WO1994008523A1

WO1994008523A1 - Forward ablating directional catheter

Info

Publication number: WO1994008523A1
Application number: PCT/US1993/010052
Authority: WO
Inventors: William B. Anderson; Tsvi Goldenberg
Original assignee: Advanced Interventional Systems, Inc.
Priority date: 1992-10-21
Filing date: 1993-10-20
Publication date: 1994-04-28

Abstract

A laser catheter (10) for ablating plaque eccentrically disposed on the inner wall of a blood vessel includes a catheter body (30) having an axis and an outer wall (41) extending between a proximal end (34) and a distal end (36). A plane (43) extends across the catheter body (30) to opposing sides of the outer wall and forms with first circumferential portions (105, 107) of the outer wall a first lumen (45). Second circumferential portions (110, 112) of the outer wall define with the plane a second lumen (47) within which is disposed a plurality of optical fibers (65). The first portions (105, 107) extend beyond the distal surface of the catheter body (30) to form a tongue (101).

Description

FORWARD ABLATING DIRECTIONAL CATHETER

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to catheters for increasing the patency of blood vessels restricted by atherosclerotic plaque, and more specifically to apparatus and techniques for using a laser catheter for the ablation of atherosclerotic plaque.

Discussion of the Prior Art

Atherosclerotic plaque includes calcium, cholesterol and other materials which form a relatively hard deposit on the interior surface of a blood vessel. Such deposits, commonly referred to as lesions, are of particular concern in the coronary arteries where they can restrict blood flow to the heart and create an infarction or heart attack. Interventional cardiologists have developed techniques for addressing the occlusive lesions by compressing, removing, or in the case of a laser catheter, ablating the plaque.

Balloon catheters have been employed for compressing the plaque against the interior wall of the vessel. While this initially tends to open the occlusion, the plaque often redeposits at the same location requiring further surgery at a later date. Balloon angioplasty also tends to create tears in the vessel walls since the plaque has a higher density and is less elastic than the blood vessel. Balloon angioplasty can be particularly damaging at a bifurcation where expansion of one vessel can result in closure of the adjacent vessel.

Atherectomy catheters have also been used to cut and remove plaque from the vessels. These devices typically consist of a metal barrel having a lateral window that is pushed into proximity with the plaque by an opposing balloon. A rotating blade cuts the plaque at the lateral window and removes it to a distal location. Since this procedure also employs a balloon, it suffers from the disadvantages previously discussed. In addition, the athrectomy catheter must be advanced beyond the lesion in order to move the lateral window into proximity with the plaque. This advancement typically occurs with two possibilities. Either the vessel is highly traumatized, or the vessel must be predilated. In the later instance, predilation typically cracks the plaque and creates fissures which ultimately interfere with the athrectomy process.

More recently, laser catheters have been employed for the ablation of plaque. The orientation of these catheters is critical since the laser fluence which radiates distally and outwardly can damage the vessel wall. This has been a particular problem where the plaque is eccentrically located on one side of the vessel leaving the opposite side of the vessel, sometimes referred to as the thin side, exposed. Absorbers have been provided for use with an optical element which directs the laser fluence toward the absorber, oblique to the forward direction. In the case of German Patent No. DE3617-09-A, the absorber has received the incident radiation to prevent damage to the thin side of the vessel. While such an absorber may provide some protection against radiation, it does not provide any means for determining the radial orientation of the catheter or means effecting a change in the radial orientation.

SUMMARY OF THE INVENTION

These deficiencies of the prior art are overcome with the present invention. In a preferred embodiment a tongue is provided at the distal end of the catheter. This tongue functions as a radiation absorber and a mechanical barrier to the distal fiber tips but it also assists in the radial orientation of the catheter relative to an eccentric lesion. The tongue includes a distal tip and lateral edges which diverge proximally to a distal surface of the catheter. In response to axial movement of the catheter, these lateral edges of the tongue perform a camming action which rotates the catheter about its axis and into a preferred radial orientation. In this preferred orientation, the optical fibers are automatically positioned to ablate the plaque while the tongue is positioned to protect the thin side of the vessel. Thus the tongue functions not merely as an optical absorber, but also as a mechanical projection for maintaining the catheter in a coaxial alignment with the vessel and for achieving the desired radial orientation of the catheter relative to the lesion.

This angular orientation of the catheter can be facilitated by provision of a torque wire. The torque wire can be twisted from the proximal end of the catheter where an actuating mechanism is provided. Means for limiting the amount of twist imparted to the torque wire insures that neither the torque wire nor the optical fibers are twisted beyond a breaking point.

In one aspect of the invention, a laser catheter is adapted for use in ablating plaque eccentrically disposed against the inner wall of a blood vessel. This catheter includes a catheter body having an axis and an outer wall extending between a proximal end and an opposing distal end, the catheter body being characterized by a distal surface and a plane of separation at the distal end of the catheter. First portions of the outer wall extend circumferentially of the catheter body on one side of the plane of separation while second portions of the outer wall extend circumferentially of the catheter body on the other side of the plane of separation. A multiplicity of optical fibers are disposed within the catheter body on the one side of the separation plane and extend to the distal surface. The first portions of the catheter body extend distally of the distal surface and form a tongue having a distal tip and lateral edges diverging proximally from the distal tip into proximity with the plane of separation.

In another aspect of the invention, a wire is disposed in the catheter body and provides a radiopaque image including a first edge extending generally longitudinally of the catheter. A marker disposed laterally of the wire provides a radiopaque image including a second edge which overlaps the first edge when the catheter is in an undesirable radial orientation within the conduit and is spaced from the first edge when the catheter is in a desired radial orientation within the conduit.

In an additional aspect of the invention, a torque wire is connected to the distal end of the catheter body and is operable from the proximal end for axially twisting the catheter body to achieve an desired angular orientation within a body conduit. This torque wire is operable over a preferred range of angular displacement. An actuating mechanism at the proximal end of the catheter body imparts axial twist to the torque wire while a torque limiter limits the extent of the imparted twist to the preferred range of angular displacement.

In a further aspect of the invention a plurality of laser fibers extend to the distal end of the catheter body and produce laser fluence which projects along a fluence path extending beyond the distal end of the catheter. Portions of the catheter body form a tongue at the distal end of the catheter, the tongue having a first position in the fluence path to protect the blood vessel from the laser fluence and a second position removed from the fluence path to permit measurement of the laser fluence.

A method for axially orienting a catheter within a body conduit includes the steps of providing a first radiopaque marker forming a first image having a first edge, and providing a second radiopaque marker forming a second image having a second edge. The method includes the step of twisting the catheter to provide the first edge and the second edge with a predetermined spaced relationship indicative of a desired angular orientation of the catheter. This orientation is particularly valued in the case of a laser catheter having eccentric fibers which must be oriented relative to an eccentric lesion while protecting the thin side of the blood vessel.

These and other features and advantages of the invention will be more apparent with a description of preferred embodiments of the invention and reference to the associated drawings. DESCRIPTION OF THE DRAWING

Fig. 1 is a side view of a laser catheter system for ablating plaque from a blood vessel;

Fig. 2 is a bottom view of the distal tip of the catheter illustrated in Fig. 1;

Fig. 2A is a cross section view taken along lines 2A- 2A of Fig. 2;

Fig. 2B is a cross section view taken along lines 2B- 2B of Fig. 2;

Fig. 3 is an end view of the distal tip illustrated in Fig. 2;

Fig. 4 is an axial cross-section view taken along lines 4-4 of Fig. 2;

Fig. 5 is a cross-section view taken along lines 5 - 5 of

Fig. 4;

Fig. 6 is a radial cross-section view taken along lines 6-6 of Fig. 4;

Fig. 7 is a radial cross-section view taken along lines 7-7 of Fig. 4; Fig. 8 is a cross-section view similar to Fig. 4 illustrating the tongue of the catheter being bent back to permit measurement of the laser fluence;

Fig. 9 is a top plan view illustrating a camming action between a tongue of the catheter and a lesion in the vessel;

Fig. 10 is an axial cross-section view of a torque limiter illustrated in Fig. 1;

Fig. 11 is a radial cross-section view of a further embodiment of the catheter wherein the optical fibers are stranded;

Fig. 12 is an axial cross-section view taken along lines 12-12 of Fig. 11;

Fig. 13 is a side view of a marker system facilitating radial orientation of the catheter and illustrating proper alignment of the components of the marker system; and

Fig. 14 is a side view of the marker system similar to Fig. 10 and illustrating improper alignment of the components of the marker system.

Fig. 15 is an axial cross-section view similar to Fig. 4 and illustrating a further embodiment of the invention; and

Fig. 16 is a cross-section view taken along lines 16- 16 of Fig. 15. DESCRIPTION OF PREFERRED EMBODIMENTS AND BEST MODE OF THE INVENTION

A laser catheter is illustrated generally in Figure 1 and designated by the reference numeral 10. This catheter 10 is representative of catheters, trocars, endoscopes and other types of access devices which may be used to gain access to a body conduit such as a blood vessel 12. The laser catheter 10 is particularly adapted for use in ablating or otherwise removing plaque 14 from an interior surface 16 of the vessel 12. This plaque 14 will typically form a lesion 18 on one side of the vessel 12. This side of the vessel 12 is sometimes referred to as the thick side 21, which the side opposite the lesion 18 is referred to as the thin side 23.

A common method for inserting the catheter 10 into proximity with the lesion 18 employs a guide wire 25 which is initially inserted through the existing opening of the vessel 12, along the thin side 23, and across the lesion 18. After the guide wire 25 is in place, the catheter 10 can be slid over the guide wire and moved axially tracking the guide wire 25 into proximity with the lesion 18.

The laser catheter 10 includes an elongate catheter body 30 which extends along an axis 32 between a proximal end 34 and an opposing distal end 36. The distal end 36 of the catheter 10 is best illustrated in the longitudinal view of Figure 4 and the associated cross sections of Figure 5-7. In this particular embodiment, the catheter body 10 includes an outer wall 41 and is characterized by a plane of separation 43 which is spaced from the axis 32 and divides the catheter into a relatively small longitudinal section 45 and a relatively large longitudinal section 47. The catheter body 30 can be formed from a - in ¬ flexible plastic such as urethane, polyethylene or polyvinylchloride.

An inner tube 50 is disposed in the small section 45 and extends between the proximal end 34 and distal end 36 to receive the guide wire 25. A smaller tube 54 is also disposed in the small section 45 and is configured to receive a torque wire 56 which is described in greater detail below. Both of these tubes are preferably formed from the low friction material, such as tetrafluoroethylene which facilitates sliding movement of the wires 25 and 56 within their respective tubes 50 and 54.

The small tube 54 also extends from the proximal end 34 toward the distal end 36 of the catheter 10. However, the distal end of the small tube 54 is foreshortened to permit the torque wire 56 to extend beyond the tube 54 and to be fixed to the distal end 36 of the catheter 10, for example with epoxy 58. A distal end 57 of the torque wire 56 is flattened and twisted to increase the cross-sectional area of the torque wire and facilitate anchoring the distal end 57 in the epoxy 58. This increases the surface contact with the epoxy 58 and enhances the torque characteristics of the catheter 10.

The large section 47 formed by the outer wall 41 and the plane 43 is preferably filled with a plurality of optical fibers 65 which extend from the proximal end 34 to a distal surface 67. This surface 67 is polished and oriented at an angle relative to the axis 32, which is typically not less than 90°. In a preferred embodiment, the angle is 112.5°. Up to the distal end 36, the optical fibers 65 are preferably free floating and have a generally parallel orientation. In a preferred embodiment each of the fibers has a core diameter of approximately 50 microns.

Referring again to Figure 1, it will be noted that the proximal end 34 of the catheter 10 includes a catheter hub 70 which divides the optical fibers 65, the torque wire 56, and the large tube 50 to facilitate implementation by the physician. This hub 70 includes a first branch 72 which receives the optical fiber 65 and is provided with a fitting suitable for connection to a laser 76. This laser 76 can be any type of laser providing fluence at a medically significant wavelength, for example a wavelength in a range between 0.2 and 12 microns. In a preferred embodiment, the laser 76 is a Xenon Chloride Excimer Laser providing a pulsed output at frequencies in a range between 5 and 30 Hertz, a wavelength of about 0.308 microns, and a pulse duration of about 100 nanoseconds.

A second branch 78 of the hub 70 receives the proximal end of the tube 50 and includes a suitable fitting 81 to facilitate introduction of the catheter 10 over the guide wire 25.

A third branch 85 of the hub 70 is configured to receive the torque wire 56. This branch 85 terminates in a twisting mechanism 87 which includes a torque limiter 90 described in greater detail below.

Of particular interest to the present invention is a tongue 101, best shown in Figure 2 and 4, which is disposed at the distal end 36 of the catheter 10. This tongue 101, preferably extends distally of the surface 67 and can be formed as an extension of the outer wall 41. The tongue 101 has a distal tip 103 and a pair of wings 105 and 107 which, in a preferred embodiment, converge distally around - li ¬ the guide wire tube 50. These wings 105 and 107 have lateral edges 108 and 109 respectively which contact the surface 67 in close proximity to the plane 43. For example, as illustrated in Figure 5, the lateral edges 108 and 109 may contact the plane 67 at opposing points 110 and 112 respectively. It is particularly desirable that these points 110 and 112 be sufficiently close to the separation plane 43 to inhibit any laser fluence emanating from the fibers 65 from contacting the thin side 23 of the vessel 12. In a preferred embodiment, the points 110 and 112 are separated from the plane 43 by a layer of epoxy which is less than about .005 inches.

One of the purposes of the tongue 101 is to provide a barrier along the thin side 21 of the vessel 12 which will prevent the laser energy or fluence from contacting the wall of the vessel 12. This laser fluence would typically extend, in a transparent medium, along a diverging path, such as illustrated by the dotted lines 114 in Figure 8, and could contact the vessel 12 on the thin side. However, with the tongue 101 extending into close proximity to the separation plane 43, the fluence path 114 in the lateral direction is blocked to protect the vessel 12. This absorption function is best served by an embodiment wherein wings 105, 107 of the tongue 101 extend circumferentially along the outer wall 41 to the points 110 and 112 where the optical fibers 65 contact the distal surface 67.

Particularly in a transparent field, the absorption of laser fluence can be particularly critical. In a further embodiment of the invention a laser transmissive fluid such as saline can be introduced through a separate lumen to provide a generally transparent environment into which the laser fluence is introduced. The transparent saline environment facilitates transmission of the laser fluence. but it also increases the risk of damage to the blood vessel 12. In this context the tongue 101 is of particular advantage due to its absorption characteristics.

Absorption of laser fluence may be of lesser concern in a blood field since the fluence does not travel a great distance. In this case, the tongue 101 need not function as an absorber, but it is still advantageous as a mechanical projection or barrier which protects the vessel from the cutting tips of the fibers. This is most critical at a bend in the vessel where axial movement of the catheter would tend to force the fiber tips against the vessel wall. In this case, the tongue 101 is most advantageous for its mechanical disposition between the fiber tips and the vessel wall.

With the tongue 101 formed as an axial projection of the outer wall 41 of the catheter body 30, it is well located to receive an extension of the guide wire tube 50. In a preferred method for positioning the catheter 10, the guide wire 25 is initially passed through the vessel 12 up to and preferably across the lesion 18. Then the eccentric guide wire tube 50 of the catheter 10 is fed over the guide wire 25. This procedure tends to automatically position the tongue 101 on the thin side 23 of the vessel 12 with the distal surface 67 facing the lesion 18.

The tongue 101 is of a further advantage due to its location distally of the ablating distal surface 67. As ablation occurs, the catheter can be moved axially to bring the distal surface 67 into contact with additional plaque 14. This axial movement could tend to bend or tip the catheter due to the eccentric location of the force resisting axial movement. This force, created by the contact between the lesion 18 and the distal surface 67, is spaced from the axis and consequently tends to tip the catheter off axis. However, in accordance with this invention the tongue 101 functions as means for providing an opposing force which tends to maintain the catheter 10 in its desired axial location. Thus, the tongue 101 provides an enlarged longitudinal structure which contacts both the lesion 18 and the vessel 12, thereby preventing any tipping of the catheter 10 from its desired axial orientation.

The lateral edges 108 and 109, which converge distally along the tongue 101 also assist in the radial orientation of the catheter 10. As the catheter 10 is moved axially through the blood vessel 12, these lateral edges 108 and 109 may contact the lesion 18. Further axial movement of the catheter 10 causes these edges 108, 109 to slide along the lesion 18 in a camming action which tends to axially rotate the catheter 10 and the tongue 101 toward the thin side 23 of the vessel 12. This feature is best illustrated in Figure 9 wherein axial movement of the catheter 10 along an arrow 121 tends to axially rotate the catheter 10, for example along an arrow 123, to the preferred radial orientation.

In any laser catheter, the amount of energy or laser fluence emanating from the distal end of the catheter is of particular interest. As illustrated in Figure 8, this laser fluence is typically measured by a detector 116 which is disposed in the fluence path represented by the dotted lines 114. In the case of the catheter 10 it is of particular interest that the tongue 101 can be bent back on itself as illustrated in Figure 8, to a position where it is removed from the fluence path 114. This permits measurement of the laser fluence in a conventional method even in an embodiment where the catheter 10 includes an absorber, such as the tongue 101, which extends beyond the distal surface 67.

While the distal convergence of the lateral edges 108 and 109 can occur anywhere along the tongue 101, it is particularly desirable for this converging section to be disposed in close proximity to the distal surface 67. Since the structure is more flared at this location, as shown by Figure 2A, its bending characteristics may be somewhat weaker thereby facilitating bending of the tongue 101 as illustrated in Figure 8.

This preferred angular orientation of the catheter 10 is further enhanced by the torque wire 56. As previously noted, a proximal end 130 of the wire 56 is received in the twisting mechanism 87 while a distal end 57 is fixed by the epoxy 58 at the distal end 36 of the catheter 10. Any twist imparted to the proximal end 130 is transmitted down the torque wire 56 and tends to axially rotate the distal end 36 of the catheter. Of course if the torque wire 56 is twisted beyond its limits, it may break or otherwise buckle thereby interfering with further orientation of the catheter. For this reason, the torque limiter 90 is provided to maintain any twist imparted to the torque wire 56 to a preferred range such as three revolutions on either side of normal.

The twisting mechanism 87 and torque limiter 90 are best illustrated in Figure 9. The mechanism 87 includes a housing 141 having internal threads 143 and external threads 144. The external threads 144 of the housing 141 are adapted to receive a cap 145 having an axial opening 147 and an internal, distally-facing surface 148. The internal threads 143 extend axially distally from an interior proximally-facing surface 146 of the housing. A torque knob 152 is connected to a shaft 154 which extends through the opening 147 in the cap 145. The shaft 154 has an enlarged section 156 which is disposed within the housing 141 and has a proximally-facing surface 157 and a distally-facing surface 158. Distally of the enlarged section 156 a projection 160 extends axially of the surface 158 and is provided with exterior threads 163 which mate with the interior threads 143. The projection 160, the enlarged portion 156, and the shaft 154 are provided with an axial bore which is adapted to receive the torque wire 56. At the proximal end 130, the torque wire 56 is bent laterally and received in a longitudinal slot 170 which is formed in the shaft 154.

In operation, the torque knob 154 can be rotated pressing the sides of the slot 170 against the distal end 130 of the torque wire 56. This imparts twist to the torque wire 56 which is transmitted along the wire to the distal end 57. The twist in the torque wire creates strain which is imparted to the distal end 36 of the catheter 10 and which tends to rotate the catheter about the torque wire 56.

As the knob 152 is turned, the shaft 154 also rotates and moves axially by operation of the screw threads 143 and

163. Rotation of the knob 152 in one direction moves the surface 158 into proximity to the interior surface 146 of the housing 141. Rotation of the knob 152 in the opposite direction moves the surface 157 into proximity with the interior surface 148 of the cap 145. If either of these pairs of surfaces 158 and 146, or 157 and 148, come into contact, further rotation of the knob 152 in that direction is prohibited. It can be seen that the radial twisting of the torque wire 56 is accompanied by axial displacement of the shaft 154. Thus the torque limiter 90 provides means for inhibiting axial travel of the shaft 154 in order to limit the radial twist of the torque wire 56. In this manner, the enlarged portion 156 of the shaft 154 functions to limit the amount of twist or torque which can be imparted to the torque wire 56. In a preferred embodiment, the range of twist is limited to three revolutions on either side of normal. This limitation on rotation is controlled of course by the pitch of the screw threads 143, 163 and the spacing of the surface pairs 146, 158 and 148, 157.

The torque wire 56 can be completely omitted in an embodiment wherein the optical fibers 65 are twisted or stranded as disclosed in applicant's co-pending application Serial No. 07/937,065 filed on August 26, 1992 and entitled Optical Catheter with Stranded Fibers. In accordance with this method and apparatus, the optical fibers 65 are twisted in a spiral configuration to form multiple cylindrical layers with adjacent layers spiraling in opposite directions. This configuration provides superior torque characteristics for the catheter 10 and eliminates the need for a separate torque wire 56 or torque limiter 90.

In an embodiment, illustrated in Figures 11 and 12, the optical fibers 65 are spiraled in separate layers 165, 166 and 167 around a core 168 which may have either a tubular or solid configuration. For example, the core 168 may comprise a single optical fiber. In the illustrated embodiment, the core 168 is offset from the axis 32 of the catheter 10, so the optical fibers 65 have an eccentric orientation. This is particularly appreciated in an embodiment wherein tubes 50, 54 are also eccentrically positioned on the side of the catheter 10 opposite the optical fibers 65. Although the stranded fibers 65 are illustrated to have a cylindrical configuration, they can be otherwise stranded to fill a non-circular cross-sectional shape. Alternatively, multiple bundles of stranded fibers can be positioned within a single catheter. Any space not occupied by the guide tube 50 or the optical fibers 65 can be filled with epoxy, can be occupied by other tubes or other means defining lumens through the catheter 10. For example, separate tubes 169 can be provided to accommodate the introduction of saline or other infusate. This additional space may also be filled with non-stranded fibers having the generally parallel configuration previously described.

While all of these features facilitate the radial orientation of the catheter 10, it is still desirable to provide some means for visualizing when the catheter 10 is disposed in a preferred radial disposition relative to the lesion 18. This visual indication is provided in a preferred embodiment by a radiopaque marker system which incudes a first marker and a second marker. The first marker, which may comprise the guide wire 25, provides a radiopaque image including a line, such as that is designated by the reference numeral 171 in Figure 13.

A second marker 172 can be disposed at the distal end 36 of the catheter 10 preferably in proximity to the line 171 of the first marker. This second marker 172 may have the configuration of a half-cylinder having a lateral edge providing a radiopaque image in the form of a second line 175 in proximity to the first line 171. In a preferred embodiment, the second marker 172 is configured to extend circumferentially outwardly of the optical fibers 65 in radially spaced relationship with the tube 50. This insures that in at least one angular orientation of the catheter 10, a minimal radiopaque gap will exist between the guide wire 25 and the marker 172. This minimal alignment gap is designated by the reference numeral 176 in Figure 5. If of the edge or line 175 is spaced from the rotational axis, torquing of the catheter 10 about the axis will move the radiopaque image of the lines 171 and 175 relative to each other. Thus by merely viewing the radiopaque images one can see for example, that if the lines 171 and 175 overlap, the catheter 10 is in an undesirable orientation relative to the lesion 18, as illustrated in Figure 14. If, however, the lines 171 and 175 are spaced or have some other predetermined orientation, the marker system will provide an indication that the catheter 10 is properly oriented relative to the lesion 18, as illustrated in Figure 13.

A further embodiment of the invention is illustrated in Figures 15 and 16 which are similar to Figures 4 and 5, respectively. In this particular embodiment elements which are similar to those previously discussed are designated by the same reference numeral followed by the lower case letter "a". For example, this embodiment also includes an outer wall 41a, tongue 101a, torque wire 56a, and large tube 50a. The optical fibers 65a are disposed on the opposite side of the separation plane 43 from these elements.

In this particular embodiment, the radiopaque marker 172a is provided in the configuration of a sleeve having a circumferential section 178 and a transverse section 180. The sleeve is configured to receive the optical fiber 65a with the circumferential section 178 disposed radially outwardly of the fiber 65a and the transverse section 180 extending along the separation plane 43a. A pair of holes 182 and 184 are provided in the transverse section 180 so that epoxy can extend through the holes 182, 184 on both sides of the separation plane 43. On one side of the plane 43, the epoxy 58a fills the interstices of the optical fibers 65a within the sleeve formed by the marker 172a. On the other side of the plane 43a, the epoxy extends through the holes 82, 84 and surrounds the tube 50a and torque wire tube 54a. As best shown in Figure 15, the outer wall 41 of the catheter 10 abuts the proximal edge of the radiopaque marker 172a so that the marker of this embodiment is visible on the outer surface up to the distal surface 67. In this embodiment, both the circumferential section 178 and transverse section 180 of the marker 172a have a thickness of about .003 inches.

In a radiopaque image, the outer surface of the transverse section 180 will form the image line 175. The separation between this line and the guide wire 25 in the radiopaque image will be not less than the thickness of the tube 50a as shown by the reference numeral 176a in Figure 16.

In the two illustrated embodiments of Figure 5 and 16, some of the dimensions are the same. For example, measured perpendicular to the plane 43, the bundle of optical fibers 65 has a height of about .033 inches. The tube 50 has an outside diameter of about .025 inches and the outer wall 41 has the thickness of about .005 inches. In the embodiment of Figure 16 wherein the circumferential section 168 and transverse section 180 each have a vertical dimension of .003 inches, the catheter has an overall diameter of about 1.8mm. In the embodiment of Figure 5, wherein the marker 172 has a single thickness of .003 inches, the epoxy surrounding the marker 172 and optical fiber 65 may have a thickness of about .004 inches so that the catheter has an overall dimension of about 1.8mm. There are many variations in the foregoing concept. Certainly the materials, which are not critical to the present invention, can be varied to achieve structural characteristics which are desirable for a particular embodiment. The configuration of the tongue 101 can also be varied as long as it has lateral edges which converge from the separation plane distally thereby providing a camming surface for angular orientation of the catheter. Other configurations for the radiopaque markers will also be apparent as long as they provide different radiopaque images based on the angular orientation of the catheter.

Other embodiments for a torque limiter will also be of interest as long as they provide an interference fit between relatively movable structures at the respective twisting limits for a torque wire.

Although the invention has been disclosed with reference to preferred embodiments, it will be apparent that these features can be altered to accommodate other laser catheter systems. By way of example, it is apparent that the catheter body 10 can be formed without a plane 43 and that the tongue 101 can be otherwise configured. For example, the lateral edges 105 and 107 can diverge at different angles and can engage the lateral surface 67 at a variety of angles to facilitate radial orientation of the catheter 10.

Given these wide variations, which are all within the scope of this concept, one is cautioned not to restrict the invention to the embodiments which have been specifically disclosed and illustrated, but rather encouraged to determine the scope of the invention only with reference to the following claims.

Claims

1. A laser catheter adapted for use in ablating plaque eccentrically disposed against an inner wall of a blood vessel, comprising: a catheter body having an axis and an outer wall extending between a proximal end and an opposing distal end, the catheter body being characterized by a distal surface and a plane of separation extending longitudinally at the distal end of the catheter; first portions of the outer wall extending circumferentially of the catheter body on one side of the plane of separation; second portions of the outer wall extending circumferentially of the catheter body on the other side of the plane of separation; at least one optical fiber disposed within the catheter body on the one side of the plane of separation, the optical fiber terminating at the distal surface; and the first portions of the catheter body extending distally of the distal surface and forming a tongue having a distal tip and lateral edges diverging proximally from the distal tip into proximity with the plane of separation.

2. The laser catheter recited in Claim 1 wherein the plane of separation contacts the outer wall at opposing points on the distal surface and each of the lateral edges of the tongue extends toward an associated one of the opposing points.

3. The laser catheter recited in Claim 1 wherein the plane of separation is spaced from the axis of the catheter body.

4. The laser catheter recited in Claim 3 further comprising torque means disposed within the catheter body on the other side of the plane of separation for adjusting the radial orientation of the catheter relative to the blood vessel.

5. The laser catheter recited in Claim 4 further comprising indicator means including a radiopaque marker for providing an indication of the angular orientation of the catheter in the blood vessel.

6. The laser catheter recited in Claim 4 further comprising: means for imparting axial twist to the torque wire; and means for limiting the twist of the torque wire.

7. The laser catheter recited in Claim 1 wherein the tongue has flexible characteristics permitting the tongue to be bent back on itself to facilitate fluence measurement at the distal end of the catheter.

8. The laser catheter recited in Claim 1 further comprising means defining a guide wire lumen within the catheter body on the other side of the plane of separation.

9. The laser catheter recited in Claim 8 wherein the guide wire lumen defining means extends into the tongue.

10. A catheter system adapted to be longitudinally and radially positioned within a body conduit, comprising: a catheter body having an axis extending between a proximal end and an opposing distal end; a wire disposed in the catheter body and providing a radiopaque image including a first edge extending generally longitudinally of the catheter; and a marker disposed laterally of the wire and providing a radiopaque image including a second edge which overlaps the first edge when the catheter is in an undesirable radial orientation within the conduit, and which is spaced from the first edge when the catheter is in a desired radial orientation within the conduit.

11. The catheter system recited in Claim 10 wherein the wire is a guidewire extending in the body conduit beyond both the proximal end and the distal end of the catheter.

12. The catheter system recited in Claim 11 wherein the marker in radial cross-section has two lateral edges which define a plane with the guidewire disposed on one side of the plane and the marker disposed on the other side of the plane.

13. The catheter system recited in Claim 10 further comprising torque means operable to rotate the catheter into the desired radial orientation within the conduit.

14. The catheter system recited in Claim 13 wherein the catheter is rotated about the wire in response to operation of the torque means.

15. The catheter system recited in Claim 10 further comprising: means for imparting axial twist to the torque wire to axially rotate the catheter; and means for limiting the amount of twist which can be imparted to the torque wire.

16. The catheter system recited in Claim 10 wherein: the wire has a radiopaque image including a first line; the system includes a radiopaque marker disposed in proximity to the wire and providing a radiopaque image including a second line; and the spacing of the first line relative to the second line provides an indication of the radial orientation of the catheter.

17. A catheter adapted to be disposed in a body conduit, comprising: a catheter body having an axis extending between a proximal section and an opposing distal section of the catheter; torque means connected to the distal section of the catheter body and operable to axially rotate the distal section of the catheter body to achieve a desired angular orientation within the body conduit; the torque means operating over a preferred range of angular displacement; means disposed at the proximal section of the catheter body for imparting axial twist to the torque means; and means for limiting the amount of imparted twist to the preferred range of angular displacement.

18. The catheter recited in Claim 17 further comprising means included in the imparting means for engaging the torque means in the proximal section, the engaging means imparting twist to the torque means with axial movement of the engaging means; and means include in the limiting means for limiting the axial movement of the engaging means.

19. The catheter recited in Claim 18 wherein: the torque means comprises a torque wire having a distal end and a proximal end; portions of the engaging means define a radial slot; and the distal end of the torque wire is disposed in the radial slot.

20. The catheter recited in Claim 17 further comprising: at least one optical fiber having bending limits; and the preferred range of angular displacement is dependent upon the bending limits of the optical fiber.

21. The catheter recited in Claim 20 further comprising a tongue extending axially at the distal end of the catheter body and portions of the tongue defining a guide wire lumen.

22. A laser catheter adapted for use in ablating plaque disposed on an inner surface of a blood vessel, comprising: a catheter body having an axis extending between a proximal end and an opposing distal end of the catheter; at least one laser optical fiber extending to the distal end of the catheter body for producing laser fluence which projects a fluence along a path extending beyond the distal end of the catheter; portions of the catheter body forming a tongue at the distal end of the catheter, the tongue having a first position in the fluence path to protect the blood vessel from the laser fluence; and the tongue having a second position removed from the fluence path to permit measurement of the laser fluence.

23. The laser catheter recited in Claim 22 wherein the laser fibers extend to a distal surface of the catheter and the tongue is characterized by a distal tip and lateral edges which diverge proximally to the distal surface of the catheter.

24. The laser catheter recited in Claim 22 wherein portions of the catheter body and the tongue define a guidewire lumen of the catheter.

25. The laser catheter recited in Claim 22 further comprising torque means for providing the distal end of the catheter with a predetermined radial orientation; and means disposed at the proximal end of the catheter body for imparting twist to the torque means.

26. The laser catheter recited in Claim 23 wherein the distal surface is disposed at an angle to the axis not less than 90°.

27. The laser catheter recited in Claim 22 wherein the laser fibers are disposed in adjacent layers and the fibers in the adjacent layers are spiraled in opposite directions.

28. The laser catheter recited in Claim 25 further comprising means for limiting the extent of the twist imparted to the torque means.

29. A method for axially orienting a catheter within a body conduit, comprising the steps of: providing a first radiopaque marker adapted to form a first image having a first edge; providing a second radiopaque marker adapted to form a second image having a second edge; and twisting the catheter to provide the first edge of the first image and the second edge of the second image with a predetermined spaced relationship indicative of a desired axial orientation of the catheter within the conduit.

30. The method recited in Claim 29 wherein the first providing step includes the step of providing the first marker in the form of a guidewire.

31. The method recited in Claim 30 further comprising the step of providing a torque wire and the twisting step includes the step of twisting the torque wire to provide the first edge and the second edge with the predetermined relationship.

32. The method recited in Claim 29 wherein the catheter is a laser catheter including at least one optical fiber and the second providing step includes the step of providing the second radiopaque marker in the form of a sleeve extending around the optical fibers of the catheter.

33. A method for ablating a lesion disposed in an eccentric location within a blood vessel, comprising: inserting into the blood vessel a guidewire having a longitudinal configuration; advancing the guidewire through the blood vessel and across the eccentric lesion; threading onto the guidewire a laser catheter having a catheter body with an axis extending between a distal section and a proximal section, portions of the catheter body defining a lumen for receiving the guidewire; torquing the catheter about the guidewire to provide the guidewire with a preferred radial orientation relative to the lesion; and arranging a radiopaque marker in the catheter to provide a visual indication when the catheter is in the preferred radial orientation.

34. The method recited in Claim 33 further comprising the steps of: providing the catheter with a tongue having lateral edges which extend proximally outwardly; and during the torquing step advancing the catheter axially to bring the lateral edges of the tongue into contact with the lesion in a camming action which torques the catheter into the preferred orientation.

35. The method recited in Claim 33 further comprising the steps of: providing the catheter with a torque wire; and during the torquing step, twisting the torque wire to torque the catheter into the preferred orientation.

36. A catheter system for ablating a lesion eccentrically located within a blood vessel, comprising: a guidewire extending through the blood vessel and across the lesion; a catheter body having an axis extending between a proximal end and a distal end of the catheter body; at least one optical fiber disposed in the catheter body eccentric of the axis of the catheter body, the optical fiber producing a laser fluence path with extends generally axially of the catheter body; tongue means receiving the guidewire eccentrically of the axis at the distal end of the catheter body, for maintaining the catheter body in coaxial alignment with the blood vessel during axial movement of the catheter body; means for rotating the catheter body about the guidewire to place the catheter body in a preferred radial orientation with the lesion; and radiopaque means for providing a visual indication when the catheter body is in the preferred radial orientation.