PATENT ABSTRACT
A catheter having an elongate body including a central lumen adapted to slidably receive a therapeutic catheter. The catheter includes a soft tip adapted to lodge in the ostium of the right coronary artery. The elongate body is formed near the distal end to impinge against the wall of the aorta opposite the ostium of the coronary artery.

PATENT DESCRIPTION
This application is a continuation of U.S. application Ser. No. 09/235,077, filed Jan. 21, 1999 now U.S. Pat. No. 6,110,163, which in turn is a divisional of application Ser. No. 08/926,129, filed Sep. 9, 1997 now U.S. Pat. No. 5,868,700, which in turn is a continuation of application Ser. No. 08/558,006, filed Nov. 13, 1995 now U.S. Pat. No. 6,120,4951, which in turn is a continuation of application Ser. No. 08/190,149, filed Feb. 4, 1994 now abandoned, which in turn is a Rule 371 National Phase Filing of PCT/US93/04031, with an International Filing Date of Apr. 29, 1993, which in turn is a continuation-in-part of application Ser. No. 07/877,288, filed May 1, 1992, now U.S. Pat. No. 5,306,263. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to catheters adapted to be inserted into the cardiovascular system of a living body and, more particularly, to a preshaped catheter having an improved distal end portion for providing more precise access to the right main coronary artery of the cardiovascular system. 
     Catheters are often used in the performance of medical procedures such as coronary angiography for injecting dye, or the like, into the cardiovascular system for diagnosis; and angioplasty to widen the lumen of a coronary artery which has become at least partially blocked by a stenotic lesion causing an abnormal narrowing of the artery due to injury or disease. In these techniques the distal end of a therapeutic catheter is introduced into the aorta by way of the femoral artery. The proximal end of the catheter is then manipulated so its distal end is inserted into the lumen of a selected coronary artery branching off from the aorta. A typical treatment procedure would involve initially inserting a guiding catheter into the cardiovascular system in the above manner, followed by the introduction of a suitable therapeutic device, such as a dilating catheter, a laser catheter, an atherectomy catheter, or the like. The therapeutic catheter is guided through the guiding catheter until its distal end portion is positioned adjacent the stenotic lesion in the coronary artery for use in reducing the blockage in the artery. In all such medical procedures, it is absolutely essential that the guiding catheter has the appropriate shape for proper alignment of its distal end relative to the coronary artery. 
     The most common catheter used in treatment of the right main coronary artery is what is often referred to as a “Judkins” catheter, which has a specially shaped distal end portion for facilitating insertion and engagement into the right coronary artery. However, there are some significant disadvantages to the “Judkins” catheter, such as its frequent inability to align perfectly coaxially with the selected artery and thus permit optimal treatment, and its inability to adequately support other therapeutic devices such as balloon catheters. Also, the Judkins catheter requires a 180 degree rotation and adroit manipulation to selectively engage its distal end in the right main coronary artery, which makes it more difficult to use effectively and efficiently. 
     In FIGS. 1A and 1B of the drawings, the reference numerical  10  refers, in general, to a well known prior art catheter, commonly referred to as a “Judkins” catheter. The catheter  10  is in the form of an elongated tubular member having a straight portion  12  (shown partially in FIGS. 1A and 1B) and a distal end portion. The distal end portion consists of a tertiary curved portion  14 , a secondary curved portion  16 , a primary curved portion  18 , and a tip portion  20 . The tertiary curved portion  14  extends from the straight portion  12  and is bent to form a curve of approximately 30°. The secondary curved portion  16  extends from the tertiary curved portion  14  and is bent in the opposite direction to the tertiary curved portion  14  to form a curve of approximately 30°. The primary curved portion  18  extends from the curved portion  16  and is bent to form a curve of approximately 90° and the tip portion  20  extends from the curved portion  18 . According to a typical Judkins catheter the curved portions  14  and  16  would have a radius of curvature of 10 and 5 centimeters (“cm.”), respectively, and the tip portion  20  would have a length of 1 cm. The catheter  10  is usually fabricated of a plastic material selected to exhibit flexibility and softness yet permit adequate “torque control” (i.e., the ability to transmit twisting forces along its length) so that it can be located and maneuvered precisely within a cardiovascular system by skilled manipulation of its proximal end, as will be described. 
     A typical cardiovascular system is shown in FIGS. 1C and 1D and is referred to, in general, by the reference numeral  22 . The system  22  includes an aorta  24  comprised of a descending aorta  24   a , an ascending aorta  24   b , and an aortic arch  24   c  which extends from the descending aorta  24   a  to the ascending aorta  24   b  over a curve of approximately 180°. The ascending aorta  24   b  then branches through a right ostium  26  and a left ostium  27  into a right coronary artery  28  and a left coronary artery  30 , respectively. An aortic valve  32  extends between the right coronary artery  28  and the left coronary artery  30  and is connected to the heart (not shown). As better shown in FIG. 1D, the right coronary artery  28  and the left coronary artery  30  are normally angularly spaced approximately 120°. 
     The prior art Judkins catheter  10  of FIGS. 1A and 1B is designed for use as a diagnostic catheter in the right coronary artery  28  but is also used as a guiding catheter for treatment of stenotic lesions, or the like. To this end, the catheter  10  is inserted into the system  22  and is manipulated so that, ideally, the tip portion  20  of the catheter  10  is positioned through the ostium  26  and into the lumen of the right coronary artery  28  and used to guide other therapeutic devices such as balloon, laser or atherectomy catheters, or the like (not shown) into the right coronary artery  28 . 
     To assist in advancing the catheter  10  through the system  22 , a relatively stiff wire is initially inserted into the catheter  10  to straighten it. After the catheter is inserted into the ascending aorta  24   b , the wire is withdrawn, causing the catheter to position itself along the wall of the ascending aorta  24   b , 1 to 2 cm. above the ostium  27  of the left coronary artery  30 . As a result, the tip portion  20  of the Judkins catheter  10  points away from the ostium  26  of the right coronary artery  28  and must be rotated 180°. During this rotation, the catheter  10  will suddenly descend about 3 cm. until the tip portion  20  hopefully aligns with the ostium  26  of the right coronary artery  28  in a coaxial relationship as shown in FIG.  1 C. 
     However, due to the particular configuration of the Judkins catheter  10 , the tip portion  20  is often misaligned with the ostium  26  of the right coronary artery  28  and is not located coaxially with the latter artery. Thus, when an inner catheter or therapeutic device such as a balloon catheter (not shown) is passed through the catheter  10 , the former often strikes the wall of the ascending aorta  24   b  or the right coronary artery  28  increasing the risk of damage. Also, due to the fact that the curved portion  18  is positioned adjacent to the wall of the ascending aorta  24   b  which contains the ostium  26  of the right coronary artery  28  and is a considerable distance from the wall of the ascending aorta  24   b  opposite the ostium  26 , the catheter  10  does not provide support for other catheters or devices that are passed through the catheter  10 . This problem is described in depth in Danforth U.S. Pat. No. 4,909,787. Due to the lack of support, when axial forces are exerted on the tip portion  20 , such as when a dilation balloon is advanced, the tip portion  20  has a tendency to push back from the ostium  26  causing the tip portion  20  to dislodge from the lumen of the right coronary artery  28  and the therapeutic device to prolapse in the ascending aorta  24   b . Thus, the therapeutic device loses its preferred orientation within the ascending aorta and right coronary artery. After this occurs, further advancement of the therapeutic device becomes nearly impossible because the Judkins catheter no long provides adequate support to the highly flexible shaft of the therapeutic device as one attempts to push the therapeutic device across the tight stenosis. 
     The lack of “backup” support happens because the Judkins catheter was not originally intended to serve as a conduit for other therapeutic devices into a patient&#39;s arterial system. Rather, the Judkins catheter was designed and configured merely to provide a means for introducing contrast fluid into the aortic root and main coronary artery region. 
     Various attempts to address these problems are described in the prior art. One of these attempted solutions is the Arani Double Loop guiding catheter. This catheter is illustrated and described in Arani, A New Catheter For Angioplasty of the Right Coronary Artery and Aorto-Coronary Bypass Grafts, Catheterization and Cardiovascular Diagnosis 11:647-653 (1985) and in a videotape publication, Select Curve Guiding Catheters: Cannulating the Right Coronary Artery, USCI/C.R. BARD (1988). 
     In FIGS. 2A,  2 B and  2 C, the Arani-type Double Loop guide catheter for the right coronary artery is presented to illustrate its use and the attendant difficulties and deficiencies of the Arani-type catheters for catheterization of the right coronary artery when used for angioplasty. 
     The Arani catheter is shown in FIG. 2A in a relaxed or “equilibrium” state prior to insertion into the cardiovascular system. The Arani-type Double Loop guide catheter includes a first straight proximal portion  402 , a secondary curve portion  404 , a second straight distal portion  406 , a primary curve portion  408 , and a distal tip straight portion  410  having a tip  412 . 
     The Arani-type Double Loop catheter  400  is shown disposed in a cardiovascular system  500  from a left anterior oblique (LAO) view as seen under fluoroscopy by the physician as shown in FIGS. 2B and 2C. The cardiovascular system includes a descending aorta  502 , an aortic arch  504 , and head and neck vessels  506  extending from a roof  508  of the aortic arch  504 . The aortic arch also has a floor  510 . The cardiovascular system  500  further includes an ascending aorta  512  having an antero-lateral wall  514  and a postero-medial wall  516 . A right main coronary artery  518  extends from the antero-lateral wall  514  of the ascending aorta and has an ostium  520  defining the interface between the ascending aorta  512  and the right coronary artery  518 . A left main coronary artery  522  extends from the opposite wall of the ascending aorta  512  and has an ostium  524 . A Sinus of Valsalva  526  extends below both the ostia of the left and right coronary arteries. The Sinus of Valsalva defines an area behind each cusp of the aortic valves where the aortic vessel wall bulges outward, forming a pouch-like dilatation. The Sinus of Valsalva  526  has a diameter wider than the diameter of the ascending aorta and have a wall having a curvature greater than that of the ascending aorta. 
     For use, the Arani catheter  400  must be first be maneuvered into the aortic complex. This is accomplished by advancing the catheter  400  over a stiff guide wire into the ascending aorta  412  to prevent the tip  412  from entering the great neck arteries. After removing the guide wire, the tip  412  typically is positioned against the antero-lateral wall  514  of the ascending aorta  512 . With some downward or upward movement, the tip  412  will usually enter the ostium  520  of the right main coronary artery  518 . As seen in FIG. 2B, the tip  412  of the Arani catheter  400  is marginally intubated into the ostium  520  of the right coronary artery  518 . 
     The Arani catheter offers two ways to use the catheter to get backup support. The first way is the “fulcrum position” (FIG. 2B) where the tip of the Arani catheter is intubated into the ostium of the right coronary artery and a portion of the straight arm of the catheter is anchored against the opposite ascending aortic wall. The second way is the “buttressed position” (FIG. 2C) where the tip of the Arani catheter is positioned in the ostium of the right coronary artery, and then the catheter is advanced distally so that the secondary curve of the catheter contacts the antero-lateral wall of the aorta. As seen in FIG. 2B, the fulcrum position is achieved by pulling the catheter  400  proximally backward, with the tip  412  engaged in the ostium  520 , so that the straight portion  406  of the catheter  400  contacts the postero-medial wall  516  of the ascending aorta  512 . In addition, a more proximal portion of the catheter (the first straight proximal portion  402 ) contacts some portion of the wall (floor) of the proximal portion of the aortic arch  510 . In this fulcrum position, the Arani catheter  400  attempts to provide backup support by gaining leverage off the postero-medial wall  516  of the ascending aorta. This leverage is created by pulling proximally backward on the catheter  400  which causes the tip  412  of the catheter  400  to tend to further seek the ostium  520 . This leveraging is intended to counter stenotic pushback forces acting to push the tip  412  out of engagement with the ostium  520  of the right coronary artery  518 . 
     However, the Arani catheter  400  when used in the fulcrum position has several major disadvantages. First, the Arani catheter  400  as used in the fulcrum position lacks stability. The catheter is limited from making substantially contiguous contact with the postero-medial wall  516  of the ascending aorta  512  and the inner wall (floor  510 ) of the aortic arch  504  throughout its length because the 90° secondary curve portion  404  forms such a relatively sharp bend in the catheter. This lack of contact created by the sharp bend provides less frictional engagement for the catheter to resist slippage when countering stenotic pushback forces. Second, this relatively sharp secondary curve of the catheter  400  in use inhibits achieving a direct and positive correspondence between advancement of the proximal end of the catheter and advancement of the tip  412  of the catheter into the ostium. This relatively severe bend retained in the catheter  400  in use distorts the 1:1 tip response that might otherwise occur in a catheter with relatively smooth curves along its entire length, from the proximal end to the distal end. 
     A third major disadvantage of using the Arani catheter in the fulcrum position is a lack of direct superior backup support which is created by negative correspondence between advancement of the proximal end of catheter and advancement of tip of catheter. As the Arani catheter  400  is moved into the fulcrum position, the tip moves distally forward but the heel (the proximal end of the primary curve of the catheter) moves away from a distal portion  517  of the postero-medial wall  516  of the ascending aorta to hang suspended in the ascending aorta adjacent the ostium  524  of the left coronary artery  522 . This negative correspondence between advancement of the catheter&#39;s proximal end and the catheter&#39;s tip is a result of the fulcrum effect created by the balancing of the straight segment on the postero-medial wall  516 . Moreover, in this fulcrum position the tip  412  can prolapse, i.e., become disengaged from the ostium  520 , because there is no direct support because of the lack of contact between the heel of the catheter  400  and the distal portion  517  of the postero-medial wall  516  of the ascending aorta  512 . Accordingly, when a tight stenosis is encountered during angioplasty, the stenotic pushback forces can overcome the countering forces provided by the fulcrum effect of the Arani-type catheter  400 . 
     Thus, although one can achieve and maintain deeper coaxial intubation of the tip of the Arani catheter  400  using the fulcrum technique, one sacrifices backup support because the catheter will react by moving the heel away from the postero-medial wall of the ascending aorta. Conversely, one could maintain greater contact between the heel of the catheter  400  and the postero-medial wall but would then sacrifice stable coaxial intubation. Accordingly, the Arani catheter  400  cannot simultaneously achieve the optimal combination of coaxial intubation of the tip and superior backup support desirably achieved by direct and stable contact of a heel of a catheter with the postero-medial wall  516 . 
     This failure to achieve this optimal combination results from the inefficient configuration of the single straight tip portion  410 . As the tip is further intubated into the ostium  520 , the straightness and relative rigidity of tip portion  410  prevents the catheter  400  from adapting to achieve substantial and stable contact between any significant portion of the catheter  400  (usually the heel of the catheter) and the wall of the ascending aorta  512 . The straightness of tip portion  410  “pulls” the heel of the catheter  400  downward to hang suspended in the ascending aorta, as opposed to the straight tip portion  410  having some curvature and the ability to flex in order to maintain backup support from the heel of the catheter during further intubation of the tip. 
     The straightness of straight tip portion  410  and the acute primary curve portion  408  also makes the Arani-type catheter  400  undesirable to use because they make the catheter  400  generally inconvenient to intubate the right main coronary artery  518 . Because of the length and straightness of portion  410  and the 90° (or 75°) sharp angle of the primary curve portion  408 , these portions of the catheter  400  frequently do not permit quick and easy upward or downward movement (or minimal rotation) of the tip  412  without some “lurching” of the catheter  400 , i.e., the catheter catching the wall of the ascending aorta  512  during such up or down movement and then releasing forcefully because of the stored energy from “catching” the wall. This occurs because the tip portion  410  is generally designed to equal or slightly exceed the width of the ascending aorta  512  such that the tip  412  may easily lodge into the ascending aortic wall causing the primary curve to buckle and store energy as the catheter is further advanced. This is just one of the many problems that make the Arani catheter hard to manipulate. 
     As seen in FIG. 2C, the buttressed position is achieved by distally advancing the Arani catheter  400  so that the secondary curve  404  of the catheter  400  contacts the antero-lateral wall  514  of the ascending aorta  512 . As the catheter  400  is advanced to this position, the primary curve  408  of the catheter drops lower into the ascending aorta to be positioned within the Sinus of Valsalva  526  below the ostium  524  of the left coronary artery  522 . In this buttressed position, the straight portion  406  proximal of primary curve  408  of the catheter barely contacts the postero-medial wall  516  of the ascending aorta  512  and the primary curve  408  hangs suspended within the ascending aorta  512 . Any stenotic push back forces placed on the guide catheter are, in the first instance, directed downward toward the aortic valve through the straight portion instead of being directed across the ascending aorta to the postero-medial wall  516 . Of course, this results in a lack of direct stable backup support for the catheter  400  in the ascending aorta  512  directly across from the right main coronary artery  518 , where support is needed most. 
     This “dropping” of the primary curve  408  within the ascending aorta  512  also may result in the tip  412  disengaging from the ostium  520  because the straight portion  410  cannot traverse the distance from the postero-medial wall of the Sinus of Valsalva  526  to the ostium  520 . Moving the catheter to a buttressed position effectively reduces the effective length of the tip  412  because at least a portion of the straight portion  410  of the tip  412  is forced at an angle upward through the ascending aorta  512  as the primary curve  408  “drops”. The Arani-type catheter  400  is generally designed with a tip  412  and straight portion  410  length sufficient to extend across the ascending aorta  512  (when in the fulcrum position) and to be capable of marginally coaxially intubating a horizontal take-off right coronary artery  518 . When moved to the buttressed position, this tip  412  and straight portion  410  length are no longer adequate to extend from the postero-medial wall  516  of the ascending aorta  512  to the ostium  520  and still maintain secure and coaxial intubation of the tip  412  of the catheter  400 . Consequently, if the physician chooses to maintain coaxial intubation of the tip, direct backup support will be sacrificed. Conversely, if more backup support is desired, attempts to use the buttress position will make it more likely that the tip  412  will become disengaged from the ostium  520 . Accordingly, the Arani-type catheter  400  when used in the buttressed position has several problems: a lack of direct backup support, inadequate tip length, and potential angled tip entry into the ostial wall. In addition, two other significant problems with the Arani catheter as used in the buttress position results from the very sharp acute angles that are created in the body of the catheter  400  (even sharper than the already sharp 75° or 90° primary curve and 90° secondary curve in a relaxed state). First, such acute angles greatly dissipate transmission of pushing forces for a therapeutic device extending through the catheter  400  in that position and, in the case of an acute primary curve, pushing on the catheter may cause the curve to close up or become even more acute. These factors both act to significantly limit the ability of a therapeutic device to cross a tight stenosis. Second, any rotation of the catheter  400  initiated at the proximal end gets distorted and dissipated by the sharp bends in the body of the catheter  400 . These sharp angles, the contact of the secondary curve portion with the antero-lateral wall, and the absence of other curves in the catheter make it extremely difficult to further manipulate the tip  412  into and around the ostium  520  of the right main coronary artery  518  (to the extent that inadequate tip length problems can be overcome). Moreover, when in the buttressed position with the primary curve angle more acute, even if it engaged an opposite portion of the ascending aorta, the apex of the primary curve would approximate a singular point, thus not providing sufficient area for stable contact with the wall of the aorta. Accordingly, once in the buttressed position, the operator loses almost all control over the ability to position the tip of the catheter  400  and transmission of pushing forces become greatly limited. This loss of tip control can be important for reasserting intubation when the tip is too short, which is a typical problem for the Arani catheter when used in the buttressed position. 
     However, the problem of inadequate tip length for the catheter  400  when used in the buttressed position cannot be effectively overcome by merely lengthening straight portion  410 . If this is done, then it is much more difficult to initiate intubation of the ostium  520  when initially advancing the tip  412  of the catheter  400  into the ascending aorta  512 . In this instance, the straight portion  410  generally would be longer than the width of the ascending aorta, and this geometrical relationship would make it extremely difficult to initially advance the catheter  400  so that the tip straight portion  410  becomes sufficiently horizontal to enter the right coronary ostium  520 . 
     With the catheter  400  in the preferred buttressed position (FIG.  2 C), the relatively small size of the contact portion and its location substantially above (not directly across from) the ostium  520  of the right coronary artery  518  along the antero-lateral wall  514  directly contribute to the relatively poor backup support of the Arani guide catheter  400  when advancing a therapeutic device adjacent a tight stenosis. First, because the surface area of contact between the secondary curve portion  404  and the aortic wall is so small, the guide catheter  400  is unstable and therefore easier to dislodge from its position against the aortic wall when resistive “pushback” forces are encountered during advancement of a balloon catheter across a stenosis. Moreover, the straight portion  406  of the Arani-type guide catheter  400  (distal of the secondary curve  404  and proximal of the primary curve  408 ) extends through the ascending aorta  512 , barely contacting, if at all, the postero-medial wall  516  of the ascending aorta  512 . This lack of contact allows the stenotic “pushback” forces to more easily overcome the friction of the small contact area between the Arani guide catheter and the aortic wall and dislodge the Arani guide catheter from the desired orientation in the aortic complex. 
     Another significant problem with the Arani guide catheter, or other conventional guide catheters having 90° angles and or acute angles (less than 90°) along their bodies is that it may be difficult to pass some therapeutic devices (such as, e.g., stents, laser catheters, atherectomy catheters) through such sharp angles in a guide catheter. Gradual curves are required to guide these larger devices because of their increased diameter and/or attendant bulky rigid portions. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a guiding catheter which is specifically designed to facilitate the maneuvering of a therapeutic device into a selected coronary artery, preferably the right main coronary artery. The present invention recognizes that the problem of backup support must be solved by making a fundamental change in the overall shape/configuration of guiding catheters used for right main coronary arteries. 
     The uniqueness of the guide catheter of the present invention results from having analyzed the factors that determine optimal support of a guide catheter within an aortic root complex and arranging these factors in a way to maximize backup support for distal advancement of a therapeutic device through the guide catheter of the present invention while maintaining a desired orientation of the distal end of the guide catheter in the ostium of the right main coronary artery. The factors determining the support provided by the guide catheter include the following. First, the invention can attain deep coaxial intubation of a distal tip of the guide catheter within the ostium of the right main coronary artery. Second, the catheter has a smoothness (i.e., lack of steep bends or acute angles) throughout its length when deployed in the cardiovascular system. Third, the catheter achieves a point of backup support against the wall of the ascending aorta that is as close as possible to directly across from the ostium of the right main coronary artery. Fourth, a large supportive segment of the guide catheter can rest against the wall of the ascending aorta to increase stability of the guide catheter within the aortic complex. Fifth, the catheter is capable of providing a substantially linear axis of support between the ostium of the right main coronary artery and the point of support against the wall of the ascending aorta. Sixth, the catheter is able to compensate for anatomical variations such as a Sheperds Crook take off, “anterior take-offs” (including a rotated aortic root or an offset origin of the right coronary artery), or an “exit bend” of the ascending aorta (a pronounced medial curvature of the lower region of the ascending aorta). 
     Providing a configuration for a guide catheter, such as the present invention, which focuses on combining all of these factors to provide an optimal guide catheter design results in a guide catheter that functions appreciatively better than the Judkins guide catheter, the Arani Double Loop catheter, or any of the known catheters used for angioplasty catheterization of the right main coronary artery. 
     The guide catheter of the present invention in a relaxed (preformed) state prior to insertion within the cardiovascular system has a configuration that causes the advantageous orientation of the guide catheter in the aortic complex. The inventive guide catheter includes a hollow, flexible tubular body having a proximal, generally straight portion and a distal, generally curvaceous portion with a distal end. The distal portion has a primary curve proximal the distal end, a secondary curve proximal the primary curve, and a tertiary curve proximal the secondary curve. These curves are preformed and aligned so that after the guide catheter has been advanced through the descending aorta, over the aortic arch, and into the ascending aorta to a position where the distal end is generally coaxially aligned relative to the ostium of the right main coronary artery, the distal portion of the guide catheter engages the wall of the ascending aorta and engages the wall of the aortic arch. 
     Preferably, the proximal and secondary curves are defined by preformed, consecutively arranged obtuse angled segments of the tubular body. The tertiary curve is defined by a preformed, oppositely disposed arc extent of the tubular body long enough to cause the distal portion to overlie itself in its preformed configuration prior to use. 
     The advantageous orientation of the guide catheter of the present invention (when in the aortic complex) results directly from the configuration of the guide catheter when in its relaxed (preformed) state prior to insertion in the cardiovascular system. Foremost, one embodiment of the guide catheters of the present invention has an “over-curved” tertiary curve portion including a supportive fifth curved segment positioned proximally of the secondary curve portion (and the primary curve). The tertiary curve portion forms an arc of between 260° to 330°. This tertiary curve portion causes the supportive fifth curved segment and a proximal portion of the secondary curve portion to form the contact portion (in use) that rests substantially contiguous against the wall of the ascending aorta. This arrangement causes at least a portion of a supportive fifth curved segment to press against the ascending aortic wall, thereby allowing the primary point of backup support (at a distal end of the area of support, i.e., a distal end of the contact portion) to be positioned very low in the ascending aorta. The preferred initial point of backup support for the guide catheter of the present invention is a point along the ascending aortic wall substantially directly opposite the ostium of the right main coronary artery. Moreover, because the supportive fifth curved segment of the guide catheter of the present invention presses against the ascending aortic wall, a large area of general backup support (the substantially contiguous contact portion) is provided for the guide catheter which aids in the backup process by making it quite difficult to dislodge the guide catheter from its desired orientation. 
     In addition, the presence of the tertiary curve portion (which is preferable defined by a series of relatively gradual bends) provides a single longer bent section of the guide catheter (than a Judkins-style or an Arani-style guide catheter) when disposed in the aortic complex. Each bend in the tertiary portion of the catheter has a relatively mild angle to allow a fuller transmission of distal pushing forces through the guide catheter. This arrangement thus facilitates the passage of therapeutic devices through the inventive guide catheter, especially when such devices have rigid and/or bulky portions, as the case may be for a stent or arthrectomy catheter. 
     All of these advantages of the guide catheter of the present invention are gained by an intentional design for the configuration of the guide catheter in its relaxed state. Accordingly, when the guide catheter of the present invention is fully disposed in the aortic complex, a substantially different and superior (i.e., better) orientation is achieved, compared to previous catheters. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings wherein: 
     FIGS. 1A and 1B are side and front views, respectively, of a portion of the Judkins-type catheter of the prior art; 
     FIG. 1C is a cross sectional view of a portion of a cardiovascular system with the catheter of FIGS. 1A and 1B inserted therein; 
     FIG. 1D is an enlarged cross-sectional view taken along the line  1 D— 1 D; 
     FIG. 2A is a side view of a portion of the Arani-type catheter of the prior art; 
     FIGS. 2B and 2C are cross-sectional views taken from a left anterior oblique view of a portion of a cardiovascular system with the Arani-type catheter disposed therein for intubation of the right main coronary artery; 
     FIGS. 3A-3D,  4 A- 4 D,  5 A- 5 D,  6 A- 6 D and  7 A- 7 D are views similar to FIGS. 1A-1D, respectively, but depicting alternate embodiments of the present invention; 
     FIGS. 8A and 8B are side views of a portion of the another embodiment of the catheter of the present invention; 
     FIG. 8C is a top view of a modified version of the catheter of FIGS. 8A and 8B, as viewed from the top is of FIGS. 8A and 8B; 
     FIGS. 9A,  9 B and  9 C are cross-sectional views taken from a left anterior oblique view of a portion of a cardiovascular system showing the alternative positions attainable with the inventive catheters of FIGS. 8A,  8 B and  8 C for intubation of the right main coronary artery; 
     FIG. 9D is a cross-sectional view taken from a left anterior oblique view of a portion of a cardiovascular system having a bent aortic arch and showing one of the alternative positions attainable with the inventive catheters of FIGS. 8A,  8 B and  8 C for intubation of the right main coronary artery; 
     FIG. 9E is a generated view in section taken from an anterior posterior view as taken along lines X—X in FIG. 9A; 
     FIG. 9F is a generated view in section taken from an anterior posterior view as taken along lines Y—Y in FIG. 9C; 
     FIGS. 10A and 10B are side views of a portion of the another embodiment of the catheter of the present invention; 
     FIG. 10C is a top view of a modified version of the catheter of FIGS. 10A and 10B, as viewed from the top of FIGS. 10A and 10B; 
     FIG. 11 is an end view of a modified version of the catheter of FIG. 10A, as viewed from the right side of FIGS. 10A and 10B; 
     FIG. 12A is a side view of a modified version of the distal portion of the catheter of FIG. 10A; and 
     FIG. 12B is an end view of the modifed version catheter of FIG. 12A, as seen from the right side of FIG.  12 A. 
    
    
     While the above identified drawings set forth several preferred embodiments, other embodiments of the present invention are also contemplated, as noted in the discussion. This disclosure presents illustrative embodiments of the present invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the catheter of the present invention is shown in general by the reference numeral  36  in FIGS. 3A-3D. The catheter  36  is in the form of an elongated, preformed tubular member having a straight portion  38  extending from the proximal end portion (not shown) of the catheter  36 . The catheter  36  includes a distal end portion formed by a curved portion  40 , a plurality of straight portions  42 ,  44 , and  46 , and a tip portion  48 . The curved portion  40  extends from the straight portion  38  for approximately 200-240°. The straight portion  42  extends from the curved portion  40  toward, and at an angle to, the straight portion  38 . The straight portion  44  extends from, and at an angle to, the straight portion  42 , and generally parallel to the straight portion  38 . The straight portion  46  extends from, and at an angle to, the straight portion  44  and the tip portion  48  extends from, and at an angle to, the straight portion  46  and generally perpendicular to the straight portion  38 . 
     The curved portion  40  has a radius of curvature of approximately 5 cm. and the distance D 1  between the tip portion  48  and the outer edge of the curved portion  40  is approximately 12.5 cm. The distance D 2  between the straight portions  44  and  38  is approximately 2.5 cm. The straight portion  44  is approximately 1.5 cm. in length, and the straight portions  46  and  48  are each approximately 1.2 cm. in length. The angle between the straight portions  42  and  44  is between 20° and 50°, the angle between the straight portions  44  and  46  is between 10° and 50°, and the angle between the straight portion  46  and the tip portion  48  is between 10° and 50°. It is understood that these distances and angles represent only one possible configuration of the catheter  36 . For example, the length of straight portion  44  can be increased to other values within the scope of the invention and thus provide increased support as compared to the Judkins catheter. 
     The aforementioned dimensions can vary substantially and depend extensively on the variance of human cardiovascular physiology. For example, while the curved portion  40  typically will have a radius of curvature of approximately 5 cm., the radius of curvature can vary from approximately 5 to 7 cm. Similarly, the distance D 1  can vary from approximately 6 to 16 cm., the distance D 2  can vary from approximately 0.0 to 6 cm., and the straight portions  46  and  48  can vary from 0.5 to 2 cm. in length. 
     Referring to FIG. 3B, it is noted that the straight portion  38  extends in the same plane as the above described distal end portion. 
     The catheter  36  can be fabricated of a material, such as plastic, which exhibits optimum flexibility and softness while permitting the transmission of twisting forces along its length by manipulation of its proximal end. The material is tubular, i.e. it has a continuous bore extending through its entire length for receiving other catheters, wires or the like as discussed above. Since this material is conventional it will not be described in any further detail. 
     FIGS. 3C and 3D depict the cardiovascular system  22  of FIG. 1C with the catheter  36  inserted therein. Prior to insertion, a relatively stiff wire (not shown) is inserted in the catheter  36 . After the catheter  36  is inserted in the system  22 , the wire is withdrawn and the catheter  36 , by virtue of its preformed shape previously described and shown in FIGS. 3A and 3B, takes the position shown in FIGS. 3C and 3D, or with slight manipulation, with the tip portion  48  precisely aligned with the ostium  26  of the right coronary artery  28  in a coaxial relationship. It is also noted that, as a result of the foregoing, a substantial portion of the catheter  36  will usually rest against the inner wall of the aorta  24 , including the descending aorta  24   a , the aortic arch  24   c  and the ascending aorta  24   b , and bends at a lesser angle compared to the Judkins catheter  10 . Also, the straight portion  44  rests against the wall of the ascending aorta  24   b  opposite the ostium  26  of the right coronary artery  28 . Thus, the catheter  36  is supported by the wall when axial forces are exerted on the tip portion  48  and the tip portion  48  remains fixed in the lumen of the right coronary artery  28 . 
     Referring to FIGS. 4A-4D, there is shown an alternate embodiment of the catheter of the present invention. The catheter depicted is shown in general by the reference numeral  50  and is for a special application referred to as  1 , anterior take-off  11  of the right coronary artery as will be described. 
     The catheter  50  is in the form of an elongated, preshaped tubular member having a straight portion  52  extending from the proximal end portion (not shown) of the catheter  50 . The catheter  50  further includes a distal end portion formed by a curved portion  54 , a plurality of straight portions  56 ,  58 , and  60 , and a tip portion  62 . The curved portion  54  extends from the straight portion  52  for approximately 200-240°. The straight portion  56  extends from the curved portion  54  toward, and at an angle to, the straight portion  52 . The straight portion  58  extends from, and at an angle to, the straight portion  56 , and generally parallel to the straight portion  52 . The straight portion  60  extends from, and at an angle to, the straight portion  58 , and the tip portion  62  extends from, and at an angle to, the straight portion  60  generally perpendicular to the straight portion  52 . 
     According to a feature of this embodiment, the straight portion  56 , and therefore the portions  58 ,  60  and  62  extending therefrom, are bent out of the plane formed by the straight portion  52  and the curved portion  54  as shown in FIG.  4 B. As a result, the straight portion  56  extends at an angle A 1  of between 8° to 40° to the straight portion  52 . Consequently, the tip portion  62  is displaced from the corresponding portion of the straight portion  52  by approximately 2 cm. 
     The catheter  50  has a special application in a coronary condition referred to as “anterior take-off” (as seen in RAO view) of the right coronary artery in which the right coronary artery  28  of the cardiovascular system  22  is angularly displaced anteriorly from its normal location, as shown in FIG.  4 D. More particularly, the normal position of the right coronary artery is shown by the dashed lines and by the reference numeral  28 . However, the right coronary artery sometimes is angularly displaced anteriorly from its normal position to a position shown, for example, by the solid lines and by the reference numeral  28 ′. Anterior displacements of the right coronary artery  28  may be due to either a displacement in the aortic root or a displacement in the right coronary artery. Both of these variations result in an anterior take-off of the right coronary artery. The catheter  50  is especially configured for this location and, when inserted into the cardiovascular system  22  in the manner described above, takes the position shown in FIG. 4C with the tip portion  62  coaxially aligned with the ostium  26 ′ of the right coronary artery  28 ′. Thus the catheter  50  enjoys the advantages of the catheter  36  of the embodiment of FIGS. 3A-3D notwithstanding the anterior displacement of the artery. 
     Referring to FIGS. 5A-5D, there is shown another alternate embodiment of the catheter of the present invention. The catheter depicted is shown in general by the reference numeral  64  and is again for the special application referred to as anterior take-off of the right coronary artery as previously described. 
     The catheter  64  is in the form of an elongated, preshaped tubular member having a straight portion  66  extending from the proximal end portion (not shown) of the catheter  64 . The catheter  64  further includes a distal end portion formed by a curved portion  68 , a plurality of straight portions  70 ,  72 , and  74 , and a tip portion  76 . The curved portion  68  extends from the straight portion  66  for approximately 200-240°. The straight portion  70  extends from the curved portion  68  toward, and at an angle to, the straight portion  66 . The straight portion  72  extends from, and at an angle to, the straight portion  70  generally, parallel to the straight portion  66 . Similarly, the straight portion  74  extends from, and at an angle to, the straight portion  72 , and the tip portion  76  extends from, and at an angle to, the straight portion  74  generally perpendicular to the straight portion  66 . 
     As better shown in FIG. 5B, the straight portion  72  is bent out of the plane formed by the straight portion  70 , the curved portion  68  and the straight portion  66 , and extends at an angle A 2  of approximately 40° to the straight portion  70 . Further, the straight portion  74  is bent back toward the aforementioned plane and extends at an angle A 3  of approximately 40° to the straight portion  72 . Also, the straight portion  76  is bent back toward the aforementioned plane and extends at an angle A 4  (FIG. 5D) of approximately 160° to the straight portion  74 . 
     The catheter  64  has a special application in connection with the anterior take-off of the right coronary artery, as previously described. The catheter  64  is especially configured for this condition and, when inserted into the cardiovascular system  22  in the manner described above, it takes the position shown in FIG. 5C with the tip portion  76  coaxially aligned with the ostium  26 ′ of the right coronary artery  28 ′. Thus the catheter  64  enjoys the advantages of the catheter  36  of the embodiment of FIGS. 3A-3D notwithstanding the anterior displacement of the right coronary artery. 
     Referring to FIGS. 6A-6D, there is shown another alternate embodiment of the catheter of the present invention. The catheter depicted is shown in general by the reference numeral  78  and is also for anterior take-off of the right coronary artery as previously described. 
     The catheter  78  is in the form of an elongated, preformed tubular member having a straight portion  80  extending from the proximal end portion (not shown) of the catheter  78 . The catheter  78  further includes a distal end portion formed by a curved portion  82 , a plurality of straight portions  84 ,  86 , and  88 , and a tip portion  90 . The curved portion  82  extends from the straight portion  80  for approximately 200-240°, and the straight portion  84  extends from the curved portion  82  toward, and at an angle to, the straight portion  80 . The straight portion  86  extends from, and at an angle to, the straight portion  84  generally parallel to the straight portion  80 . Similarly, the straight portion  88  extends from, and at an angle to, the straight portion  86 , and the tip portion  90  extends from, and at an angle to, the straight portion  88 . 
     The embodiment of FIGS. 6A-6D enjoys the same planar relationships, as the embodiment of FIGS. 3A-3D with two additional features. As better shown in FIG. 6B, the straight portion  84  is bent out of the plane formed by the straight portion  80  and the curved portion  82  and extends at an angle A 4  of approximately 10-30° to the straight portion  80 . Also, the straight portion  86  is bent at an angle A 5  of approximately 0-30° to the straight portion  84  in the opposite direction of A 4 , i.e. back towards the straight portion  80 . In a preferred embodiment, the angle A 4  is 20° and the angle A 5  is 30°. 
     The catheter  78  has a special application in connection with the anterior take-off of the right coronary artery, as previously described. When inserted into the cardiovascular system  22  in the manner described above, the catheter  78  takes the positions shown in FIGS. 6C-6D with the tip portion  90  coaxially aligned with the ostium  26 ′ of the right coronary artery  28 ′. Thus the catheter  78  enjoys the advantages of the catheter  36  of the embodiment of FIGS. 3A-3D notwithstanding the anterior displacement of the artery. 
     Referring to FIGS. 7A-7D, there is shown still another alternate embodiment of the catheter of the present invention which is referred to in general by the reference numeral  92 . This alternate embodiment can be designed for use either with a standard anatomy or when there is an anterior take-off of the right coronary artery, as previously described. 
     The catheter  92  is in the form of an elongated, preformed tubular member having a straight portion  94  extending from the proximal end portion (not shown) of the catheter  92 . The catheter  92  further includes a distal end portion formed by a curved portion  96 , a plurality of straight portions  98 ,  100 , and  102 , and a tip portion  104 . The curved portion  96  is “overcurved” in this embodiment for reasons described below such that it extends from the straight portion  94  for approximately 260-320°. The straight portions  98 ,  100 , and  102 , and the tip portion  104  are shaped as their counterparts in the previous embodiment shown in FIGS. 4A-4D. In FIG. 7B, these portions are shown as being out of the plane formed by the straight portion  94  and the curved portion  96 , however, they are not preformed to be out of the aforementioned plane, but are necessarily so due to the extended curvature of the curved portion  96 . 
     The curved portion  96  of the catheter  92  is “overcurved” to alleviate two common problems. First, the extended curvature is necessary to compensate for the extra flexibility imparted to catheters as they warm to body temperature. If the curved portion  96  was not “overcurved,” then as the catheter  92  warmed and became more flexible, the curved portion  96  would open and enlarge to an angle greater then the angle of the aortic arch  24   c . Second, the extended curvature is necessary for support when the aortic arch  24   c , which normally curves over 180°, is curved to a greater extent. In both cases, the result is a catheter  92  which no longer rests against the inner wall of the aorta  24 , thereby forfeiting the support afforded when the straight portion  100  rests against the ascending aorta  24   b  wall opposite the ostium  26  of the right coronary artery  28 . By “over curving” the curved portion  96 , the catheter  92  will rest against the inner wall of the aorta  24  (see FIG. 7C) and provide the needed support. 
     While the embodiment shown in FIGS. 7A-7D is for standard anatomy, it is also applicable for those earlier embodiments described for use when the right coronary artery has an anterior take-off in that various portions of the catheter  92  can be bent out of the plane formed by the straight portion  94  and the curved portion  96  to allow the tip portion  104  to align with the lumen of a right coronary artery having an anterior take-off. 
     Additional embodiments of the guide catheters of the present invention for catheterization of a right main coronary artery provide further illustration of the features of embodiments of the present invention described above. These additional embodiments of the present invention include substantially the same strategically ordered sequence (particularly with respect to the embodiments of FIGS. 7A-7D) of straight portions, curve portions, and tertiary curve portions resulting in more precise coaxial alignment of the guide catheter within the ostium of the right main coronary artery, increased support and guidance for therapeutic devices, and a fuller transmission of pushing forces. The previously described guide catheter embodiment of the present invention for catheterization of a right main coronary artery, e.g., the guide catheter embodiment of FIG. 7A, and these additional embodiments, include a unique overcurved tertiary portion created between an otherwise conventional first straight portion and a secondary curve portion of the guide catheter of the present invention. In the previously described embodiment (e.g., the FIG. 7A embodiment), a straight portion  98  was included between the tertiary curve portion (curve portion  96 ) and the secondary curve portion (the junction of straight portion  98  and straight portion  100 ). These additional embodiments include a tertiary curve portion (in FIG. 7A, the curved portion  96 ) but preferably do not include a straight portion like that of straight portion  98  in embodiment  7 A. These additional embodiments also include a mild obtuse angle primary curve portion like that shown in the FIG. 7A embodiment (the junction of the portion  104  and portion  102 ). These additional embodiments provide further examples illustrating the strategic sequencing of straight, curved, and tertiary portions that yield the many advantages of the guide catheters of the present invention, particularly those used for catheterization of a right main coronary artery. 
     A guide catheter  110 , another preferred embodiment of the present invention, is illustrated in FIGS. 8A-8C. The guide catheter  110  is adapted for use with a right main coronary artery to facilitate advancement of a dilatation balloon catheter (or other intravascular devices) through the guide catheter  110 . The preformed guide catheter  110  is shown in FIG. 8A in a relaxed or “equilibrium” state prior to insertion into the cardiovascular system and includes a hollow elongate flexible tubular body or shaft  112  which extends from a proximal generally straight portion  114  to a distal generally curvaceous portion  116 . The guide catheter  110  includes a first straight proximal portion  118  that extends from a proximal end  120  of the guide catheter  110  to a point  122  (a distal end of the first straight portion  118 ) located distally along the catheter shaft  112  from the proximal end  120 . A fitting or manifold (not shown) is typically mounted on the proximal end of a guide catheter. 
     The first straight portion  118  preferably has a length of about 90 to 95 centimeters but can be made shorter or longer to accommodate different patient anatomies. The distal portion  116  of the guide catheter  110  includes consecutively arranged portions including a tertiary curved portion  123 , a secondary curved portion  146 , and a distal tip portion further including a second straight portion  138 , a primary curved portion  140 , and a straight tip portion  142 . The tertiary curve portion  123  forms an arc that curves oppositely from the obtuse angles created by the primary and secondary curve portions,  140  and  146 , respectively, and is long enough to cause the distal portion  116  of the guide catheter  110  to overlie itself in its relaxed, preformed configuration prior to use. 
     The tertiary curve portion  123  of the guide catheter  110  is defined by the curvature in the guide catheter  110  between the point  122  and a point  144  (a distal end of the tertiary portion  123 ) located distally along the catheter shaft  112 . As seen in FIG. 8B, the secondary curve portion  146  extends distally from the distal end of the tertiary curve portion  123 , from the point  144  to a point  137 . The second straight portion  138  extends distally from a distal end of the second curved portion  146 , from the point  137  to a point  139 . The primary curve portion  140  extends distally from the distal end of the second straight portion  138 , from the point  139  to a point  141 . The straight tip portion  142  extends distally from the primary curved portion  140 , from the point  141  to a point  143  (which defines a terminal distal end of the guide catheter  110 ). 
     The tertiary portion  123  of the guide catheter  110  is a curvaceous segment forming an arc from between 260 and 330° and is comprised of the preferred combination of five discrete portions: a first curved segment  124 , a second curved segment  126 , a third curved segment  128 , a fourth curved segment  130 , and a fifth curved segment  132 . As shown in FIGS. 8A-8B, the tertiary portion  123  forms an arc of about 330°. 
     The first curved segment  124  of the tertiary curve portion  123  extends distally from the point  122  to a point  125  along the catheter shaft  112 . The arc of the first curved segment  124  is about 27°, has radius of curvature of about 3.5 centimeters, and is about 1.65 centimeters long. The second curve segment  126  of the tertiary curve portion  123  of the guide catheter  110  is defined by the curvaceous segment of the catheter shaft  112  extending distally from the point  125  to a point  127  along the catheter shaft  112 . The second curved segment  126  forms an arc of about 55°, has a radius of curvature of about 5.5 centimeters, and is about 5.3 centimeters long. The third curved segment  128  of the tertiary curved portion  123  extends distally from the point  127  to a point  129  along the catheter shaft  112 . The third curved segment  128  forms an arc of about 153°, has a radius of curvature of about 3.0 centimeters, and is about 8.0 centimeters long. The fourth curved segment  130  of the tertiary curved portion  123  extends distally from the point  129  to a point  131  along the catheter shaft  112 . The fourth curved segment forms an arc of about 69°, has a radius of curvature of about 2.8 centimeters, and is about 3.4 centimeters long. The fifth curved segment  132  of the tertiary curved portion  123  extends distally from the point  131  to the point  144  along the catheter shaft  112 . The fifth curved segment  132  forms an arc of about 25°, has a radius of curvature of about 6.0 centimeters, and is about 2.6 centimeters long. 
     The secondary curved portion  146  is preferably comprised of two discrete curved segments: a first curved segment  134  and a second curved segment  136 . The first curved segment  134  forms an arc of about 20°, has a radius of curvature of about 2.0 centimeters, and is about 0.70 centimeters long. The second distal curved segment  136  forms an arc of about 50°, has a radius of about 1.5 centimeters, and is about 1.3 centimeters long. 
     The second straight portion  138  of the guide catheter extends about 0.30 centimeters from the distal end of the secondary curved portion  146  from the point  137  to a point  139  along the catheter shaft  112 . The primary curved portion  140  extends from the second straight portion  138  from the point  139  to a point  141 . The primary curved portion  140  forms an arc of about 25°, has a radius of about 2.0 centimeters, and is about 0.85 centimeters long. The straight tip portion  142  extends distally from the primary curve portion  140  for about 0.95 centimeters. The primary curve portion  140  forms an obtuse angle of approximately 25° between the second straight portion  146  and the straight tip portion  142 . 
     The distance D 1  (see FIG. 8B) from the point at which the distal portion  116  overlaps itself to a point  147  diametrically opposite therefrom along the tertiary curve portion  123  is about 7.45 centimeters. The distance D 2  in FIG. 8B is about 6.0 centimeters. The distance from point  147  to the secondary curve portion  146  is about 8.0 to 9.0 centimeters when the guide catheter  110  is fully disposed in the right coronary artery  518  (as in FIG.  9 A). The catheter length from the distal end  143  and an apex of the primary curve portion  140  is about 1.4 centimeters. The catheter length from the apex of the primary curve portion  140  and an apex of the second curved portion  136  is about 1.4 centimeters. The catheter length from the apex of the second curved segment  136  and an apex of the first curved segment  134  is about 1.0 centimeters. 
     Although the guide catheter  110  can be a single piece of tubing with a uniform degree of flexibility throughout its length, the guide catheter  110  preferably is made of two or three principal tubular segments with each successively distal segment having a greater degree of flexibility. As seen in FIG. 8A, the embodiment of the guide catheter  110  having three principal flexibility segments includes a first flexibility tubular segment  150  extending from the proximal end  120  of guide catheter  110  to a bond member  152  located just distal of the primary curve portion  140  (in the distal portion  116  of the guide catheter  110 ). A second flexibility tubular segment  154  extends distally from the bond member  152  to a third flexibility tubular tip segment  156 . In an alternate embodiment, the bond ring member  152  is located proximal of the primary curve portion  140  of the guide catheter  110 . Accordingly, the least flexible segment, segment  150 , would extend just proximal of the primary curve portion  140  of the guide catheter  110 . 
     The nature of the three principal segments and their different flexibility are described in co-pending application Ser. No. 07/908,250 INTRAVASCULAR GUIDE CATHETER, which is incorporated by reference herein. In one embodiment, the first segment  150 , the second segment  154 , and the third segment  156  have a Shore D durometer hardness of about, 63, 40, and 35 respectively. The bond member  152  has a Shore D durometer hardness of about 50, intermediate the hardness of the first segment  150  and the second segment  154 . 
     A double flexibility segment embodiment (not shown) of the guide catheter  100  has two principal segments of flexibility, each with a different degree of flexibility. The double flexibility embodiment has a tip segment (like tip segment  156 ) with a select degree of flexibility and a main segment (all portions proximal to the tip segment) with a different select degree of flexibility (less flexible than the tip segment). The double flexibility segment embodiment differs from the triple flexibility segment embodiment in that the second flexibility segment  154 , having a hardness intermediate that of the first (i.e., main) flexibility segment  150  and the tip segment  156 , is absent in the double flexibility segment embodiment. Although it is preferred to have a bond ring member (like member  152 ) positioned between the main and tip flexibility segments, the double flexibility segment may omit a bond ring member between the main segment and the tip segments In one embodiment, the main segment of the double flexibility segment embodiment of the guide catheter  110  has a Shore D hardness of 63 (or 67, 70) and the tip segment has a Shore D hardness of 35. The optional bond ring member would have a Shore D hardness (e.g., about 46) intermediate that of the first segment and tip segment. The optional bond ring member would preferably be positioned distal of the primary curve portion  140  of the guide catheter  110 . 
     The catheter shaft  112  of both the double flexibility segment embodiment and the triple flexibility segment embodiment is made of an outer layer and an inner layer. The outer laser is preferably formed of a polyether block amide material, such as PEBAX® available from ATOCHEM, INC. (Glen Rock, N.J.), loaded with a radiopaque compound such as bismuth subcarbonate. The inner layer is a coating of lubricous material such as TEFLON® available from E.I. Du Pont Nemours &amp; Co. (Wilmington, Del.). The first principal segment  150  and the second (intermediate) segment  154  (in the triple flexibility embodiment) preferably have a reinforcing layer of wire braiding (of stainless steel wire) extending along the catheter shaft  112  between the inner layer and the outer layer. The tubular tip segment  156  is formed from PEBAX® material, loaded with a radiopaque compound such as bismuth subcarbonate. 
     The configuration of the guide catheter  110  is created by fitting the tubing comprising the catheter (without curves) into a mold having the desired curves and straight segments. The catheter tubing is then heat set into that shape by infrared heating and then cooled as is known in the art. This molding technique produces the configuration of the guide catheter  110  as shown in FIGS. 8A-8C, FIGS. 10A-10C, FIGS. 11 and 12, as well as any one of the catheters of the present invention described herein. 
     The guide catheter  110 , in one embodiment overlies itself as generally depicted by FIG.  8 B. FIG. 8C also shows an alternate embodiment of the inventive guide catheter in which a portion of the guide catheter  110 A extends in multiple planes to yield a three dimensional type distal portion  116  of a guide catheter  110 A. The segments of the guide catheter  110 A have the same lengths and curvatures as the guide catheter  110  shown in the view FIG.  8 B. However, as seen in this top view of the guide catheter  110 A in FIG. 8C, the guide catheter  110 A has curves planes in several planes. The guide catheter  110 A of FIG. 8C has a proximal first segment  170 , a straight second segment  172 , a curved third segment  174 , a straight fourth segment  176 , a curved fifth segment  178 , and a sixth distal straight segment  180 . 
     The angle (α 1 ) between the first segment  170  and the second segment  174  is about 22 degrees and the length of the second segment  172  is about 5.35 centimeters. The third segment  174  has a radius of curvature of about 10 centimeters and forms an arc of about 5 degrees. In an alternate embodiment, the third segment  174  can be straight and extend about 1.0 centimeters. The fourth segment  176  has a slightly curved proximal portion extending from the third segment  174  and then has a straight portion extending distally for about 3.0 centimeters. The angle between the plane traversed by the third segment  174  and the plane traversed by the straight portion of the fourth segment  176  is about 60°. As seen from the top view of FIG. 8C, the straight portion of fourth segment  176  forms an obtuse angle (α 2 ) of about 130 degrees relative to the first segment  170  over which the fourth segment  176  crosses. The distance between the crossover of the fourth segment  176  and the junction of the first segment  170  and the second segment  172  is about 4.5 centimeters. The fifth segment  178  has a radius of curvature of about 1.5 centimeters and forms an arc of about 60 degrees. The sixth segment  180  extends from segment  178  and has a length of about 1.0 centimeter. The distance D 3  between the crossover of the fourth segment  176  and the first segment  170  to the tip of segment  180  is about 3.0 centimeters. The distance D 4  between the apex of the third segment  174  and the first segment  170  is about 2.0 centimeters. 
     In use, as shown in FIG. 9A, the guide catheter  110  is inserted through the cardiovascular system so that its distal end portion  116  is disposed within the aortic complex including the ascending aorta  512 , aortic arch  504 , and the descending aorta  502 . FIGS. 9A-9D are sectional views of the cardiovascular system  500  as seen from a left anterior oblique (LAO) viewpoint as seen by a physician via fluoroscopy. The guide catheter  110  is typically inserted into the cardiovascular system  500  at a femoral artery (not shown) with a stiffening wire (not shown) extending through the entire length of the lumen of the guide catheter  110 . The stiffening wire is of sufficient rigidity to temporarily overcome the curve portions of the guide catheter  110  so that the guide catheter  110  takes on the shape of the stiffening wire as the stiffening wire passes through the cardiovascular system  500 . The guide catheter  110  (with the stiffening wire therein) is advanced distally through the cardiovascular system until the straight tip portion  142  of the guide catheter  110  is beyond the great head and neck arteries  506 . The guide catheter  110  (with the stiffening wire extending therethrough) forms a relatively smooth curve to extend about the arch of the aorta  504  and down through the ascending aorta  512 . Once the straight tip portion  142  of the guide catheter  110  is in position adjacent the right main coronary artery  518 , the stiffening wire is removed from within the guide catheter  110  allowing the guide catheter  110  to attempt to resume its relaxed state (preformed) configuration (the relaxed state shape prior to insertion in the cardiovascular system, as shown in FIGS.  8 A- 8 C). 
     The guide catheter  110  is advanced distally and further maneuvered until in the orientation shown in FIG.  9 A. This orientation (FIG. 9A) corresponds to the proper and preferred positioning of the guide catheter  110  within the cardiovascular system  500  so that the guide catheter  110  can facilitate the advancement and support of a balloon dilatation catheter  160  through the guide catheter  110 . As seen in FIG. 9A, the distal portion  116  of the guide catheter  110  is positioned within the aortic complex such that the tertiary curved portion  123  wraps around the arch of aorta  504 , hugs against the postero-medial wall  516  of the ascending aorta  512 , as well as against a wall of the descending aorta  502 . The last (fifth) curved segment  132  (which can be a straight member in an alternate embodiment) of the tertiary curved portion  123  of the guide catheter  110  extends distally from the rest of the tertiary curve portion  123  to press against and be substantially contiguous with the postero-medial wall of the ascending aorta  158  thereby acting as a supportive segment for the guide catheter  110 . 
     As seen in FIG. 9A, a proximal portion of the secondary curved portion  146  extends distally from the last curved segment  132  of the tertiary curved portion  123 . Accordingly, the tertiary curve portion  123  and the proximal portion of the secondary curved portion  146  together define a contact portion of the guide catheter  110  for pressing against and substantially contiguous with the postero-medial wall  516  of the ascending aorta  158 . From its distal end, the contact portion extends along the ascending aortic postero-medial wall  516  generally above the ostium  524  of the left main coronary artery. A remaining distal portion of the secondary curved portion  146  (beginning with approximately the apex of its pre-insertion, i.e., relaxed state, curvature) extends laterally away from the postero-medial wall  516  of the ascending aorta  512  so that the second straight portion  138  and the straight tip portion  142  together extend laterally across the ascending aorta  512 . As seen in FIG. 9A, the straight portion  138  of the guide catheter  110  extends slightly downward as it extends across the ascending aorta  512  from the distal portion of the secondary curve portion  146  near a distal end  517  of the postero-medial wall  516  of the ascending aorta  512 . This arrangement causes the distal straight tip portion  142  to be precisely coaxially intubated within the ostium  520  of the right main coronary artery  518  and, at the same time, maintains contact between the heel of the guide catheter  110  and the postero-medial wall  516  to provide superior backup support. 
     The primary curved portion  140  of the guide catheter  110  is shown in FIG. 9A, resting in its natural relaxed state orientation of about 155°, which causes the straight tip portion  142  of the distal end portion of the guide catheter  110  to extend substantially horizontally (for a lateral take-off) through the ascending aorta  512  until the distal end of the distal straight tip portion  142  intubates coaxially within the ostium  520 . The straight portion  138  and the distal straight tip portion  142  (when properly positioned within the aortic complex as shown in FIG. 9A) together define an axis of support extending across the ascending aorta  512  from the distal end  517  along the postero-medial wall  516  of the ascending aorta  512  generally opposite the ostium to the ostium  520 . 
     This advantageous orientation of the guide catheter  110  in the cardiovascular system  500  as just described and shown in FIG. 9A is in stark contrast to the disposition of the Arani-style catheter  400  in the cardiovascular system as shown in FIGS. 2A-2C. The Arani catheter  400  when disposed in the fulcrum position can coaxially intubate the ostium  520  but usually does so at the expense of the heel of the catheter losing substantial contact with and therefore backup support from the postero-medial wall  516  as seen in FIG.  2 B. Achieving secure intubation of the Arani catheter  400  typically results in the heel of the catheter  400  hanging unsupported in the ascending aorta  512  as seen in FIG.  2 B. However, the guide catheter  110  of the present invention as seen in FIG. 9A, establishes coaxial intubation of the tip  142  within the ostium  520  but, unlike the Arani catheter, still maintains substantial positive engagement of the heel of the guide catheter  110  with the postero-medial wall  516  for stable backup support. It is the presence of the mild primary curve portion  140  of the guide catheter  110  disposed midway between the distal end  142  and the apex of the secondary curved segment of the secondary curve portion that insures positive engagement of the heel of the guide catheter  110  with the postero-medial wall  516  and coaxial intubation of the tip  142  within the ostium  520 . 
     One primary feature of the superior (i.e., better) orientation of the guide catheters of the present invention over the prior art catheters is that, when disposed in the aortic complex, a contact portion of the guide catheter  110  is established in a substantially contiguous manner against the aortic wall through the ascending aorta  512 , aortic arch  504 , and descending aorta  502 . This extensive contact between the guide catheter  110  and the inner wall of the portions of the aorta,  502 ,  504 , and  512 , respectively, primarily results from the overcurve of the tertiary curve portion  123  pressing against these portions of the aortic anatomy as the tertiary curve portion  123  tries to reassert its natural preinsertion configuration (which has a greater curvature than the curvature of the aortic arch). 
     Moreover, a distal end of this contact portion is pressed against the postero-medial aortic wall  516  slightly above the ostium  524  of the left main coronary artery  522  at point  517 . This positive engagement of the catheter  110  against the wall  516  ensures a primary area of backup support for the guide catheter  110  that is stable and that substantially directly opposes stenotic pushback forces directed outwardly from the ostium  520  of the right main coronary artery  518 . 
     In addition, a distal tip portion of the guide catheters of the present invention (including the second and tip straight portions  138  and  142 ) when disposed in the aortic complex provide a general axis of support that extends substantially across the ascending aorta  512  from the distal end  517  of the postero-medial wall  516  to the ostium  520  of the right main coronary artery  518 . This axis of support generally opposes the axis of the stenotic pushback forces, thereby substantially diminishing the potential for prolapse of the distal tip portion of the guide catheters of the present invention. Furthermore, the distal tip of the guide catheter is aligned essentially coaxially with the ostium  520  of the right main coronary artery  518 . 
     The catheter of the present invention also has the advantage of deep intubation with precise coaxial alignment in the ostium  520  of the right main coronary artery  518 . This is significant because the right main coronary artery  518  is frequently smaller than the left main coronary artery  522 . Accordingly, a catheter must be precisely configured to permit both deep intubation and coaxial alignment. The guide catheter  110  of the present invention can be advanced from its most conventional use position (FIG. 9A) to the position shown in FIG. 9B where the tip  142  has been advanced further into the ostium  520 . This is accomplished by distally advancing the guide catheter  110 , thereby causing the secondary curve portion  146  to drop lower in the ascending aorta  512  and the primary curve portion  140  to tend to straighten (although usually not completely) as the tip  142  becomes further intubated in the ostium  520  (this is further accentuated when the guide catheter  110  includes the intermediate flexibility portion  154 ). This means that the tip has effectively lengthened so that even after deeper intubation, the guide catheter  110  can still bridge the distance from the ostium  520  to the postero-medial wall  516  of the ascending aorta  512 . The effective tip length now includes both the straight tip portion  142 , primary curve portion  140  and straight tip portion  138 , as well as a distal portion of the secondary curve portion  146 . 
     As shown in FIG. 9B, this maneuver can be achieved without the secondary curve portion  146  of the guide catheter  110  dropping below the level of the ostium  524  of the left main coronary artery  522 . In particular, the apex of the secondary curve portion  146  remains substantially directly across from the ostium  520  of the right main coronary artery  518  while the proximal portion of the secondary curve portion  146  extends upward along and contacts the postero-medial wall  516  of the ascending aorta. The supportive fifth curved segment  132  of the tertiary curve portion  123  continues to press against the postero-medial wall  516  of the aorta  512  (because of the overcurve of the tertiary curve portion  123  attempting to reassert its preinsertion orientation) to anchor the catheter  110  across from the ostium  520  for providing direct and stable backup support. The remainder of the tertiary curve portion  123  “hugs” and wraps around the aortic arch  504  to prevent slippage of the catheter and maintain stability of the backup support provided along the postero-medial wall  516  of the ascending aorta  512 . 
     The adaptation of the catheter of the present invention to allow for deeper intubation without losing support from the postero-medial wall  516  of the ascending aorta  512  is unique. This is just one aspect of the catheter of the present invention that makes this catheter convertible for many uses in catheterizing the right main coronary artery. 
     In addition, the presence of the tertiary curve portion provides a gradual bend in the guide catheter (as opposed to the relatively severe bends in an Arani-style guide catheter) when disposed in the aortic complex, thereby allowing a fuller transmission of distal pushing forces through the guide catheter  110 . Moreover, the mild obtuse angle (about 160°) of the primary curve portion  140  of the guide catheter  110  and the long distal straight portion  142  cause the distal tip portion  142  to align substantially coaxially within the ostium  520  of the right main coronary artery  518 . 
     The distal straight portion  142  also maintains the primary curve portion  140  within the ascending aorta  512  outside of the ostium  520  of the right main coronary artery  518  to provide backup support. 
     The tertiary curve  123  of the guide catheter  110  has a curvature greater than the curvature of the aortic arch  502 . Thus, when the guide catheter  110  is maneuvered into the aortic complex with the tip  142  intubated in the ostium  520 , the tertiary curve portion  123  attempts to reassert its original configuration but is prevented from doing so by the inner postero-medial wall  516  of the ascending aorta  512  and the floor  510  of the aortic arch  504 , which in combination, have a lesser degree of curvature than the tertiary curve portion  123 . Accordingly, the distal portion of the tertiary curve portion  123  pushes inward against the postero-medial wall  516  of the ascending aorta  512 . This tension in the guide catheter  110  increases the stability of guide catheter  110  and accentuates backup support because the secondary curve portion  146  of the guide catheter  110  is urged against the postero-medial wall  516  of the ascending aorta  512  just above the ostium  524  of the left main coronary artery  522 . This effectively anchors the distal portion  116  of the guide catheter  110  across from the right coronary ostium  520  and substantially diminishes slippage of the guide catheter  110  along the wall of the ascending aorta when resisting stenotic pushback forces. 
     The primary curve portion  140  of the guide catheter  110  also greatly facilitates easy and accurate intubation of the tip portion  142  within the ostium  520  when initially advancing the guide catheter  110  into the ascending aorta  512 . The primary curve portion  140  (as opposed to a quite long straight portion) facilitates directing the tip  142  to the ostium  520  while only requiring minimal rotation and/or up and downward movement of the tip  412  to coaxially intubate the ostium  520 . 
     Moreover, the interaction of the particular configuration of the preformed curves in the distal portion  116  of the guide catheter  110  places the distal portion  116  of the guide catheter  110  in automatic engagement with the postero-medial wall  516  of the ascending aorta and the wall of the aortic arch  502 . The guide catheters of the prior art (i.e., Arani) require some (pulling) of the guide catheter to achieve substantial contact with the postero-medial wall  516  of the ascending aorta  512  and wall  510  of aortic arch  504 . Moreover, despite this contact, extra backup support is not obtained because the heel of the Arani catheter  400  does not maintain contact with the postero-medial wall  516  as the tip of the Arani catheter  400  is substantially intubated in the ostium  520  in the fulcrum position as shown in FIG.  2 B. 
     The inventive guide catheter  110  can be advanced to yet another operative orientation from that shown in FIGS. 9A and 9B in order to accentuate backup support for a balloon catheter being advanced distally through the guide catheter  110 . As seen in FIG. 9C, the guide catheter  110 , while the tip  142  remains deeply intubated within ostium  520  and the fifth supportive segment  132  of tertiary curve portion  123  continues to press against the postero-medial wall  516  of the ascending aorta  512 , the remaining proximal portions of the guide catheter  110  are manipulated to alter the orientation of guide catheter  110  to provide further backup support when advancing a balloon catheter through the guide catheter  110  across a tight stenosis. It should be noted that the orientation of the guide catheter  110  shown in FIGS. 9A-9B provides more than adequate backup support for advancing a balloon catheter through the guide catheter  110  in about eighty percent of all angioplasty cases. The orientation shown in FIG. 9C is for more extreme cases, about ten percent, that require even greater backup support than already attainable with the inventive guide catheter  110 . 
     The orientation of FIG. 9C is achieved by further distally advancing shaft  112  of the guide catheter  110  such that the portions of the guide catheter  110  proximal of the supportive segment  132  are lifted away from the postero-medial wall  516  of the ascending aorta  512  and the floor  510  of the aortic arch  504  and pushed upwardly to contact and rest against the roof  508  of the aortic arch  504  in a substantially contiguous fashion. In this orientation, the contact between the portions of the tertiary curve portion  123  against the roof  508  of the aortic arch  504  assist in further maintaining the position of the supportive segment  132  of the tertiary curve portion  123  against the ascending aortic postero-medial wall  516  and the apex of the secondary curve portion  146  adjacent the distal end  517  of the postero-medial wall  516 . This maintains the primary area of support for the guide catheter  110  generally opposite the right coronary ostium  520  as was true for the orientations of the catheter shown in FIGS. 9A-9B. 
     In the advantageous orientation shown in FIG. 9C of the guide catheter  110  of the present invention, the primary curve portion  146  of the guide catheter  110  retains its smooth gradual curvature from the postero-medial wall  516  across the ascending aorta to direct the tip portion  142  to be coaxially intubated within ostium  520 . Moreover, the guide catheter  110 , as shown in the operative orientation of FIG. 9C, has no sharp bends which cause the several undesirable results seen in previous catheters such as the Arani-style guide catheters. In particular, the lack of sharp bends greatly accentuates transmission of pushing forces of a therapeutic device through the guide catheter  110  in the orientation of FIG.  9 C and helps avoid kinking of the shaft of the device through any such sharp bends. In addition, the lack of sharp bends in the guide catheter  110  greatly facilitates any further distal tip manipulations that might be required for adjusting the position of the guide catheter  110  to create any particular desired effect in angulating or maintaining the guide catheter  110  in position during advancement of a therapeutic device. 
     A particular feature of the operative orientation of FIG. 9C is the supportive segment  132  of the tertiary curve portion  123  which continues to press against the postero-medial wall  516  to anchor the guide catheter  110  and acts as a portion of a rod or column of support between the roof  508  of the aortic arch  504  and the apex of the secondary curve portion  146  (which is maintained generally opposite the ostium  520  of the right main coronary artery  518  ). Note that even though the tertiary curve portion  123  has lifted off of the floor of the aortic arch, the full extent of the guide catheter  110  still provides a gradual smooth curvature throughout the aortic arch to maximize, or to the extent possible, mimic the gradual curvature of the aortic arch. One additional feature of the orientation of the guide catheter  110  in FIG. 9C that is advantageous as compared to the Arani-style guide catheter  400  shown in the FIGS. 2B and 2C, is that the area of contact between the tertiary curve portion  123  and the roof  508  of the aortic arch  504  is rather extensive (compared to a smaller area of contact for the Arani guide catheter). The greater contact area on the roof  508  assists to greatly prevent slippage of the guide catheter  110  during advancement of the balloon catheter therethrough. In addition, in combination with the area of contact provided-by the supportive segment  132  pressing against the postero-medial wall  516 , this contact with the roof  508  provides two relatively large areas of firm and stable support for the guide catheter  110  (in contrast to the relatively small points of contact provided by the Arani catheter  400 ). This further insures stability (i.e., preventing slippage) of the guide catheter  110  while providing enhanced backup support. 
     The orientation of the catheter in FIG. 9C further illustrates the convertibility of the guide catheter  110  of the present invention from the various positions shown in FIGS. 9A,  9 B, and  9 C. All of these positions provide tremendous backup support for advancing a balloon catheter, yet in slightly different capacities, while taking advantage of several distinct features of the guide catheter  110 , including the mild obtuse angle primary curve portion  140 , the support segment  132  of tertiary curve portion  123  and the “overcurved” nature of the tertiary curve portion  123 . Moreover, for all of these orientations shown in FIGS. 9A,  9 B and  9 C, the tip  142  of the guide catheter  110  is conveniently intubatable within the ostium  520  without any significant rotation of the guide catheter  110  when initially advanced into the aortic complex and the ascending aorta  512 . 
     FIG. 9D illustrates a further orientation of the guide catheter  110  of the present invention for a special application in which the lower portion of the ascending aorta  512  has an extensive bend, causing a greater curvature in the ascending aorta  512  and making the right main coronary artery  518  even more difficult to intubate and to provide suitable backup support. This “exit bend” of the ascending aorta  512  occurs about one to two inches above the aortic valve and is a pronounced medial curvature of the ascending aorta as shown in FIGS. 9A-9C at  513 . However, in some patient anatomies (typically older patients or patients with chest deformities), the “exit bend” of the ascending aorta is more pronounced. An example of a pronounced exit bend is illustrated in FIG. 9D at  515 . This pronounced exit bend at  515  creates additional challenges for a guide catheter to traverse this anatomical variation and to still provide superior stable backup support for angioplasty or the manipulation of other therapeutic devices. 
     The guide catheter  110  of the present invention is configured to conveniently adapt to this anatomical variation and provide more than adequate backup support as was described for FIGS. 9A,  9 B and  9 C. All of the orientations shown for FIGS. 9A-9C are obtainable in the anatomy shown for FIG.  9 D. FIG. 9D illustrates that the “overcurved” nature of the tertiary curve portion  123  readily adapts to an overcurved anatomy of the aortic arch  504  and ascending aorta  512  (particularly the postero-medial wall  516 ). The overcurved tertiary curve portion  123  allows the distal portion  116  of the guide catheter  110  to reach around the extensive curvature of the ascending aorta  512  even with the pronounced exit bend and still readily intubate the ostium  520 . As was seen in the orientations of FIGS. 9A-9C, the primary support generally opposite the ostium  520  is maintained in the region  517  of the postero-medial wall  516  by the supportive segment  132 , and substantially contiguous contact is maintained between the remaining proximal portions of tertiary curve portion  123  and the ascending aorta  512  and the aortic arch  504 . 
     FIG. 9E illustrates the modified guide catheter  110 A shown in FIG. 8C in use through the aortic system as viewed from an anterior posterior viewpoint as seen by a physician via fluoroscopy. The modified guide catheter  110 A is especially suited for patient anatomies in which the exit bend  515  is very pronounced. As shown in FIG. 8C, the guide catheter  110 A extends distally from the plane of the third segment  174  into the plane of the straight portion of the fourth segment  176  to mimic the angled orientation of the plane of the ascending aorta  512  as shown in FIG.  9 E. As seen in FIG. 9E, this multiplane, i.e., three dimensional, bending of the guide catheter  110 A allows the guide catheter  110 A in the distal portion  116  to better trace the three dimensional path of the ascending aorta  512  as it extends toward the heart, achieving an almost perpendicular (i.e., horizontal) orientation relative to the vertical orientation of the descending aorta  502 . FIG. 9E represents the position of the guide catheter  110 A in the same general orientation as in FIGS. 9A,  9 B and  9 D (and accordingly the heel of the catheter  110 A presses against the postero-medial wall  516 ). As shown, the location at which the third segment  174  extends within the ascending aorta  512  generally corresponds to the initial curvature of the ascending aorta  512  toward the heart. This allows the distal tip portion  142  of the guide catheter  110 A to properly angulate and mimic the orientation of the ascending aorta  512  and thereby enhance proper intubation of the right main coronary artery  518 . 
     FIG. 9F shows an orientation of the guide catheter  110 A in which the general orientation as in FIG. 9C is achieved. FIG. 9F is the cardiovascular system  500  as seen under fluoroscopy from the anterior posterior viewpoint. In the orientation of FIG. 9C, the tertiary curve portion  123  substantially contacts the roof  508  of the aortic arch  504 . However, in this orientation for multiplane three dimensional guide catheter  110 A, the third segment  174  is pushed against a wall of the ascending aorta  512  about the point where the curvature of the ascending aorta  512  toward the heart begins. This provides an additional area of support for the guide catheter  110 A against the wall of the ascending aorta  512  in addition to the primary area of support provided by supportive segment  132  pressing against the postero-medial wall  516  of the ascending aorta  512  and the support provided by contact of the tertiary curve portion  123  along the roof  508  of the aortic arch  504 . Thus, it can be seen that the advantageous features of the inventive guide catheter can be employed in extreme anatomical variations such as those shown in FIGS. 9E and 9F by modifications of the configuration of the guide catheter, including providing a multiplane distal portion and by using orientations such as shown by FIG. 9C to provide even more support for the guide catheter in those extreme anatomical situations requiring extra backup support. 
     Another embodiment of the present invention is a guide catheter  210 , illustrated in FIGS. 10A-10B in its relaxed state prior to insertion in a cardiovascular system. From its proximal end  220  to point  244  at the end of tertiary curve portion  223 , the shaft  212  of the guide catheter  210  is formed the same as guide catheter  110  described above. It differs from guide catheter  110  in its distal portion, distal of the tertiary curve portion  223 . The distal portion  216  of the guide catheter  210  includes the tertiary curved portion  223 , a secondary curved portion  246 , and a distal tip portion further includes a second straight portion  242 , a primary curved portion  247 , and a straight tip portion  250 . 
     The secondary curved portion  246  extends distally from the distal end of the tertiary curve portion  223  from the point  244  to a point  240  along the catheter shaft  212 . The second straight portion  242  extends distally from the point  240  to a point  244  along the catheter shaft  212 . The primary curved portion  247  extends distally from the point  244  to a point  248  along the catheter shaft  212 . The straight tip portion  250  extends distally from the point  248  to a point  251  which defines a terminal end of the catheter  210 . 
     As mentioned, the catheter shaft  212 , through the tertiary curve portion  223 , is the same as previously described. The secondary curved portion  246 , however, is different and is preferably comprised of three discrete segments: a first curved segment  234 , an intermediate straight segment  236 , and a second curved segment  238 . The first curved segment  234  forms an arc of about 20°, has a radius of about 2.0 centimeters, and is about 0.70 centimeters long (from point  244  to point  233  along the catheter shaft  212 ). The intermediate straight segment  236  extends distally from the distal end of the first curved segment  234  for about 0.5 centimeters (from point  233  to point  235  along the catheter shaft  212 ). The second curved segment  238  extends distally from the intermediate straight segment  234 , forms an arc of about 50°, has a radius of about 1.5 centimeters, and has a length of about 1.3 centimeters (from point  235  to point  240  along the catheter shaft  212 ). 
     The second straight portion  242  of the guide catheter  210  extends rectilinearly about 0.70 centimeters from the distal end of the secondary curved portion  246 , from the point  240  to a point  240 A along the catheter shaft  212 . The primary curved portion  247  extends distally from the point  240 A to a point  248 . The primary curved portion  247  forms an arc of about 25°, has a radius of about 2.0 centimeters, and is about 0.85 centimeters long. The straight tip portion  250  extends-distally from the primary curve portion  247  for about 1.35 centimeters. The primary curve portion  247  forms an obtuse angle of approximately 155° between the second straight portion  242  and the straight tip portion  250 . 
     The distance D 5  (see FIG. 10B) from the point at which the distal portion  216  overlaps itself to a point diametrically opposite therefrom along the tertiary curve portion  223  is about 7.35 centimeters. The distance D 6  in FIG. 10B is about 6.0 centimeters. The distance from the point  147  to the secondary curve portion  246  is about 8.5 to 9.5 centimeters when the catheter  210  is fully disposed in the right main coronary artery  518  (such as, e.g., disposed in FIG.  9 A). The length of the catheter  210  between the utmost distal end  251  of the catheter  210  and an apex of the primary curve portion  240  is about 1.8 centimeters. The length of the catheter  210  between the apex of the primary curve portion  240  and an apex of the second curved segment  238  is about 1.8 centimeters. The length of the catheter  210  between the apex of the second curved segment  238  and the apex of the first curved segment  234  is about 1.5 centimeters long. 
     As shown in FIG. 10A, the guide catheter  210  is constructed of three shaft segments, each with a different degree of flexibility. The guide catheter  210  in FIG. 10A has a first flexibility segment  260  with a Shore D hardness of 63, a second increased flexibility segment  264  with a Shore D hardness of 40, and a third, further increased flexibility tip segment  266  with a Shore D hardness of about 35. A bond ring member  262  is sandwiched between a distal end of the first segment  260  and a proximal end of the second segment  264 , and has a hardness of about 51. As shown, the bond ring member  262  is preferably positioned just distal to the primary curve portion  240 . In an alternate embodiment, the bond ring member  262  can be positioned proximally of the proximal curve portion  240 . Instead of the triple flexibility segment construction, the guide catheter  210  can have a double flexibility segment construction as described for the guide catheter  110 . In addition, for both the double and triple flexibility segment constructions of the guide catheter  210 , the same materials (e.g., PEBAX® material, TEFLON® material, wire braiding and radiopaque agents) can be used as was described for the guide catheter  110 . Moreover, the method of forming the preshaped configuration of the guide catheter  210  is the same as described for the guide catheter  110 . 
     An alternate embodiment of guide catheter  210  extends in multiple planes with a three dimensional distal portion  216  like that of guide catheter  110 A as shown in FIG.  8 C. The segments of the guide catheter  210 A have the same lengths and angles and curvatures as the guide catheter  110 A as seen in the top view of FIG. 8C despite the guide catheter  210  having slightly different dimensions for portions  250 ,  242 , and  246  as seen in FIGS. 10A and 10B. 
     The guide catheter  210  is inserted into the cardiovascular system in the manner previously described for guide catheter  110  and as depicted in FIGS. 9A-9F. The guide catheter  210  assumes the same advantageous orientation within the ascending aorta  512  and ostium  520  of the right main coronary artery  518  as is shown in FIGS. 9A-9F (as shown for the guide catheters  110  and  110 A). The guide catheter  210 , because of its slightly altered construction adjacent its distal end, provides a longer effective tip length for the guide catheter, to aid in extending across the ascending aorta and into the right coronary artery. 
     A modification of the embodiment shown in FIGS. 10A-10B is especially suited for catheterization of a “Shepherds Crook” anatomical variation of the right main coronary artery. The modification includes altering the distal straight tip portion  250 , the primary curve portion  247 , and the second straight portion  242 . The distal tip portion  250  is lengthened to about 2 centimeters and the second straight portion  242  is shortened to about 0.25 centimeters. The arc of primary curve portion  247  is tightened to about 35° (having a radius of curvature of about 2.0 centimeters), and the length of the arc extended to about 1.2 centimeters. This modification of the guide catheter  210  facilitates intubation of a “Shepherds Crook” formed right main coronary artery which has a severe superior take-off orientation where the artery extends upwardly, for a portion, almost parallel to the ascending aorta  512 . Other than these slight modifications of the guide catheter  210  in the three portions  250 ,  247 , and  242 , the alternate embodiment for the Sheperds Crook anatomical variation is same as the guide catheter  210  shown in FIGS. 10A and 10B. 
     However, the alternate embodiment of guide catheter  210  adapted for the Sheperds Crook variation also can be modified into a multiplane three dimensional embodiment similar to the embodiment shown in FIG.  8 C. 
     As seen in FIG. 10C, a three dimensional guide catheter  260  is shown having first, second and third segments  270 ,  271  and  273  which are the same as segments  170 ,  172  and  174 , respectively as the guide catheter shown in the view of FIG.  8 C. Distal of the third segment  273 , the catheter  260  has a fourth segment  272  with a proximal portion extending from the third segment  273  and a straight portion with a length of about 2.35 centimeters. The angle between the plane traversed by the third segment  273  and the plane traversed by the straight portion of the fourth segment  272  is about 45°. The fourth segment of catheter  268  crosses over the first segment  270  at about the same angle of 130 degrees (i.e., α 2 ). Extending distally from the fourth segment  272  is a fifth segment  274  having a radius of curvature of about 10 centimeters and forming an arc of about 50 degrees. A sixth segment  276  extends distally from the fifth segment  274  and has a radius of curvature of about 1.0 centimeters and forms an arc of about 60 degrees. A straight seventh segment  278  extends distally from the sixth segment  276  for about 1.1 centimeters. The distances D 7  and D 8  are the same as the distances D 3  and D 4 , respectively, for the guide catheter shown in FIG.  8 C. 
     FIG.  11  and FIG. 12 show additional embodiments of the guide catheter of the present invention which are variations of the basic configuration of the guide catheters shown in FIGS. 8A-8B and  10 A- 10 B. These additional embodiments are especially suited for intubating saphenous bypass grafts of the ascending aorta  512  in the vicinity of the left and right main coronary arteries. A saphenous bypass graft typically involves using a great saphenous vein from the leg as a graft onto the wall of the ascending aorta to bypass an occluded main coronary artery. 
     The guide catheters  110  and  210  of the present invention can be used for intubating the ostium of a saphenous bypass graft by making relatively slight modifications in the shape of the distal portion of the catheter. FIG. 11 is an end view of a catheter  700 , as taken from the right side of a catheter view such as FIG.  10 A. The guide catheter  700  is adapted for use in treatment of a left saphenous vein bypass graft. The guide catheter  700  depicted in FIG. 11 corresponds in every capacity to the guide catheter  210  of FIGS. 10A-10B except for the out-of-plane modifications adjacent its distal end. As shown in FIG. 11, the distal portion of the guide catheter  700  is bent out of plane consecutively at two different angles. The first out of plane portion  702  extends at angle of about 20 degrees away from the first plane of the catheter  700  at a bend  704 . The bend  704  is located approximately at the apex of a second curved segment of a secondary curve portion of the catheter body (i.e., at the apex of the second curved segment  238  of the secondary curve portion  246  for the guide catheter  210 ). The second out of plane portion  710  extends from the first out of plane portion  702  at angle of about 40 degrees relative to the first plane of the catheter  700  at a bend  712 . The bend  712  is located approximately at the apex of a primary curve portion of the catheter body (i.e., at the apex of the primary curve portion  247  for the guide catheter  210 ). The configuration of the guide catheter  700  permits coaxial intubation and provides backup support for an angioplasty procedure through a left saphenous vein bypass graft in a cardiovascular system. Because the guide catheter  700  has the same basic structure as the guide catheter  210 , the guide catheter  700  enjoys all the advantages of the catheter  210  when deployed in the cardiovascular system. 
     An alternate embodiment of the catheter  700  for use in left saphenous bypass graft has the same out of plane bending as shown in FIG. 11 but also includes modifying the lengths of the following portions of the guide catheter  210  as seen in FIG.  10 B: a second straight portion (like the second straight portion  242  of the guide catheter  210 ) is lengthened to about 1.20 centimeters and a distal tip straight portion (like straight tip portion  250  of the guide catheter  210 ) is lengthened to about 1.85 centimeters. 
     A guide catheter  800  is shown in FIGS. 12A and 12B, and is adapted for use in treatment of a right saphenous vein bypass graft. FIG. 12A is a side view like FIG. 10A but only showing the distal end portion of the guide catheter  800 . FIG. 12B is an end view of the guide catheter  800 , as taken from the right side of a catheter view such as FIG.  10 A. The guide catheter  800  depicted in FIG. 12A corresponds in every capacity to guide catheter  210  shown in FIG. 10A except for the out-of-plane modifications adjacent its distal end (FIG. 12B) and a reverse orientation of primary curve portion  802  (as compared to primary curve portion  247  in FIG.  10 A). The interior of the arc of the primary curve portion  802  is disposed oppositely from the orientation of the primary curve portion  247  shown in FIG.  10 A. The primary curve portion  802  the guide catheter  800  has a radius of curvature of 2.0 centimeters and forms an arc of about 25 degrees. As shown in FIG. 12B, the distal portion of the catheter is bent out of plane in one plane. The first out of plane portion  810  extends at an angle of about 30 degrees away from the first plane of the catheter  800  at a bend  812 . The bend  812  is located approximately at the apex of the primary curve portion  802  of the catheter body (i.e., at the apex of the primary curve portion  247  of the guide catheter  210 ). The configuration of the guide catheter  800  permits coaxial intubation and provides backup support for an angioplasty procedure through a right saphenous vein bypass graft in a cardiovascular system. Because the guide catheter  800  has the same basic structure as the guide catheter  210 , the catheter  800  enjoys all the advantages of the catheter  210  when deployed in the cardiovascular system. 
     It is thus seen that the guide catheters of the present invention are specifically configured for more precise coaxial alignment with a selected (e.g., right main) coronary artery in the cardiovascular system without the need to rotate the catheter. Also, the guide catheters of the present invention provide improved support and guidance of associated therapeutic devices, such as balloon catheters, during angioplasty. Further, the guide catheters of the present invention form relatively small angles when inserted in the cardiovascular system, thus minimizing the dissipation of axial forces during use. In addition, the inventive guide catheters can be formed so as to maintain these characteristics even after warming to body temperature or when the aortic arch is overcurved. 
     It is understood that several variations may be made in the foregoing without departing from the scope of the invention. For example, the catheters embodied in the present invention are not limited for use as guiding catheters but can have other uses for treatment of the cardiovascular system, such as use as diagnostic, balloon, laser and atherectomy catheters, etc. The catheters of the present invention may also be introduced to the aorta via the brachial or axillary artery in addition to the femoral artery. Further, the present invention can be used to form catheters for use in cases of posterior take-off of the right coronary artery. Also, the specific lengths and angles of the specific examples of the catheters of the present invention set forth above can be varied within the scope of the invention. In addition, although the angles A 1  (FIG. 4B) and A 4  (FIG. 6B) have been shown at the apex of the curved portions  54  and  82 , it is understood that they could be located at other portions of the curved portions  54  and  82 . Moreover, it is understood that, instead of the well defined lengths and angles shown and described in the above examples, the bent distal end portion of the a catheters of the present invention can form more smoother curves within the scope of the invention. 
     It should also be understood that the embodiments of FIGS. 3A-7A can be made with the materials and by the technique described for the embodiments of FIGS. 8A and 10A. Moreover, features of the various embodiments ( 3 A- 8 A,  8 C,  10 A,  10 C,  11 , and  12 A- 12 B) can be combined with each other to achieve additional optimal combinations of catheter configurations within the scope of the present invention. 
     Other modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.