Device delivery system with two stage withdrawal
A medical device delivery system provides for a two-stage withdrawal of a deflated balloon portion of a catheter and the remains of a ruptured sheath. The deflated balloon portion is withdrawn from within an expanded medical device a predetermined distance before the remains of the ruptured sheath begins being removed from between the expanded device and a vessel wall. Initiating removal of the deflated balloon portion before the sheath reduces a total amount of drag that is exerted against a self-expanding medical device that has been deployed in a vessel.
1. A delivery system, comprising: a catheter having a distal end and distal portion;
a balloon portion disposed on the distal portion of the catheter;
a sheath disposed about the balloon portion;
a first catheter stop disposed on the catheter at a first location a first distance from the distal end of the catheter; and
a sheath ring fixedly coupled with the sheath and slidable on the catheter proximal to the first catheter stop, the first catheter stop being configured such that as the catheter is moved proximally relative to the sheath, the first catheter stop engages the sheath ring and moves the sheath proximally.
2. The delivery system of claim 1 , wherein the sheath is of a predetermined length and comprises a distal portion and a proximal portion, and wherein:
the sheath ring is attached to the sheath at the proximal portion of the sheath; and
the first distance is determined as a function of at least one of a length of the balloon portion and a length of the sheath.
3. The delivery system of claim 1 , further comprising:
a second catheter stop disposed on the catheter at a second distance from the distal end of the catheter, the second distance greater than the first distance.
4. The delivery system of claim 1 , further comprising:
a medical device disposed about the balloon portion and restrained by the sheath.
5. The delivery system of claim 4 , wherein the medical device is a self-expanding stent.
6. The delivery system of claim 4 , wherein a length of the sheath is determined as a function of at least one of:
a length of the balloon portion; and
a length of the medical device.
7. The delivery system of claim 4 , wherein:
a distance which the proximal portion of the sheath extends beyond the location of the first catheter stop is determined as a function of at least one of:
a length of the balloon portion; and
a length of the medical device.
8. The delivery system of claim 7 , further comprising:
a second catheter stop disposed on the catheter at a second location a second distance from the distal end of the catheter,
wherein the second distance is greater than the first distance.
9. The delivery system of claim 8 , wherein:
a difference between the first and second distances is determined as a function of at least one of:
a length of the balloon portion; and
a length of the medical device.
10. The delivery system of claim 8 , wherein:
the second location is substantially adjacent the sheath ring as held in place by the proximal portion of the sheath.
11. A method of delivering a medical device to a predetermined location in a vessel of a body, the method comprising:
constraining the medical device in a compressed state on a catheter with a sheath;
maneuvering a delivery system to position the constrained medical device substantially adjacent to the predetermined location;
releasing the medical device from its compressed state to deploy substantially at the predetermined location in the vessel; and
withdrawing the catheter proximally and sliding the catheter relative to the sheath, and continuing withdrawal of the catheter to engage a member fixedly coupled to the sheath so as to urge the sheath proximally together with the catheter.
12. The method of claim 11 , wherein the medical device is a self-expanding stent.
13. The method of claim 12 ,
wherein releasing the stent from the sheath comprises:
inflating a balloon portion of the catheter to rupture the sheath.