TECHNICAL FIELD

[0001] The present invention, in general, relates to stents, stent systems, and methods for delivery and uses thereof. Particularly, the invention relates to a branch vessel ostial stent with an ostial stent delivery system. More particularly, the present invention relates to a branch vessel ostial stent with an ostial stent delivery system that aids the precise deployment of the stent at the ostium of the branch vessel with no or minimal unwanted protrusion of stent or part of the stent thereof in the main vessel.

BACKGROUND ART

[0002] Percutaneous transluminal coronary angioplasty (PTCA) is a procedure that is the well-established standard of care for the treatment of blockages in the coronary arteries. The said procedure involves the deployment of the stent in the diseased segment of the blood vessel. A stent is a type of endoprosthesis device, wherein it can be placed or implanted within a vein, artery, or other body lumens for treating occlusions, stenoses, dissections, or aneurysms of a vessel by reinforcing the wall of the vessel or by expanding the vessel. However, one of the drawbacks of conventional stents is that they are difficult to position in and around vessel bifurcations (branch points). Often treatment of diseased vessels at or near bifurcations requires the deployment of a stent in both the main vessel and a branch vessel at the bifurcation.

[0003] Specifically, in a situation wherein a branch arises from the main vessel at an angle (suppose 45-degree), and it is intended to place a stent at the ostium of said branch, then placing a cylindrical stent at the ostium leads to two possibilities: one, the edge of the stent towards the carina will protrude into the main vessel, and secondly, if the stent is prevented from protruding into the main vessel, then said stent will miss the proximal portion of the overhanging edge (i.e., edge opposite to the carina) of the stented branch vessel.

[0004] In the state-of-the-art literature, US20040267352A1 teaches a stent with protruding branch portion for bifurcated vessels, wherein the branch portion is at least partially detachable from the stent body. This system is meant to deploy two stents at bifurcation points, i.e., one in the main vessel and another in the branch vessel. Said system may not be suitable to deploy the only stent at the ostium of the branch vessel, because the configuration of branch vessel stent is like the usual cylindrical stent which otherwise can also be placed without the use of this special system. As the branch vessel arises at some angle with respect to the main vessel, the use of the typical cylindrical stent at the branch vessel ostium poses two problems (except in the situation wherein the branch vessel arises at 90-degrees from the main vessel). First, if the stent covers the ostium completely, then the part of the stent towards the carinal side protrudes into the main vessel, wherein if the interventionalist attempts to prevent the protrusion of the stent into the main vessel, then the stent may miss the edge of the ostium opposite to the carina.

[0005] JP2014138851A details a bifurcation stent and method of positioning in the body lumen. In this system, two stents are used normally, wherein one stent is to be deployed in the main vessel and another one to be deployed in the branch vessel. In order to cover the branch vessel ostium completely with the branch vessel stent, it is necessary to deploy the main vessel stent because the distal part of the main vessel stent is wider wherein it encroaches into the branch vessel ostium and covers the overhanging edge of the branch vessel ostium, which otherwise is not possible only with the branch vessel stent.

[0006] Canadian patent CA2840880C teaches a bifurcated catheter, which can deploy a bifurcated stent constructed as a single piece into a bifurcated vessel. The system has two main parts, a Y-shaped catheter with a splittable seam and a custom-made stent that can be deployed with the help of a bifurcated catheter. Said system is meant to deploy two to three stents at bifurcation points i.e. , main vessel and two branches below the bifurcation point, and may not be suitable just to deploy a single stent at the branch vessel ostium.

[0007] EP2036519A1 details a bifurcation stent and stent delivery assembly, for treating a lesion at the vessel bifurcation in the body. Said system is meant to deploy three stents at bifurcation points, i.e. , one in the main vessel and two stents in two branch vessels and may not be suitable to deploy the only stent at the ostium of the branch vessel, because the configuration of branch vessel stent is like the usual cylindrical stent which otherwise can also be placed without the use of this special system. The disadvantage of the use of the usual cylindrical stent at branch vessel ostium is already mentioned above, in relation to prior art US20040267352A1 .

[0008] W02007001519A1 teaches a bifurcation stent assembly featuring a stent and branch vessel flap. Said system is meant to deploy two stents at bifurcation points, i.e., one in the main vessel and another in the branch vessel and may not be suitable to deploy the only stent at the ostium of the branch vessel. The branch vessel stent in this system is the usual cylindrical stent and the branch vessel flap of the main vessel stent aids to cover the ostium of the branch vessel completely. [0009] From the foregoing, it becomes apparent that there is a need for a stent for precise ostial stent deployment at the ostium of the branch vessel that is arising at various angles other than 90-degrees, wherein said stents have proximal edges shelved at specific angles to cover both the edges i.e. , carinal edge and the opposite overhanging edge of the ostium of the branch vessel without protrusion in the main vessel.

[0010] The present invention discloses a branch vessel ostial stent with an ostial stent delivery system that aids the precise deployment of the stent at the ostium of the branch vessel with no or minimal unwanted protrusion of stent or part of the stent thereof in the main vessel. It also provides complete coverage of the ostium of the stented branch vessel during the procedure.

SUMMARY OF THE INVENTION

[0011] The present invention details a branch vessel ostial stent and ostial stent delivery system which helps in the precise deployment of the stent at the ostium of the branch vessel. The characterizing features of said stent facilitate precise branch vessel ostial stent deployment to provide complete ostial coverage of branch vessel ostium along with no or minimal unwanted protrusion of stent or part of the stent in the main vessel.

[0012] Said stent features a side tube, which is a small tube of length around 15 to 20 mm and an inner lumen diameter of 0.5 mm wherein it is composed of material similar to the inner tube of the usual stent delivery system. The side tube has proximal and distal radiopaque markers for locating it under fluoroscopy. The proximal part of the side tube is attached to the proximal part of the semi-compliant balloon at its bare area i.e. , where the stent is not mounted with the help of a side tube connector. Due to this arrangement, when the stent along with the balloon is negotiated over the guidewire in the branch vessel to be stented and the side tube is negotiated over the adjacent branch guidewire, then the receding edge of the stent will always stay towards the receding edge (carinal edge) of the ostium of the vessel to be stented and the overhanging edge of the stent will stay towards the overhanging edge of the ostium (i.e. the edge of the ostium opposite to the carina) of the vessel to be stented resulting in optimal ostial coverage without protruding stent edges into the main vessel.

[0013] It is therefore the primary objective of the present invention to provide a branch vessel ostial stent and ostial stent delivery system that facilitates precise branch vessel ostial stent deployment to provide complete ostial coverage of branch vessel ostium along with no or minimal unwanted protrusion of stent or part of the stent in the main vessel.

[0014] It is yet another object of the present invention to propose a branch vessel ostial stent and ostial stent delivery system that eliminates the drawbacks of conventional stents in positioning them in and around vessel bifurcations or branch points.

[0015] It is a further object to provide a branch vessel ostial stent and ostial stent delivery system that resolves the need for the deployment of a stent in both the vessels i.e., the main vessel and a branch vessel at the bifurcation while addressing the treatment of the branch vessel with the stent.

[0016] Accordingly, the present invention proposes a branch vessel ostial stent and ostial stent delivery system configured to aid the precise deployment of a stent at the ostium of a branch vessel, comprising of: • metallic flexible hypotube 3 featuring an inner tube 5, wherein the interior of said tube is accessible through a lateral bore 9 at its proximal end and central lumen 5d of end tube 8 at its distal end;

• crimped ostial stent 6a mounted over an inflatable semi- compliant balloon 7a, wherein the proximal end of said stent is slanted in shape with an elliptical cross-section, wherein the plane of elliptical surface 21 forms an angle ‘a’ with the vertical side 23 of the said stent; and

• a side tube connector 12 configured to attach the proximal part of side tube 11 to the bare area 40 of the balloon 7a.

BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG.1 shows the branch vessel ostial stent with an ostial stent delivery system.

[0018] FIG.2 illustrates the guidewire crossing through the inner tube and guidewire crossing through the side tube.

[0019] FIG.3 depicts the geometry of the branch vessel ostial stent.

[0020] FIG.4 shows the three different branch vessel ostial stents with different stent deployment angles a or [3 i.e. , 30-degree, 45-degree, and 60- degree.

[0021] FIG.5 illustrates the semi-compliant balloon, stent, side tube, and side tube connector assembly.

[0022] FIG.6 illustrates the method to measure the angle of the branch vessel to be stented with respect to the main vessel.

[0023] FIG.7 depicts the steps involved in the deployment of branch vessel ostial stent using the ostial stent delivery system.

[0024] FIG.7A shows the coronary artery dividing into two branches.

[0025] FIG.7B illustrates how the coronary guidewire 14 is negotiated in branch vessel 28 to be stented and guidewire 15 is negotiated in adjacent vessel 27.

[0026] FIG.7C depicts the advancement of deflated balloon catheter 38a over the guidewire 14 and brought in the stenosed segment 30a of the vessel 28. [0027] FIG.7D shows the inflation of balloon catheter 38b in the stenosed segment 30a.

[0028] FIG.7E shows partially dilated stenotic segment 30b.

[0029] FIG.7F depicts the negotiation of stent-balloon assembly 39 along with an ostial stent delivery system over the respected guidewires i.e. , stent-balloon assembly 39 over the guidewire 14 and the side tube over the guidewire 15.

[0030] FIG.7G shows the deployment of the stent 6b against the inner lumen of the blood vessel by inflation of the balloon 7b.

[0031] FIG 7H illustrates the deployed stent in the vessel with guidewires in situ.

[0032] FIG.7I shows the deployed stent in the vessel.

DESCRIPTION OF EMBODIMENTS

[0033] The preferred embodiments of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However, in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.

[0034] The preferred embodiment of the present invention teaches a branch vessel ostial stent and ostial stent delivery system which aids in the precise deployment of the stent at the ostium of the branch vessel. The characterizing features of said stent facilitate precise branch vessel ostial stent deployment to provide complete coverage of the ostium of the branch vessel along with no or minimal unwanted protrusion of stent or part of the stent in the main vessel. [0035] FIG.1 illustrates the branch vessel ostial stent with ostial stent delivery system of the preferred embodiment. It comprises hub 1 with inflation port 2, metallic flexible hypotube 3, distal outer tube 4, inner tube 5, metallic crimped stent 6a mounted over inflatable semi-compliant balloon 7a, and end tube 8. Inflation port 2, hypotube 3, distal outer lumen 4, and cavity of the balloon 7a are in fluid communication with each other. Inner tube 5 works as a passage, wherein said tube is adapted to be advanced over a coronary guidewire. The proximal end of the inner tube 5 may be accessed via lateral bore 9 and at its distal end via central lumen 5d of end tube 8. As shown in the figure, the part of inner tube 5c underneath balloon 7 features two radiopaque markers i.e., proximal stent marker 10a representing the proximal stent edge and distal stent marker 10b representing the distal stent edge, to indicate the position of the stent under fluoroscopy.

[0036] As depicted in FIG.1, a side tube 11 of length around 15 to 20 mm and made of a material similar to that of the inner tube 5 is attached to the proximal part of the balloon 7 through a side tube connector 12. Referring to FIG.1 and FIG.5, said connector attaches the proximal part of side tube 11 to the bare area 40 of the balloon 7a where the stent is not mounted (as shown in FIG.5). The inner lumen diameter of the side tube 11 is 0.5 mm, wherein said tube is meant to be advanced over the adjacent branch guidewire 15, as illustrated in FIG.7. As shown in FIG.1 , side tube 11 has two radiopaque markers - proximal 13a and distal 13b - to mark the position of the side tube under fluoroscopy.

[0037] The side tube connector 12 is a silicon rubber structure that is stretchable, wherein said stretchable property of side tube connector 12 aids in easy positioning of the balloon 7 along with stent 6 with respect to the side tube 11 when the balloon 7 along with the stent 6 is navigated into the branch vessel to be stented along its respective guide wire 15, leaving the side tube in the main or adjacent vessel, as depicted in FIG.7.

[0038] The guidewire 14 crossing through inner tube 5 and the guidewire 15 crossing through side tube 11 is shown in FIG.2. The balloon is inflated 7b with the contrast media 16 using the inflation device in order to deploy the stent at the desired position inside the branch vessel. On inflating balloon 7b, the crimped stent mounted over said balloon 7b also expands 6b, wherein it gets deployed against the inner wall of the branch vessel.

[0039] FIG.3 illustrates the geometry of the branch vessel ostial stent. Normally, a cylinder has one curved surface 17, two flat surfaces 18 and 19, and height ‘hT. The ordinary stent is a hollow cylindrical metal mesh structure. In the preferred embodiment, however, at one end (proximal end), the branch vessel ostial stent is slanted in shape with an elliptical crosssection, as shown in FIG.3(H). As depicted in FIG.3(I) and FIG.3(J), said elliptical cross-section 21 is illustrated with three axes X, Y, and Z, wherein the central axis ‘C’ of the stent or alternatively, the vertical side 23, and the ‘X’ plane of elliptical surface 21 forms an angle ‘a’. During the procedure, based on the observed angle between the branch vessel to be stented and the main vessel (as shown in FIG.6), a stent with a suitable angle ‘a’ is chosen. Further, the central axis ‘C’ of the stent or the side 22 of the cylinder and the ‘X’ axis of elliptical surface 21 forms an angle ‘P’ congruent to angle ‘a’, as shown in FIG.3(I).

[0040] FIG.4 depicts three different branch vessel ostial stents with various stent deployment angles a or p i.e. , 30-degree, 45-degree, and 60-degree.

[0041] FIG.5 illustrates the semi-compliant balloon, stent, side tube, and side tube connector assembly. Further, FIG.5(N) shows the deflated balloon 7a with crimped stent 6a mounted over it. Referring to FIG.3 and FIG.4, the proximal edge of the branch vessel ostial stent is slanted at an angle, which gives rise to two different heights to the stent w.r.t the two points (24 and 25) on said elliptical edge, i.e., a longer height ‘h3’ and a shorter height ‘h2’. When said stent is crimped over the balloon, the proximal part of the balloon along the side of shorter height ‘h2’ remains bare 40 i.e., without getting mounted by the said stent. [0042] Owing to said construction, when the stent 6a along with the balloon 7a is negotiated over the guidewire 14 in the branch vessel to be stented, and the side tube 11 being negotiated over the adjacent branch guidewire 15, the receding edge 24 of the stent will always stay towards the receding edge 32 (carinal edge) of the ostium 31 of the branch vessel to be stented, wherein the overhanging edge 25 of the stent happens to stay towards the overhanging edge of the ostium (edge of the ostium opposite to the carina) 33 of the branch vessel to be stented, resulting in optimal ostial coverage without stent edges protruding into the main vessel (as shown in FIG.7).

[0043] FIG.5(0) illustrates the inflated balloon 7b with the contrast media 16 using the inflation device in order to deploy the stent at the desired position inside the blood vessel. On inflation, balloon 7b, the crimped stent 6a mounted over balloon 7b also expands 6b and gets deployed on the inner wall of the vessel. The part of inner tube 5c underneath balloon 7 features two radiopaque markers (proximal 10a and distal 10b) to indicate the position of the stent under fluoroscopy. The proximal radiopaque markers 10a lies at the level of edge 24 of the stent along the side 22 and shorter height ‘h2’ (as shown in figure 4), whereas the distal radiopaque markers 10b lies at the level of distal stent edge 19.

[0044] FIG 6 illustrates the method to measure the angle of the branch vessel to be stented with respect to the main vessel using two examples with different anatomy of bifurcation. Said examples are depicted in FIG.6 (P) and FIG.6 (Q). FIG.6 shows the coronary artery 26 dividing in two branches (27 and 28), featuring ostium 31 of branch 28 and atherosclerotic plaques 29 causing stenosis 30 in the vessel. Said figure also shows the carina 32, which is the ridge at the base of main vessel 26 that separates the opening of two branch vessels 27 and 28, as well as the overhanging edge 33 of the ostium of the branch 28. Referring to FIG.6, wherein an angle Y is formed at the intersection 36 of the imaginary line 34 passing through the carina 32 and the overhanging edge 33, and another line 35 that is drawn crossing longitudinally through the ostio-proximal segment 37 of the branch vessel 28 to be stented. That is, said lines (34 and 35) intersect at an angle y, wherein said angle is considered as the angle at which said branch vessel to be stented is arising from the main vessel. Further, said angle y helps to choose the correct branch vessel ostial stent to be deployed at the ostium 31 of the branch vessel 28 to be stented. The right branch vessel ostial stent is chosen according to the angle y’, wherein the angle ‘a’ of the stent (as shown in FIG.4) is equal to the angle y’ at the vessel bifurcation.

[0045] FIG.7 illustrates the steps involved in the deployment of branch vessel ostial stent using the ostial stent delivery system. The procedure employed is the usual steps involved in angioplasty. FIG.7(A) depicts the coronary artery 26 dividing in two branches 27 and 28, featuring ostium 31 of the branch 28 and atherosclerotic plaques 29 causing stenosis 30 in the vessel. Said figure also shows the carina 32, which is the ridge at the base of main vessel 26 that separates the opening of two branch vessels 27 and 28 whereas 33 represents the overhanging edge of the ostium of the branch 28. Referring to FIG.7(B), the coronary guidewire 14 is negotiated in vessel 28, and guidewire 15 is negotiated in adjacent vessel 27.

[0046] FIG.7(C) illustrates the advancement of deflated balloon catheter 38a over the guidewire 14, wherein it is brought into the stenosed segment 30a of the vessel 28. FIG.7(D) depicts the inflation of balloon catheter 38b in the stenosed segment 30a that causes the stenosed segment to dilate 30b partially as shown in FIG.7(E). At this stage, the best possible angiographic view is taken to assess the approximate angle y’ between the main vessel 26 and the branch vessel 28 to be stented at the point of bifurcation (as shown in FIG.6). The right branch vessel ostial stent is chosen according to the angle y’, wherein the angle ‘a’ of the stent (as shown in FIG.4) is equal to the angle y’ at the vessel bifurcation. The chosen stent along with the ostial stent delivery system is then advanced over the two guidewires, wherein the stent-balloon assembly 39 is advanced over the guidewire 14 that is parked in branch vessel 28 that is to be stented, and the side tube 11 is advanced over the guidewire 15 that is parked in the adjacent vessel 27. [0047] Then the whole system is gently pushed forward so that the side tube connector 12 sits on the carina 32 at the bifurcation of the vessels (27 and 28). The side tube connector 12 is a silicon rubber structure that is stretchable, wherein said stretchable property of side tube connector 12 aids in easy positioning of stent-balloon assembly 39 with respect to the side tube 11 when the stent-balloon assembly 39 is navigated into the branch vessel to be stented over the guidewire 15, leaving the side tube in the adjacent branch vessel, as depicted in FIG.7(F).

[0048] As illustrated in FIG.5, side tube 11 is attached to the bare area 40 of the balloon 7 (i.e. , towards the side 22 of the stent where said stent is not mounted). Owing to this arrangement, when the stent 6a along with the balloon 7a (stent and balloon are labeled together as stent-balloon assembly 39 in FIG.7) is negotiated over the guidewire 14 in the branch vessel to be stented, and the side tube 11 is negotiated over the adjacent branch guidewire 15, the receding edge 24 of the stent will remain towards the carina 32 at the bifurcation of the vessels, wherein the overhanging edge 25 of the stent will lie towards the overhanging edge 33 of the ostium 31 of the vessel 28, therein resulting in optimal ostial coverage without any protruding stent edges into the main vessel.

[0049] The position of the stent is then confirmed under the fluoroscopy with the aid of radiopaque markers 10a and 10b (as illustrated in FIG.1, FIG.2, and FIG.5). Once the position of stent 6a in the stent-balloon assembly 39 is confirmed, balloon 7a is inflated with the contrast media 16 using an inflation device (as shown in FIG.2 and FIG.5). As the balloon inflates 7b, the crimped stent 6a mounted over the balloon expands 6b and gets deployed against the inner lumen of vessel 27, as depicted in FIG.7(G). The balloon 7b is then deflated and the ostial stent delivery system is taken out. Further steps of angioplasty like post-dilatation of the stents are then continued as per the standard procedure. FIG.7(H) and FIG.7(I) show stent deployed at the ostium of the branch vessel 28.

[0050] Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention unless they depart therefrom.