CA2358449A1 - Expandable intravascular tubular stents - Google Patents
Expandable intravascular tubular stents Download PDFInfo
- Publication number
- CA2358449A1 CA2358449A1 CA002358449A CA2358449A CA2358449A1 CA 2358449 A1 CA2358449 A1 CA 2358449A1 CA 002358449 A CA002358449 A CA 002358449A CA 2358449 A CA2358449 A CA 2358449A CA 2358449 A1 CA2358449 A1 CA 2358449A1
- Authority
- CA
- Canada
- Prior art keywords
- stent
- stmt
- tubular stent
- adjacent
- intravascular
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Landscapes
- Media Introduction/Drainage Providing Device (AREA)
Abstract
An expandable intravascular medical tubular stent (140) is a supporting devi ce intended to maintain the walls of anatomical body channels or vessels, the stent being expandable within the vessel by an angioplasty balloon associate d with a catheter thereby dilating and expanding the lumen of a vessel. The stent (140) comprises an arrangement of a plurality of radially expandable, serpentine members (16) arranged in interconnected rings. Upon inflation of the balloon, the stent expands in both radial and longitudinal directions in relation to the amount of radially-outwardly directed force by the balloon. The stent is designed such that during expansion, the longitudinal length of the stent is not substantially affected.
Description
EXPANDABLE INTRAVASCULAR TUBULAR STENTS
BACKGROUND OF THE INVENTION
Following an angioplasty procedure, the restenosis rate of stented vessels has proven significantly lower than for unstented or otherwise treated vessels, which treatments include drug therapy and other surgical procedures.
The intravascular stmt functions as scaffolding for the lumen of a vessel. The scaffolding of the vessel walls by the stmt serves to: (a) prevent elastic recoil of the dilated vessel wall;
(b) eliminate residual stenosis of the vessel, a common occurrence in balloon angioplasty procedures; (c) maintain the diameter of the stented vessel segment slightly larger than the native unobstructed vessel segments adjacent the stented segment; and (d) as indicated by the latest clinical data, lower the restenosis rate.
The conventional stmt designs suffer in varying degrees from a variety of drawbacks 1 ~ including: (a) the inability to negotiate bends in vessels due to columnar rigidity of the unexpended stent; (b) the lack of structural strength, both radial and bending, of the unexpended stent; (c) significant foreshortening of the stmt during expansion;
(d) limited stmt length; (e) constant expanded stmt diameter; (fJ poor crimping characteristics; and (g) rough surface modulation of the unexpended stent.
Although many stems are made of wire which is wound and bent into desired configurations, stems may also be formed using thin-walled tubes that are laser cut, or otherwise formed to allow the tubes to be compressed into a smaller diameter for delivery to a desired location within a body lumen. Such stents, commonly referred to as tubular stems, provide advantages in terms of increased torsional stability and hoop strength as compared to stems formed from wires. One disadvantage, however, is that tubular stems typically exhibit limited longitudinal flexibility which can limit delivery through tortuous pathways and their deployment in cmroed body lumens.
BACKGROUND OF THE INVENTION
Following an angioplasty procedure, the restenosis rate of stented vessels has proven significantly lower than for unstented or otherwise treated vessels, which treatments include drug therapy and other surgical procedures.
The intravascular stmt functions as scaffolding for the lumen of a vessel. The scaffolding of the vessel walls by the stmt serves to: (a) prevent elastic recoil of the dilated vessel wall;
(b) eliminate residual stenosis of the vessel, a common occurrence in balloon angioplasty procedures; (c) maintain the diameter of the stented vessel segment slightly larger than the native unobstructed vessel segments adjacent the stented segment; and (d) as indicated by the latest clinical data, lower the restenosis rate.
The conventional stmt designs suffer in varying degrees from a variety of drawbacks 1 ~ including: (a) the inability to negotiate bends in vessels due to columnar rigidity of the unexpended stent; (b) the lack of structural strength, both radial and bending, of the unexpended stent; (c) significant foreshortening of the stmt during expansion;
(d) limited stmt length; (e) constant expanded stmt diameter; (fJ poor crimping characteristics; and (g) rough surface modulation of the unexpended stent.
Although many stems are made of wire which is wound and bent into desired configurations, stems may also be formed using thin-walled tubes that are laser cut, or otherwise formed to allow the tubes to be compressed into a smaller diameter for delivery to a desired location within a body lumen. Such stents, commonly referred to as tubular stems, provide advantages in terms of increased torsional stability and hoop strength as compared to stems formed from wires. One disadvantage, however, is that tubular stems typically exhibit limited longitudinal flexibility which can limit delivery through tortuous pathways and their deployment in cmroed body lumens.
As a result, a need exists for a stmt that provides the longitudinal flexibility associated with wire-wound stems in combination with the hoop strength and torsional stability of a tubular stmt.
A review article, Does Stent Design Influence Restenosis?, by Dr. J. Gunn published in the European Heart Journal July 1999 (Vol. 20, issuel4), stated that unlike restenosis after balloon angioplasty, the in-stmt restenosis consists predominantly of neointimal growth rather than the combination of neointima, recoil and downsize remodelling seen after the balloon angioplasty. The degree of restenosis is related to the extent of damage done at the time of implantation. The composition of the neointima of in-stmt restenosis is similar to that seen in balloon angioplasty, and includes vascular smooth muscle cells and inter-cellular matrix.
Any subtle differences in the composition of the neointima of the in-stmt restenosis and post -balloon injury, for example a suggestion of more matrix relatives to cell in the former, may be explained by the different nature and time-course of the two injuries: stmt struts produce local deep trauma, and the stmt as a whole produces chronic stretch; whereas balloon injury, which may also be deep, is transient an tends to be focal, with unilateral dissection rather than circumferential stretch. There is clinical evidence that the stmt geometry influences in-stmt restenosis. One widespread perception is that tissue prolapse at the central articulation of the Palmaz-Schatz stmt (U.S. Patent No. 5,382,261 to Palmaz dated January 17, 1995) increases in-stmt restenosis at that site. Intravascular ultrasound has also revealed that in-stmt restenosis within coil-stems is related to recoil, whereas in-stmt restenosis within slotted tube stems is related to sub-expansion. In a retrospective study of matched lesion, the flexible Micro StentTM from Arterial Vascular Engineering, Inc. of Santa Rosa, California., was associated with a higher restenosis rate than the more rigid Palmaz-Schatz stmt. Similarly, a coil-stmt has been shown to be associated with increased in-stmt restenosis compared with a slotted tube stmt in chronic total occlusions, a situation where radial strength is probably paramount.
In one systematic study, where the features of stmt geometry which make one stmt superior to another were investigated, changing the stmt configuration to reduce strut-strut intersections reduced the vascular injury score by 42%, thrombosis by 69% and neointimal hyperplasia by 38%. Coating with an inert polymer did not alter vascular injury or neointimal hyperplasia, although thrombosis was eliminated. Uniform (modest oversize) deployment of multiple examples of one design of stmt in normal porcine coronary artery, with many sections analysed at a consistent time point, allows precise mathematical analysis of the relationship between as many parameters of the stmt geometry as are thought useful in in-stmt restenosis.
Using this technique, extreme strut protrusion, large inter-strut distance, fracture ofthe internal elastic lamina, medial compression and location near the distal ends of the stmt have been identified as of particular importance. There was no direct relationship found between the number of struts and in-stmt restenosis unless the stmt was over-deployed, in which case more struts were advantageous, presumably distributing the forces of stretch more evenly and preventing isolated strut protrusion. In the same study, there was great lumen loss and neointimal growth at the distal end compared with the middle of the stems, possibly reflecting the taper seen in a porcine artery. There was suggestion that eccentricity of the stmt deployment (oblateness of the cross-section) adversely affected in-stmt restenosis. There is clinical intravascular ultrasound-based evidence for this, too. In one study, deviation from the circular in a stented vessel is associated with a trend towards increased target vessel revascularization at long-term follow-up. In contrast to the early days of stenting, when the fear of a "foreign body" reaction was still present, results such as this now point away from a minimalist approach towards generous coverage of the wounded vessel wall, with a high metal/artery ratio. The concept of maximizing the metal barrier is, of course, limited by poor "crimpability", unacceptable profile and inflexibility. Such designs (for example, the Jomed covered stmt made by Jomed Implantate GmbH of Rangendingen, DE) are already marketed, but have not yet reached wide acceptance.
Deployment strategies are also likely to affect the long-term result of stenting. Finite element analysis has revealed that low balloon compliance and the lowest possible balloon pressure to achieve adequate deployment are important variables. Balloon -(and stmt)-artery ratio (BAR) are also contributory. In his early studies, Schwartz ( J Am Coll Cardol 1992;19:267-274) used a BAR of 1.5:1, and produced dramatic injury with a high experimental animal mortality rate. Thomas (Jlnvas Cardiol 1997;9:453-460) , however, using a BAR of 1.1: l, experienced 100% patency and minimal neointima. In trying to draw any conclusion from the data available about the "ideal" stmt, a pattern is starting to emerge. Whilst preserving the desirable characteristics of low profile, trackability, conformability and visibility, a stmt should have many, closely spaced struts giving good, well-distributed radial strength. The inter-strut connections, whilst allowing for even balloon expansion and access to side-branches, should form a close meshwork which prevents large spaces from opening up between the struts, or from one strut protruding radially beyond its neighbours. The forces for expansion should be distributed evenly so that the stmt expands symmetrically, without eccentrity. Attention should be paid to the design of the ends of the stmt, so that a smooth transition to normal vessel is created, and distal oversizing is avoided. The design should preclude the development of large defects in metal coverage. Sizing of the stmt relative to the normal "reference" segment should not be over-zealous, especially where a long stmt is used.
The diameters of some preferred stems, when in the compressed state for delivery to a desired location within a body lumen is typically from about two to about three times less than the diameter of the stems when in their expanded state. For example, typical stems may have a compressed external diameter of about 1 millimeter to about 3 millimeters for delivery and an expanded external diameter in a body lumen of about 3 millimeters to about 15 millimeters when released from compression in a large arterial vessel.
The metal surface coverage as a function of stmt diameter is calculated by dividing the total vessel contact metal surface area of the stmt structure by the surface area of the vessel at any given stent/vessel diameter. There is inverse relationship between the metal surface coverage and the stent expansion (the more expansion of the stmt, the less metal surface coverage).
The two most important features of the coronary stmt are basic to its use:
flexibility is required only during insertion and until deployment of the stmt at the target lesion.
Rigidity is required to supply long term support to the vessel wall, but only from the moment of deployment and on.
In a description of the Iris stmt (which is a slotted tube stmt made of 316L
stainless steel by Uni-Cath Inc. of Saddle Brook, New Jersey, U.S.A.) by Albert Tashji published in the Handbook of Coronary Stents, second edition,1998, chapter24 (see also U. S.
Patent Number 5,911,754, issued June 15, 1999), the expansion data observed is shown in Table 1.
STENT DIAMETER LENGTH SHORTENING METAL COVERAGE
mm (inches (mm (%) %) 1 0.04 16.9 -- 55.4 2.5 0.098 16.1 4.7 21.9 3 0.118 16 5.3 18.6 3.5 0.138 15.1 10.7 17 4 0.157 14 17.2 16.2 Table 1 The NIR stmt by SCIMED MEDTRONICS (SciMed Life Systems, Inc. of Maple Grove, MN, U.S.A. and Medtronics, Inc. of Minneapolis, MN, U.S.A.) is a mufti-cellular slotted tube design made of 316L stainless steel. The mufti-cellular design comes in two types to cover different vessel diameters. The 7-cell circumflex unexpended stmt will expand by different 5 size balloons to cover vessel diameters that range from 2.Smm to 3.Smm. The metal to artery percentage ratio for the 7-cell will range from 24% at 2.Smm to 14% at 3.Smm expansion and the stmt foreshortening ranges from 7% at 3.Smm to 14% at 4.Omm expansion. In order to prevent further reduction of the metal to artery percentage ratio and foreshortening of the stmt at expansion higher than 3.Smm, a second stmt is provided where the external diameter of the circumflex unexpended stmt is increased to 9-cell in order to expand up to Smm. The metal to artery percentage ratio for the 9-cell will range from 14% at 3.Omm to 11%
at S.Omm expansion and the stmt foreshortening ranges from 7% at 3.Smm to 14% at S.Omm expansion (PMA application # P980001 , published by the FDA in August 11, 1998). The drawback of the increase of the external diameter of the unexpended stmt will effect the flexibility, because there is inverse relationship between the external diameter and the flexibility of the unexpended stmt.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a flexible stmt which can be easily delivered through meandering and narrow arteries or other body lumens.
Another object of the invention is to provide the stmt as stated above, which can substantially prevent shortening of the entire length of the stmt when it is expanded. It is further obj ection of the present invention to provide a stmt which does not substantially change in length or at least does not reduce in length as the stmt diameter expands during balloon expansion.
A further obj ect of the present invention is to provide a stmt with a low profile when crimped over a delivery balloon of the stmt assembly.
A further object of the present invention is to provide a stmt with generous coverage of the wounded vessel wall, with a high metal/artery ratio. It is further objection of the present invention to provide a stmt with a closely spaced struts giving good, well-distributed radial strength.
16:05 FAa 613 234 3563 MacRse & Co.
' 06-03-2001_ - _ - - - - - _ _ - ,_", _ _ - _ - . CA 000000035 " CA 02358449 2001-07-16 Another object of the invention is to provide the stoont with a compressed state or uncxpand~ed diameter for deliveryto adesired locationwithia a bodyl>imenwhich allow a gradual increase up to five times the initial diameter of the stmt upon expansion. It is a ftutlur object of the t invention to provide a ewutmlled expansion of the stmt to avoid ovetstzing of the stmt relative to the normal "refaa~ce" segment Accordingly there is provided in one aspect of this invention an iatravascular tubular stoat expandable bvtwoea a first, constricted state and a second state of greater expanded diameter;
the stmt coaaprisiag is its constricted state:
a plurality of radiahy expandable rings each formed of a plurality of circum'ferentially extendable elona~s, each cireurnf~tially axtaadable element co~aaprisin8:
at least one first functional unit having a bendable joist from which a pair of arms extend so as to form thezebetween an elongate opening disposed in a first direction; and a plurality of second functional omits each of whichhaving a bendable joint fra~m which a pair of arms extend so as to fear therebctween as elongate opening disposed in a scwad ditedion;
the first direction being substantially papa~icularto the second direction;
and each pair of adjacent radiadly expandable rings being cotu~ected to each other at at least one location.
In accordance with another aspect of the invention, there is provided an intravaseular tubular steal expandable between a first, constricted stare and a second state of greater Gxpaaded diameter; the stmt comprising in its constricted state:
a plurality of radially expandable rings each formal of a plurality of circumfaacnially extendable elements, each circumfereatially extendable element comprising at least one functional wait having a bendable j oiat from which a pair of arms acGaad so as to form an elongate opening therebetween;
each expandable ring being disposed at as obli~ angle with respect to the longitudinal axis of the slant, and each pair of adj scent radislly expandable rings being connected to each other at at least one location.
AMENDED SHEET
EMPFANGSZEIT 6,MAR. 22;02 Hu~uRUCKSZE1T ~ MaR ~~~n~
A review article, Does Stent Design Influence Restenosis?, by Dr. J. Gunn published in the European Heart Journal July 1999 (Vol. 20, issuel4), stated that unlike restenosis after balloon angioplasty, the in-stmt restenosis consists predominantly of neointimal growth rather than the combination of neointima, recoil and downsize remodelling seen after the balloon angioplasty. The degree of restenosis is related to the extent of damage done at the time of implantation. The composition of the neointima of in-stmt restenosis is similar to that seen in balloon angioplasty, and includes vascular smooth muscle cells and inter-cellular matrix.
Any subtle differences in the composition of the neointima of the in-stmt restenosis and post -balloon injury, for example a suggestion of more matrix relatives to cell in the former, may be explained by the different nature and time-course of the two injuries: stmt struts produce local deep trauma, and the stmt as a whole produces chronic stretch; whereas balloon injury, which may also be deep, is transient an tends to be focal, with unilateral dissection rather than circumferential stretch. There is clinical evidence that the stmt geometry influences in-stmt restenosis. One widespread perception is that tissue prolapse at the central articulation of the Palmaz-Schatz stmt (U.S. Patent No. 5,382,261 to Palmaz dated January 17, 1995) increases in-stmt restenosis at that site. Intravascular ultrasound has also revealed that in-stmt restenosis within coil-stems is related to recoil, whereas in-stmt restenosis within slotted tube stems is related to sub-expansion. In a retrospective study of matched lesion, the flexible Micro StentTM from Arterial Vascular Engineering, Inc. of Santa Rosa, California., was associated with a higher restenosis rate than the more rigid Palmaz-Schatz stmt. Similarly, a coil-stmt has been shown to be associated with increased in-stmt restenosis compared with a slotted tube stmt in chronic total occlusions, a situation where radial strength is probably paramount.
In one systematic study, where the features of stmt geometry which make one stmt superior to another were investigated, changing the stmt configuration to reduce strut-strut intersections reduced the vascular injury score by 42%, thrombosis by 69% and neointimal hyperplasia by 38%. Coating with an inert polymer did not alter vascular injury or neointimal hyperplasia, although thrombosis was eliminated. Uniform (modest oversize) deployment of multiple examples of one design of stmt in normal porcine coronary artery, with many sections analysed at a consistent time point, allows precise mathematical analysis of the relationship between as many parameters of the stmt geometry as are thought useful in in-stmt restenosis.
Using this technique, extreme strut protrusion, large inter-strut distance, fracture ofthe internal elastic lamina, medial compression and location near the distal ends of the stmt have been identified as of particular importance. There was no direct relationship found between the number of struts and in-stmt restenosis unless the stmt was over-deployed, in which case more struts were advantageous, presumably distributing the forces of stretch more evenly and preventing isolated strut protrusion. In the same study, there was great lumen loss and neointimal growth at the distal end compared with the middle of the stems, possibly reflecting the taper seen in a porcine artery. There was suggestion that eccentricity of the stmt deployment (oblateness of the cross-section) adversely affected in-stmt restenosis. There is clinical intravascular ultrasound-based evidence for this, too. In one study, deviation from the circular in a stented vessel is associated with a trend towards increased target vessel revascularization at long-term follow-up. In contrast to the early days of stenting, when the fear of a "foreign body" reaction was still present, results such as this now point away from a minimalist approach towards generous coverage of the wounded vessel wall, with a high metal/artery ratio. The concept of maximizing the metal barrier is, of course, limited by poor "crimpability", unacceptable profile and inflexibility. Such designs (for example, the Jomed covered stmt made by Jomed Implantate GmbH of Rangendingen, DE) are already marketed, but have not yet reached wide acceptance.
Deployment strategies are also likely to affect the long-term result of stenting. Finite element analysis has revealed that low balloon compliance and the lowest possible balloon pressure to achieve adequate deployment are important variables. Balloon -(and stmt)-artery ratio (BAR) are also contributory. In his early studies, Schwartz ( J Am Coll Cardol 1992;19:267-274) used a BAR of 1.5:1, and produced dramatic injury with a high experimental animal mortality rate. Thomas (Jlnvas Cardiol 1997;9:453-460) , however, using a BAR of 1.1: l, experienced 100% patency and minimal neointima. In trying to draw any conclusion from the data available about the "ideal" stmt, a pattern is starting to emerge. Whilst preserving the desirable characteristics of low profile, trackability, conformability and visibility, a stmt should have many, closely spaced struts giving good, well-distributed radial strength. The inter-strut connections, whilst allowing for even balloon expansion and access to side-branches, should form a close meshwork which prevents large spaces from opening up between the struts, or from one strut protruding radially beyond its neighbours. The forces for expansion should be distributed evenly so that the stmt expands symmetrically, without eccentrity. Attention should be paid to the design of the ends of the stmt, so that a smooth transition to normal vessel is created, and distal oversizing is avoided. The design should preclude the development of large defects in metal coverage. Sizing of the stmt relative to the normal "reference" segment should not be over-zealous, especially where a long stmt is used.
The diameters of some preferred stems, when in the compressed state for delivery to a desired location within a body lumen is typically from about two to about three times less than the diameter of the stems when in their expanded state. For example, typical stems may have a compressed external diameter of about 1 millimeter to about 3 millimeters for delivery and an expanded external diameter in a body lumen of about 3 millimeters to about 15 millimeters when released from compression in a large arterial vessel.
The metal surface coverage as a function of stmt diameter is calculated by dividing the total vessel contact metal surface area of the stmt structure by the surface area of the vessel at any given stent/vessel diameter. There is inverse relationship between the metal surface coverage and the stent expansion (the more expansion of the stmt, the less metal surface coverage).
The two most important features of the coronary stmt are basic to its use:
flexibility is required only during insertion and until deployment of the stmt at the target lesion.
Rigidity is required to supply long term support to the vessel wall, but only from the moment of deployment and on.
In a description of the Iris stmt (which is a slotted tube stmt made of 316L
stainless steel by Uni-Cath Inc. of Saddle Brook, New Jersey, U.S.A.) by Albert Tashji published in the Handbook of Coronary Stents, second edition,1998, chapter24 (see also U. S.
Patent Number 5,911,754, issued June 15, 1999), the expansion data observed is shown in Table 1.
STENT DIAMETER LENGTH SHORTENING METAL COVERAGE
mm (inches (mm (%) %) 1 0.04 16.9 -- 55.4 2.5 0.098 16.1 4.7 21.9 3 0.118 16 5.3 18.6 3.5 0.138 15.1 10.7 17 4 0.157 14 17.2 16.2 Table 1 The NIR stmt by SCIMED MEDTRONICS (SciMed Life Systems, Inc. of Maple Grove, MN, U.S.A. and Medtronics, Inc. of Minneapolis, MN, U.S.A.) is a mufti-cellular slotted tube design made of 316L stainless steel. The mufti-cellular design comes in two types to cover different vessel diameters. The 7-cell circumflex unexpended stmt will expand by different 5 size balloons to cover vessel diameters that range from 2.Smm to 3.Smm. The metal to artery percentage ratio for the 7-cell will range from 24% at 2.Smm to 14% at 3.Smm expansion and the stmt foreshortening ranges from 7% at 3.Smm to 14% at 4.Omm expansion. In order to prevent further reduction of the metal to artery percentage ratio and foreshortening of the stmt at expansion higher than 3.Smm, a second stmt is provided where the external diameter of the circumflex unexpended stmt is increased to 9-cell in order to expand up to Smm. The metal to artery percentage ratio for the 9-cell will range from 14% at 3.Omm to 11%
at S.Omm expansion and the stmt foreshortening ranges from 7% at 3.Smm to 14% at S.Omm expansion (PMA application # P980001 , published by the FDA in August 11, 1998). The drawback of the increase of the external diameter of the unexpended stmt will effect the flexibility, because there is inverse relationship between the external diameter and the flexibility of the unexpended stmt.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a flexible stmt which can be easily delivered through meandering and narrow arteries or other body lumens.
Another object of the invention is to provide the stmt as stated above, which can substantially prevent shortening of the entire length of the stmt when it is expanded. It is further obj ection of the present invention to provide a stmt which does not substantially change in length or at least does not reduce in length as the stmt diameter expands during balloon expansion.
A further obj ect of the present invention is to provide a stmt with a low profile when crimped over a delivery balloon of the stmt assembly.
A further object of the present invention is to provide a stmt with generous coverage of the wounded vessel wall, with a high metal/artery ratio. It is further objection of the present invention to provide a stmt with a closely spaced struts giving good, well-distributed radial strength.
16:05 FAa 613 234 3563 MacRse & Co.
' 06-03-2001_ - _ - - - - - _ _ - ,_", _ _ - _ - . CA 000000035 " CA 02358449 2001-07-16 Another object of the invention is to provide the stoont with a compressed state or uncxpand~ed diameter for deliveryto adesired locationwithia a bodyl>imenwhich allow a gradual increase up to five times the initial diameter of the stmt upon expansion. It is a ftutlur object of the t invention to provide a ewutmlled expansion of the stmt to avoid ovetstzing of the stmt relative to the normal "refaa~ce" segment Accordingly there is provided in one aspect of this invention an iatravascular tubular stoat expandable bvtwoea a first, constricted state and a second state of greater expanded diameter;
the stmt coaaprisiag is its constricted state:
a plurality of radiahy expandable rings each formed of a plurality of circum'ferentially extendable elona~s, each cireurnf~tially axtaadable element co~aaprisin8:
at least one first functional unit having a bendable joist from which a pair of arms extend so as to form thezebetween an elongate opening disposed in a first direction; and a plurality of second functional omits each of whichhaving a bendable joint fra~m which a pair of arms extend so as to fear therebctween as elongate opening disposed in a scwad ditedion;
the first direction being substantially papa~icularto the second direction;
and each pair of adjacent radiadly expandable rings being cotu~ected to each other at at least one location.
In accordance with another aspect of the invention, there is provided an intravaseular tubular steal expandable between a first, constricted stare and a second state of greater Gxpaaded diameter; the stmt comprising in its constricted state:
a plurality of radially expandable rings each formal of a plurality of circumfaacnially extendable elements, each circumfereatially extendable element comprising at least one functional wait having a bendable j oiat from which a pair of arms acGaad so as to form an elongate opening therebetween;
each expandable ring being disposed at as obli~ angle with respect to the longitudinal axis of the slant, and each pair of adj scent radislly expandable rings being connected to each other at at least one location.
AMENDED SHEET
EMPFANGSZEIT 6,MAR. 22;02 Hu~uRUCKSZE1T ~ MaR ~~~n~
In general, the design geometry of the subject stems is such that substantially no shortening of the stent occurs throughout expansion and over the viable working range of the stmt. These and other objects and advantages of the present invention are described in the following description and illustrated by way of drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 A is a schematic drawing illustrating a tubular stmt in its unexpended, pre-deployment state; and Fig. 1B is a schematic drawing similar to that of Fig.
A, but showing the stmt in a radially expanded state;
Figs. 2A to 2C are schematic drawings showing a flattened portion of the cylindrical contour of the various tubular stems;
Figs. 3A through 3I are schematic drawings showing various stmt elements for describing their mechanics during expansion;
Fig. 4A is a schematic showing a flattened portion of the cylindrical contour of a prior art stmt, while Fig. 4B is a schematic of a flattened portion of a stmt in accordance with the present invention; and Fig. 4C is an illustration of the stmt portion show in Fig. 4B but in its expanded state.
Figs. 5 to 1 S are schematic drawings showing alternate embodiments of the stmt according to the present invention as a flattened portion thereof;
Fig. 16A is a magnified plan view of a dissected and laid flat stmt prototype made in accordance with the present invention; Fig. 16B is a greatly enlarged detail section of Fig.
16A; and Fig. 16C is a schematic showing a flattened portion of the stmt of Fig. 16A but shown in its expanded state; and Figs. 17 to 19 are schematic drawings showing further stmt embodiments made in accordance with the teachings of the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 A illustrates schematically a simple form of a stmt 10 shown in its constricted state, i.e.
prior to the deployment and expansion. In general, the stmt 10 comprises a plurality of interconnected radially expandable rings 12 arranged coaxially so as to form a generally tubular structure having a longitudinal axis 14. Each pair of adjacent rings 12 is interconnected by at least one interconnection member 15. The stmt of the present invention is operable with two or more such rings 12, the number of which is generally dependent on specific structure of the rings and how they are interconnected as well as the desired length of the stmt. Each ring 12 comprises a series of expandable elements 16 connected together in a circular contour. As shown schematically in Fig. 1 B, in response to the radially outwardly directed expansion force of a pressurized balloon inserted through the ring 12, each expansion element 16 expands along the generally increasing circumferential contour of the stmt 10'.
Figs. 2A, 2B and 2C show, for explanatory purposes, specific examples of portions of stems 10A, l OB and l OC, laid flat for illustrative purposes. Stems 10A, l OB and l OC comprise a plurality of coaxially-arranged annular rings 12. Each ring 12 consists of a series of connected elements 16- which are circumferentially expandable. Adjacent pairs of rings 12 are interconnected by interconnecting elements 15 which can be generally linear as shown or can themselves be expandable or contractible longitudinally with respect to the axis of the stmt in response to the expansion of the rings 12. In this regard, attention is directed to Applicant's copending International Application No. PCT/CA99/00632 filed July 12, 1999 and entitled "Expandable Endovascular Medical Tubular Stent", the entirety of which is incorporated herein by reference, which contains illustrations of a variety of different arrangements for the elements that constitute the stmt.
In general, the aforementioned stems 10A, lOB and lOC and, in particular, the extendable elements 16, can be considered to comprise one or more "functional units" each of which, roughly speaking, is an element that doubles-back on itself so as to form a pair of "arms"
which are attached at one end and separated at their other thus resulting in a "U", "V" or "C"
shape, for example. In the exemplary stems 1 OA,1 OB and 1 OC shown in Figs.
2A, 2B and 2C, these functional units are U-shaped and are oriented such that their "arms" or their "openings"
are disposed either parallel with or transverse to the stmt axis 14. Figs. 3A
and 3C illustrate such functional units 20A and 20B, respectively. Fig. 3A shows a functional unit 20A of length L, having a pair of generally parallel arms 22,24 connected by a deformable or bendable joint 26. The arms 22,24 are spaced apart a circumferential distance C, by an opening 28.
Opening 28 as well as arms 22,24 are disposed generally parallel with the longitudinal axis 14 of the stmt. In general, many prior art stems utilize such parallelly-oriented functional units or variations thereof in their construction, including Applicant's prior U.S.
Patent No.
5,755,776, issued May 26, 1998 and entitled "Permanent Expandable Intraluminal Tubular Stent", which is also incorporated herein by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 A is a schematic drawing illustrating a tubular stmt in its unexpended, pre-deployment state; and Fig. 1B is a schematic drawing similar to that of Fig.
A, but showing the stmt in a radially expanded state;
Figs. 2A to 2C are schematic drawings showing a flattened portion of the cylindrical contour of the various tubular stems;
Figs. 3A through 3I are schematic drawings showing various stmt elements for describing their mechanics during expansion;
Fig. 4A is a schematic showing a flattened portion of the cylindrical contour of a prior art stmt, while Fig. 4B is a schematic of a flattened portion of a stmt in accordance with the present invention; and Fig. 4C is an illustration of the stmt portion show in Fig. 4B but in its expanded state.
Figs. 5 to 1 S are schematic drawings showing alternate embodiments of the stmt according to the present invention as a flattened portion thereof;
Fig. 16A is a magnified plan view of a dissected and laid flat stmt prototype made in accordance with the present invention; Fig. 16B is a greatly enlarged detail section of Fig.
16A; and Fig. 16C is a schematic showing a flattened portion of the stmt of Fig. 16A but shown in its expanded state; and Figs. 17 to 19 are schematic drawings showing further stmt embodiments made in accordance with the teachings of the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 A illustrates schematically a simple form of a stmt 10 shown in its constricted state, i.e.
prior to the deployment and expansion. In general, the stmt 10 comprises a plurality of interconnected radially expandable rings 12 arranged coaxially so as to form a generally tubular structure having a longitudinal axis 14. Each pair of adjacent rings 12 is interconnected by at least one interconnection member 15. The stmt of the present invention is operable with two or more such rings 12, the number of which is generally dependent on specific structure of the rings and how they are interconnected as well as the desired length of the stmt. Each ring 12 comprises a series of expandable elements 16 connected together in a circular contour. As shown schematically in Fig. 1 B, in response to the radially outwardly directed expansion force of a pressurized balloon inserted through the ring 12, each expansion element 16 expands along the generally increasing circumferential contour of the stmt 10'.
Figs. 2A, 2B and 2C show, for explanatory purposes, specific examples of portions of stems 10A, l OB and l OC, laid flat for illustrative purposes. Stems 10A, l OB and l OC comprise a plurality of coaxially-arranged annular rings 12. Each ring 12 consists of a series of connected elements 16- which are circumferentially expandable. Adjacent pairs of rings 12 are interconnected by interconnecting elements 15 which can be generally linear as shown or can themselves be expandable or contractible longitudinally with respect to the axis of the stmt in response to the expansion of the rings 12. In this regard, attention is directed to Applicant's copending International Application No. PCT/CA99/00632 filed July 12, 1999 and entitled "Expandable Endovascular Medical Tubular Stent", the entirety of which is incorporated herein by reference, which contains illustrations of a variety of different arrangements for the elements that constitute the stmt.
In general, the aforementioned stems 10A, lOB and lOC and, in particular, the extendable elements 16, can be considered to comprise one or more "functional units" each of which, roughly speaking, is an element that doubles-back on itself so as to form a pair of "arms"
which are attached at one end and separated at their other thus resulting in a "U", "V" or "C"
shape, for example. In the exemplary stems 1 OA,1 OB and 1 OC shown in Figs.
2A, 2B and 2C, these functional units are U-shaped and are oriented such that their "arms" or their "openings"
are disposed either parallel with or transverse to the stmt axis 14. Figs. 3A
and 3C illustrate such functional units 20A and 20B, respectively. Fig. 3A shows a functional unit 20A of length L, having a pair of generally parallel arms 22,24 connected by a deformable or bendable joint 26. The arms 22,24 are spaced apart a circumferential distance C, by an opening 28.
Opening 28 as well as arms 22,24 are disposed generally parallel with the longitudinal axis 14 of the stmt. In general, many prior art stems utilize such parallelly-oriented functional units or variations thereof in their construction, including Applicant's prior U.S.
Patent No.
5,755,776, issued May 26, 1998 and entitled "Permanent Expandable Intraluminal Tubular Stent", which is also incorporated herein by reference.
Fig. 3B demonstrates the changes to the functional unit 20A' during radial expansion of the stmt. In general, initial deformation takes place in the bendable joint 26 and both the arm members 22;24 move diagonally away from each other in the opposite (i.e.
circumferential) direction which results in an increase of the circumferential distance C,' which results in an overall increase in the circumference of the stmt 10 during expansion. At the same time, the length L of the functional unit 20A will be reduced to a length L,' which, in turn, results in overall foreshortening of the stmt 10.
In order to avoid the foreshortening of the functional unit 20A,20A', a change in the orientation is needed as shown in the functional unit 20B in Fig. 3 C in which the arm members 22,24 are disposed generally perpendicular to the longitudinal axis 14 of the stmt 10 and connected by bendable joint 26 arranged generally parallel to the longitudinal axis 14. In this case, the axial length of the functional unit 20B is shown as Lz while its circumferential length is shown as C2. If the arm members 22,24 are caused to move diagonally away from each other, this will result (see Fig. 3D) in an increase of the length LZ of the functional unit 20B
to LZ' which, in turn, will result in overall increase in the length of the stmt 10. At the same time, there will be a decrease in the circumferential length CZ of the functional unit 20B to CZ' which will result in a reduction of the circumference of the stmt 10 and this reduction is at odds with the desired capability for expansion.
To reach an optimum state between Figs. 3A and 3C, there is provided in Fig.
3E a diagonally-oriented functional unit 20C in which the arm members 22,24 have a diagonal orientation with respect to the longitudinal axis 14 of the stmt 10. The arms 22,24 are connected by a bendable joint 26 also arranged diagonal to the longitudinal axis 14 of the stmt 10.
The functional unit 20C has a length L3 and the ends of the arms 22,24 are separated a circumferential distance C3.
Upon radial expansion (as shown in Fig. 3F), arm members 22,24 of the functional unit 20C' move diagonally away from each other in the opposite direction which results in increase of the circumferential distance C3' which, in turn, results in overall increase in the circumference of the stmt 10 during expansion. At the same time, the length L3' of the functional unit 20C' will be at least be maintained with respect to initial length L3 or non-significantly reduced which will result in practically no foreshortening of the stmt 10 during expansion.
Another alternative to prevent foreshortening of the functional unit is shown in Fig. 3G in which the functional unit 20D having a length L4 has its two arm members 22,24 angled towards one another each at an angle a from parallelity with the stmt axis 14 so that the opening 28 is narrower at the ends of the arms 22,24 distal the bendable joint 26 than at their proximal ends. This arrangement is termed herein as "over-parallel". The advantage to this over-parallel arrangement is that where the ends distal the bendable joint are spaced an initial circumferential distance C4, circumferential expansion initially opens the arms 22,24 through 5 to parallelity as shown in Fig. 3H whereat the ends of the distal arms 22,24are spaced apart a greater distance C4' while the length of the functional unit 20D' expands slightly to L4'.
Continued radial expansion causes further widening of the circumferential distance to C4"
(termed "under-parallel") as shown in Fig. 3I, resulting in an overall increase in the circumference of the stmt 10. However, as the arms 22,24 diverge from parallel, the overall 10 length L4" of the functional unit 20D"will start to reduce from L4'. When the angle a"= a, length L4" will equal the initial length L4 and while there has been a circumferential expansion to C4", no overall shortening of the functional unit 20D has resulted. Of course, further radial expansion will start to foreshorten the functional unit 20D" as compared with its original length. Of importance, however, is that in comparing the functional units 20A
and 20D of Figs. 3A and 3G, respectively, for a given amount of circumferential expansion, the axial shortening of the former will necessarily be greater than that of the latter.
Alternately stated, for a given reduction in length of one of these functional units, a greater circumferential expansion can be achieved by the functional unit 20D of Fig. 3G than the functional unit 20A
of Fig. 3A. Accordingly, these advantageous principles can be incorporated into the design of stents to achieve the desired minimization or elimination of axial reduction upon radial/circumferential expansion.
Figs. 4B and 4C illustrate the principle of the over-parallel functional unit 20D of Fig. 3G as applied to the substantially rectilinear stmt design 40 as shown in Fig. 4A, which is derived from Applicant's aforementioned U.S. Patent No. 5,755,776. Stent 40 comprises a plurality of circular rings 12 arranged coaxially with respect to stmt axis 14. Each ring 12 comprises a plurality of circumferentially expandable elements 16 arranged in a generally serpentine or square wave-form pattern about the cylindrical contour of the stmt. The arrangement of circumferentially expandable elements 16 in one ring 12 is such that the adjacent ring 12 is the mirror opposite in the axial direction. Thus, the openings 28 of the expandable elements 16 of one ring 12 oppose the openings 28 of the expandable elements 16 of an adjacent ring 12, whereas the "joints" 26 of the expandable elements 16 are disposed immediately adjacent the joints 26 of the adjacent ring 12. By interconnecting adjacent pairs of rings 12 by at least one interconnecting member 15 per pair from the "bottom" 42 of an expandable element 16 to the bottom 42 of an adjacent expandable element 16, the stmt 40 resists reduction in length upon radial expansion as explained in Applicant's aforementioned U.S. Patent No.
5,755,776. In the stmt 50 shown in Fig. 4B, the joints 26 between the pairs of arms 22,24 are rounded and the arms 22,24, which are generally linear, are angled toward one another so as to form an expandable element 16 with a convergent opening 28 which is the same as the over-parallel functional unit 20D of Fig. 3G. The expandable element 16 alternatingly repeats itself so as to form a serpentine or sinusoidal ring 12. Stated alternately, the arm 22 for one expandable element 16 is shared as one arm 22 of the circumferentially adjacent expandable element 16 as shown in Fig. 4B. Interconnecting members 15 connects the bottom 42 of one expandable element 16 to an opposed expandable element 16 so as to function in the same manner as the interconnecting member 15 of the stmt 40 of Fig. 4A as aforesaid. Upon radial expansion of the stmt 50 as shown in Fig. 4C, the diverging of the arms 22,24 initially causes each ring to lengthen in the axial direction of the stmt SOand, only once the arms 22,24 are past parallel, do the rings 12 start to shorten. Thus, the propensity for shortening upon radial expansion of the stmt 50 of Fig. 4B is even further reduced as compared with the arrangement of Fig. 4A
in accordance with the previously discussion with respect to functional unit 20D of Fig. 3G.
Variations of the stmt 50 of Fig. 4B are shown in Figs. 5 and 6 as stems 60,70 in their compressed (i.e. unexpanded), pre-deployment state. In Fig. 5, the ring interconnecting member 62 essentially takes the place of an adj acent pair of expandable elements 16' as shown in stippled lines. As with the arrangement shown in Fig. 4, interconnecting member 62 serves to reduce the longitudinal reduction of the stmt 60. The presence of the over-parallel functional units 20D serve to further reduce the amount of foreshortening. In order to increase axial flexibility, the stent 70 of Fig. 6 is provided with a relatively short interconnection member 64s between adjacent rings 12. Enhanced axial flexibility is important in the undeployed stmt to enable the stmt to be delivered to a desired location via a tortuous vessel.
The stents 50,60,70 shown in Figs. 4B,5, and 6 comprise a plurality of the over-parallel functional units 20D disposed generally parallel with respect to the longitudinal axis 14 of the respective stmt (i.e. the openings 28 are aligned generally parallel as shown in Fig. 3G).
However, Applicant has found as explained in his aforementioned International Application No. PCT/CA99/00632, that by orienting at least some of the roughly linear components of the circumferentially expandable elements 16 in the circumferential direction, such as is shown in Figs. 2A-2C, self compensation of the longitudinal shortening of the stmt occurs due to the longitudinal expansion of each ring 12 coupled with the reduction in distance between adj acent rings. By orienting at least some over-parallel functional units in the circumferential direction, even further radial expansion is possible while still maintaining the self compensating feature of the stmt, thus resulting in a greater expansion range with little or no change in the length of the stmt over the working range.
In this regard, there is provided in Fig. 7 one embodiment of the invention which includes a plurality of rings 12 each comprised of a series of circumferentially expandable serpentine elements 16. Each expandable element 16 is comprised of a plurality of over-parallel functional units 20E oriented generally circumferentially or perpendicular to the longitudinal axis 14 of the stmt 80. Adjacent rings 12 are interconnected at selective locations 82 whereat the bendable joint 26 of one over-parallel functional unit 20E is integrally formed, fused or otherwise attached to the bendable joint 26 of an adjacent over-parallel functional unit 20E.
In other words, the external apexes of adjacent bendable joints 26 are attached. With this stmt 80, each expandable element 16 is connected to the next in the series by way of a further over-parallel functional unit 20F oriented generally parallel to the axis 14.
Fig. 8 shows a stmt 90 which is a variation of the stmt 80 embodiment of Fig.
7 having substantially identical rings 12 comprised of a series of expandable elements 16, each being a horizontal mirror image to the next in the series. The rings 12 themselves are vertical mirror images of the adjacent ring 12. However, the rings 12 in this embodiment are interconnected in the same manner as the stmt 50 of Fig. 4B, that being an interconnecting member 1 S which extends from the bottom of one axially aligned, over-parallel functional units 20F to the bottom of an opposed over-parallel functional unit 20F.
The stmt 100 shown in Fig. 9 is similar to the stmt 80 of Fig. 7 except that the arms 22A,24A
of the circumferentially aligned over-parallel functional units 20E which are on the outermost sides of each expandable element 16 are circumferentially aligned. Between circumferentially adjacent expandable elements 16, an axially-aligned functional unit 20A, such as shown in Fig.
3A is provided.
The stmt 110 shown in Fig. 10 comprises a plurality of rings 12, each identical to its adjacent ring 12. While as with the Fig. 7 and Fig. 8 embodiments, adjacent bendable joints 26 are interconnected by member 15, due to the geometry, the bottom of one axially-aligned over-parallel functional unit 20F is attached by member 15 to the apex of an adjacent axially-aligned over-parallel functional unit 20F'.
circumferential) direction which results in an increase of the circumferential distance C,' which results in an overall increase in the circumference of the stmt 10 during expansion. At the same time, the length L of the functional unit 20A will be reduced to a length L,' which, in turn, results in overall foreshortening of the stmt 10.
In order to avoid the foreshortening of the functional unit 20A,20A', a change in the orientation is needed as shown in the functional unit 20B in Fig. 3 C in which the arm members 22,24 are disposed generally perpendicular to the longitudinal axis 14 of the stmt 10 and connected by bendable joint 26 arranged generally parallel to the longitudinal axis 14. In this case, the axial length of the functional unit 20B is shown as Lz while its circumferential length is shown as C2. If the arm members 22,24 are caused to move diagonally away from each other, this will result (see Fig. 3D) in an increase of the length LZ of the functional unit 20B
to LZ' which, in turn, will result in overall increase in the length of the stmt 10. At the same time, there will be a decrease in the circumferential length CZ of the functional unit 20B to CZ' which will result in a reduction of the circumference of the stmt 10 and this reduction is at odds with the desired capability for expansion.
To reach an optimum state between Figs. 3A and 3C, there is provided in Fig.
3E a diagonally-oriented functional unit 20C in which the arm members 22,24 have a diagonal orientation with respect to the longitudinal axis 14 of the stmt 10. The arms 22,24 are connected by a bendable joint 26 also arranged diagonal to the longitudinal axis 14 of the stmt 10.
The functional unit 20C has a length L3 and the ends of the arms 22,24 are separated a circumferential distance C3.
Upon radial expansion (as shown in Fig. 3F), arm members 22,24 of the functional unit 20C' move diagonally away from each other in the opposite direction which results in increase of the circumferential distance C3' which, in turn, results in overall increase in the circumference of the stmt 10 during expansion. At the same time, the length L3' of the functional unit 20C' will be at least be maintained with respect to initial length L3 or non-significantly reduced which will result in practically no foreshortening of the stmt 10 during expansion.
Another alternative to prevent foreshortening of the functional unit is shown in Fig. 3G in which the functional unit 20D having a length L4 has its two arm members 22,24 angled towards one another each at an angle a from parallelity with the stmt axis 14 so that the opening 28 is narrower at the ends of the arms 22,24 distal the bendable joint 26 than at their proximal ends. This arrangement is termed herein as "over-parallel". The advantage to this over-parallel arrangement is that where the ends distal the bendable joint are spaced an initial circumferential distance C4, circumferential expansion initially opens the arms 22,24 through 5 to parallelity as shown in Fig. 3H whereat the ends of the distal arms 22,24are spaced apart a greater distance C4' while the length of the functional unit 20D' expands slightly to L4'.
Continued radial expansion causes further widening of the circumferential distance to C4"
(termed "under-parallel") as shown in Fig. 3I, resulting in an overall increase in the circumference of the stmt 10. However, as the arms 22,24 diverge from parallel, the overall 10 length L4" of the functional unit 20D"will start to reduce from L4'. When the angle a"= a, length L4" will equal the initial length L4 and while there has been a circumferential expansion to C4", no overall shortening of the functional unit 20D has resulted. Of course, further radial expansion will start to foreshorten the functional unit 20D" as compared with its original length. Of importance, however, is that in comparing the functional units 20A
and 20D of Figs. 3A and 3G, respectively, for a given amount of circumferential expansion, the axial shortening of the former will necessarily be greater than that of the latter.
Alternately stated, for a given reduction in length of one of these functional units, a greater circumferential expansion can be achieved by the functional unit 20D of Fig. 3G than the functional unit 20A
of Fig. 3A. Accordingly, these advantageous principles can be incorporated into the design of stents to achieve the desired minimization or elimination of axial reduction upon radial/circumferential expansion.
Figs. 4B and 4C illustrate the principle of the over-parallel functional unit 20D of Fig. 3G as applied to the substantially rectilinear stmt design 40 as shown in Fig. 4A, which is derived from Applicant's aforementioned U.S. Patent No. 5,755,776. Stent 40 comprises a plurality of circular rings 12 arranged coaxially with respect to stmt axis 14. Each ring 12 comprises a plurality of circumferentially expandable elements 16 arranged in a generally serpentine or square wave-form pattern about the cylindrical contour of the stmt. The arrangement of circumferentially expandable elements 16 in one ring 12 is such that the adjacent ring 12 is the mirror opposite in the axial direction. Thus, the openings 28 of the expandable elements 16 of one ring 12 oppose the openings 28 of the expandable elements 16 of an adjacent ring 12, whereas the "joints" 26 of the expandable elements 16 are disposed immediately adjacent the joints 26 of the adjacent ring 12. By interconnecting adjacent pairs of rings 12 by at least one interconnecting member 15 per pair from the "bottom" 42 of an expandable element 16 to the bottom 42 of an adjacent expandable element 16, the stmt 40 resists reduction in length upon radial expansion as explained in Applicant's aforementioned U.S. Patent No.
5,755,776. In the stmt 50 shown in Fig. 4B, the joints 26 between the pairs of arms 22,24 are rounded and the arms 22,24, which are generally linear, are angled toward one another so as to form an expandable element 16 with a convergent opening 28 which is the same as the over-parallel functional unit 20D of Fig. 3G. The expandable element 16 alternatingly repeats itself so as to form a serpentine or sinusoidal ring 12. Stated alternately, the arm 22 for one expandable element 16 is shared as one arm 22 of the circumferentially adjacent expandable element 16 as shown in Fig. 4B. Interconnecting members 15 connects the bottom 42 of one expandable element 16 to an opposed expandable element 16 so as to function in the same manner as the interconnecting member 15 of the stmt 40 of Fig. 4A as aforesaid. Upon radial expansion of the stmt 50 as shown in Fig. 4C, the diverging of the arms 22,24 initially causes each ring to lengthen in the axial direction of the stmt SOand, only once the arms 22,24 are past parallel, do the rings 12 start to shorten. Thus, the propensity for shortening upon radial expansion of the stmt 50 of Fig. 4B is even further reduced as compared with the arrangement of Fig. 4A
in accordance with the previously discussion with respect to functional unit 20D of Fig. 3G.
Variations of the stmt 50 of Fig. 4B are shown in Figs. 5 and 6 as stems 60,70 in their compressed (i.e. unexpanded), pre-deployment state. In Fig. 5, the ring interconnecting member 62 essentially takes the place of an adj acent pair of expandable elements 16' as shown in stippled lines. As with the arrangement shown in Fig. 4, interconnecting member 62 serves to reduce the longitudinal reduction of the stmt 60. The presence of the over-parallel functional units 20D serve to further reduce the amount of foreshortening. In order to increase axial flexibility, the stent 70 of Fig. 6 is provided with a relatively short interconnection member 64s between adjacent rings 12. Enhanced axial flexibility is important in the undeployed stmt to enable the stmt to be delivered to a desired location via a tortuous vessel.
The stents 50,60,70 shown in Figs. 4B,5, and 6 comprise a plurality of the over-parallel functional units 20D disposed generally parallel with respect to the longitudinal axis 14 of the respective stmt (i.e. the openings 28 are aligned generally parallel as shown in Fig. 3G).
However, Applicant has found as explained in his aforementioned International Application No. PCT/CA99/00632, that by orienting at least some of the roughly linear components of the circumferentially expandable elements 16 in the circumferential direction, such as is shown in Figs. 2A-2C, self compensation of the longitudinal shortening of the stmt occurs due to the longitudinal expansion of each ring 12 coupled with the reduction in distance between adj acent rings. By orienting at least some over-parallel functional units in the circumferential direction, even further radial expansion is possible while still maintaining the self compensating feature of the stmt, thus resulting in a greater expansion range with little or no change in the length of the stmt over the working range.
In this regard, there is provided in Fig. 7 one embodiment of the invention which includes a plurality of rings 12 each comprised of a series of circumferentially expandable serpentine elements 16. Each expandable element 16 is comprised of a plurality of over-parallel functional units 20E oriented generally circumferentially or perpendicular to the longitudinal axis 14 of the stmt 80. Adjacent rings 12 are interconnected at selective locations 82 whereat the bendable joint 26 of one over-parallel functional unit 20E is integrally formed, fused or otherwise attached to the bendable joint 26 of an adjacent over-parallel functional unit 20E.
In other words, the external apexes of adjacent bendable joints 26 are attached. With this stmt 80, each expandable element 16 is connected to the next in the series by way of a further over-parallel functional unit 20F oriented generally parallel to the axis 14.
Fig. 8 shows a stmt 90 which is a variation of the stmt 80 embodiment of Fig.
7 having substantially identical rings 12 comprised of a series of expandable elements 16, each being a horizontal mirror image to the next in the series. The rings 12 themselves are vertical mirror images of the adjacent ring 12. However, the rings 12 in this embodiment are interconnected in the same manner as the stmt 50 of Fig. 4B, that being an interconnecting member 1 S which extends from the bottom of one axially aligned, over-parallel functional units 20F to the bottom of an opposed over-parallel functional unit 20F.
The stmt 100 shown in Fig. 9 is similar to the stmt 80 of Fig. 7 except that the arms 22A,24A
of the circumferentially aligned over-parallel functional units 20E which are on the outermost sides of each expandable element 16 are circumferentially aligned. Between circumferentially adjacent expandable elements 16, an axially-aligned functional unit 20A, such as shown in Fig.
3A is provided.
The stmt 110 shown in Fig. 10 comprises a plurality of rings 12, each identical to its adjacent ring 12. While as with the Fig. 7 and Fig. 8 embodiments, adjacent bendable joints 26 are interconnected by member 15, due to the geometry, the bottom of one axially-aligned over-parallel functional unit 20F is attached by member 15 to the apex of an adjacent axially-aligned over-parallel functional unit 20F'.
The interconnection of the adjacent rings 12 can take on various forms as already shown in Figs. 7 to 10 and as shown in Figs. 11 to 15. In Fig. 11, selective adjacent portions 120 of circumferentially expandable elements 16 of adj acent rings 12 may be integrally formed, fused or otherwise attached to form the connection. In Fig. 12, an interconnecting element 122 extends between a portion of one expandable element 16 of one ring 12 and a portion of another expandable element 16' in an adjacent ring 12'. In this case, the expandable element 16 is not axially adjacent the expandable element 16'. The interconnecting member need not be linear and may take a variety of different shapes to promote better axial flexibility of the stmt, maintaining the axial length of the stmt, and/or to provide additional vessel wall support and, hence, greater metal coverage. As shown in Fig. 12, the interconnecting member 122 is serpentine or N-shaped which is geared toward promoting separation between rings 12,12' during expansion. In Fig. 13, the interconnecting member 124 is shown as triple-S-shaped which tends to increase the metal content, increase the radial strength and serves to fill the larger gaps for more complete support. In Fig. 14, the interconnecting member 126 is disposed between portions of adjacent expandable elements 16 of adjacent rings. In this case, interconnecting member 126 is shown as U-shaped but any one of a variety of shapes may be employed. Fig. 15 illustrates more complex interconnecting mechanisms 128,130.
Interconnecting mechanism 128 comprises a first interconnecting member 128A
disposed between portions of adjacent expandable elements 16 of adjacent rings 12,12' and a second interconnecting member 128B disposed between portions of adjacent expandable elements 16 of adjacent rings 12,12'. The interconnecting members 128A,128B are integrally formed, fused or otherwise attached to each other. The cloverleaf design of the interconnecting members 128A,128B permits some local axial and circumferential expansion.
Interconnecting mechanism 130 comprises a first interconnecting member 130A
disposed between non-adjacent portions expandable elements 16 of adjacent rings 12',12 and a second interconnecting member 130B disposed between non-adjacent portions of adjacent expandable elements 16 of adjacent rings 12',12. Both the interconnecting members 130A,130B are N-shaped with their central leg portions crossingly attached. The interconnecting mechanisms 128,130 serve to increase the metal coverage, which will give more radial support and reduce the gaps between the struts/members, and can be designed to limit the radial expansion of the stmt so as to reduce the risk of stmt rupture by overinflation.
Fig. 16A shows a complete portion of a stent 140 (as laid flat) in accordance with a prototype of the present invention which is similar to the stmt portion 100 of Fig. 9 except that the expandable element 16 includes an additional circumferentially-oriented, over-parallel functional unit 20E. In addition, adjacent rings 12 are interconnected by a relatively short interconnecting member 142 to facilitate axial flexing. As can be seen, the stmt 140 provides substantial metal coverage when in its unexpanded state shown in Fig. 16A. The length L
=15.851mm and the distance C, which is the circumference is 4.393mm which results in a tubular stmt of approximately 1.37mm diameter. Fig. 16B illustrates an enlarged section of the stmt 140 of Fig. 16A. For reference purposes, Table 2 sets out the length L and radius R
dimensions (in mm) as measured:
Li LZ L3 La Ls L6 L~ R, Rz R3 Ra Rs R6 R~ Rs 0.8460.5630.3980.070.080.080.080.140.140.090.1650.050.060.1310.05 Table 2 The thickness of the material, i.e the stmt's tubular wall thickness is on the order of about 0.05-0.2mm.
Fig. 16C shows a portion of the stmt 140 in its expanded form as 140'. The expandable elements 16' have started to move diagonally and the axially-oriented functional units 20A' have expanded circumferentially to an "under-parallel" disposition. The rings 12' are prevented from separation by interconnecting members 142'. The expansion causes a tensile force component to be exerted along the expandable element 16', causing the individual functional units 20E'expand from their originally over-parallel disposition to parallel as shown in Fig. 16C and with sufficient expansion, to an under-parallel disposition.
Table 3 sets out the results of radial expansion testing the stent 140.
STENT DIAMETER LENGTH SHORTENING METAL
COVERAGE
(mm) (inches) (mm) (%) (%) 1.37 0.054 16 -- 52 3 0.118 16 0 24 3.5 0.138 16 0 20 4 0.157 16 0 17 Table 3 As can be seen from Table 3, the length of the stmt 140 remains the same over the range from its nominal, unexpanded diameter of 1.37mm to 4mm. These results can be compared with the results of Uni-Cath, Inc.'s Iris stmt as shown in Table 1, which show stmt length reduction as expansion increases. In addition, the stmt 140 retains acceptable metal coverage over the 5 expansion range.
The self compensating principle as described above with respect to the diagonally-oriented functional element 20C of Fig. 3E, can also be combined with the aforementioned over-parallel concept for axially- or circumferentially-oriented functional elements 20D,20E and arranged to optimize axially flexibility for ease of deployment without significant detriment 10 to strength of the expanded stmt after deployment. To illustrate the combination of these principles, there is shown in Fig. 17 a stmt 150 comprising a plurality of similar rings 152.
Each ring 152 consists of an alternating series of over-parallel functional elements 20G which are arranged diagonally with respect to the longitudinal axis 14 of the stmt 150. Each ring 152 forms a separate oblique cylinder and is not part of a "helical winding", and accordingly, the 15 end rings 152 are not as prone to splaying as would be the case with a free end portion of a helical winding.
As with the stent 50 of Fig. 4B, adjacent rings 152 are interconnected with an interconnecting member 154 between opposed bendable joints 156. The interconnecting members can be attached in an number of ways, such as for example, bottom-to-bottom as shown, apex-to-apex as shown in Fig. 16A, or apex-to-bottom as shown in Fig. 10. Similarly, to increase the flexibility as aforesaid, the length of the connecting member 164 between adjacent rings 162 can be reduced as aforesaid and as illustrated in Fig. 18.
The diagonally-oriented functional unit 20C concept can also be employed in a stmt without use of the over-parallel feature of Fig. 3G to substantially the same advantage. By way of example, stmt 170 of Fig. 19 is constructed of a plurality of obliquely disposed rings 172.
Each ring 172 consists of a series of circumferentially expandable elements 16 in this case connected to the next expandable element in the series by a diagonally-disposed functional unit 20C. Each expandable element comprises one or more diagonally-oriented functional units 20C' which in this case are disposed generally at right angles to the diagonally-disposed functional unit 20C. Selected apexes of adjacent bendable joints 176 of adjacent rings 172 may be attached at 174 to form the ring interconnections or the interconnecting can be accomplished in any of the manners discussed in this application or in Applicant's aforementioned International Application No. PCT/CA99/00632.
The stems described herein are preferably fabricated from biocompatible, low memory, more plastic than elastic material to permit the stmt to be expanded and deformed, yet sufficiently rigid to permit the stmt to retain its expanded and deformed configuration with an enlarged diameter and also to resist radial collapse.
Typically, stems in accordance with the teachings herein may be expanded up to about four times their original constricted diameters yet still have desirable properties of good axial flexibility in the constricted state and resistance to radial collapse and comprehensive wall support in the expanded state. Accordingly, stems may be provided for example in nominal diameters d of about lmm, l.Smm, and 2mm which, depending on the specific structure, may be expanded to 4mm, 6mm or 8mm, respectively, which should enable a minimum number of stems to be employed in most situations. It should be borne in mind that the stems of the present invention are operable over their entire range because they deform substantially continuously under application of an radially outwardly directed force. Upon removal of the force, deformation halts and the stmt remains sufficiently rigid to withstand the radial force of the wall which it supports.
Suitable materials for the fabrication of the tubular stmt would include silver, tantalum, stainless steel (316 L), gold, titanium, NiTi alloy or any suitable plastic materials such as thermoplastic polymers. Any medically-suitable metal which is capable of yielding plastically under the typical forces of a balloon catheter could also be employed.
Alternatively, the stmt may be made of a radioactive material or irradiated with a radioactive isotope. The radioactive isotope may be a beta particle emitting radioisotope. By using a stmt made of the radioactive material, cancer cells in and around the stmt can be deactivated or killed.
Alternatively, the stmt can be coated with materials that prevent cell overgrowth. The stmt may be coated with an anticoagulating medication substance, such as heparin, and/or a bioabsorbable material.
Accordingly, when the stmt is used in a blood vessel, blood clotting can be prevented. Also, the stmt may have pores, indentations or a roughened surface capable of absorbing or retaining a drug therein/thereon for slowly releasing the same over time. Thus, when the stmt with a drug is implanted in the body lumen, the drug can slowly released in the body lumen. To enhance visibility of the stmt when viewed by various different medical imaging devices, the end rings can be formed from a radio-opaque material, such as gold, silver or platinum, which allows both ends of the stmt to be clearly visible through a medical imaging device during or after implantation of the stmt within a body lumen of the patient.
The stmt is preferably formed by laser cutting technology wherein the pattern is cut into a cylindrical section of the appropriate material. Other suitable methods may be used, for example, the stmt can be formed by an etching technique. Namely, a pattern of the rings and the interconnecting members are coated on a cylindrical metal member, which is etched in an acid solution. Then, un-coated portions are removed.
The thickness of the material, i.e the stmt's tubular wall thickness is on the order of about 0.05-0.2mm. The cross-sectional configuration of the material can be varied, although it will likely depend upon the manner in which the stmt is manufactured. For, example, using laser cutting on a piece of tubular material, the resulting members which are disposed in the circumferential direction will have roughly rectangular cross-sections while the members generally parallel to the longitudinal axis will likely have a slightly trapezoidal cross-section if the axis of the laser intersects the axis of the tubular material. A more rectangular cross-section would be obtainable with an appropriate offset of the laser's axis.
Having described this invention with regard to specific embodiments, it is to be understood that the invention has been described with respect to a limited number of embodiments. It will be appreciated that many variations, modifications and other applications of the invention may be made. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.
Interconnecting mechanism 128 comprises a first interconnecting member 128A
disposed between portions of adjacent expandable elements 16 of adjacent rings 12,12' and a second interconnecting member 128B disposed between portions of adjacent expandable elements 16 of adjacent rings 12,12'. The interconnecting members 128A,128B are integrally formed, fused or otherwise attached to each other. The cloverleaf design of the interconnecting members 128A,128B permits some local axial and circumferential expansion.
Interconnecting mechanism 130 comprises a first interconnecting member 130A
disposed between non-adjacent portions expandable elements 16 of adjacent rings 12',12 and a second interconnecting member 130B disposed between non-adjacent portions of adjacent expandable elements 16 of adjacent rings 12',12. Both the interconnecting members 130A,130B are N-shaped with their central leg portions crossingly attached. The interconnecting mechanisms 128,130 serve to increase the metal coverage, which will give more radial support and reduce the gaps between the struts/members, and can be designed to limit the radial expansion of the stmt so as to reduce the risk of stmt rupture by overinflation.
Fig. 16A shows a complete portion of a stent 140 (as laid flat) in accordance with a prototype of the present invention which is similar to the stmt portion 100 of Fig. 9 except that the expandable element 16 includes an additional circumferentially-oriented, over-parallel functional unit 20E. In addition, adjacent rings 12 are interconnected by a relatively short interconnecting member 142 to facilitate axial flexing. As can be seen, the stmt 140 provides substantial metal coverage when in its unexpanded state shown in Fig. 16A. The length L
=15.851mm and the distance C, which is the circumference is 4.393mm which results in a tubular stmt of approximately 1.37mm diameter. Fig. 16B illustrates an enlarged section of the stmt 140 of Fig. 16A. For reference purposes, Table 2 sets out the length L and radius R
dimensions (in mm) as measured:
Li LZ L3 La Ls L6 L~ R, Rz R3 Ra Rs R6 R~ Rs 0.8460.5630.3980.070.080.080.080.140.140.090.1650.050.060.1310.05 Table 2 The thickness of the material, i.e the stmt's tubular wall thickness is on the order of about 0.05-0.2mm.
Fig. 16C shows a portion of the stmt 140 in its expanded form as 140'. The expandable elements 16' have started to move diagonally and the axially-oriented functional units 20A' have expanded circumferentially to an "under-parallel" disposition. The rings 12' are prevented from separation by interconnecting members 142'. The expansion causes a tensile force component to be exerted along the expandable element 16', causing the individual functional units 20E'expand from their originally over-parallel disposition to parallel as shown in Fig. 16C and with sufficient expansion, to an under-parallel disposition.
Table 3 sets out the results of radial expansion testing the stent 140.
STENT DIAMETER LENGTH SHORTENING METAL
COVERAGE
(mm) (inches) (mm) (%) (%) 1.37 0.054 16 -- 52 3 0.118 16 0 24 3.5 0.138 16 0 20 4 0.157 16 0 17 Table 3 As can be seen from Table 3, the length of the stmt 140 remains the same over the range from its nominal, unexpanded diameter of 1.37mm to 4mm. These results can be compared with the results of Uni-Cath, Inc.'s Iris stmt as shown in Table 1, which show stmt length reduction as expansion increases. In addition, the stmt 140 retains acceptable metal coverage over the 5 expansion range.
The self compensating principle as described above with respect to the diagonally-oriented functional element 20C of Fig. 3E, can also be combined with the aforementioned over-parallel concept for axially- or circumferentially-oriented functional elements 20D,20E and arranged to optimize axially flexibility for ease of deployment without significant detriment 10 to strength of the expanded stmt after deployment. To illustrate the combination of these principles, there is shown in Fig. 17 a stmt 150 comprising a plurality of similar rings 152.
Each ring 152 consists of an alternating series of over-parallel functional elements 20G which are arranged diagonally with respect to the longitudinal axis 14 of the stmt 150. Each ring 152 forms a separate oblique cylinder and is not part of a "helical winding", and accordingly, the 15 end rings 152 are not as prone to splaying as would be the case with a free end portion of a helical winding.
As with the stent 50 of Fig. 4B, adjacent rings 152 are interconnected with an interconnecting member 154 between opposed bendable joints 156. The interconnecting members can be attached in an number of ways, such as for example, bottom-to-bottom as shown, apex-to-apex as shown in Fig. 16A, or apex-to-bottom as shown in Fig. 10. Similarly, to increase the flexibility as aforesaid, the length of the connecting member 164 between adjacent rings 162 can be reduced as aforesaid and as illustrated in Fig. 18.
The diagonally-oriented functional unit 20C concept can also be employed in a stmt without use of the over-parallel feature of Fig. 3G to substantially the same advantage. By way of example, stmt 170 of Fig. 19 is constructed of a plurality of obliquely disposed rings 172.
Each ring 172 consists of a series of circumferentially expandable elements 16 in this case connected to the next expandable element in the series by a diagonally-disposed functional unit 20C. Each expandable element comprises one or more diagonally-oriented functional units 20C' which in this case are disposed generally at right angles to the diagonally-disposed functional unit 20C. Selected apexes of adjacent bendable joints 176 of adjacent rings 172 may be attached at 174 to form the ring interconnections or the interconnecting can be accomplished in any of the manners discussed in this application or in Applicant's aforementioned International Application No. PCT/CA99/00632.
The stems described herein are preferably fabricated from biocompatible, low memory, more plastic than elastic material to permit the stmt to be expanded and deformed, yet sufficiently rigid to permit the stmt to retain its expanded and deformed configuration with an enlarged diameter and also to resist radial collapse.
Typically, stems in accordance with the teachings herein may be expanded up to about four times their original constricted diameters yet still have desirable properties of good axial flexibility in the constricted state and resistance to radial collapse and comprehensive wall support in the expanded state. Accordingly, stems may be provided for example in nominal diameters d of about lmm, l.Smm, and 2mm which, depending on the specific structure, may be expanded to 4mm, 6mm or 8mm, respectively, which should enable a minimum number of stems to be employed in most situations. It should be borne in mind that the stems of the present invention are operable over their entire range because they deform substantially continuously under application of an radially outwardly directed force. Upon removal of the force, deformation halts and the stmt remains sufficiently rigid to withstand the radial force of the wall which it supports.
Suitable materials for the fabrication of the tubular stmt would include silver, tantalum, stainless steel (316 L), gold, titanium, NiTi alloy or any suitable plastic materials such as thermoplastic polymers. Any medically-suitable metal which is capable of yielding plastically under the typical forces of a balloon catheter could also be employed.
Alternatively, the stmt may be made of a radioactive material or irradiated with a radioactive isotope. The radioactive isotope may be a beta particle emitting radioisotope. By using a stmt made of the radioactive material, cancer cells in and around the stmt can be deactivated or killed.
Alternatively, the stmt can be coated with materials that prevent cell overgrowth. The stmt may be coated with an anticoagulating medication substance, such as heparin, and/or a bioabsorbable material.
Accordingly, when the stmt is used in a blood vessel, blood clotting can be prevented. Also, the stmt may have pores, indentations or a roughened surface capable of absorbing or retaining a drug therein/thereon for slowly releasing the same over time. Thus, when the stmt with a drug is implanted in the body lumen, the drug can slowly released in the body lumen. To enhance visibility of the stmt when viewed by various different medical imaging devices, the end rings can be formed from a radio-opaque material, such as gold, silver or platinum, which allows both ends of the stmt to be clearly visible through a medical imaging device during or after implantation of the stmt within a body lumen of the patient.
The stmt is preferably formed by laser cutting technology wherein the pattern is cut into a cylindrical section of the appropriate material. Other suitable methods may be used, for example, the stmt can be formed by an etching technique. Namely, a pattern of the rings and the interconnecting members are coated on a cylindrical metal member, which is etched in an acid solution. Then, un-coated portions are removed.
The thickness of the material, i.e the stmt's tubular wall thickness is on the order of about 0.05-0.2mm. The cross-sectional configuration of the material can be varied, although it will likely depend upon the manner in which the stmt is manufactured. For, example, using laser cutting on a piece of tubular material, the resulting members which are disposed in the circumferential direction will have roughly rectangular cross-sections while the members generally parallel to the longitudinal axis will likely have a slightly trapezoidal cross-section if the axis of the laser intersects the axis of the tubular material. A more rectangular cross-section would be obtainable with an appropriate offset of the laser's axis.
Having described this invention with regard to specific embodiments, it is to be understood that the invention has been described with respect to a limited number of embodiments. It will be appreciated that many variations, modifications and other applications of the invention may be made. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.
Claims (28)
1. An intravascular tubular stent expandable between a first, constricted state and a second state of greater expanded diameter; said stent comprising in its constricted state:
a plurality of radially expandable rings each formed of a plurality of circumferentially extendable elements, each circumferentially extendable element comprising:
at least one first functional unit having a bendable joint from which a pair of arms extend so as to form therebetween an elongate opening disposed in a first direction; and a plurality of second functional units each of which having a bendable joint from which a pair of arms extend so as to foam therebetween an elongate opening disposed in a second direction;
said first direction being substantially perpendicular to said second direction;
and each pair of adjacent radially expandable rings being connected to each other at at least one location.
a plurality of radially expandable rings each formed of a plurality of circumferentially extendable elements, each circumferentially extendable element comprising:
at least one first functional unit having a bendable joint from which a pair of arms extend so as to form therebetween an elongate opening disposed in a first direction; and a plurality of second functional units each of which having a bendable joint from which a pair of arms extend so as to foam therebetween an elongate opening disposed in a second direction;
said first direction being substantially perpendicular to said second direction;
and each pair of adjacent radially expandable rings being connected to each other at at least one location.
2. The intravascular tubular stent as claimed in claim 1, wherein said first functional unit is oriented such that the elongate opening is disposed generally parallel to the longitudinal axis of the tubular stent.
3. The intravascular tubular stent as in claim 1, wherein said first functional unit is oriented such that the elongate opening is disposed diagonally with respect to the longitudinal axis of the tubular stent.
4. The intravascular tubular stent as claimed in claim 1, wherein each expandable ring is substantially identical to each adjacent ring.
5.~The intravascular tubular stent as claimed in claim 1, wherein each expandable ring is the mirror-image in the axial direction to each adjacent ring.
6. The intravascular tubular stent as claimed in any one of claims 1 to 3, wherein each expandable ring is disposed obliquely with respect to the longitudinal axis of the stent.
7. The intravascular tubular stent as claimed in any one of claims 1 to 6, wherein said pair of arms from each said second functional unit converge toward their ends distal its bendable joint so as to form a converging opening.
8. The intravascular tubular stent as claimed in any one of claims 1 to 7, wherein said pair of arms from each said first functional wait converge toward their ends distal its bendable joint so as to form a converging opening.
9. The intravacular tubular stent as claimed is any one of claims 1 to 6, wherein said pair of arms from each said second functional unit extend generally parallely from its bendable joint so as to form a generally constant width opening.
10. The intravascular tubular stent as claimed is any one of claims 1 to 7, wherein said pair of arms from tech said first functional unit extend generally parallely from its bendable joint so as to form a generally constant width opening.
11. The intravascular tubular stent as claimed in claim 1, wherein at least one interconnecting member extends between a portion of one ring and an adjacent portion of an adjacent ring.
12. The intravascular tubular stent as claimed is claim 11, wherein the at least one interconnecting member extends between a bendable joint of one extendable element to the bendable joint of another extendable element is an adjacent ring.
13. The intravascular tubular stent as claimed in claim 12, wherein said one extendable element is longitudinally adjacent the another extendable element in the adjacent ring.
14. The intravascular tubular stent as claimed in claim 1, wherein adjacent rings are connected by connecting mechanisms disposed to expand into the largest gaps produced between said rings upon radial expansion.
15. The intravascular tubular stent as claimed in claim 14, wherein the connecting mechanisms limit the longitudinal and/or radial expansion of the stent
16. The intravascular tubular stent as claimed in claim 14, wherein the connecting mechanisms extend between a portion of an extendable element of one ring and a portion of a non-adjacent extendable element of as adjacent ring.
17. The intravascular tubular stent as claimed is claim 3, wherein at least one interconnecting member extends between a portion of one ring and an adjacent portion of as adjacent ring.
18. The intravascular tubular stent as claimed is claim 17, wherein said interconnecting member is disposed at substantially the same diagonal orientation as the elongate opening of said first functional unit.
19. The intravascular tubular stent as claimed is claim 1, wherein radial expansion of said scent results is substantially no shortening in the length of said stent
20. An intravascular tubular stent expandable between a first, constricted state and a second state of greater expanded diameter; said stent comprising in its constricted states:
a plurality of radially expandable rings each formed of a plurality of circumferentially extendable elements, each circumferentially extendable element comprising at least one functional unit having a bendable joint from which a pair of arms extend so as to form an elongate opening therebetween;
each said expandable ring being disposed at an oblique angle with respect to the longitudinal axis of the stent, and each pair of adjacent radially expandable rings being connected to each other at at least one location.
a plurality of radially expandable rings each formed of a plurality of circumferentially extendable elements, each circumferentially extendable element comprising at least one functional unit having a bendable joint from which a pair of arms extend so as to form an elongate opening therebetween;
each said expandable ring being disposed at an oblique angle with respect to the longitudinal axis of the stent, and each pair of adjacent radially expandable rings being connected to each other at at least one location.
21. The intravascular tubular stent as claimed in claim 20, wherein said elongate opening is disposed generally parallel to the longitudinal axis of the tubular stent.
22. The intravascular tubular stent as claimed in claim 20, wherein said functional wait is oriented such that the elongate opening is disposed diagonally with respect to the longitudinal axis of the tubular stem
23. The intravascular tubular stent as claimed in claim 22, wherein said functional unit is oriented such that the elongate opening is disposed substantially perpendicularly with respect to the oblique angle at which each said expendable ring is disposed.
24. The intravascular tubular stent as claimed in claim 20, wherein at least one interconnecting member extends between a portion of one ring and an adjacent portion of an adjacent ring.
25. The intravascular tubular stent as claimed in claim 24, wherein the at least one interconnecting member extends between a bendable joint of one extendable element to the bendable joint of another extendable element in as adjacent ring.
26. The intravascular tubular start in claimed in claim 25, wherein said interconnecting member is disposed at substantially the same diagonal orientation as the elongate opening of the functional unit.
27. The intravascular tubule stent as claimed in any one of claims 20 to 26, wherein said pair of arms from each said second functional unit converge toward their ends distal its bendable joint so as to form a converging opening.
28. The intravascular stent as claimed in any one of claims 20 to 26, wherein said pair of arms from each said second functional unit extend generally parallely from its bendable joint so as to form a generally constant width opening.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002358449A CA2358449A1 (en) | 1999-01-22 | 2000-01-21 | Expandable intravascular tubular stents |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11687799P | 1999-01-22 | 1999-01-22 | |
| US60/116,877 | 1999-01-22 | ||
| CAPCT/CA99/00632 | 1999-07-12 | ||
| PCT/CA1999/000632 WO2000042945A1 (en) | 1999-01-22 | 1999-07-12 | Expandable endovascular medical tubular stent |
| CA002358449A CA2358449A1 (en) | 1999-01-22 | 2000-01-21 | Expandable intravascular tubular stents |
| PCT/CA2000/000035 WO2000042946A1 (en) | 1999-01-22 | 2000-01-21 | Expandable intravascular tubular stents |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2358449A1 true CA2358449A1 (en) | 2000-07-27 |
Family
ID=27171603
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002358449A Abandoned CA2358449A1 (en) | 1999-01-22 | 2000-01-21 | Expandable intravascular tubular stents |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2358449A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007093031A1 (en) * | 2006-01-23 | 2007-08-23 | Daniel Gelbart | An axially-elongating stent and method of deployment |
-
2000
- 2000-01-21 CA CA002358449A patent/CA2358449A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007093031A1 (en) * | 2006-01-23 | 2007-08-23 | Daniel Gelbart | An axially-elongating stent and method of deployment |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6607554B2 (en) | Universal stent link design | |
| EP1796588B1 (en) | Optimized flex link for expandable stent | |
| JP5259746B2 (en) | Lumen prosthesis | |
| US5776183A (en) | Expandable stent | |
| US7540881B2 (en) | Bifurcation stent pattern | |
| US8328864B2 (en) | Stent having phased hoop sections | |
| US7128756B2 (en) | Endoprosthesis having foot extensions | |
| US7867272B2 (en) | Stent having twist cancellation geometry | |
| US8337544B2 (en) | Endoprosthesis having flexible connectors | |
| US20050182477A1 (en) | Intraluminal stent and graft | |
| WO2003049642A1 (en) | Non-foreshortening stent | |
| EP1703856A2 (en) | Longitudinally flexible stent | |
| EP1152710A1 (en) | Expandable intravascular tubular stents | |
| WO2000042945A1 (en) | Expandable endovascular medical tubular stent | |
| CA2358449A1 (en) | Expandable intravascular tubular stents | |
| CA2586095C (en) | Stent having twist cancellation geometry | |
| WO2002051335A1 (en) | Implantable intravascular stent |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |