Implantable intraluminal device and method of using same in treating aneurysms

[0001] The present invention is related to Provisional Application No. 60/332,013 filed 23 Nov. 2001, the contents of which are incorporated herein by reference, and claims the priority date of that application.

[0002] The present invention relates to intraluminal devices implantable in a blood vessel for the treatment of aneurysms especially brain aneurysms. The invention also relates to methods of treating aneurysms using such intraluminal devices.

[0003] A number of publications as listed at the end of this specification are incorporated herein by reference in their entireties for background information and are numerically referenced in the following text:

[0004] Intracranial aneurysms are the main cause of nontraumatic subarachnoid hemorrhage and are responsible for about 25% of all deaths relating to cerebrovascular events. Autopsy studies show that the overall frequency of intracranial aneurysms in the general population is approximately 5 percent and suggest that 10 to 15 million persons in the United States have or will have intracranial aneurysms 1. In approximately 15,000 cases (6 cases per 100,000 persons per year), intracranial aneurysms rupture every year in North America 2. Rupture of intracranial aneurysms leads to subarachnoid aneurysmal hemorrhage (SAH) which has a 30-day mortality rate of 45%, and results in approximately half the survivors sustaining irreversible brain damage 1, 2.

[0005] The primary goal of treatments for intracranial aneurysm is prevention of the rupture of the aneurysms, thereby preventing bleeding or rebleeding. At the present time, three general methods of treatment exist. These can be grouped according to their approach: extravascular, endovascular, and extra-endovascular.

[0006] The extravascular approach involves surgery or microsurgery of the aneurysm. One surgical procedure is to apply a metallic clip or a suture-ligation across the artery feeding the aneurysm (neck), thereby allowing the aneurysm to clot off and hopefully shrink. Another surgical procedure is to surgically reconstruct the aneurysmal portion of the artery, by surgically cut out the aneurysm and repairing the vessel by using a natural or synthetic vessel graft. Both of these surgical procedures typically require general anesthesia, craniotomy, brain retraction, and dissection of the arachnoid around the neck of the aneurysm.

[0007] Surgical treatment of vascular intracranial aneurysm is accompanied by a mortality rate of 3.8% and a morbidity rate of 10.9% 3. Because of the high mortality and morbidity rates, and because the condition of many patients does not permit them to undergo an open operation, the surgical procedure is often delayed or not practical. For this reason the prior art has sought alternative means of treatment.

[0008] The development of microcatheters made possible the use of endovascular (catheter-based) procedures. The major advantage of the endovascular procedures is that they do not require the use of open surgery. They are generally more beneficial and have much lower mortality and morbidity rates than the extravascular procedures.

[0009] Many variations of endovascular procedures exist of which some of the more important are the following:

[0010] 1. Placement of embolic material, such as metallic microcoils or spherical beads, inside the aneurysm sac in order to form a mass within this sac which will slow the blood flow and generally encourage the aneurysm to clot off and to shrink. To accomplish this procedure, a microcatheter is guided through the cerebral arteries until the site of the aneurysm is reached. The distal tip of the microcatheter is than placed within the sac of the aneurysm, and the embolic material is injected into the sac of the aneurysm. Typical microcatheters suitable for this procedure are disclosed in U.S. Pat. Nos. 5,853,418; 6,066,133; 6,165,198 and 6,168,592.

[0011] Widespread, long-term experience with this technique has shown several risks and limitations. The method has 4% morbidity and 1% mortality rate and achieves complete aneurysm occlusion in only 52% to 78% of the cases in which it is employed. The relatively low success rate is due to technical limitations (e.g., coil flexibility, shape, and dimensions) which prevent tight packing of the sac of the aneurysm, especially aneurysms with wide necks 3. Other difficulties are associated with the presence of preexisting thrombus within the aneurysm cavity, which may be sheared off into the parent trunk leading to parent artery occlusion. Also aneurysm perforation may occur during placement of coils into the aneurysm. Additionally, occurrence of coil movement and compaction may foster aneurysm revascularization or growth.

[0012] 2. Another endovascular technique for treating aneurysms involves inserting a detachable balloon into the sac of the aneurysm using a microcatheter. The detachable balloon is then inflated using embolic material, such as a liquid polymer material or microcoils. The balloon is then detached from the microcatheter and left within the sac of the aneurysm in an attempt to fill the sac and to form a thrombotic mass inside the aneurysm.

[0013] One of the disadvantages of this method is that detachable balloons, when inflated, typically do not conform to the interior configuration of the aneurysm sac. Instead, the aneurysm sac is forced to conform to the exterior surface of the detachable balloon. Thus, there is an increased risk that the detachable balloon will rupture the sac of the aneurysm.

[0014] 3. Stent technology has been applied to the intracranial vasculature. The use of this technology has been limited until recently by the lack of available stents and stent delivery systems capable of safe and effective navigation through the intercranial vessels. The use of such stents is particularly difficult with respect to aneurysms in head blood vessels because of the number of perforating vessels in such blood vessels, and thereby the increased danger that one or more perforating vessels may be in the vicinity of such an aneurysm. The same is true with respect to bifurcations of a blood vessel splitting into one or more branch vessels, which may also be in the vicinity of an aneurysm. Where the blood supply to an aneurysm is to be reduced, it is critical that the blood supply to such perforating vessel or branch vessels, in the vicinity of the aneurysm not be unduly reduced to the degree causing damage to the tissues supplied with blood by such perforating or branch vessels.

[0015] Thus, there is a serious danger that the placement of a conventional endovascular stent within the parent artery across the aneurysm neck to reduce blood flow to the aneurysm, to promote intra-aneurysm stasis and thrombosis 4,5.

[0016] Stents having portions of different permeabilities are disclosed, for example, in McCrory U.S. Pat. No. 5,951,599, Brown et al U.S. Pat. No. 6,093,199, Wallsten U.S. Pat. No. 4,954,126, and Dubrul U.S. Pat. No. 6,258,115.

[0017] The McCrory patent discloses a braided stent having a first portion with a relatively high porosity index so as to be highly permeable to blood flow, and a second portion of lower porosity index so as to be less permeable to blood flow. When the stent is deployed, the portion of low permeability is located to overlie the neck of the aneurysm, and the portion of high permeability is spaced from the neck of the aneurysm. A braided stent construction with different porosities is also disclosed in the Dubrul patent.

[0018] Brown et al, on the other hand, discloses an intraluminal device or stent comprising a diverter, in the form of a low-permeability foam pad, to overlie the neck of the aneurysm, straddled on its opposite sides by a pair of high-permeability coil elements for anchoring the device in the blood vessel.

[0019] Wallsten U.S. Pat. No. 4,954,126, discloses a braided tube intraluminal device for use in various applications, one of which applications is to apply a graft to treat an aneurysm (FIG. 9). In this case, the complete braided tube would have high permeability with respect to blood flow therethrough since its function is to mount the grafts, but the graft would have low-permeability to decrease the possibility of rupture of the aneurysm.

[0020] Delivery devices for stents for use in the intracranial vasculature are well known at the art. Typical devices are disclosed, for example, in the following U.S. Pat. Nos. 5,496,275; 5,676,659; and 6,254,628. The blood vessels in the brain are frequently as small as several millimeters, requiring that the catheters have an outside diameter as small as 2-8 French (0.66 mm to 2.64 mm).

[0021] Technically it is very difficult to produce and accurately deploy the stents described in the above McCrory, Brown et al and Wallsten patents for treating aneurysms by using presently available delivery systems. The difficulties include not only in producing such stents of different permeabilities, but also in deploying them such that the portion of low permeability is exactly aligned with the aneurysm neck. When the device is to be implanted in a blood vessel having an aneurysm at or proximate to a perforating vessel or a bifurcation leading to a branch vessel, the portion of high permeability must be precisely located at the perforating or branch vessels in order to maintain patency in the perforating or branch vessels. Additionally, particularly in tortuous, ectatic vessels, existing stiff stents are difficult to introduce and may results in kinking such as to cause the failure of the deployment process.

[0022] For these reasons it is apparent that there is a need for a better intraluminal device to treat an aneurysm, particularly an intracranial aneurysm.

[0023] An object of the present invention is to provide an intraluminal device having advantages in one or more of the above respects for implantation in a blood vessel having an aneurysm in order to treat the aneurysm. Another object of the invention is to provide such an intraluminal device particularly useful for implantation in a blood vessel having an aneurysms at or proximate to one or more perforating vessels and/or a bifurcation leading to a branch vessel such as to reduce the blood flow to the aneurysms while still maintaining patency in the perforating and/or branch vessels.

[0024] Another object of the invention is to provide an implantable intraluminal device for treating aneurysms in the intracranial vasculature that is sufficiently flexible and pliable so that it can be delivered easily to an intracranial site, deployed accurately, and then left in position to accomplish its purpose.

[0025] A further object of the invention is to provide a method of treating aneurysms by using intraluminal devices having the above features.

[0026] According to the present invention, there is provided an intraluminal device implantable in a blood vessel having an aneurysm therein in the vicinity of a perforating vessel, and/or of a bifurcation leading to a branch vessel, the device comprising: a mesh-like tube of bio-compatible material having an expanded condition in which the tube diameter is slightly larger than the diameter of the blood vessel in which it is to be implanted, and the tube length is sufficient to straddle the aneurysm and to be anchored to the blood vessel on the opposite sides of the aneurysm; the mesh-like tube also having a contracted condition wherein it is sufficiently flexible so as to be easily manipulatable through the blood vessel to straddle the aneurysm; the mesh-like tube, in its expanded condition, having a porosity index of 55%-80% such as to reduce the flow of blood through a wall of the mesh-like tube to the aneurysm sufficiently to decrease the possibility of rupture of the aneurysm but not to unduly reduce the blood flow to a perforating or branch vessel to the degree likely to cause significant damage to tissues supplied with blood by such perforating or branch vessel.

[0027] Experimental evidence indicates that patency can be maintained and ischemia and infarction can be prevented if less than 50% of the ostial diameter is occluded 6.

[0028] In the described preferred embodiments, the windows in the mesh-like tube produce a porosity index of 50%-85%, preferably 60%-75%. The porosity index (P.E.) is defined by the relation: $P.E.=1-\frac{\mathrm{Sm}}{\mathrm{St}}$

[0029] wherein: Sm is the actual surface covered by the mesh-like tube, and St is the total surface area of the mesh-like tube. The porosity index of the existing typical stents is well above 80%. In the tube devices of the present invention, however, the porosity index is not more than 85%, preferably 55-80%, more preferably 60-75%.

[0030] In the described preferred embodiments, the mesh-like tube includes windows having an inscribed diameter of 30-480 m, preferably 50-320 m, in the expanded condition of the mesh-like tube.

[0031] According to the described preferred embodiments, the mesh-like tube includes a plurality of filaments of bio-compatible material extending helically in an interlaced manner in opposite directions so as to form a braided tube. It is contemplated, however, that other mesh-like structures could be used, such as woven or knitted tubes.

[0032] A maximum porosity index is attained when the braiding angle, in the expanded condition of the braided tube, is 90. However, decreasing the braiding angle below 90 increases the radial force applied by the braided tube against the inner surface of the blood vessel and decreases the P.E. In cases, where low radial force is needed, the desirable low P.E. can be achieved by increasing or decreasing the braiding angle, as described below with respect to specific examples. Preferably, the braided tube has a braiding angle in the range of 20%-150% in the expanded condition of the braided tube.

[0033] Also in the described preferred embodiments, the filaments, or at least most of them, are of circular cross-section and have a diameter of 10-60 m, preferably 20-40 m. The filaments could also be of non-circular cross-section, such as of square or rectangular cross-section, in which case it is preferred that they have a circumference of 40-180 m. It is also possible to use combination of several filament diameters and filament materials in one device to achieve structural stability and/or desired radio-opacity characteristic. Preferably the braid is formed of 24-144 filaments, more preferably 62-120 filaments. The filaments may be of a suitable bio-compatible material, metal or plastic, and may include a drug or other biological coating or cladding.

[0034] According to another aspect of the present invention, there is provided a method of treating an aneurysm in a blood vessel, which may be proximate to one or more perforating vessels and/or to a bifurcation leading to a branch vessel, by using intraluminal devices having the above combination of features.

[0035] As will be described more particularly below, intraluminal devices constructed in accordance with the foregoing features show great promise in the treatment of aneurysms in general, and brain aneurysms in particular, since they are relatively easily manipulatable through the blood vessel to the implantation site, and when deployed in their expanded condition in the implantation site, they reduce the flow of blood to the aneurysm sufficiently to decrease the possibility of rupture thereof, while maintaining patency in any perforating or branch vessels in the vicinity of the aneurysm.

[0036] Further features and advantages of the invention will be apparent from the description below.

[0037] The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

[0038] FIGS. 1a and 1b are side and end view, respectively, illustrating one form of intraluminal device constructed in accordance with the present invention, the device being shown in its normal, expanded condition;

[0039] FIGS. 2a and 2b are corresponding views but illustrating the device in its contracted, stressed condition;

[0040] FIG. 3 more particularly illustrates the braid pattern of FIGS. 1a, 1b and 2a, 2b in the expanded condition of the braided tube;

[0041] FIG. 4 illustrates another braid pattern, wherein one filament extending in one helical direction is interwoven over and under two filaments extending in the opposite helical direction;

[0042] FIG. 5 illustrates a further braid pattern in which two (or more) filaments extending helically in one direction are interwoven over and under two (or more) filaments extending in the opposite direction;

[0043] FIG. 6 schematically shows the relationship between the bending rigidity of the braided tube with respect to the diameter of the filaments producing the braided tube;

[0044] FIG. 7 schematically illustrates an intraluminal device implanted in a blood vessel having a plurality of perforating vessels in the vicinity of an aneurysm; and

[0045] FIGS. 8, 9, and 10 illustrate various manners in which an intraluminal device constructed in accordance with the present invention may be implanted in a blood vessel having an aneurysm at or proximate to a bifurcation leading to one or more branch vessels.

[0046] It is to be understood that the drawings and the description below are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and various possible embodiments thereof, including what is presently considered to be preferred embodiments. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein.

[0047] FIGS. 1a and 1b illustrate an intraluminal device, therein generally designated 2, constructed in accordance with the present invention in its normal or expanded condition which it assumes in a blood vessel after deployment therein; whereas FIGS. 2a and 2b illustrate the intraluminal device 2 of FIGS. 1a and 1b in the contracted or stressed condition of the device which assumes to facilitate its manipulation through the blood vessel to the deployment site.

[0048] As shown particularly in FIG. 1, the intraluminal device includes a plurality of filaments of elastic and non-elastic bio-compatible material, metal or plastic, extending helically in an interlaced manner to define a braided tube. Thus, shown in FIG. 1a are a first group of filaments 3 extending helically in one direction, and a second group of filaments 4 extending helically in the opposite direction, with the two groups of filaments being interwoven such that a filament 3 overlies a filament 4 at some points as shown at 5, and underlies a filament 4 at other points as shown at 6.

[0049] Filaments 3 and 4 thus define a braided tube having a plurality of windows 7. The inscribed diameter and the length of each window are shown at W_d and W_L, respectively, in the normal, expanded condition of the braided tube. These characteristics depend on, among other factors, the number of filaments and the braiding angle at the cross-over points of the two groups of filaments 3, 4.

[0050] FIG. 3 more particularly illustrates the above-described braid pattern in the expanded condition of the braided tube. Thus, as shown in FIG. 3, each filament 3a extending helically in one direction and is interwoven with one filament 4a extending helically in the opposite direction. Such a braid pattern is sometimes called a one over one pattern. FIG. 4 illustrates a one over two pattern, in which each filament 3b extending helically in one direction is interwoven with two filaments 4b extending helically in the opposite direction. FIG. 5 illustrates a further braid pattern that may be used, in which two (or more) filaments 3c extending helically in one direction are interwoven with two (or more) filaments 4c extending helically in the opposite direction.

[0051] The braid pattern illustrated in FIG. 3 is of highest flexibility, whereas that illustrated in FIG. 5 is of lower flexibility but of higher strength.

[0052] Such braided-tube intraluminal devices are well-known, for example as described in Wallsten et al, U.S. Pat. No. 5,061,275 and Wallsten U.S. Pat. No. 4,954,126, the contents of which are incorporated herein by reference. They are generally used as stents for providing support to a wall of a blood vessel, for implanting a graft, e.g., to treat an aneurysm (FIG. 9 of the latter patent), or for other purposes. As known, the braided tube is normally formed in an expanded condition (FIGS. 1a, 1b) having a diameter slightly larger than the diameter of the blood vessel so that when the device is deployed it becomes firmly embedded in the wall of blood vessel. However, the braided tube is capable of being stressed into a contracted condition, as shown in FIGS. 2a and 2b, wherein the diameter of the braided tube is decreased, and its length increased, to permit manipulation of the braided tube through the blood vessel to the site of implantation.

[0053] Further information concerning the construction and deployment of such braided-tube intraluminal devices is available in the above-cited patents, and also in Applicant's International Application PCT/IL01/00624, published 24 Jan. 2002, International Publication No. WO 02/05729, the contents of which are incorporated herein by reference.

[0054] When such braided tubes are used as stents within blood vessels, the filaments forming the braided tube are generally of a diameter exceeding 50 m and define windows producing a porosity index exceeding 80%. Such constructions, however, do not have the combination of flexibility to enable them to be easily manipulated through the tortuous blood vessels of the intracranial vascular system for preventing intracranial aneurysm ruptures, and blood permeability to enable them to be used for treating aneurysm at or proximate to perforating vessels, or a bifurcation leading to a branch vessel. These problems were sought to be overcome in the above-cited McCrory U.S. Pat. No. 5,951,599, Brown et al U.S. Pat. No. 6,093,199 and Wallsten U.S. Pat. No. 4,954,126, in producing braided tubes having a high-permeability portion to be deployed in the blood vessel and a low-permeability portion aligned with the aneurysm, but as indicated above such braided tubes constructions are difficult to produce, difficult to manipulate through the blood vessel, and difficult to accurately deploy at the site of the aneurysm.

[0055] According to the present invention, the filaments making up the braided tube are of a sufficiently small size in cross-section and define windows of a size such that the braided tube, when in its contracted condition, is sufficiently flexible so as to be easily manipulatable through the blood vessel to straddle the aneurysm; and when in its expanded condition straddling the aneurysm, reduces the flow of blood through the braided tube to the aneurysm sufficiently to decrease the possibility of rupture of the aneurysm. When the device is implantable in a blood vessel having an aneurysm at or proximate to one or more perforating vessels, or a bifurcation leading to a branch vessel, the windows defined by the filaments of the braided tube are such as to reduce the flow of blood therethrough to the aneurysm to decrease the possibility of rupturing it, but not to unduly reduce the blood flow to the perforating or branch vessels to the degree likely to cause damage to tissues supplied with blood by such vessels. As indicated earlier, experimental evidence indicates that patency can be maintained, and ischemia and infarction can be prevented, if less than 50% of the ostial diameter of the branch vessel is occluded.

[0056] FIG. 6 schematically illustrates how the bending rigidity or flexibility of a braided tube varies with the diameter of the filaments. Region A in FIG. 6 illustrates typical diameters in conventional stents used for supporting blood vessels, which region usually starts above 50 m and extends to several hundred m. Region B in FIG. 6 illustrates the region of filament diameters for use in constructing braided tubes in accordance with the present invention. The filament diameters in this region would be significantly smaller than in region A, preferably being 10-60 m, more preferably 20-40 m.

[0057] The foregoing dimensions apply to the diameters of filaments of circular cross-section. Where the filaments are of non-circular cross-section, such as of rectangular or square cross-section, the filaments would preferably have a circumference of 40-180 m. The circumference is defined in macro scale. The circumference can be enlarged micro-scale by adding roughness to the wire, in order to control the neointimal growth and making the circumference in micro scale longer while keeping the macro scale the same. In this case the surface cross section of the filament would be in the range 75-3000 m² preferably 300-1300 m².

[0058] As indicated earlier, the windows formed in the braided tube would also be preferably within a predetermined range such as to reduce the blood-flow in the portion of the braided tube applied over the aneurysm, but maintain sufficient blood flow in any perforating or branch vessels in the vicinity of the aneurysm. Preferably the length of the window, i.e., its long dimension as shown at W_L in FIG. 1a, would be within the range of 50-400 m, more preferably 80-300 m, in the expanded condition of the braided tube. Also, the braid angle (, FIG. 1a) would preferably be within the range of 150-20, more preferably 80-40 for high radial force and 100-140 for low radial force, in the expanded condition of the braided tube.

[0059] The diameter and length of the braided tube in its normal, expanded condition, will vary according to the location and anatomical dimensions at the particular site of the implantation. Preferably, the windows are globally (but not necessary locally) uniform in size such that any portion of the device can be placed across the neck of the aneurysm to reduce the blood flow thereto, while the remaining portions of the device firmly contact the walls of the blood vessel and securely anchors the device within the blood vessel.

[0060] The filaments can be made of any suitable material which are bio-compatible and which can be worked into a braid. Bio-compatible means any material that can be safely introduced and implanted in human or animal bodies for indefinite periods of time without causing any significant physiological damage. Preferably, the filaments are made of a material selected from among the 316L stainless steel, tantalum, and super elastic Nitinol, cobalt base alloy, polymer or any other suitable metal or metal combination. The filament can be coated with bio-compatible coatings Ulrich Sigwart, Endoluminal Stenting, W. B. Saunders Company Ltd., London, 1996. It is possible to use a combination of several filament materials in one device and combinations of several materials in one filament.

[0061] In some situations, it may be desired to implant the device in a portion of a lumen, e.g., an artery, varying significantly in diameter along its length. As will be appreciated, if a constant diameter braided tube device is inserted into such a variable-diameter lumen, this may result in a defective anchoring of the device at the larger diameter portion of the lumen, and in a possible risk of the migration of the device within the lumen. This problem can be easily overcome in several ways, e.g., by creating braided devices with variable diameters along their longitudinal axis, as described in the above-cited International Publication No. WO 02/05729, the contents of which are incorporated herein by reference.

[0062] FIG. 7 diagrammatically illustrates the braided tube device, therein generally designated 20, implanted in a blood vessel 22 having an aneurysm 24 in a region of a blood vessel 22 having a plurality of perforating vessels 26. The braided tube device 20 is introduced, in its contracted condition, into the blood vessel 22 and is manipulated to the implantation site by a microcatheter 28 where it is expanded such that it overlies the neck 30 of the aneurysm sac 24 and the perforating vessels 26. The braided tube is thus firmly bonded, by its expansion, to the inner surfaces of the blood vessel 20. As described above, the braided tube device 20 is constructed such that, in its expanded deployed condition as shown in FIG. 4, it reduces the flow of blood to the aneurysm sac 24 sufficiently to decrease the possibility of rupture thereof. While at the same time, it does not unduly reduce the flow of blood to the perforating vessels 26 to the degree likely to cause damage to the tissue supplied by the perforating vessels.

[0063] FIGS. 8, 9 and 10 illustrate the use of the braided tube device, generally designated 30, to treat an aneurysm in a blood vessel at or proximate to a bifurcation leading to one or more branch vessels.

[0064] Thus, FIG. 8 illustrates the braided tube device 30 implanted in a blood vessel 32 having an aneurysm 34 at the bifurcation leading to two branch vessels 36, 38. In the example illustrated in FIG. 8, the braided tube device 30 is deployed with one end embedded in the blood vessel 32 and the opposite end embedded within the branch vessel 38, so as to produce a reduced blood flow to the aneurysm sac 34, and also to the branch vessel 36. As described earlier, however, while the reduced blood flow to the aneurysm sac 34 is sufficient to reduce the possibility of rupture of the sac, the reduced blood flow to the branch 36 is not sufficient so as to be likely to cause damage to the tissues supplied by that branch vessel.

[0065] FIG. 9 illustrates a variation wherein one end of the braided tube 30 is bonded within the main blood vessel 32, and the opposite end is bonded within the branch vessel 36. In this case, the aneurysm sac 34 will also have a reduced supply of blood such as to reduce the possibility of its rupture, while the branch vessel 38 will have its blood supply reduced but not to the point of causing damage to the tissues supplied by that vessel.

[0066] FIG. 10 illustrates the variation wherein the opposite ends of the braided tube 30 are embedded in the two branch vessels 36, 38 at the bifurcation. In this case, the blood supply to the aneurysm sac 34 will also be reduced, but the blood supply to both branch vessels 36, 38 will be reduced but not sufficient to cause damage to the tissues supplied by those branch vessels.

[0067] Following are a number of examples of intraluminal devices constructed in accordance with the invention:

[0068] Given:

[0069] 1. Artery diameter3 mm

[0070] 2. Braiding angle 90

[0071] A porosity index of 70% can achieved by changing the filament diameter and the number of filaments as follows:

					Windows
	Artery	Braiding	Number	Filaments	Inscribed	Porosity
	Diameter	Angle	of Fil-	Width	Diameter	Index
	mm	deg	aments	m	m	%
1(a)	3	90	108	20	100	70
1(b)	3	90	78	27	140	70
1(c)	3	90	62	35	180	70
Note: For round cross-section filaments, the bending stiffness of 1(a) in its contracted condition is one-fifth that of 1(c) due to the smaller diameter filaments in 1(a).

[0072] Given:

[0073] 1. Artery diameter3 mm

[0074] 2. Braiding angle 90

[0075] 3. Filaments diameter27 m

[0076] The porosity index can changes by changing the number of filaments as follows:

					Windows
	Artery	Braiding	Number	Filament	Inscribed	Porosity
	Diameter	Angle	of Fil-	Diameter	Diameter	Index
	mm	deg	aments	m	m	%
2(a)	3	90	64	27	180	75
2(b)	3	90	108	27	140	70
2(c)	3	90	110	27	80	60
Note: For round cross-section filaments, the bending stiffness of 2(a) in its contracted condition is 60% of 2(c) due to the smaller number of filaments in 2(a).

[0077] Given:

[0078] 1. Artery diameter3 mm

[0079] 2. Number of filaments78

[0080] 3. Filaments diameter27 m

[0081] The porosity index can reduced from its maximum value at 90 in 3(a) by changing, i.e., increasing in 3(b) or decreasing in 3(c) the braiding angle as follows:

					Windows
	Artery	Braiding	Number	Filament	Inscribed	Porosity
	Diameter	Angle	of Fil-	diameter	Diameter	Index
	mm	deg	aments	m	m	%
3(a)	3	90	78	27	140	70
3(b)	3	106	78	27	110	65
3(c)	3	56	78	27	110	65

[0082] Given:

[0083] 1. Artery diameter3 mm

[0084] 2. Number of filaments78

[0085] 3. Braiding angle 90

[0086] The porosity index can changed by changing the filament diameter asfollows:

					Windows
	Artery	Braiding	Number	Filaments	Inscribed	Porosity
	Diameter	Angle	of Fil-	Diameter	Diameter	Index
	mm	deg	aments	m	m	%
4(a)	3	90	78	20	150	77
4(b)	3	90	78	27	140	70
4(c)	3	90	78	35	130	63
Note: For round cross-section filaments, the bending stiffness of 4(a)in its contracted condition is one-ninth that of 4(c) due to the smaller diameter filaments in 4(a).

[0087] While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations, modifications and applications of the invention may be made.

[0088] For example, the device could be composed of multiple tubular meshes, lying one above the other in layer-like formations. Also, the device could include a plurality of groups of filaments in the longitudinal and/or circumferential direction. Further, the invention could be implemented with respect to many of the other variations and applications described in the above-cited International Application PCT IL01/00624 incorporated herein by reference.

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