STENT

Abstract

The disclosure provides a tubular stent comprising at least three primary elongate columns disposed around a circumference of the stent. The primary elongate columns substantially parallel to a longitudinal axis of the stent. The stent further comprises at least two non-linear struts disposed between each pair of circumferentially adjacent primary columns, wherein each strut extends between the circumferentially adjacent primary columns. The stent is configured to adopt a first, unexpanded configuration and a second, expanded configuration in which the stent has a greater diameter than in the first, unexpanded configuration.

Claims

1. A tubular stent comprising: at least three primary elongate columns disposed around a circumference of the stent, and substantially parallel to a longitudinal axis thereof, and at least two non-linear struts disposed between each pair of circumferentially adjacent primary columns, wherein each strut extends between the circumferentially adjacent primary columns, wherein the stent is configured to adopt a first, unexpanded configuration and a second, expanded configuration in which the stent has a greater diameter than in the first, unexpanded configuration.

2. The tubular stent according to claim 1, wherein the stent defines a longitudinal length of between 1 and 500 mm.

3. The tubular stent according to claim 1, wherein the tubular stent comprises between three and four primary columns.

4. The tubular stent according to claim 1, wherein, in the first, unexpanded configuration, the stent has an internal diameter of between 0.5 and 50 mm.

5. The tubular stent according to claim 1, wherein the stent is configured to convert from the first, unexpanded configuration to the second, expanded configuration, and when the stent converts from the first, unexpanded configuration to the second, expanded configuration, the stent is configured to expand to a diametral strain of at least 50%.

6. The tubular stent according to claim 1, wherein the stent is configured to convert from the second, expanded configuration to a third, recoiled configuration in which the stent has a greater diameter than in the first, unexpanded configuration and a smaller diameter than in the second, expanded configuration, and when the stent converts from the second, expanded configuration to the third, recoiled configuration, the stent is configured to have a radial recoil of less than 50%.

7. The tubular stent according to claim 1, wherein the primary columns and struts have a thickness between 10 and 1,000 μm.

8. The tubular stent according to claim 1, wherein the struts each comprise a first portion and a second portion, wherein in the first, unexpanded configuration, the first and second portions are substantially linear or geodesic, and the first and second portions of each strut define a first angle therebetween of between 0.5° and 189.5°.

9. The tubular stent according to claim 8, wherein the first portion of the strut and a substantially adjacent primary column define a second angle therebetween, and the second portion of the strut and a substantially adjacent primary column define a third angle therebetween, and in the first, unexpanded configuration, the second and third angles are both between 0.25° and 89.75°.

10. The tubular stent according to claim 8, wherein the first and second portions of the strut directly interconnect.

11. The tubular stent according to claim 8, wherein, in the first, unexpanded configuration, the strut defines a v-shape.

12. The tubular stent according to claim 8, wherein the strut comprises a bent portion disposed between the first and second portions, wherein the bent portion is curved.

13. The tubular stent according to claim 8, wherein the first portion comprises a first radial side which defines a curved section substantially adjacent to a first primary column in the circumferentially adjacent pair of primary columns, and the second portion comprises a first radial side which defines a curved section substantially adjacent to the second primary column in the adjacent pair of primary columns.

14. The tubular stent according to claim 1, wherein the struts have a width between 10 and 1,000 μm.

15. The tubular stent according to claim 1, wherein the primary columns comprise a proximal end and a distal end, wherein the proximal ends of the primary columns define the proximal end of the stent and the distal ends of the primary columns are spaced apart from the distal end of the stent.

16. The tubular stent according to claim 1, wherein the primary columns have a width between 10 and 1,000 μm.

17. The tubular stent according to claim 1, wherein a first non-linear strut is disposed between each pair of circumferentially adjacent primary columns, and is substantially adjacent to the proximal ends thereof, and a second non-linear strut is disposed between each pair of circumferentially adjacent primary columns, and is substantially adjacent to the distal ends thereof.

18. The tubular stent according to claim 1, wherein the stent comprises at least three secondary elongate columns disposed around the circumference of the stent, and substantially parallel to the longitudinal axis thereof, wherein the secondary columns intersect the struts.

19. The tubular stent according to claim 18, wherein the secondary columns comprise a proximal end and a distal end, wherein the distal ends of the secondary columns define the distal end of the stent, and the proximal ends of the secondary columns are spaced apart from the proximal end of the stent.

20. The tubular stent according to claim 1, wherein the stent consists of the primary columns and the struts, and optionally a drug-eluting coating and/or a polymer or fabric coating disposed around the outer circumference of the stent.

21. The tubular stent according to claim 1, wherein the stent comprises a polymeric material and/or a metal.

Description

[0064] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying FIGS., in which:—

[0065] FIG. 1 is a three-dimensional representation of stents defining (a) angular and (b) curved chevron-shaped cell structures;

[0066] FIG. 2 shows a line of repeating units of the angular chevron-shaped cell stent of FIG. 1a;

[0067] FIG. 3 shows a line of repeating units of the curved chevron-shaped cell stent of FIG. 1b;

[0068] FIG. 4a shows an isometric view of the stent of FIG. 1a; FIG. 4b shows an isometric view of the stent of FIG. 1b; and FIGS. 4c-g show isometric views of further stents in accordance with the present invention;

[0069] FIG. 5 shows contour plots for the stent shown in FIG. 4e in the (a) unexpanded, (b) fully expanded, and (c) fully recoiled states, when viewed along the longitudinal axis. The insert legend gives a measure of the effective stress state within the stent material based on polydioxanone (PDO) polymeric material;

[0070] FIG. 6 shows contour plots for the stent shown in FIG. 4e in the (a) unexpanded, (b) fully expanded, and (c) fully recoiled states, when viewed perpendicular to the longitudinal axis. The insert legend gives a measure of the effective stress state within the stent material based on polydioxanone (PDO) polymeric material;

[0071] FIG. 7 is a three-dimensional representation of an alternative stent;

[0072] FIG. 8 shows a portion of the stent of FIGS. 1b and 4b;

[0073] FIG. 9 is a virtual designs of a stent;

[0074] FIG. 10 shows the assembled ex-vivo setup of three stents showing balloon and the stents: (a) is the stent shown in FIG. 9, identified as Stent 1, (b) is the stent shown in FIG. 1a, identified as Stent 2, and (c) is the stent shown in FIG. 1c, identified as Stent 3;

[0075] FIG. 11 is an illustration, using Stent 3, of three regions at which structural parameters were extracted for the three stents. These regions coincide with proximal, central and distal regions of the stents, along the line of insertion in the occluded artery. For each region, two reference points were identified and kinematically tracked during the deformation;

[0076] FIG. 12 shows stent mechanics contour plots for the three stents showing stress distribution in the stents for (a) Stent 1, (b) Stent 2, and (c) Stent 3;

[0077] FIG. 13 shows evidence of dogboning from contour plots from the virtual testbed showing (a) significant dogboning of Stent 1 with D.sub.2>>D.sub.1, (b) limited dogboning for Stent 2, and (c) limited dogboning for Stent 3;

[0078] FIG. 14 is a graph comparing the structural parameters of Stents 1 to 3;

EXAMPLE 1—DESIGN OF A NEW STENT

[0079] A tubular stent 2a is shown in an unexpanded configuration in FIGS. 1a and 4a. The stent 2a comprises a proximal end 4 and a distal end 6, and a longitudinal axis extends therebetween. The tubular stent 2 has a substantially cylindrical cross-section with an internal diameter of about 2 mm, an outer diameter of about 3 mm and a total length of about 12 mm.

[0080] The stent 2a comprises four elongate columns 8, each column 8 comprising a proximal end 10 and a distal end 12. The proximal end 10 of each column 8 is angular, defining a point. Conversely, the distal end 12 of each column 8 is linear, defining a surface substantially perpendicular to the longitudinal axis of the stent 2a. The columns 8 have a depth of approximately 0.5 mm, a width of approximately 0.3 mm and a length of about 9.75 mm. The columns are disposed parallel to the longitudinal axis of the stent 2, and are evenly spaced around the circumference of the tubular stent 2. The proximal ends 10 of the columns 8 are level with and define the proximal end 4 of the stent 2. Conversely, the distal ends 12 of the columns 8 are spaced apart from the distal end 6 of the stent 2a.

[0081] As shown in FIG. 2, a bent strut 14 extends between adjacent columns 8a, 8b. The strut comprises a bent portion 20, a first portion 16, extending between the first column 8a and the bent portion 20, and a second portion 18, extending between the second column 8b and the bent portion 20. The first and second portions 16, 18 each define an angle α with the adjacent column 8a, 8b and an angle β with each other. In the embodiment shown in FIGS. 1 and 2, a is 31.31° and β is 62.62°. The first and second portions 16, 18 have a length of about 2.3 mm and have a width of about 0.3 mm and a depth of approximately 0.5 mm.

[0082] As shown in FIG. 1, four struts 14 extend circumferentially between each pair of circumferentially adjacent columns 8. A first strut 14a is disposed adjacent to the proximal ends 10 of the columns 8. Similarly, a second strut 14b is disposed a third of length along the columns 8, closer to the proximal ends 10 thereof. A strut 14c is located two thirds of length along the columns 8, closer to the distal ends 12 thereof. Finally, a fourth strut 14d is located adjacent to the distal ends 12 of the columns 8. The four struts 14 disposed between each pair of columns 8 are all parallel to each other. The bent portions 10 of all the struts 14 point towards the distal end 6 of the stent. In particular, the bent points 20d of the fourth strut 14d define the distal end 6 of the stent 2a.

[0083] The stent 2a shown in FIGS. 1a and 4a has an angular configuration i.e., as explained above, the proximal ends 10 of the columns 8 define points and the bent portions 20 also define points.

[0084] An alternative stent 2b is shown in FIGS. 1b and 4b, and FIG. 3 shows a line of repeating units for this stent 2b. The stent 2b has a substantially cylindrical cross-section with an internal diameter of about 2 mm, an outer diameter of about 3 mm and a total length of about 10 mm. In this embodiment, the columns define a length of about 7.5 mm. Additionally, in this embodiment, the angle α is 18.74° and the angle β is 37.48°. The first and second portions 16, 18 have a length of about 1.9 mm, and both the columns 8 and the struts 14 have a width of approximately 0.3 mm and a depth of approximately 0.5 mm.

[0085] This stent 2b is similar to the stent 2a shown in FIGS. 1a and 2 but has a curved configuration. Accordingly, in this embodiment, the proximal ends 10 of the columns 8 define curved surfaces. This curved portion of the design can be defined by the are length of the curved surface using the following equation:

Arc length=(θ/360)×π×D

θ is the angle shown in FIG. 8, and D is the diameter of the circle. The stent shown in FIGS. 1b and 4b has an arc length of 0.9877 mm, which is 32.75% of the circumference of the circle. However, it will be appreciated that the are length, and the portion of a circle the proximal end 10 of the column 8 defines will vary as the angles α and β vary.

[0086] Similarly, bent portions 20, where the first and second portions 16, 18 meet, also define curved surfaces which define 32.75% of the circumference of the circle. As shown in FIGS. 1b and 4b, a proximal radial side 28 of the first and second portions 16, 18 is curved adjacent to the column 8. A distal radial side 30 of the first and second portions 16, 18 is linear adjacent to the column 8 in the pictured stent, but it will be appreciated that in some embodiments the distal radial side of the first and second portions 16, 18 could be curved.

[0087] Alternative stents with angular configurations are shown in FIGS. 4c to 4g. These stents have been modified by changing the size of the columns, the number of columns, the size of the struts, the number of struts repeating in a longitudinal direction and/or the angles of α and β. Furthermore, the stents shown in FIGS. 4c and 4d comprise three (as opposed to four) columns 8.

[0088] Briefly, a stent 2c shown in FIG. 4c comprises three columns 8 and four pairs of struts 14 are disposed between each circumferentially adjacent pair of columns 8. The stent 2c has a length of 11.97 mm, an inner diameter of 1.5 mm and the struts 14 and columns 8 have a depth of 0.5 mm and a width of 0.3 mm, a is 37.69° and β is 75.38°.

[0089] A stent 2d shown in FIG. 4d comprises three columns 8 and four pairs of struts 14 are disposed between each circumferentially adjacent pair of columns 8. The stent 2d has a length of 12.01 mm, an inner diameter of 0.7 mm and the struts 14 and columns 8 have a depth of 0.5 mm and a width of 0.3 mm, α is 440 and β is 88°.

[0090] A stent 2e shown in FIG. 4e comprises four columns 8 and four pairs of struts 14 are disposed between each circumferentially adjacent pair of columns 8. The stent 2e has a length of 11.99 mm, an inner diameter of 1.7 mm and the struts 14 and columns 8 have a depth of 0.5 mm and a width of 0.3 mm, a is 20.01° and β is 44.01°.

[0091] A stent 2f shown in FIG. 4f comprises eight columns 8 and four pairs of struts 14 are disposed between each circumferentially adjacent pair of columns 8. The stent 2f has a length of 22.31 mm, an inner diameter of 2.9 mm and the struts 14 and columns 8 have a depth of 0.05 mm and a width of 0.05 mm, a is 5° and β is 10°.

[0092] A stent 2g shown in FIG. 4g comprises four columns 8 and ten pairs of struts 14 are disposed between each circumferentially adjacent pair of columns 8. The stent 2g has a length of 14 mm, an inner diameter of 4.21 mm and the struts 14 and columns 8 have a depth of 0.09 mm and a width of 0.03 mm, a is 89.5° and β is 179°.

[0093] A further alternative stent 2h is shown in FIG. 7. This stent 2h has an angular configuration, and is similar to the stent 2a depicted in FIGS. 1a and 4a. However, the stent further comprises four secondary columns 22, each secondary column 22 comprising a proximal end 24 and a distal end 26. The proximal end 24 of each secondary column 22 is angular, defining a point. The distal end 24 of each secondary column 22 is also angular, defining a point.

[0094] The secondary columns 22 have a depth and width of approximately 0.5 mm and a length of about 9.75 mm. The secondary columns 22 are disposed parallel to the longitudinal axis of the stent 2, and are evenly spaced around the circumference of the tubular stent 2, wherein each secondary column 22 is evenly spaced between a pair of primary columns 8. Accordingly, the secondary columns 22 intersect the bent portions of the stents 14.

[0095] The proximal ends 24 of the secondary columns 22 are spaced apart from the proximal end 4 of the stent 2. Conversely, the distal ends 26 of the secondary columns 22 define the distal end 6 of the stent 2.

[0096] While the distal ends 12 of the columns 8 are shown as linear in the FIGS., it will be appreciated that the stents could be modified such that the distal end 12 is angular or curved.

EXAMPLE 2—COMPUTATIONAL ASSESSMENT OF THE PROPOSED STENTS' STRUCTURAL RESPONSE

Methods

[0097] Finite element analysis (FEA) computational studies were conducted on several stent designs some based on more traditional stent types in comparison with the proposed stent design. Out of different stents studied, the angular chevron-shaped cell stent and curved chevron-shaped cell stent performed consistently, in comparison with existing stents.

[0098] This study was carried out using a virtual testing framework developed by the inventors, whose computational engine is based on a finite element modelling scheme. The framework was configured to model deployment of the stent using a balloon catheter during percutaneous transluminal angioplasty (PCTA). Accordingly, the framework modelled an unexpanded stent as being disposed around a balloon catheter. The balloon was then inflated up to 0.97 mm radial displacement over 0.45 seconds, held at maximum radial expansion for 0.1 second and then deflated at the same over 0.45 seconds to its initial diameter. During the procedure, time-dependent kinematic and kinetic outputs were recorded, and post-test were collated and used to assess the structural performance of the stent. The studies were carried out using a stent comprising a polydioxanone (PDO) polymeric material. The computational studies comprised only the stent design and a balloon structure. This representative volume element of the coronary angioplasty system was chosen to comprise of only these two materials to reduce the computational cost for the study and emphasize solely the impact of the stent geometries on the stent design.

[0099] The structural performance was assessed based on accepted stent mechanical response parameters, namely: (1) radial recoil, (2) longitudinal retraction, (3) foreshortening, (4) maximum stent stress and (5) maximum strain. The stent parameters are objective measures of the structural response of the stent with respect to the desired stent expansion and deflation mechanics.

1. Radial Recoil

[0100] Radial recoil percentage (R.sub.recoil) is a percentage of the ratio of change in internal diameter of the stent following deflation of the balloon in comparison to its fully expanded internal diameter. It may be calculated using the following formula:

[00001]$R_{r\mathrm{ecoil}}=\frac{{\mathrm{ID}}_{\mathrm{expanded}}-{\mathrm{ID}}_{r\mathrm{ecoiled}}}{{\mathrm{ID}}_{\mathrm{expanded}}}\times 100\%$

Where ID.sub.expanded is the internal diameter of the stent when it is in the expanded state and ID.sub.recoiled is the internal diameter of the stent after the balloon has deflated.

[0101] It is desirable for the radial recoil percentage to be minimised, preferably to within approximately 10%.

2. Longitudinal Retraction

[0102] Longitudinal retraction (L.sub.retraction) is a measure of the ratio of change in the total axial stent length when expanded, compared to the original length of the unexpanded stent. It may be calculated using the following formula:

[00002]$L_{re\mathrm{traction}}=\frac{L_{u\mathrm{nexpanded}}-L_{\mathrm{expanded}}}{L_{\mathrm{unexpanded}}}\times 100\%$

L.sub.unexpanded and L.sub.expanded refer to the axial length of the stent in the unexpanded and expanded configurations, respectively.

[0103] It is also desirable for the longitudinal retraction to be minimised, preferably to within approximately 10%.

3. Foreshortening

[0104] Foreshortening (F.sub.sh) is related to the radial recoil percentage and refers to the ratio of the change in axial length of the stent between the recoiled position and the fully expanded position. It gives an indication of the lateral recoil of the stent following deflation of the balloon. It may be calculated using the following formula:

[00003]$F_{sh}=\frac{L_{recoiled}-L_{\mathrm{expanded}}}{L_{\mathrm{expanded}}}\times 100\%$

L.sub.recoiled refers to the axial length of the stent after the balloon has deflated.

[0105] It is also desirable for the foreshortening to be minimised, preferably to within approximately 10%.

4. Maximum Stent Stress

[0106] Maximum stent stress is a measure of the largest stress that the stent can support under the effect of an inflating balloon. It represents the maximum average stress state within the balloon. It also gives an indication of the load-bearing capacity of the stent. For this study the stress recorded was von Mises stress.

[0107] This is an important measure as it illustrates the possibility of the stent to fail/damage during the balloon inflation process. A comparison of this stress with say the yield stress or ultimate tensile strength of the test material (PDO for example) will help you know if the effective stress experienced by the stent material is ‘dangerously’ close to the failure load of the test material. For such cases, the stent will be highly susceptible to failure which is not good.

[0108] It is not the same for all the stent parts because the stent is a complex ‘mesh-like structure’ so the distribution of load within them will be different hence leading to different stress states shown from the computational framework.

[0109] This structural response helps select which material, design combination and inflating pressure that will be suitable for the coronary angioplasty while ensuring the structure is still intact and not susceptible to failure.

[0110] It is desirable for the maximum stent stress to be maximised, preferably up to the yield stress of the stent material.

5. Maximum Diametral Strain

[0111] Maximum diametral strain (Øε) is a measure of the maximum strain experienced by the stent following the balloon deployment. It is a structural strain measured radially along the diameter of the stent. It is an indicator of the ability of the stent to support the imposed balloon pressure without structural collapse of the stent due to tensile failure in one of the struts. Higher strain without localised damage/over-stretching of the stent is most desirable. It may be calculated using the following formula:

[00004]${\mathrm{\varnothing \epsilon }}_{\max }=\frac{{\varnothing }_{\mathrm{expanded}}-{\varnothing }_{\mathrm{unexpanded}}}{{\varnothing }_{\mathrm{expanded}}}\times 100\%$

Where Ø.sub.expanded and Ø.sub.unexpanded are the expanded and unexpanded stent internal diameters, respectively.

[0112] It is also desirable for the maximum diametral strain to be maximised.

Results

[0113] FIGS. 5 and 6 show the contour plots from the virtual testing scheme for a stent in the three deformation states (unexpanded, expanded and recoiled). The legend gives a measure of the effective stress state within the stent material based on polydioxanone (PDO) polymeric material. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Calculated structural stent parameters Maximum Radial Longitudinal Diametral Maximum Stent Recoil Retraction Foreshortening Strain Stress Angular chevron stent, 9.94% 8.17% 2.60% 128.86% 81.43 MPa as shown in Figures 1a and 4a Curved chevron stent, 10.45% 15.48% 5.40% 206.08% 71.7 MPa as shown in Figures 1b and 4b

[0114] Across all tested stent structural parameters, except maximal diametral strain, the angular chevron stent seemed to out-perform the curved chevron stent. The former also meets with the requirements for a good stent design and compares favourably with metallic stents in all parameters.

[0115] The present design compared favourably to commercially available stents. For instance, in silico studies done by Schiavone et al. (2017) show recoiling effect for commercial stents, Xience was 11% and for Elixir DESolve, which is fully polymeric was 20%.

[0116] The angular chevron cell experienced just over 100% maximum diametral strain, unlike the curved chevron cell stent which experienced over 200% strain. This indicates that the curved chevron stent has a higher expansion potential and can be used in cases were larger strains are required. Both stents have structural values in line with the structural stent parameters for commercially available stents.

EXAMPLE 3—FURTHER COMPUTATIONAL ASSESSMENT OF THE PROPOSED STENTS' STRUCTURAL RESPONSE

Methods

[0117] Three stents were designed in SolidWorks and imported into the virtual testbed for analysis. The stents are shown in FIG. 9 and FIGS. 1a and 1b. The stent shown in FIG. 9, hereinafter identified as “Stent 1”, has six struts and the angle at position a is 15°. The stents shown in FIGS. 1a and 1b are described above, and hereinafter are identified as “Stent 2” and “Stent 3”, respectively.

[0118] The stents were set up as shown in FIG. 10 for virtual testing. FIG. 11 shows the regions where structural parameters were extracted and FIG. 12 shows stent mechanics contour plots which were generated for the three stents.

Dogbone Assessment

[0119] The inventors reviewed the dogbone response of the stents, as its vital that stents that should be deployed within an occluded artery must show limited dogbone effects. The contour plots for all three stents (without perspective) are shown in FIG. 13.

[0120] As shown in the contour plots, Stent 1 is subject to asymmetric dogboning effects with only the distal ends showing least expansion while the proximal and medial/central regions deformed comparably. This sort of stent mechanics is not suitable for a stent for use within the arteries as this will lead to differential/variable scaffolding effects at different regions of the arteries.

Structural Mechanics

[0121] Structural mechanics were extracted using the reference nodes at the distal, central and proximal regions. The following structural parameters were extracted: [0122] Elastic (or Radial) Recoil [0123] Longitudinal retraction [0124] Foreshortening [0125] Dogboning [0126] Stent mechanics assessment—which assesses if stent is suitable for in vivo use [0127] Damage assessment index: has any of the stent's struts damaged or not.

[0128] The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Comparison of structural parameters for three stent designs Stent Type Structural Parameters Units Stent 1 Stent 2 Stent 3 Maximum radial mm 2.6 1.3 1.9 displacement Maximum Diametral Strain % 274.2 137.8 199.5 Elastic Recoil (Average) % 31.9 6.5 12.5 Foreshortening (Average) % 2.9 2.7 7.0 Longitudinal % 3.5 7.0 7.0 Retraction (Average) Dogboning (Maximum) % 23.0 11.9 4.7 Damage Assessment — PASSED PASSED PASSED Index (DAI) Stent Mechanics — NO YES YES Assessment (SMA) Ranking — 3.sup.rd 1.sup.st 2.sup.nd
A comparison of the structural parameters is shown in FIG. 14.

Findings

[0129] The numerical study has shown the following: [0130] a) Stents 2 and 3 (Curved and Straight versions) are suitable for deployment within the occluded artery without experiencing any damage of the struts even up to 130% diametral strain. [0131] b) Stent 1 behaved poorly in terms of structural parameters such as elastic radial recoil (32%) in comparison with the Stents 2 and 3 which showed values of 6.5% and 12.5% respectively for the Straight and Curved Chevron versions. [0132] c) Also, the Stent 1 showed significant dogboning with maximum values of 23% whilst Stents 2 and 3 showed values of 12% and 5% respectively. Dogboning is a feature of many stents and the objective is to make sure it is minimized as such high values as 23% will lead to variable scaffolding of the artery after stent deployment which can lead to structural and arterial failures in the long term. [0133] d) All three stents showed acceptable longitudinal retraction and foreshortening properties. [0134] e) Stent 1 showed the largest diametral expansion experiencing as much as 274% strain whilst Stent 2 gave the least value of 138% and Stent 3 a value of 200%. [0135] f) The stent-to-artery contact area is lower for Stents 2 and 3 than that of Stent 1 which significantly improves their use as it will allow for less arterial contacts and consequent arterial stress during the deployment.

CONCLUSIONS

[0136] The novel design of Stents 2 and 3 makes them significantly better than existing competitor stents since they: [0137] a. Limit dogboning effects; [0138] b. Limit elastic recoil, an essential feature for effective scaffolding of the artery post-deployment of the stent; and [0139] c. Limit the stent-to-artery contact area allowing for better stent mechanics, less arterial contacts and consequent reduction in arterial stress during stent deployment.