Delivery System With Profiled Sheath Having Balloon-Oriented Position
A delivery system for delivering a self-expanding medical device such as a stent. The delivery system includes a sheath profiled or shaped to reduce instances of interference between a distal edge of the sheath and a vessel or with any lesion or lesions that might be present in the vessel. The sheath is formed by modifying a cylinder of sheath material to include three portions and an initiation slit that controls the rupturing of the sheath to facilitate delivery of the medical device. The initiation slit is positioned on the delivery system with respect to a configuration of a balloon portion of the system.
1 . A delivery system, comprising:
a catheter having a distal end and a proximal end;
a balloon positioned at the distal end of the catheter, the balloon comprising at least two wing portions wrapped about the distal end of the catheter;
a medical device, having a compressed state and an expanded state, positioned about the balloon portion; and
a sheath positioned about the medical device to hold the medical device in the compressed state, the sheath comprising:
a distal sheath portion located at a distal end of the sheath, the distal sheath portion having a first diameter and a first longitudinal length;
a transition portion, of a second longitudinal length, having a distal end located adjacent the proximal end of the distal sheath portion, the distal end of the transition portion being of the first diameter and having a proximal end with a second diameter greater than the first diameter;
a body portion of a third longitudinal length, having a distal end adjacent a proximal end of the transition portion, the body portion being of the second diameter; and
an opening provided in an outer surface of the sheath,
wherein the opening is located on the positioned sheath in a predetermined relation to the at least two wing portions of the balloon.
2 . The delivery system of claim 1 , wherein:
the opening of the positioned sheath is located at a position where a total force exerted by expansion of the at least two wing portions against the positioned sheath, upon inflation of the balloon, is at its greatest.
3 . The delivery system of claim 1 , wherein:
the opening of the positioned sheath is located at a position that is approximately equidistant between sequentially adjacent circumferential points where the at least two wings press against the positioned sheath as the balloon is inflated.
4 . The delivery system of claim 1 , wherein:
upon inflation of the balloon, each wing of the at least two wings presses against the positioned sheath at a respective wing pressure location about the circumference of the sheath; and
the opening of the positioned sheath is located at a position that is approximately half the distance, around the circumference, between adjacent wing pressure locations.
5 . The delivery system of claim 1 , wherein the predetermined location of the opening is within 20% of a midpoint between sequentially adjacent circumferential points where the at least two wings press against the positioned sheath as the balloon is inflated.
6 . The delivery system of claim 1 , wherein:
the balloon is a dual-wing balloon having first and second wings, each wing having a respective wing-tip portion and a wing-base portion,
wherein the balloon is wrapped about the catheter in a bi-fold orientation, and p 1 wherein the opening in the sheath is located between the wing-tip portion of the first wing and the wing-base portion of the second wing.
7 . The delivery system of claim 1 , wherein:
the balloon is a dual-wing balloon having first and second wings, each wing having a respective wing-tip portion and a wing-base portion, and
wherein the balloon is wrapped about the catheter in a U-fold orientation, and
wherein the opening in the sheath is located between the wing tip of the first wing and the wingtip of the second wing.
8 . The delivery system of claim 1 , wherein:
the balloon is a tri-wing balloon having three wings, each wing having a respective wingtip portion and wing base portion,
wherein the balloon is wrapped about the catheter such that a wingtip portion of a first wing is folded toward a wing-base portion of a next adjacent wing, and
wherein the opening in the sheath is located between the wingtip portion of the first wing and the wing-base portion of the next adjacent wing.
9 . The delivery system of claim 1 , wherein the sheath comprises:
material with a grain oriented along the longitudinal axis of the sheath, and
wherein the opening is an initiation slit of a predetermined length oriented substantially in parallel with the material grain.
10 . The delivery system of claim 9 , wherein the slit extends from the distal portion to the transition portion.
11 . The sheath of claim 10 , wherein a distal-most end of the initiation slit is located at a predetermined distance proximally from the distal end of the sheath.
12 . A method of creating a medical device delivery system, the method comprising:
providing a catheter having a distal end and a proximal end;
wrapping at least two wing portions of a balloon about the distal end of the catheter;
positioning a medical device about the balloon, the medical device configurable in one of: a compressed state and an expanded state; and
providing a sheath about the medical device to hold the medical device in the compressed state about the folded balloon, wherein providing the sheath comprises:
providing a distal sheath portion at a distal end of the sheath, wherein the distal sheath portion has a first diameter and a first longitudinal length;
providing a transition portion, of a second longitudinal length, having a distal end located adjacent a proximal end of the distal sheath portion, the distal end of the transition portion being of the first diameter and providing a proximal end of the transition portion with a second diameter greater than the first diameter;
providing a body portion, of a third longitudinal length, having a distal end adjacent a proximal end of the transition portion, the body portion being of the second diameter; and
providing an opening in an outer surface of the sheath; and
locating the opening in the outer surface of the positioned sheath at a location in a predetermined relation to the at least two wing portions of the balloon.
13 . The method of claim 12 , further comprising:
positioning the opening of the positioned sheath at a location where a total force exerted by expansion of the at least two wing portions of the balloon against the positioned sheath, upon inflation of the balloon, is at its greatest.
14 . The method of claim 12 , further comprising:
positioning the opening of the at a location that is approximately equidistant between sequentially adjacent circumferential points where the at least two wing portions press against the positioned sheath as the balloon is inflated.
15 . The method of claim 12 , wherein the predetermined location of the opening is within 20% of a midpoint between sequentially adjacent circumferential points where the at least two wing portions press against the positioned sheath as the balloon is inflated.
16 . The method of claim 12 , wherein
the balloon is a dual-wing balloon having first and second wings, each wing having a respective wing-tip portion and a wing-base portion, the method further comprising:
wrapping the balloon about the catheter in a bi-fold orientation, and
positioning the opening in the sheath between the wing-tip portion of the first wing and the wing-base portion of the second wing.
17 . The method of claim 12 , wherein providing the sheath comprises at least one of:
applying RF energy;
heating;
applying microwave energy; and
applying IR energy.