Patent Publication Number: US-2021186721-A1

Title: Endovascular prosthesis and delivery device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 14/711,061, filed May 13, 2015, which is a continuation U.S. patent application Ser. No. 14/065,788, filed Oct. 29, 2013, now U.S. Pat. No. 9,056,024, issued Jun. 16, 2015, which is a continuation of International Application No. PCT/CA2012/000379, filed Apr. 27, 2012, which was published in English and designated the U.S., which claims benefit of provisional U.S. Patent Appln. No. 61/457,604 and provisional U.S. Patent Appln. No. 61/457,605, each filed Apr. 29, 2011, the contents of all incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     In one of its aspects, the present invention relates to an endovascular prosthesis. In another of its aspects, the present invention relates to a method of treating an aneurysm in a patient. In another of its aspects, the present invention relates to an endovascular prosthesis delivery device. Other aspects of the invention will be apparent to those of skill in the art having in hand the present specification. 
     Description of the Prior Art 
     As is known in the art, an aneurysm is an abnormal bulging outward in the wall of an artery. In some cases, the bulging may be in the form of a smooth bulge outward in all directions from the artery—this is known as a “fusiform aneurysm”. In other cases, the bulging may be in the form of a sac arising from an arterial branching point or from one side of the artery—this is known as a “saccular aneurysm”. 
     While aneurysms can occur in any artery of the body, it is usually those which occur in the brain which lead to the occurrence of a stroke. Most saccular aneurysms which occur in the brain have a neck which extends from the cerebral blood vessel and broadens into a pouch which projects away from the vessel. 
     The problems caused by such aneurysms can occur in several different ways. For example, if the aneurysm ruptures, blood enters the brain or the subarachnoid space (i.e., the space closely surrounding the brain)—the latter is known as an aneurysmal subarachnoid hemorrhage. This is followed by one or more of the following symptoms: nausea, vomiting, double vision, neck stiffness and loss of consciousness. Aneurysmal subarachnoid hemorrhage is an emergency medical condition requiring immediate treatment. Indeed, 10-15% of patients with the condition die before reaching the hospital for treatment. More than 50% of patients with the condition will die within the first thirty days after the hemorrhage. Of those patients who survive, approximately half will suffer a permanent stroke. Some of these strokes occur one to two weeks after the hemorrhage itself from vasospasm in cerebral vessels induced by the subarachnoid hemorrhage. Aneurysms also can cause problems which are not related to bleeding although this is less common. For example, an aneurysm can form a blood clot within itself which can break away from the aneurysm and be carried downstream where it has the potential to obstruct an arterial branch causing a stroke (e.g., an ischemic stroke). Further, the aneurysm can also press against nerves (this has the potential of resulting in paralysis or abnormal sensation of one eye or of the face) or the adjacent brain (this has the potential of resulting in seizures). 
     Given the potentially fatal consequences of the aneurysms, particularly brain aneurysms, the art has addressed treatment of aneurysms using various approaches. 
     Generally, aneurysms may be treated from outside the blood vessels using surgical techniques or from the inside using endovascular techniques (the latter falls under the broad heading of interventional (i.e., non-surgical) techniques). 
     Surgical techniques usually involve a craniotomy requiring creation of an opening in the skull of the patient through which the surgeon can insert instruments to operate directly on the brain. In one approach, the brain is retracted to expose the vessels from which the aneurysm arises and then the surgeon places a clip across the neck of the aneurysm thereby preventing arterial blood from entering the aneurysm. If there is a clot in the aneurysm, the clip also prevents the clot from entering the artery and obviates the occurrence of a stroke. Upon correct placement of the clip the aneurysm will be obliterated in a matter of minutes. Surgical techniques are the most common treatment for aneurysms. Unfortunately, surgical techniques for treating these conditions are regarded as major surgery involving high risk to the patient and necessitate that the patient have strength even to have a chance to survive the procedure. 
     As discussed above, endovascular techniques are non-surgical techniques and are typically performed in an angiography suite using a catheter delivery system. Specifically, known endovascular techniques involve using the catheter delivery system to pack the aneurysm with a material which prevents arterial blood from entering the aneurysm—this technique is broadly known as embolization. One example of such an approach is the Guglielmi Detachable Coil which involves intra-aneurysmal occlusion of the aneurysm via a system which utilizes a platinum coil attached to a stainless steel delivery wire and electrolytic detachment. Thus, once the platinum coil has been placed in the aneurysm, it is detached from the stainless steel delivery wire by electrolytic dissolution. Specifically, the patient&#39;s blood and the saline infusate act as the conductive solutions. The anode is the stainless steel delivery wire and the cathode is the ground needle which is placed in the patient&#39;s groin. Once current is transmitted through the stainless steel delivery wire, electrolytic dissolution will occur in the uninsulated section of the stainless steel detachment zone just proximal to the platinum coil (the platinum coil is of course unaffected by electrolysis). Other approaches involve the use of materials such as cellulose acetate polymer to fill the aneurysm sac. While these endovascular approaches are an advance in the art, they are disadvantageous. Specifically, the risks of these endovascular approaches include rupturing the aneurysm during the procedure or causing a stroke (e.g., an ischemic stroke) due to distal embolization of the device or clot from the aneurysm. Additionally, concern exists regarding the long term results of endovascular aneurysm obliteration using these techniques. Specifically, there is evidence of intra-aneurysmal rearrangement of the packing material and reappearance of the aneurysm on follow-up angiography. 
     One particular type of brain aneurysm which has proven to be very difficult to treat, particularly using the surgical clipping or endovascular embolization techniques discussed above occurs at the distal basilar artery. This type of aneurysm is a weak outpouching, usually located at the terminal bifurcation of the basilar artery. Successful treatment of this type of aneurysm is very difficult due, at least in part, to the imperative requirement that all the brainstem perforating vessels be spared during surgical clip placement. 
     Unfortunately, there are occasions when the size, shape and/or location of an aneurysm make both surgical clipping and endovascular embolization not possible for a particular patient. Generally, the prognosis for such patients is not good. 
     Accordingly, while the prior art has made advances in the area of treatment of aneurysms, there is still room for improvement, particularly in endovascular embolization since it is such an attractive alternative to major surgery. 
     In International Publication Number WO 99/40873 [Marotta et al. (Marotta)], published Aug. 19, 1999, there is taught a novel endovascular approach useful in blocking of an aneurysmal opening, particularly those in saccular aneurysms, leading to obliteration of the aneurysm. The approach is truly endovascular in that, with the endovascular prosthesis taught by Marotta, there is no requirement to pack the aneurysmal sac with a material (e.g., such is used with the Guglielmi Detachable Coil). Rather, the endovascular prosthesis taught by Marotta operates on the basis that it serves to block the opening to the aneurysmal sac thereby obviating the need for packing material. Thus, the endovascular prosthesis taught by Marotta is an important advance in the art since it obviates or mitigates many of the disadvantages of the prior art. The endovascular prosthesis taught by Marotta comprises a leaf portion capable of being urged against the opening of the aneurysm thereby closing the aneurysm. In the endovascular prosthesis taught by Marotta, the leaf portion is attached to, and independently moveable with respect to, a body comprising at least one expandable portion. The expandable portion is expandable from a first, unexpanded state to a second, expanded state with a radially outward force thereon. Thus, the body serves the general purpose of fixing the endovascular prosthesis in place at a target body passageway or vascular lumen in the vicinity at which the aneurysmal opening is located and the leaf portion serves the purpose of sealing the aneurysmal opening thereby leading to obliteration of the aneurysm. Thus, as taught by Marotta, the leaf portion functions and moves independently of the body of the endovascular prosthesis. 
     While the endovascular prosthesis taught by Marotta is a significant advance in the art, there is still room for improvement. Specifically, in the preferred embodiment of the endovascular prosthesis taught by Marotta, once the device is partially or fully deployed, for all intents and purposes, it is not possible to retrieve the prosthesis—e.g., for re-positioning. While this may not be a problem in most instances, there are occasions where the physician wishes to be able to retrieve the device so that it may be repositioned for optimum placement. 
     Accordingly, there remains a need in the art for an endovascular prosthesis that may be retrieved by the physician after it has been partially or fully deployed. It would be particularly advantageous to have a self-expanding endovascular prosthesis that may be retrieved by the physician after it has been partially or fully deployed. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art. 
     It is another object of the present invention to provide a novel endovascular prosthesis. 
     It is another object of the present invention to provide a novel endovascular prosthesis delivery device. 
     Accordingly, in one of its aspects, the present invention provides an endovascular prosthesis comprising 
     a first expandable portion expandable from a first, unexpanded state to a second, expanded state to urge the first expandable portion against a vascular lumen; and 
     a retractable leaf portion attached to the first expandable portion, the retractable leaf portion comprising at least one spine portion and a plurality of rib portions attached to the spine portion, longitudinally adjacent pairs of rib portions being free of interconnecting struts. 
     In another of its aspects, the present invention provides an endovascular prosthesis delivery device comprising a tubular member having a distal portion and a proximal portion, the distal portion having a porous surface defined by a plurality of circumferential rings, adjacent pairs of circumferential rings being interconnected by at least one longitudinal strut, the porous surface comprising a decreasing gradient of longitudinal strut circumferential width between longitudinal struts connected to opposed sides of a single circumferential ring in a direction from the proximal portion to the distal portion. 
     In another of its aspects, the present invention provides an endovascular prosthesis delivery device comprising a tubular member having a distal portion and a proximal portion, the distal portion having a porous surface defined by a plurality of circumferential rings, adjacent pairs of circumferential rings being interconnected by at least one longitudinal strut, the porous surface comprising a increasing porosity in a direction from the proximal portion to the distal portion. 
     In a preferred embodiment, the porous surface of the delivery device comprises a cover layer, preferably made of a polymer and/or preferably disposed substantially continuously over the porous surface, to reduce friction between the delivery device and the inner surface of a delivery catheter, facilitating a low force delivery of the endovascular prosthesis. The nature of the cover layer will be described in more detail hereinbelow. 
     Thus, the present inventors have discovered a novel endovascular prosthesis that can be unsheathed and re-sheathed for repositioning of the endovascular prosthesis prior to final deployment thereof. This provides the clinician with a significant advantage over the prior art devices described above. The present endovascular prosthesis comprises a first expandable portion expandable from a first, unexpanded state to a second, expanded state to urge the first expandable portion against the wall of the vascular lumen such as an artery. The endovascular prosthesis further comprises a retractable leaf portion attached to the first expandable portion; the retractable leaf portion serves to facilitate stasis and thrombotic occlusion of the aneurysm. The retractable leaf portion comprises at least one spine portion and a plurality of rib portions attached to the spine portion. Importantly, longitudinally adjacent pairs of rib portions are free of intricate connecting struts. The present inventors conducted a number of tests and have discovered that when connections are made between adjacent rib portions, the retractability of the leaf portion is significantly compromised and, in many cases, the leaf portion may not be retracted at all. 
     In addition, the present endovascular prosthesis is advantageous in that it has a natural tendency to flex in a manner such that the spine portion is on the outside of the bend. This is highly advantageous, especially when the device is implanted in a bifurcated body passageway. An additional advantage is that the orientation of the rib portions, coupled with the flex, particularly facilitates atraumatic and accurate delivery and deployment of the present endovascular prosthesis. 
     While not wishing to be bound by any particular theory or mode of action, it has been found that the rib portions of the present endovascular prosthesis are compressible whereas the spine in not compressible; therefore under an axial loading in the sheath, the rib portions have a tendency to compress and induce a bend that facilitates proper orientation during delivery in the correct direction. 
     In a highly advantageous embodiment, the present endovascular prosthesis is configured to be self-expanding. This means that the device may be sheathed or otherwise restrained prior to deployment and after initial delivery of the device, the sheath or restraint is partially retracted thereby allowing the device to self-expand. This allows for partial and progressive deployment of the device with the advantage that the clinician can re-sheath the device if initial deployment of the endovascular prosthesis is not in the correct position with respect to the target anatomy of the patient. In this context, it is also possible to achieve an additional rotational orientation of the present endovascular prosthesis by delivering the prosthesis using a ‘torquable catheter’. This involves partially deploying the prosthesis to evaluate rotational orientation. If the rotation of the device relative to the aneurysm neck needs to be adjusted, the prosthesis may be retracted into the torquable catheter, torqued into the another orientation and then these steps are repeated until the prosthesis is deemed to be in the correct position relative to the aneurysm neck, after which the prosthesis may be fully unsheathed and detached from the delivery device using a number of techniques such as those described in more detail below. This is another highly advantageous feature of the present endovascular prosthesis. 
     Another aspect of the present invention relates to the provision of an endovascular prosthesis delivery device which comprises the tubular member having a distal portion and a proximal portion. The distal portion of the endovascular prosthesis has a porous surface made up of the number of circumferential rings with adjacent pairs of these rings being interconnected by one or more longitudinal struts. The porous surface in the distal portion of the endovascular prosthesis delivery device has a decrease in the width between a pair of the longitudinal struts connected to opposed sides of a given circumferential ring. This decrease in circumferential width of longitudinal strut runs in a direction from the proximal portion of the tubular member to the distal portion of the tubular member. Consequently, this means that the distal portion of the tubular member becomes progressively more flexible in a direction toward the distal most end of the tubular member. This feature facilitates navigating the endovascular prosthesis delivery device through tortuous anatomy while providing sufficient integrity and radial rigidity at the user end of the tubular member to be able to insert the device in the patient and navigate it completely to the target anatomy all the while obviating or mitigating kinking of the endovascular prosthesis delivery device. In a preferred embodiment, there is a decrease in the circumferential width between pairs of the circumferential rings running in a direction from proximal portion to the distal portion. 
     In a particularly preferred embodiment of the present endovascular prosthesis delivery device, the circumferential rings comprise a series of alternating peaks and valleys. In this preferred embodiment, it is further preferred that the longitudinal struts connect a valley from one circumferential ring with a valley in an adjacent circumferential ring. This so-called valley-valley connection embodiment is characterized by having the peaks in adjacent circumferential rings longitudinally aligned but unconnected. The advantage of this approach is that when the endovascular prosthesis delivery device is flexed to a certain degree, the adjacent peaks will contact each other prior to the endovascular prosthesis delivery device kinking, bending too much and yielding/breaking. 
     The present endovascular prosthesis is believed to be particularly useful in the treatment of aneurysms such as those described hereinabove and is therefore believed to provide a significant alternative to the conventional surgical techniques described hereinabove. Additionally, it is envisaged that the present endovascular prosthesis may be used in the treatment of certain aneurysms which are diagnosed as being inoperable. The present endovascular prosthesis also is believed to provide a significant advantage of current endovascular approaches such as the Guglielmi Detachable Coil described hereinabove. Specifically, since the present endovascular prosthesis does not rely on insertion into the aneurysm of a metal packing material (e.g., platinum coil), the risk of rupturing the aneurysm is mitigated as is the risk of intra-aneurysmal rearrangement of the metal packing material and subsequent reappearance of the aneurysm. Of course, those of skill in the art will recognize that there may be certain situations where the present endovascular prosthesis could be used in combination with Guglielmi Detachable Coils described hereinabove—e.g., to treat an aneurysm with a large neck in which an added structure across the neck (i.e., the present endovascular prosthesis) would help hold the coils with in the aneurysmal sac (this would obviate or mitigate the possibility of a coil exiting the aneurysm sac and causing an ischemic stroke). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like parts, and in which: 
         FIG. 1  illustrates a two-dimensional representation of a first embodiment of the present endovascular prosthesis; 
         FIG. 1  a is an enlarged view of a portion of  FIG. 1  identifying various elements in the design of the prosthesis; 
         FIG. 2  illustrates a perspective view of the endovascular prosthesis illustrated in  FIG. 1 ; 
         FIG. 3  illustrates a top view of the endovascular prosthesis illustrated in  FIGS. 1-2  coupled to a delivery device; 
         FIG. 4  illustrates delivery of the endovascular prosthesis illustrated in  FIGS. 1-3  to occlude an aneurysm; 
         FIGS. 5-6  illustrate a portion of the endovascular prosthesis illustrated, in a transparent sheath, in  FIGS. 1-4  as it is reversibly sheathed and unsheathed; 
         FIG. 7  illustrates the endovascular prosthesis illustrated in  FIGS. 1-6  after it has been released from the delivery device and is in the correct position to treat the aneurysm; 
         FIG. 8  illustrates the endovascular prosthesis illustrated in  FIGS. 1-7  after it has been deployed and is occluding an aneurysm (also, the delivery device is pulled away from the endovascular prosthesis); 
         FIG. 9  illustrates a two-dimensional representation of a second embodiment of the present endovascular prosthesis; 
         FIG. 10  illustrates a perspective view of the endovascular prosthesis illustrated in  FIG. 9 ; 
         FIG. 11  illustrates a perspective view of the endovascular prosthesis illustrated in  FIGS. 9-10  coupled to a delivery device; 
         FIGS. 12( a )-12( c )  illustrate details of how the endovascular prosthesis illustrated in  FIGS. 9-11  is coupled to the delivery device; 
         FIG. 13  illustrates a two-dimensional representation of a third embodiment of the present endovascular prosthesis; 
         FIG. 14  illustrates a perspective view of the endovascular prosthesis illustrated in  FIG. 13  as it is coupled to a delivery device; 
         FIGS. 15( a )-15( d )  illustrate further detail of coupling of the endovascular prosthesis illustrated in  FIGS. 13-14  to the delivery device; 
         FIG. 16  illustrates a two-dimensional representation of a fourth embodiment of the present endovascular prosthesis; 
         FIG. 17  illustrates a perspective view of the endovascular prosthesis illustrated in  FIG. 16 ; 
         FIGS. 18( a )-18( f ) , and  19 - 21  illustrate, in a step-wise manner, deployment of the endovascular prosthesis illustrated in  FIGS. 16-17  in an aneurysm located at the junction of a bifurcated artery; 
         FIGS. 22-24  illustrate, in a step-wise manner, release of one end of the endovascular prosthesis illustrated in  FIGS. 16-21  from the delivery device; 
         FIG. 25  illustrates a perspective view of a portion of the delivery device used to deliver the endovascular prosthesis illustrated in  FIGS. 16-24 ; 
         FIGS. 26-27  illustrate an enlarged view of the portion of the delivery device illustrated in  FIG. 25  and how it is coupled to an opposite end (cf.  FIGS. 22-24 ) of the endovascular prosthesis illustrated in  FIGS. 16-24 ; 
         FIG. 28  illustrates a two-dimensional representation of a fifth embodiment of the present endovascular prosthesis; 
         FIG. 29  illustrates a perspective view of the endovascular prosthesis illustrated in  FIG. 28 ; 
         FIGS. 30-32  illustrate, in a step-wise manner, release of the endovascular prosthesis illustrated in  FIGS. 28-29  from its delivery device; 
         FIGS. 33-35  illustrate additional views of a delivery device used to deliver the endovascular prosthesis illustrated in  FIGS. 28-32 ; 
         FIG. 36  illustrates a two-dimensional representation of a sixth embodiment of the present endovascular prosthesis; 
         FIG. 37  illustrates a perspective view of the endovascular prosthesis illustrated in  FIG. 36  connected to a delivery device therefor; 
         FIGS. 38( i ) -( iii ) illustrate a portion of a preferred embodiment of the present endovascular prosthesis delivery device (including enlarged views in  FIGS. 38( a )-( d ) ); and 
         FIGS. 39( a )-39( d ), 40( a )-40( d ) ,  41 ,  42 ( a )- 42 ( c ), and  43 ( a )- 43 ( e ) illustrate various views of various endovascular prosthesis delivery devices that are shown throughout  FIGS. 1-37 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In one of its aspects, the present invention relates to an endovascular prosthesis comprising: a first expandable portion expandable from a first, unexpanded state to a second, expanded state to urge the first expandable portion against a vascular lumen; and a retractable leaf portion attached to the first expandable portion, the retractable leaf portion comprising at least one spine portion and a plurality of rib portions attached to the spine portion, longitudinally adjacent pairs of rib portions being free of interconnecting struts. Preferred embodiments of this endovascular prosthesis may include any one or a combination of any two or more of any of the following features:
         a single spine portion is connected to the first expandable portion;   the single spine portion comprises a row of rib portions connected to one side of the single spine portion;   the single spine portion comprises a pair of rows of rib portions, each row of rib portions connected to one side of the single spine portion;   the single spine portion comprises a pair of rows of rib portions connected to opposed sides of the single spine portion;   in two dimensions, each row of rib portions is a substantial mirror image of an adjacent row of rib portions along the single spine portion;   a first row of rib portions is connected at a plurality of first connection points to the single spine portion and a second row of rib portions is connected at a plurality of second connection points to the single spine portion, the plurality of first connection points and the plurality of second connection points being longitudinally aligned with respect to one another;   a first row of rib portions is connected at a plurality of first connection points to the single spine portion and a second row of rib portions is connected at a plurality of second connection points to the single spine portion, the plurality of first connection points and the plurality of second connection points being longitudinally staggered with respect to one another;   the single spine portion is linear;   the single spine portion is curvilinear;   the single spine portion is curved;   the single spine portion comprising an undulating pattern comprising alternating peaks and valleys;   at least some rib portions are connected to the peaks in the undulating pattern;   each rib portion is connected to a peak in the undulating pattern;   in two dimensions, each rib portion is configured substantially to form an acute angle with respect to a spine longitudinal axis of the single spine portion;   in two dimensions, each rib portion comprises a rib proximal portion, a rib distal portion and a rib intermediate portion disposed therebetween;   in two dimensions, each rib portion has a substantially constant circumferential width;   in two dimensions, each rib portion has a variable circumferential width;   in two dimensions, the rib intermediate portion has a circumferential width less than at least one of the rib proximal portion and the rib distal portion;   the rib intermediate portion has a circumferential width less than both of the rib proximal portion and the rib distal portion;   the rib proximal portion has a circumferential width in the range of from about 0.0010 to about 0.0120 inches;   the rib proximal portion has a circumferential width in the range of from about 0.0017 to about 0.0096 inches;   the rib proximal portion has a circumferential width in the range of from about 0.0024 to about 0.0072 inches;   the rib proximal portion is from about 1% to about 10% of the overall length of the rib portion;   the rib proximal portion is from about 2% to about 6% of the overall length of the rib portion;   the rib proximal portion is about 3% of the overall length of the rib portion;   rib intermediate portion has a circumferential width in the range of from about 0.0005 to about 0.0100 inches;   rib intermediate portion has a circumferential width in the range of from about 0.0011 to about 0.0062 inches;   rib intermediate portion has a circumferential width in the range of from about 0.0016 to about 0.0024 inches;   the rib intermediate portion is from about 25% to about 90% of the overall length of the rib portion;   the rib intermediate portion is from about 60% to about 90% of the overall length of the rib portion;   the rib intermediate portion is about 90% of the overall length of the rib portion;   rib distal portion has a circumferential width in the range of from about 0.0010 to about 0.0120 inches;   rib distal portion has a circumferential width in the range of from about 0.0013 to about 0.0072 inches;   rib distal portion has a circumferential width in the range of from about 0.0016 to about 0.0024 inches;   the rib distal portion is up to about 25% of the overall length of the rib portion;   the rib distal portion is from about 4% to about 16% of the overall length of the rib portion;   the rib distal portion is up to about 7% of the overall length of the rib portion;   the rib proximal portion is configured to form a rib proximal portion acute angle with respect to a longitudinal axis of the endovascular prosthesis;   the rib proximal portion acute angle is in the range of from about 15° to about 90°;   the rib proximal portion acute angle is in the range of from about 35° to about 60°;   the rib proximal portion acute angle is about 45°;   the rib distal portion is configured to form a rib distal portion angle with respect to a rib intermediate portion of the endovascular prosthesis;   the rib distal portion angle is in the range of from about 0° to about 120°;   the rib distal portion angle is in the range of from about 3° to about 60°;   the rib distal portion angle is about 8°;   the rib intermediate portion is configured to form a rib intermediate portion acute angle with respect to a longitudinal axis of the endovascular prosthesis;   the rib intermediate portion acute angle is in the range of from about 5° to about 140°;   the rib intermediate portion acute angle is in the range of from about 22° to about 86°;   the rib intermediate portion acute angle is about 45°;   the rib intermediate portion comprises: (i) a rib intermediate first portion connected to the rib proximal portion and configured to form a rib intermediate first portion acute angle with respect to a longitudinal axis of the endovascular prosthesis, and (ii) a rib intermediate second portion connected to the rib distal portion and configured to form a rib intermediate second portion acute angle with respect to a longitudinal axis of the endovascular prosthesis;   the rib intermediate first portion acute angle is less than the rib intermediate second portion acute angle;   the rib intermediate first portion acute angle is in the range of from about 5° to about 140°;   the rib intermediate first portion acute angle is in the range of from about 22° to about 66°;   the rib intermediate first portion acute angle is about 30°;   the rib intermediate second portion acute angle is in the range of from about 5° to about 140°;   the rib intermediate second portion acute angle is in the range of from about 42° to about 86°;   the rib intermediate second portion acute angle is about 60°;   the rib intermediate first portion has a circumferential width in the range of from about 0.0010 to about 0.0100 inches;   the rib intermediate first portion has a circumferential width in the range of from about 0.0014 to about 0.0062 inches;   the rib intermediate first portion has a circumferential width in the range of from about 0.0018 to about 0.0024 inches;   the rib intermediate first portion is from about 5% to about 25% of the overall length of the rib portion;   the rib intermediate first portion is from about 7% to about 17% of the overall length of the rib portion;   the rib intermediate first portion is about 9% of the overall length of the rib portion;   the rib intermediate second portion has a circumferential width in the range of from about 0.0005 to about 0.0070 inches;   the rib intermediate second portion has a circumferential width in the range of from about 0.0011 to about 0.0044 inches;   the rib intermediate second portion has a circumferential width in the range of from about 0.0016 to about 0.0018 inches;   the rib intermediate second portion is from about 25% to about 90% of the overall length of the rib portion;   the rib intermediate second portion is from about 53% to about 85% of the overall length of the rib portion;   the rib intermediate second portion is about 81% of the overall length of the rib portion;   in two dimensions, the rib distal portion of each rib portion is directed away from the first expandable portion;   in two dimensions, the rib distal portion of each rib portion is directed toward the first expandable portion;   in two dimensions, each rib portion is linear;   in two dimensions, each rib portion is curvilinear;   in two dimensions, each rib portion is curved;   in two dimensions, each rib portion comprises at least two sub-portions each sub-portion form a different angle with respect to a longitudinal axis of the endovascular prosthesis;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance ranging from about 0.0254 mm to about 10 mm;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance ranging from about 0.0254 mm to about 5 mm;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance ranging from about 0.1400 mm to about 3 mm;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance ranging from about 0.1400 mm to about 1 mm;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance ranging from about 0.1400 mm to about 0.8 mm;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance ranging from about 0.1400 mm to about 0.6 mm;   a pair of longitudinally adjacent rib portions are spaced at a connection point to the spine portion at a distance of about 0.254 mm;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy less than about 75% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy from about 5% to about 75% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy from about 5% to about 65% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy from about 10% to about 50% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy from about 15% to about 40% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy less than about 10% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy less than about 8% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy less than about 5% of a surface area of the retractable leaf portion;   in two dimensions, the at least one spine portion and the plurality of rib portions attached to the spine portion combine to occupy less than about 3% of a surface area of the retractable leaf portion;   the retractable leaf portion further comprises a cover layer connected to the plurality of rib portions;   the retractable leaf portion comprises less than 10 longitudinally spaced rib portions connected on one side of the spine portion;   the retractable leaf portion comprises less than 8 longitudinally spaced rib portions connected on one side of the spine portion;   the retractable leaf portion comprises less than 6 longitudinally spaced rib portions connected on one side of the spine portion;   the retractable leaf portion contains only 3 longitudinally spaced rib portions connected on one side of the spine portion;   the ratio of the perpendicular distance from the longitudinal axis to the distal tip portion of the rib portion to 50% of the circumference of the first expandable portion in the second, expanded state is in the range of from about 1:4 to about 1:1;   in two dimensions, the ratio of the perpendicular distance from the longitudinal axis to the distal tip portion of the rib portion to 50% of the circumference of the first expandable portion in the second, expanded state is in the range of from about 1:2.5 to about 1:1.5;   in two dimensions, the ratio of the perpendicular distance from the longitudinal axis to the distal tip portion of the rib portion to 50% of the circumference of the first expandable portion in the second, expanded state is about 5:9;   the at least one spine portion is curved about an axis transverse to a longitudinal axis of the endovascular prosthesis;   the at least one spine portion is curved about an axis substantially orthogonal to a longitudinal axis of the endovascular prosthesis;   the axis is opposed to the plurality of rib portions relative to the at least one spine portion;   the at least one spine portion comprises a first radius of curvature over the length of the at least one spine portion about an axis transverse to a longitudinal axis of the endovascular prosthesis;   the first radius of curvature is substantially constant from a proximal portion of the at least one spine portion to a distal portion of the at least one spine portion;   the first radius of curvature is variable from a proximal portion of the at least one spine portion to a distal portion of the at least one spine portion;   the first radius of curvature decreases from a proximal portion of the at least one spine portion to a distal portion of the at least one spine portion.   the retractable leaf portion comprises a second radius of curvature over the length of the at least one spine portion about a longitudinal axis of the endovascular prosthesis;   the second radius of curvature is substantially constant from a proximal portion of the retractable portion to a distal portion of the retractable portion;   the second radius of curvature is variable from a proximal portion of the retractable leaf portion to a distal portion of the retractable leaf portion;   the second radius of curvature increases from a proximal portion of the retractable leaf portion to a distal portion of the retractable leaf portion;   in an expanded configuration of the endovascular prosthesis, the retractable leaf portion comprises an arc of curvature about a longitudinal axis of the endovascular prosthesis in the range of from about 90° to about 360°;   in an expanded configuration of the endovascular prosthesis, the retractable leaf portion comprises an arc of curvature about a longitudinal axis of the endovascular prosthesis in the range of from about 120° to about 270°;   in an expanded configuration of the endovascular prosthesis, the retractable leaf portion comprises an arc of curvature about a longitudinal axis of the endovascular prosthesis in the range of from about 150° to about 250°;   in an expanded configuration of the endovascular prosthesis, the retractable leaf portion comprises an arc of curvature about a longitudinal axis of the endovascular prosthesis in the range of from about 175° to about 225°;   in an expanded configuration of the endovascular prosthesis, the retractable leaf portion comprises an arc of curvature about a longitudinal axis of the endovascular prosthesis of about 200°;   the first expandable portion has a diameter in the second, expanded state in range of from about 2 mm to about 40 mm;   the first expandable portion has a diameter in the second, expanded state in range of from about 2 mm to about 30 mm;   the first expandable portion has a diameter in the second, expanded state in range of from about 2 mm to about 20 mm;   the first expandable portion has a diameter in the second, expanded state in range of from about 2 mm to about 10 mm;   the first expandable portion has a diameter in the second, expanded state in range of from about 2.5 mm to about 5 mm;   a single spine portion is connected to the first expandable portion and a loop portion is connected to a distal portion of the single spine portion;   a single spine portion is connected to the first expandable portion and a split loop portion connected to a distal portion of the single spine portion;   the loop portion comprises a radioopaque portion;   the endovascular prosthesis further comprises a second expandable portion expandable from a first, unexpanded state to a second, expanded state to urge the first expandable portion against a vascular lumen;   the second expandable portion comprises a radioopaque portion;   the endovascular prosthesis is manufactured from a tubular starting material;   the endovascular prosthesis is manufactured from a tubular starting material on which a cutting technique has been applied;   the endovascular prosthesis is manufactured from a tubular starting material on which a laser cutting technique has been applied;   tubular wall has a radial thickness in the range of from about 0.0005 to about 0.0200 inches;   the tubular wall has a radial thickness in the range of from about 0.0015 to about 0.0100 inches;   the tubular wall has a radial thickness of about 0.0025 inches;   the first expandable portion comprises a radioopaque portion;   the prosthesis is constructed from a self-expanding material;   the prosthesis is constructed from a shape memory alloy;   the prosthesis is constructed from nitinol;   the prosthesis is constructed from a metallic material; and/or   the prosthesis is constructed from a polymer material.       

     In one of its aspects, the present invention relates to an endovascular prosthesis delivery device comprising a tubular member having a distal portion and a proximal portion, the distal portion having a porous surface defined by a plurality of circumferential rings, adjacent pairs of circumferential rings being interconnected by at least one longitudinal strut, the porous surface comprising a decreasing gradient of longitudinal strut circumferential width between longitudinal struts connected to opposed sides of a single circumferential ring in a direction from the proximal portion to the distal portion. Preferred embodiments of this endovascular prosthesis delivery device may include any one or a combination of any two or more of any of the following features:
         each circumferential ring comprises alternating peaks and valleys;   the at least one longitudinal strut connects a first valley in a first circumferential ring to a second valley in a second circumferential ring adjacent to the first circumferential ring;   the at least one longitudinal strut connects to a mid-point of the first valley;   the at least one longitudinal strut connects to a mid-point of the second valley;   the at least one longitudinal strut connects to: (i) a mid-point of the first valley, and (ii) a mid-point of the second valley;   the first circumferential ring and the second circumferential ring each comprise at least one pair of alternating peaks and valleys;   the first circumferential ring and the second circumferential ring each comprise at least two pairs of alternating peaks and valleys;   the endovascular prosthesis delivery device comprises a longitudinal strut for each peak;   the endovascular prosthesis delivery device comprises a longitudinal strut for each valley;   the endovascular prosthesis delivery device comprises a longitudinal strut for each pair of alternating peaks and valleys in first circumferential ring or the second circumferential ring;   the first circumferential ring and the second circumferential ring each comprise one pair of alternating peaks and valleys;   two longitudinal struts interconnect the first circumferential ring and the second circumferential ring;   the plurality of circumferential rings comprises a first circumferential ring, a second circumferential ring axially spaced from the first circumferential ring and a third circumferential ring axially spaced from the second circumferential ring;   the first circumferential ring and the third circumferential ring are spaced at a distance that is in the range from about 100% to about 300% of the diameter of the tubular member;   the first circumferential ring and the third circumferential ring are spaced at a distance that is in the range from about 175% to about 225% of the diameter of the tubular member;   the first circumferential ring and the third circumferential ring are spaced at a distance that is about 200% of the diameter of the tubular member;   the porous surface has a proximal porous portion and a distal porous portion disposed distally of the proximal porous portion;   the endovascular prosthesis delivery device comprises a first longitudinal strut disposed in the distal porous portion and a second longitudinal strut disposed in the proximal porous portion, with the proviso that a first longitudinal strut circumferential width of the first longitudinal strut is less than a second longitudinal strut circumferential width of the second longitudinal strut;   the first longitudinal strut circumferential width and the second longitudinal strut circumferential width each are in the range of from about 0.0010 in to about 0.0500 in;   the first longitudinal strut circumferential width and the second longitudinal strut circumferential width each are in the range of from about 0.0035 in to about 0.0300 in;   the first longitudinal strut circumferential width and the second longitudinal strut circumferential width each are in the range of from about 0.0045 in to about 0.0150 in;   the first longitudinal strut circumferential width is greater than about 0.0010 in and the second longitudinal strut circumferential width is less than about 0.0500 in;   the first longitudinal strut circumferential width is greater than about 0.0035 in and the second longitudinal strut circumferential width is less than about 0.0300 in;   the first longitudinal strut circumferential width is greater than about 0.0045 in and the second longitudinal strut circumferential width is less than about 0.0150 in;   the endovascular prosthesis delivery device comprises a first circumferential ring disposed in the distal porous portion and a second circumferential ring disposed in the proximal porous surface, with the proviso that a first axial width of the first circumferential ring is less than a second axial width of the second circumferential ring;   the first axial width and the second axial width each are in the range of from about 0.0010 in to about 0.0450 in;   the first axial width and the second axial width each are in the range of from about 0.0040 in to about 0.0325 in;   the first axial width and the second axial width each are in the range of from about 0.0050 in to about 0.0250 in;   the first axial width is greater than about 0.0010 in and the second axial width is less than about 0.0450 in;   the first axial width is greater than about 0.0040 in and the second axial width is less than about 0.0325 in;   the first axial width is greater than about 0.0050 in and the second axial width is less than about 0.0250 in;   the endovascular prosthesis delivery device comprises a first pair of adjacent circumferential rings disposed in the distal porous portion and a second pair of circumferential rings disposed in the proximal porous surface, with the proviso that a first minimum distance between the first pair of adjacent circumferential rings is greater than a second minimum distance between the second pair of adjacent circumferential rings;   both of the first minimum distance and the second minimum distance are in the range of from about 0.0010 in to about 0.0250 in;   both of the first minimum distance and the second minimum distance are in the range of from about 0.0025 in to about 0.0190 in;   both of the first minimum distance and the second minimum distance are in the range of from about 0.0040 in to about 0.0150 in;   the first minimum distance is less than about 0.0250 in and the second minimum distance is greater than about 0.0010 in;   the first minimum distance is less than about 0.0190 in and the second minimum distance is greater than about 0.0025 in;   the first minimum distance is less than about 0.0150 in and the second minimum distance is greater than about 0.0040 in;   the endovascular prosthesis delivery device comprises a first pair of adjacent circumferential rings disposed in the distal porous portion and a second pair of circumferential rings disposed in the proximal porous surface, with the proviso that a first maximum distance between the first pair of adjacent circumferential rings is greater than a second maximum distance between the second pair of adjacent circumferential rings;   both of the first maximum distance and the second maximum distance are in the range of from about 0.0050 in to about 0.0400 in;   both of the first maximum distance and the second maximum distance are in the range of from about 0.0075 in to about 0.0365 in;   both of the first maximum distance and the second maximum distance are in the range of from about 0.0090 in to about 0.0330 in;   the first minimum distance is less than about 0.0400 in and the second minimum distance is greater than about 0.0050 in;   the first minimum distance is less than about 0.0365 in and the second minimum distance is greater than about 0.0075 in;   the first minimum distance is less than about 0.0330 in and the second minimum distance is greater than about 0.0090 in;   the endovascular prosthesis delivery device further comprises an endovascular prosthesis connection portion attached to the distal portion;   the endovascular prosthesis connection portion comprises at least one elongate section comprising an intermediate section and a distal section for connection to the endovascular prosthesis;   at least one of the intermediate section and the distal section are angled with respect to a longitudinal axis of the endovascular prosthesis delivery device;   both of the intermediate section and the distal section are angled with respect to a longitudinal axis of the endovascular prosthesis delivery device;   the intermediate section and the distal section are angled with respect to one another;   the endovascular prosthesis connection portion comprises a pair of elongate sections comprising a first elongate section and a second elongate section;   the first elongate section comprises an endovascular prosthesis first attachment portion disposed at a distal end thereof;   the endovascular prosthesis first attachment portion comprises a first half of a first male-female connection system for receiving a second half of the first male-female connection system disposed on an endovascular prosthesis;   the first half of the first male-female connection system comprises a first male portion;   the second half of the first male-female connection system comprises a first female portion;   the first half of the first male-female connection system comprises a first female portion;   the second half of the first male-female connection system comprises a first male portion;   the first half of the first male-female connection is configured to receive a first endovascular prosthesis detachment member;   the second half of the first male-female connection is configured to receive a first endovascular prosthesis detachment member;   the first half and the second half of the first male-female connection are configured to receive a first endovascular prosthesis detachment member;   the first endovascular prosthesis detachment member comprises a first wire member;   the second elongate section comprises an endovascular prosthesis second attachment portion disposed at a distal end thereof;   the endovascular prosthesis second attachment portion comprises a first half of a second male-female connection system for receiving a second half of the second male-female connection system disposed on an endovascular prosthesis;   the first half of the second male-female connection system comprises a second male portion;   the second half of the second male-female connection system comprises a second female portion;   the first half of the second male-female connection system comprises a second female portion;   the second half of the second male-female connection system comprises a second male portion;   the first half of the second male-female connection is configured to receive a second endovascular prosthesis detachment member;   the second half of the second male-female connection is configured to receive a second endovascular prosthesis detachment member;   the first half and the second half of the second male-female connection are configured to receive a second endovascular prosthesis detachment member;   the endovascular prosthesis detachment member comprises a wire member;   the first elongate portion has a greater longitudinal length than the second elongate portion;   the second elongate portion has a greater longitudinal length than the first elongate portion; and/or   the first elongate portion and the second elongate portion have a substantially equal longitudinal length.       

     With reference to  FIGS. 1-2 , there is illustrated an endovascular prosthesis  100 . Endovascular prosthesis  100  comprises an expandable portion  105 , a leaf portion  110  and a loop portion  115 . Expandable portion  105  comprises a pair of undulating circumferential rings  106 , 107  that are interconnected to one another by a pair of longitudinal struts  108 , 109 . 
     Leaf portion  110  comprises a spine portion  111  to which is connected a first row of rib portions  112  on one side thereof and a second row of rib portions  113  on an opposed side thereof. As can be seen, spine portion  111  comprises an undulating configuration (see also  FIG. 1 a    for an enlarged view of this feature). Individual ribs in each of rows  112 , 113  are connected to the peaks of the undulating pattern formed by spine portion  111 . This results in the connection points of individual rib portions in rows  112 , 113  being longitudinally offset with respect to one another. 
     The specifications for each rib portion in rows  112  and  113  are preferred to be those mentioned above. Loop portion  115  comprises a single loop portion  116 , the function of which will be described in more detail below. 
     Endovascular prosthesis  100  further comprises a series of radiopaque markers  120  disposed at various positions on prosthesis  100 . 
     Expansible portion  105  comprises a pair of loop portions  122 , 124  for connection to a delivery system (discussed below). 
     With reference to  FIG. 1 a   , there is illustrated an enlarged view of a portion of endovascular device  100 . The following is a concordance of terms used in  FIG. 1 a    (while the terms are illustrated with reference to endovascular device  100 , the also apply to endovascular devices  200 ,  300 ,  400 ,  500  and  600  described in more detail hereinbelow) and elsewhere in this specification: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 A 
                 root angle 
                 rib proximal portion acute angle 
               
               
                 B 
                 lead in angle 
                 rib intermediate first portion acute angle 
               
               
                 C 
                 rib angle 
                 rib intermediate second portion acute angle 
               
               
                 D 
                 tip angle 
                 rib distal portion acute angle 
               
               
                 W 
                 root width 
                 rib proximal portion 
               
               
                 X 
                 lead in width 
                 rib intermediate first portion 
               
               
                 Y 
                 rib width 
                 rib intermediate second portion 
               
               
                 Z 
                 tip width 
                 rib distal portion 
               
               
                   
               
            
           
         
       
     
     With reference to  FIG. 3 , endovascular prosthesis  100  is connected to a delivery device  130 . The details of delivery device  130  will be discussed in further detail below. For present purposes, delivery device  130  comprises at its distal end a pair of arms  135  (only one arm is shown in  FIG. 3 ). Each arm  135  of delivery device  130  is connected to loop portion  122  or  124  of expansible portion  105  as shown in  FIG. 3 . A delivery catheter  140  covers delivery device  130 . 
     With reference to  FIG. 4 , further details are provided on connection of delivery device  130  to endovascular prosthesis  100  and deployment of the latter. 
     Thus, delivery device  130  comprises a porous tube  132  at the distal portion of which may be found arms  135 . One arm  135  is connected to loop  122  of expansible portion  105  in a male-female arrangement while the other arm  135  is connected to loop portion  124  also in a male-female relationship. The connection between arms  135  and loop portions  122 , 124  is maintained as shown in  FIG. 4  by a pair of wires  137 . 
     As shown in  FIG. 4 , endovascular prosthesis  100  is delivered to a body passageway  10  (i.e., an artery) having an aneurysm  15  with an aneurysmal opening  17 . In the illustrated embodiment, endovascular prosthesis  100  is a so-called self-expanding device. This means that when sheath  140  is retracted, endovascular prosthesis  100  will expand to its deployed state. 
     In the illustrated embodiment, endovascular prosthesis  100  is positioned incorrectly with respect to aneurysm  15 , particularly the aneurysmal opening  17 . Specifically, the clinical goal is to have leaf portion  115  covering aneurysmal opening  17  of aneurysm  15 , ultimately leading to occlusion of aneurysm  15 . As shown in  FIG. 4 , the clinical goal has not been achieved. 
     One of the specific advantages of the present invention generally and the endovascular prosthesis specifically is that the prosthesis may be retracted into the sheath after it has been completely unsheathed and before it has been fully released and deployed. A device that is retracted and partially unsheathed is shown schematically in  FIGS. 5 and 6 , respectively. 
     Thus, in  FIG. 5  sheath  140  is extended to cover leaf portion  115  of endovascular prosthesis  100 . While, in the illustrated embodiment, loop portion  116  emanates from sheath  140  in  FIG. 5 , the entire device could be retracted into sheath  140 , if desired. The orientation and design of the rib portions in leaf portion  115  facilitate retraction of leaf portion  105  into sheath  140 , for example, by allowing crisscrossing of the distal portions of respective rib portions in rows  112 , 113 —this is a particularly advantageous feature of the present endovascular prosthesis generally. 
     As shown in  FIG. 5 , re-sheathing of endovascular prosthesis  100  is achieved by relative movement between endovascular prosthesis  100  and sheath  140  in the direction of arrow A. When it is desired to unsheath endovascular prosthesis  100  (for the first time or otherwise), sheath  140  is moved relative to endovascular prosthesis in the direction of arrow B as shown in  FIG. 6 . 
     The ability to sheath, unsheath, re-sheath, etc. endovascular prosthesis  100  as shown in  FIGS. 5 and 6  is a distinct advantage of the present endovascular prosthesis generally since it allows the clinician to optimize the position of leaf portion  115  relative to aneurysmal opening  17  of aneurysm  15 , even after endovascular prosthesis  100  has been partially or fully unsheathed. Furthermore, the sheathing, unsheathing, re-sheathing, etc. . . . feature also allows the clinician to evaluate the size (diameter and length) of the endovascular prosthesis relative to the patient anatomy and if the sizing is not satisfactory the clinician can fully remove the endovascular prosthesis and exchange it for a correctly sized device while maintaining the sheath in the patient at the target site. 
     The optimum position of endovascular prosthesis  100  is shown in  FIG. 7  wherein leaf portion  115  occludes aneurysmal opening  17  of aneurysm  15 . The term “occlude” is used in a broad sense and generally means leaf portion  115  covers aneurysmal opening  17  of aneurysm  15 . While not wishing to be bound by any theory or particular mode of action, it is believed that this action of leaf portion  115  creates a pressure drop between aneurysm  15  and the parent vessel which leads ultimately to occlusion and healing. Single loop  116  of loop portion  115  serves to improve apposition of leaf portion  110  in body passageway  10 . 
     Once endovascular prosthesis  100  is in the correct position (this may be confirmed by the clinical use of conventional radiography and observing the position of radioopaque markers  120  relative to the target anatomy), endovascular prosthesis  100  is released from delivery device  130 . This is achieved by retracting wires  137  (initial retraction is shown in  FIG. 7 ) which allows arms  135  of delivery device  130  to be released from loops  122 , 124  of expansible portion  105  of endovascular prosthesis  100 . Delivery device  130  and sheath  140  may then be withdrawn from the patient. Leaving the correctly deployed endovascular prosthesis  100  implanted as shown in  FIG. 8 . 
     With reference to  FIGS. 9 and 10 , there is illustrated an endovascular prosthesis  200 . Endovascular prosthesis  200  is similar to endovascular prosthesis  100  illustrated in  FIGS. 1-2  with the following exceptions:
         single closed loop  116  in loop portion  115  of endovascular prosthesis  100  has been replaced with a pair of split loop portions  216   a , 216   b;      the disposition of radioopaque markers  220  in endovascular prosthesis  200  differs from the disposition of radioopaque markers  120  in endovascular prosthesis  100 ;   the design of the individual ribs in leaf portion  210  of endovascular prosthesis  200  has been slightly modified with respect to the rib portions in leaf portion  110  of endovascular prosthesis  100 ;   the rib portions in rows  212 , 213  of endovascular prosthesis  200  are more closely spaced than in endovascular prosthesis  100 ; and   loops  222  and  224  have been modified for attachment to the delivery system.       

     The use of split loops  216   a , 216   b  provides improved apposition of endovascular prosthesis  200 . A single loop  116  as used in endovascular prosthesis  100  can protrude into the lumen of the artery if the single loop is oversized relative to the size of the artery. The provision of pair of split loops  216   a , 216   b  allows for overlap of each loop in a given pair while avoiding bending into the lumen of the artery. The addition of radiopaque markers in this embodiment facilitates visualization by the clinician of the location of the extremities of the endovascular prosthesis  200 . The provision of radiopaque markers  220  in expansible portion  205  as illustrated facilitates visualization of one end the end of prosthesis  200  while the provision of radiopaque markers  220  in loop portion  215  as illustrated facilitates visualization of one the other end of prosthesis  200 . 
     Furthermore, having two markers near the spine of the leaf and depicting the length of the occlusive length of leaf allows the clinician the ability to evaluate whether or not the leaf length relative to the aneurismal opening  17  is adequate. 
     As can be seen, loop  222  comprises a pair of apertures  222   a , 222   b . Similarly, loop  224  comprises a pair of apertures  224   a , 224   b.    
     With reference to  FIG. 11 , endovascular prosthesis  200  is attached to a delivery device  230 . As can be seen, delivery device  230  comprises a porous tube  232 . A pair of arms  235  is provided at the distal end of porous tube  232 .  FIG. 12( a )  provides an enlarged view of region C of  FIG. 11 . As can be seen, each arm  235  has a pair of apertures  235   a , 235   b . Aperture  235   a  of arm  235  is aligned with aperture  222   a  or  224   a  of loops  222  or  224 , respectively. Similarly, aperture  235   b  is aligned with apertures  222   b  or  224   b  of loops  222  or  224 , respectively. A loop wire  240  is then passed through these aligned loops to create a pair of wire loops  241 . Loop wire  240  may be a single wire for each of arms  235  or it may be a pair of independent wires. A release wire  245  is then fed through loops  241 . This can be seen more clearly with reference to  FIG. 12( b )  which illustrates the arrangement of loop wire  240  and release wire  245  without the detail of endovascular prosthesis  200  or delivery device  230 .  FIG. 12( c )  shows the orientation of loop wire  240  on its own. 
     Endovascular prosthesis  200  may be navigated to an aneurysm in the same manner as described above with reference to endovascular prosthesis  100 . Thus, endovascular prosthesis  200  also has a beneficial feature of being able to be sheathed, unsheathed, re-sheathed, etc. as was the case for endovascular prosthesis  100 . 
     When endovascular prosthesis  200  is positioned correctly. It can be detached from delivery device  230  by sequentially retracting release wire  245  and then retracting loop wire  240 . As will be appreciated by those of skill in the art, once release wire  245  is retracted, loops  241  are free to be retracted from the apertures in loops  222 , 224  and the apertures in arms  235 . Once loops  241  have been retracted in this manner, endovascular prosthesis  200  will detach from arms  235  of delivery device  230 . 
     With reference to  FIGS. 13 and 14 , there is illustrated an endovascular prosthesis  300 . Endovascular prosthesis  300  is similar to endovascular prosthesis  200  described above with the exception that expansible portion  305  has been modified. Specifically, expansible portion  305  comprises an anchor spine  306  with a series of anchor ribs  307  disposed on opposite sides of anchor spine  306 . 
     The other modification made to endovascular prosthesis  300  is the provision of a single loop  322  comprising a pair of apertures  322   a , 322   b  for connection to a delivery device. 
     The advantages of endovascular prosthesis  300  compared with endovascular prosthesis  200  include:
         a single attachment connection between the prosthesis and the delivery device compared to two connections for endovascular prosthesis  200  (and endovascular prosthesis  100 ); and   addition of radioopaque markers near the rib tips near the middle of the leaf portion, which are generally circumferentially orthogonal to the markers close to the spine portion of the leaf portion—these circumferentially orthogonal markers help the clinician to evaluate the rotational position of the device radiographically.       

     With particular reference to  FIGS. 14 and 15 , there is illustrated endovascular prosthesis device  300  connected to a delivery device  330  having a porous tube  332 . Disposed at the end of porous tube  332  is a single arm  335 . Arm  335  comprises a pair of apertures that, during manufacture, can be aligned with apertures  322   a , 322   b  of loop  322  of endovascular prosthesis  300 . After these apertures are aligned during manufacturing, a single loop/release wire  345  is fed through the aligned apertures to provide a pair of loops  341 . The same loop/release wire  345  is then fed back on itself through loops  341  as shown in  FIGS. 15( a ), ( b ), ( c ) and ( d )  which provide various details of how single loop/release wire  345  is positioned. As shown, the end of single loop/release wire  345  is permanently affixed to arm  335 . 
     Endovascular prosthesis  300  may be delivered to a target aneurysm in the same manner as described above with reference to endovascular prosthesis  100  and endovascular prosthesis  200 . Once endovascular prosthesis is in the correct position, it may be detached from delivery device  330  by retracting loop/release wire  345 . Initial retraction of loop/release wire  345  removes it from loops  341 . Continued retraction of loop/release wire  345  removes loops  341  from aligned apertures in loop  322  of endovascular prosthesis  300  and arm  335  of delivery device  330 . At this point, delivery device  330  may be withdrawn leaving endovascular prosthesis  300  in place. 
     The endovascular prosthesis described above with reference to  FIGS. 1-15  is particularly well suited for occlusion of a so-called sidewall aneurysm. Occasionally, the target aneurysm is located at an intersection of a bifurcated artery such as the distal basilar artery described above—such a target aneurysm is generally more difficult to treat than a sidewall aneurysm. For treatment of such a target aneurysm, it is preferred to further modify the endovascular prosthesis described above with reference to  FIG. 115 . 
     Thus, with reference to  FIGS. 16-17 , there is illustrated an endovascular prosthesis  400  that is particularly well suited for treatment of an aneurysm located in a bifurcated artery. As can be seen, endovascular prosthesis  400  is similar to endovascular prosthesis  100  described above with reference to  FIGS. 1-2  with the following modifications:
         expansible portion  405  (including circumferential rings  406 , 407  and struts  408 , 409 ) have been translated to the opposite end of the spine  411  so that spine  411  is connected to a peak of circumferential ring  406  (cf. spine  111  in endovascular prosthesis  100  which is connected to a valley of circumferential ring  106 )—this feature facilitates delivery of endovascular prosthesis  400  into either a straight or bifurcated body passageway;   detachment loops  422 , 424  are located on opposed ends of endovascular prosthesis  400  (cf. loops  122 , 124  located on expansible portion  105  of endovascular prosthesis  100 );   there is no loop portion in the proximal end of endovascular prosthesis  400  as there is an endovascular prosthesis  100  (cf. loop portion  115 ); and   a single attachment portion  424  is provided at a proximal end of spine  411  of endovascular prosthesis  400 .       

     With reference to  FIGS. 18-21 , there is illustrated delivery and deployment of endovascular prosthesis  400  in a bifurcated artery  50 . As can be seen, bifurcated artery  50  comprises an aneurysm  55  having an aneurysmal opening  57 . 
     Of particular note in  FIGS. 18-21  is the general manner in which endovascular prosthesis is oriented during delivery and deployment. Specifically, when any of endovascular prosthesis  100 , 200 , 300  described above is delivered to a sidewall aneurysm, delivery is accomplished by orienting the expansible portion ( 105 , 205 , 305 ) such that it is proximal to the clinician whereas the loop portion ( 115 , 215 , 315 ) is oriented distally with respect to the clinician thus exiting delivery catheter  440  first. In contrast, when delivering endovascular prosthesis  400  to bifurcated artery  50 , expansible portion  405  is oriented distally with respect to the clinician whereas loop  424  (at the opposed end of endovascular prosthesis with respect to expansible portion  405 ) is oriented proximally with respect to the clinician thus exiting delivery catheter  440  last. 
     With reference to  FIG. 18( a ) , a guidewire  66  is inserted and passed through a first branch  51  of bifurcated artery  50 . Next, with reference to  FIG. 18( b ) , delivery catheter/sheath  440  is passed over guidewire  66  into first branch  51  of bifurcated artery  50 . 
     Next, with reference to  FIG. 18( c ) , guidewire  66  is withdrawn from first branch  51  of bifurcated artery  50 . With reference to  FIG. 18( d )  endovascular prosthesis  400  attached to delivery device  430  is fed through delivery catheter/sheath  440  until endovascular prosthesis  400  is positioned in first branch  51  of bifurcated artery  50 . 
     With reference to  FIG. 18( e )  delivery catheter/sheath  440  is thereafter retracted: this results in initial deployment of expansible portion  405  of endovascular prosthesis  400 . If the physician is not satisfied with this initial deployment of expansible portion  405  of endovascular prosthesis  400 , he/she may re-sheath endovascular prosthesis  400  in an attempt to reposition it within first branch  51  of bifurcated artery  50 . 
     Once the physician is satisfied with the initial deployment of endovascular prosthesis  400 , delivery catheter/sheath  440  is further retracted exposing the proximal portion of endovascular prosthesis  400 —see  FIG. 18( f ) . 
     With reference to  FIG. 19 , delivery device  430  is further extended as shown in  FIG. 19 . This further extension naturally progresses into a second branch  52  of bifurcated artery  50  due to the initial deployment of endovascular prosthesis  400 . 
     Once it has been determined that endovascular prosthesis  400  is in the correct position, delivery device  430  is detached from endovascular prosthesis  400  in the manner to be discussed below. This allows for withdrawal of delivery catheter  440  and delivery device  430  resulting in final deployment of endovascular prosthesis  400  as shown in  FIG. 21 . In this final deployed configuration, leaf portion  410  of endovascular prosthesis  400  occludes aneurysmal opening  57  of aneurysm  55 . 
     With reference to  FIG. 25 , there is illustrated a delivery device  430  for delivery of endovascular prosthesis  400 . Delivery device  430  comprises a porous surface  432  similar to the one described above with reference to endovascular prosthesis  100 , 200 , 300 . Delivery device  430  further comprises a first arm  435  having a square aperture  437  and a second arm  442  having a cleat/buckle attachment  445 . Cleat/buckle attachment  445  comprises a finger portion  447  having an aperture  448 . Finger portion  447  is movable with respect to a protector portion  449  of cleat/buckle attachment  445 . Protector portion  449  of cleat/buckle attachment  445  protects against snagging of loop  424  during retraction of endovascular prosthesis  400 . 
     With reference to  FIGS. 22-24 , there is illustrated further detail on attachment of arm  435  of delivery device  430  to loop portion  424  of expansible portion  405  of endovascular prosthesis  400 . Thus, loop portion  424  is inserted in square aperture  437  and a wire  438  is inserted through loop portion  424  so as to secure loop portion  424  with respect to square aperture  437 —see  FIG. 22 . Once endovascular prosthesis is in the correct position and the clinician desires to detach delivery device  430  from endovascular prosthesis  400 , wire  438  is retracted as shown in  FIG. 23 . This allows arm  435  to be separated from loop portion  424  of endovascular prosthesis  400  as shown in  FIG. 24 . 
     With reference to  FIGS. 26 and 27 , there is illustrated further detail of attachment of attachment portion  422  of endovascular prosthesis  400  to cleat/buckle attachment  445  of arm  442  of delivery device  430 —for ease of understanding the illustration has been styled outside the vasculature (cf.  FIG. 20 ). Thus, finger portion  447  of cleat/buckle attachment  445  is inserted in a first aperture  426  of attachment portion  422 . A wire  428  is inserted through a second aperture  429  of attachment portion  422  such that it also passes through aperture portion  448  of finger portion  447  of cleat buckle attachment  445 —see  FIG. 27 . This arrangement serves to secure attachment portion  422  of endovascular prosthesis  400  with respect to cleat/buckle attachment  445  of delivery device  430 . 
     When endovascular prosthesis  400  is in the correct position and the clinician wishes to detach endovascular prosthesis  400  from delivery device  430 , the clinician retracts wire  428  from apertures  429 , 448 . This allows finger portion  447  to be able to be retracted from aperture  426  of attachment portion  422  thereby allowing detachment of that portion of endovascular prosthesis  400  from delivery device  430 . 
     At this point, delivery device  430  is detached from endovascular prosthesis  400  and the former may be fully retracted from the patient through delivery catheter/sheath  440  as shown in  FIG. 20 . The final deployment of endovascular prosthesis  400  is illustrated in  FIG. 21 . 
     With reference to  FIGS. 28-35 , there is illustrated an endovascular prosthesis  500  that is particularly well suited for treatment of an aneurysm located in a bifurcated artery. As can be seen, endovascular prosthesis  500  is similar to endovascular prosthesis  400  described above with reference to  FIGS. 16-17  with the following general modifications:
         the provision of arms  519 ;   the single radioopaque marker  420  in endovascular prosthesis  400  has been replaced by a trio of radioopaque markers  520   a , 520   b , 520   c;      the arrangement of radioopaque markers  520  in the rows  512 , 513  of rib portions has been altered;   single attachment portion  424  provided at the end of spine  411  of endovascular prosthesis  400  has been replaced by a pair of arms  519  at the end of which is an attachment portion  524  comprising a pair of apertures  526 , 529 .       

     A number of technical effects accrue from these modifications. The additional radiopaque markers provide the clinician with information about the location in the patient of the proximal and distal extremities of the endovascular prosthesis  500 . In endovascular prosthesis  400 , the radioopaque markers were disposed along the same side of the spine portion of the prosthesis. In contrast, in endovascular prosthesis  500 , the radioopaque markers alternate along the spine portion and the most proximal radioopaque marker is centred with the spine. Pair of arms  519  in endovascular prosthesis  500  serve to urge the spine and rib portions toward the aneurysmal opening and provide support to the spine and rib portions to urge them against the artery wall. Furthermore, pair of arms  519  replace the function of second arm  442  of the delivery device used in endovascular prosthesis  400 . 
     With reference to  FIGS. 30-35 , there is illustrated attachment of endovascular prosthesis  500  to a delivery device  530  which is similar to delivery device  430  described above. One difference is that first arm  435  of delivery device  430  has been replaced with a first wire portion  535  which is fed into loop portion  524  of expansible portion  505 . A wire  538  is fed through wire portion  535  as shown in  FIG. 30  which illustrates attachment of delivery device  530  to expansible portion  505 . When it is desired to detach wire portion  535  form expansible portion  505 , wire  538  is retracted which allows wire portion  535  to disengage from loop portion  524  of expansible portion  505 —see  FIGS. 31 and 32 . 
     With reference to  FIG. 33 , there is shown additional detail on delivery device  530 . In essence, arms  435 , 442  used in endovascular prosthesis  400  have been omitted. Specifically, arm  435  has been replaced with wire portion  535  and arm  442  has been omitted and replaced with a pair of arms  519  in endovascular prosthesis  500 —see  FIG. 34 . The function of arm  442  is replaced by the presence of arms  519  in endovascular prosthesis  500  with the added advantage that the curvature in arms  519  in endovascular prosthesis  500  aid in correct placement of endovascular prosthesis  500  in a bifurcated artery. 
     As shown, delivery device  530  comprises an attachment portion  542  which is aligned with apertures  526 , 529  of arms  519  of endovascular prosthesis  500  and secured as a unit by a loop wire  548  and a release wire  528 . As shown in  FIG. 34 , arms  519  of endovascular prosthesis  500  are aligned such that respective apertures  526 , 529  of each arm  519  are aligned. Loop wire  548  is passed through attachment portion  542  of delivery device  530 . A retraction wire  528  is passed through loop wire  548  as shown in  FIG. 34  and also as shown in  FIG. 35 . 
     Endovascular prosthesis  500  may be delivered using delivery device  530  in a manner similar to that described above in  FIGS. 18-21  with reference to endovascular prosthesis  400 . 
     With the reference to  FIGS. 36 and 37 , there is illustrated an endovascular prosthesis  600  that is particularly well suited for treatment of aneurysm located in a bifurcated artery. As can be seen, endovascular prosthesis  600  is similar to endovascular prosthesis  500  described above with reference to  FIGS. 28 and 29  with the following general modifications:
         pair of arms  519  in endovascular prosthesis  500  have been replaced with a quartet of arms  619 ;   radioopaque markers  620  are arranged differently in endovascular prosthesis  600  then radioopaque markers  520   a , 520   b , 520   c , 520  in endovascular prosthesis  500 ;   longitudinal strut  509  has been deleted thereby resulting in element  606 , 607  being noncircumferential extending (they may be regarded as so-called “split loops”); and   an element corresponding to attachment point  522  does not exist on endovascular prosthesis  600 , because the “expansible portion” has been replaced with ribs or split loops and as such, no longer requires an attachment point.       

     One of the principle advantages of endovascular prosthesis  600  is that it may be delivered with a delivery device  630  which consists of a single attachment to endovascular prosthesis  600 . The provision of arms  619  will improve urging of the spine portion and rib portions against the aneurysmal opening and against the artery wall. This is particularly advantageous since it allows for implantation of endovascular prosthesis in more varied anatomy than endovascular prosthesis  500 . If endovascular prosthesis  600  is oversized relative to the target artery, arms  619  will remain against the artery wall and overlap each other, whereas in endovascular prosthesis  500 , arms  519  may encroach into the lumen of the artery if the prosthesis were oversized. Similar advantage accrues with reference to elements  606  and  607 . Finally, there are radioopaque markers disposed on both sides of the spine portion in endovascular prosthesis  600  compared to the alternating arrangement used in endovascular prosthesis  500 —this provides a more detailed description of the leaf spine radiographically which allows for optimal positioning with respect to the aneurysmal opening. 
       FIG. 37  illustrates connection of endovascular prosthesis  600  to delivery device  630 . Specifically, attachment portion  622  of endovascular prosthesis  600  is aligned with an attachment portion  632  of delivery device  630 . While the details of connecting endovascular prosthesis  600  to delivery device  630  are not illustrated in  FIG. 37 , it is preferred to utilize a single loop/release wire as described above with reference to  FIGS. 14 and 15  with the proviso that loops  341  are inverted when connecting endovascular prosthesis  600  to delivery device  630 . 
     With reference to  FIGS. 38( i ) - 38 ( iii ), there are illustrated various views of the distal portion of a endovascular prosthesis delivery device  5 . The illustrated distal portion has a porous surface. The remainder of the endovascular prosthesis delivery device (not shown for clarity) is substantially non-porous. 
     As illustrated, there is an overall increase in porosity of the porous surface of the endovascular prosthesis delivery device  5  moving from a proximal portion of the porous surface to the distal portion of the porous surface (left to right in  FIGS. 38( i ) -( iii )). 
     The present inventors have discovered that a combination of specific dimensions of the porous surface is particularly useful in conferring a highly desirable balance between longitudinal flexibility and sufficient structural integrity (re. torquing ability) to facilitate delivery of an endovascular prosthesis, particularly through tortuous vasculature. 
     Specifically, with particular reference to  FIGS. 38( a ) and 38( b ) , a functional advantage accruing from a porous surface having the combination of dimensions if it allows for bending of a longitudinal strut  10  in the porous surface until the amount of bending allows for edges  20  of adjacent circumferential rings  25  to contact each other, at which point no further bending (strain) can be applied to longitudinal strut  10 . Consequently, there is a limit on the amount of strain that can be placed on longitudinal strut  10 , thereby reducing the likelihood of kinking, yield and/or failure of the material used to produce the porous surface of endovascular prosthesis delivery device  5 . 
     With reference to  FIGS. 38( a )-38( d ) , the dimensions for elements O, P, Q and R appearing in those drawings denote the concurrent transition for all of these elements from one end of the device to the other end: 
     
       
         
           
               
               
            
               
                   
                   
               
               
                   
                 Dimension (in.) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 O 
                 P 
                 Q 
                 R 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Preferred 
                 0.0250-0.0010 
                 0.0010-0.0450 
                 0.0400-0.0050 
                 0.0010-0.0500 
               
               
                 More preferred 
                 0.0190-0.0025 
                 0.0040-0.0325 
                 0.0365-0.0075 
                 0.0035-0.0300 
               
               
                 Most preferred 
                 0.0150-0.0040 
                 0.0050-0.0250 
                 0.0330-0.0090 
                 0.0045-0.0150 
               
               
                   
               
            
           
         
       
     
     The number of transitions in elements O, P, Q and R is not particularly restricted. For example, in  FIG. 38 , there is a transition between circumferentially adjacent longitudinal struts (R) and longitudinally adjacent circumferential rings P. However, the transition may achieved using fewer steps—e.g., by having sub-sections with constant dimensions for O, P, Q and R. In this latter embodiment, the sub-sections may be of similar or dissimilar longitudinal length. It is also possible to use a combination of one or more sub-sections with a series of individual transitions. 
     The embodiment of the delivery device shown in  FIG. 38  preferably has a diameter less than that of delivery catheter  140 , 440 . Preferably, the delivery device has a in the range of from about 0.015 to about 0.035 inches, more preferably from about 0.020 to about 0.030 inches, most preferably 0.025 inch. 
     Endovascular prosthesis delivery device  5  is particularly well suited for delivery of the present endovascular prosthesis particularly when it is desired to deliver that prosthesis through torturous vasculature in a patient. Of course, it will be appreciated that endovascular prosthesis delivery device  5  can be used to deliver other types of endovascular prostheses. 
       FIGS. 38-43  illustrate enlarged views of the distal portions of the various delivery devices described above identified with reference numerals ending in “30”. The following is a concordance of the above-described delivery devices and the above-described endovascular prosthesis preferably delivered by that delivery device: 
                                         Delivery   Endovascular       Figure   Device   Prosthesis                  38   130   100       39(a)-(d)   230   200       40(a)-(d)   330   300       41   430   400       42(a)-(c)   530   500       43(a)-(e)   630   600                    
As can be seen in  FIGS. 39-43 , the porous, tubular portion of each delivery device is very similar but the distal section which is used to attach to the endovascular prosthesis is varied in each embodiment to accommodate the specific type of endovascular prosthesis. In Figures, the distal section which is used to attach the endovascular prosthesis is heat set (e.g., in when the delivery device is constructed from a shape memory alloy such as nitinol) to facilitate delivery of the endovascular prosthesis—this is particularly advantageous when it is desired to deliver the endovascular prosthesis to a bifurcated artery. The point is, a person of ordinary skill in the art, having in hand the present specification will understand that the specific nature of the distal section which is used to attach to the endovascular prosthesis is not specifically restricted. Further, a person of ordinary skill in the art will understand, having this specification in hand, that it may be possible to mix and match certain illustrated embodiments of the endovascular prosthesis with certain illustrated embodiments of the endovascular prosthesis delivery device with or without minor modifications to one or both of these.
 
     In a highly preferred embodiment, the present endovascular prosthesis delivery device also is provided with a cover layer on the porous surface thereof. The cover layer may be disposed on one or both of the inner and outer surfaces of the porous surface of the endovascular prosthesis delivery device. The provision of such a cover layer has been found to obviate or mitigate friction between the endovascular prosthesis delivery device and the interior of the deliver catheter conventionally used to deliver the endovascular prosthesis. Preferably, the cover layer is a made from a biocompatible polymer which can be a natural or a synthetic polymer. Non-limiting examples of a suitable polymer may be selected from the group comprising polyurethanes, silicone materials, polyurethane/silicone combinations, rubber materials, woven and non-woven fabrics such as Dacron, fluoropolymer compositions such as a polytetrafluoroethylene (PTFE) materials, expanded PTFE materials (ePTFE) such as and including Teflon™, Gore-Tex™, Softform™ Impra™ and the like. Preferably, the cover layer has a thickness in the range of from about 0.00025 to about 0.00100 inches, more preferably the cover layer has a thickness of about 0.00050 inches. 
     The endovascular prosthesis of the present invention may further comprise a coating material thereon. The coating material can be disposed continuously or discontinuously on the surface of the prosthesis. Further, the coating may be disposed on the interior and/or the exterior surface(s) of the prosthesis. The coating material can be one or more of a biologically inert material (e.g., to reduce the thrombogenicity of the stent), a medicinal composition which leaches into the wall of the body passageway after implantation (e.g., to provide anticoagulant action, to deliver a pharmaceutical to the body passageway and the like), an expansible/swellable material (e.g., a hydrogel material) and the like. 
     Further, the present endovascular prosthesis may be provided with a biocompatible coating, in order of minimize adverse interaction with the walls of the body vessel and/or with the liquid, usually blood, flowing through the vessel. A number of such coatings are known in the art. The coating is preferably a polymeric material, which is generally provided by applying to the stent a solution or dispersion of preformed polymer in a solvent and removing the solvent. Non-polymeric coating material may alternatively be used. Suitable coating materials, for instance polymers, may be polytetrafluroethylene or silicone rubbers, or polyurethanes which are known to be biocompatible. Preferably however the polymer has zwitterionic pendant groups, generally ammonium phosphate ester groups, for instance phosphorylcholine groups or analogues thereof. 
     Examples of suitable polymers are described in International Publication Numbers WO-A-93/16479 and WO-A-93/15775. Polymers described in those documents are hemocompatible as well as generally biocompatible and, in addition, are lubricious. When such coatings are used, it is preferred that the surfaces of the endovascular prosthesis are completely coated in order to minimize unfavourable interactions, for instance with blood, which might lead to thrombosis. This good coating can be achieved by suitable selection of coating conditions, such as coating solution viscosity, coating technique and/or solvent removal step. 
     The manner by which the present endovascular prosthesis is manufactured is not particularly restricted. Preferably, the endovascular prosthesis is produced by laser cutting or chemical etching techniques applied to a tubular starting material. Thus, the starting material could be a thin tube of a metal or alloy (non-limiting examples include stainless steel, titanium, tantalum, nitinol, Elgiloy, NP35N, cobalt-chromium alloy and mixtures thereof) which would then have sections thereof cut out (by laser cutting or chemical etching) to provide a prosthesis having a pre-determined design. Alternatively, it is possible to cut the design (by laser cutting or chemical etching) of the prosthesis from a flat starting material and thereafter roll the cut product into a tube and heat set in such a configuration or the edges of which could be welded or otherwise secured together to form a tubular device. 
     In a particularly preferred embodiment, the present endovascular prosthesis is made from a suitable material which will expand when a certain temperature is reached. In this embodiment, the material may be a metal alloy (e.g., nitinol) capable of self-expansion at a temperature of at least about 25° C., preferably in the range of from about 25° C. to about 35° C. In this preferred embodiment, it may be desired and even preferable to heat set the endovascular prosthesis to adopt a deployed configuration which has been optimized for the particular intended anatomy—e.g., this is preferred for endovascular prosthesis  400 , 500 , 600  described above. 
     While this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Thus, various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. For example, the illustrated embodiments all utilize the leaf portion to act as a so-called flow diverter—i.e., once the device is implanted, the leaf portion diverts blood flow away from entering the aneurysmal opening. In cases where the aneurysmal opening is relatively large, it is possible to modify the leaf portion to act as a retention member—e.g., to retain one or more Guglielmi Detachable Coils in the aneurysm. In this modification, the spacing between adjacent rib portions would be increased a sufficient degree to allow delivery of one or more Guglielmi Detachable Coils through the leaf portion after implantation of the endovascular prosthesis. The Guglielmi Detachable Coils would be less likely to “fall out” of the aneurysm when the leaf portion of the present endovascular prosthesis is covering the aneurysmal opening. Further, while the illustrated embodiments depict attaching the endovascular prosthesis to the endovascular prosthesis delivery device using release wire/loop wire systems with or without male-female connection systems, other approaches may also be used—e.g., electrolytic, thermal-mechanical, other mechanical and similar approaches may be adopted. Further, while the illustrated embodiments are focussed on treatment of a cerebral aneurysm, it is contemplated that the present endovascular prosthesis may be used to treat other diseases such as aortic disease (e.g., see the discussion of aortic disease set out in International Publication Number WO 02/39924 [Erbel et al.]). In this modification, it may be appropriate to alter various of the above-mentioned dimensions. For example, It is therefore contemplated that the appended claims will cover any such modifications or embodiments. 
     All publications, patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.