Claims:1. A balloon dilatation catheter comprising:
an elongate, flexible tubular shaft having proximal and distal ends, wherein the tubular shaft is modified to provide a set of entry and exit points;
an inflatable balloon on the distal end of the tubular shaft, wherein the tip of inflatable balloon is bonded with set of hollow tubes to provide another set of entry and exit points;
an inner lumen extending through the tubular body and interacting with the inflatable balloon;
wherein the balloon is inflatable to a pressure, to create a focalized concentrated force in order to break the stenosis.
2. A balloon dilatation catheter as claimed in claim 1, wherein the flexible tubular shaft is bonded with tapered track wire at proximal end and connected to inflation lumen at distal end.
3. A balloon dilatation catheter as claimed in claim 2, wherein the proximal end of the flexible tubular shaft is connected to inflation hub through the inflation lumen.
4. A balloon dilatation catheter as claimed in claim 1, wherein elongate tubular shaft is composed of stainless steel having an external diameter ranging between 0.5mm to 0.7mm and internal diameter ranging between 0.35mm to 0.45mm.
5. A balloon dilatation catheter as claimed in claim 1, wherein the inflatable balloon can be made of nylon having a diameter ranging between 1mm to 4mm.
6. A method of operating a balloon dilatation catheter, wherein the balloon catheter is advanced over the guide wire through the set of multiple entry and exit points, allowing the inflatable balloon to apply focussed force on the said guide wire upon inflation of the balloon, by introducing the inflation medium/air through the inflation lumen connected to the said elongated tubular shaft, thus allowing the inflatable balloon to inflate at a pressure and create a focalized concentrated force in relation to the guide wire in order to break the stenosis.
, Description:FIELD OF THE INVENTION:
The present invention relates generally to intravascular catheters and more particularly to balloon dilation catheters suitable for angioplasty catheters, with a balloon having variable radial force along the longitudinal axis for improved expansion and stenting.
BACKGROUND OF THE INVENTION:
Balloon catheters are used in angiography, angioplasty and angio-occlusion. They comprise a catheter that carries a distal balloon that is inflated once the target site in a vessel is reached by the distal end of the catheter. Often the vessels through which the catheter is passed are narrow and torturous. In order for the balloon catheter to access sites in such vessels the catheter must be flexible, torqueable and of very fine dieter.
Percutaneous transluminal coronary angioplasty (PTCA) is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient’s coronary artery. The balloon on the catheter is inflated within the stenosis region of the patient’s artery, exerting the radial force on the stenosis to open up the arterial passageway, thereby increasing the blood flow.
In order to treat stenosis in small arteries, or to treat stenosis having small diameter openings, there have been continuing efforts to reduce the profile of balloon dilatation catheters. One disadvantage of the existing balloon dilatation catheters is that the overall profile of these catheters is limited due to the provision of both a guide wire lumen and an inflation lumen for inflating the balloon lumen. The fixed wire catheters have been developed that provide for a lower profile. These catheters are generally fixed to a guide wire or guiding member for advancement to a site of stenosis advance and therefore a guide wire lumen for relative movement between the guide wire and the catheter are not required, allowing for a reduced profile relative to other catheters. The lower profile allows these catheters to cross tighter lesions and to generally be advanced deeper into the vasculature. The disadvantage of such catheters is that the physician is unable to maintain position at the stenosis site when withdrawing the catheter and replacing it with one having a different balloon diameter. Instead the path to the stenosis must be continually established.
Therefore, a need exist for the reduced profile dilation catheters that can be advanced over a guide wire positioned at a stenosis site. A further need exists for such catheters that are easily manufactured, durable and easy to use.
SUMMARY OF THE INVENTION:
The present invention meets the above needs and is directed to a balloon dilatation catheter having an elongated shaft and a balloon mounted on a distal portion of the shaft. The balloon has a working section and proximal and distal end portions wherein, the proximal and distal end portions are secured to the catheter shaft within the working section. The balloon catheter of the present invention allows for a variable radial force along the catheter’s longitudinal axis without changing the outer diameter of the working section of the balloon or the wall thickness throughout the balloon. The location of the secured ends of the balloon creates a variable radial force along the balloon working section. Certain areas exert more force, and therefore expand more, against the vessel wall. This phenomenon is called focal expansion.
The present invention is further directed to a balloon dilatation catheter which works on the principle of focal force dilatation, wherein the balloon dilatation catheter is advanced over a guide wire positioned at a stenosis site. As the balloon is inflated at certain pressure, the balloon tend to focally expand, concentrating the force on particular points within the balloon, which are in co-relation with the guide wire, thus creating focalized expansion of the balloon, which in turn breaks down the stenosis with said focalized force of the balloon dilatation catheter.
The present invention is directed to a balloon dilatation catheter having an elongated shaft and a balloon mounted on a distal portion of the shaft, wherein the distal tip of the balloon is shaped in a manner to facilitate the easy and non-torturous manoeuvring of the assembly, also the elongated shaft is secured to the distal end portion of balloon in a manner to create a set of entry and exit points for the movement of guide wire. The distal tip of balloon is further connected to the working section of balloon in a way to create another set of entry and exit points for the movement of the said guide wire.
Further features and advantages of the present invention will become apparent to one of skill in the art in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 is the perspective view of the present invention i.e. perspective view of the balloon catheter
Figure 1a is the elevated view of the distal tip of the balloon of the balloon catheter
Figure 2 is the side view of the balloon tip of the balloon catheter
Figure 3 is elevated side view of proximal end portion of balloon catheter
Figure 4 is side view of distal end portion of the balloon catheter
DETAILED DESCRIPTION OF THE INVENTION:
Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Referring to Figure 1, there is disclosed a balloon dilatation catheter in accordance with one of the present invention. Catheters embodying additional features known in the art, such as implantable stents, drug delivery, perfusion or dilatation features, or any combination of these features, can be used in combination with the focal balloon of the present invention as will be readily apparent to one of skill in the art in view of the disclosure herein.
Referring to Figure 1, the balloon catheter 10 comprises of a laminated tubular shaft 11 having a proximal end 11a and a distal end 11b wherein the distal end 11b of the said shaft 11 is affixed with tapered track wire 12. The length of the laminated tubular shaft depends upon the desired application. For example, lengths in this area of about 110cm are typical for use in percutaneous transluminal coronary angioplasty applications.
In general, shaft 11, in accordance with the present invention, is provided with a generally circular cross sectional configuration having an external diameter within the range of from about 0.5mm to 0.7mm. In accordance with one of the preferred embodiment, the tubular shaft 11 has an internal diameter of ranging about 0.35mm to 0.45mm throughout most of its length. Alternate cross sectional configurations can be used, as well as other non-circular configurations, depending upon the number of lumen extending through the catheter, the method of the manufacture and the intended use. Tubular shaft 11 must have sufficient structural integrity e.g. push-ability to permit the catheter to be advance distal arterial locations without buckling or undesirable bending of the tubular shaft 11.
The laminated tip 12a for tapered track wire 12 is fixed with radiopaque marker bands 13a, 13b for easy visualization of the balloon catheter 10 within the body, able to move the said balloon catheter 10 by locating the radiopaque marker bands 13a, 13b by the physicians while performing the procedure. The marker bands not necessarily can be made of platinum (90%) and iradium (10%) material. The said marker bands 13a, 13b are usually placed at a gap, depending upon the balloon width, towards the distal end of the laminated tip 12a, as shown in Figure 2.
As illustrated in Figure 1, the distal end 10b of the catheter 10 is provided with at least one inflation balloon 14 having a diameter that ranges between 1mm to 4mm. The proximal end 10a of the catheter 10 is provided with a hub 15 having a balloon inflation port 15a. The tubular shaft 11 constituting the tapered guide wire 12 runs through the length of the balloon 14 and merges with the balloon tip 14a. The tubular shaft 11 is bonded with balloon through thermal bonding technique, wherein the tubular shaft extends from the distal end of the balloon 14b towards the proximal portion of the catheter 10 and connects to an inflation/deflation port 15a. The tubular shaft 11, may be formed of any suitable material known in the art that is sufficiently rigid yet flexible enough to be advanced through coronary vessels while avoiding trauma to the vessels. Preferably, the shaft is made of a polymer, Such as polyimide, polyester, nylon, polyethylene, or polyketones. The shaft can also be made of composites. The shaft may optionally be coated with a low-friction material or materials to facilitate advancement through coronary vessels. To further enable the movement of the guide wire 17, the tubular shaft 11 can be necked and modified at certain length for about 4 to 6mm to create a set of entry 16a and exit point 16b to facilitate the entry of the guide wire 17.
Inflatable balloon member 14 likewise can be formed of suitable material know in the art, preferably polymeric materials including non-compliant materials, such as polyethylene and polyethylene terephthalate, and semi-compliant materials such as Nylon homopolymers and copolymers. The non-compliant or semi-compliant nature of these materials guards against overexpansion of the balloon, which can cause injury to the patient's vasculature. Distal end 14b of balloon member 14 are bonded to tubular shaft 11 by conventional methods, such as thermal bonding, fusing or heat sealing, or adhesive bonding. Thermal fusing methods are preferred because they can yield a lower profile attachment site than adhesive bonding methods, which typically increase the profile of the shaft due to the addition of an adhesive layer between the balloon member and the shaft. The proximal end 11a of the tubular shaft runs through the balloon, in a manner as shown in Figure 1a, wherein the two radiopaque marker bands 13a, 13b bonded with the tapered wire 12, sits at the 14a’ and 14b’ in the balloon 14, thus making the tracking of the movement of the catheter 10 easy for the surgeons.
The proximal end 11a of the tubular shaft 11 is laminated and bonded with a strain relief tube 18 as shown in Figure 3, wherein the same is connected to the inflation hub 15. The proximal end 11a of the strain relief coated tubular shaft 11 can be thermally bonded to the inflation hub 15, wherein the shaft 11 connects with the inner lumen 15’ of the inflation hub 15 which further is connected to inflation port 15a thus facilitating the inflation and deflation of the balloon 14 when the same is connected to a inflation/deflation source.
At the catheter distal end 10b, the balloon tip 14a is covered and bonded with a set of flexible hollow tubes, wherein the unit 20 so formed as shown in Figure 4, comprises of a set of entry 20a and exit 20b point to facilitate the movement of the guide wire 17. The flexible hollows tubes can be of material such as pebax primarily thus not limiting the use of other flexible materials. The guide wire 17 is allowed to run through the multiple entry 16a, 20a and exit 16b, 20b in order to get better pushability. The balloon 14 is further wrapped in multiple pleats in a manner to provide smaller crossing profile in stenotic area to the catheter 10 while using the same.
In operation, as illustrated in Figure 5, when guide wire 17 is passed through catheter assembly 10, from different entry and exit points, thus allowing the said guide wire 17 to run over the balloon 14 and as the shaft 11 stretches and deflects, it provides for a tight seal around the guide wire, while at the same time still allowing for movement of the guide wire 17 relative to the catheter 10. In normal use, once the catheter 10 has been positioned at the desired location, inflation of the balloon 14 dilates a patient's vessel. Inflation of the balloon member is performed by introducing inflation media or air under pressure into inner lumen 15’ through inflation/deflation port 15a. Initially, as the pressure is increased the balloon member 14 starts inflating, and as the pressure inside the balloon member increases, the balloon 14 deflects and compresses against guide wire 17 to form a tight seal around the guide wire 17 and create a focalized concentrated force over the certain portion of the guide wire 17, thus resulting in the breakage of the stenosis 19. The balloon 14 will initially engage and press against the guide wire 17 at pressures of at least about 1.0-1.2 atmospheres. The balloon 14 continues to press against the guide wire up to rated burst pressure of balloon. The greater the pressure within the balloon member, the higher the force against the guide wire, greater concentration of focalized force against the stenosis.
Once dilation of the vessel is completed, balloon member 14 is deflated, typically by applying a vacuum to inflation/deflation port 15a. When vacuum is applied, the fluid pressure inside the balloon member decreases. As pressure in the balloon reduces, the balloon 14 disengages from guide wire 17. Once the balloon 14 has disengaged from the guide wire 17, movement of the guide wire 17 relative to the shaft 11 can again occur. Once the balloon is deflated, the catheter can be advanced further into a patient's cardiovascular system for treatment of additional stenoses, or can be removed from the patient's system.
Although only certain embodiments have been illustrated and described, those having ordinary skill in the art will understand that the invention is not intended to be limited to the specifics of these embodiments, but rather is defined by the accompanying claims.