SHAPE CONTROL OF CATHETERS BY USE OF MOVABLE INNER TUBE

Abstract: A composite catheter is formed from the combination of a catheter body and an inner tubular member, the two components being slidable relative to one another. Both components are of resilient construction with shape memories for at least a portion of their lengths, and at least one shape memory includes a curved segment. The rigidities of the two components are selected to be either equal or different, and in some cases one of the components varies in rigidity in segments along its length. These parameters are selected such that when the inner tubular member is advanced or retracted within the catheter body, the shape of the composite of both components varies in a continuous gradation. Movement of the inner tubular member thus permits the user to adjust the length, shape and location of one or more curves in the catheter body and thereby adjust the catheter body to its optimal shape for any particular patient or procedure without removing the catheter from the patient's body.

Description: SHAPE CONTROL OF CATHETERS BY USE OF MOVABLE INNER TUBE CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of co-pending United States patent application serial no. 08/544,399, filed October 10, 1995, the entire contents of which are incorporated herein by reference. This invention resides in the construction of catheters for use in interventional procedures in fields such as cardiology, neuroradiology, urology and gastroenterology. This invention is of particular interest in the construction of guide cateters. BACKGROUND OF THE INVENTION Guide catheters are relatively large lumen catheters used to guide catheters of smaller diameter, such as therapeutic, diagnostic or imaging catheters, into bodily passages that are curved or branched. A guide catheter specially designed for a procedure in a coronary artery, for example, is shaped so that its distal tip will reside inside one of the coronary ostia when the guide catheter is inserted into the femoral artery and through the aorta of the patient. Due to the arrangement of these ostia in the heart, a guide catheter for the right coronary artery is shaped differently than one for the left coronary artery. A guide catheter designed so that its tip resides in a carotid artery differs in shape from guide catheters for either the left coronary artery or the right coronary artery. Guide catheters of still other shapes are designed for other bodily passages and regions of interest. Guide catheters currently marketed are available in a variety of shapes to follow the contours of the bodily passages for which they are intended. Those of skill in the art recognize these different shapes by names such as Judkins Right, Judkins Left, Amplatz Right, Amplatz Left, Bentson, Shepherd Hook, Cobra, Headhunter, Sidewinder, Newton, Sones and others, each characterized by a distinct shape. Most of these shapes are available in gradations of size or curvature to accommodate differences among individual patients. One example of a type of guide catheter which is available in gradations of size, and which serves as an illustration of the needs addressed by the present invention are the catheters known as Judkins Left. The distal end of a Judkins Left catheter is formed into a hook, giving the catheter in its relaxed form a shape resembling the letter "J. " Near the tip of the hook is an additional bend. This bend is commonly referred to as the "first curve" or "primary curve" and is located approximately 1 cm or less from the distal tip, while the curve at the lowest point of the letter "J" is referred to as the "secondary curve. " The center of curvature of the secondary curve is generally about 3.5 cm to about 6 cm from the primary curve. When a Judkins Left catheter is inserted through the aorta into the heart, the "J" shape is distorted to follow the aortic arch, but the portion extending from the secondary curve through the primary curve to the distal tip maintains its curvature. The primary curve places the distal tip of the catheter in the left coronary ostium and a short distance inside the artery, while the secondary curve contacts the wall of the aorta on the side opposite the ostium. The contact continues for a short distance in the proximal direction, and terminates in a "tertiary curve" at the point where the guide catheter separates from the aortic wall. This length of contact between the guide catheter and the aortic wall anchors the Judkins Left catheter in position so that it will serve as a secure guide for the smaller operating (therapeutic or diagnostic) catheters to be inserted through it. Other guide catheters, including those for the coronary system as well as those for other bodily regions, have similar distal bends to direct the distal tips into specific branch passages, plus locations along the catheter length where the catheter contacts an internal wall for stabilization. The dimensions of these bodily passages differ from one patient to the next, and for proper stabilization and direction of the operating catheter, a guide catheter of the appropriate dimensions must be used. In Judkins Left catheters, for example, an important factor in stabilizing the catheter is the angle of the segment between the primary and secondary curves and the axis of the ostium when the guide catheter is in place, the axis of the ostium being generally transverse to the axis of the aorta. This angle is established by the distance between the primary and secondary curves, and for an aortic root of given dimensions, the angle will be greater when this distance is greater. For optimal anchoring stability, this angle is an acute angle of about 10°. Distal tips entering the ostium at greater angles are at serious risk of becoming dislodged when functional catheters are inserted through the guide catheter. The dimensions of the aortic arch and ascending aorta differ from one patient to the next, however, and one must select from among the range of available sizes of Judkins Left guide catheters the one size having the right dimensions for the patient undergoing treatment. In this type of procedure as well as others involving the use of guide catheters, therefore, operating rooms are equipped with a range of sizes so that exchanges can be made as needed. Since measurements of these bodily passages cannot be taken prior to insertion of the guide catheter, the physician often relies on visualization devices or techniques incorporated in the catheter body to determine whether the catheter is properly positioned. If the catheter cannot be properly positioned, it must be removed and replaced with one of a different size or a different shape, and this may have to be repeated until the appropriate fit is achieved. One disadvantage of these multiple insertions is cost, since catheters once inserted are not reused. The risk of infection also rises with multiple insertions since the major potential sources of infection are the patient's own skin contaminants and contamination from the operators, both of which are introduced at the insertion site. Still further, multiple insertions increase the risk of trauma to the vessels receiving the catheters. SUMMARY OF THE INVENTION The problems noted above as well as other problems associated with guide catheters of the prior art are addressed by the present invention, which resides in a catheter with a curvature which is changeable either in location, radius of curvature, length of curvature, direction of curvature, or two or more of these at the same time, and in which the change can be made from the proximal end of the catheter so that adjustments can be made either before the catheter is inserted into the body or while the catheter is inside the body. The invention is of particular interest in the construction of guide catheters, but is applicable to catheters in general. The catheter of the present invention is one of composite construction, including a catheter body and an inner tubular member which fits inside the catheter body, and is longitudinally movable (slidable) relative to the catheter body. The inner tubular member substantially fills the lumen of the catheter body, which is preferably a single-lumen catheter body, and the lumen of the inner tubular member is sufficiently large to permit operating catheters to be inserted through it. Both the catheter body and the inner tubular member are of resilient construction and both have shape memories for at least a portion of their lengths, and in many embodiments, for their entire lengths. The term "shape memory" is defined as the shape of the catheter body in its unmodified or relaxed condition. The f nctionality of the invention resides in one or more regions of curvature in the shape memories, in conjunction with the rigidities of the catheter body and inner tubular member relative to each other. Contained in the shape memories of the two components is at least one region of curvature. Thus, in some cases, only one of the two components has a shape memory that includes a curved region, while in others both components have curvatures in their shape memories, and in some cases, a single component has two or more regions of curvature. By appropriate selection of the relative rigidity of each component in conjunction with the number, placement and shape of the region(s) of curvature, the combined components are made to change shape by moving the inner tubular member lengthwise inside the catheter body. For this reason, the inner tubular member is at times referred to herein as an "actuating tube. " The actuating tube can thus be more rigid than the catheter body for a portion of its length or for its entire length, in which case the curvature (or lack of curvature) of this portion of the actuating tube will also be the shape of the combined components in the region where this portion resides. Alternatively, the actuating tube and the catheter body can be of substantially equal rigidity but differing in shape memory curvature, in which case the curvature of the combined components will be the sum of the curvatures of each component alone. The actuating tube can have a curvature of its own, or can be curved in one or more portions and straight in others. The rigid portion can constitute the entire actuating tube or only part of it, and in certain embodiments of the invention, as will be seen below, the actuating tube contains a flexible portion as well, and preferably two rigid portions separated by a flexible portion. The terms "rigid" and "flexible" are used herein as relative terms - in the case of the actuating tube, "rigid" or "relatively rigid" means more rigid and less flexible than the catheter body, while "flexible, " "more flexible, " or "less rigid" means less rigid and more flexible than the catheter body. When a curvature is included in the shape memory of either the catheter body or the actuating tube, the curvature can be any type of non-linear shape. The choice will depend on the use or type of catheter, or in the case of guide catheters, on the particular guide catheter presently known for which the composite catheter of the present invention will be used as a substitute. The curvature may thus be a wave-form curvature, a loop, an arc or part of a wave or loop, a loop with multiple turns, a spiral, or composite curves. A curvature in the form of an arc can vary in terms of the radius of curvature, whether the radius is constant or varies along the arc, and in terms of the total angular rotation of the arc. A curvature in the form of a loop can vary in terms of the number of turns, the radius of curvature of the loop, whether the radius is constant or varies along the length of the loop, and the location of the loop along the length of the catheter body. Certain composite catheters in accordance with this invention are effective substitutes for Judkins Left guide catheters, Shepherd Hook guide catheters, or Sidewinder guide catheters. In these composite catheters, the shape memory in the catheter body contains a loop which corresponds to the secondary curve in a conventional Judkins Left, Shepherd Hook or Sidewinder catheter, and the uncurved length of this loop exceeds the length of the secondary curve. The actuating tube is segmented along its length, with at least one segment that is substantially straight and more rigid than the catheter body and therefore capable of modifying the curvature imposed by the catheter body shape memory. The actuating tube also contains at least one segment that is either less rigid than the catheter body or has the same or greater rigidity and the same curvature as the curved segment of the catheter body and therefore does not modify the curvature imposed by the shape memory. This latter segment is however of shorter length than the curved segment of the catheter body. The actuating tube thus shortens the curved portion of the catheter body to conform to the secondary curve of the Judkins Left, Shepherd Hook, or Sidewinder shape, and the location of this secondary curve along the catheter can be varied by moving the actuating tube back and forth inside the catheter body. Analogous effects are achieved with catheters having the shape known as Sones. Other catheters in accordance with this invention are effective substitutes for Judkins Right guide catheters or Newton guide catheters. In these composite catheters, the actuating tube contains a relatively rigid segment (i.e. , more rigid than the catheter body) that is curved rather than straight. Accordingly, this segment of the actuating tube will impose its curvature on the catheter body, thereby curving a straight portion of the catheter body, or changing the radius of curvature or the direction of curvature of a curved portion of the catheter body. In certain embodiments of the invention, the actuating tube also includes one or more flexible segments, permitting the shape memory curvature of the catheter body to be retained, in those portions where the flexible segments reside. Thus, the result can be a combination of the curvature of the shape memory and that of the actuating tube. Composite catheters in which the entire actuating tube is more rigid than the catheter body can produce a complete change in shape by full insertion of the actuating tube, and an intermediate change by partial insertion. Thus, an Amplatz shape can be converted to a Judkins Right shape, with hybrid shapes in between. The same is true for other combinations. Analogous results are achieved when both components are of substantially equal rigidity, with insertion of the actuating tube resulting in an additive (or averaged) shape. For catheter bodies in general with loop-shaped curvatures, the variability in shape, curvature or both upon insertion of the actuating tube will depend on such factors as: (a) the number of turns in the relaxed loop, (b) the radius of curvature of the relaxed loop and whether the radius is constant or variable along the loop, (c) whether the loop begins at the distal end of the catheter body or is separated from the distal end by a non-looped segment, (d) the number and arrangement of relatively flexible and rigid segments in the actuating tube, and (e) the lengths of these segments. Similar considerations apply to embodiments in which the curvature is an arc rather than a loop. Thus, by selecting appropriate values and ranges for each of these dimensional variables, the concepts of this invention may be implemented to produce catheters of a wide variety of shapes, for use as adjustable replacements for many of the fixed-shape guide catheters presently in use. This includes catheters with hooks, loops, S-shaped curves, and other shapes. The relatively rigid portion(s) of the actuating tube will in general be less than completely rigid, and will instead have enough flexibility to permit passage of the composite catheter through the bodily passages as needed to reach the site of interest. The composite catheter will therefore still be curved or bent by the bodily passages themselves. The straightening of portions of the curvature dictated by the shape memory is likewise limited by the shape or curvature of the bodily passage. These embodiments are explained in detail below, together with explanations of other features and advantages of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 depicts a composite catheter of the present invention in transverse cross section. FIG. 2 depicts one example of a catheter body representing one component of a composite catheter in accordance with the present invention. FIG. 3 depicts an inner tubular member for use with the catheter body of FIG. 1, and thereby forming the second component of a composite catheter in accordance with the present invention. FIG. 4 depicts the two components of FIGS. 1 and 2 combined, with the catheter body in cross section to render the inner tubular member visible. FIG. 5 depicts the composite catheter of FIG. 4 inside an aorta, showing the catheter in several configurations differing by the degree of insertion of the inner tubular member. FIG. 6 depicts one example of the construction of the inner tubular member of FIG. 3. FIG. 7 depicts a second example of the construction of the inner tubular member of FIG. 3. FIG. 8 depicts a third example of the construction of the inner tubular member of FIG. 3. FIG. 9 depicts a fourth example of the construction of the inner tubular member of FIG. 3. FIG. 10 depicts a fifth example of the construction of the inner tubular member of FIG. 3. FIG. 11 depicts a catheter body for use as part of a different composite catheter in accordance with the present invention. FIG. 12 depicts an inner tubular member for use with the catheter body of FIG. 11. FIG. 13 depicts the catheter body of FIG. 11 and the inner tubular member of FIG. 12 combined, with the catheter body in cross section to render the inner tubular member visible. FIG. 14 is a second view of the same catheter body and inner tubular member, with the inner tubular member further advanced inside the catheter body. FIG. 15 depicts a third example of a catheter body for use as part of a composite catheter in accordance with the invention. FIG. 16 depicts an inner tubular member for use with the catheter body of FIG. 15. FIG. 17 depicts the catheter body of FIG. 15 and the inner tubular member of FIG. 16 combined, with the catheter body in cross section to render the inner tubular member visible. FIG. 18 is a second view of the combined components of FIG. 17, with the inner tubular member further advanced inside the catheter body. FIG. 19 depicts a fourth example of a catheter body for use as part of a composite catheter in accordance with the invention. FIG. 20 depicts an inner tubular member for use with the catheter body of FIG. 19. FIG. 21 is one view of the catheter body of FIG. 19 and the inner tubular member of FIG. 20 combined, with the catheter body in cross section. FIG. 22 is a second view of the combined components of FIGS. 19 and 20. FIG. 23 is a third view of the combined components of FIG. 19 and 20. FIG. 24 depicts a fifth example of a catheter body for use as part of a composite catheter in accordance with the invention. FIG. 25 depicts an inner tubular member for use with the catheter body of FIG. 24. FIG. 26 is one view of the catheter body of FIG. 24 and the inner tubular member of FIG. 25 combined, with the catheter body in cross section. FIG. 27 is a second view of the combined components of FIGS. 24 and 25. FIG. 28 depicts a sixth example of a catheter body for use as part of a composite catheter in accordance with the invention. FIG. 29 depicts an inner tubular member for use with the catheter body of FIG. 28. FIG. 30 is one view of the catheter body of FIG. 28 and the inner tubular member of FIG. 29 combined, with the catheter body in cross section, and the inner tubular member partially inserted in the catheter body. FIG. 31 is a second view of the combined components of FIGS. 28 and 29, with the inner tubular member fully inserted in the catheter body. DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS As indicated above, the concepts of the invention can be embodied in catheter constructions varying widely in shape, size and configuration, and thereby useful for a variety of bodily passages and types of clinical procedures. To promote a better understanding of the invention, this section of the specification describes several constructions in detail, each construction designed to substitute for a catheter in current use by duplicating or approximating its shape while permitting continuous variations in the shape to substitute for the limited discrete variations currently available. The Judkins Left shape is produced or approximated in FIGS. 2 through 5; the Shepherd Hook shape in FIGS. 11 through 14; the Judkins Right shape in FIGS. 15 through 18; the Sidewinder shape in FIGS. 19 through 23; the Newton shape in FIGS. 24 through 27; and an Amplatz Right- Judkins Right hybrid shape in FIGS. 28 through 31. It will be apparent to those of skill in the art, however, that the principles discussed in relation to these five classes of catheter shapes will be applicable to other classes as well. This variety of catheter shapes utilizes a variety of actuating tubes, differing in the locations and arrangements of segments of differing stiffness and the shapes of the stiffer segments. Examples of different manufacturing methods for achieving stiffness variations are given only for the actuating tube used in FIGS. 2 through 5, since the same principles can be applied to all actuating tubes. These manufacturing methods appear in FIGS. 6 through 10. FIG. 1 is a cross section of the catheter body 11, which appears as an outer tubular member, and the inner tubular member 12. This cross section is applicable to all shapes of catheters addressed by the present invention, and illustrates one method of making a section of an inner tubular member stiffer than the adjacent section of the catheter body. Both of these tubular members are made of the same material of construction. Greater stiffness in the inner tubular member 12 is achieved simply by using a thicker wall. Alternately, greater stiffness can be achieved by use of a different material of construction, such as different alloying components or proportions for metallic tubes, different additives or proportions for nonmetallic tubes, or by use of differences in molecular orientation or crystal structure, such as different degrees of crosslinking, biaxial orientation, or tempering. Still further means of achieving stiffness variations are by forming the tubular members of composite construction, such as combining resins with fibers or wire. As an example, the outer shaft can be of triple-layer construction, with inner, middle and outer layers. The inner layer is a lubricious plastic such as a fluorinated polymer or thermoplastic, or a thermoplastic elastomer with a lubricious coating, both for purposes of promoting smooth movement of the actuating tube. Typical materials for this inner layer are FEP (fluorinated ethylene-propylene) resin and PTFE (polytetrafluoroethylene). The middle layer is braided stainless steel or braided synthetic fiber, and serves to allow torque transmission from the handle of the catheter to its distal tip. The braided stainless steel can for example be wire of diameter in the range of 0.0005 inch (0.0013 cm) to 0.003 inch (0.0076 cm), or flat wire 0.00075 inch (0.002 cm) in thickness and 0.003 inch (0.0076 cm) in width. The outer layer is a thermoplastic elastomer, optionally filled with radiopaque material. Examples of thermoplastic elastomers are polyurethane, elastomeric nylon, and elastomeric copolymers. The actuating tube in this example is also of triple-layer construction. Its inner layer is polyimide or other high strength thermoplastic or thermoset material, with a coating of TEFLON (tetrafluoroethylene fluorocarbon polymer). A typical thickness of the inner layer is 0.0005 inch (0.0013 cm) to 0.003 inch (0.0076 cm), and the purposes served by the inner layer are to allow smooth movement of other interventional devices through its lumen, and to provide the column strength necessary to permit the actuating tube to be moved within the catheter body. The middle layer of the actuating tube is similar to that of the middle layer of the catheter body, although a preferred middle layer is made of a stainless steel coil, using 304V stainless steel (or similar alloys). The typical size range of the wire is 0.0005 inch (0.0013 cm) to 0.003 inch (0.0076 cm), and the typical space between adjacent coils is 0.001 inch (0.0025 cm) to 0.003 inch (0.0076 cm). The coil provides kink resistance to the actuating tube and the catheter body. The outer layer of the actuating tube is similar in purpose and construction to the outer layer of the catheter body. Both the catheter body and the actuating tube will often have stiffness transitions along their length, the transitions occurring at portions well removed proximally from the curvatures near the distal end that define the character of the catheter body as Judkins Left or Right, Amplatz Left or Right, and the others listed above. These stiffness transitions range from a relatively high stiffness near the proximal end (i. e. , the end closest to the physician) to a relatively low stiffness near the distal end (the end furthest inside the patient), and there are typically two to four of these transitions. The purpose of high stiffness at the proximal end is to provide column support during advancement of the catheter into the patient's body; and the purpose of the low stiffness at the distal end is to impart flexibility to the catheter for purposes of entering branched and curved passages in the body and anchoring the catheter at the desired position. These transitions can be achieved by the use of materials of different hardnesses and by changes in the braid or coil pattern. The stiffness at the proximal end can be as high as D72 to D95 (Durometer scale), while the stiffness at the distal end can be as low as A85 (Durometer scale). The stiffness variations addressed by this invention and discussed below as a means of changing the shape of the catheter in the region of its distal end are all within the region located distally relative to the last of these transitions. Nevertheless, differences in stiffness between the catheter body and the actuating tube are achieved in the same manner, as are any longitudinal variations in the region of distal curvature. The slight gap 13 between the catheter body and inner tubular member permits sliding movement, although in preferred embodiments as mentioned above, a lubricious coating on one or both of the contact surfaces serves to promote ease of sliding, and the actuating tube preferably fills the catheter body lumen, leaving little or not gap. The lumen 14 of the actuating tube can accommodate one or more additional catheters (not shown). Turning first to the Judkins Left shape in FIGS. 2 through 4, the catheter body (outer tubular member) 15 is shown in FIG. 2. No actuating tube (inner tubular member) has been inserted, and the catheter body 15 is therefore in a relaxed condition. As shown, the catheter body includes a distal tip 16 with a slight bend, a looped segment 17, and a relatively straight segment 18 between the distal end and the looped segment. The bent distal tip 16, which serves as the primary curve of the guide catheter, is preferably about 5 mm to about 10 mm in length, forming an angle of from about 120° to about 150° with the straight segment immediately adjacent to it. The length of the straight segment 18 extending from the primary curve at the distal tip 16 to the beginning of the looped segment 17 is preferably from about 1 cm to about 10 cm, and most preferably from about 2 cm to about 7 cm. For this catheter body, the looped segment 17 when relaxed as shown in FIG. 2 forms a loop with a total angular rotation of at least about 1.25ιτ radians. In preferred constructions, the total angular rotation of this loop is at least about 1.57r radians. In a presently preferred embodiment, the total angular rotation of the loop is about 1.83π radians (330°). The extended length of the looped segment will generally range from about 15 mm to about 100 mm, and preferably from about 25 mm to about 75 mm. In a presently preferred embodiment, this extended length is about 55 mm. The radius of curvature in the looped segment when relaxed will be from about 5 mm to about 20 mm, and preferably about 10 mm. FIG. 3 illustrates an inner tubular member 21 or actuating tube for the Judkins Left construction. This inner tubular member 21 contains two relatively rigid segments ~ a distal segment 22 and a proximal segment 23, both straight ~ and one relatively flexible segment 24 between the two relatively rigid segments. Of the interfaces 25, 26, between the relatively rigid and relatively flexible segments, at least one interface remains within the confines of the loop at any time, and the location of the interface dictates the shape of the composite catheter formed by the combination of catheter body and inner tubular member. FIG. 4 illustrates the assembled or composite catheter, with the inner tubular member inserted in the catheter body. The angular rotation of the loop is reduced to a 180° turn (π radians) by the distal 22 and proximal 23 (relatively rigid) segments of the inner tubular member, while the flexible segment 24 permits the curvature to remain over a shortened length although one which is sufficient to achieve the 180° turn. The amount of curvature which remains in the loop of the catheter body when the inner tubular member is inserted, and the distance between the remaining loop curvature and the distal tip of the catheter body, are determined by the length of the flexible intermediate segment 24 of the inner tubular member, and the position of this segment relative to the loop 17 (FIG. 2). The flexible segment 24 of the inner tubular member is shorter than the extended length of the loop, and the shorter the flexible segment, the lesser the degree and length of curvature at the secondary curve of the assembled guide catheter. In preferred embodiments of this invention, the flexible segment 24 of the inner tubular member will have a length ranging from about 0.1 to about 0.8 times the extended length of the looped segment of the catheter body. With a loop of the above dimensions, a preferred inner tubular member will be one with the flexible segment 24 having an uncurved length of about 5 mm to about 50 mm, and preferably about 15 mm to about 40 mm, but at least about 5 mm shorter, and preferably at least about 15 mm shorter, than the extended length of the looped segment. In a presently preferred embodiment, the flexible segment 24 is about 0.5 times the extended length of the looped segment of the tubular member, and is about 25 mm in length. An alternative to the inner tubular member of FIG. 3 is one in which all segments of the inner tubular member shown in the drawing are of greater rigidity than the segments of the catheter body shown in FIG. 2, and the curvature of segment 24 as shown in FIG. 4 is incorporated into the shape memory of the inner tubular member. The result when the two components are combined is the same as that shown in FIG. 4, despite the difference in the manner in which the inner tubular member functions. In either case, the further the flexible segment 24 (or its curved and more rigid counterpart in the alternative described in the last paragraph) is advanced distally along the length of the loop 17, the smaller the distance between the secondary curve and the distal end of the catheter body. Once the catheter is placed inside the aortic root, this distance controls the approach angle of the guide catheter toward the ostium in which the distal tip of the catheter is inserted. FIG. 5 shows the assembled catheter inside the aorta 31, and its distal tip 32 inside the ostium 33 of the right coronary artery. The catheter is shown in various gradations of shape 34, 35, 36, 37, with corresponding gradations in the location of the secondary curve 38 along the aortic wall and in the approach angle a of the catheter toward the ostium 33. These gradations are the result of different lengths for the distance between the secondary curve 38 and the catheter's distal tip 32, and are achieved by moving the inner tubular member relative to the catheter body. Examples of configurations and constructions for the inner tubular member of FIGS. 3 and 4 are shown in FIGS. 6, 7, 8, 9 and 10. In FIG. 6, the relatively stiff proximal 41 and distal 42 segments each consist of a continuous tube of metallic or high density polymeric material with inner and outer liners of thin, flexible polymeric material. The flexible intermediate segment 43 is of the same construction except that the continuous tube is replaced by a series of rings (whose outlines 44 are visible in the drawing), with gaps 45 between each pair of adjacent rings. The thin polymeric material in the gaps supplies the flexibility while maintaining the spacing between the rings (column strength). The thin polymeric material is still sufficiently stiff to avoid collapsing in the axial direction, even when the tubular member is pushed distally from the proximal end. The example of FIG. 7 contains relatively stiff proximal 46 and distal 47 segments likewise separated by an intermediate flexible segment 48. The entire tubular member is constructed of a unitary piece of tubing, and the intermediate segment 48 is rendered more flexible than the two outer segments by slots 49 cut into the tubing wall. In FIG. 8, the inner tubular member is formed of woven strands 50. The intermediate flexible segment 51 consists of the woven strands alone, while the relatively stiff proximal 52 and distal 53 segments each consist of the woven strands either impregnated or sheathed with a stiffening resin. Alternatively, the density of the weave, the thickness or gauge of the strands, or the strand material, can be varied to achieve regions of differing stiffness. In FIG. 9, which unlike FIGS. 6-8 and 10 is a cross section, the inner tubular member consists of a coil 61 either embedded in flexible resin or inside a flexible tube 62. The turns of the coil 61 vary from being closely spaced in the proximal 63 and distal 64 segments to being widely spaced in the intermediate flexible segment 65. The difference in spacing provides the difference in flexibility. The inner tubular member of FIG. 10 is a unitary piece of tubing 66 like that of FIG. 6, with a side section of its wall cut out, leaving two solid tubular segments 67, 68 as the stiff proximal and distal segments, respectively, and an intermediate strip of wall material 69 as the flexible segment. The strip is more flexible than the solid tubular sections due to its lesser amount of wall material. FIGS. 11 through 14 illustrate a composite catheter designed to serve as a Shepherd Hook-type catheter. The catheter body 71 without the inner tubular member is shown in FIG. 11. The catheter body has a curved segment 72 and a hook 73 at the distal end, the curved segment separated from the hook by a short straight length 74. The hook 73 corresponds to the primary curve of the Shepherd Hook catheter, and the curved segment 72 supplies the curvature for the secondary curve. The angular rotation of the curved segment 72 considerably exceeds the angular rotation of the secondary curve of the conventional Shepherd Hook catheter. FIG. 12 depicts the inner tubular member 76 for the catheter body of FIG. 11. Here, as in the inner tubular member of FIG. 2, there are two relatively rigid segments — one distal 77 and one proximal 78, both straight — separated by a flexible segment 79. The flexible segment 79 is relatively short compared to the flexible segment 24 of the inner tubular member of FIG. 2, and thereby permits less of the curve in the catheter body to remain. This is illustrated in the cross section drawings in FIGS. 13 and 14, which can be compared to FIG. 4. In FIGS. 13 and 14, the inner tubular member 76 is inserted in the catheter body 71 to two different depths. In each case, the only curvature remaining in the catheter body from the curved segment is the small length where the flexible segment 79 of the inner tubular member resides, the two straight and relatively rigid segments 77, 78 eliminating the curvature in the portions where they reside. Similarly to the alternative described above for FIG. 3, the inner tubular member of FIG. 12 can be substituted by an inner tubular member in which all segments shown in the drawing are of greater rigidity than the segments of the catheter body shown in FIG. 11, and the curvature of segment 79 as shown in FIGS. 13 and 14 is incorporated into the shape memory of the inner tubular member. The result when the two components are combined is the same as that shown in FIGS. 13 and 14. A composite catheter having a Judkins Right shape is formed by the catheter body and inner tubular member shown in FIGS. 15, 16, 17 and 18. The catheter body 81 is shown alone in FIG. 15. Its bent distal tip 82 is identical to the bent distal tip of a Judkins Right catheter. Immediately proximal to the bent distal tip is a first arc 83 that curves gently in the same direction as the bent tip. This arc has a radius of curvature that is approximately constant and equal to the radius of curvature at the corresponding location on a relaxed Judkins Right catheter. Adjacent to this arc 83 is a second arc 84 curving in the opposite direction. The radius of curvature of this second arc increases in the direction along the arc away from the distal end 82 of the catheter body. The remainder 85 of the catheter body is straight. Like the catheter bodies shown in the previous drawings, this catheter body, or at least the portion extending from the second arc 84 to the distal end 82, is formed of a single material of construction with a constant diameter and wall thickness. The inner tubular member 91 for this catheter body is shown in FIG. 16. The inner tubular member contains three segments - a proximal segment 92, an intermediate segment 93, and a distal segment 94. The intermediate segment 93 is flexible relative to the catheter body and assumes the curvature of the portion of the catheter body in which it resides. The proximal and distal segments 92, 94 are more rigid than the catheter body and impose their shape on the portions of the catheter body in which they reside. Of these two segments, the proximal segment 92 is straight while the distal segment 94 is curved, with the same radius of curvature as the first or distal arc 83. The proximal segment 92 will thus straighten the portion of the catheter body in which it resides, while the distal segment 94 will either change the radius of curvature of the portion of the catheter body in which it resides, the direction of curvature of the portion, or both, depending on the location and orientation of the distal segment 94 inside the catheter body. The cross section of FIG. 17 shows the inner tubular member 91 inserted in the catheter body 81. Comparing this Figure to the two preceding Figures, the inner tubular member is advanced just far enough that the distal end 95 of the inner tubular member is only a short distance past the location of the junction 96 of the first and second arcs of the catheter body, and the inner tubular member 91 is oriented in such a way that the distal segment 94 of the inner tubular member curves in the same direction as the first arc 83 of the catheter body. The result is that the curvature of the second arc 84 of the catheter body is reversed to extend the first arc 83 into a longer arc curving in the same direction and at the same radius of curvature. The flexible segment 93 occupies the proximal end of the second arc 84 and permits it to retain its direction and degree of curvature. The cross section of FIG. 18 shows the inner tubular member 91 advanced further into the catheter body. The entire distal segment 94 of the inner tubular member is past the location of the junction 96 of the first and second arcs of the catheter body, and the proximal segment 92 has straightened out most of the curvature of the second arc 84. The only curvature remaining from the second arc is the curvature in the region of the flexible portion 93 of the inner tubular member. Positions of the inner tubular member intermediate between those of FIGS. 17 and 18 will results in differing lengths of the arc. A composite catheter having a Sidewinder shape is formed by the components shown in FIGS. 19, 20, 21, 22 and 23. The catheter body 101 and inner tubular member 102 are shown individually in FIGS. 19 and 20, respectively. In its relaxed position as shown, the catheter body 101 can be divided into four sections. From the distal end 103, these are a slightly bent or curved distal segment 104, a straight segment 105, a spiral segment 106 (in this case forming a loop of approximately one and a half turns), and a long proximal straight segment 107. The spiral segment 106 has a radius of curvature that is monotonically decreasing as the loop proceeds in the distal direction (indicated by the arrow 108). The inner tubular member 102 consists of two relatively rigid segments, distal 111 and proximal 112, both straight, separated by a relatively flexible segment 113. As in the preceding constructions, the effect of these segments on the portions of the catheter body in which they reside will be that the relatively rigid segments 111, 112 will impose their shape on the composite catheter (in this case, straighten any curvature otherwise present in the catheter body), and the relatively flexible segment 113 will permit the shape memory of the catheter body to govern the shape of the composite catheter. Three gradations in shape of the composite catheter, achieved by advancing the inner tubular member 102 to three different depths inside the catheter body 103 are shown in FIGS. 21, 22 and 23, respectively. In each of the three gradations, the flexible segment 113 of the inner tubular member is entirely within the spiral segment 106 of the catheter body, although in FIG. 21 the flexible segment is near the distal end of the spiral segment, in FIG. 22 it is approximately midway between the distal and proximal ends, and in FIG. 23 it is near the proximal end. The relatively rigid distal 111 and proximal 112 segments of the inner tubular member straighten out all remaining portions of the spiral segment. In each case, the composite catheter retains a secondary curve 114 of 180° (π radians) or less in the region where the flexible segment is located, and a primary curve 115 at the distal end identical in curvature to the curved distal end 104 of the catheter body alone. The distance between the secondary curve 114 and d e primary curve 115 increases as the inner tubular member is retracted, and the radius of curvature of the secondary curve 114 increases due to the increasing radius of the spiral in the catheter body. Here as in the other composite catheters, the gradations in shape form a continuum. The components shown in FIGS. 24, 25, 26 and 27 are used to form a composite catheter having a Newton shape. The catheter body 121 and inner tubular member 122 are shown individually in FIGS. 24 and 25, respectively. Shown in its relaxed position, the catheter body 121 is in three segments — a straight distal segment 123, an intermediate curved segment 124 (in this case, with a constant or approximately constant radius of curvature), and a proximal straight segment 125. Note that as shown in this drawing the direction of curvature of the curved segment as one proceeds toward the distal end 126 of the catheter body is counter-clockwise, and the arc of the curved segment is about 270° (1.5ττ radians) or greater. The inner tubular member 122 is in three segments as well, with a distal straight, relatively rigid segment 131, an intermediate flexible segment 132, and a relatively rigid proximal segment 133. The relatively rigid proximal segment is straight for most of its length, except for its distal portion 134 which is curved into a 180° (τ radians) arc. The radius of curvature of the curved segment 134 of the inner tubular member is the same or approximately the same as the radius of curvature of the curved segment 124 of the catheter body. The inner tubular member 122 is purposely oriented in this drawing such that the curvature of the curved segment 134 of the inner tubular member is clockwise, i.e. , opposite that of the curved segment 124 of the catheter body. The reason is evident in FIGS. 26 and 27. Two gradations in shape of the composite catheter formed by advancing the inner tubular member 122 to different depths inside die catheter body 121 are shown in FIGS. 26 and 27. Note that the orientations shown for the individual components in FIGS. 24 and 25 are maintained in FIGS. 26 and 27. In each gradation, the flexible segment 132 of the inner tubular member 122 resides entirely within the curved segment 124 of the catheter body, permitting the corresponding portion of the curved segment 124 of the catheter body to retain both its curvature and its counter-clockwise direction of curvature. The remaining portions of the curved segment 124 of the catheter body are either straightened or forced into a curvature in the opposite (clockwise) direction by the rigid portion(s) of the inner tubular member. In FIG. 26 the straight rigid distal segment 131 of the inner tubular member straightens the curvature of the catheter body while the curved rigid segment 134 (on the proximal side of the flexible segment 132) curves the otherwise straight proximal segment 125 of the catheter body. In FIG. 27 the curved rigid segment 134 reverses part of the curvature of the catheter body and continues the curve by curving part of the otherwise straight proximal segment. In either case, the result is an S-shaped curve in the composite catheter, with the position of the S controlled by the position of the inner tubular member. As in the other composites, this composite is capable of a continuum of gradations in shape. For composite catheters of this invention in which the inner and outer tubular members curve in opposite (or otherwise divergent) directions, means for preventing angular rotation or twisting of one component relative to the other can be incorporated into the construction of the components. For example, the contact surfaces of the components can contain a mating ridge and groove, or any other similarly functioning members, that can be held in engagement by the close fit of the two tubes and that will permit relative motion in the longitudinal direction only. The catheter body, the inner tubular member or both can be either a tube with a closed and continuous circumference, or a tube with a slit along its circumference. The slit can serve the function of the groove described in the preceding paragraph, or various other functions such as providing the catheter body or inner tubular member with the ability to expand or contract. It is preferred that the combined components form a composite catheter that is fully enclosed around its circumference, whether this be due to at least one of the components being circumferentially closed or, if both have slits, then the slits being out of alignment with each other. The remaining figures illustrate a composite catheter that is alterable from an Amplatz Right shape to a Judkins Right shape with gradations in between. FIG. 28 illustrates the distal region of a catheter body 141 that approximates the Amplatz Right shape, and FIG. 29 illustrates the distal region of an inner tubular member 142 that approximates the Judkins Right shape. The portion of the inner tubular member 142 that is shown in FIG. 29 is relatively rigid compared to the portion of the catheter body 141 that is shown in FIG. 28, and is sufficiently rigid to maintain its curvature even when advanced inside the catheter body. Partial insertion of the inner tubular member, as shown in FIG. 30, therefore, gives the composite catheter the shape of the Judkins Right up to the point where the distal end 143 of the inner tubular member, with the remainder 144 retaining the shape of the catheter body. This can be referred to as a hybrid shape. Full insertion of the inner tubular member, as shown in FIG. 31, provides the composite catheter with the same shape as the inner tubular member itself, . e. , the Judkins Right shape. The composite catheters shown in FIGS. 2 through 5, 11 through 18, and 28 through 31 are particularly suitable for use as guide catheters to provide access to coronary arteries. The composite catheters shown in FIGS. 19 through 27 are particularly suitable for use as guide catheters to provide access to carotid arteries. Other composite catheters, not shown but similarly achieving gradations in shape changes by insertion of the inner tubular member to varying degrees, are within the scope of this invention and will be readily apparent to those skilled in the art. In addition to the types of shape changes shown above where one of the two components dominates the other and establishes by itself the curvature of the combined pair, the invention further contemplates catheter body and inner tubular member combinations in which both have equal or approximately equal stiffness, and the composite curvature is determined not by any single component but by both combined. The following considerations are applicable to composite catheters of this invention in general, without being restricted to any single shape or class of shapes. As noted above, the various configurations and tubular construction techniques shown in FIGS. 6 through 10 can be used to differentiate the flexible segment(s) from the rigid segment(s) in any of the inner tubular members shown in the attached drawings. Further means of differentiation will be readily apparent to those skilled in the art. Furthermore, the inner tubular member may contain gradations in rigidity or flexibility, either in a continuously varying manner or in a stepwise manner with two or more steps. Regardless of the catheter type or shape, the extended length of the catheter body will generally range from about 50 cm to about 150 cm, preferably from about 90 cm to about 110 cm. The diameter of the catheter body will most often be in the range of about 4 French (F, where IF = 0.33 mm) to about 12F, and preferably from about 6F to about 11F. The catheter body will have a lumen with a diameter of from about 3F to about 11F, preferably from about 5F to about 10F. The inner tubular member will be small enough to fit within the lumen of the catheter body with a sufficiently loose fit to be moved longitudinally inside the lumen, but large enough so that the lumen of the inner tubular member itself can accommodate a working catheter, or two or more if necessary. The shape memory of the catheter body when not under the influence of the inner tubular member may be inherent in the catheter body itself, such as by appropriate molding, tempering, or alloying techniques. Alternatively, the shape memory may be imparted and maintained by one or more spring rods (not shown in the drawings) embedded in the wall of the catheter body. The spring rods will have looped or curved segments corresponding to any looped or curved segments of the desired shape memory, and will be resilient enough that their shapes will be modified by the relatively rigid portions of the inner tubular member yet capable of resuming the curvature when the relatively rigid portions are replaced by the relatively flexible portions. Manipulation of the inner tubular member is performed at the proximal end of the catheter, outside the patient's body. Manipulation is readily performed by hand, with the operator assisted by visualization of the distal tip of the catheter. Visualization may be achieved by conventional means. Fluoroscopy, a common visualization techniques for catheters, is one example. The movement and securement of the inner tubular member relative to the catheter body can be achieved at the proximal end by simple mechanical devices. Examples are a threaded knob, a ratchet-type mechanism, or various kinds of toothed or locking mechanisms which can be manipulated by hand. Other examples will be readily apparent to those skilled in the art. One specific example is a toothed track on a stationary member to which the catheter body is mounted, and a spring-loaded catch on a mobile member to which the inner tubular member is mounted, the catch mounted through a pivot to a toothed wheel. When the wheel is pushed by the user's thumb to engage the track, the catch is lifted away from engagement with the track. Turning of the wheel while pressing it against the track by the user's thumb moves the mobile member relative to the stationary member, and release of the wheel causes the catch to engage the track, locking the members relative to each other. Many other mechanisms with a similar ease of manipulation can be substituted.

Claims: WE CLAIM: 1. A composite catheter comprising: a catheter body of resilient construction with a shape memory and a lumen; and an inner tubular member slidably receivable within said catheter body and substantially filling said lumen when so received, said inner tubular member being of resilient construction with a shape memory, and along at least a portion of its length, said inner tubular member having a degree of rigidity equal to or greater than that of said cadieter body; said shape memories selected such that sliding said inner tubular member longitudinally inside said catheter body causes said catheter body to change shape. 2. A composite catheter in accordance with claim 1 in which said inner tubular member comprises first and second portions arranged lengthwise, said first portion having a degree of rigidity greater than that of said catheter body, and said second portion having a degree of rigidity equal to or less than that of said catheter body. 3. A composite catheter in accordance with claim 1 in which said inner tubular member comprises first and second portions arranged lengthwise, said first portion having a degree of rigidity greater than that of said catheter body, and said second portion having a degree of rigidity less than that of said catheter body. 4. A composite catheter in accordance with claim 1 in which said inner tubular member has a degree of rigidity substantially equal to that of said catheter body for substantially the entire length of said inner tubular member. 5. A composite catheter in accordance with claim 1 in which said inner tubular member has a degree of rigidity greater than that of said catheter body for substantially the entire length of said inner tubular member. 6. A composite catheter in accordance with claim 1 in which said shape memory of said catheter body defines a curved segment. 7. A composite catheter in accordance with claim 6 in which said curved segment is an arc having a total angular rotation of at least about 1.25 π radians. 8. A composite catheter in accordance with claim 6 in which said curved segment is an arc having a total angular rotation of at least about 1.5ττ radians. 9. A composite catheter in accordance with claim 6 in which said curved segment is an arc having a constant radius of curvature. 10. A composite catheter in accordance with claim 6 in which said curved segment is an arc having a monotonically varying radius of curvature. 11. A composite catheter in accordance with claim 1 in which said shape memory of said catheter body defines a first curved segment, and said shape memory of said inner tubular member defines a second curved segment, said second curved segment differing from said first curved segment. 12. A composite catheter in accordance with claim 11 in which said first and second curved segments each have a constant radius of curvature and differ in total angular rotation. 13. A composite catheter in accordance with claim 11 in which said first and second curved segments differ in radius of curvature. 14. A composite catheter in accordance with claim 11 in which said first and second curved segments differ in direction of curvature. 15. A composite catheter in accordance with claim 1 in which said inner tubular member is comprised of proximal and distal regions of greater rigidity than said catheter body, separated by an intermediate region of lesser rigidity than said catheter body. 16. A composite catheter in accordance with claim 15 in which said distal region is straight. 17. A composite catheter in accordance with claim 15 in which said distal region is curved. 18. A composite catheter in accordance with claim 15 in which one of said proximal and distal regions is straight and the other is curved. 19. A composite catheter in accordance with claim 1 in which: said catheter body has a distal end and said shape memory of said catheter body defines a curved segment separated from said distal end by a distance of about 2 cm to about 7 cm and said curved segment is an arc having a total angular rotation of at least about 1.25.T radians; and said inner tubular member is comprised of proximal and distal regions that are both substantially straight and of greater rigidity than said catheter body, and are separated by an intermediate region of lesser rigidity than said catheter body, said intermediate region being shorter than said arc. 20. A composite catheter in accordance with claim 19, 21 in which said curved segment is a spiral with radius of curvature decreasing in the direction of said distal end. 21. A composite catheter in accordance with claim 1 in which: said catheter body has a distal end and said shape memory of said catheter body defines a curved segment separated from said distal end by a distance of about 2 cm to about 7 cm and said curved segment is a first arc having a total angular rotation of at least about 1.25π radians; and said inner tubular member is comprised of proximal and distal regions that are both substantially straight and of greater rigidity than said catheter body, said proximal and distal regions separated by an intermediate region of rigidity equal to or greater than that of said catheter body, said intermediate region being a second arc having a total angular rotation less than that of said first arc, said first and second arcs having equal radii of curvature. 22. A composite catheter in accordance with claim 1 in which: said catheter body has a distal end and said shape memory of said catheter body defines a first arc having a total angular rotation of substantially no greater than 0.5π radians, and a second arc distal to said first curved segment and having a total angular rotation of substantially no greater than 0.5π radians, said first and second arcs curved in opposing directions; and said inner tubular member is comprised of proximal and distal regions that are both of greater rigidity than said catheter body, and are separated by an intermediate region of lesser rigidity than said catheter body, said distal region being curved into a third arc, and said intermediate region being shorter than either of said first and second arcs. 23. A composite catheter in accordance with claim 1 in which: said catheter body has a distal end and said shape memory of said catheter body defines a first arc having a total angular rotation of substantially no greater than Q.5τr radians, and a second arc distal to said first curved segment and having a total angular rotation of substantially no greater than 0.5 T radians, said first and second arcs curved in opposing directions; and said inner tubular member is of greater rigidity than said catheter body for substantially the entire length of both said catheter body and said inner tubular member, and said shape memory of said inner tubular memory defines a third arc of substantially less than 0.5π radians and of substantially greater radius of curvature than either of said first and second arcs. 24. A composite catheter in accordance with claim 1 in which: said catheter body has a distal end and said shape memory of said catheter body defines a loop separated from said distal end by a distance of about 2 cm to about 7 cm, having a substantially constant radius of curvature, and having a total angular rotation of at least about TΓ radians; and said inner tubular member is comprised of proximal and distal regions that are both of greater rigidity than said catheter body, and are separated by an intermediate region of lesser rigidity than said catheter body, a portion of said proximal region being adjacent to said intermediate region being curved to form an arc having a radius of curvature substantially equal to that of said loop.

Inventors: GALEL ZEV, KAMDAR KIRTI, KILICCI CEM, GALEL, ZEV, KAMDAR, KIRTI, KILICCI, CEM
Applicants: GALEL ZEV, GUIDED MEDICAL SYSTEMS INC, KAMDAR KIRTI, KILICCI CEM, GALEL, ZEV, GUIDED MEDICAL SYSTEMS, INC., KAMDAR, KIRTI, KILICCI, CEM
Application year: 1996
Main classification: A61M25
IPC codes: A61M25