Methods for delivering in vivo uniform dispersed embolic...

Details Methods for delivering in vivo uniform dispersed embolic... Methods for delivering in vivo uniform dispersed embolic...

2000-05-19

2002-09-24

Low, Christopher S. F. (Department: 1653)

Surgery

Means for introducing or removing material from body for...

Material introduced into and removed from body through...

C604S041000, C604S030000, C424S009411, C424S078370, C424S423000, C424S484000, C514S002600, C514S021800

Reexamination Certificate

active

06454738

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to methods for delivering in vivo uniform dispersed embolic compositions of high viscosity. These methods can be used in the treatment of aneurysms, AVM and high flow fistulas.
In one embodiment, the methods of this invention comprise heating to above about 40° C. while mixing a high viscosity composition comprising a biocompatible polymer, a biocompatible solvent and a biocompatible contrast agent. Heating and mixing is continued until a uniform suspension is formed and the heated suspension is then transferred to a catheter for vascular delivery.
2. References
The following publications are cited in this application as superscript numbers:
1
Mandai, et al., “Direct Thrombosis of Aneurysms with Cellulose Acetate Polymer”,
J. Neurosurg
., 77:497-500 (1992)
2
Kinugasa, et al., “Direct Thrombosis of Aneurysms with Cellulose Acetate Polymer”,
J. Neurosurg
., 77:501-507 (1992)
3
Casarett and Doull's
Toxicology
, Amdur et al., Editors, Pergamon Press, New York, pp. 661-664 (1975)
4
Greff, et al., U.S. patent application Ser. No. 08/507,863 for “Novel Compositions for Use in Embolizing Blood Vessels”, filed Jul. 27, 1995
5
Greff, et al., U.S. patent application Ser. No. 08/508,248 for “Cellulose Diacetate Compositions for Use in Embolizing Blood Vessels”, filed Jul. 27, 1995
6
Kinugasa, et al., “Early Treatment of Subarachnoid Hemorrhage After Preventing Rerupture of an Aneurysm”,
J. Neurosurg
., 83:34-41 (1995)
7
Kinugasa, et al., “Prophylactic Thrombosis to Prevent New Bleeding and to Delay Aneurysm Surgery”,
Neurosurg
., 36:661 (1995)
8
Taki, et al., “Selection and Combination of Various Endovascular Techniques in the Treatment of Giant Aneurysms”,
J. Neurosurg
., 77:3742 (1992)
9
Evans, et al., U.S. patent application Ser. No. 08/655,822 for “Novel Compositions for Use in Embolizing Blood Vessels”, filed May 31, 1996
10
Dunn, et al., U.S. Pat. No. 4,938,763 for “Biodegradable In-Situ Forming Implants and Methods of Producing Same”, issued Jul. 3, 1990
All of the above references are herein incorporated by reference in their entirety to the same extent as if each individual reference was specifically and individually indicated to be incorporated herein by reference in its entirety.
3. State of the Art
Embolization of blood vessels is conducted for a variety of purposes including the treatment of tumors, the treatment of lesions such as aneurysms, uncontrolled bleeding and the like.
Embolization of blood vessels is preferably accomplished via catheter techniques which permit the selective placement of the catheter at the vascular site to be embolized. In this regard, recent advancements in catheter technology as well as in angiography now permit neuroendovascular intervention including the treatment of otherwise inoperable lesions. Specifically, development of microcatheters and guide wires capable of providing access to vessels as small as 1 mm in diameter allows for the endovascular treatment of many lesions.
Embolic compositions heretofore disclosed in the art include those comprising a biocompatible polymer, a biocompatible solvent and a contrast agent which allowed visualization of the in vivo delivery of the composition via fluoroscopy.
1-8
Such compositions typically contain no more than about 8 weight percent of biocompatible polymer based on the weight of the total composition.
Endovascular treatment regimens preferably include the use of a water insoluble, radiopaque contrast agent in the embolic compositions in order that the physician can visualize delivery of the composition to the vascular site via conventional techniques such as fluoroscopy.
1-8
Additionally, the use of water insoluble contrast agents is beneficial during post treatment procedures to visualize the embolized mass during, for example, surgery or to monitor the disease condition and/or retreatment purposes.
Visualization is particularly necessary when using catheter delivery techniques in order to ensure both that the composition is being delivered to the intended vascular site and that the requisite amount of composition is delivered. The latter requirement is particularly critical in the treatment of aneurysms where only the aneurysm sac is intended to be filled while leaving the adjoining blood vessel unaffected.
Accordingly, in such treatments, the amount of embolic composition delivered is selected to substantially fill but not overflow the aneurysm sac. If less than this amount of embolic composition is delivered to the aneurysm sac, the patient will be left with an active aneurysm which, in some cases, may grow/enlarge over time. If more than this amount of embolic composition is delivered, the composition will overflow into the adjoining blood vessel which can then embolize this blood vessel as well as the aneurysm. In the case where the affected blood vessel is in or leads to a critical body organ, e.g., the brain, damage due to blood flow reduction or cessation can result in severe patient disability or death.
When delivered by catheter, the embolic compositions preferably comprise a biocompatible solvent, a biocompatible polymer and the water insoluble contrast agent. The biocompatible solvent is miscible or soluble in blood or other body fluid and also solubilizes the biocompatible polymer during delivery. The biocompatible polymer is selected to be soluble in the biocompatible solvent but insoluble in blood or other body fluid. The water insoluble contrast agent is suspended in the composition and, as above, permits the physician to fluoroscopically visualize catheter delivery of this composition. Upon contact with the blood or other body fluid, the biocompatible solvent dissipates from the embolic composition whereupon the biocompatible polymer precipitates in the presence of the water insoluble contrast agent and embolizes the blood vessel.
Notwithstanding the benefits associated with the use of such embolic compositions in treating aneurysms and other vascular disorders, in vivo these compositions formed coherent masses which often suffer from solidification and formation of a coherent mass distal from the point of ejection from the catheter. That is to say that upon ejection of the embolic composition in a vascular site, the coherent mass subsequently formed was often distal and not proximate the ejection port of the catheter. Moreover, upon solidification, the solid mass formed was often linear in shape (i.e., having a “string shape”).
In many circumstances, a contiguous or ball shape precipitate formed at the ejection port is desired (e.g., to fill an aneurysm sac). Distal solidification of a string shape precipitate makes site specific delivery of the solid mass in the vasculature difficult. As is apparent, site specific delivery of the solid mass is essential for treatment of vascular disorders such as aneurysms. Solidification at points distal to the ejection port, as is common in string shape precipitates, can result in the solid mass forming not in the aneurysm sac but in the artery attendant the aneurysm. Such a string shape precipitate is more prone to fragmentation which can lead to embolization of this artery and possible incapacitation or death of the patient. Moreover, such fragmentation can lead to particles or fragments being “washed” downstream and lodging at undesired locations in the vasculature.
To address this problem, U.S. patent application Ser. No. 09/574,379, concurrently filed herewith and entitled “Novel High Viscosity Embolizing Compositions” discloses that the use of high viscosity embolic compositions comprising a biocompatible polymer, a biocompatible solvent and a contrast agent permits site specific delivery of these compositions to the vascular site. The contents of this application are incorporated herein by reference in its entirety.
A problem has arisen with the use of such high viscosity compositions. Specifically, the high viscosity of the biocompatible polymer/biocompatible solvent mixture makes it difficult to form a uniform suspension when co

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