Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
2000-03-02
2002-02-12
Truong, Kevin (Department: 3731)
Surgery
Instruments
Internal pressure applicator
Reexamination Certificate
active
06346117
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an intravascular device used in the treatment of aneurysms, and especially in the occlusion of cerebrovascular saccular aneurysms.
BACKGROUND OF THE INVENTION
Saccular aneurysms occur at the branching of arteries in the body and comprise a sack-like formation of the artery wall which extends outwardly from the bifurcation point between the arterial branches. The aneurysm has a neck forming the juncture with the artery and is capped by a dome. During formation of the aneurysm, the arterial internal elastic lamina disappears at the base of the neck, the sack wall thins and weakens and connective tissue replaces smooth-muscle cells. The aneurysm tends to rupture at the dome and bleeding ensues.
Rupture of a cerebrovascular saccular aneurysm is especially serious due to the associated high mortality rate (10% within the first day of rupture, 25% within three months) and the major neurological deficits experienced by those who survive the initial hemorrhage. Naturally, therapeutic treatment of cerebrovascular aneurysms emphasizes preventing the initial rupture.
Intravascular Catheter Treatment Technique
Intravascular catheter techniques for treating saccular aneurysms are discussed in U.S. Pat. No. 5,122,136, hereby incorporated by reference, and U.S. Pat. No. 6,010,498, also hereby incorporated by reference.
The techniques described in these patents can be summarized with reference to
FIGS. 1 and 2
, which show a saccular aneurysm
20
formed in an artery
22
at a bifurcation point
24
. The treatment techniques involve positioning a catheter
26
at the artery bifurcation point
24
, the catheter tip
28
extending partially into the neck
30
of the aneurysm
20
. Once the catheter is in position, a length of platinum or platinum alloy wire
32
is snaked through the catheter's lumen
34
through the aneurysm neck
30
and into the aneurysm
20
. The wire
32
has a length between 0.4 and 20 inches (1 and 50 cm), is relatively thin (between 0.001-0.005 inches in diameter) and flexible and loops and tangles randomly as it is packed into the aneurysm. Blood which would normally circulate under pressure into the aneurysm, causing it to enlarge, weaken and rupture, begins to form clots
36
on the platinum wire tangle and eventually the clots merge and enlarge to form an occlusion
38
(see
FIG. 2
) which seals off the aneurysm from the blood flow, preventing further enlargement and rupture.
Clotting on the wire
32
within aneurysm
20
is promoted by mechanical and/or electrical means. Forming the wire
32
into a continuous coil having a diameter between 0.010 and 0.020 inches will promote clotting mechanically by providing a multiplicity of adjacent cites on the wire where clots can adhere and join together. Running an electrical current of approximately 0.01 to 2 milliamperes through the wire with the wire forming the anode of the circuit at a positive 0.1 to 6 volts will cause clots to form by the phenomenon of electrothrombosis. Electrothrombosis takes advantage of the fact that white blood cells, red blood cells, platelets and fibrogen are typically negatively charged in blood having normal pH, and these negatively charged components are, therefore, electrostatically attracted to the positively charged wire. The electrostatic attraction of the blood components promotes and speeds the clotting process.
Once the appropriate length of wire is positioned in the aneurysm and the occlusion has been formed, the wire
32
is released at or near the neck
30
of the aneurysm and the catheter is withdrawn (FIG.
2
). Wire release is effected by any one of several means, for example, mechanical means or electrolytic means.
Release of the wire by mechanical means involves another wire (not shown) which is attached in tandem with the platinum wire
32
. The other wire extends through the catheter and provides the means to push the platinum wire through the catheter and into the aneurysm. The other wire has a spring biased mechanical clasp (not shown) at its end which grips an end
40
of wire
32
(see FIG.
2
). The clasp remains engaged with the wire end
40
as long as the clasp remains within the catheter lumen. To release wire
32
, the clasp is temporarily extended from the lumen, the spring biasing opens the clasp and the wire end
40
is released. The other wire and the clasp are drawn back into the catheter lumen, which is then removed from the artery.
For release of the wire by electrolytic means, the end
40
of platinum wire
32
is attached to the other wire by a wire segment formed of stainless steel (not shown). When it is desired to release the platinum wire, the stainless steel segment is positioned outside of the catheter lumen and exposed to the blood stream. Application of an electrical current through the exposed stainless steel portion causes it to corrode away, releasing the platinum wire
32
.
While this catheter technique holds great promise of effective treatment for preventing aneurysm rupture, especially cerebrovascular saccular aneurysms, it has a significant drawback in that it is not always possible to ensure that the entire length of wire
32
remains within the aneurysm. Even if the entire length of wire is successfully positioned wholly within the aneurysm during the procedure, it has been found that the end
40
of the wire can work its way out of the aneurysm over time, extend through the aneurysm neck
30
and protrude into the artery
22
as illustrated in FIG.
2
. Blood flowing through the artery past the wire end will form a clot
36
on the protruding wire end
40
, and this clot could separate from the wire end and cause a stroke or embolism. Statistical results predict that as many as 5% of the patients treated by this technique will suffer complications caused by the wire extending through the aneurysm neck and into the artery. Clearly, there is a need for improving this catheter treatment technique to eliminate the potential for embolisms or stroke as a result of the procedure.
SUMMARY AND OBJECTS OF THE INVENTION
The invention comprises a flexible bag adapted to pass through a catheter lumen and expand upon release from the lumen to substantially occupy a fluid-filled cavity larger than the lumen. The bag is adapted to receive fluid within the cavity. The bag also receives a clotting medium which promotes coagulation of the fluid when in contact with it.
The bag comprises a plurality of interlaced flexible filamentary members and a multiplicity of pores formed by interstices between the interlaced filamentary members. The pores are sized to allow the fluid in the cavity to enter the bag but prevent outward protrusion of the clotting medium out of the bag.
The filamentary members are resiliently biased to assume an expanded first diameter substantially filling the cavity upon release from the catheter lumen. The filamentary members are resiliently deformable to a second diameter smaller than the first diameter, the second diameter being sized to slidingly interfit within the catheter lumen.
Preferably, the bag is used in the intravascular treatment of saccular aneurysms, thus, the aforementioned cavity is the saccular aneurysm, the fluid is blood and the clotting medium comprises a length of wire. The wire length could be contained in the bag while positioned in the catheter or fed into the bag after it is positioned in its expanded diameter within the aneurysm. Preferably, the wire is compatible with human tissue and conducts electricity, thus, allowing a current to be passed to promote clotting by electrothrombosis. Platinum is the preferred wire material because it fulfills the necessary requirements.
Preferably, the wire is fed into the bag through an opening in the bag for receiving the wire. The filamentary members forming the bag are resiliently biased adjacent to the opening to form a constriction in the bag which closes off the opening and prevents the wire from extending outwardly therethrough. The filamentary members are resiliently deformable away from the opening to expand
Prodesco, Inc.
Synnestvedt & Lechner LLP
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