1. Field of the Invention
The invention relates to catheters insertable within vasculature of a patient and more particularly to mechanisms and systems that alter the stiffness of at least one section of the catheter.
2. Description of the Related Art
Traditional vascular catheter designs struggle with the trade-off between flexibility and stiffness. Flexibility is desired to assist in navigating tortuous anatomy of the vasculature. On the other hand, stiffness is needed both for pushability during insertion and, after the distal tip of the catheter is positioned at a selected site, for stability to provide support during the advancement of accessory devices through the catheter.
There are a number of systems for steering catheters, such as disclosed by Lundquist et al. in U.S. Pat. No. 5,254,088 and by Heinzelman et al. in U.S. Pat. No. 5,364,351. Steering mechanisms described in these patents have levers or knobs which cause selective rotation or tension on steering wires or other elements within the catheters.
Several constructions of an adjustable stiffness catheter are described by Gregorich et al. in U.S. Patent Publication No. 2007/0060880. In one construction having coaxial hypotubes, the inner diameter of an outer hypotube is decreased, or the outer diameter of an inner hypotube is increased, to engage one hypotube with the other hypotube. In other constructions, one or more inflatable elements engage a hypotube.
It is therefore desirable to have an improved catheter stiffness adjustment mechanism that is simple to use and which does not bind inner and outer elements together.
An object of the present invention is to provide an improved stiffness adjustment system that can be actuated as desired during insertion and placement of a catheter to change its flexibility.
This invention features a catheter stiffener adjustment system including a first member with an outer diameter and having at least three first segments with at least one joint enabling the segments to bend relative to each other, and a second member having an inner diameter defining a passageway through which the first member is movable relative to the second member. The second member has at least three second segments with at least one joint enabling the segments to bend relative to each other. In a first position, the first segments and the second segments are alignable substantially in phase to generate a first flexure condition. In a second position, the first segments and the second segments are alignable substantially out of phase to generate a second, stiffer flexure condition.
In certain embodiments, the first member and the second member are at least one of rotatable and translatable relative to each other in both the first and second positions. In one embodiment, the joint for at least one of the first and second members is substantially helical. In some embodiments, the joint for at least one of the first and second members is formed by a thinning of material separating the segments. In other embodiments, the joint for at least one of the first and second members is formed by an elimination of material separating the segments along at least one side of the member.
In some embodiments, at least one of the first and second members is substantially tubular. In one embodiment, each of the first and second members is substantially cylindrical. In certain embodiments, the inner diameter of the second member is greater than the outer diameter of the first member in both the first and second positions.
This invention also features a catheter having a stiffener adjustment system including an outer catheter body defining a central lumen, a first member with an outer diameter and having at least three first segments with at least one joint enabling the segments to bend relative to each other, and a second member movable through the central lumen of the catheter body and having an inner diameter defining a passageway through which the first member is movable relative to the second member. The second member has at least three second segments with at least one joint enabling the segments to bend relative to each other. In a first position, the first segments and the second segments are alignable substantially in phase to generate a first flexure condition for the catheter. In a second position, the first segments and the second segments are alignable substantially out of phase to generate a second, stiffer flexure condition for the catheter.
This invention may also be expressed as a method of adjusting the stiffness of a catheter, including selecting a catheter having an outer catheter body defining a central lumen, a first member with an outer diameter and having at least three first segments with at least one joint enabling the segments to bend relative to each other, and a second member movable through the central lumen of the catheter body and having an inner diameter defining a passageway through which the first member is movable relative to the second member. The second member has at least three second segments with at least one joint enabling the segments to bend relative to each other. At least the three first segments and the three second segments have sufficiently similar lengths to enable alignment substantially in phase with the first and second members in a first position and, in a second position, being alignable substantially out of phase. The method further includes aligning the first segments and the second segments substantially in phase to generate a first flexure condition for the catheter. The method also includes aligning the first segments and the second segments substantially out of phase to generate a second, stiffer flexure condition for the catheter.
In what follows, preferred embodiments of the invention are explained in more detail with reference to the drawings, in which:
This invention may be accomplished by a vascular catheter having adjustable stiffness during insertion into vasculature of a patient, where the terms “vascular” and “vasculature” are utilized in their broadest meaning to include any duct or tube network in a human or other animal. A catheter according to the present invention includes a catheter stiffener adjustment system having a first member with an outer diameter and having at least three first segments with at least one joint enabling the segments to bend relative to each other, and a second member having an inner diameter defining a passageway through which the first member is movable relative to the second member. The second member has at least three second segments with at least one joint enabling the segments to bend relative to each other. In a first position, the first segments and the second segments are alignable substantially in phase to generate a first flexure condition, also referred to as a “flexibility mode”. In a second position, the first segments and the second segments are alignable substantially out of phase to generate a second, stiffer flexure condition, also referred to as a “stiffness mode”.
The present invention solves the trade-off faced by most conventional catheters by providing a system that generates an amount of stiffness that can be changed as desired, prior to or during a surgical procedure, by utilizing a simple actuation mechanism such as described below in relation to
A catheter 10, shown in cross-section in
In other words, this invention may be accomplished by a two-member system, each member having one or more joints of substantially the same frequency or periodicity as the other member to thereby establish segments having similar lengths, preferably substantially identical lengths, and enable the segments of the first and second members to be controllably aligned in phase or out of phase, depending on the desired amount of flexibility or stiffness for the members and accompanying structure such as an outer catheter body. In some constructions, the joints are formed by cuts, either continuous or discrete, which extend through the entire wall thickness of the member and, in other constructions, permeate to a selected wall thickness to create living hinges. One suitable source for metal hypotubes, formed of a platinum alloy or tantalum if radiopacity is desired, is Johnson Matthey Medical Components (see “www.jmmedical.com”). If metal or polymeric hypotubes or other hollow, substantially cylindrical tubes are utilized, it is generally easier to manufacture the joints as cuts made by laser or water jet into the outer diameters of the tubes. The segments then have a major or outer diameter, with a maximum wall thickness, while the joints have a minor or smaller diameter with minimal or no wall thickness, depending on the depth of the cuts. Partial cuts with minimal wall thickness can also be referred to as channels or grooves between segments.
Additionally, the joints, as continuous or discrete bending loci, can be formed on all of the length of the tubes or other elongated items serving as first and second members, or can be formed only on certain sections of the first and second members. Further, each member may also vary in thickness, material and/or durometer to generate a desired amount of flexibility or stiffness over selected lengths for the respective modes to tailor the stiffener adjustment system to particular procedures. Moreover, the periodic cut frequency, cut type and shape, and material of the two members can be adjusted to manage catheter kink radius, mean and differential stiffness between the two modes or states of flexibility, and length change needed to transition between the two modes or states.
Dashed line 130 represents another construction in which cover 120 has a dome-like distal end which occludes the distal opening of passageway 24a. Cover 120 is sealed entirely by seal 122 on outer segment 124, obviating the need for seal 126.
Biocompatible jacketing materials, inner liners, outer liners, and/or coatings can be applied to or over inner and/or outer surfaces of one or both of the first and second members as desired for particular procedures and to enhance compatibility with devices or fluids passed through catheters with adjustable stiffness according to the present invention. For example, imaging agents, pharmaceuticals, saline or other liquids may be injected under pressure. Liners or spacers can assist alignment of the joints of both members during use, and preferably reduce frictional engagement between the members within tortuous vascular pathways.
This invention may also be accomplished by a method of adjusting the stiffness of a catheter, including selecting a catheter having an outer catheter body defining a central lumen, a first member with an outer diameter and having at least three first segments with at least one joint enabling the segments to bend relative to each other, and a second member movable through the central lumen of the catheter body and having an inner diameter defining a passageway through which the first member is movable relative to the second member. The second member has at least three second segments with at least one joint enabling the segments to bend relative to each other. At least the three first segments and the three second segments have sufficiently similar lengths to enable alignment substantially in phase with the first and second members in a first position and, in a second position, being alignable substantially out of phase. The method further includes aligning the first segments and the second segments substantially in phase to generate a first flexure condition for the catheter. The method also includes aligning the first segments and the second segments substantially out of phase to generate a second, stiffer flexure condition for the catheter.
Thus, while there have been shown, described, and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions, substitutions, and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. For example, it is expressly intended that all combinations of those elements and/or steps that perform substantially the same function, in substantially the same way, to achieve the same results be within the scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated. It is also to be understood that the drawings are not necessarily drawn to scale, but that they are merely conceptual in nature. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
Every issued patent, pending patent application, publication, journal article, book or any other reference cited herein is each incorporated by reference in their entirety.