CA2189354A1

CA2189354A1 - Stent and method of making the same

Info

Publication number: CA2189354A1
Application number: CA002189354A
Authority: CA
Inventors: Gladwin S. Das
Original assignee: Gladwin S. Das; The Regents Of The University Of Minnesota
Current assignee: University of Minnesota
Priority date: 1994-05-04
Filing date: 1995-05-04
Publication date: 1995-11-16
Also published as: WO1995030385A1; ATE288232T1; EP0758215A1; JPH09512194A; AU682772B2; EP0758215A4; US5554181A; DE69533985D1; AU2479195A; DE69533985T2; JP3717931B2; ES2236707T3; EP0758215B1

Abstract

A stent (1) comprising a self-expandable cylindrical body constructed of a single integral piece of material (8), including a plurality of wavy closed windings (10), and strips (16) interconnecting the windings such that the stent is prevented from stretching longitudinally, is provided. A method of manufacture of the stent by winding a continuous wire (10) upon spikes (44) on an elongated mandrel (40) to form a self-expanding shape memory coil is disclosed. A method of implanting the stent by releasably securing the stent in a sheath for insertion into a body cavity to maintain patency, is also disclosed.

Description

W095/30385 218935~ l~l" '-- I
6TEN-T AND NETEIOD OF NARING T~I3 SANE
FIELD OF T}IE lNV~LlUN
The present invention relates to a stent to be 5 deployed inside a cavity of an animal for --;ntA;n;n~
patency of the cavity. This invention also relates to a method of making and positioniny such a stent in the body cavity of an animal.
BACRGROllND OF TEIE lNvh~lL~
In many diseaseg, a body cavity, such as a passageway or channel (e.g. blood vessel, esophagus, bronchus, etc. ~ through which a body fluid or other substance (e.g., air in bronchus) flows, may collapse or 15 be narrowed to be substantially restricted. A
passageway can be 50 restricted that fluid flow in the passageway is ~l;m;n; ~hf~fl or blocked. For example, in coronary artery disease, the coronary artery of a mammal is narrowed or restricted such that blood f low through 20 the artery is rl;r;n;qh~d Even after balloon angioplasty procedures, such as percutaneous tr~n~ min~1 angioplasty, in which a blood vessel is dilated by means of a balloon catheter to flatten plaque against the artery wall, in many cases, restenosis 25 occurs soon afterwards and the vessel becomes restricted again. Following perCutAn~ollc balloon angioplasty, the arterial wall ~ develops tears As a result, f laps of the inner layer of the arterial wall may hang loosely in the blood vessel, causing obstruction to 30 blood flow and requiring emergency bypass surgery.
There is a need for a means to -~-;ntA;n patency of :: ~ -collapsing body cavities or blood vessels and to prevent the renarrowing of the vessel after angioplasty.
Stents can be used to provide mechanical 35 support to --;nt~;n the patency of blood vessels.
Similarly, the patency of body cavities and passageways such as urethra, bile duct, esophagus, ureters,aorta, etc., can also be r-;ntA;n~d by stents. Stents of various shapes and designs have been l]t; 1; 70d for such Wo 95l30385 2 1 8 .9 3 ~ ".,~ s 1 ~
purposes. For example, U.S . Patent No. 4, 886, 062 (Wiktor) discloses an intravascula~ radially ~ n~lAhle stent and method of i~?lAn -nt the3~eof-: The stent disclosed by Wiktor comprises a~wire wound into a 5 r~nt;nlloug helix along the length of the stent. The stent is made of a low-memory metal and is radially expanded by ;nflAt;n~ a ~thrt,~r balloon, which exerts a force on the stent. U.S. Patent No. 4,969,458 (Wiktor) also discloses a stent made of low-memory metal, 10 ~YpAntl~hle radially to a larger diameter by the action of inflation of a balloon. U.$. Patent No. 5,133,731 (Wiktor) discloses yet another stent made of low-memory material. The stent has a cylindrical body coiled from a generally r~nt;n~ us wire with a deformable zig-zag 15 structure . Means f or preventing the stent ~ 8 body f rom stretching along its longitudinal axis are also present in the stent.
Becau5e stent5 made with low-memory materials rer~,uire -h~n;~i~l force to expand the stent, such as a 20 force exerted by the inflation of a balloon, their use can result in trauma to the body caused by the imprecise control of the expansion of the stent or the balloon.
Moreover, stents made with low memory material may have a tendency to be compressed into a smaller ~; i t~ by 25 the radial,-~inwardly directed force exerted by the body tissue on the stent. Self-~n~i;ng stents have been developed to obviate the use of ~t~rn~ll 1 y applied mechanical orce for their expansion. For example, IJ.S.
Patent No. 4,830,003 (Wolff) discloses a cylindrical 30 stent for preventing arterial closure and restenosis.
The stent is made of biocompatible metal wires welded together ~n pairs at alternate ends with each pa~r of ~ ' w~res bent into a V-section. The stent is compressed and loaded ~nto an outer catheter, posit~oned in a 35 selected location and released for self-expans~on by an inner catheter. ~.S. Patent No. 5,104,404 (Wolff) discloses an art~culated stent made up of a number of .. . .. , .. , , ,, ~ _ _ _ WO 9!il3038!; ~ 1 8 ~ 3~ ~ P~ v3$11 ~ . :

individual stent segments~ A number of wires are welded together to form a segment, and adjacent stent segments are connected together to provide a hinge action. In a similar fashion, U.S. Patent No. 5,035,706 (Gianturco) 5 discloses a self-~An-l;n~ stent formed of stainless steel wire arranged in a closed zig-zag configuration including an endless series of straight sections joined at their ends by bends. The bends of at least one end of the stent are formed into eyes f or connection with 10 eye8 at one end of a similarly constructed stent. The stents are compre8sible into reduced diameter size for insertion into and removal from a body passageway.
Because self-P~An~l;ng stents, such as those made from 8tainless steel, once ~Antl.~d, cannot be ~-15 deformed unless an ~lr~rn;ll force is applied thereto, such stents generally cannot be removed from the body cavity once they are deployed therein . Theref ore, stents that can be brought back to a smaller shape and size after expansion within a body cavity have been

2 0 developed to enable removal af ter deployment . For example, U.S. Patent No. 5,037,427 (Harada et al.) discloses a method of implanting a stent and removing same from a tubular organ. The stent is formed of a two-way shape-memory alloy and expands or shrinks in the 25 radial direction, in accordance with changes in temperature. Also, U.S. Patent No. 5,147,370 (M_Nc.",a et al. ) discloses a coil stent constructed from a nitinol alloy. ~owever, because such stents expand by the heat of the body, there can be a ri5k that such a

3 0 stent would expand bef ore it is properly deployed or positioned in the desired location.
U.S. Patent No. 5,026,377 (Burton) discloses a stent pl A~--' instrument and method for deployment or retraction of a self -f~YrAnt1; n~ stent in a body canal .
35 The instrument comprises an elongated tubular outer sleeve having disposed therein an elongated core which is movable relative to the sleeve and has a grip member Wo gs/303~5 210935g for releasably holding a self~ n~n~ stent within the outer sleeYe U.S. Patent No. 5,078,720 (Burton) discloses yet another stent pl~c: '_ instrument and method for the ~ t of a aelf-expanding stent in a 5 body canal. The inatrument comprisea an elongated inner tube having an outer tube dispoaed along ita axia for carrying and retaining a aelf -~ n~l; ng stent and an aLL~ y. t for r~ ; n~ the 8tent, in combination with at least one of: (a) a location member for positioning 10 and fixing the instrument so that the stent is released at a desired ~ ocation in the body canal, and (b) a memher for r~ c;n~ the stent in a retrograde manner.
The stenta diacloaed by Burton in the two patents are wire-mesh-type stents.
sur~aRY OF T~IE ~\/~l The present invention provides a stent having an elongated (e.g., generally cylindrical) body which includes a ~1llr~l ;ty of generally closed windinga (or 20 loops) and strips inter~ nn~-t;ng the windings such that the stent is prevented from stretching longitl~;nzllly (or along its axis). The cylindrical body is conatructed from a aingle piece of material 8uch as a wire. The stent is self-~n~hl~ from a first, 25 radially-constrained, lln~ n~P~l geometry to a aecond, radially-unconatrained, F-~n~ geometry. The stripa can be interconnected to form an aligned, longitudinally oriented apine which helpa to prevent longitudinal stretching of the stent, thus --~ntA;n;n~ the geometry 30 thereof. The windings can further have curves (or waves) which, for example, can have a generally sinusoidal appearance. The stent of present invention, being capable of self-expanaion, is effective for supporting and ~-intFl;n;n~ patency of a body cavity, 35 auch aa a paasageway (e.g., artery, aorta, bile duct, urethra) through which a fluid flows. Such a stent can _ _ WO 95/30385 21 8 9 3 ~ ~ r 5/lJ~. . Al fl, be implanted in a body cavity of an animal, such as a mammal, 1n~11It8;n~ humans.
In another aspect, the present invention provides a stent comprising a eelf-P~n~l~hle 5 cylindrical body f ormed f rom a continuous wire . The cylindrical body i8 a coil having successive windings of wire wherein each of the windings (or loops) is an essentially closed, complex loop . The term " complex loop" refers to a loop that has curves (or waves) or 10 structures such a6 o-shaped eyelet9 on the loop. The stent is formed such that it i9 prevented from stretching longitudinally (or axially) by portions of wire interconnecting adj acent windings . When compresaed and put under radial pressure by a radial constraint, 15 such as a sheath of a catheter, which prevents the stent from ~ n~1lng radially outward, the stent has a first diameter reflecting the dimensions of the constraint.
When the radial constraint is removed, the stent can self-expand from the first radially-constrained, 20 llnP~n~f~d diameter to a second, radially-unconstrained, P~rln~n~l~(l diameter. The stent can be wound such that any two adjacent windings (for example, a first and second successive windings), are connected and restrained from stretching longitudinally by a portion (or strip) of 25 wire interposed between the first and second successive windings and intertwining with a portion of one of said two adj acent windings . The portion of the wire interposed between the two successive windings can be connected to a f irst end or end portion of the f irst 3 0 winding and an end or end portion of the second winding and intertwined with a second end portion of the f irst winding to prevent stretching longitudinally. The intertwining of the wire interposed between successive windings can be aligned to result in a generally 35 straight longitudinal spine (or cord) in the stent. The stent can be formed from a single, continuous wire into such a coil having successive windings.

W095/30385 ~ ' 0~
21893~4~

The present invention also provides a method of making a stent. ~ The method includes a step of winding a wire on a cylindrical mandrel to form a self-n~lin~ coil of successive windings (or loops) such 5 that each of the windings having curves and that the coil i8 prevented from stretching longitudinally by portions of ~he wire connecting the successive windings.
Spikes can be used on the mandrel for the wire to be wound thereupon. The wire can be wound such that the 10 portion of wire connecting any adj acent first and second successive windings is connected to a f irst end portion of the f irst winding and an end portion of the second winding and intertwined with a second end portion of the f irst winding.
The mandrel can be disassemblable (or capable of being taken apart) to enable a o~med or wound stent to be removed therefrom without distortion. Such a disassemblable mandrel can contain a elongated, preferably generally cylindrical body with spikes 20 disposed thereon for a wire to be wound to form the stent. The cylindrical body can contain digagg~ hlf.
longitudinal layers. In another aspect, the spikes can be movably affixed on the cylindrical body, for example, by screwing into the cylindrical body.
The stent can be made with a flexible material, for example, a shape-memory material such as nitinol. In the preferred embodiment, the stent is made of "superelastic" ~nitinol, which is an alloy c~nt~;n;ns equal parts of nickel and titanium. A stent made with such a superelastic nitinol, upon ~nne~l ;n~ at an elevated temperature, gains memory of the shape in which it is ~nnP~ (i . e., a preprogrammed shape) . If deformed into other shapes, upon release, the stent will spring back to its p~ yl ~1 shape. The method of making the stent can include ;3nne~l ;ng the wound coil on the mandrel at an elevated temperature above room temperature, preferably at above 5000C, more preferably _ . _ _ _ _ _ _ . _ _ .. _ . ... . . . _ _ _ _ . _ _ WO 95/30385 2 1 8 9 ~ ` P~
about 500C, for a determined period, for example, about 3 0 minutes .
Also provided by the present invention is a system for positioning (or deploying) in a body cavity a 5 self ~ r~n~hl ~ stent . This system includes an instrument for r~ ~r~m~nt (or deployment) of a self -~lr~ntl;n~ gtent and a self-~r~n~l;nrJ stent releasably held by the instrument. In this aystem, the stent ;nrlll~lP~ a self-f~ n~hle/ cylindrical body formed by a 10 rt~nt;nll~lus wire. The cylindrical body is a coil of successive windings each having curves and the stent is prevented from stretching in its longitudinal axis. The stent is self-~r~n~hle from a first radially-constrained, l~n~r~n~f3 diameter to a second, radially-15 unconstrained, ~l~rAn~ d diameter.
The instrument can include an elongatedtubular outer sheath (or sleeve) having a first end and a second end, such as a conventional catheter, for radially constraining the stent proximate the distal end 20 of the instrument, and an elongated core or pusher device having a f irst end and a second end movably disposed within the lumen of the sheath. As used herein, the term.. "proximal" means the end or part nearest to the operator of the instrument and the term 2~ "distal" means the end or part farthest from the operator. The stent can be self-~l~r~n~hle such that it self-expands and r~nt~rtcl or rests on the body tissue or wall in the body cavity when the sheath is moved longit~ ; ni~l l y away from the distal end o~ the core, 30 thus releasing the radial constraining by the sheath on the stent.
The stent of the present invention has many superior characteristics which render it highly useful as scaffolding support to m-;nt~;n patency of body 35 cavities and passageways. Because the stent of the present invention can be made from a single r~mt;nll~us wire, compared to prior art stents, the manufacturing ~:

W0 95/30385 ~ r ~ . c or 11 ~
~ .
process of the stent of the present invention is greatly simplified and the amount of waste material resulting from ~nllf~-turing is greatly reduced, thereby reducing the cost of.production.
Furthermore, the stent of the present invention overcomes many of the 8hortcomings of the prior art stents. For example, the zig-zag stents have many ends of wire (or wire ends), which are welded to other wire ends. With a large number of wire ends, as is present in a multiple-wired stent, special effort may be needed tQ shield these wire-ends or prevent them from protruding into tissue of the body. Such effort is labor-intensive. Likewise, the wire-mesh stents also have multiple wires and thus impose similar risk associated with multiple wire ends. In the present invention, using one continuous wire to make a stent reduces the number of wire ends, thus greatly lowering the risk of causing irritation or injury to body tissue.
Such a single-wired stent has only two wire ends, whioh can easily be shielded or curved radially inward to avoid irrlt:~t;n~ or injuring body tissue.
With multiple-wired steuts such as the zig-zag type stent or the ~wire-mesh stent, because of the interlocking or intermeshing of the wires, the stents are not very compressible and flexible. The wire-mesh stent tends to become compres8ed (or narrow) radially at the bend when it is flexed and lengthen9 longitl-~l;n~l ly when compressed radially. In contrast, the stent of the present invention ~ is advantageous in that it can be flexed without causing significant radial compression.
Moreover, it can be compressed radially without longitudinal t~;r~ n:~l change. Further, using a single piece of material (such as a c nnt;nl1nus wire) to make a stent affords the advantage that a stent of any desirable length can be made without having to join sections o~ =wire together.
_ _ _ _ _ .

WO9~/30385 21 8~3S4 ` ` : -Often, balloon inflation is needed to expand prior art coil stents or wire-mesh stents fully to the - desired diameter. The present invention can be 8elf-ntl1ng such that no external force, such as that 5 provided by an i n~ ; ng balloon, is needed to fully expand the diameter of the stent . Such self -~n~1 ng nature of the stent of the present invention obviates ~ h~ftU...C and possibly trauma-causing procedures such as balloon inflation.
Furthermore, unlike the coil or helical stents that do not have means for constraining longitudinal extension and tend to 5tretch under longitudinally directed f orces ( such as the f orce caused by f lowing fluid or movement of the vessel contacting the stent), the stent of the present invention has constraint means 80 that the stent does not extend lo~gitll~1n~l1y from the ~ ntl~rl f orm .
Becau8e the deployment of thermoelastic shape-memory stents generally re~uire ice-cold saline to r-;nt~;n the stent in the soft or shrunken form or saline of relative hot temperature to expand the stent, the use of self ~ n~i n~ stents obviates such cumbersome procedures. Although the stent of the present invention can be made of thermoelastic shape-memory material to render it soft and shrunken at a temperature lower than normal human body temperature (about 37~C), the stent can also be made with other flexible material which are effective in rendering a stent capable of returning (or self -~n~11 nS) to a ~r~ r~L 1 shape upon release from a deformed shape.
An example of such a material is stainless steel, superelastic nitinol, or superelastic plastics. The stent can be made to have any desirable length with any number of loops or windings f rom a single wire without 3 5 the use of external adhesion means such as welds or adhesives .

218 9 3 ~

Prior art cylindrical, spikeless mandrels, such as those used ior making coil-shaped stents that are expanded with balloons, are not readily adapted for making a self-~xpAn~l;ng coil with curves from a single wire because there is no structure on such mandrels for securing the stent. The mandrel of the present invention ~V~ A this problem by having spikeq upon which the wire can~ be wound. Further, the mandrel of the present invention can be used to make stents that have completely F~n~l OAf~ loops and still enables the removal of the stent, once f ormed, f rom the mandrel without distortion. The mandrel of the present invention can be disassemblable such that it can be taken apart without distorting a stent that has been formed thereon. This overcomes the problem that a stent tautly wound on a mandrel with spikes cannot be easily released from the mandrel. The disassemblable mandrel of the present invention greatly facilitates the forming of stents with intricate patterns of waves from single lengths of wire. ~
BRIEF DES~:Kl~ lUN OF THE DRAWING
These and other ieatures, aspects and advantages oi the ~present invention are illustrated with reference to the Ar~, ying drawing, wherein like numerals represent corresponding parts in the several views:
FIG. 1 is an isometric view of an embodiment of the stent in its ~An~lPd form;
FIG. 2 is a side view of an isolated loop ~or winding) of = the stent of FIG . 1;
PIG. 3 is an end view of the stent of FIG. 1;
FIG. 4 is an end view of a mandrel ior making the stent of FIG. ~ 1;
FIG. 5 is an isometric uiew of a portion of the mandrel of FIG. 4 with a wire mounted thereon for making a stent;
.. _ .. _ ... . .. _ _ ~9 WO 95l30385 5 ~ r~
FIG. 6 is an end view of the structure resulting after a mandrel of FIG. 5 has been partially disassem.bled and parts removed therefrom.
FIG . 7 is a plan view viewing f rom the end of another ~ n~;rAnt of a mandrel of the present invention wherein spikes have been pushed below the cylindrical surf ace of the mandrel .
FIG. 8 is a side elevation in section of an instrument f or deploying a stent of the present invention with the stent mounted therein in a blood vessel;
FIG. 9 is a side elevation of the instrument of FIG. 8 showing a partly deployed stent in a blood vessel;
FIG. lO is a side elevation of the instrument of FIG. 9 showing a fully deployed stent in a blood vessel;
FIG. 11 is a side elevation showing a stent of the present invention deployed in a bloood vessel;
FIG. 12 is an isometric view of another ; of the stent according to the invention;
FIG . 13 is an end view of the mandrel f or forming a stent shown in FIG. 12;
FIG. 14 is an isometric view in section of a mandrel with a stent of FIG 13 wound thereon;
- FIG. 15 i8 an isometric view of another embodiment of the stent according to the invention;
FIG. 16 is an end view of the stent of FIG.
15; and 3 o FIG . 17 is an isometric view of yet another Amho~1;r^nt of the stent arcor~l;n~Aj to the invention.
DT~T~TT.T~ 3s~:KI~Lluw OF TRE 1NV~WL1UN
For purposes of illustration, the preferred 3~ Amhorl; - t of this invention is shown and described in reference to applications in angioplasty. ~lowever, applications other than in angioplasty, such as in body _ _ _ _ . . . .. . _ ... _ _ .

WO 9~/3038~ 218 9 3 ~
li ~
cavities and passageways, are practicable and no limitation in scope of the invention is intended by the embodiment s .
FIGS. 1-3 show the construction of an 5 embodiment of the stent of the present invention. The stent 1 is a coil 4 having a generally cylindrical shape with an open lumen 6. That is, as shown in FIG. 3, the stent 1 has a circular cross section with an open central portion or ~ lumen 6 . A continuous wire 8 c~n be 10 used to form the coil 4 such that the coil has successive windings (or loops) 10 and is prevented from stretching in its longitudinal axis. Any two adjacent successive windings 10 (or first lOA and second lOB
windings) are connected and restrained from stretching 15 longitudinally by an interconnecting portion or strip 12 of the wire. Such an interconnecting portion of wire 12 is integrally connected to a first end portion 14 of the first winding lOA and an end portion 16 of the second winding lOB and intertwined with a ~econd end portion 18 20 of the first winding lOA. Thus each winding (e.g. lOA) forms a loop closed by intertwining, wherein one end portion (e.g. 14) of the winding is integrally connected to the ;n~P~r~nn~ ;n~ portion (e.g. 12) of the wire and the other end portion (e.g. 18) of the winding (e.g.
25 lOA) is intertwiningly connected to the same interconnecting portion (e . g . 12 ) . Such intertwining of the interconnecting portions of the wire along the length of the stent results in an aligned, generally straight, longitudinal spine (or cord) 20 in the stent 3 0 1. The intertwining of the interconnecting portion of the wire with an end portion of a winding secures the windings in relation to one another to r-;nt~;n the geometry of the stent and prevent stretching of the stent longitudinally or axially. The number of turns in 35 the intertwining can vary rlPrPn~l; ng on the distance between successive windings. In a stent 1 with only one spine 20, because the portions of the windings 10 on the ~ W095130385 218935~ 13 P~ 'O'tll part of the cylindrical coil opposite the spine are not rigidly held together but have freedom of ~n~,v~ t, the - stent can be flexed without significant narrowing of the lumen 6 at the bend as a result of the flexion.
5 Referring to FIG. 2, a winding (or loop) 10 has curves (or waves) 22, which have peaks 24 each with a valley 26 adjacent and associated therewith. As referred to herein, peaks generally are oriented in the same direction. Preferably, the curves 22 in a winding 10 are generally sinusoidal in appearance and each has one peak 24 and one valley 26. In a sinusoidal wave, a wave of one wavelength exists between two adj acent points having the same phase. The peaks and valleys can have smooth turns resempling a ture sine wave rather than sharp turns as in a zig-zag form. This is particularly true in the case where a stif f material such as a nitinol wire is used to form the stint. In the formation process of the stent, the st;ffnPqq of the wire facilitates the smooth curving of a winding as the wire is bent. Depending on the size of the body cavity to be supported }:y the stent, the size of the curves and number of curves 22 or peaks 24 in a 9tent L can vary.
For example, a stent 1 having an PYri~nf~ outside diameter of about 3 mm can have two peaks 24 or curves 22 whereas a stent designed to have an .o~n~ d outside diameter of 1 cm can have four or more (for example, eight) peaks. The distance between adjacent loopis or windings 1 can also vary ~l~r~n~l; n~ on the supporting strength desired and the size of the body cavity to be supported by the stent. For example, a stent having an ~n~l~d ~ t~r of about 0.7 cm can have windings that are about 0 . 5 cm apart f rom peak to peak along the longitudinal axis.
The wire 8 f or making the stent can be a flexible material of adequate strength for making self-n~l;ng stents, such as stainless steel, plastic polymeric material, shape-memory material (e.g., W0 95/3038S 21~ u~ r ~
14 : -nitinol), and the like. The use of nitinol and shape-memory material for making stents has been disclosed in U.S. Patent No. 5,147,370 ~McNamara) and in "Shape-Memory A110YB, " Scientific American, Vol. 281, pages 74-82, November=~979, the disclosure of which relating to the methods of making stents from such shape-memory material is incorporated by ref erence herein .
Preferably, the stent is made of a superelastic shape-memory material, such as one made with superelastic nitinol. The stent can also be made with thermoelastic shape-memory material, which can also be made of nltinol. Nitinol alloys as an implant material have been est:~hl; ~h~d to be biocompatible. A
number of permanent implants made from nitinol have been used in humans. Nitinol is also resistant to corrosion, oxidation, and abrasion. Nitinol wires and structures of other shapes are commercially available, for example, f rom suppliers such Shape Memory Applications Co . and Flexmedics Co.
A stent made from a flexible or superelastic material can be compressed into a smaller size (i.e.
smaller rl; .~r and/or shorter length) to fit and be confined inside a catheter-like instrument for delivery of the stent to a desired location in the body cavity.
When the stent is released from the in~L~, t, the flexibility of the flexible material causes the stent to spring back to its shape and size before compression. A
stent made of a thermoelastic shape-memory material can also be made by forming the material into a desired size and shape and ~nn~l ;n~ at a temperature higher than the transition temperature to program the stent to have that desired size and shape. A~ter cooling the stent to a temperature below the transition temperature, the stent becomes soft and can be reduced to a smaller size by 3~ crushing or compressing by force so that it can be deli~ered to the selected location in the body cavity while r~-;nt~;n;ng the temperature of the stent at below WO 95l30385 218 9 3 ~ ~ r~J~

the transition temperature. As long as such below-transition-temperature is m~;nt~;n~l, the stent remains at its reduced size without subj ecting to an externally applied compression. When the stent is warmed to a 5 temperature above the transition temperature, the stent returns to the PL~:~1UYL ~ J size and shape (i.e., the size and shape before the stent was crushed).
The stent can also be coated with a substance for reducing the risk of thrombosis and preventing lO undesirable depositions thereon. For example, appropriate r-~t1n~fi, such as s; l; rr,nf~ rubbers, hydrophilic polymer8, fibrin, coatings C~lrt~;n;nrJ
heparin, collagen, and the like may be used on the stent. The curves of the stent, upon expansion, rest 15 and press on the wall of the body cavity, thereby exerting a pressure on the wall to prevent the collapse of the wall of the body cavity.
A stent of the present invention can be made by winding a single rr~nt;nllr,us wire, such as a nitinol 20 wire, on a preformed cylindrical jig or mandrel to obtain the coil with the right conf iguration of curves .
FIG. 4 shows the end view of an embodiment of a mandrel used for forming the coil of a stent of FIG. 1. The mandrel 40, as shown in FIG. 4, has a diameter of about 25 0.4 cm and rows (or rings) 42 of spikes 44 disposed longitudinally 0 . 5 cm apart on the outer surface of the mandrel. E~ach ring 42 of spikes rrnt:~;nF: six spikes 44 arranged evenly as a ring- like conf iguration on the outer surface 46 of the mandrel. The spikes 44 are 3 0 about 0 .1 cm high and about 0 . 7 mm x 0 . 7 mm in cross section .
FIG. 5 shows how a wire 8 made of nitinol is wound on the mandrel around (or upon) the spikes to form a stent with the conf iguration of FIG . 1. The wire 8 is 35 wound on the spikes 44 of two different rings to form a generally sinusoidal winding 10 with curves . A f irst end (not shown) of the wire can be anchored or secured -.

W0 95~30385 2 ~ 8 9 3 ~ JOII ~
on the mandrel 4 0 so that the wire 8 can be wound upon the spikes 44 tautly. The wire extends paGt the last spike 50 o the first ring 42A of spikes to the second ring 42B of spikes and winds upon the first spike ~2 of 5 the second ring of bpikes, then extends back to wind upon a spike (the second spike 54) on the first ring 42A
of spikes, thereby forming the first valley 56 and peak 58 of the first winding (the order of the rings and spikes are arbitrarily assigned for convenience of 10 reference). The wire is then wound upon the spikes in the second and first rings of spikes alternately in a wavy fashion to form the wavy loop of the first winding.
The wire wound upon the last spike 50 of the first ring 42A of spikes extends to the third ring 42C of the 15 spikes while intertwining with the portion 59 of the wire ~lct~n~;n~ from the first end of the wire between the first ring 42A of spikes and the first spike 52 of the second ring 42B of spikes. Similarly, the wire wound upon the last spike 60 of the second ring 42B
20 extends to the fourth ring 42D of the spikes while intertwining with the portion 62 of the wire f~tPnf~i n~
between the second ring 42B of spikes and the f irst spike 64 of the third ring 42C of spikes. This portion 61 of wire can be considered the interconnecting portion 25 interr~ nn~rtlng the first winding 42A and the second winding 42B. The portion of wire 59 extending from the first ring 4ZA of spikes to the first spike 52 of the second ring 42B of ~ spikes i5 an end portion of the first winding lOA (see FIG. 1) and the portion of wire 62 30 connected with the interC~nn~ tin~ portion 61 and extending to the first spike 64 of the third ring 42C of spikes is an end portion of the second winding lOB. The process for forming a winding can be repeated to wind the wire alternately upon the spikes of the second and 35 third rings of spikes to form the second winding.
Depending on the length of the wire in the intercoImecting portion, the number of intertwining WOgs/30385 2f 8g3.s~ P~
twists (or turns) therein can vary, typically from about 0 . 5 to about 4 . 5, preferably 1. 5 intertwining twists between adj acent windings . An intertwining twist (or ==
turns) herein refers to a 360 turn of the double helix 5 formed by the intertwining of two wires. This process for forming successive winding9 can be ~r)nt;nll~tl until a stent of desired length is formed on the mandrel.
Af ter the wire i8 wound on the mandrel, the other end (not shown) can be secured to the mandrel as 10 does the first end. The wire ends can be secured to the mandrel by methods such as tying a knot on a structure such as a spike or being gripped by a clamp. The wire ends can be secured in such a way that they are turned --radially inward on the mandrel 80 that when the f;n;Rh~
15 stent is deployed the wire ends will not protrude into the body tissue. This can be done, for example, by providing a depression on the surf ace of the mandrel on which the wire end is clamped.
Subsequently, the mandrel with the wire 20 mounted thereon can be annealed at about 500C for about 3 o minutes and then cooled to room temperature . Methods of i~nnf~l ;n~ nitinol material is widely known in the art ~_ and can be used for pL~LUyL ; n~ the stent of the present invention to attain a desired configuration or --25 shape. The stent can then be removed from the mandrel.
The mandrel can be made with a material that can m~;nt~;n mechanical integrity for the wire to be wound thereon and undergo temperature changes for : =
~nnP~l ;n~. An example of material effective for 30 construction of the mandrel is a metal such as aluminum, titanium, or nickel; or an alloy such as carbon steel, stainless steel, or MONEI-. As previously stated, the mandrel of the present invention is preferably disassemblable to facilitate the removal of a formed, 35 wound stent therefrom. The mandrel can have spikes or projections disposed on the outer surface thereof upon which the wire can be wound to form the stent. The Wo 95/3038s ~ P~
2t89~S~ 18 spikes can be cylindrical, has a square cross section, or other similar shapes as long as a wire can be firmed wound upon them. Other than spikes, means on which the wire can be wound, such as hooks, or 61its cut on the 5 mandrel, can be used to f orm the cu~ves of the stent .
Preferably, the mandrel can be di5assembled 80 that the stent can be released therefrom without being distorted e~ther radially or longit--~l;n~lly. As used herein, a stent is "distorted~ if after removal from the 10 mandrel, .~lrtl~rn;~l ~force is needed to shape the stent back to the form prior to removal. Referring to FIGS. 4-5, which shows the detail structures of an r-~c~;r^nt of the mandrel of the present invention, the mandrel 40 has spikes 44 and a cylindrical body 65 which includes three 15 layers. The two ~Yt~rn'll (or end) layers 68A, 68B of the cylindrical body each has a lateral (or transverse) cross section that is shaped generally like a segment of a circle defined by an arc and a chord. All of the spikes 44 arç disposed on such l~rt.orn;ll layers 68~, 68B .
20 The third layer 70 of the cylindrical body is an intermediate layer disposed between and separating the P~rt~rn~l layerg 68A, 68B. Such intermediate layer 70 is a strip or A spacer having a lateral (or transverse) cross section that is generally rectangular. Bach of 25 the three layers fan have holes 72 proximate its ends through which screws 73 can extend. The three layers of the mandrel can thus be secured together at the two ends with screws 73 and bolts 74.
To remove a formed (or wound) stent from the 30 mandrel 8hown in FIGS. 4-5, the bolts 74 and screws 73 are removed from the ends of the mandrel 40 so that the three layers of the mandrel are no longer secured together. ~he intermediate layer 70 can then be withdrawn ~or removed) from the mandrel 40, enabling the 35 two ,o~rt~-rn~l layers 68A, 68B to be brought together. ~ow referring to FIG. ~ 6 (FIGs. 5-6 are not drawn to scale, the spikes are shown larger proportionally compared to .... . . . _ . _ _ _ WO95/30385 2~g354 . r~ ., the overall size to show structure), the two external layers 68A, 68B, after being brought together, results in a structure that is still generally cylindrical but has a smaller transverse, cross-s~t;~n~l area than that of 5 the three-layered mandrel. The thickness of the intermediate layer 70 i8 selected such that the transverse cross section of such two-layered structure has a perimeter that is small enough to enable the windings of the stent to be lifted off the spikes, thus 10 releasing the stent from the mandrel. At least one layer (68A or 68B) of the two-layered structure can then be slid out of the stent at a time. In this way, the stent can be removed f rom the mandrel without distortion .
In another embodiment, the mandrel can have spikes that are movably affixed thereon. For example, the spikes can be made of screws that can be removably screwed into the cylindrical body of the mandrel. To separate a formed stent from the mandrel without 20 distortion, the screws can first be removed by unscrewing from the cylindrical body.
In yet another embodiment, as shown in FIG. 7, the spikes can be slidably affixed in holes on the cylindrical body. The spikes 144 can extend out o~ the 25 cylindrical outer surface 146 of the cylindrical body (of the mandrel) for the wire to be wound thereupon.
When the stent has been formed, the spikes 144 can be forced (for example, by pushing with a finger) proximate ~=
or below the outer cylindrical surface 146 of the 30 mandrel 140. This results in a mandrel 140 wherein the spikes 144 do not extend out of the surface 146 of the cylindrical body. The stent can then be slid off the mandrel. The mandrel can have a annular outer shell 17~
through the spikes extend. A means, such as a core (not 35 shown) that fits inside the shell 17~, can be used to push the spikes 144 out of the outer cylindrical surface 146 of the mandrel 140 for a wire to be wound thereon.

W095/30385 21893~ s~ - I~1/.J~ SI1~ 1 ~
~ r ~ 20 Such a mandrel is part; r~ rl y well adapted to be used in mass-producing the stent. For example, to further facilitate removal of a formed stent, a means can be u3ed to extend the~ spikes as a group in and out of the 5 cylindrical surface 146 of the mandrel such that the spikes do not have to be pushed individually.
A stent formed with a superelastic material by the method described hereinabove can be deformed, compressed or flexed to various shapes and will 10 immediately return to its preprogrammed, annealed shape on release oii the externally applied force. Since the stent can be formed to have any desired length, it can be formed to have the exact length needed for a particular application. Alternatively, a stent of a 15 desired length can be formed by trimming the ends o~f a longer stent. A long stent can also be divided into shorter stents.
The self -P~ri~n~; ng stent of the present invention can be used to provide scaf f olding support to 20 hollow orga~;s or passageways or rh~nnPl ~ which are narrowed. ~he stent can also act as a skeleton to f ashion vascular graf ts f or the treatment of aneurysms o~ vascular structures. The stent is preferably delivered to, placed or deployed in a desired or 25 selected location by using a catheter-like instrument.
FIG. 8 and FIG. 9 ~show such an embodiment. The instrument has an elongated tubular outer sheath (or sleeve) 78 having a first or proximal end 79A and a second or distal end 79B. The sheath can be a 30 conventional catheter. The instrument also includes an elongated core or pusher device 80 having a first or proximal end and a second or distal end movably or slidably disposed within the sheath. The core 80 can have a generally blunt, conical or h~ rh~rical tip, 35 nose, or terminal piece 81 proximate or at its distal end. The sheath and core can be made with conventional material efiective for making catheters. The conical Wo g~/3038s ~ 8 g ~ S ~ P.~
, .

tip 81 of the core 80, being on the distal end 79B of -the instrument, f acilitates the introduction of the instrument through a narrow body channel into the desired location of the body cavity. The conical tip 81 5 has a diameter at the base of t~e cone approximately equal to the outside ~; i t~r of the eheath 78 . The core 80 also has an annular recees 82 defined by the conical tip 81 and a plug 83 some distance away from the conical tip toward the proximal end of the core. The 10 core 80 can be drawn such that the conical tip is proximate to the distal end of the sheath 78 so as to conf ine a stent within the sheath . A stent 101 of the present invention loaded (or seated) in the recess 82 of ~ -the core 80 is compressed and secured (or restrained) 15 from ,o~i~nll; ng radially by the sheath 78 . Because the stent of the present invention is highly compressible, it can be rnnf; n~d in the recess of the core by the sheath and the core. --The instrument can have a channel running 20through the center of the core longitudinally. A guide- -wire 84 can be provided to extend from one end of the core 80 through the channel iqnd out the other end of the core 80. The catheter-like sheath 78 with a stent restrained therein is positioned across the area to be 25stented by passing over the guide-wire 84. Methods of positioning catheters, such as one with the aid of a guide-wire, are widely known in the art. Such standard methods can be utilized to position the instrument with the loaded stent in a desired location. After the 30instrument has been positioned in a desired location, the sheath 78 is gently drawn or pulled back while the core 80 is ~-;nti~irf~fl stationary. As the sheath 78 is pulled backwards in the proximal direction, the now unconstrained stent 101 springs open or expands radially 35due to its flexibility or memory for its predetermined or preprogrammed state, as shown in FIG. lo. The windings of the stent rest and press on the wall 86 of WO 95~30385 2 1 8 ~ 3 ~ ~ i .; } , p~

the body cavity 87.~ The 6heath 78, the core 80, and guide-wire 8~ are then withdrawn from the body cavlty 87. Once ~n~l~rl, the open cylindrical lumen of the stent has a diameter larger than both the conical tip 81 and the sheath 78, therefore the instrument 76 can easily be withdrawn without snagging or catching the stent 101.
Due: to the wavy shape oi the windings, the btent provides s~ffn1~1;ng support to m~;ntA;n patency of the body cavity without the body ti6sue col l Are; ng or protruding into the cylindrical lumen of the stent around the wires, as shown in FIG. 11. The epine (not shown in FIGS. 8-11 for reason of simplicity) prevent6 the stent 101 from ~ stretchirlg during the deployment of the stent ae well as over time as the stent rests in the body cavity af ter deployment . The high longitudinal f lexibility of the: stent reduces trauma to the body tissue .
In a further: ~ ~rl; t of the invention, the Gtent can be made of a thermoela6tic shape-memory material that can be rendered soft and 6hrunken at a temperature below normal body temperature, for example, a material that haa a transition temperature of about 30-60~C. A stent made of such a material can be deployed in the bo~dy cavity by an instrument and method as disclosed in U.S. Patent No. 5,037,427 (Harada et al . ), which description relating to the instrument and method of deployment of the 6tent i6 incorporated by ref erence herein .
3 o The number of ~vindings, the longitudinal di6tance between winding6 in the stent, and the number of curvea in a winding can vary depending on f actors such a6 the . dimensions of the body cavity in which the 6tent is to be positioned, the physiological cnntl;t;nn of the tissue in the body cavity, the material selected f or making the stent, and the wire thickness : interloop gap ratio 6elected. FIG. 12 i6 another embodiment of WO g5130385 21 8 9 3 5 4 I ~
23 ~ ~
the stent of the present invention. ThiE stent 201 has two curves or waves 222A, 222B oriented in the same direction in a single winding 210. Such a stent is made by winding on a mandrel 240 having an end view as shown 5 in FIG. 13 and an isometric view of a portion thereof as shown in FIG. 14. The mandrel 240 has rings 242 of ~ _ spikes 244 disposed on the outer surface 2~6 thereof.
Each ring 242 of spikes 244 contains four spikes evenly spaced around the circumference of a circle 10 corresponding to the cross section of the mandrel 240.
As can be seen in FIG. 13 and FIG. 14, the corresponding spikes 244 in different rings 242 are aligned (or arranged) in longitudinal straight lines (or columns) such that viewing f rom the end of the mandrel, only the 15 four spikes proximal to a viewer are visible. However, the spikes in different rings can also be arranged in a regular but nonstraight f ashion instead of in straight columns, for example, as in twisted, parallel lines.
2 0 EXA~PLES
Stents were made according to the procedure described hereinabove each using a gingle c~-n~; nll~U8 piece of superelastic nitinol wire and a mandrel shown in FIG . 4 and FIG . 6 such that each wire was f ashioned into a cylindrical stent about 3 cm long and 0 . 4 cm in diameter in the fully ~ n~d state. A superelastic nitinol wire 8 of 0.1 mm diameter was wound on a generally cylindrical mandrel 40 of about 0 . 4 cm ~=
diameter with rings 42 of spikes 44 disposed about 0 . 5 cm longitudinally apart on the mandrel. Each ring 42 of spikes c~mt~;n~d 6 spikes 44 evenly spaced apart on the circumference (or perimeter) of the ring. Each spike 44 was 1 mm high and had a transverse cross section of 0 . 7mm x 0 . 7mm . Af ter a stent 1 was f ormed on the mandrel and annealed at 500C for 30 minutes, it was placed, compressed and confined (or secured) in the ==
recess space 82 of a catheter-like instrument 76 WO 9S/30385 A .
21893S~ ~2~
described hereinabove for pl ;l~r-^nt or deployment into a coronary artery of a dog. Seven dogs, weighing between 22 Kg and 30 Kg, were used in the study. The stents were deployed in the coronary arteries of the dogs by 5 llt;l;7;n~ a 5 French delivery instrument or catheter (i.e., the sheath has an outside ~; t~r of 1.67 mm) as illustrated in Figs. 8-10. Of the seven dogs, one died during the procedure of placing the stent, six were successfully stented, each with a stent deployed in the 10 coronary artery. The dogs were sacrificed after two to eight months to investigate the patency of the coronary arteries where the stents were deployed. All of the stented arteries we~e found to be patent with minimal intimal hyperplasia (or narrowing). The canine studies 15 were performed according to a protocol approved by the Animal Care Committee (Protocol No. 9011022) of the University of Minnesota.
Referring to FIG. 15, a 3tent 301 of another embodiment has individual windings (or loops) 310 20 wherein adjacent loops are interconnected by a strip (or portion) 362 of wire, which intertwines with a portion of wire 309 that runs along the length of the stent to maintain the geometry of the stent and prevents the longitudinal stretching of the stent. ~ spine is formed 25 by the intertwining of interconnecting portions of wire with the lengthwise-running portion of wire. One or more of the windings (or loops) 310 in the stent can have one or more eyelets 390 ~; Rh;t~n~d in it. The eyelets are little~loops formed on the perimeter of the 3 0 individual windings which are interconnected by the spine 320. A8 shown in FIG. 16, each winding 310 is generally circular ~in outline. An eyelet 390 is formed as a tight turn of ~the wire, forming a small loop on a spike when the stent is wound on a mandrel (not shown).
35 Four eyelets 390 can be formed on a winaing 310, one on the spine 320 and three spaced from the spine.

W0 9sl3o38s ~ 5 ~ F~

Such a stent can be f orm by running a generally straight wire 309 along the length of the mandrel (not shown) and then bendi~g the wire back to run in the opposite direction at the end of the mandrel 5 before forming the first winding 310A. After a winding (e.g. 310A) is formed, the portion of wire (e.g. 362A) interconnecting the previously formed winding (e.g.
310A) and the next winding (e.g. 310B) is intertwined with the generally straight portion 309 (i.e., the 10 portion that runs lengthwise on the mandrel) of the wire. Then the next winding (e.g. 310B) is formed.
The eyelets can function as torsion springs and permit the winding to be collapsed by f lexion at the =
eyelets when the loop or winding is compressed radially.
15 For example, when a winding 310 is compressed by applying force on the eyelet 390A on the spine 320 and the eyelet 390C opposite the spine, the winding will collapse (or flex) about the other eyelets 390B, 390D.
In other words, the generally circular winding will be 20 transformed into two semicircular segments that are hinged to flex in a book-like fashion about the eyelets 390B, 390D adjacent to but spaced from the spine 320 .
Likewise, when the eyelets adjacent to but spaced from the spine 320 are compressed, the winding collapses 25 about the spine and about the eyelet 390C opposite the spine . By compressing the winding to f lex about all the eyelets simultaneously, the winding can be collapsed to a geometry (or size) to fit inside a deployment instrument ( such as the one shown in FIG . 8 ) that 30 constrains the radial dimensions of the stent. A stent, having its windings thus collapsed, can be deployed in a selected site in the body. Upon deployment, the stent can spring back to its unconstrained dimension (i.e.
preprogrammed shape) to m-;nt;~1n the patency of the body 35 cavity or passageway. The eyelets, other than functioning as torsion springs, also help to provide more contact surface area for scaffold-supporting the WO 95/3038~ 2 1 g ~ 3 ~ ~ P~

wall of the body cavity. Such an embodiment would be preferred ior~arge~ stent3 with diameters of l0mm to 30mm .
Variou3 modif ication can be made on the above 5 embodiments. For example, the loop on an eyelet can be wound on a spike clockwisely or counterclockwisely and the number o~~~eyelets on a winding can vary. The eyelet on the spine can be eliminated by, at the beginning and end of a windlng, turning the wire g0 at the spike 10 aligned with the spine instead of forming a loop-shape eyelet thereon. Such a stent can still be collapsed by radial compre3sion. The elimination of this eyelet may also enhance~he longitudinal integrity against stretching. On the other hand, more eyelets can also be 15 made on a winding to provide more pointG upon which the winding can f lex . In ~ 1 t; nn, in closing a winding on the mandrel, a knot~ can be tied after the winding has been wound on the mandrel, securing the two ends of the winding together on the spine. The knot can be but is 20 preferably not tied onto a spike so that the wire on which the knot is tied can be gripped more tightly by the knot to further prevent the longitudinal stretching of the stent. Such a stent with knots for closing windings can even be made without the generally straight 25 wire running ~long the length of the stent for intertwining with the interconnecting portions.
The above embodiment can further be modified, as shown in FIG. 17 by using crimpable (or pinchable) sections 492 of tubing to encircle and hold the 30 interconnecting portions 462 oi the wire onto the generally straight portion 409 of the wire. After a winding (e.g. 420A) is formed, the free ends of the wire (i.e., the free end of the generally straight portion 409 of the wire and the free end of the wire ~tc~n~l;ng 35 from the newly formed winding which will become an interconnecting portion 462 of the wire) are threaded through a section of a crimpable tubing 492 made of a WO 95/30385 , } ~ "

deformable material without shape-memory (e.g., stainless steel, titanium). These free end portions of the wire are then threaded through the section 492 of tubing until the section of tubing is proximate to the 5 newly formed winding (e.g. 420A). Then a tool, such as a pair of crimping pliers (not shown), is used to crimp or pinch the section of tubing 492 onto the portions of wire 80 that they are held f ast by the crimped section of tubing. Likewise,= before a winding (for example, the 10 fir8t winding formed on a stent) is formed, the portions of the wire can be held fast in a similar manner. The stents of the above Pmhn~;r^nts can be made with superelastic nitinol with the ;InnP;~l ;nj method and disassemblable mandrel described hereinabove.
In yet another embodiment, the stent can be made, rather than from a single wire, by fashioning out of larger pieces of material, such a8 punching the desired stent conf iguration out of a single integral piece of material (e.g. a nitinol tube), cutting the 20 desired stent configuration out of metallic structures using dies, or chemically etching out of a tubular structure. Methods of punching, die-cutting, chemical etching, and the like, are known in the art and can be used for making such stents. Stents can be fashioned 25 with such methods to have a structure substantially similar to the single-wired stent described hereinabove.
Such a stent can have a cylindrical body which; n~ PA
a plurality of wavy clo5ed windings (or loops) and strips interconnecting the windings 8uch that the stent 30 is prevented from stretching longitudinally. The strips can be interconnected to form an aligned longitllrlin;~lly oriented spine. Such a stent can be made of the material described hereinabove and can be self-P~r~n~l~hle from a first radially-constrained, lln~rîAn~lpd 35 diameter to a second, radially-unconstrained, `^~r?3n'l~'1 diameter .

WO 95/30385 ~ ~9~ 1 1 218935~ ~ --2'8 ~ :
The~ methods for making the stent of the present invention can also be automated to mass-produce the stent.
It is to be understood that even though 5 numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with detail~ of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, lC especially in manners of shape, size and arrangement of parts without departing from the spirit and scope of the invention .

Claims

WHAT IS CLAIMED IS:

1. A stent, comprising a self-expandable cylindrical body made from a single piece of material, said cylindrical body including a plurality of closed windings and strips interconnecting the windings such that said stent is prevented from stretching longitudinally, said stent being self-expandable from a first radially-constrained, unexpanded geometry to a second, radially-unconstrained, expanded geometry.

2. The stent of claim 1 wherein the strips are aligned to form a longitudinally oriented spine.

3. The stent of claim 1 wherein at least one closed winding is wavy.

4. The stent of claim 1 wherein the cylindrical body is formed from a single piece of wire.

5. The stent of claim 4 wherein at least one closed winding has eyelets about which the winding can be flexed.

6. The stent of claim 4 wherein a portion of the wire extends throughout the length of the stent and intertwines with portions of the wire that integrally interconnecting corresponding adjacent windings.

7. The stent of claim 4 wherein a generally straight portion of the wire extends throughout the length of the stent and said stent further comprising a tubing section encircling a portion of the wire integrally interconnecting adjacent windings and a portion of the straight portion of wire, wherein the tubing section is crimped to secure the portions of wire encircled therein to prevent the longitudinal stretching of the stent.

8. A stent, comprising a self-expandable cylindrical body formed from a continuous wire, said cylindrical body being a coil of successive windings interconnected by portions of the wire such that each of said windings having curves and said stent is prevented from stretching longitudinally as a result of the interconnecting portions of wire, said stent being self-expandable from a first radially-constrained, unexpanded diameter to a second, radially-unconstrained, expanded diameter.

9 . The stent of claim 8 wherein any adjacent first and second successive windings are connected and restrained from stretching longitudinally by a portion of the wire interposed between said first and second successive windings.

10. The stent of claim 9 wherein the portion of the wire interposed between said two successive windings is connected to a first end portion of the first winding and an end portion of the second winding and intertwined with a second end portion of the first winding.

11. The stent of claim 10 wherein the intertwining of the wire interposed between successive windings results in an aligned, generally straight, longitudinal spine in the stent.

12. The stent of claim 8 wherein the wire is made of nitinol.

13. A stent for implantation within a body cavity, comprising a self-expandable cylindrical body formed from a continuous, superelastic nitinol wire, said cylindrical body being a coil having successive sinusoidal-wave-shaped windings and said coil is prevented from stretching longitudinally, said stent being self-expandable from a first radially-constrained, unexpanded diameter to a second, radially-unconstrained, expanded diameter, wherein any adjacent first and second successive windings are connected and restrained longitudinally from stretching by a portion of the wire connected to a first end portion of the first winding and an end portion of the second winding and intertwined with a second end portion of the first winding, the intertwining of the wire interposed between successive windings resulting in an aligned, generally straight longitudinal spine in the stent.

14. A stent, comprising a self-expandable cylindrical body having successive windings of wire, each of said windings having curves, wherein a portion of wire interconnecting two successive windings intertwines with a portion of one of said two successive windings to prevent stretching longitudinally; said stent being self-expandable from a first radially-constrained, unexpanded diameter to a second, radially-unconstrained, expanded diameter.

15. The stent of claim 14 wherein the portion of the wire interconnecting said two successive windings is integrally connected to a first end portion of a first winding and an end portion of the second winding of said two successive windings and intertwined with a second end portion of the first winding.

16. A method of making a stent, comprising winding a continuous wire upon spikes on an elongated mandrel to form a self-expanding shape-memory coil having a plurality of closed windings and strips interconnecting the windings such that said stent is prevented from stretching longitudinally.

17. The method of claim 16 wherein the wire is wound such that the portion of wire connecting any adjacent first and second successive windings is connected to a first end portion of the first winding and an end portion of the second winding and intertwined with a second end portion of the first winding, the intertwining of the wire interposed between successive windings resulting in an aligned, generally straight, longitudinal spine in the stent.

18. The method of claim 16 further comprising annealing the wound coil on the mandrel at an elevated temperature above room temperature.

19. The method of claim 18 wherein the annealing temperature is about 500°C.

20. The method of claim 16 wherein the mandrel is disassemblable to enable release of a formed stent from the mandrel.

21. The method of claim 20 further comprising removing the stent from the mandrel without distorting said stent.

22 A system for positioning in a body cavity a self-expandable stent, comprising:
an instrument for deployment of a self-expanding stent by releasably holding therein the stent in a radially constrained diameter; and a self-expanding stent releasably held by said instrument, said stent comprising a self-expandable cylindrical body formed by a continuous wire which is a coil having a plurality of closed windings and strips interconnecting the windings such that said stent is prevented from stretching longitudinally, said stent being self-expandable from a first radially-constrained, unexpanded diameter to a second, radially-unconstrained, expanded diameter.

23. The system of claim 22 wherein the instrument comprises an elongated tubular outer sheath having a first end and a second end for radially constraining said stent, an elongated core having a first end and a second end movably disposed within said sheath, the first end and second end of the sheath correspond to the first end and second end of the core respectively, said core having means for constraining the stent from moving longitudinally relative to said core, said core being longer than the sheath, said stent being releasably held within a space defined between said sheath and said core, wherein said stent self-expands and is deployed in the body cavity upon moving the sheath longitudinally away from the first end of the core, thereby releasing the radial constraint by the sheath.

24. A method of placing a self-expanding support in a body cavity, comprising:
forming a self-expanding stent comprising a self-expandable cylindrical body formed from a continuous wire, said stent being a coil having a plurality of closed windings and strips interconnecting the windings such that said stent is prevented from stretching longitudinally, said stent being self-expandable from a first radially-constrained, unexpanded diameter to a second, radially-unconstrained, expanded diameter;
releasably securing said stent in an instrument for radially constraining the stent to a first unexpanded diameter;
advancing the instrument with the stent secured therein into a desired location in the body cavity; and deploying the stent from the instrument by releasing the radial constraint by the sheath on the stent and allowing the stent to self-expand to a second expanded diameter.

25. The method of claim 24 wherein the instrument for radially constraining the stent comprises an elongated tubular outer sheath having a first end and a second end for radially constraining said stent, an elongated core having a first end and a second end movably disposed within said sheath, the first end and second end of the sheath corresponding to the first end and second end of the core respectively, said core having means for releasably constraining the stent from moving longitudinally relative to said core, said core being longer than the sheath, said stent being releasably held within a space defined between said sheath and said core.

26. A disassemblable mandrel for forming a stent, said mandrel comprising an elongated body with spikes disposed thereon, said spikes being effective for a wire to be wound thereon to form a stent and said mandrel being disassemblable to release the stent once formed.

27. The mandrel of claim 26 wherein said elongated body can be disassembled without distorting the stent.

28. The mandrel of claim 27 wherein said elongated body comprises of disassemblable longitudinal layers.

29. The mandrel of claim 28 wherein said elongated body comprises an intermediate layer having a transverse, generally rectangular cross section interposed between two external layers each of which has a transverse, generally circle-segment-shaped cross section.

30. The mandrel of claim 29 wherein said elongated body has a transverse, generally circular cross section and wherein the intermediate layer can be removed from the mandrel to enable the exterior layers to be brought together to attain a smaller transverse cross sectional area than that of the mandrel, thereby releasing of the stent from said exterior layers.

31. The mandrel of claim 26 wherein said spikes are movably affixed to said elongated body.

32. The mandrel of claim 31 wherein said spikes are removable from said elongated body.

33. The mandrel of claim 31 wherein said elongated body has a cylindrical outer surface and said spikes can be forced proximate said outer surface to release said stent.