Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reexamination Certificate
1998-03-26
2001-10-02
Milano, Michael J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001120, C623S001300
Reexamination Certificate
active
06296660
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to controlled deployment of medical devices such as endoprostheses and balloons.
Prostheses are used in body lumens that have been occluded or weakened by disease. For example, to treat arterial stenoses, an endovascular stent is implanted to hold the lumen open and to prevent any flaps or dissections on the lumen wall from occluding the lumen. To treat aneurysms, a prosthesis in the form of a graft is attached to healthy portions of the lumen on either side of the aneurysm so that the body of the graft bridges the weakened area. The wall of these grafts is initially permeable, but through clotting action, becomes fluid impermeable. This reduces the pressure in the aneurysm and hence, the likelihood that it will rupture.
Prostheses are typically delivered into the body on a catheter in small diameter form and then expanded to engage the lumen at the desired site. They may be self-expanding, i.e., they expand from a small diameter to a larger diameter by their own elastic forces after removal of a restraint, or they may be expanded by radial force from within the prosthesis, provided, for example, by an inflatable balloon on the end of the catheter.
In a procedure known as valvuloplasty, a balloon is used to open a valve in the heart. In this case, the physician urges the catheter through the closed valve to position the balloon beyond it. A controlled inflation is then effected such that the distal end of the balloon inflates to a diameter larger than the valve. The catheter is then withdrawn proximally until the physician feels resistance caused by the inflated portion of the balloon engaging the inner walls of the valve. A proximal portion of the balloon is then inflated which centers the balloon about the valve. Finally, the central portion of the balloon is inflated to dilate the valve.
SUMMARY OF THE INVENTION
In a first aspect, the invention features a prosthesis delivery system. The system includes a balloon catheter having an inflatable balloon on its exterior. The balloon is inflatable by injection of fluid through a lumen in the catheter. The balloon is initially partially restrained against inflation by a constraint. A tubular prosthesis is disposed on the catheter over at least a portion of the balloon and a portion of the constraint. The tubular prosthesis has a contracted condition and an expanded condition. The tubular prosthesis is initially disposed on the catheter in the contracted condition.
Embodiments may include one or more of the following features. The balloon is only initially radially constrained. The constraint is an axially slidable sheath which surrounds and partially constrains the balloon from inflation. The sheath is designed to axially slide along a length of the balloon in response to a pressure in the balloon, such that the balloon may be progressively incrementally inflated. The slidable sheath is adapted to slide axially onto a shaft of the catheter so that the sheath may be retrieved from the patient. The constraint is an elastomeric band which surrounds and partially constrains the balloon from inflation. The elastomeric band is disposed over a significant length of the balloon. The elasticity of the elastomeric band varies, e.g., by varying the thickness of the bond, from one end of the balloon to the other to allow progressive incremental inflation of the balloon. The elastomeric band has uniform elasticity over the portion of the balloon on which it is disposed. The elastomeric band is disposed only over a center region of the balloon and divides the balloon into a proximal and a distal region. The tubular prosthesis is a stent. The balloon is substantially nondistendible. The constraint is an axially slidable sheath which surrounds the balloon, the sheath being formed of a low coefficient of friction polymer. The polymer is teflon. The balloon has an inflatable portion corresponding to the length of the prosthesis and the balloon and prosthesis have a length of about 5 cm or more. The balloon and prosthesis have a length in the range of about 8-12 cm. The prosthesis includes a clot inducing fabric. The prosthesis is folded around the balloon and constraint. The catheter includes a single lumen for injection of the inflation fluid. The inflation lumen includes an inflation port for directing fluid into the balloon, the port located at a region corresponding to a portion of the balloon not initially restrained by the constraint.
In another aspect, the invention features a balloon catheter having an inflatable balloon on its exterior. The balloon is inflatable by injection of fluid through a lumen in the catheter. The balloon is initially partially radially restrained against inflation by a constraint which surrounds the balloon. The constraint is capable of constraining the balloon so that it may be progressively incrementally inflated.
Embodiments may include one or more of the features discussed above with respect to prosthesis delivery systems. Particular embodiments may include one or more of the following. The balloon is substantially nondistendible. The constraint is an axially slidable sheath which surrounds the balloon, the sheath being formed of a low coefficient of friction polymer. The polymer is teflon. The sheath includes an extension to proximal portions of the catheter for controlling the axial location of the sheath. The sheath is adapted to slide axially in response to pressure in the balloon.
In another aspect, the invention features a method of expanding a tubular prosthesis with a balloon catheter. The method includes providing a balloon catheter having an inflatable balloon on its exterior. The balloon is inflatable by injection of fluid through a lumen in the catheter. The balloon is initially partially radially restrained against inflation by a slidable sheath which surrounds the balloon. The sheath is adapted to slide axially along the balloon onto the catheter shaft in response to a pressure in the balloon such that the balloon may be progressively incrementally inflated. A tubular prosthesis is disposed on the catheter over at least a portion of the balloon and a portion of the constraint. The tubular prosthesis has a contracted condition and an expanded condition. The tubular prosthesis is initially disposed on the catheter in the contracted condition. The method further includes inflating the balloon such that an unrestrained portion of the balloon inflates first and causes a portion of the tubular prosthesis disposed over the unrestrained portion to expand and progressively incrementally inflating the constrained portion of the balloon causing a portion of the tubular prosthesis disposed over the restrained portion of the balloon to be progressively incrementally expanded.
In another aspect, the invention features a method of expanding a tubular prosthesis with a balloon catheter. The method includes providing a prosthesis delivery package having a balloon catheter having an inflatable balloon on its exterior. The balloon is initially partially radially restrained against inflation by an elastomeric band which surrounds the balloon and is inflatable by injection of fluid through a lumen in the catheter. The elastomeric band is disposed over a significant length of the balloon and has a non-uniform thickness such that the elastomeric band progressively expands with incremental increases in pressure and allows the balloon to be progressively incrementally inflated. A tubular prosthesis is disposed on the catheter over at least a portion of the balloon and a portion of the constraint. The tubular prosthesis has a contracted condition and an expanded condition. The tubular prosthesis is initially disposed on the catheter in the contracted condition. The method further includes inflating the balloon such that an unrestrained portion of the balloon inflates first and causes a portion of the tubular prosthesis disposed over the unrestrained portion to expand and progressively incrementally inflating the constrained portion of the balloon causing a portion of the t
Chin Yem
Chu Michael S. H.
Hess Kathleen L.
Nott Sepideh H.
Roberts George T.
Boston Scientific Corporation
Fish & Richardson P.C.
Milano Michael J.
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