WO1997010870A1

WO1997010870A1 - Composite guide catheter with shaping element

Info

Publication number: WO1997010870A1
Application number: PCT/US1996/015186
Authority: WO
Inventors: Zev Galel; Cem Kilicci
Original assignee: Guided Medical Systems, Inc.
Priority date: 1995-09-22
Filing date: 1996-09-20
Publication date: 1997-03-27
Also published as: AU7242896A

Abstract

A guide catheter is formed from a combination of a tubular member with a large central lumen to accommodate working catheters, and one or more shape limiting rods insertable and movable longitudinally within the tubular member. The tubular member is resiliently flexible with a shape memory which imparts a curvature to the tubular member when it is relaxed. A reversible tensioning mechanism, operable from the proximal end of the tubular member, is used to straighten the tubular member prior to use. The shape limiting rod contains both permanently curved and flexible segments and causes the tubular member to retain a portion of its curvature when under tension. The location of this retained portion is determined by the position of the shape limiting rod inside the tubular member.

Description

COMPOSITE GUIDE CATHETER WITH SHAPING ELEMENT

CROSS REFERENCE TO RELATED APPLICATION

This application is related to United States provisional patent application no. 60/004,179, filed September 22, 1995, and hereby claims all benefits legally available therefrom. Provisional application no. 60/004,179 is incoφorated herein by reference.

BACKGROUND OF THE INVENTION

This invention resides in the technology of guide catheters, which are relatively large lumen catheters for use in cardiology, urology, gastroenterology, and other procedures involving insertion of catheters into bodily passages with curved shapes or branching. Guide catheters are specially shaped to provide a passage to a region of interest inside or at the end of the bodily passage, and their lumens are used to direct functional catheters such as therapeutic, imaging or diagnostic catheters to the region. A guide catheter specially designed for heart surgery, for example, is inserted through the vasculature and into the aorta of a patient and is preshaped in a specific manner to place the distal tip of the catheter inside one of the coronary ostia. With the catheter thus positioned, the large lumen and the pre-imposed shape of the catheter permit it to serve as a guide channel through which smaller catheters which do not have a pre-imposed shape can be advanced to the ostium and beyond to reach locations of interest inside the coronary arterial system.

Guide catheters are available in a wide 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, and others, each formed into a different shape. In addition, many of these different shapes are manufactured in gradations of size or curvature to accommodate individual patients.

One class of guide catheters illustrating these gradations are the catheters referred to as Judkins Left, which are the most widely used guide catheters for coronary procedures. 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 corresponding to 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 the catheter is inserted through the aorta, the "J" shape is distorted to follow the aortic arch, but the portion extending from the secondary 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 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 a guide catheter of d e 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 cadieter 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 procedures as well as other involving the use of guide catheters, therefore, operating rooms are equipped with a full range of sizes so that quick exchanges can be made as needed.

Since measurements of these bodily passages cannot be taken prior to selecting the appropriate guide catheter, the physician often relies on certain visualization means incorporated in the catheter itself to determine that the catheter is properly positioned. If the catheter cannot be properly positioned, it must be removed and replaced with one of a different size, and this may have to be repeated until an acceptable angle is achieved. This presents disadvantages to the procedure. Cost, for example, is a critical factor in these procedures, and each exchange increases the cost to the patient. In addition, the risk of infection is increased since the major potential sources of infection are skin contaminants and contamination from the operators, both which are introduced at the insertion site. Also, the risk of trauma to the vessels receiving the catheters is increased when multiple insertions are performed.

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 guide catheter with a curvature which can be modified in a variety of ways, including extending or shortening its length as well as moving it to different locations along the longitudinal axis of the catheter, all such manipulations capable of being performed while the catheter is in place inside the bodily vessel.

The catheter of the present invention is of a composite construction, and includes a tubular member which is flexible but resilient plus one or more shape limiting rods capable of insertion into the tubular member and of longitudinal movement within the tubular member from the proximal end. The tubular member is the shell of the guide catheter and has a shape memory which includes a curved segment close to the distal end of the member. The length of the curved segment is greater than the length of the curvature that the guide catheter as a whole will assume when in use, and only a portion of the full curvature of the segment will be retained when guide catheter is assembled and operative. The choice of which portion of the curvature in the shape memory is to be retained and the removal of the remaining portion or portions are achieved by the combined effect of two elements — a reversible straightening mechanism which overrides the shape memory of the tubular member and tends to straighten out the curved segment, and the one or more shape limiting rods, which override the straightening mechanism along a limited length of the tubular member. Each shape limiting rod contains a minimum of two segments. One or these segments is curved and relatively rigid, its curvature at least approximately congruent with, i.e. , conforming to, the curvature of the curved segment of the tubular member, but shorter in length. The other segment is flexible. The curved rigid segment overrides the straightening mechanism and thereby retains the curvature of the tubular member for the portions of the member through which this segment passes. The flexible segment, in contrast, is susceptible to straightening by the straightening mechanism, and the portions of the tubular member in which this segment resides will straighten upon actuation of the mechanism. Thus, the assembled guide catheter, with the straightening mechanism in use, will have a curved segment have a curvature and length equal to that of the curved rigid segment of the shape limiting rod, and the lengths of any straight segments of the guide catheter, including those which are distal to the curved segment as well as those which are proximal, will be determined by the longitudinal position of the shaping rod within the tubular member.

These and other features and advantages of the invention will be explained in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a tubular member as one component of a composite guide catheter in accordance with the present invention.

FIG. 2 depicts a shape limiting rod as a second component of a composite guide catheter in accordance with the present invention.

FIG. 3 depicts the tubular member of FIG. 1 and the shape limiting rod of FIG. 2 assembled. FIG. 4 depicts the tubular member of FIG. 1 and the shape limiting rod of FIG. 2 assembled and in a tensioned configuration.

FIG. 5 depicts one example of a shape limiting rod in accordance with the present invention, the view shown in partial cross section.

FIG. 6 depicts a second example of a shape limiting rod in accordance with the present invention.

FIG. 7 depicts a third example of a shape limiting rod in accordance with the present invention.

FIG. 8 depicts a composite guide catheter of the present invention in transverse cross section. FIG. 9 depicts a series of composite guide catheters of the present invention in position inside an aorta.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The curvature in the tubular member as defined by the shape memory may be any type of non-linearity, depending on the type and configuration of bodily vessel or passage in which the catheter of the present invention is to be inserted, or on the particular known type of guide catheter which the catheter of the invention is intended as a substitute for. The curvature may thus be a wave-form curvature, a loop, a partial wave or loop, a loop with multiple turns, or any other kind of non-linear form. Loop-type curvatures can vary in terms of the number of turns, the radius of curvature of the loop, whether the radius is constant or varied along the length of the loop, and the location of the loop along the longitudinal axis of the tubular member.

The curvature in the rigid or permanently curved segment of the shape limiting rod is preferably selected to conform, at least approximately, to a portion of the curvature in the shape memory of the tubular member. If the shape memory curvature is a loop, for example, the permanently curved segment of the rod may be an arc of the loop. Other examples will be readily apparent. In preferred embodiments of the invention, the length of the permanently curved segment of the rod is from about 0.1 to about 0.8 times the length of the curved segment of the shape memory of the tubular member.

In preferred embodiments of the invention, the permanently curved segment of the rod is at the distal end of the rod, with the flexible segment immediately proximal to the permanently curved segment. In further preferred embodiments, the rod contains a third segment proximal to the first two and extending to the extreme proximal end of the rod. This third segment preferably has a flexibility substantially less than that of the second or flexible segment, and potentially as inflexible as the first or permanently curved segment. For guide catheters of this invention which are designed as replacements for Judkins Left guide catheters, the curved segment defined by the shape memory of the tubular member is a loop, which corresponds to the secondary curve in the Judkins Left catheter. The total angular rotation of the loop (i.e. , in its relaxed or untensioned form) exceeds the angular rotation of the secondary curve. In certain preferred embodiments of the invention, the loop has a total angular rotation of at least about 1.25x radians, and most preferably at least about 1.5x radians. Expressed in terms of lengths following the curvatures (i.e. , uncurved lengths), the loop in preferred embodiments of the invention is about 15 mm to about 100 mm in lengm, most preferably about 25 mm to about 75 mm in length. By contrast, the permanently curved segment of the shape limiting rod in preferred embodiments of the invention is about 5 mm to about 50 mm in length, most preferably about 15 mm to abtou 40 mm in length. The rod segment in these embodiments is at least about 5 mm shorter in length than the loop length, and most preferably at least about 15 mm shorter.

The loop is separated from me distal end of the tubular member by a distance corresponding to the lower limit of the desired range for the distance between the primary and secondary curves of the Judkins Left. In preferred embodiments of the invention, this distance is about 10 cm or less, more preferably about 1 cm to about 10 cm, and most preferably about 3 cm to about 7 cm. When the shape limiting rod is inserted in the tubular member far enough so that the permanently curved region of the rod resides within the loop, the portion of the loop in which the permanently curved region of the rod resides will remain curved when the tensioning mechanism is actuated while the remainder of the loop will be straightened. The location of the permanently curved region of the rod thus establishes the location of the secondary curve of the guide catheter, and the tubular member assumes the "J" shape characteristic of Judkins Left catheters only when the rod is inserted and the tension applied.

The shape limiting rod can be retained by the mbular member in a variety of ways. For example, the rod can pass through the central lumen of the catheter which serves as a channel for additional catheters serving any of a wide variety of functions. As another example, the rod can fit within a smaller diameter lumen in the mbular member parallel to and separate from the larger central lumen, leaving the central lumen fully open for the additional or functional catheters. In either case, the rod can then be slid back and forth within its lumen to move the permanently curved region of the rod relative to the mbular member, and thereby move the location of the curvature which will be retained when the remainder of the tubular member is straightened. This manipulation can be done manually from the proximal end of the catheter after the catheter has been placed in position with its distal region in the bodily passage. For coronary applications, this procedure can be done with the distal region of the catheter in the ascending aorta.

The tensioning mechamsm straightens all segments of the mbular member other than the segment in which the permanently curved segment of the shape limiting rod resides. This includes any portions of the curved segment of the mbular member which are distal to the permanently curved segment of the rod as well as any which are proximal. Even when under tension, however, the mbular member as a whole, including the regions proximal to the curved segment, retain a certain degree of flexibility to permit the composite catheter to conform to the curvature of bodily passages which the catheter must pass through to reach the region of interest. In the case of coronary surgery, sufficient flexibility is retained to permit the catheter to follow the curvature of the aortic arch. All segments of the tensioned catheter retain sufficient stiffness, however, to stabilize the catheter when it is in position. The tensioning mechanism is preferably one which applies tension to the mbular member in an internal manner, and this may be achieved in a variety of ways. A preferred method, as described in detail below, is the use of a high pressure fluid within a lumen internal to the rod itself.

The extended length of the mbular member will generally range from about 50 cm to about 150 cm, preferably from about 90 cm to about 110 cm. The diameter of the member will most often be in the range of about 4F to about 12F (where "F" designates French; IF = 0.33 mm), and preferably from about 6F to about 11F. The central lumen of the mbular member will most often have a diameter of from about 3F to about 11F, preferably from about 5F to about 10F. The lumen will be large enough to permit the insertion and withdrawal of working catheters in general, such as angioplasty catheters, atherectomy catheters, laser ablation catheters, imaging catheters, and other types of interventional catheters serving therapeutic and diagnostic functions. The concepts of the invention can be embodied in catheter constructions ranging widely in shape, size and configuration. To promote a better understanding of the invention, however, the following discussion will address the constructions shown in the drawings, which represent specific examples within the more general concepts of the invention. FIG. 1 illustrates a tubular member 11 in accordance with the invention. The mbular member has a shape memory and is shown in a relaxed condition, i.e. , without a shape limiting rod inserted and in the absence of tension. As shown, the mbular member includes a distal tip 12 with a slight bend, a loop 13, a relatively straight segment 14 between the distal tip 12 and the loop, and another relatively straight segment 15 extending from the proximal end of the loop to the proximal end of the mbular member. In a presently preferred embodiment, the loop has a total angular rotation of about 3.33ιr radians (600°), and the radius of curvamre is from about 5 mm to about 20 mm, preferably about 10 mm.

FIG. 2 illustrates a shape limiting rod 21. The rod includes a permanently curved segment 22 at its distal end, a flexible segment 23 immediately proximal to the permanently curved segment 22, and a somewhat stiffer segment 24 forming the remainder of the rod. The permanently curved segment 22 has the same curvamre as the loop 13 of the mbular member in FIG. 1, but is shorter, forming an arc of about lx radians (180°). This segment is formed from material which is inherently stiff, either by tempering or by chemical composition, and in any event, sufficiently stiff to retain its curvamre when subjected to the tensioning force which is applied to the mbular member. The stiff proximal segment 24 can be less stiff than the curved segment 22, and its stiffness is less critical to the operation of the catheter. The stiffness of the proximal segment 24 serves primarily to facilitate the insertion of the rod in the mbular member, as well as any longimdinal adjustments which are to be made to the rod once inside the mbular member. The proximal segment can be rendered stiff by the same means as the curved distal segment 22.

FIG. 3 illustrates the assembled guide catheter, with the shape limiting rod 21 inserted in the mbular member 11, and without tension applied. The shape limiting rod 21 has been inserted to a distance whereby its distal end 25 is more than halfway inside the loop 13 of the mbular member, and whereby the flexible segment 23 of the rod is also partially within the loop. The flexible segment 23 by virtue of its flexibility conforms to the curvamre of the loop. FIG. 4 illustrates the assembled guide catheter of FIG. 3 with tension applied to the mbular member. The tendency of the tension is to straighten the mbular member entirely, up to but not including the bend 12 at the distal end (which serves as the primary curve of the catheter), but the permanently curved segment 22 of the shape limiting rod prevents straightening in the portion of the mbular member in which this segment resides, thereby forming the secondary curve 26 of the catheter. The distance of the straight segment 27 between the secondary curve 26 and the primary curve 12 will thus depend on how far d e shape limiting rod has been inserted into the mbular member.

Examples of shape limiting rods are shown in FIGS. 5, 6 and 7. In the example of FIG. 5, the distal permanently curved segment 31 and the proximal straight segment 33 are separated by a flexible segment 32 which consists of a coil spring 34 coiled around a central wire 35 (the view is shown in partial cross section to expose the wire). The coil spring 34 has no stiffness in any direction perpendicular to the length of the rod and will bend or curve in any transverse direction. When placed inside a lumen of similar diameter, the coil spring 34 together with the central wire 35 can push or pull the distal segment 31. The distal segment 31 and the proximal segment 33 as well as the spring 34 and wire 34 can be made of a solid metallic material, such as stainless steel or aluminum, appropriately tempered, or nonmetallic materials. The outer diameter of the coil spring 34 is approximately equal to the outer diameters of the stiffer proximal and distal segments of the rod to minimize any discontinuities and thereby facilitate the longimdinal sliding of the rod inside the mbular member.

In the rod construction shown in FIG. 6, the proximal segment 41 and the distal 43 segment are identical to those of the rod of FIG. 5. The flexible segment 42 has a smaller diameter and is flexible for this reason. All segments may be of solid metallic composition, with the same metal or alloy being used for each. Alternatively, the rod may be formed of a polymeric material which can be softened by heat and drawn to a small diameter.

In the rod construction shown in FIG. 7, the proximal 51 and distal 53 segments are again identical to those of the rods of FIGS. 5 and 6. The flexible segment 52 is formed from a material of construction which differs from that of the other two segments, the material of the flexible segment being one which is inherently more flexible than the material used for the others. The difference in flexibility may be achieved by using different metal alloys or different polymers, or by using composites of different compositions, or by the same metallic materials or polymers treated differently to achieve different grain sizes, molecular chain lengths, or differences in any other parameter which affects flexibility. As in the embodiment of FIG. 5, it is preferred that the three segments have the same outer diameter for ease of movement within the mbular member. The number of shape limiting rods used with a single mbular member may vary . The use of two or more of these rods offers advantages of increased control and less stress on individual rods, with a lowered risk of breakage. The use of two or more rods also offers the option of advancing the rods to differing depths within the mbular member, and thereby varying the length of curvature retained when tension is applied to the mbular member. In the assembled catheter shown in FIG. 4, for example, the retained curve 26 may be lengthened or shortened by the use of two overlapping rods where the degree of overlap is varied by advancing one rod relative to the other(s).

The shape memory of the tubular member may be inherent in the mbular member itself. Alternatively, the shape memory may be imparted and maintained by one or more rods separate from the shape limiting rods. These rods, which may be termed "spring rods," may be held stationary, and preferably embedded or otherwise affixed, inside the mbular member so that their position within the mbular member is not variable. The spring rods will have a curved segment corresponding to the curved segment desired in the shape of the mbular member, plus a resiliency which permits their curvamre to be overcome by the tensioning mechanism, and to regain the curvamre when the tension is removed.

Methods by which the shape limiting rods and the spring rods are retained inside the mbular member may vary. This is true of spring rods as well. The central lumen of the mbular member can serve as a conduit for insertion of these rods, while still leaving room for working catheters. This is less preferred, however, than the use of separate lumens.

An example of a mbular member with separate lumens for the working catheters, straightening rods and spring rods is shown in FIG. 8. The central lumen 61 through which the working catheters pass is approximately circular in cross section, preferably of the dimensions cited above, and is slightly eccentric relative to the mbular member 62 itself. Adjacent to the central lumen are a wide, shallow lumen 63 which accommodates three shape limiting rods 64, 65, 66, and two small lumens 67, 68 of circular cross section, each of which accommodates a spring rod 69, 70. The wide, shallow lumen 63 provides a relatively loose fit for the shape limiting rods 64, 65, 66 to permit the shape limiting rods to be slid readily along the length of the lumen by hand from the proximal end of the catheter. The spring rod lumens 67, 68 may be of a tighter fit since the spring rods will generally be inserted by the manufacturer and will not be manipulated by the user during the typical medical procedure. The lumens for the both types of rods are preferably positioned on the side of the mbular member facing the loop or other curvamre. Manipulation of the shape limiting rod(s) is performed at the proximal end of the mbular member, 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, for example, is one of the most common such means and can be used conveniently in the present invention. Movement and securement of a straightening rod relative to the mbular member can be achieved at the proximal end by simple mechamcal means. Examples are a threaded knob, a ratchet- type mechamsm, or various kinds of toothed or locking mechanisms which can be manipulated by hand and would be readily apparent to those skilled in the art. One presently favored strucmre is a toothed track on a stationary member to which the mbular member is mounted, and a spring-loaded catch on the mobile member to which the straightening rod is mounted, the catch mounted through a pivot to a toothed wheel. When the wheel is depressed by the user's thumb to engage the track, the catch is lifted out of 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 can be substituted for similar ease of manipulation. A preferred tensioning mechanism for the tubular member is the application of a pressurized fluid to a lumen extending the length of the mbular member. The fluid may be water, physiological saline, air, or any other liquid, gas or gel, preferably one which is compatible with a physiological system, and the fluid is then pressurized. The lumen may be permanently filled with fluid but at a variable pressure controlled from the proximal end of the mbular member. When the pressure is raised to a superatmospheric level, the mbular member extends and rigidifies. The source of pressurization will be external to the patient's body. Conventional pumps, pressure gauges and pressure regulators of the types included in equipment used in medical clinics can be used. The lumen to which the pressurized fluid is applied may be a separate lumen, or it may be one of the lumens used for either the spring rods or the shape limiting rods. The lumen may extend the full length of the mbular member, or it may terminate at the distal end of the curved segment of the mbular member.

To illustrate the application of the concepts of this invention to a catheter serving the function of a Judkins Left catheter in coronary surgery, FIG. 9 illustrates the assembled guide catheter in position, with tension applied. The distal region of the catheter is in the aorta, close to the aortic root 81, and the distal tip 82 is inside the ostium 83 of the right coronary artery. The catheter is shown in various gradations of shape 84, 85, 86, 87, with corresponding gradations in the location of the secondary curve 88 along the aortic wall, and in the approach angle a of the catheter toward the ostium 83. These gradations are the result of differences in the distance between the secondary curve 88 and the catheter's distal tip 82, and are achieved by moving the shape limiting rod relative to the mbular member. The foregoing is offered primarily for purposes of illustration. It will be readily apparent to those skilled in the art that the number of components, their shapes, materials of construction, methods of use and arrangement in the composite guide catheter described herein may be further modified or substimted in various ways without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A composite guide caϋ eter, comprising: an elongate mbular member having a proximal end and a distal end, said mbular member being resiliently flexible and having a shape memory defining a curved segment; straightening means reversibly actuatable from said proximal end for reversibly straightening said curved segment; receiving means in said tubular member and extending into said curved segment for receiving a rod and for permitting longimdinal movement of a rod so received from said proximal end; a shape limiting rod capable of being received within said receiving means, comprising: a first rod segment curved substantially congruently with a poπion of said curved segment and sufficiently rigid to prevent said straightening means from straightening any portion of said curved segment that said first rod segment is positioned in; and a second rod segment sufficiently flexible to permit said straightening means to straighten any portion of said curved segment that said second rod segment is positioned in.

2. A composite guide catheter in accordance with claim 1 in which said shape limiting rod has distal and proximal ends, said first rod segment is adjacent to said distal end of said shape limiting rod, and said second rod segment is proximal relative to said first rod segment.

3. A composite guide catheter in accordance with claim 2 in which said shape limiting rod further comprises a third rod segment which is substantially straight and of substantially the same rigidity as said first rod segment.

4. A composite guide catheter in accordance with claim 1 in which said straightening means comprises means for supplying pressurized fluid to said mbular member.

5. A composite guide catheter in accordance with claim 1 in which said straightening means comprises a lumen in said mbular member extending from said proximal end to a least through said curved segment, and means for supplying pressurized fluid to said lumen.

6. A composite guide catheter in accordance with claim 1 in which said mbular member contains an axial lumen extending the full length of said tubular member for passage of functional catheters selected from therapeutic and diagnostic catheters.

7. A composite guide catheter in accordance with claim 6 in which said receiving means comprises a second lumen separate and distinct from said axial lumen and extending from said proximal end of said mbular member to a least through said curved segment.

8. A composite guide catheter in accordance with claim 7 in which said straightening means comprises said second lumen plus means for supplying pressurized fluid to said second lumen.

9. A composite guide catheter in accordance with claim 1 in which said first rod segment is of a length ranging from about 0.1 to about 0.8 of the length of said curved segment of said elongate tubular member.

10. A composite guide catheter in accordance with claim 1 in which said curved segment is a loop having a total angular rotation of at least about 1.257T radians.

11. A composite guide catiieter in accordance with claim 1 in which said curved segment is a loop having a total angular rotation of at least about 1.5x radians.

12. A composite guide catheter in accordance with claim 10 in which said loop has an uncoiled length of from about 15 mm to about 100 mm, and said first rod segment is from about 5 mm to about 50 mm in length and is at least about 5 mm shorter tiian said uncoiled length of said curved segment.

13. A composite guide catheter in accordance with claim 10 in which said loop has an uncoiled length of from about 25 mm to about 75 mm, and said first rod segment is from about 15 mm to about 40 mm in length and is at least about 15 mm shorter than said uncoiled length of said curved segment.

14. A composite guide catheter in accordance with claim 1 in which said curved segment is separated from said distal end by at most about 10 cm.