FIEED OF THE INVENTION: The present invention generally relates to a medical device. More particularly, the present invention relates to a design of a scaffold or stenting device for interventional vascular surgery within anatomical blood bifurcation.

BACKGROUND:

Stenting is a process of inserting a stent (can be a metal or polymer tube) into a lumen of an anatomical vessel to keep the passageway open. One of the major applications of the stenting device is in the field of vascular surgery. A number of surgical techniques have been developed to introduce various types of stents into different vascular structures. A lesion located at or near a bifurcation vessel is a challenge, since the stent needs to hold three separate vascular structures to be open.

Conventionally, there are various surgical techniques including "crush" stenting techniques and "T" stenting techniques. Particularly, in mini-culotte technique, a first stent is introduced into the smaller side branch at the bifurcation and the second stent is then introduced into the larger main branch of the bifurcation overlapping the first stent.

In United States Patent No. 6264682 to W. Stan Wilson et al. entitled “Stent and catheter assembly and method for treating bifurcations” discloses an apparatus and a method for stenting bifurcation vessels. The apparatus comprises a proximal angled stent for implanting in a side- branch vessel and a second aperture stent for implanting in the main vessel adjacent to the bifurcation vessel. Side branch and main vessel catheter assemblies are advanced over a pair of guide wire for delivering, positioning and implanting the stents. In European Patent No. 1512381 to Robert Burgermeister et al. entitled “Side branch stent with split proximal end” describes a stent for implantation into a vessel comprises a first stent having a longitudinal axis, proximal end and a distal end. The distal section of the stent has a plurality of circumferential set of struts; each strut longitudinally separated from each other and forms a cylindrical portion. The proximal portion of the strut has three spokes, each connected to the proximal most circumferential set of strut members. A second stent has a cylindrical distal section and a split proximal section designed to be flared outward with respect to the cylindrical distal section.

In PCT Application No. 2016131822 to Sheiban entitled “STENTING DEVICE COMPRISING A BALLOON WITH AN ECCENTRIC SHAPE” discloses a stenting device comprising an expandable stent, having a proximal region, distal region and a balloon catheter comprising a proximal section with first diameter and distal section with second diameter, when expanded form an eccentric shape. The stent has struts in proximal region greater than the struts in the distal region. The proximal region and distal region are linked by means of two linkers.

Though, number of devices are available for bifurcation stenting in the prior art, there exists many shortcomings on such devices. The expansion of the second stent will not be effective since the struts of the first stent will hinder the introduction of the second stent. The deployment and the positioning of the stent are difficult since the main vessel section is bulkier. Also, the main vessel section causes blockage to the side vessel since the main vessel section is made of smaller struts. The overlapping of the stents in the blood vessel will increase the risk of in-stent restenosis or stent thrombosis. Further, the opening of the strut links is ineffective due to the presence of two linkers.

Furthermore, an another major challenge in the existing catheter design is that the main vessel section had to be fully expanded together with the side branch vessel section, thus the positional adjustment of the stent is not possible. Also, if the main vessel is not deployed properly, it is difficult to visualise, further it requires another post dilation balloon to be employed for proper deployment. Thus, there exists a need for a bifurcation stent with simple design for providing easy deployment and proper positioning of the stent with minimal risk of restenosis. OBJECTS OF THE INVENTION:

The primary objective of the present invention is to provide a simple stent design for vascular surgery in bifurcation vessel enabling easy deployment and proper positioning of the stent. Another objective of the present invention is to provide a bifurcation stent device which minimizes the risk of restenosis and also the blockage of side vessel.

SUMMARY: The present invention provides an improved bifurcation stenting device comprises an expandable stent having a proximal region and a distal region. In the present invention, the proximal region of the stent is a main vessel section and the distal region of the stent is a side vessel section. In accordance with the present invention, the main vessel section and the side vessel section are made of plurality of struts that are linked by bridges. The strut size of the main vessel section is larger than the strut size of the side vessel section. The number of bridges between the struts in the main vessel section is lesser than the number of bridges between the struts on the side vessel section. The proximal main vessel section and the distal side vessel section are linked by a single bridge having length smaller than the length of bridge between the struts of the main vessel section or the side vessel section. According to the present invention, the stent has a shorter main vessel section of length without limiting to approximately 5.0 mm and a longer side vessel section of different length combinations. The main vessel section, having larger struts and diameter, is formed as a hybrid design, by a combination of closed and open cell structure with reduced number of bridges between the struts, and the side vessel section is formed by a different hybrid design with a combination of closed cell and open cell structure with more number of bridges between the struts or by a completely closed cell structure. The diameter of the main vessel section of the stent is greater than the diameter of the side vessel section of the stent, for example with a difference of at least 0.5 mm.

In one embodiment of the present invention, the main vessel section and the side vessel section may be made of similar material. In another embodiment of the present invention, the main vessel section and side vessel section may be made of different materials or different combination of materials.

According to the present invention, the main vessel section and the side vessel are balloon expandable using a dual balloon catheter or multiple single balloon catheters.

In another embodiment of the present invention, the main vessel section is self-expandable and is mounted on a silicon coated section of the dual balloon. The side vessel section is balloon expandable using a dual balloon catheter and is mounted on the stent delivery system. In another embodiment of the present invention, the main vessel section is balloon expandable and the side vessel section is self-expandable.

In yet another embodiment of the present invention, the main vessel section and the side vessel section are self-expandable. In yet another embodiment of the present invention, both main vessel section and side vessel section are balloon expandable using a dual balloon catheter. In one embodiment of the present invention, the stent is crimped on the dual balloon for expanding the stent during deployment. Stent delivery system is provided with plurality of markers, including but not limited to balloon radio-opaque markers, for monitoring the position of the device within the patient during stenting process. In one embodiment of the present invention, all the markers on the stents are removed and the stent is deployed using the markers provided on the dual balloon catheter. This reduces the cost of fabrication of the stent and reduces the complexity associated with positioning of the stent.

These objectives and advantages of the present invention will become more evident from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF l lll DRAWINGS:

The objective of the present invention will now be described in more detail with reference to the accompanying drawing, wherein:

FIG. 1 shows the design of the bifurcation stent according to the present invention;

FIG. 2 shows the bifurcation stent as crimped on the stent delivery system;

FIG. 3 shows the bifurcation stent during deployment;

FIG. 4 shows the bifurcation stent after deployment in the bifurcation vessel; FIG. 5 shows the self-expanding and balloon expanding section; and

FIG. 6 shows the dual balloon catheter for stent delivery.

OFT ATT /FT) DESCRIPTION OF I IIF INVENTION:

The present invention discloses an improved stenting device for vascular surgery in bifurcation vessel comprises an expandable stent having a proximal region, a distal region and a dual balloon catheter for expanding the stent. The proximal region is a main vessel section and the distal region is a side vessel section.

According to the present invention, the stent design comprising the main vessel section and the side vessel section is made of plurality of struts linked by bridges. The strut size of the main vessel section is larger than the strut size of the side vessel section.

Further in the present invention, the number of bridges between the struts in the main vessel section is lesser than the number of bridges between the struts in the side vessel section. The main vessel section and the side vessel section are linked by a single bridge for providing efficient opening of the strut links during the deployment process in the bifurcation. The length of the bridge linking the main vessel section and the side vessel section is smaller than the length of bridge between the struts of the main vessel section or the side vessel section.

The main vessel section is made by a combination of closed and open cell structure forming a hybrid design with reduced number of bridges between the struts and the side vessel section is made by a combination of closed and open cell structure or by a completely closed cell structure forming a different hybrid design, with more number of bridges between the struts. The stent has smaller main vessel section and longer side vessel section. Typically, the main vessel section has a length, without limiting, in the range 2.0mm to 10.0mm and often in the range 4.0mm to 6.0mm, approximately 5.0mm. The side vessel section has a length of different combinations, without limiting, in the range 10.0mm to 30.0mm, often in the range 15.0mm to 20.0mm. The diameter of the main vessel section of the stent is greater than the diameter of the side vessel section of the stent. Typically, the diameter of the proximal region is in the range, 3.0mm to 5.0mm. For example, the main vessel section has a diameter greater by at least 0.5mm than the side vessel section The skilled person would appreciate that different ranges of diameters, for both the stent and the balloon, could be employed depending on the particular type of vessel or vessels in the body for which the stent is intended (such as coronary arteries, peripheral arteries and veins.

The main vessel section and the side vessel section is made of similar materials, including but not limited to, stainless steel, cobalt chromium, nitinol alloys, polymers or magnesium.

In one embodiment of the present invention, the main vessel section and side vessel section may be made of different materials or different combination of materials.

Referring to FIG. 1 , the design of a bifurcation stent comprises the smaller main vessel section with larger struts and less bridge whereas the longer side vessel section with shorter struts and same number of bridges as the struts. The main vessel section and the side vessel section are linked by a single bridge.

In accordance with the present invention, the stent is crimped on the dual balloon for expanding the stent during deployment. For example, the stent can be deployed on the dual balloon catheter device as illustrated in Indian Patent Application Number 201941016372. Initially, the main vessel section is partially expanded which provides a facility to adjust the stent position and ability to ensure that the stent is properly deployed on the vessel surface. Stent delivery system is provided with a plurality of markers, including but not limited to balloon radio-opaque markers, for monitoring the position of the device within the patient during stenting process. Referring to FIG. 2, it illustrates a bifurcation stent structure when crimped on a stent delivery system. The main vessel section to be allocated in the main vessel and the side vessel section to be allocated in the side vessel of the bifurcation vessel during the deployment of stent is shown in FIG. 3.

Referring to FIG. 4, it illustrates the position of the main vessel section and the side vessel section after deployment in the bifurcation vessel. According to the present invention, the main vessel section is made of expandable material and the side vessel section is expanded by using balloon catheter. The main vessel section is mounted on a silicon coated section of the dual balloon and the side vessel section is mounted on the stent delivery system. The silicon balloon material is embedded between the struts for holding the expanding stent placement. During the deployment process, when the balloon is expanded partially, the stent is released due to the expansion of the silicon balloon, as illustrated in FIG. 5 & FIG. 6.

In one embodiment of the present invention, the section is made of different material for different type of deployment. For example, for self-expanding type deployment, silicon balloon material is used and for balloon expanding type deployment pebal or nylon variant is used.

In one embodiment of the present invention, a stent having a self-expandable main vessel section and balloon expandable side vessel section made of different materials (for example, Nitinol and CoCr respectively) are linked by creating two nudge areas on the two section and are attached manually by applying force.

In one embodiment of the present invention, the sections are linked by ultrasound or laser welding process. In another embodiment of the present invention, the main vessel section is balloon expandable using a dual balloon catheter and the side vessel section is self-expandable. In yet another embodiment of the present invention, the stent is capable of self-expanding during the deployment. These self-expanding stents have shape memory. When the stent reaches particular temperature, for example body temperature, it will automatically expand without the need of balloon catheter for expansion.

Thus, the present invention describes an improved bifurcation stent design which provides easy deployment and proper positioning of the stent as the main vessel section is less bulky. Large struts in the main vessel ensure minimum risk of blocking the side vessel and reduce the risk of restenosis due to reduced contact of stent metal and the vessels. Also, the present invention provides a facility of adjusting the stent during the deployment process since it utilizes dual balloon for expansion. Further, the markers are removed from the stent of the present invention and the stent is delivered using the markers provided on the dual balloon catheter. Thus results in the reduction of fabrication cost of the stent and the difficulty existed during the positioning of the stent.

While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.