Method and apparatus for intravasculer embolization

Disclosed is a method and apparatus to treat an aneurysm. The method involves the introduction of an embolic material into the aneurysm. The embolic material is adapted to permit tissue ingrowth within the region defined by the aneurysm, which results in treatment of the aneurysm. Preferred embolic materials are those having an open cell structure, such as polyvinyl alcohol foams. Also disclosed is a catheter which may be used to introduce an embolic material into an aneurysm.

FIELD OF THE INVENTION 
The present invention relates to intravascular embolization, and in one 
application, to a method and apparatus for inserting material into an 
aneurysmal sac to promote thrombus formation or other healing mechanisms 
within the sac, thereby treating the aneurysm. 
BACKGROUND OF THE INVENTION 
An aneurysm is a balloon-like swelling in the wall of a vessel. An aneurysm 
generally results in weakness of the vessel wall in which it occurs, which 
predisposes the region to a tear or rupture, with potentially catastrophic 
consequences for the patient. For example, if an aneurysm is present 
within an artery in the brain, and should burst under blood pressure, 
cranial hemorrhaging, and perhaps death, may occur. 
Aneurysms may result from a variety of causes. For example, an aneurysm may 
result from trauma, from a degenerative disease which damages the muscular 
coat of a vessel, or it may be the result of a congenital deficiency in 
the muscular wall of the artery. 
A variety of methods and apparatus have been used to provide an artificial 
structural support to the vessel region affected by the aneurysm, to 
minimize the effect of blood pressure and impact pressure within the 
aneurysmal sac, and thus prevent or minimize the chance of rupture. For 
example, U.S. Pat. No. 5,405,379 to Lane discloses a self-expanding 
cylindrical tube which is intended to span the aneurysm, resulting in 
isolation of the aneurysm from blood flow. One drawback with such devices, 
however, is that while they may reduce the risk that the aneurysm might 
rupture, they do not necessarily promote a healing response within the 
aneurysm. In addition, indwelling stents may increase the risk of 
thrombosis or embolism, and the wall thickness of the stent may 
undesirably reduce the fluid flow rate in the vessel. Indwelling stents or 
bypass structures are also generally straight along their length and 
cannot always be used to treat aneurysms at a bend in the artery or in 
tortuous vessels such as in the brain. 
Another approach to the treatment of vascular aneurysms has been the use of 
vaso occlusion coils. In general, this technique involves the implantation 
of coiled fine metal wire into the aneurysm, to inhibit the flow of red 
blood cells. This can in turn promote thrombus formation. See, for 
example, U.S. Pat. No. 5,304,194 to Chee, et al.; U.S. Pat. No. 5,304,195 
to Twyford, Jr., et al.; and U.S. Pat. No. 5,354,295 to Guglielmi, et al. 
However, this technique leaves a metal coil implanted within the patient 
which may compact, and migrate over time, and does not optimize the body's 
natural healing processes. 
Thus, there exists a need for a method and apparatus for treating an 
aneurysm which takes advantage of the body's own healing responses to 
treat the aneurysm. Preferably, the treatment minimizes any interference 
with blood flow in the adjacent vessel, is useful in small diameter 
vessels, and can be used to treat aneurysms located on either straight or 
curved portions of the adjacent vessel. 
SUMMARY OF THE INVENTION 
The present invention provides a method and apparatus for treating 
aneurysms which advantageously utilizes the body's own thrombic responses 
to treat an aneurysm. 
There is provided in accordance with one aspect of the present invention an 
expandable plug for treating a vascular aneurysm. The plug comprises a 
biocompatible material which is expandable from a first, constrained 
volume to a second, larger volume. Before placement at the treatment site, 
the expandable material is in the first, constrained volume and restrained 
therein by a blood-soluble restraining agent. 
Preferably, the expandable material comprises an open-cell structure foam. 
In one embodiment the expandable material comprises crosslinked polyvinyl 
alcohol. The blood-soluble restraining agent comprises any of a variety of 
agents which are soluble in blood, such as polyvinyl alcohol, polyvinyl 
pyrrolidone, gelatin, or dextrose. 
In accordance with another aspect of the present invention, there is 
provided a combination of a transluminal delivery wire and an expandable 
plug for treating a vascular site. The combination comprises an elongate 
flexible delivery wire having proximal and distal ends, and an expandable 
plug on the distal end of the delivery wire. The plug is expandable from a 
first, introduction volume to a second, expanded volume upon exposure to a 
body fluid. The expandable plug is initially releasably secured to the 
delivery wire in the first, introduction volume. The plug is released from 
the delivery wire and expands to the second, expanded volume upon exposure 
to a body fluid, and dissolution of the blood soluble restraining agent. 
In one embodiment the expandable plug comprises a plurality of particles 
which are compressible from an expanded volume to a compressed volume. In 
another embodiment, the plug comprises a single particle of open cell foam 
material. 
In accordance with a further aspect of the present invention, there is 
provided a method of making an expandable plug for delivery to a vascular 
aneurysm. The method comprises the steps of providing an elongate flexible 
delivery wire having proximal and distal ends, and providing an expandable 
plug material which is expandable from a first, compressed volume to a 
second, expanded volume. The material is exposed to a blood soluble 
restraining agent and compressed into the first, compressed volume and 
placed in contact with the distal end of the delivery wire. The 
restraining agent is permitted to restrain the material in the first, 
compressed volume and in contact with the delivery wire. 
In accordance with a further aspect of the present invention, there is 
provided a method of delivering an expandable material to a treatment site 
within a vessel. The method comprises the steps of providing an elongate 
flexible delivery device having proximal and distal ends and an expandable 
material at the distal end. The distal end is transluminally advanced and 
positioned such that the material is at the treatment site. The material 
is exposed to a body fluid, causing blood to dissolve the restraining 
agent and the material to expand at the delivery site. 
Further features and advantages of the present invention will become 
apparent to those of skill in the art in view of the disclosure which 
follows, when considered together with the attached drawings and claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, there is depicted catheter 10 for delivering the 
embolic plugs of the present invention. Although illustrated in a context 
of a simple catheter, having a single lumen (FIG. 4) or having a single 
guidewire lumen and a single delivery wire lumen (FIGS. 1-3 and 5), it is 
to be understood that the present method of treating aneurysms can readily 
be adapted to a wide variety of catheter structures, including those 
capable of performing additional functions not described herein. 
Similarly, although the present invention will be described primarily in 
the context of treating vascular aneurysms, the present inventors 
contemplate much broader potential applicability to any of a variety of 
conditions which would benefit from intravascular embolization as will be 
appreciated by those of skill in the art. 
For example, the embolic delivery catheter may also be provided with an 
inflatable balloon and an inflation lumen, to permit vascular dilatation 
as is understood in the art. In addition to or instead of balloon 
dilatation capabilities, an inflatable balloon may be used to assist in 
holding the catheter in position while embolic plug is expressed into the 
aneurysm. A distal inflatable balloon may also be utilized to permit the 
catheter to float downstream directed by blood flow to position the 
catheter, as will be understood by those of skill in the art. 
The catheter may also be provided with a delivery lumen with distal 
delivery openings through the wall of the catheter to enable the site 
specific introduction of medication, contrast media or other fluids. 
Catheters having any of a variety of functional capabilities can readily 
be adapted for use with the apparatus and method of the present invention, 
as will be apparent to those of skill in the art in view of the disclosure 
herein. 
Catheter 10 generally comprises an elongate flexible tubular body 12 
extending between a proximal control end 14 and a distal functional end 
16. The length of the tubular body 12 depends upon the desired 
application. In general, tubular body 12 will have a generally circular 
cross-sectional configuration with an external diameter within the range 
of from about 0.026 inches to 0.065 inches for most cerebral vascular 
applications. Alternatively, a generally triangular cross-sectional 
configuration can also be used, depending upon the number of lumen in the 
catheter, with the maximum base to apex distance also generally within the 
range of from about 0.030 inches to about 0.065 inches. Other noncircular 
catheter configurations, such as rectangular or oval, may also be used to 
introduce the embolic plugs of the present invention. In peripheral 
vascular applications, tubular body 12 will typically have an outside 
diameter within the range of from about 0.026 inches to about 0.091 
inches. 
The present invention is particularly suited for treating intracranial 
vascular aneurysms. For intracranial applications, the percutaneous access 
site is generally the femoral artery. Catheters having an axial length 
within the range of from about 150 cm to about 175 cm are generally 
preferred for this application. The maximum outside diameter of at least 
the distal segment of the catheter is limited by the inside diameter of 
the target vessel. In general, catheters having a diameter of no more than 
about 0.052 inches, and preferably no more than about 0.038 inches are 
preferred for most intracranial applications of the present invention. 
Catheters having diameters outside the ranges recited above may also be 
used with the embolic plugs of the present invention, provided that the 
functional consequences of the diameter are acceptable for the specific 
intended use of the catheter. For example, the lower limit of the diameter 
for tubular body 12 in a given application will be a function of, among 
other things, the number of desired functional lumen contained in the 
catheter. 
In addition, tubular body 12 must have sufficient structural integrity 
(i.e., "pushability") to permit the catheter to be advanced to distal 
arterial locations without buckling or undesirable bending of tubular body 
12. The ability of tubular body 12 to transmit torque may also be 
desirable, such as in those embodiments where it may be desirable to 
rotate the tubular body 12 after insertion, as for example, to facilitate 
advancing a plug introduction wire laterally into an aneurysmal sac, as 
discussed below. 
Catheters having larger tubular body diameters may be provided with larger 
internal lumen, thereby facilitating movement of wires or fluids therein, 
but such larger diameters will tend to reduce perfusion in the artery in 
which the catheter is placed, and for certain applications, will be too 
large to be used in small diameter vessels. Increased diameter catheter 
bodies also tend to exhibit reduced flexibility, which can be 
disadvantageous for treatment of aneurysms in a remote or tortuous 
vascular location. 
The proximal end 14 of catheter 10 may be provided with a manifold 18 
having one or a plurality of access ports, as is known in the art. As 
depicted in FIG. 1, manifold 18 is provided with a guidewire port 20 in an 
"over-the-wire" guidewire embodiment. Manifold 18 also features a side 
port 22 for introduction of a plug delivery wire 29 in a dual lumen 
embodiment. 
The distal end 16 of the catheter 10 is preferably provided with an 
atraumatic distal tip 36, as is known in the art. One or more radiopaque 
markers may also be provided to facilitate positioning of the catheter. 
Radiopaque markers may be provided proximally and distally of exit port 
64, (in a laterally opening embodiment) so that exit port 64 may be 
readily positioned adjacent an aneurysmal sac. Suitable marker bands can 
be produced from any of a variety of materials, including platinum, gold, 
and tungsten.backslash.rhenium alloy, and alloys thereof. 
Referring to FIGS. 1 and 2, guidewire port 20 is in communication with a 
guidewire lumen 35, which extends axially along the length of catheter 10. 
An opening 38 is provided at or near the distal end of the catheter for 
providing exterior access to the guidewire lumen 35. The proximal 
guidewire port 20 may be eliminated from manifold 18 in a rapid-exchange 
or "monorail" embodiment, in which embodiment the proximal opening of the 
guidewire lumen 35 is positioned along the side of tubular body 12. The 
proximal guidewire access port in a rapid exchange embodiment for coronary 
vascular applications is typically within about 20 cm from the distal end 
of the catheter. 
Plug wire port 22 is in communication with lumen 26, which extends axially 
along the length of catheter 10 in a dual lumen embodiment. An exit port 
28 is provided at or near the distal end 16 of catheter 10 to permit the 
distal end of plug wire 29 to exit the tubular body and enter the 
aneurysm. 
As illustrated in FIG. 2, plug wire 29 is slidably receivable within lumen 
26. An embolic plug 40 is attached to the distal tip of plug wire 29 in a 
manner which permits release of embolic plug 40 from wire 29 when wire 29 
is exposed to body fluids, such as blood or plasma. 
The embodiment illustrated in FIGS. 2 and 3 is a side by side dual lumen 
catheter. This catheter may be desirable in applications where a guidewire 
is utilized to assist in advancing the catheter to the treatment site, and 
in which the clinician desires that the guidewire be left in place 
throughout the procedure. A separate lumen is therefore desirable to 
permit distal advance of the plug introduction wire 29. 
Alternatively, the plug introduction wire is introduced through the same 
lumen as the guidewire. Referring to FIG. 4, there is disclosed a distal 
section of a single lumen catheter 60 useful for this purpose. This 
catheter design may be desirable in applications where a guidewire is not 
necessary to advance the distal tip of the catheter to the treatment site. 
Alternatively, the embodiment of FIG. 4 may be utilized where the catheter 
is advanced over a guidewire to the treatment site, but the guidewire may 
be removed following proper placement of the catheter. Central lumen 62 is 
then available to receive the plug introduction wire axially therethrough. 
The introduction wire is then advanced distally through the lumen, and the 
distal plug is positioned in the aneurysm. Upon exposure to blood, the 
plug expands in the aneurysm and is released from the wire. 
One advantage of catheters built in accordance with the design of FIG. 4 is 
that the outside diameter of the catheter may be minimized due to the 
single lumen construction. Single lumen construction may be utilized in 
catheters either designed for sequential guidewire and plug introduction 
wire use, as described above, or also for simultaneous guidewire and plug 
introduction wire use. Thus, the inside diameter of lumen 62 may be 
sufficiently large to accept both a placement guidewire and a plug 
introduction wire in a slidable side by side relationship within lumen 62. 
Preferably, the single lumen embodiment of FIG. 4 has an internal diameter 
which is no larger than necessary to slidably receive the plug wire having 
a plug in the reduced, introduction diameter thereon. Particularly for 
cranial vascular applications, the outside diameter of the introduction 
catheter is preferably minimized. In a single lumen catheter of the type 
illustrated in FIG. 4, the proximal manifold may be simplified by 
eliminating the side port 22. Alternatively, a side port may be provided, 
if desired, to permit introduction of a contrast media through the central 
lumen 62 such as to permit fluoroscopic evaluation of the size of the 
aneurysm. 
Referring to FIG. 5, there is disclosed an alternate dual lumen embodiment 
of the introduction catheter of the present invention. This embodiment is 
similar to that illustrated in FIG. 2, except that the distal opening 64 
of plug introduction wire lumen 66 opens laterally from the side of the 
catheter 68. A gentle lateral ramp 70 may also be provided to assist in 
launching the plug introduction wire in a lateral direction relative to 
the catheter. 
The catheters illustrated in FIG. 2 through 5 can be constructed in any of 
a variety of manners well known in the catheter construction art. For 
example, the catheter of the present invention may be produced by 
extrusion techniques using high or medium density polyethylene or any of a 
variety of other catheter body materials well known in the art. 
Alternatively, the catheter body may be fabricated such as through the use 
of wire wound or polymeric ribbon wound coil structures. The selection of 
any particular catheter body construction technique will be governed by 
the intended use of the catheter, and the resulting dimensional and 
physical property requirements imposed by that use as has been discussed. 
Aneurysms may form at any of a variety of locations within the vascular 
system. For example, an aneurysm may form on the side wall of a relatively 
straight arterial flow path. See, for example, FIG. 6a. This type of 
aneurysm can be accessed either by a catheter or introduction wire which 
can advance in a lateral direction relative to the longitudinal axis of 
the vessel or by a very flexible distal tip catheter. 
Lateral launching of the embolic plug can be accomplished through the use 
of a catheter having a lateral opening therein, and/or by the use of a 
thrombic plug wire having a laterally bent distal tip. Similarly to the 
memory contained in most guidewires, a prebent distal tip on the delivery 
wire of the present invention will tend to exert a lateral biasing force 
against the wall of the delivery lumen. Once the wire is advanced distally 
out of the catheter, the prebent tip will tend to return to its prebent 
configuration, thereby exerting a lateral bias against the wall of the 
vessel. In this manner, and by torquing the wire to assume the proper 
rotational orientation, the plug can be steered into an aneurysm. The use 
and functionality of prebent distal tips on guidewires will be well 
understood to those of ordinary skill in the art in view of conventional 
percutaneous transluminal coronary angioplasty guidewire placement 
techniques. 
Aneurysms occasionally form at a branch point where a single artery divides 
into two or more branches. See, for example, FIGS. 7 (bifurcation 
aneurysm) and 8 (terminal aneurysm). Due to the pressure exerted by blood 
flow, such aneurysms often form directly in the line of flow of blood from 
the primary artery, in between the two branches. This type of aneurysm can 
be readily accessed by a distally opening catheter such as that 
illustrated in FIG. 2 or FIG. 4. 
As will be discussed below, the preferred plug material is a compressed 
crosslinked PVA foam material which will expand and become disassociated 
from the introduction wire upon contact with blood or other bodily fluid 
and dissolution of restraining agent. Thus, the compressed PVA foam or 
other particles should not have a sufficient exposure to blood prior to 
placement within the aneurysm or the plug may prematurely expand. A 
variety of features of the catheters, plug coating and or methods of the 
present invention can be utilized to minimize the risk of premature 
expansion or disassociation of the embolic material. 
In one embodiment, a liquid-tight pierceable membrane (not illustrated) is 
placed over exit port 28 or 64, such that the plug introduction lumen is 
not exposed to internal body fluids until delivery wire 29 is forced 
distally through the membrane. In this embodiment, the membrane may 
function to protect certain types of embolic materials useful for 
practicing the present invention from expanding prematurely, as will be 
discussed below. The membrane may be fashioned out of any of a variety of 
pierceable biocompatible materials known to those of skill in the art, 
such as polyethylene or polypropylene, and be attached by bonding or 
fusion, or be integrally formed with the catheter tubular body. The 
membrane is preferably fluid tight, and also pierceable by wire 29 without 
displacing any embolic material attached to wire 29. 
Alternatively, a biodegradable or soluble membrane or plug may be 
positioned in the distal end of the delivery lumen. By gradually 
dissolving upon contact with blood, the plug would provide a sufficient 
barrier between the embolic inside the catheter and the blood stream to 
permit placement of the catheter. The thickness and composition of the 
membrane or plug can be selected to provide a predetermined dissolution 
time to permit catheter placement before the embolic material becomes 
exposed to blood. 
By sealing the proximal opening of the delivery lumen around the delivery 
wire, a hydrostatic lock of a small volume of a biologically compatible 
fluid which will not readily dissolve the restraining agent such as 
saline/glycerine can be maintained in the catheter at least between the 
distal end of the delivery wire and the distal opening of the delivery 
wire lumen. A slight positive pressure on such a protective fluid can also 
be maintained. Following placement of the catheter, the delivery wire can 
be advanced distally out of the distal end of the catheter and into the 
aneurysm. 
As a further alternative, the delivery wire having embolic material secured 
thereto can simply be maintained apart from the catheter, and only 
inserted into the catheter and advanced transluminally to the aneurysm 
after the catheter has been appropriately positioned within the vessel. 
The embolic materials useful for practicing the present invention are 
preferably biocompatible materials having an open cell structure to which 
cells may bind to stimulate embolization and thrombosis. Although a wide 
variety of materials may be used, certain properties appear desirable. For 
example, low compression set materials are preferred. Molecular weights 
typically will fall within the range of from about 50,000 to 500,000 and 
preferably from about 100,000 to about 200,000. A modulus within the range 
of from about 10,000 to about 100,000 psi and preferably no more than 
about 50,000 psi. Substantially open cell foam structure is preferred, and 
as high as 90% open cell or even higher is preferable. 
Presently preferred materials include crosslinked polyvinyl alcohol (PVA) 
foam, also known as Ivalon, polyurethane foam, polyethylene foam, silicone 
foams or fluorinated polyolefin foams. A variety of other biodegradable 
materials may also be used. Biodegradable for the present purpose 
generally means degraded/eroded in the body over a period of a few days to 
several months. These materials are selected with the expectation that 
they will be non-permanent in specific clinical situations. Suitable 
biodegradable materials for this purpose include gelatin--(Gelfoam); 
collagen--(Avitene); oxidized, modified cellulose--(Oxycel); poly lactic 
acid, glycolic acid and copolymers; polycaprolactone and copolymers; poly 
ethylene glycol, propylene glycol and copolymers; polyvinylpyrrolidone and 
copolymers; poly (vinyl alcohol) and copolymers; and modified starches. 
Autologous tissue (clot, fat, etc.) may not be appropriate in a foam 
structure, but may be compressible and useful in some applications. As 
will be appreciated by one of skill in the art in view of the present 
disclosure, any of a variety of materials which permit or facilitate 
embolization may be used in place of PVA foam. 
When PVA foam is used to make embolic plug 40, it is preferably formed into 
roughly spherical pellets having uncompressed diameters which range from 
about 1 mm to about 10 mm, more preferably from about 3 mm to about 6 mm, 
and most preferably from 3-4 mm in diameter. A sufficient number of 
pellets to produce the desired total expanded volume is then secured to 
the delivery wire as discussed below. Other pellet sizes may be 
appropriate for other embolic plug materials depending upon 
compressibility and expansion characteristics, as can be readily 
determined by one of skill in the art for a given application. It should 
be appreciated, that the particles used to form embolic plug 40 may be 
formed in any of a variety of shapes, such as cubes, cylinders, or 
nonregular shapes, and may still be used to practice the present 
invention. 
As will be appreciated by those of skill in the art, the number of 
particles utilized to construct a plug 40 may be varied considerably, 
depending on a variety of considerations such as the size of the aneurysm 
to be treated, the composition of the particles, the desired time release 
characteristics of the plug or others that will be understood by those of 
skill in the art. A single particle of material sized to treat the 
aneurysm may desirably minimize the risk of post-installation migration. 
For certain applications, it may be desirable to use particles of larger 
sizes than those described, such as when treating giant aneurysms. The 
optimal size of the particle or particles for a desired plug will depend 
in part upon the relative compressibility of the material selected and the 
size of the intended aneurysm to be treated. For example, a single foam 
particle having an expanded cross section on the order of no more than 
about 12 mm may be useful to treat small aneurysms. Large aneurysms may 
use a particle having a cross section within the range of from about 12 mm 
to about 24 mm and particles greater than about 25 mm may be used to treat 
giant aneurysms. Optimization of particle and plug size in view of a 
particular compressible material and particular aneurysm can be readily 
accomplished by one of skill in the art in view of the disclosure herein. 
Embolic plug 40 may be attached to wire 29 by any of a variety of ways 
which permit the clinician to release the plug 40 at the desired location. 
In one method of attachment, one or more roughly spherical embolic 
particles are formed from crosslinked PVA foam, and are wetted with a 
blood soluble restraining agent, such as a 10-20 weight % concentration 
aqueous solution of polyvinyl alcohol or polyvinyl pyrrolidone. The 
desired volume of one or more moistened particles are then placed adjacent 
to plug wire 29 and the assembly is inserted into a press. The particles 
are compressed onto the surface of the wire, reducing their size by a 
factor of at least about 5 and preferably from about 10 to 15, and are 
then allowed to dry. Once dry, the restraining agent functions to retain 
the particles in the compressed state and in attachment to wire 29 in the 
form of an expandable plug. However, because the restraining agent is 
blood soluble, once wire 29 bearing plug 40 is exposed to blood within the 
body, plug 40 will reconstitute to the uncompressed state. Moreover, the 
restraining agent bond between plug 40 and wire 29 will be broken, 
releasing plug 40 within the aneurysm. 
In one embodiment, the compressed embolic material is provided with a time 
release coating which may be the same as or in addition to the restraining 
agent. The time release coating may be applied such as by dipping or 
spraying processes as can be readily devised by those of skill in the art. 
The coating composition and thickness is selected to permit a 
predetermined exposure time to blood before it is dissolved sufficiently 
to permit expansion of the embolic plug. In this manner, the invention can 
be readily practiced without the need for specially designed introduction 
catheters. 
In an alternate mode of the invention, the embolic plug is expandable from 
the first, reduced volume to the second, implanted volume without the need 
for a chemical restraining agent. In this embodiment of the invention, the 
embolic plug material is compressed and loaded into a delivery catheter 
such as central lumen 62 of catheter 60 (FIG. 4). The catheter 60 
functions as a restraining sleeve, to restrain the embolic material in its 
compressed form. Following placement of the distal end of the catheter at 
or about the opening to the aneurysm, a pushwire is advanced distally 
through the central lumen 62 to push the compressed embolic material out 
the distal end of the catheter. Other restraining sleeve variations for 
restraining the compressed embolic material in its compressed 
configuration will be readily apparent to those of skill in the art in 
view of the disclosure herein. 
One advantage of the expandable foam embolic material of the present 
invention over prior art expandable indwelling materials is the relatively 
low radially outwardly directed biasing force exerted by the reconstituted 
foam. One disadvantage of memory metal coils and other self expanding gels 
is the possibility of exerting an excessive radially outwardly directed 
force upon expansion. Excessive forces can increase the risk of rupture, 
particularly if the expanded volume of the material is to large for a 
particular aneurysm. The relatively low force exerted by the expanding 
foam of the present invention minimizes the risk of rupture or dissection 
of the artery as a result of the expansion. 
Due to the variation in size and configuration of aneurysms from patient to 
patient and from aneurysm to aneurysm, delivery wires having an expandable 
material thereon are preferably provided in an array of different 
implantation and expanded sizes for selection by the clinician. For 
example, wires having an expanded volume foam as low as about 0.015 cc, 
and as high as about 8 cc in an unconstrained expansion may be provided. 
Intermediate volumes may also be provided, so that the clinician has a 
series of graduated plug wires to choose from. 
In general, the clinician will select a plug which has an expanded volume 
in the unconstrained state of greater than the anticipated volume of the 
aneurysm to reduce the risk of migration out of the aneurysm. For example, 
the unconstrained expanded plug volume may exceed the aneurysm volume by 
as much as about 25% or greater. The size of the aneurysm can be 
approximated fluoroscopically with injection of contrast media into the 
aneurysm, as will be understood by those of skill in the art. The 
relatively low expansive force of the preferred expanded foam enables the 
use of larger volume foams which, when constrained by the aneurysm, stop 
expanding and conform to the interior thereof. 
The use of the embolic plug wire 29 and plug 40 of the present invention in 
the context of treating a vascular aneurysm can be readily understood by 
reference to FIGS. 6a and 6b. Referring to FIG. 6a, there is illustrated a 
section of tissue 42 having a vessel such as an artery 44 extending 
therethrough. A portion of the wall of the vessel 44 has formed an opening 
46 into an aneurysm 54. In this illustration, a prebent plug wire 29 has 
been navigated through the opening 46 and into the aneurysm 54. The plug 
wire 49 is provided with an expandable plug 40, illustrated in its 
reduced, introduction volume. The particular introduction catheter 
utilized to facilitate placement of the plug 40 within the aneurysm 54 is 
relatively unimportant, and was therefore not illustrated in FIG. 6a. 
In practice, the clinician inserts an introduction catheter using standard 
medical procedures known to those of skill in the art, and positions the 
catheter such that a distal opening on a delivery lumen is adjacent the 
aneurysm 54. If necessary, plug wire 29 may be prebent and rotated 
(torqued) so that the distal tip of plug wire 29 faces the aneurysmal 
opening. Plug wire 29 is then advanced so that the distal tip of plug wire 
29 enters the aneurysmal sac 54. See FIG. 6a. 
The embolic plug 40 will begin to expand when exposed to the bodily fluids 
contained in the aneurysmal sac 54. Expansion can commence almost 
immediately or after a time delay depending upon the restraining agent and 
degree of compression. As plug 40 expands, it will detach from wire 29 and 
continue to expand until it reaches its native size and configuration, or 
its expanded configuration as constrained by the surrounding anatomy. See 
FIG. 6b. 
Wire 29 is withdrawn back through opening 46, leaving the embolic plug 40 
in place within the aneurysmal sac 54, and the catheter and wire assembly 
29 is removed. Because of the open cell structure of the embolic plug, it 
is readily invaded by fibrous tissues, and will promote embolization 
within the aneurysmal sac. Clot promoting agents such as fibrin, 
fibrinogen or thrombin can be impregnated into the foam structure to 
enhance embolization as will be appreciated by those of skill in the art. 
Compressed crosslinked/polyethylene, PVA, or other expandable foam plugs 
can be delivered using vehicles other than attachment to a delivery wire. 
For example, a compressed foam plug can be inserted into the proximal end 
of a delivery lumen and advanced transluminally in a distal direction to 
the treatment site using a pusher wire. Alternatively, the compressed foam 
plug can be prepositioned within the delivery lumen such as at the point 
of manufacture, and pushed from the distal opening of the lumen and into 
the aneurysm using a pushwire, or by the introduction of pressurized 
fluids such as saline behind the plug to advance the plug distally from 
the catheter into the aneurysm. 
A variety of alternative materials can be utilized for making an 
aneurysm-treating plug, as long as the material can be provided in a 
manner that is introducible in a first, reduced volume and capable of 
growing to a second, larger volume within the aneurysm. In addition, the 
particle or particles which are compressed to form a plug can be 
impregnated with a drug for localized drug delivery at the treatment site. 
Open-cell foam structures can be immersed in an aqueous solution of the 
drug prior to compression into an aneurysm-treating plug. Alternatively, 
any of a variety of known binding techniques for releasably binding a drug 
to a carrier can be utilized, as will be apparent to those of skill in the 
art. 
In addition, any of a variety of restraining agents or cements can be 
utilized, depending upon the underlying particle composition and 
structure. Selecting an appropriate plug material and restraining agent 
pair can be readily accomplished through routine experimentation by those 
of skill in the art. Suitable restraining agents for use with PVA plugs, 
for example, include gelatin, natural gums, dextrose, sugar, 
polysaccharides (HEstarch), water soluble polymers and others which can be 
identified through routine experimentation. 
Plug material, structure and compression can affect the length of time 
between the first exposure to blood and the time that the plug is fully 
expanded within the aneurysm. For example, tailoring the compression 
ratio, such as by compressing the material to a greater density, can 
prolong the length of time required to fully release once exposed to an 
aqueous media. As an alternative, or in addition to increased compression, 
additional layers of the restraining agent can be applied over the 
compressed plug to slow the release time for the plug. The concentration 
of the restraining agent can also be increased to delay the onset of or 
slow plug expansion, and the chemical composition of the restraining agent 
can be modified to reduce its rate of solubility in blood. 
Depending upon the particular combination of restraining agent, 
compression, and concentration or loading of the restraining agent, any of 
a variety of desired release times can be obtained. In general, it is 
presently preferred that the expansion time for the plug fall within the 
range of from about 30 seconds to as much as 15 minutes, depending upon 
the mode of delivery of the plug and how long it will likely be exposed to 
blood before the clinician will have ample time to properly position the 
plug within the target aneurysm. 
It will be appreciated that certain variations of the present invention may 
suggest themselves to one of ordinary skill in the art. The foregoing 
detailed description is to be clearly understood as given by way of 
illustration, the spirit and scope of this invention being limited solely 
by the appended claims.