VASCULAR OCCLUSION DEVICE

Abstract: The present invention relates to an occlusion device (10) for treating an aneurysm (11), its use and a method for treating an aneurysm (11). The occlusion device (10) comprises a detachable filling element (12) and at least one radioactive source (14). The detachable filling element (12) and the radioactive source (14) are adapted to be inserted into a vessel (13) at least in close proximity of a neck (15) of an aneurysm (11). The radioactive source (14) prevents recanalisation for permanently obstructing the neck (15) of the aneurysm (11).

Description: VASCULAR OCCLUSION DEVICE BACKGROUND OF THE INVENTION (a) Field of the Invention The invention relates to an artificial occlusion device designed for the endovascular treatment of aneurysms, such as lntracramal, or for closing any body lumen, such as vascular lumen or other. The invention also relates to the use of the occlusion device and a method for treating an aneurysm. (b) Description of Prior Art Direct surgical clipping has been used for the treatment of most mtracranial aneurysms. However, surgical difficulties and related morbidity with certain aneurysms have stimulated the development of endovascular procedures. Despite the favorable results of endovascular platinum coil treatment m acutely ruptured aneurysms, neck remnants and recurrences are frequent and may compromise the long-term success of this treatment modality (Jean Raymond et al . , Neurosurgery, 41:6, 1977). This mechanical failure of the device of the prior art is not surprising and coils alone without efficient healing mechanisms may not be strong enough to counteract the continuous repetitive force of the abnormal flow which often remains following incomplete endovascular treatment, or which follows recanalisation after coil embolization. The mechanism of surgical clipping directly opposes the vessel wall, leading to rapid "primary healing" . By opposition, following endovascular treatment, the wound margins are separated by coils and healing depends on fibrous replacement of clot between coils and growth of a neomtima at the coil - parent vessel interface. There is a general pattern of wound healing m the vessel wall, which occurs following a wide variety of traumatic or pathological conditions. These mechanisms are also involved in repairing experimental aneurysms. In vivo studies suggest that healing of experimental aneurysms involves coagulation, inflammation, cellular migration, proliferation, matrix secretion with the formation of a neointima at the neck of treated aneurysms. Conversely, aneurysms treated by coil embolization are subjected to a recanalization process that involves the formation of endothelialized slit-like spaces between coils or between coils and the aneurismal wall. The proposed invention is designed to inhibit aneurismal recanalisation in order to improve long-term results of endovascular treatment. Intracranial aneurysms can be treated by four different principles: 1) Surgical clipping permits closure of the aneurysmal neck from the outside, with close apposition of the edges of the "wound" and satisfactory healing, but necessitates craniotomy and dissection at the base of the brain. 2) Parent vessel occlusion consisting of occlusion of the vessel along with the aneurysm or with the intent to decrease blood flow to the aneurysm, is possible only in certain anatomical sites, and in the presence of an adequate collateral circulation. 3) Parent vessel stenting is a new possibility but is currently technically feasible only in proximal vessels or in extracranial aneurysms such as the aorta (WO 98/12990 and WO 93/08767) . 4) Selective endosaccular occlusion of the aneurysm is currently the most frequently used method of endovascular treatment. This method can be performed with three (3) different types of material: a) Liquid or fluid agents which polymerize inside the aneurysm or immediately before exiting the catheter; this strategy has never been routinely used because of the fear of cerebral embolization; b) Detachable balloons have been introduced by Serbmenko, Romodanov and Scheghlov and have more frequently been used between 1978 and 1990. The expertise necessary for using these devices was difficult to master; these devices led to a high incidence of inadvertent aneurysm rupture and were also plagued with a high incidence of recurrences; and c) Microcoils; these metallic devices became popular with the Guglielmi Detachable Coil system, which permitted to reposition the coil and detach it only when it was felt to be m a satisfactory position. The availability of this system has greatly increased the use of the endovascular route m the treatment of mtracramal aneurysms . The device is much safer to use than detachable balloons, free coils, or polymeric embolic agents. The mam advantage of soft coils compared to detachable balloons is the fact that they will conform to the shape of the aneurysm. However, even m aneurysms that can be sufficiently occluded m order to prevent rebleedmg of the aneurysm during the acute phase, recurrences after a few months are frequent and this fear of recurrences is currently the major drawback of the technique and the most important argument against a more widespread clinical application. International application publication WO 99/61107 entitled "Radioactive intraluminal endovascular prosthesis and method for the treatment of aneurysms" discloses a method for "promoting the rate of thrombus formation and proliferative cell growth" . The method is dedicated to the use of stents m fusiform aneurysms, or stent-grafts in abdominal aortic aneurysms . It would be highly desirable to be provided with a device for treating aneurysms, which could prevent recanalisation at the neck of treated aneurysms for improving long-term results of endovascular treatment. It would also be highly desirable to be provided with a method for treating aneurysms, which could prevent recanalisation and increase neointima formation at the neck of treated aneurysms for improving long-term results of endovascular treatment. SUMMARY OF THE INVENTION One aim of the present invention is to provide a device for treating aneurysms, which could inhibit aneurismal recanalisation for improving long-term results of endovascular treatment. Another aim of the present invention is to provide a method for treating aneurysms, which could inhibit recanalisation and increase neointima formation at the neck of treated aneurysms for improving long-term results of endovascular treatment. In accordance with the present invention there is provided a device for treating aneurysms, which inhibit recanalisation for improving long-term results of endovascular treatment . In accordance with the present invention there is provided a method for treating aneurysms, which could inhibit recanalisation at the neck of treated aneurysms by emission of radiation. Still in accordance with the present invention there is provided an occlusion device for treating an aneurysm, comprising a detachable filling element and at least one radioactive source, said detachable filling element and said radioactive source being adapted to be inserted into a vessel at least m close proximity of a neck of an aneurysm, said radioactive source preventing aneurismal recanalisation. The detachable filling element may be a coil, preferably a platinum coil . The radioisotope source is preferably a β- emittmg source. The radioisotope source may be made of a polymer and a radioisotope. The β-emittmg source is preferably at least one β-emittmg source from Antιmony-124 , Cesιum-134, Cesιum-137, Calcιum-45, Calcιum-47, Cerium 141, Chloπne-36, Cobalt-60, Europιum-152, Gold-198, Hafnιum-181, Iodme-131, Iπdιum-192, Iron-59, Lutetιum-177 , Mercury-203, Neodymιum-147 , Nιckel-63, Phosphorus - 32 , Phosphorus -33 , Rhenιum-186, Rubιdιum-86, Ruthenium- 106 , Samaπum-153 , Scandιum-46, Silver-llOm, Strontιum-89 , Strontιum-90 , Sulfur-35, Technetιum-99, Terbιum-160, Thulιum-170, and Yttrium- 90. In accordance with another aspect of the invention, the occlusion device may further comprise a second filling element selected from the group consisting of a coil, a polymer, a bioactive peptide, an aqueous solution, and a gel. The aqueous solution is preferably a solution capable of polymerization once m the aneurysm. Further in accordance with the present invention, there is provided the use of an occlusion device as defined above for the treatment of an aneurysm. Also m accordance with the present invention, there is provided a kit for the treatment of an aneurysm. The kit comprises: a detachable filling element adapted to be inserted into a vessel at least m close proximity with a neck of an aneurysm; and a radioactive source adapted to be inserted with the detachable filling element; wherein the radioactive source prevents recanalisation causing permanent obstruction of the neck of the aneurysm. Further in accordance with the present invention, there is provided a method for treating an aneurysm comprising inserting a detachable filling element and a radioactive source into a vessel at least m close proximity of a neck of an aneurysm, the radioactive source preventing recanalisation and causing permanent obstruction of the neck of the aneurysm. The present invention thus primarily addresses mtracranial saccular aneurysms. A preferred embodiment of the present invention is a radioactive coil designed to inhibit recanalization following coil embolization. The method of the present invention is not designed to increase endothelialization as in WO99/61107, but to decrease endothelialization of the thrombus to prevent the formation of slit-like spaces responsible for recanalization after coil embolization; The method is not designed to increase proliferative cell growth. The thicker neointima noted after radioactive coil embolization is an "artefact", secondary to fibrosis of the clot which has not recanalized or which could not recanalize because of radiation. BRIEF DESCRIPTION OF THE DRAWINGS Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and wherein: Fig. 1 is a partial schematic representation of a microcatheter provided with a radioactive coil in accordance with one embodiment of the invention; Fig. 2 is an enlarged cross-sectional view taken along lines 2-2 of Fig. 1; Fig. 3 is partial schematic cross-sectional view of an artery having an aneurysm filled with the radioactive coil of Fig. 1; Fig. 4 is a schematic view of another embodiment of the invention; Figs. 5A and 5B illustrate a schematic view of further embodiments of the invention; and Fig. 6 illustrates a histogram showing the effect of radioactivity on recanalisation. DETAILED DESCRIPTION OF THE INVENTION In accordance with one embodiment of the present invention there is provided a device for treating aneurysm, which would inhibit aneurismal recanalisation by adding a radioactive source to the embolic agent. Although β-particle emitting stents have been designed to inhibit neointima formation, 1 μCi and lower dose stents are shown to cause the reverse effect i.e. they were associated with a more severe neointimal response than control stents. Neointima formation may be promoted with low dose radiation by fibrin-thrombus deposition, overexpression of tissue factor, inflammation and growth factor secretion by inflammatory cells, by stimulation of extracellular matrix by neointimal cells or by any other unknown mechanisms. However, the present invention relates to the fact that radiation inhibits recanalisation of thrombus after coil embolisation, and increased neointima is only secondary to fibrous replacement of increased residual clot, not subjected to the recanalisation process. Thus a radioactive source that is delivered at low dose prevents recanalisation at the neck of the aneurysms. This effect would then decrease the incidence of recurrence. As seen in Figs. 1 to 3 , in accordance with one embodiment of the present invention, there is provided an artificial occlusion device 10 designed for endovascular treatment of an aneurysm 11, and preferably of an intracranial aneurysm. However, the artificial occlusion device 10 is not restricted to this use as it could also be used to close any body lumen, such as vascular lumen or others. The artificial occlusion device 10 comprises a detachable filling coil 12, onto which a β-emitting radioactive source 14, such as 32 P, is coated. In this embodiment, the embolic agent is a detachable coil, preferably a platinum coil, and the radioactive source is 32 P, a β-emitting isotope of phosphorus. In one embodiment of the invention, 2 P ions are directly coated onto the metallic coil, using ion implantation. A beam of 32 P ions is accelerated to hundreds of Kev and directed along a beam line to the coil surface. Direct implantation of 32 P to reach a total activity above 0.13 μCi/cm of coil has been shown to be effective in experimental animals. Penetration of 32 P ions is only a few tenths of a micron, so that the trace amounts are not expected to alter significantly the properties of the coil. Other γ or β emitters such as rhenium, strontium, or any other radioactive source can be used for the same purpose. The radioactive source can be part of a large molecule, or can be added to a polymer or a chemical substance used to coat the surface or to fill the center of coils . The radioactive source can be delivered through a polymer or any filling substance that could be used as an embolic agent, either alone or m combination In use the filling coil 12 and the β-emitting radioactive source 14 are delivered with a microcatheter 16. For filling the aneurysm 11 with the artificial occlusion device 10, the same procedure is done as is presently being done for filling any aneurysm. The difference being that currently, aneurysms are being filled with a filling coil alone, whereas m accordance with the present invention, aneurysm treated with the present invention would be filled with a filling coil coated or ion implanted with a β-emittmg radioactive source, realizing m fact a local mtra-aneurysmal radiotherapy. Briefly, the microcatheter 16 is brought to the aneurysm 11 to be treated from within a blood vessel 13. At the site of the aneurysm 11, the filling coil 12 carrying (such as coated or ion implanted with) a β- emittmg radioactive source 14 is pushed m the aneurysm 11. Sufficient filling coil 12 is inserted m the aneurysm 11 for filling and packing it. The β- emittmg radioactive source 14 on the filling coil 12 prevents recanalisation, which will cause permanent closure of the neck 15 of the aneurysm 11 therefore repairing the blood vessel . In another embodiment of the present invention, the β-emittmg radioactive source 14 is coated onto the surface of a detachable balloon 18, as illustrated m Fig. 4 for treating aneurysms. The detachable balloon is mounted on a delivery wire 20 or catheter slidably fitted into the microcatheter 16. Accordingly, when the pushing wire 20 is retracted into the microcatheter 16, the balloon 18 coated with the β-emittmg radioactive source 14 is detached from the pushing wire 20, and left into the aneurysm. In a further embodiment of the present invention as illustrated in Fig. 5A, there is provided a stent 22 coated with the β-emitting radioactive source 14. The stent is inserted within the blood vessel as is being done in the art. The radioactive source on the stent prevents recanalisation of the clot formed at the stent -aneurysm interface. After a period of time, the stent will be embedded in a new neointima formation, which will therefore obstruct the neck of the aneurysm, causing same to close. A variant of this latter embodiment is illustrated in Fig. 5B. In Fig. 5B, a support 24 coated with a radioactive source 14 is mounted at each ends thereof on an self -expandable loop 26, each adapted to fractionally engage with the inner surface of a blood vessel for maintaining the support 24 in place with the blood vessel. Accordingly, the variant is installed similarly as a stent is installed, positioning however the support 24 coated with a radioactive source 14 against the neck of an aneurysm for obstructing it. As mentioned previously, after a given time, the support 24 will be covered by a neointima formation, which will cause closing of the neck of the aneurysm. The present invention will be more readily understood by referring to the following example, which is given to illustrate the invention rather than to limit its scope. EXAMPLE I Low-Dose Beta- Irradiation Prevents Recanalization After Coil Embolization The mechanisms involved in recurrences after coil embolisation of human aneurysms have not yet been determined. Aneurismal recurrences after endovascular treatment can be reproduced in selected animal models (Raymond, J. Neuroradiol . ) . Coil embolisation of surgically constructed bifurcation aneurysms in dogs is consistently followed by early recurrences that can be seen by angiography at 3 months. To investigate mechanisms involved in this phenomenon, a model of single coil embolisation of canine vertebral and maxillary arteries has been used. Coil embolization is routinely followed by arterial occlusion one hour after treatment . Arterial occlusions persist for many days but serial angiographic studies reveal recanalisation of occluded arteries at 1 week, a phenomenon that is completed by 2 weeks and persists at 3 months in almost all cases. Recanalized arteries previously embolized with platinum coils and recurrent bifurcation aneurysms also treated with coils in the same animals share similar features on macroscopic inspection at 3 months. While coils may be embedded in a thin or a well- developed neointima, there are open channels between them or between the coils and the vascular wall . Histological studies performed at various times after embolization show invasion of the clot by alpha-actin positive mesenchymal cells, as well as the formation of endothelialized channels that restore circulation in the occluded vessel . It was found that the outcome of embolization would depend on the balance between 2 phenomena that the inventors artificially separated: the recanalization process, which involves endothelial cells that attempt to restore a non-thrombogenic surface and a patient lumen; and the restenotic process, with smooth muscle cells or myofibroblasts invading the provisional fibrin matrix to secrete collagen and form fibrous tissue. These processes probably collaborate in assuring or restoring arterial patency following arterial trauma or occlusions. While the recanalization process may be essential to restore circulation to ischemic tissues, it may also recanalize the clot between the coils at the neck of aneurysms . According to this, the inventors found that if they could delay endothelial invasion and recanalization of the clot, the balance would fall in favor of fibrous tissue formation and permanent occlusion of artery or aneurysms . Arterial reactions to coils implanted with a low dose of the isotope 32 P have been studied. Standard platinum coils of the IDC type (immediately detachable coils, Target Therapeutics, n=8) measuring 3mm in caliber and 10 cm in length were implanted with 0.14 μCi/cm of 32 P using an ion implantor dedicated to radioactive beams. This method allows to embed 32 P ions onto coils, at a few nanometers from the coil surface without causing any mechanical alteration of the device. The coil becomes a sealed source of beta radiation with a low penetration (70% of the dose is lost in the first millimeter) . In 8 animals, 32 P-coils were used to embolize one maxillar artery, while the controlateral maxillary artery was treated with an identical but non-radioactive coil. The recanalisation process was completely inhibited with 32 P and arteries remained obliterated for 2(n=2), 3(n=2), 4(n=4) and 12 weeks (n=6) while arteries treated with non-radioactive coils were recanalized and patent at all dates. Gross morphological and pathological studies showed that the lumen of arteries embolized with radioactive coils was fully replaced with fibrous tissue at 3 months. To eliminate any potential effect of the implantation process on results, 3 coils were submitted to implantation but without 32 P and inserted into one maxillary artery, while the controlateral maxillary of each dog was embolized with an intact coil in 3 animals. All 6 arteries became occluded at 1 week but were recanalized at 2 , 3 and 12 weeks. To define the level of activity that has to be implanted to prevent the recanalization process the experiment was repeated m 8 animals followed for 3 months using 3 different doses of 32 P in 4 arteries while the operator was blinded to the activity of each coil. The results of these experiments are summarized m Fig. 6. An activity of 0,13 μCi/cm of coil is sufficient to prevent recanalization m 100% of arteries. Fig. 6 shows recanalization of canine arteries and inhibition with β-irradiation. Patency rates of canine maxillary or vertebral arteries embolized with 3 mm x 10 cm platimum coils carrying 0 to 5.5 μCi of 32 P were determined. All coils caused thrombosis at one week, followed by recanalization at two weeks. The recanalization process is partially inhibited with coils carrying activities between 0.8 and 1.29 μCi, and completely inhibited with activities above 1.3 μCi . It was then tested if this strategy would prevent recurrences after endovascular treatment of experimental bifurcation aneurysms, a model that had shown constant recanalization m previous experiments. In 7 animals, aneurysms measuring approximately 8mm were embolized with 2 radioactive coils 5mm m diameter and 15 cm m length implanted with a mean of 2.2 μCi of 32 P. The core of this radioactive platinum sphere was then packed with non-radioactive coils to achieve near complete obliteration of aneurysms. Results of this experiment were compared with similar aneurysms embolized m a similar fashion with non-radioactive platinum coils. Angiographic results at 3 and 12 weeks, scored according to a previously described classification (Raymond), are shown m Table 1. When 32 P-coιls are used m the bifurcation aneurysm model, angiographic results remain stable, with no recurrence, while aneurysms embolized with non-radioactive coils recur constantly. Differences in angiographic scores between the 2 groups were significant. Gross morphological studies at 12 weeks showed that the neck of aneurysms embolized with 32 P coils is sealed by a well -developed fibrous neointima. Conversely, the cold coils at the neck of control aneurysms were covered by a thin and incomplete neointima with open crevices between the coils leading to large open spaces. Table 1 Radioactive coils vs. control coils and aneurismal recurrences: comparison of angiographic scores Angiographic results 3 months after endovascular treatment of 13 canine bifurcation aneurysms, 6 embolized with standard platinum coils, 6 with radioactive coils (total activity > 4 μCi / aneurysm). Angiographic scores increase with time (aneurysms recur) with standard coils while aneurysms treated with radioactive coils have a stable angiographic score. 1 Angiographic score at 3 months » initial score (p = 0.0009) 2 Angiographic score at 3 months not significantly different from initial score (p = 0.60) Vascular healing phenomena may vary from one species to another. It was then accessed whether the recanalization process witnessed above and its inhibition by beta-irradiation were specific to canine arteries. The experiment involving arterial occlusion with platinum coils was repeated in porcine lingual and maxillary arteries and in rabbit subclavian arteries, 2 species often used in the evaluation of pathological reactions to endovascular interventions. The same recanalization process was encountered in rabbits and a similar activity of was sufficient to inhibit recanalization. Conversely, porcine arteries did not recanalize with the same frequency as dogs and rabbits at 3 weeks, when the coils were cold (75% as compared to 100%) . The addition of the same activity of 32 P found effective in other species prevented recanalization in all arteries. This experiment explains why aneurismal recurrences can be reproduced in animal models that use dogs or rabbits but are infrequent in experimental porcine aneurysms . The effects of 32 P on the recanalization process after coil embolization are reproducible and this discovery may have a strong impact on endovascular treatment of aneurysms. A mechanism, which can prevent recanalization in si tu, without systemic effects, and without changing the initial thrombogenicity of the embolic agent, as the present invention, may improve long-term results without increasing iatrogenic complications of the endovascular procedure. While the invention has been described with particular reference to the illustrated embodiment, it will be understood that numerous modifications thereto will appear to those skilled in the art. Accordingly, the above description and accompanying drawings should be taken as illustrative of the invention and not in a limiting sense.

Claims: What is claimed is: 1. An occlusion device for treating an aneurysm, comprising a detachable filling element and at least one radioactive source, said detachable filling element and said radioactive source being adapted to be inserted into a vessel at least in close proximity of a neck of an aneurysm, said radioactive source preventing recanalisation for permanently obstructing the neck of the aneurysm or filling up the aneurysm. 2. The occlusion device of claim 1, wherein the detachable filling element is a coil. 3. The occlusion device of claim 2, wherein said coil is a platinum coil . 4. The occlusion device of claim 1, 2 or 3 , wherein the radioisotope source is a β-emitting source. 5. The occlusion device of claim 1, 2, 3 or 4, wherein the radioisotope source comprises a polymer and a radioisotope. 6. The occlusion device of claim 4, wherein the β- emitting source is at least one β-emitting source from Antimony-124 , Cesium-134, Cesium-137, Calcium-45, Calcium-47, Cerium 141, Chlorine-36, Cobalt-60, Europium-152, Gold-198, Hafnium- 181, Iodine-131, Iridium-192, Iron-59, Lutetium-177 , Mercury-203, Neodymium-147 , Nickel -63, Phosphorus- 32 , Phosphorus-33 , Rhenium-186, Rubidium-86, Ruthenium- 106 , Samarium-153 , Scandium-46, Silver-llOm, Strontium-89 , Strontium-90 , Sulfur-35, Technetium-99, Terbium-160, Thulium-170, and Yttrium-90. 7. The occlusion device of claim 1, 2, 3, 4, 5 or 6, further comprising a second filling element selected from the group consisting of a coil, a polymer, a bioactive peptide, an aqueous solution, and a gel. 8. The occlusion device of claim 7, wherein the aqueous solution is a polymerizable solution capable of polymerization once m the aneurysm. 9. Use of an occlusion device as defined m claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 for the treatment of an aneurysm. 10. A kit for the treatment of an aneurysm, said kit comprising : a) a detachable filling element adapted to be inserted into a vessel at least m close proximity with a neck of an aneurysm; and b) a radioactive source adapted to be inserted with the detachable filling element; wherein said radioactive source prevents recanalisation causing permanent obstruction of the neck of the aneurysm. 11. A method for treating an aneurysm comprising inserting a detachable filling element and a radioactive source into a vessel at least m close proximity of a neck of an aneurysm, said radioactive source preventing recanalisation causing permanent obstruction of the neck of the aneurysm.

Inventors: LECLERC GUY, RAYMOND JEAN, LECLERC, GUY, RAYMOND, JEAN
Applicants: ANGIOGENE INC, LECLERC GUY, RAYMOND JEAN, ANGIOGENE INC., LECLERC, GUY, RAYMOND, JEAN
Application year: 2001
Main classification: A61B17
IPC codes: A61B17, A61N5