US 20060036309 A1
A method of delivering a stent comprising providing an elongate guide having a stent coaxially supported on the guide for placement and movement by the guide, providing a tubular sheath member, advancing the elongate guide into the body to provide initial access to a preselected treatment site within the body and to carry and deliver the stent to position the stent at the treatment site, and exposing the stent from the tubular sheath member to enable the stent to move from a first reduced diameter position to a second expanded position.
23. A method of delivering a stent within a body comprising:
providing an elongate guide having a proximal end, a distal end, a length therebetween, and a radially expandable stent coaxially supported on the elongate guide for placement and movement by the elongate guide;
providing a tubular sheath member;
advancing the elongate guide into the body to provide initial access to a preselected treatment site within the body and to carry and deliver the stent to position the stent at the treatment site, the tubular sheath member covering at least part of the stent during advancement through the body; and
exposing the stent from the tubular sheath member to enable the stent to move from a first reduced diameter position to a second expanded position.
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32. A method of delivering a stent within a hollow body organ comprising:
providing a stent delivery assembly including an elongate guide in the form of a wire or hypotube, a stent mounted on the elongate guide proximal of a distalmost tip of the guide, and a tubular sheath for covering a least a portion of the stent during advancement of the elongate guide through the body;
inserting the elongate guide, stent and tubular sheath into the body;
initially advancing the elongate guide into the body to provide initial access to an area of stenosis or aneurysm;
further advancing the elongate guide without passage over a guidewire to cross the stenosis or aneurysm to enable positioning of the stent at the stenosis or aneurysm, the tubular sheath covering at least part of the stent during advancement through the body; and
exposing the stent from the tubular sheath to enable the stent to move from a first reduced diameter position to a second expanded position to treat the stenosis or aneurysm.
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The present invention relates generally to catheters and intravascular medical procedures. More particularly, it relates to methods and apparatus for delivering a stent through a catheter by way of a guidewire delivery device.
Intravascular stents are well known in the medical arts for the treatment of vascular stenoses. Stents are prostheses which are generally tubular and which expand radially in a vessel or lumen to maintain its patency. For deployment within the body's vascular system, most stents are mounted onto a balloon angioplasty catheter for deployment by balloon expansion at the site of a dilated stenosis or an aneurysm. Self-expanding stents, which typically expand from a compressed delivery position to its original diameter when released from the delivery device, generally exert a radial force on the constricted portion of the body lumen to re-establish patency. One common self-expanding stent is manufactured of Nitinol, a nickel-titanium shape memory alloy, which can be formed and annealed, deformed at a low temperature, and recalled to its original shape with heating, such as when deployed at body temperature in the body.
To position a stent across an area of stenosis or an aneurysm, a guiding catheter having a preformed distal tip is percutaneously introduced into the vascular system of a patient by way of, e.g., a conventional Seldinger technique, and advanced within the vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired artery. A guidewire is then positioned within an inner lumen of a dilatation catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire must first be advanced out of the distal end of the guiding catheter into the patient's coronary vasculature until the distal end of the guidewire crosses a lesion to be dilated, then the catheter having a stent positioned on the distal portion is advanced into the patient's vasculature over the previously introduced guidewire until the stent is properly positioned across the lesion. Once in position, the stent may be released accordingly.
It is generally desirable to have catheters which present small cross sectional diameters to enable access into small sized vessels. However, conventional techniques and apparatus typically require the use of a guidewire for the desirable placement of the catheter and stent within the vasculature. Thus, conventional catheters typically require a separate lumen within the catheter body to allow for the passage of a guidewire therethrough. This separate lumen necessarily adds to the cross sectional profile of the device. Yet vasculature having a tortuous path and/or a small diameter, such as the intracranial vasculature, present problems for the conventional stenting catheter. Accordingly, a highly flexible stenting apparatus which is capable of accessing tortuous regions and which presents a small cross section is needed.
A highly flexible stent delivery assembly is described below. The assembly has the desirable characteristics of guidewires in traversing tortuous vasculature, including small cross sectioned vessels. The stent delivery assembly of the present invention is thus able to deliver and place a stent anywhere in the vasculature or within the body that is readily accessible by a guidewire but is not normally accessible by a stenting catheter body which would ride over such a guidewire.
The stent delivery assembly may typically comprise a guidewire body which is preferably covered at least in part by a retractable sheath. A radially expandable stent is disposed directly in contact about the guidewire preferably near or at the distal end of the guidewire. The retractable sheath preferably covers the entire stent during deployment and placement, and is retractable proximally to uncover or expose the stent for radial expansion. A pair of optionally placed radio-opaque marker bands may be located on either side (distally or proximally) or both sides of the stent on the guidewire body.
The sheath may have a flush port, which is in fluid communication with the distal end of the assembly, located near the proximal end of the sheath. The flush port enables a fluid, e.g., saline, to be passed through the assembly prior to insertion into the vasculature for flushing out air or debris trapped between the sheath and guidewire. It may also be used to deliver drugs or fluids within the vasculature as desired.
Because the guidewire body, rather than a catheter body, carries and delivers the stent through the vasculature, the stent may be placed almost anywhere in the body accessible by a conventional guidewire. This may include, e.g., the tortuous intracranial vasculature as well as, e.g., the more accessible coronary vasculature. Furthermore, the assembly, which may include the guidewire, sheath, and stent, may be introduced into a wide variety of conventional catheters. This portability allows for flexibility in using the same type of assembly in an array of conventional catheters depending upon the desired application and the region of the body to be accessed.
The sheath may be made from various thermoplastics, e.g., PTFE, FEP, Tecoflex, etc., which may optionally be lined on the inner surface of the sheath or on the outer surface of the guidewire or on both with a hydrophilic material such as Tecoflex or some other plastic coating. Additionally, either surface may be coated with various combinations of different materials, depending upon the desired results. It is also preferably made to have a wall thickness of about, e.g., 0.001 in., thick and may have an outer diameter ranging from about 0.0145 to 0.016 in. or greater. The sheath may be simply placed over the guidewire and stent, or it may be heatshrinked to conform closely to the assembly.
The guidewire body may be made of a conventional guidewire or it may also be formed from a hypotube having an initial diameter ranging from 0.007 to 0.014 in. Possible materials may include superelastic metals and alloys, e.g., Nitinol, or metals such as stainless steel, or non-metallic materials, e.g., polyimide. The hypotube may be further melted or ground down, depending upon the type of material used, into several sections of differing diameters. The distal end of the guidewire may be further tapered and is preferably rounded to aid in advancement through the vasculature. Radio-opaque coils may be placed over a portion of distal end to aid in radiographic visualization.
The stent may be configured to be self expanding from a constrained first configuration when placed upon guidewire to a larger expanded second configuration when deployed. When the sheath is retracted proximally, the stent preferably self expands to a preconfigured diameter of, e.g., about 0.060 in. (1.5 mm), and up to a diameter of about 0.315 in. (8 mm). Various materials may be used to construct the stent such as platinum, Nitinol, other shape memory alloys, or other self expanding materials.
Other variations may include a guidewire which defines a stepped section near the distal end of the guidewire. The stepped section outer diameter is less than the uniform diameter defined by the remainder of the guidewire. The stent may be placed over this section while maintaining a flush outer diameter which may facilitate delivery of the stent-guidewire assembly not only through catheter body but within the vasculature. The guidewire may be further formed into tapered section distally of the stepped section.
When in use in tortuous pathways, such as intracranial vessels, the guidewire assembly may be used with the sheath alone or in combination with a delivery catheter. The catheter body may be advanced within the vessel to a treatment location such as an aneurysm. Once the catheter is near the treatment site, the guidewire may be advanced out of the catheter and adjacent the treatment site. The sheath may then be retracted proximally to expose the stent to radially expand into contact with the walls of the vessel. Alternatively, the sheath may be held stationary while the guidewire and stent are advanced to expose the stent, e.g., as when deploying a coil stent. The stent may be self expanding or configured to expand upon the application of an electric current with or without the sheath. In either case, once the stent has been released from the guidewire and expanded, both the guidewire and sheath may be withdrawn into the catheter body and removed from the vicinity. The catheter may be left within the vessel to allow for the insertion of additional tools or the application of drugs near the treatment site.
Other variations may include an expandable balloon section preferably located distally of the stent. In this case, treatment preferably includes the expansion of the balloon first to mitigate any occlusions within the vessel. The stent may then be released in a manner similar to that described above. Once the balloon has been deflated and the stent expanded, the assembly may be removed from the vicinity.
A stent delivery assembly having a small cross section and which is highly flexible is described herein. As shown in
Because the guidewire body 24, rather than a catheter body, carries and delivers stent 28 through the vasculature, the stent 28 may be placed almost anywhere in the body accessible by a conventional guidewire. This may include, e.g., the tortuous intracranial vasculature as well as, e.g., the more accessible coronary vasculature. Furthermore, assembly 40, which may include the guidewire 24, sheath 26, and stent 28, may be introduced into a wide variety of conventional catheters. This portability of assembly 40 allows for flexibility in using the same type of assembly 40 in an array of conventional catheters depending upon the desired application and the region of the body to be accessed.
The sheath 26 may be made from various thermoplastics, e.g., PTFE, FEP, Tecoflex, etc., which may optionally be lined on the inner surface of the sheath or on the outer surface of the guidewire or on both with a hydrophilic material such as Tecoflex or some other plastic coating. Additionally, either surface may be coated with various combinations of different materials, depending upon the desired results. Sheath 26 is preferably made to have a wall thickness of about 0.001 in. thick, and optionally thicker, and may have an outer diameter ranging from about 0.0145 to 0.016 in., or greater. Sheath 26 may also be placed over guidewire body 24 having a diameter of about 0.038 in. When placed over guidewire body 24 and stent 28, it may be simply placed over to slide along wire 24 or it may also be heatshrinked over the wire 24 and stent 28 to conform closely to the assembly.
A more detailed view of the guidewire assembly is shown in the cross sectioned side view in
The guidewire body 24 may be made of a conventional guidewire and it may also be formed from a hypotube having an initial diameter ranging from 0.007 to 0.014 in. The hypotube or guidewire may be made from a variety of materials such as superelastic metals, e.g., Nitinol, or it may be made from metals such as stainless steel. During manufacture, a proximal uniform section 50 of the hypotube may be made to have a length of between about 39 to 87 in. (100 to 220 cm), preferably between about 63 to 71 in. (160 to 180 cm), having the initial diameter of 0.007 to 0.022 in., preferably 0.008 in. The hypotube may be further melted or ground down into a tapered section 52, depending upon the type of material used, which is distal to the proximal uniform section 50. Tapered section 52 may have a length of about 4 in. (10 cm) to reduce the diameter down to about 0.002 to 0.003 in. The hypotube may be further formed to have a distal uniform section 54 of about 2 in. (5 cm) in length over which the stent 28 is preferably placed. Radio-opaque marker bands may optionally be placed either distally 30 or proximally 32 of stent 28 to visually aid in the placement of the stent 28, as is well known in the art. Alternatively, distal and proximal marker bands 30, 32 may be eliminated altogether. Marker bands 30, 32 may be used as blocks or stops for maintaining the stent in its position along guidewire body 24. Alternatively, if bands 30, 32 are omitted from the device, stops or blocks may be formed integrally into the guidewire body 24 or they may be separately formed from material similar to that of guidewire body 24 and attached thereto.
Distal end 56 may be further tapered beyond distal uniform section 54 to end in distal tip 58, which is preferably rounded to aid in guidewire 24 advancement. A coil, preferably made from a radio-opaque material such as platinum, may be placed over a portion of distal end 56. Alternatively, a radio-opaque material, e.g., doped plastics such as bismuth or tungsten, may be melted down or placed over a portion of distal end 56 to aid in visualization. Stent 28 is preferably made to be self expanding from a constrained first configuration, as when placed upon guidewire 24 for delivery, to a larger expanded second configuration as when deployed within the vasculature. Stent 28 may be constrained by sheath 26 to a diameter of, e.g., 0.014 in., while being delivered to a treatment site within the body, but when sheath 26 is retracted proximally, stent 28 preferably self expands to a preconfigured diameter of, e.g., about 0.060 in. (1.5 mm), and up to a diameter of about 0.315 in. (8 mm). Various materials may be used to construct stent 28 such as platinum, Nitinol, other shape memory alloys, or other self expanding materials. Sheath 26 may also have drainage ports or purge holes 64 formed into the wall near the area covering stent 28. There may be a single hole or multiple holes, e.g., three holes, formed into sheath 26. Purge holes 64 allow for fluids, e.g., saline, to readily escape from inbetween sheath 26 and guidewire 24 when purging the instrument, e.g., to remove trapped air or debris.
In operation, the stent delivery guidewire may be used with or without the catheter body to deliver the assembly intravascularly. It is preferable that a catheter be used to provide a pathway close to the treatment site. However, in tortuous pathways, such as intracranial vessels, the guidewire device may be used with the sheath alone if the catheter body presents too large a cross section for delivery purposes.
Stent 28, as shown in
Treatment may also be accomplished with the guidewire variation having an expandable balloon section.
The applications of the guidewire assembly and methods of use discussed above are not limited to the deployment and use within the vascular system but may include any number of further treatment applications. Other treatment sites may include areas or regions of the body such as organ bodies. Modification of the above-described assemblies and methods for carrying out the invention, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the scope of the claims.