Balloon catheter

Details Balloon catheter Balloon catheter

1999-05-28

2004-04-20

Bennett, Henry (Department: 3743)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S093010

Reexamination Certificate

active

06723070

ABSTRACT:

FIELD OF INVENTION
This invention is related to balloon catheters.
BACKGROUND OF THE INVENTION
Heretofore, balloon catheters have been used, for example, for the percutaneous transluminal coronary angioplasty or PTCA. One such balloon catheter comprises of a thin flexible shaft and a balloon disposed on the distal end of the shaft. When fluid is supplied to or removed from the proximal end of the shaft via a supply/removal path for liquid, the balloon on the distal end of the shaft inflates or contracts.
In general, the shaft of the balloon catheter has high flexibility. High flexibility ensures that the shaft can flexibly curve along a bending blood vessel to smoothly guiding the balloon catheter into the vessel. But having a shaft with high flexibility naturally lacks rigidity and therefore provides poor pushability in the operation of the balloon catheter.
To improve on the above mention problem a balloon catheter having a core made of metal wire or the like fixed inside the shaft was provided. Since such a balloon catheter had a higher rigidity due to its core, the pushability in the operation of the balloon catheter was improved compared to a balloon catheter without a core. However, to some extent the flexibility of the shaft was sacrificed due to the more rigid core.
In the case of a conventional balloon catheter, though either one of flexibility or pushability was alternatively improved depending on whether the shaft of balloon catheter had a core or not, another important property is sacrificed. Once either type of a balloon catheter is chosen adjusting for flexibility or pushability during the operation of the balloon catheter that corresponds to encountered circumstances is impossible.
SUMMARY OF THE INVENTION
Wherefore, an object of the present invention is to provide a balloon catheter whose flexibility or pushability can be controlled depending on encountered circumstances during its operation.
In order to achieve the above and other objects, the present invention provides a balloon catheter having a thin and flexible shaft in which a fluid supply/removal path extends from the proximal end to the distal end. To the distal end of the shaft a balloon is secured. The balloon is inflated when fluid is supplied into its inside via the fluid supply/removal path, and is contracted when the fluid in its inside is removed. Finally, a core is provided in such a way that the core is inserted into the shaft from the proximal end of the shaft into its inside, and is slidable along the shaft. It is to be appreciated that allowing the tip end of the core to protrude from the shaft is prevented.
For the balloon catheter of the present invention, its structure and material are the same as those for a conventional balloon catheter. Typically, the balloon is made of a moldable polymer like, for example, polyurethane, latex, silicone rubber, natural rubber, polyvinyl chloride, polyamide, polyamide elastomer, copolymer of ethylene and vinyl acetate, polyethylene, polyimide, polyethylene terephthalate, fluorine resin and the like. However, it is to be appreciated that any other resin which is flexibly extendable and shrinkable, and is harmless as a medical apparatus can also be used, as there is no special limitation on such useable materials. Additionally, the shaft may be made of any material similar to that of the balloon so long as the material used can be flexibly bent while maintaining the form of the lumen.
To increase rigidity, the shaft has an insertable core. This core is made of a material which increases rigidity of the shaft without sacrificing for the lowest flexibility demanded of the shaft. Specifically, a metal wire thinner than the shaft or the like is used. Preferably, the metal wire has sufficient rigidity, even though very thin, and such tenacity that it does not break when bent. More specifically, such a metal used includes stainless steel, tungsten, nickel- titanium alloy, amorphous alloy and the like.
The core of the present invention is arranged in such a way that its end cannot protrude to the outside of the shaft. Various arrangement structures can be applied. For example, while a receiving space for a core is kept in the shaft, the length of the core insertable into the shaft is made shorter than the length of the receiving space. Such a structure prevents the core from protruding outside of the shaft. Since the end part of the core cannot protrude to the outside of the receiving space, the distal end of the receiving space may be of any structure. Alternatively, by applying a structure in which the end part of the core abuts the distal end of a wall defining the receiving space, the end part of the core is prevented from being protruded to the outside of the shaft. In this alternative embodiment the distal end of the wall defining the receiving space should be formed in such a way to prevent problems from occurring should the core abut the distal end of the wall. Further, in this alternative embodiment the core is not restricted concerning its total length and can be made, for example, excessively long, since the core cannot be further pushed into the receiving space, once the end part of the core abuts the distal end of the wall.
Though either a gas or liquid can be used as the fluid for inflating the balloon, liquid is more preferable because of the lesser effect pressure has on changing the volume of an inflated balloon. Such a liquid includes a physiological salt solution, a solution containing contrast medium or the like. In the case of gas, an inactive gas like helium is preferable.
When using the present invention, for example, when the stenosed part of the blood vessel is to be expanded with a catheter, the balloon catheter is inserted into the blood vessel in the same manner as a conventional balloon catheter. The difference being the slidable core of the catheter, which when slid towards the distal end, provides a higher rigidity to its influenced part of the shaft, while the uninfluenced part remains more flexible. Conversely, when the core is slid towards the proximal end, the part of the shaft without the core's influence becomes more flexible, while the part of the shaft with the core remains less flexible. Therefore, the flexibility and the pushability of the balloon catheter of the invention can be adjusted depending on the circumstances encountered when in use.
Specifically, in the circumstance where there is a bend in a blood vessel with the present invention an adjustment can be performed where the core is slid to the distal end side to keep good pushability until the catheter reaches the bent part of the blood vessel. Once at the bend, the core is then slid to the proximal end side in order to improve the flexibility of the distal end part of the shaft so that the catheter may pass through the bent part of the blood vessel. In this manner, the balloon catheter of the present invention makes its possible to adjust for flexibility or pushability during its operation to correspond to encountered circumstances.
The body conformation, the state of bending of the blood vessel and the distance from the insert portion of the catheter to the lesion of the patient differ depending on the patient to whom a balloon catheter is applied. By sliding the core corresponding to these conditions, the length of the shaft with high flexibility can be freely adjusted.
Moreover, as for the balloon catheter of the present invention, the core is preferably exchangeably formed by pulling out the core from the shaft. According to the balloon catheter formed in such a way, the rigidity of the shaft can be finely adjusted if only a few kinds of core are prepared, since the core can be pulled out from the shaft and exchanged. Needless to say, when fine adjustment of the rigidity of the shaft is unnecessary, the catheter may be formed in such a way that the core cannot be pulled out from the shaft or cannot be exchanged even if it can be pulled out (for example, a structure in which it is difficult for the core to be reinserted once it has been pulled out). Ado

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