of a guide wire is passed through the introducer passageway and into the patient's vasculature. The guide wire is threaded through the vasculature until the inserted distal end of the guide wire extends just beyond the intended treatment site. The proximal end of the guide wire typically extends outside the introducer for manipulation by the medical practitioner.

Some self-expanding stents are known as “braided stents” having a plurality of rigid but flexible and elastic thread elements defining a radially expanding helix. Braided stents are typically held at a distal end of an outer catheter and pushed into position by an inner piston. Other types of self-expanding stents include alloys, such as Nitinol, having shape memory or superelastic characteristics. The shape memory characteristics allow deformation of the stent to facilitate insertion of the stent into the vessel, or other passageway, whereafter resumption of the original shape of the stent occurs when the stent is subjected to sufficient heat within the patient's body. The superelastic characteristics generally allow the metal to be deformed and restrained to facilitate insertion into the vessel, or other passageway, whereafter the restraint is then removed permitting the stent to return to its original undeformed shape.

One example of a self-expanding stent delivery system is U.S. Pat. No. 4,580,568 issued to Gianturco on Apr. 8, 1986. This reference discloses a delivery apparatus that uses a hollow sheath, like a catheter. The sheath is inserted into a patient's vessel and navigated there through so that its distal end is adjacent to the intended treatment site. The stent is then compressed to a smaller diameter and loaded into the sheath at the sheath's proximal end. A flat end pusher is inserted into the sheath and pushes the stent from the proximal end of the sheath to the distal end of the sheath. Once the stent is located at the distal end of the sheath adjacent to the intended treatment site, the sheath is pulled back while the pusher remains stationary, thereby exposing the stent and allowing the stent to expand within the vessel.

Delivering the stent the entire length of the catheter sheath can pose problems however, including damage to the vessel or the stent during deployment. Preloading the stent at the distal end of the catheter, as in U.S. Pat. No. 4,732,152 issued to Wallsten, et al. on Mar. 22, 1988, can pose other problems. Such problems include embedding of the stent in the interior surface of the distal end of the catheter or other conduit within the distal end of the catheter. Difficulty in sliding the catheter or other conduit over the preloaded stent can also occur during deployment even where actual embedding of the stent into the catheter or conduit does not occur.

Yet a further option for self-expanding stent delivery is set forth in U.S. Pat. No. 6,743,219 issued to Dwyer, et al. on Jun. 1, 2004, the contents of which are incorporated herein by reference, wherein an outer sheath receives an inner shaft and a stent. The inner shaft includes a flexible coiled portion to help the delivery device navigate tortuous vasculature. The inner shaft also includes a distal marker at the distal end of the inner stop, and a stop. A stent bed, on which the undeployed stent is positioned within the outer sheath, extends between the distal marker and the stop of the inner shaft. The delivery device positions the stent across an intended treatment site by aligning the distal marker and stop appropriately relative to the intended treatment site. Because the distal marker and the stop are provided with radiopaque materials, the alignment of the stent is readily monitored fluoroscopically. The stent maintains frictional contact with the interior surface of the outer sheath until the outer sheath is withdrawn to deploy the stent at the intended treatment site. The stop prevents the stent from sliding back, i.e, withdrawing, with the sheath and effectively “pushes” the stent out the distal end of the sheath as the sheath is withdrawn. In this manner, the stent is deployed as desired across an intended treatment site. While an effective alternative, the stent delivery system of Dwyer, et al., nevertheless still risks twisting or bunching of the stent during deployment or loading of the stent, that can hinder desirable emplacement of the stent across an intended treatment site.

In view of the above, a need exists for systems and methods that can more reliably and accurately emplace a self-expanding stent within a vessel or passageway of a patient.

The various aspects of the systems and methods of the invention described herein provide a delivery system for reliably and accurately emplacing a self-expanding stent within a vessel or passageway of a patient.

In one embodiment, the delivery system comprises a delivery catheter working in complicity with a guide catheter or introducer in conventional manner. The delivery catheter further comprises an outer body, an inner body received within the outer body, and a self-expanding stent received on a stent bed along the inner body proximal to a distal end of the inner body so as to be between the inner body and the outer body in a loaded, undeployed state. The outer body thus acts as a sheath to protect and constrain the stent in its unexpanded state, while the inner body acts as a guide wire that assists in navigating the vasculature of a patient within which the stent is to be emplaced. At least one anchoring mechanism is provided on at least a proximal end of the stent bed. The at least one anchoring mechanism engages the loaded stent in its constrained state until deployment of the stent occurs and expansion of the stent results in the disengagement of the stent from the stent bed, the at least one anchoring mechanism and the inner body. The stent is a self-expanding stent comprised of a biostable polymer, bioabsorbable polymer or metal and can include drugs, bio-active agents and radiopaque markers. Radiopaque materials may be added to the anchoring mechanisms, and drugs or bio-active agents may be added to the stent and some, all or none of the anchoring mechanisms, as desired.

Alternatively, the at least one anchoring mechanism includes one anchoring mechanism provided at the proximal end of the stent bed and one anchoring mechanism provided at the distal end of the stent bed. In still other embodiments, the at least one anchoring mechanism includes anchoring mechanisms provided along the stent bed between the proximal end and the distal end of the stent bed. Of course, combinations of the above embodiments are also contemplated herein, as the artisan should readily appreciate. In any case, the at least one anchoring mechanism helps to maintain the stent in place between the inner body and the outer body during loading and deployment of the stent. In addition, the at least one anchoring mechanism provides support that helps minimize twisting or bunching of the stent during loading and deployment thereof. Radiopaque material can be added to the anchoring mechanisms in order to increase fluoroscopic visualization thereof. Accurate and reliable emplacement of the stent across an intended treatment site is thus enhanced. Drugs or other bio-active agents may be added to the stent and to some, all or none of the anchoring mechanisms, as desired.

In another embodiment, the at least one anchoring mechanism is a set of at least two bumpers located on the inner body, between which bumpers the stent is crimped when loaded onto the stent bed of the inner body prior to deployment. The bumpers preferably include radiopaque material (e.g., tungsten; tantalum; gold; barium sulfate; bismuth subcarbonate; iodine compounds; platinum; platinum/iridium or the like, and combinations thereof) so as to enhance visualization thereof during deployment of the stent. Drugs or other bio-active agents may be added to the stent and to some, all or none of the bumpers, as desired. As in the earlier described embodiment, after the delivery catheter is navigated through the vasculature and the stent is identified as positioned across the intended treatment site, the outer body is withdrawn. Withdrawal of the outer body permits the stent to disengage from the stent bed, the bumpers, and the inner body in general. Thereafter, the inner body is withdrawn and the stent is fully deployed as desired across the intended treatment site. The introducer/guide catheter is then withdrawn in conventional manner.

In yet another embodiment, the at least one anchoring mechanism is a set of at least two bumpers located on the inner body. One bumper is preferably located at the distal end of the stent bed and another bumper is located at the proximal end of the stent bed. Of course, other configurations are also contemplated herein including multiple bumpers along the stent bed with or without the bumpers at the proximal and distal ends of the stent bed, or bumpers in combination with anchoring mechanisms otherwise described herein, as the artisan will readily appreciate. The bumpers, or other anchoring mechanisms, preferably include radiopaque material to enhance visualization thereof during delivery of the stent. Drugs or other bio-active agents may be included in the stent and in some, all or none of the bumpers or other anchoring mechanisms, as desired.

In practice, the stent is loaded onto the stent bed of the inner body of the delivery catheter. The stent is oriented on the stent bed of the inner body so as to engage the at least one anchoring mechanism. The inner body with stent loaded thereon is then received within the outer body. The outer body thus protects and constrains the stent in its unexpanded state until deployment of the stent occurs by withdrawal of the outer body. Thereafter, the introducer/guide catheter and then the delivery catheter are introduced to the vasculature of a patient in conventional manner through an incision, for example, an incision in the femoral artery. The delivery catheter is then navigated through the vasculature of the patient to position the loaded stent across an intended treatment site. Fluoroscopically visualizing the at least one anchoring mechanism helps identify when the loaded stent is located across the intended treatment site. Once the loaded stent is identified as positioned across the intended treatment site, then the outer body of the delivery catheter is withdrawn. Thereafter, the stent expands to disengage from the stent bed, the at least one anchoring mechanism and the inner body in general. The inner body is then withdrawn and the stent is fully deployed across the intended treatment site. The introducer/guide catheter is then withdrawn in conventional manner.

The above and other features of the invention, including various novel details of construction and combinations of parts, will now be more particularly described with reference to the accompanying drawings and claims. It will be understood that the various exemplary embodiments of the invention described herein are shown by way of illustration only and not as a limitation thereof. The principles and features of this invention may be employed in various alternative embodiments without departing from the scope of the invention.

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