Retractable catheter

Abstract

A retractable catheter including an elongate tubular sheath having at least in a distal portion made of a relatively flexible material, a reinforcing structure made of a relatively inextensible material incorporated in the relatively flexible material of the sheath along at least a portion thereof, and a pull element for transmitting a pull force longitudinally to the sheath and the reinforcing structure, wherein the pull element is connected directly to a portion of the reinforcing structure exposed from the relatively flexible material to transmit the pull force directly to the reinforcing structure.

Description

PRIORITY[0001]This application claims the benefit of priority to U.S. Provisional Patent Application No. 61 / 119,661, filed Dec. 3, 2008, and to U.K. Provisional Patent Application No. 0822109.5, filed Dec. 3, 2008, each of which is incorporated by reference into this application as if fully set forth herein.FIELD OF THE INVENTION[0002]This invention relates to a retractable catheter preferably for use as an outer sheath in an implant catheter delivery system, and to a method of manufacturing a retractable catheter. Such a catheter is preferably sized to be inserted in a bodily lumen. Such a retractable catheter includes a pull element connected at its distal end to an elongate tubular sheath.BACKGROUND ART[0003]Conventional implant catheter delivery systems comprise an inner shaft that extends from a proximal end to a distal end of the system and carries on its distal end a self expanding implant. A longitudinal tubular sheath lies radially outside the implant to retain the implant ...

AI Technical Summary

Benefits of technology

[0009]An advantage achievable with embodiments of the present invention is to improve the connection between a pull element and an outer sheath in a catheter system, whilst preferably avoiding an increase in the diameter of the outer sheath. Another advantage obtainable with embodiments of the present invention is to provide an outer sheath having evenly formed outer and inner surfaces.

[0010]Due to the force being transmitted directly into the element of the catheter sheath which is strongest in tension, a greater force can be applied to the catheter without risk of damage to the catheter sheath or of breaking the connection between the pull element and the sheath. Application of tensile forces up to 110N has been achieved with this connection method, as compared with 31N for known swaging ring techniques. Furthermore, the need for swaged inner and outer rings can be obviated, which can reduce the overall retractable catheter diameter.

[0011]A further advantage which can be achieved is to provide a larger gap between the catheter sheath and an implant retained thereby, to stop the sheath pressing on the implant as it passes around a tight curvature, without any significant increase in the overall catheter diameter, due to the lower profile sheath that can be used with this construction. This can reduce the friction between the sheath and the implant during retraction, thus lowering the retraction force which must be applied. This enables deployment of longer or covered implants into relatively narrow body passages.

[0012]Preferably, the exposed portion of the reinforcing structure is exposed in an opening in the flexible material and / or by not being completely incorporated in the flexible material. An opening can be provided at the best place for making the exposure and connection, increasing the flexibility and adaptability of the connection process. Alternatively, by not incorporating the reinforcing structure completely the connection process can be easier to manage during manufacture.

[0013]In preferred embodiments, the reinforcing structure comprises a braiding. Braiding can provide well defined directional reinforcement of the sheath material, and can be securely encapsulated in the sheath material.

[0014]Preferably, the pull element is thermally connected to the reinforcing structure, the thermal connection method preferably including laser welding, resistance welding, gap welding, and / or point welding. Such a connection is easy to accomplish and further avoids unnecessary extra elements. Thus, the connection can be made thin, allowing more space within the sheath to slide past the implant, and friction during sheath retraction can be further reduced.

Problems solved by technology

Since a greater force has to be applied, the possibility arises that the inner shaft may deflect or move under compression, as tension is applied to the pull wire.

Larger forces will also tend to break the connection between the pull wire and sheath.

Another disadvantage of such an arrangement is that the diameter of the outer sheath has to be at least large enough, for the inner shaft, the stent and the inner ring to be accommodated in the sheath.

Furthermore, the outer rings increase the thickness of the device as well, at least if one is clamped directly on the inner ring, and may distort the outside surface of the outer sheath.

Since an application of such an implant catheter delivery system is for delivery of stents by advancing the catheter system into a bodily lumen, a thicker diameter reduces the range of possible treatment opportunities, especially in the narrow confines of a patient's vasculature, or may give rise to a risk of injury as the catheter system is advanced.

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