artery or blood vessel on a temporary basis while there
TEMPORARY STENT AND METHODS FOR USE is an immediate risk that the region may collapse. This
AND MANUFACTURE support must be provided until the region is repaired or
stabilized. To provide this support, a device known as a
REFERENCE TO RELATED APPLICATION 5 stent may be installed at the desired region. A stent is a
This application is a continuation in part of Ser. No. device which is used to hold or maintain the diameter of
07/594,121, filed Oct. 9, 1990. the artery or vessel.
„ ,„ „„m „„ „„„ „„,„.TM „ Although some stents are available in the art, these
BACKGROUND OF THE INVENTION ^ gener* ly of ^ type ... for use.
This invention relates to devices known as stents 10 This type of permanent stent is implanted in a patient's
which provide support to a vessel, such as a blood ves- vascular system and remains in place after the proce
sel, and in particular to stents that are both temporary dure or operation. Such permanent types of stents are
and removable. shown, for example, in U.S. Pat. Nos. 4,913,141,
Obstructive coronary artery disease is one of most 4,878,906, 4,856,516 and 4,820,298. These permanent
serious health problems facing our society today. This 15 type of stents may not always be desired for the situa
disease is the result of the deposit of fatty substances on tjons described above. First, it may be unnecessary and
the interior surface of the walls of the arteries. The build even undesirable to install a permanent device when up or lesion of such deposits results in a narrowing of only temporary support is needed. Further, these per
the diameter of the artery which restricts the blood flow manent t of stents ^ a relatively co u.
through the artery. This condition wherein the artery is 20 ^ dure tQ mstaU Fmh uge Qf ^
narrowed is known as stenosis. The lesion may form in ^ fa ... h ^ ohseTvat£a md re.
any part of the artery and in some instances the deposits c ^ Additionally, a complement of drug theramay form at the intersection between two arteries, that . J . , . ,J'
is, where the section where the two arteries form a Pf . required^ order to offset the bioreaction re
generally "Y" configuration (e.g. bifurcate, trifurcate, 25 sultmg in thrombus formation or smooth muscle cell
and so on) proliferation on the stent surface. These drug therapies
There have been significant developments of the may ^ required for a significant period of time until
treatment of such obstructive coronary disease in the new norma1 endothelial cells have formed. In situations
recent past. Coronary artery bypass graft surgery is such as a "bail-out it is desirable for the physician to
often used to treat this disease. Bypass surgery, how- 30 have the ability to quickly maneuver the stent to the
ever, has the disadvantage that it is extremely invasive desired location and quickly and easily place the stent in
and traumatic to the patient. Some of the recent devel- its operating mode.
opments provide a less invasive and less traumatic alter- A temporary stent on the other hand may be particu
native to bypass surgery. Two of these recent develop- larly useful in situations where it is intended to be used
ments are known as angioplasty and atherectomy pro- 35 in the patient only for several minutes or days and then
cedures. removed. For example, use of a temporary stent in a
Angioplasty is a procedure in which a balloon is bail-out situation will enable the physician to defer a
positioned on the inside of the artery at the site of the more complicated procedure until a patient's condition
lesion and expanded in order to compress the materials is more stable, or in some cases eliminate further proce
at the lesion and thus open the restricted area in the 40 dures by resecuring the vessel geometry which allows
artery. In this procedure, an elastic balloon is attached near normal blood flow.
to one end of a small diameter flexible catheter which A temporary stent may have particular usefulness in
includes means for inflating the balloon from the other situations such as when an intimal flap is encountered or
end of the catheter. The catheter is maneuvered during occurrrences of vasoconstriction or vasospasm
through the patient's vessels to the site of the lesion with 45 Qr m situations in which there is a potential for such
the balloon m uninflated form. When the umnflated conditions to occur such as following angioplasty. An
balloon is properly positioned at the lesion, the balloon mtimal fl QCCaa when a ion of ^ vessd wall is then inflated to dilatate the restricted area. iall Qr letel tears off wd h down ^
Atherectomy is a procedure in which a small cutting ^ ... flow h An fl ... ...
tool is attached to the end of a small diameter flexible 50 - ... , S... „ . ,
it_ „ , . A, , x. .,, . . . or after an angioplasty procedure. If the flap is large, it
catheter and maneuvered through the patient s arterial .. , ° , , T . , __f „ °
... .. c. . . j. j . may entirely occlude the vessel lumen. The flap may
system to the site of the lesion m the diseased artery. , , . .. .i . , . ^ . , . , . *\'
,i7, t, *„ i • l ~a ■» heal itself if it can be maintained in place against the
When the cutting tool is properly positioned, the tool is . . ,. , . * 6
used to cut and remove the deposits from the surface of vessel trom which it tore.
the diseased artery 55 Vasoconstriction or vasospasm also may occur dur
Although these two procedures provide less trau- in8 or after angioplasty. Vasoconstriction or vasospasm matic alternatives to bypass surgery, they are not with- m manv cases may. accompany the occurrence of an out risk. It is possible that following procedures such as mtlmal flap, but in many other cases, vasoconstriction angioplasty or atherectomy the artery or blood vessel or vasospasm may occur independent of an mtimal flap, may collapse or be susceptible to constriction. In some 60 During vasoconstriction or vasospasm, muscles around instances it may also be necessary to abort or "bail-out" the vessel contract and can partially or completely Deprocedures such as angioplasty or atherectomy due to elude the vessel. If the vessel can be maintained open, some type of unexpected complication. vasoconstriction or vasospasm may cease after a period
In these situations it is necessary to maintain the in- of time. Medicines may be administered to treat the tegrity of the region of the artery until the artery is 65 vasoconstriction or vasospasm. Whereas a small force repaired or stabilizes. That is, following some angio- may be sufficient to maintain an intimal flap against the plasty or atherectomy procedures or in a "bail-out" vessel wall and maintain blood flow, a significantly situation, it may be necessary to provide support to a greater force would usually be needed to keep a vessel