Catheter with gear body and progressively compliant tip

Abstract

The present invention relates to an improved intravascular catheter. One improvement relates to the catheter body wherein the body is made of an inner tube of high temperature thermoplastic having a low coefficient of friction (for example fluorinated polymer). The extruded inner tube carries on its periphery a plurality of gear bodies. Each gear body further includes opposing elongated tangentially extending gear teeth spaced above the periphery of the tube. Wires are wound about the tube and over the gear teeth. An overcoat of low temperature thermoplastic covers the entire catheter and is interstitially disposed beneath the tangential teeth and the gear supported portions of the wire. The overcoat of low temperature thermoplastic over the high temperature fluorinated polymer produces an interlocking gear thereby enhancing the lamination of both low and high temperature polymers. This coupled gear design makes possible a mechanical anchoring to fluorinated polymers such as TEFLON.RTM. which are difficult, if not impossible, to bond. Another improvement of the intravascular catheter involves the use of a progressively compliant tip at the distal end of the catheter body. This progressively compliant tip utilizes an endmost tubular member having a first softness and an intermediate tubular member having a second softness. The low temperature thermoplastic overcoat on the catheter body has a third softness which is significantly lower than the first and second degrees of softness exhibited by the other tubular members. The endmost member, intermediate member and thermoplastic overcoat are joined together by heat formed, blended tubular regions, each having respective incrementally increasing intermediate softness characteristics over predetermined lengths thereof. The incrementally increasing intermediate softness characteristic of these blended regions is formed by heated diffusion of the endmost member with the intermediate member, and further by the heated diffusion of the intermediate tubular member with the polymer overcoat. Accordingly, the softness and hence the compliancy of the distal end region of the catheter tip changes from the distal end of the tip (very soft) to the first blended tubular region (high-medium degree of softness), to the intermediate tubular member (medium degree of softness), to the further blended tubular region (medium-low degree of softness), and ultimately to the thermoplastic overcoat (low degree of softness).