Pull back stent delivery system with pistol grip retraction handle

A stent delivery system for delivering a self-expanding stent to a predetermined location in a vessel includes a catheter body having an axial guidewire lumen and a pull-wire lumen. A medical device such as a self-expanding stent is held in a reduced delivery configuration for insertion and transport through a body lumen to a predetermined site for deployment. The stent is carried axially around the catheter body near its distal end and held in its reduced configuration by a retractable outer sheath. A proximal retraction handle is connected to the proximal end of the catheter body and includes a pistol grip trigger engaging a rachet mechanism, which is connected to a pull-wire which extends through the pull-wire lumen and is connected to the retractable outer sheath.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improved wire pull back delivery 
system. More specifically, the invention relates to a wire pull-back 
implant delivery system which utilizes a pistol grip retraction handle to 
retract the retractable outer sheath and deploy a medical implant for a 
minimally invasive application, such as an endovscular stent graft, vena 
cava filter, self-expanding stent, balloon expandable stent, or the like. 
2. Description of the Related Art 
Delivery systems for deploying medical implants, such as an endovscular 
stent graft, vena cava filter, self-expanding stent, balloon expandable 
stent or the like, are a highly developed and well known field of medical 
technology. These medical devices have many well known uses and 
applications. In particular, a stent is a prosthesis which is generally 
tubular and which is expanded radially in a vessel or lumen to maintain 
its patency. Stents are widely used in body vessels, body canals, ducts or 
other body lumens. A self-expanding stent is a stent which expands from a 
compressed delivery position to its original diameter when released from 
the delivery device, exerting radial force on the constricted portion of 
the body lumen to re-establish patency. One common self-expanding stent is 
manufactured of Nitinol, a nickeltitanium 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. 
Wire pull-back stent delivery systems are disclosed in U.S. Pat. No. 
5,360,401 and U.S. Pat. No. 5,571,135. One important factor in delivering 
the stent is a controlled precise retraction of the retractable outer 
sheath. What is needed is a wire pull-back stent delivery system which 
provides for a controlled and precise retraction of the retractable outer 
sheath and enables the physician to accurately determine proper 
positioning of the stent, as well as track the retraction of the outer 
sheath. 
SUMMARY OF THE INVENTION 
The inventive stent delivery system for delivering a self-expanding stent 
to a predetermined location in a vessel includes a catheter body having an 
axial guidewire lumen and a pull-wire lumen. A medical device such as a 
self-expanding stent is held in a reduced delivery configuration for 
insertion and transport through a body lumen to a predetermined site for 
deployment. The stent is carried axially around the catheter body near its 
distal end and held in its reduced configuration by a retractable outer 
sheath. A proximal retraction handle is connected to the proximal end of 
the catheter body and includes a pistol grip trigger engaging a rachet 
mechanism, which is connected to a pull-wire which extends through the 
pull-wire lumen and is connected to the retractable outer sheath.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
While this invention may be embodied in many different forms, there are 
shown in the drawings and described in detail herein a specific preferred 
embodiment of the invention. The present disclosure is an exemplification 
of the principles of the invention and is not intended to limit the 
invention to the particular embodiment illustrated. 
FIGS. 1 and 2 show side views of the inventive delivery system. The 
preferred embodiment discussed below specifically discusses delivering a 
self-expanding stent, but it should be understood that the inventive 
delivery system can deliver any medical implant for a minimally invasive 
application, such as an endovascular stent graft, vena cava filter, 
self-expanding stent, balloon expandable stent or the like. 
The preferred embodiment is a two-part system including an implantable 
medical device such as a self-expanding stent and a delivery catheter. The 
delivery catheter is shown generally at 10 and includes the catheter body 
12, the retractable outer sheath 14 and the proximal retraction handle 16. 
FIG. 3 shows the distal end of the delivery system 10, and the retractable 
outer sheath 14 in more detail. A medical device is held in its delivery 
configuration by outer sheath 14, and in the preferred embodiment the 
medical device is a self-expanding stent 18 which is carried 
concentrically around the single lumen extrusion 35 near the distal tip 
20. 
FIG. 4 shows that catheter body 12 is a tri-lumen catheter, and in the 
preferred embodiment is a nylon extrusion with a guidewire lumen 22, a 
stent flushing lumen (priming port) 24 and a pull-wire lumen 26. The 
guidewire lumen accommodates a 0.035 inch guidewire 28. The guidewire 
lumen 22 and stent flushing lumen 24 terminate at the point shown 
generally at 30, and a stainless steel pull-wire 32 is shown extending 
from the pull-wire lumen 26 and which attaches to a stainless steel ring 
34 (best seen in FIG. 6). A nylon single lumen (guidewire lumen) extrusion 
35 is thermally lap welded to the catheter body 12 at point 30 and has a 
nylon extrusion which is thermally molded to the distal end of the nylon 
single guidewire lumen 35 and tapered to create smooth atraumatic tip 20. 
FIG. 5 shows a cross-section view of the single guidewire lumen extrusion 
35 along section lines 5--5 of FIG. 3. 
In the preferred embodiment, tantalum radiopaque marker bands 36 and 38 are 
bonded to the single lumen extrusion 35 using cyanoacrylate adhesive, 
although it should be understood that marker bands 36 and 38 could be 
attached using other well known techniques such as weld swaging or 
crimp/swaging. Marker bands 36 and 38 are used in connection with an 
imaging procedure to aid in determining proper positioning of the stent in 
the body lumen. Although fluoroscopy is the most common imaging procedure 
typically employed, x-ray, MRI or any other well known imaging techniques 
may also be utilized. In the embodiment of FIG. 3 marker bands 36 and 38 
show the proximal and distal ends of the stent 18 as carried in its 
delivery configuration. An alternate embodiment may locate marker bands 36 
and 38 to mark the proximal and distal ends of the stent 18 in its 
expanded position, which would have a slightly shorter length than the 
stent in its delivery configuration. A nylon band stent stop 40 is also 
bonded to the single lumen extrusion 35 and prevents the stent 18 from 
moving proximally along the single lumen extrusion 35 as the outer sheath 
14 retracts, assisting in accurate stent placement. Stop 40 could also be 
attached using any standard technique, such as overmolding or ultrasonic 
welding. 
In the preferred embodiment the retractable outer sheath 14 is a clear 
medical grade PTFE (polytetrafluoroethylene) extrusion which covers the 
distal 10-20 cm (depending on stent length) of the catheter body 12. 
However the outer sheath 14 could be made of any suitable fluropolymer 
material. A specific alternate embodiment could utilize a fluropolymer 
material which is transparent to visible light to enable the operator to 
directly view deployment in an endoscopic delivery procedure. Such 
materials are well known in the art. In the preferred embodiment 
self-expanding nitinol stents of from 6-14 mm in diameter and ranging from 
20-100 mm in length can be accommodated. It should be understood that any 
type of self-expanding stent could be employed, although nitinol 
self-expanding stents are preferred. The retractable outer sheath 14 is 
connected to the proximal retraction handle 16 by stainless steel 
pull-wire 32 which is welded to stainless steel ring 34 (best seen in FIG. 
6). Ring 34 is swaged in place to the outer sheath 14 with tantalum 
radiopaque marker band 42. The distal end of retractable outer sheath 14 
is designed to flush fit with tip 20 to create a smooth profile. The 
proximal end of retractable outer sheath 14 is finished with a smooth 
transition consisting of a thermally molded nylon extrusion swaged in 
place with a tantalum radiopaque marker band 44 (best seen in FIG. 7). It 
should be understood that tapered transition could be molded in place, 
which would eliminate the need for a marker band swaged in place to attach 
the nylon extrusion. It should also be understood that the marker band 
could be bonded or crimp/swaged. The tapered smooth transition of the 
proximal portion of outer sheath 14 allows catheter body 12 to be more 
easily extracted from the body lumen and introducer sheath. The proximal 
end of retractable outer sheath 14 slidably seals to catheter body 12 
permitting it to slide proximally along catheter body 12 when retracted by 
pull-wire 32. The nitinol stent 18 is compressed at low temperature for 
loading into delivery system 10 and held in its reduced delivery 
configuration by retractable outer sheath 14. Upon deployment in vivo at 
body temperature the original stent shape is restored as the nitinol stent 
self-expands, exerting radial force on the constricted portion of the body 
lumen to re-establish patency. Marker band 45 is also bonded to extrusion 
35 approximately one stent length proximally of marker band 42 (in the 
unretracted position) and is utilized to confirm full stent release as 
discussed further below. It should be understood that marker band 45 could 
also be attached using swaging or crimp/swaging. 
FIGS. 6-8 show details of FIG. 3 is more detail. 
Referring again to FIGS. 1 and 2, the stent 18 is deployed using proximal 
retraction handle 16. The invention proximal retraction handle 16 is a 
multi-component assembly ergonomically designed with a pistol grip trigger 
46. The trigger mechanism 46 is contained within a two-part molded ABS 
(acrylonitrile, butadiene, styrene) outer housing that is snap-fit 
together. The ABS trigger 46 has a polypropylene safety lock mechanism 48 
to prevent inadvertent stent release. The proximal retraction handle 16 is 
connected to the catheter body 12 by the pull-wire 32, a Y-luer assembly 
shown generally at 50 and a strain relief 52. 
Referring now to FIG. 9, catheter body 12 is connected to strain relief 52, 
and the proximal end of pull-wire 32 exits from lumen 26 and is threaded 
and crimped to a strip 54 by crimp tube 56, which is part of the ratchet 
mechanism used to retract outer sheath 14. Strain relief 52 is made of 
Pebax.RTM. and is insert molded over catheter body 12, and is constructed 
to fit inside the nose of proximal handle 16 (best seen in FIGS. 11 and 
12). 
Referring now to FIG. 10, the Y-luer assembly 50 is shown, and consists of 
a nylon Y-luer with a nylon single lumen extrusion overmolded to each leg 
of the "Y". It should be understood that the extrusion could also be 
bonded to each leg of the "Y". Leg 58 of the "Y" forms the stent flushing 
port and leg 60 forms the guidewire port. Each single lumen is thermally 
lap welded to the catheter body 12 and provides communication between the 
Y-luer and the guidewire lumen 22 and the stent flushing lumen 24. The 
stent flushing lumen is used to fill the retractable outer sheath 14 with 
fluid to purge air out of the outer sheath 14 prior to insertion of the 
catheter body 12 into the body. 
Referring now to FIG. 11, the proximal retraction handle 16 is shown in 
more detail and is a multi-component assembly ergonomically designed with 
a pistol grip 46, which is engaged by trigger spring 62. The pistol grip 
46 or trigger has two cylindrical protrusions 64 on either side of trigger 
46 which extend outwardly and are received by pivot mounts molded into the 
proximal retraction handle 16 to attach the pistol grip 46 to the handle 
16 as well as provide a point about which the pistol grip rotates. A 
trigger stop 66 defines the normal trigger position and the trigger 46 is 
maintained in this normal position by trigger spring 62. As the trigger 46 
is squeezed it rotates to its compressed position, and when released the 
trigger spring forces the trigger to rotate back to its normal position 
flush with the trigger stop 66. Trigger 46 includes a pair of gear 
engaging members 68 which are spaced apart to form a channel wide enough 
to receive the larger gear 72 of gear 70. Gear 70 includes gear 72 and a 
pair of gears 74 fixedly attached on either side of gear 72. Gears 74 
engage the gear engaging portions 68 of trigger 46 to rotate gear 70 as 
trigger 46 rotates. Axle 76 is received by molded mounts in the two parts 
of handle 16 to attach the gear to the handle 16. Gear 72 engages the 
ratchet mechanism which is attached to the pull-wire 32. The ratchet 
mechanism is comprised of a rack driver which is comprised of 2 parts, a 
rack 80 and a rack tab 82, which snap fit together to form a channel for 
receiving strip 84. As can be seen best in FIG. 15, strip 84 contains ramp 
shaped stops 86, each adjacent pair of stops forming detents 88 (best seen 
in FIG. 15). Rack tab 82 contains a flexible ratcheting pawl 89 which 
engages with detents 88 such that when the rack driver is moved proximally 
when the trigger 46 is squeezed to its compressed position, strip 84 is 
moved proximally, but when the rack driver is moved distally when trigger 
46 is rotated to its normal position, the flexible ratcheting pawl 89 
slides up ramp shaped stop 86 to disengage from strip 84. 
As is best shown in FIG. 12, strip 84 is received by channel 90. A second 
spring, strip spring 92 is securely held to handle 16 by tail 94 and its 
locking head portion 96 lockingly engages with detents 88 to hold strip 84 
in place when trigger 46 is released and rack tab 82 is moved distally to 
lockingly engage with the adjacent distal detent 88. The ramp shaped stops 
86 (best seen in FIG. 15) allow the strip to be moved proximally in 
channel 90 by rack tab 82 until the adjacent detent lockingly engages with 
strip spring 92. The detents are each approximately 2 mm apart so that 
each complete squeeze of the trigger 46 retracts the pull-wire 32 and 
outer sheath 14 approximately 20 mm. By repeatedly squeezing and releasing 
trigger 46 the outer sheath 14 is fully retracted to release the stent 18 
to self-expand. The rachet mechanism is designed to work with any stent of 
lengths between 20 and 100 mm, although it could easily be designed to 
accept any desired length stent. 
The ratio of gear 70 in the embodiment shown in FIG. 12 is 2:1, such that a 
1 mm squeeze on trigger 46 retracts the outer sheath 2 mm. However, it 
should be understood that any desired gear ratio could be utilized. For 
example gear 70 is designed optionally to allow for a gear ratio of 1:1. 
In that embodiment a trigger 46 with a single gear engaging portion 68 is 
designed to engage gear 72, rather than gears 74, to provide a 1:1 ratio 
such that a 1 mm squeeze on the trigger will retract the outer sheath 14 1 
mm. In order to accommodate this detents 88 would be spaced approximately 
1 mm apart on strip 84 and it should be understood that the stops 86 and 
detents 88 could be arranged in any desired spacing. Gear 70 could also be 
designed if desired to have a ratio of 1:2, such that a 2 mm squeeze of 
trigger 46 retracts outer sheath 14 1 mm. 
In operation, pre-placement imaging or other standard procedure is normally 
performed to identify an insertion tract and assess the site. A guidewire 
(0.035 inch diameter in the preferred embodiment) 28 is maneuvered through 
the tract. The delivery system 10, with the preloaded medical device (a 
self-expanding stent in the preferred embodiment) is then passed through 
an introducer sheath and tracked over the guidewire until the medical 
device is positioned as desired. In the preferred embodiment markers 36 
and 38 are used with standard imaging techniques such as fluoroscopy, 
x-ray, MRI or the like to aid in proper positioning of the stent 18 across 
the stricture. As the trigger 46 is repeatedly squeezed, the outer sheath 
14 is retracted proximally to release the stent to self-expand. To aid in 
confirming complete stent deployment and release the operator observes 
marker 42 move to meet marker 45. 
FIGS. 3, 13 and 14 show the distal end of delivery system 10 in a 
pre-deployed state (FIG. 3), partially deployed state (FIG. 13) and fully 
deployed state (FIG. 14). 
Referring now to FIGS. 16 and 17, an alternate embodiment of the inventive 
delivery system is shown where the pull-wire 32 is U-shaped with the U 
loop portion 100 of the pull-wire 32 looping around a notch 102 in the 
pull-ring 34. The 2 ends of the U-shaped pull-wire extend through 
pull-wire lumen 26 to attach to the ratchet mechanism. As shown in FIG. 
17, if desired a plurality of pull-wires 32 could by looped around a 
plurality of notches 102 spaced around pull-ring 34. A second pull-wire 
lumen could be provided to carry one or more pull-wires 32 to allow the 
pull-ring to be retracted with the pulling force more evenly distributed 
around the pull-ring perimeter. Two U-shaped pull-wires 32, each carried 
by a separate lumen and each looping around pull-ring 34 as shown in FIG. 
17 would provide 4 points arranged around pull-ring 34 to more evenly 
distribute the pulling force on the pull-ring. Each pull-wire lumen could 
also optionally carry more than 1 pull-wire to provide as many attachment 
points on pull-ring 34 as desired. 
This completes the description of the preferred and alternate embodiments 
of the invention. It is to be understood that even though numerous 
characteristics and advantages of the present invention have been set 
forth in the foregoing description, together with the details of the 
structure and function of the invention, the disclosure is illustrative 
only and changes may be made in detail, especially in matters of shape, 
size and arrangement of parts within the principals of the invention, to 
the full extent indicated by the broad, general meaning of the terms in 
which the appended claims are expressed. Those skilled in the art may 
recognize other equivalents to the specific embodiment described herein 
which are intended to be encompassed by the claims attached hereto.