IMPROVED LASER-HEATED INTRAVASCULAR CAUTERY CAP

Abstract: Improvements in laser-heated intravascular cautery cap construction include structures for joining the cap (162, 163, 164) and optical fiber assembly (176), and structures for guiding the assembly through a vessel. Furthermore, a catheter guide wire (174) may extend outwardly from the center of the closed end of the cap. The cap may be formed with a central bore (172) therethrough to receive a guidewire (174) in slidable fashion.

Description: IMPROVED LASER-HEATED INTRAVASCULAR CAUTERY CAP Reference to Related Application This application is a continuation-in- art of application serial number 06/650,889, titled Laser Revascularization Device and Method of Operation Thereof, filed September 17, 1984 by Garrett Lee. Background of the Invention The concept of revascularization of vessels occluded by atherosclerotic plaque deposits by the use of a laser-heated cautery cap is described fully in the parent patent application referenced above. Briefly, this technique involves securing a cautery cap to one end of an optical fiber, with the other end of the optical fiber connected to a laser light source. The cautery cap-fiber assembly is dimensioned to be passed through arteries or other vessels, either percutaneously or intraoperatively, and the cap end is advanced to impinge upon an atherosclerotic plaque deposit. The laser light source is then actuated to deliver a pulsed or continuous beam through the optical fiber to the cautery cap, which is heated virtually instantaneously to a temperature sufficient to thermally destroy the plaque in contact with the cap. This process may be reiterated, SUBSTITUTE SHEET and the cap may thus be advanced through the plaque deposit. Alternatively, the laser may be operated continuously to heat the cap as it is drawn through a vessel requiring treatment. As a result, the lumen of the vessel may be reopened to a degree approximating the original fluid carrying capacity of the vessel. Devices known in the prior art for carrying out this process have exhibited some limitations in functionality and reliability. These limitations are categorized as (1) occassional separation of the cap from the fiber assembly during use; (2) problems in guidance and positioning of the cap within vessels; (3) lack of an accurate temperature control method; and (4) lack of preferential directional heating capability. In the prior art, the optical fiber is secured within a sleeve-like jacket extending the length thereof for mechanical support, and the cautery cap comprises a tubular cylindrical member having a closed distal end and an open proximal end. The proximal end is generally both glued and crimped to the outer surface of the jacket of the optical fiber, and a small, closed air space exists between the inner surface of the distal end of the cap and the distal end of the jacket of the optical fiber. It has been found that the optical fiber jacket portion near the cap may not be strong enough or durable enough to provide a reliable connection after undergoing repeated high temperature excursions and under commonly encountered mechanical stresses during clinical use. Failure of the jacket or the bond between the SUBSTITUTE SHEET jacket and the cap would lead to cap separation resulting in a difficult and dangerous situation for the patient and the surgeon. Furthermore, it is quite clear that the cautery cap must direct its thermal energy preferentially to the atherosclerotic deposits, with minimal injury to the adjacent vessel wall. Various guidance devices and assemblies have been developed in the prior art, and are described in the parent patent application referenced above. However, as the revascularization technique is refined and applied to smaller vessels, the requirements for guidance and control of the cap with respect to the vessel wall become more acute. For example, with regard to working within coronary vessels, it should be noted that the lumen of these tortuous vessels often narrows to a ran "g___•e of 0.5-1.0 mm, and that there is a very small margin for error in placement of the cautery cap. Also, it should be noted that the atherosclerotic lesions on the interior surface of the vessel typically are not disposed symmetrically about the axis of the lumen at that location. Indeed, the lesion may be partially or totally eccentric to the axis. Thus it is desirable to provide a preferential directional heating capability to deliver the destructive thermal energy to the lesion, while sparing the adjacent healthy vessel wall. Prior art devices cannot provide this directional control. SUBSTITUTE SHEET Summary of the Present Invention The present invention generally comprises improvements to laser- heated cautery cap constructions, particularly for revascularization procedures in atherosclerotically occluded blood vessels. These improvements are designed (1) to direct the thermal energy preferentially to specific locations on the cautery cap to maximize the energy delivered to the plaque deposits, while protecting the adjacent vessel walls from thermal damage, (2) to increase the guidance and positional control of the cautery cap within the vessel, while permitting revascularization procedures within far smaller vessels; and (3) to monitor and control the cap temperature in use. The improvements also increase the mechanical strength of the cautery cap-optical fiber assembly, so that mechanical failures during revascularization procedures are prevented. Furthermore, the invention provides unique cap configurations and shapes for particular treatment purposes. The cap configuration may be generally tubular and cylindrical, or may be oblate spheroidal with either a blunt or pointed tip. Another cap configuration includes a pair of cylindrical, concentric sidewalls. The inner sidewall may define a bore extending through the cap and adapted to receive a guide wire therethrough for guidance purposes. Alternatively, the cap end wall may close the bore, with the optical fiber secured in the SUBSTITUTE SHEET central bore to heat the end wall and the annular space between the concentric sidewalls employed either for thermal insulation or for use as a flow space to deliver cooling and irrigating fluid to the treatment site. The wide variety of cap configurations are used in various surgical procedures and to accommodate diverse situations in the vessels themselves. To direct the thermal energy more precisely, in the present invention the closed end or sidewall of the cap may be provided with at least one annular portion having a reduced thickness , so that the thermal energy conduction path is restricted and the heated zone is well defined and limited. Thus the physical conformation of the cautery cap acts to deliver the thermal energy to the treatment site, and to protect the adjacent vessel walls from thermal damage. Another feature of the present invention for selectively directing the thermal energy is the provision of a disk inserted into the cap to intercept the laser beam and conduct the resulting heat energy to the periphery of the cap. The disc may be selectively placed along the axis of the cap to preferentially heat the annular portion of the cap contacted by the outer edge of the disc. In accordance with the disc position, the annular heating zone may be adjacent to the tip for the purpose of enlarging the lumen, or may be more medially spaced for the purpose of annealing the vessel wall; e.g., immediately following a balloon angioplasty procedure. In addition, the disc may be configured so that only a portion of the disc periphery is in SUBSTITUTE SHEET contact with the interior of the cap. As a result, the heat energy is conducted only to a portion of the annulus of the cap side wall, directing the energy to a selected angular portion of the annulus with respect to the axis of the cap. Thus eccentric atherosclerotic lesions may be treated effectively and safely. To strengthen the cap/fiber connection, the invention in one embodiment provides a strap, fashioned as an integral portion of the cap, extending from the side wall parallel to the axis of the optical fiber and rearwardly to a ring which is axially spaced rearwardly of the cap side wall. The ring is glued to the fiber jacket at a point which is sufficiently distant from the cap so that it is not subject to heating by the cap. The tensile strength of the strap together with the augmented retention provided by the ring act to provide greater mechanical strength to the cap-jacket bond. This feature prevents accidental loss of the cap from the end of the optical fiber assembly. Another embodiment for strengthening the fiber jacket adjacent to the cap comprises either a stainless steel wire braid or a plurality of filaments wound in spiral fashion about the fiber jacket from the ring or the cap rearwardly. It has been noted in the prior art that tension exerted on the optical fiber jacket can cause stress in the jacket portion to which the cap is joined, resulting in "necking", or diameter reduction in the jacket and possible mechanical failure of the jacket. The wire braid or the spiral SUBSTITUTE SHEET winding of the multiple filaments undergoes diametrical contraction when the jacket begins to stretch under tension. The contraction of the braid or filaments compressively engages the jacket and strengthens the jacket, thus alleviating this failure mode. In addition, a metal spring coil may be drawn over the optical fiber and secured to the proximal end of the cap. The spring coil provides mechanical protection for the fiber and greater rigidity for the assembly, thus increasing the ability to push the instrument through the catheter and blood vessel. The spring coil also functions as a safety tether for the cap, permitting withdrawal of the cap if the fiber breaks or if the cap detaches from the fiber. The guidance of the laser-heated cautery cap may be improved by the provision of a guide wire joined to the closed end of the cap and extending axially and forwardly therefrom. The guide wire may be welded to the outer surface of the end wall of the cap, or formed integrally with the end wall structure, or may extend through a hole drilled in the cap end wall. In all cases, the guide wire is employed by being introduced first into the lumen of the vessel and advanced to the atherosclerotic occlusion. If the occlusion is not complete, the guide wire may be passed through the occlusion to effectively lead the cautery cap into direct impingement with the occlusion. Selection of a cap with a diameter somewhat less than the internal diameter of the normal vessel, together SUBSTITUTE SHEET with the direct positioning of the integral guide wire, limits contact between the cap and the vessel wall during revascularization. The wire can be fastened to the center of the cap, or for certain application can be fastened eccentrically to allow for more precise placement on eccentric lesions. Another structure for guiding the cautery cap within the lumen comprises a guide sleeve secured directly to the sidewall of the cap. The guide sleeve is a cylindrical tube welded to the sidewall of the cap, and a guide wire may be passed through the sleeve in slidable fashion. After the g ~ ~~uide wire is introduced into the vessel and advanced throu * g-•*h the lumen to the atherosclerotic blockage, the guide sleeve-cap assembly with the optical fiber trailing behind may be advanced along the guide wire to the blockage and positioned thereby. The invention also includes several arrangements of interlocking crimped and flared bushings and sleeves for joining the cap structures described above, embodying various combinations of the guidance features, the preferential directional heating features and the mechanical strengthening features, to the end of an optical fiber. Indeed, a salient feature of the invention is that a minimal number of fiber end connection arrangements are required to secure the entire variety of cap structures and sizes to the fiber, thus facilitating efficient, low cost manufacturing of the devices. In one embodiment, an insulative ceramic bushing is secured SUBSTITUTE SHEET about an inner sleeve which is in turn secured about the jacket of the fiber end. An outer bushing is secured about the ceramic bushing, the outer bushing having a standardized diameter. The proximal open end of any cap of the invention may be slidably engaged about the outer bushing and crimped in place. Another embodiment includes a bushing which may be secured about the rear portion of the cautery cap sidewall. In this embodiment the sidewall is elongated axially, and the bushing is secured about the rear (proximal) portion of the cap to avoid overheating by the thermal energy delivered to the forward (distal) end of the cap. The bushing is provided to position the cap within the end opening of a guide catheter passage with annular spacing between the cap and the catheter. The guide catheter positions the cap centrally within the vessel, and the distal end of the cap extends from the catheter passage to impinge on the atherosclerotic blockage. The annular spacing created by the bushing insulates the catheter from the high temperature of the distal end of the cap, and centers the cap within the vessel. The cap temperature control system of the invention includes a laser disposed to deliver a beam of coherent light through a beam splitter and into the optical fiber extending to the cap. Thermal radiation (infrared light) is conducted back along the fiber to the beam splitter, and thence to a filter that blocks the laser wavelength, so that only the thermal radiation SUBSTITUTE SHEET passes therethrough. The thermal radiation strikes a photodiode which generates a voltage signal proportional to the temperature of the cap. The signal is amplified and buffered, and used to drive a temperature display, and to control the laser output to produce cap temperatures within a selected range. SUBSTITUTE SHEET 11 Brief Description of the Drawing Figure 1 is a schematic representation of the operating system of the laser-heated cautery cap, including the cap operating temperature control system. Figure 2 is a cross-sectional elevation of a typical laser-heated cautery cap assembly known in the prior art. Figure 3 is a side elevation of one embodiment of the present invention, comprising a laser-heated cautery cap "configured to deliver thermal energy primarily axially and forwardly of the cap. Figure 4 is a side elevation of another embodiment of the present invention, comprising a laser-heated cautery cap configured to deliver thermal energy primarily axially and forwardly of the cap, and having a higher flash temperature. Figure 5 is a side elevation of a further laser-heated cautery cap embodiment of the present invention, comprising an oval cap configured to deliver thermal energy primarily axially and forwardly of the cap in controlled, annular temperature bands. SUBSTITUTE SHEET Figure 6 is a side elevation of another oval laser-heated cautery cap embodiment of the present invention, including a disc disposed in the cap and oriented generally transversely in the laser beam path laser. Figure 7 is a side elevation of an additional embodiment of the present invention, comprising a laser-heated cautery cap having an intermediate disc disposed to deliver thermal energy primarily radially and laterally with respect to the axis of the cap. Figure 8 is a side elevation of an additional embodiment of the present invention, comprising a laser-heated cautery cap having an intermediate disc disposed to deliver thermal energy primarily radially and laterally to an angular segment of the cap with respect to the axis thereof. Figure 9 is a cross-sectional elevation taken along line 9-9 of Figure 8. Figure 10 is a side elevation of an additional embodiment of the present invention, comprising a laser-heated cautery cap having an intermediate disc disposed to deliver thermal energy primarily radially and laterally to an angular segment of a medial annular portion of the cap. SUBSTITUTE SHEET Figure 11 is a cross-sectional elevation taken along line 11-11 of Figure 10. Figure 12 is a side elevation of an additional embodiment of the present invention, comprising a laser-heated cautery cap having a self- guiding tip and an intermediate disc disposed to deliver thermal energy primarily radially and laterally to an angular segment of the cap with respect to the axis thereof. Figure 13 is a side elevation of a variation of the device of Figure 12, in which the intermediate disc is configured to deliver thermal energy primarily radially and laterally to an angular segment of an annular portion of the cap. Figure 14 is a cross-sectional elevation taken along line 14-14 of Figure 13. Figure 15 is a side elevation of a laser-heated cautery cap including an augmented mechanical bond to the jacket of the optical fiber joined thereto. SUBSTITUTE SHEET Figure 16 is a side elevation of a laser-heated cautery cap device, including a wound filament reinforcement of the jacket of the fiber joined thereto. Figure 17 is a side elevation of a laser-heated cautery cap device, including a bi-directionally wound filament reinforcement of the jacket of the optical fiber joined thereto. Figure 18 is a cross-sectional side elevation of one connection arrangement for joining a laser-heated cautery cap to an optical fiber termination. Figure 19 is an enlarged, fragmentary cross-sectional side elevation of the connection arrangement of Figure 18. Figure 20 is an enlarged, fragmentary cross-sectional side elevation of another connection arrangement for joining a laser-heated cautery cap and the end of an optical fiber. Figure 21 is a cross -sectional side elevation of a spring coil reinforcement joined about an optical fiber in accordance with the present invention. SUBSTITUTE SHEET Figure 22 is another embodiment of a cross-sectional side elevation of a spring coil reinforcement joined about an optical fiber in accordance with the present invention. Figure 23 is a cross-sectional side elevation of a concentric double- walled laser-heated cautery cap in accordance with the present invention. Figure 24 is a cross-sectional side elevation of a further embodiment of the device shown in Figure 23. Figure 25 is a side elevation of a laser-heated cautery cap assembly, including a guide sleeve joined directly to the cap and adapted to engage an arterial guide wire. Figure 26 is a side elevation of a laser-heated cautery cap assembly, including an arterial guide wire integrally joined to the outer end surface of an oval cap assembly and extending distally therefrom. Figure 27 is a side elevation of a laser-heated cautery cap assembly, including an arterial guide wire integrally joined to the outer end surface of a blunt end cap assembly and extending distally therefrom. SUBSTITUTE SHEET Figure 28 is a cross-sectional side elevation of a laser-heated cautery cap assembly received within an arterial catheter and spaced therein by a bushing member secured about the cautery cap. Figure 29 is a cross-sectional elevation taken along line 29-29 of Figure 28. Figure 30 is a cross-sectional side elevation of a laser-heated cautery cap assembly in which the cap extends concentrically about a central guide wire. Figure 31 is an enlarged, fragmentary cross-sectional side elevation of the device of Figure 30, showing the guide wire and inflatable balloon of this embodiment as well as the structure of the distal end of the laser- heated cautery cap. Figure 32 is a cross-sectional side elevation of a laser-heated cautery cap disposed concentrically about a guide wire and including an integral bushing extending thereabout. SUBSTITUTE SHEET Figure 33 is a cross-sectional end view taken along line 33-33 of Figure 32. Figure 34 is a cross-sectional side elevation of a further emodiment of the invention in which a directionally preferentially heated cap is secured to an optical fiber disposed within a sleeve, the sleeve extending from an arterial catheter, and a balloon mounted eccentrically on the sleeve and disposed to be inflated to urge the heated portion of the cap into engagement with an atherosclerotic lesion. SUBSTITUTE SHEET Description of the Preferred Embodiment The present invention generally comprises an improved laser-heated cautery cap particularly adapted for use in revascularization of vessels which are partially or totally occluded by deposits of atherosclerotic plaque. With regard to Figure 2, a typical laser-heated cautery cap assembly known in the prior art includes a light-conducting optical fiber 16 which is surrounded by a sleeve-like jacket 17 to impart greater mechanical (particularly bending stress) strength to the fiber. The diameter of the fiber 16 is typically in the range of 100-400 microns, and the thickness of the jacket is typically 50-200 microns. A cautery cap 18 is joined to the distal end of the jacket 17, and the proximal end 19 of the optical fiber is connected to a controlled, high intensity light source such as a laser. The typical laser-heated cautery cap 18 comprises a tubular cylindrical member formed of high-temperature alloy. The proximal portion of the cylindrical sidewall 19 is crimped (22) to the jacket 17, and an annular glue line 23 is also provided to seal the cap to the optical fiber assembly. The closed, distal end wall 21 of the cap is spaced slightly from the distal end of the fiber, and a small enclosed chamber 24 is defined by the interior surfaces of the cap and the distal end surface of the jacket. Several deficiencies have been noted in the typical prior art laser- heated cautery cap. One serious problem is that there is no effective means SUBSTITUTE SHEET for ascertaining the actual temperature of the laser-heated cautery cap during use. Relatively precise control of the temperature of the cap surface during clinical use is very important because the biological effect in tissue varies greatly as a function of the cap temperature. Generally, in the prior art each cap is thermally calibrated prior to use by measuring the power output of the laser and measuring the resulting temperature profile of the cap surface in a known ambient environment such as air, water, or tissue. The subsequent temperature in clinical use can be inferred approximately from the power input with a wide range. However, the actual operating circumstances vary widely within a vessel during clinical use. The presence of blood or saline solution, the rate of cap movement through the vessel, the different compositions of atherosclerotic lesions, and the degree of tissue contact all affect the rate of heat loss from the cap surface and thus its temperature. Thus the actual operating temperature of prior art laser-heated cautery cap devices is generally known only within a broad range of error. At elevated temperatures (200°C to 1000°C) a large deviation from the predicted temperature can occur in as little as 0.1 second and can cause unintended tissue effects in far less than one second. To overcome this problem, the present invention provides a laser control system which not only detects and displays the actual temperature of the hottest portion of the cap, but also maintains a desired operating SUBSTITUTE SHEET temperature. With regard to Figure 1, the system generally includes a laser 41 disposed to deliver a beam of coherent light through a beam splitter 42 to a lens 43. The lens 43 focuses the beam and directs it into the proximal end of a flexible optical fiber assembly 44. At the distal end of the optical fiber 44 is a laser-heated cautery cap 46, the various features of which are described in the specification below. Generally speaking, the laser beam heats the cap 46 to carry out revascularization procedures, and the heated cap also emits infrared radiation that is a function of its temperature. The thermal radiation from the inside surface of the cap is conducted back along the fiber 44, through the lens 43 to the beam splitter 42. A portion of the thermal radiation, together with a portion of the original laser beam, is directed by the beam splitter to a filter 47. The filter 47 selectively blocks radiation at the wavelength of the laser, so that only the thermal radation from the cap 46 passes therethrough. The thermal radiation strikes a photodetector 48, comprising a light sensitive photodiode 49 connected in series between positive power and a dropping resistor 51 to ground. It may be appreciated that as the thermal radiation drives the photodiode toward conduction, the voltage on the signal line 50 rises. The signal line 50 is connected to a differential amplifier 52 configured as a current to voltage amplifier and signal buffer. A feedback loop 53 to the negative input includes a manually adjustable resistance to set SUBSTITUTE SHEET the gain and control the signal level. The buffered signal, which comprises a voltage analog of the temperature of the cap 46, is fed to a signal buss 54. One device connected to the buss 54 is a temperature display 60 which indicates the operating temperature of the cap 46. The display 60 may comprise a voltmeter calibrated to indicate the cap temperature to the surgical team using the cap device. Also receiving the temperature signal from the buss 54 is a threshold detector 56 comprised primarily of a differential amplifier 57. The negative input to the amplifier 57 is a voltage level determined by potentiometer 58 connected between the positive power source and ground. The output line 59 of the differential amplifier 57 is connected to an alarm system 61. It may be appreciated that the voltage level set by the potentiometer 58 determines the signal voltage required to switch on the amplifier 57. Thus the potentiometer is used to selectively set the maximum safe temperature for cap operation. When the maximum temperature is exceeded, the resulting signal on line 59 actuates the alarm system 61 to apprise the surgeon of danger. The alarm system 61 may also include an emergency shutoff relay 62 to immediately cease operation of the laser. The temperature of the laser-heated cautery cap 46 can also be indicated by a variable tone generator 63. A voltage to frequency converter 64 receives the signal from the buss 54, and is connected to drive SUBSTITUTE SHEET a speaker 66. As the temperature of the cap 46 varies, the tone of the output of the speaker 66 varies also, providing an audible indication to the surgeon who may be too busy to observe the visual display 60. The invention also includes a laser control circuit 67 which receives the temperature signal from buss 54. The circuit 67 controls the power to the laser 41, and it uses the temperature signal to automatically adjust the laser power to maintain the desired cap operating temperature. In discussing the various embodiments of the laser-heated cautery cap of the present invention, three different modes of heating the cap are mentioned, each having different clinical applications. The flash mode of heating is designed to heat the working surface of the cap to a preset temperature, generally between 400°C and 1000°C, for a very brief time, generally less than a second. The continuous high temperature, or "hot mode" of heating is designed to maintain the working surface within a predetermined, narrow temperature range within a broader span from approximately 200° C to 400°C, over a longer time period (between one and ten seconds) while the cap is moved through tissue. The continuous low temperature, or "warm mode" is designed to maintain the working surface within a predetermined temperature range below 200° C over one to ten seconds as the cap is moved through tissue. The control system disclosed above is designed to carry out these heating modes. .SUBSTITUTE SHEET In prior art laser-heated cautery cap designs, there has been a trade¬ off among three desirable properties: (1) providing a beam target portion of the cap sufficiently thick to prevent burnthrough and to promote uniform heat conduction to the larger working surface of the cap; (2) having the periphery and side walls of the cap sufficiently thin to restrict heat conduction to the vessel wall and rearwardly to the junction with the fiber jacket; and (3) using a thermal mass of the working portion of the cap sufficiently low to permit very rapid heating and cooling of the working portion. The laser-heated cautery cap embodiments of the present invention are generally designed to maximize the three properties noted above by utilizing two basic design principles: reducing thermal mass wherever possible while maintaining mechanical strength, and isolating the working portion of the cap from the remainder of the cap by interposing restriction areas having minimal possible thickness to reduce heat conduction. There are numerous specific configurations based on these principles for use in diverse clinical procedures and to accommodate diverse vessel shapes and plaque materials. One embodiment of the present invention, designed to control and direct the flow of thermal energy to the point of treatment and away from the vessel wall, is shown in Figure 3. (In the following descriptions the same reference numerals are used to indicate common features of different SUBSTITUTE SHEET embodiments.) It comprises a laser-heated cautery cap 67 having a generally cylindrical sidewall 68 joined to the jacket 17 of an optical fiber core 16 as described in the following specification. The distal end wall 70 of the cap extends generally transverse to the axis of the sidewall 68 and is formed integrally therewith. The distal end wall 70 is substantially thicker in the central portion than the thin outer annulus 71 at the junction with the sidewall. This feature limits thermal conduction to the sidewall to prevent dangerous heating of the sidewall. Furthermore, the annular sidewall portion 69 adjacent to the end wall 70 is substantially thinner than the remainder of the sidewall which is in contact with the jacket 17. The thinner annulus 69 further restricts the thermal conductivity path from the end wall, and prevents overheating of the sidewall portion in contact with the jacket. Thus the thermal energy is directed toward the central portion of the end wall, which is the portion of this embodiment of the cap generally used to contact and destroy the atherosclerotic plaque. A further embodiment of the cap of the present invention, shown in Figure 4, also includes a laser-heated cautery cap 67' having a generally cylindrical sidewall 68' joined to the jacket 17 of an optical fiber core 16. The annular sidewall portion 69' adjacent to the end wall 74 is substantially thinner than the remainder of the sidewall which is in contact with the jacket 17. The thinner annulus 69 restricts the thermal conductivity path from the end wall, preventing overheating of the sidewall SUBSTITUTE SHEET portion in contact with the jacket. A salient feature is the configuration of the end wall 74, which comprises a a thin panel dished convexly outwardly from the end of the cap. The thin end wall 74 not only limits thermal conduction to the sidewall, it also presents a minimal thermal mass to be heated by the incident laser beam. As a result, this embodiment is designed to provide a high flash temperature. The convex end wall also serves to provide a small degree of self-guiding capability, as the convex end tends to direct the cap through the existing lumen of a vessel. Another embodiment of the cap which is designed to separate heated, working surfaces from the remainder of the cap is shown in Figure 5. It comprises a smoothly curving, oval cap 76 joined to the jacket 77 of an optical fiber 78 at the distal end thereof by any one of the several means described below. The cap is formed in a quasi-ellipsoidal, or prolate configuration, with the major axis of the ellipsoid generally coextensive with the axis of the fiber 78, and the minor axis extending farther than the diameter of the jacket 77. The end wall 79 tapers to a smoothly curved, rounded tip. A medial annular portion 81 of the cap side wall extends from the tip portion 79 in smoothly contoured fashion to the proximal annular portion which flares from a junction with the jacket 77 to the medial portion 81. The oval cap 76 defines within a closed chamber 83 having a distal beam target surface 84 extending generally transverse to the fiber axis and disposed to receive the beam therealong. The beam heats the SUBSTITUTE SHEET surface 84, and this thermal energy is conducted to the working surface 79 of the cap. It may be noted that the internal surface 79 converges at its periphery with the external surface 79, defining an annulus 86 having very thin side wall thickness. This reduced thickness annulus restricts the thermal conduction of the side wall rearwardly of the annulus 86, thus reducing side wall heating during operation of the invention. The interior chamber may be provided with a series of annular steps to define one or more thermal restriction annulus 87 to further reduce heating of the side wall portions in contact with the vessel wall. It should be noted that the tapered tip 79 of the cap 76 provides a self -guiding characteristic to the cap, so that it may be used, for example, to traverse and revascularize a vessel having a partially occluded lumen. Although Figure 5 suggests visually that the cap 76 is greater in diameter than caps shown in Figures 3 and 4, this is not necessarily the case. Indeed, the jacket and fiber 77 and 78 may be substantially smaller than their counterparts 17 andl6, and the caps may have similar diameters. To further the concept of preferentially heating portions of the laser- heated cautery cap while restricting heating of the remainder of the cap, the present invention provides a metallic disc disposed inside the cap between the end of the optical fiber and the closed end of the cap. The disk serves two purposes: (1) it intercepts the laser beam and conducts the SUBSTITUTE SHEET 27 resulting heat preferentially to the portions of the cap in contact with the disk, and (2) it provides a relatively stable and predictable thermal mass isolated from tissue contact which allows more accurate measurement and control of cap temperature. With regard to Figure 6, one embodiment 5 includes an oval cap 76 joined to the jacket of an optical fiber 78, as described previously. Rather than having the laser beam strike the interior surface of the cap tip 79, a disk 91 is placed in the beam path, transverse to the beam and disposed within the chamber 83 adjacent to the tip 79. The disk, and all disks mentioned hereafter are preferably formed of tantalum, 0 a material which is durable, machinable, with a high melting point and high thermal conductivity. However, other similar materials may be selected by those skilled in the art. The entire peripheral edge of the disk 91 impinges on the inner surface of the chamber 83; it may be appreciated that when the disk 91 is heated by the laser beam, the heat is conducted by the disk to 5 the portion of the cap in contact therewith. Therefore an annular zone 94 is heated by the disk, the zone extending adjacent to and rearwardly of the tip 79. The embodiment also provides a thermal restriction annulus 92, between the disk and the tip 79, to prevent high temperatures at the tip. Another thermal restriction annulus 93, disposed rearwardly of the disk 0 91, prevents excessive heat conduction to the medial side wall portion of the cap. In this embodiment the central face of the tip 79 is relatively cool, and the heated working surface is an annular portion just rearward of the " SUBSTITUTE SHEET tip 79. Thus this embodiment may be used, e.g., to guide itself through a ' partially open lumen, and to enlarge that lumen as it is traversed. As shown in Figure 7, a further embodiment of the oval cap 76 includes a disk 96 disposed within the chamber 83 and located in the beam path at a medial portion of the cap. The heat generated by the disk is conducted to the medial side wall portion which it contacts, creating a heated annular zone 97. Rather than restrict thermal conduction to the cap side wall and to the vessel wall, this embodiment directs the thermal energv to the side wall, particularly for the purpose of "annealing" or smoothing the surface of the vessel after procedures such as balloon angioplastv or after a series of cautery cap bums that leave ragged edges or tears in the tissue. Although annealing is a metallurgical concept, it is defined herein as a process of smoothing the vessel walls using a moderately heated cap. When tissue is heated to approximately 60°C, protein denaturing occurs, and there is heat-shrinkage of tissue and cross-linking of tissue proteins. In the vascular wall, tissue adhesion results from collagen denaturation in the medial and adventitial walls of the vessel, as well as fibrin polymerization. Microscopic tears within the vascular wall and disruptions within the atheromatous plaque can be fused and welded by annealing with a laser heated cap. Annealing with a warm cap can also make the luminal surface smooth by fusing the roughened and shaggy surface often caused by balloon angioplasty. Some intraluminal (intimal) SUBSTITUTE SHEET flaps can be vaporized by heating the tissue to higher than 100°C. A smooth intraluminal surface reduces turbulent blood flow in the vessel and consequently decreases the abrupt reclosure rate and chronic restenosis rate that are found following the conventional balloon angioplasty procedure. In the present invention the concept of preferential directional heating of the cap has been extended to include heating of portions of an annulus of the cap; i.e., heating of eccentric portions of the cap. With regard to Figures 8 and 9, a further embodiment uses the oval cap 76, as described in Figure 6. However, this embodiment includes a disk 101 disposed in the chamber 83 at a position adjacent to and rearwardly of the tip 79. The disk 101 is not circular; rather, it is provided with a chordal cutaway 102, so that the portion 1.02 of the periphery of the disk 101 is spaced apart from contact with the cap. It may be appreciated that the heat generated by the disk is conducted to the cap side wall with which it is in contact. As a result, this embodiment features a heated zone 94 which is a portion of an annulus, with the zone 103 remaining relatively cool. This eccentrically heated zone is used to treat atherosclerotic lesions disposed to one side of the vessel lumen. The cap-fiber assembly may be rotated about the axis of the fiber 78 to orient the heated zone 94 to impinge on the lesion, while the remaining, healthy vessel wall in contact with the cap is not damaged. SUBSTITUTE SHEET Directional, eccentric heating of the cap is also usefully applied to an annealing cap construction. For example, as shown in Figures 10 and 11, the annealing cap of Figure 7 is modified by the use of a disk 104 within the cap chamber 83, the disk 104 including a chordal cutaway 106. The peripheral edge portions of the disk in contact with the cap side wall determine that a medial zone 97 is heated by the disk, and that a portion 107 of the medial area is maintained cool. This directional, eccentrically heated zone may be used to anneal one side of a vessel wall, leaving the remainder of the vessel wall unperturbed. The cap construction shown in Figures 12-14 is similar to the cap of Figures 6, 8 and 9, with the addition of a more pointed tip 108. The pointed tip facilitates self-guiding of the cap through a partially closed lumen, and the remaining features function as described previously. Another cap construction of the present invention which is adapted to control and direct the flow of heat to the side wall is shown in Figure 20. A laser-heated cautery cap (any of the embodiments shown herein) having a side wall 144 is provided with an inner sleeve 146 disposed concentrically therein. A tantalum disk 147 is secured in the distal end opening of the sleeve 146, the disk being disposed to receive the laser beam from the optical fiber 16. An annular spacing bushing 148 is secured about the proximal end of the sleeve 146 and within the side wall 144 to secure the sleeve and disk. The annular space between the sleeve and cap side wall SUBSTITUTE SHEET may be filled with ceramic insulative fill 149 or used as an air gap. This construction permits the disk to be operated at a relatively high temperature (i.e., above 400°C), and the tortuous thermal conduction path to the side wall creates a high temperature differential and a relatively warm but not hot side wall. The high operating temperature of the disk increases the intensity and decreases the wavelength of the retroradiation from the disk to the sensor 48 (Figure 1), thereby increasing the reliability and sensitivity of the measurement of the cap temperatureat lower temperatures. The present invention also includes structures to strengthen the mechanical bond between the laser-heated cautery cap and the optical fiber which heats the cap. As noted above with regard to the prior art cap of Figure 2, the heat generated by the laser pulse striking the end wall 21 is partially conducted to the sidewall 19, resulting in heating of the distal end portion of the jacket 17 and weakening of the jacket. The jacket is generally formed of a biologically inert plastic substance which is weakened by heating. Considering the small diameter of the jacket, it does not possess great tensile strength. Indeed, the jacket is usually not strongly bonded to the fiber core, and tension on the jacket may cause it to stretch independently of the fiber core. Under tension or heating it tends to "neck down" and become thinner, further weakening the jacket and causing rapid failure. SUBS r 5-r i *»τ *υ • ** ε SHEE Heating of the sidewall is also deleterious in that the sidewall may be adjacent to the interior surface of the vessel, and thermal damage to the vessel wall may occur. Furthermore, the crimp junction 22 with the jacket tends to weaken the jacket at that point, further exacerbating the thermal damage to the end of the jacket. As a result, the tensile and bending stresses applied to the device during use within a vessel may cause the cap to separate from the optical fiber assembly. The potential for separation of the cap from the optical fiber assembly is further heightened by thermal pressure effects within the chamber 24. It may be appreciated that when a cap is heated by a laser pulse (to near 1000°C), the gas within the chamber is also heated to high temperature, creating a high pressure therein. If there is a flaw in the glue line or a small hole in the medal cap, some of this gas will be forced out of the chamber. When the cap cools and the gas in the chamber cools with it, a partial vacuum will be created within the chamber. Given the liquid environment is which the device operates, some liquid or vapor will likely be drawn into the chamber 24 to fill the partial vacuum. Subsequent laser pulses can heat the liquid or vapor and create a sufficient overpressure to explosively separate the cap from the optical fiber assembly. With regard to Figure 15, one embodiment of the present invention is designed to strengthen the bond between the cautery cap and the optical fiber assembly to prevent detachment. The embodiment includes a laser- SUBSTITUTΞ SHEET 3 heated cautery cap 26 having a cylindrical sidewall 27 and a closed distal end wall 28. The sidewall 27 is glued to the distal end portion of the jacket 17, as explained above. A salient feature is the provision of a strap 29 extending proximally (rearwardly) from the sidewall 27 and parallel to the axis of the optical fiber assembly. The strap 29 comprises a narrow web of material, and is preferably formed integrally with the cap 26. Joined to the proximal end of the strap 29 is a ring 31, also integrally formed therewith and adapted to be bonded to the jacket 17. It should be noted that the ring 31 provides an augmented mechanical connection to the jacket in addition to the connection of the cap itself to the jacket. The narrow strap 29 exhibits high tensile strength but provides a poor thermal conduction path, so that the ring 31 is joined to a portion of the jacket which does not undergo substantial heating by the operation of the laser-heated cautery cap. Thus even though the connection between the cap 26 and the jacket may weaken somewhat during operation, the ring 31 and the strap 29 will retain the cap-optical fiber assembly intact. The use of a strap and ring to strengthen the bonding of a laser-heated cautery cap device to an optical fiber can be extended to other cap constructions, as described below and shown for example in Figure 18. Even with the provision of the augmented mechanical connection of Figure 15, the cautery cap-optical fiber assembly can fail under tension due to the fact that the jacket itself can stretch and break, as described above. SUBSTITUTE SHEET With regard to Figures 16 and 17, a further embodiment of the invention provides a band 32 of high tensile strength filaments wrapped helically about the distal end portion of the jacket and extending proximally several inches therefrom. As shown in Figure 17, a second band 33 of filaments may be wrapped in the opposite helical direction to further strengthen the jacket. Alternatively, a braided wire sleeve of stainless steel wire or the like may be secured about the jacket. The distal ends of the bands (or braided sleeve) are secured within the ring 31, or may be retained within the crimp and glue connection 22 and 23 of a typical laser-heated cautery cap. The bands of filaments or braided sleeve act to distribute tensile loading created by the cap along a longer portion of the jacket, to alleviate localized failures. Furthermore, the helical wrap or braided configuration acts intrinsically under tension to decrease in diameter, thus compressing the jacket radially and increasing its frictional engagement with the core. The tensile load is thus transferred to the fiber core, which generally exhibits greater tensile strength than the jacket. As a result of these synergistic effects, the amount of stretch and slip of the jacket along the core is limited, and the strength of the cautery cap-optical fiber connection is dramatically increased. Another aspect of the present invention is the provision of structures to guide the laser-heated cautery cap within the blood vessel, and to maximize the effect on the atherosclerotic lesions while minimizing anv SUBSTITUTE SHEET deleterious effect on the vessel wall. As shown in Figure 25, this embodiment is adapted to improve the precision with which the laser- heated cautery cap is positioned within the vessel. As noted previously, a major problem in using the typical laser-heated cautery cap in blood vessels is perforation or thermal damage to the vessel wall due to the fact that the cap cannot be precisely positioned in the vessel to keep it from contacting the vessel wall. The cautery cap may be adapted for use with a prior art vessel guide wire by providing a guide sleeve 36 secured directly to the cap. Although the guide sleeve 36 is shown secured to a cap construction 26, it may also be used in conjunction with other cap embodiments herein or with prior art constructions as shown in Figure 2. The guide sleeve 36 comprises a cylindrical metal tube aligned parallel with the cap and welded thereto at weld points 37. A notch 38 is provided in the outer surface of the tube diametrically opposite the cap to facilitate access to the weld points. Extending between the distal end of the cap 26 and the distal end of the guide sleeve 36 is a gap 35. The gap 35 is several millimeters in length, and is provided to establish a thermal conduction break between the hot tip and the sleeve. The sleeve 36 includes an inner bore which is dimensioned to receive a typical prior art catheter guide wire 39 in freely translating fashion. The flexible guide wire may be inserted into the vessel and advanced to the area of atherosclerotic occlusion, and extended through that area if the occlusion SUBSTITUTE SHEET is not complete/ The cap-optical fiber assembly of Figure. 25 is then slidably advanced along the guide wire 39 to the atherosclerotic deposits, and employed to remove the deposits. It may be appreciated that the cap- optical fiber assembly may be rotated about the guide wire 39 to position the cap with respect to both the vessel wall and the atherosclerotic deposits. The present invention also provides an alternative construction for making use of a guide wire to precisely position the cautery cap at the site of atherosclerotic plaque occlusions. This feature generally involves the use of a guide wire welded or otherwise secured to the distal end wall of the cap and extending distally therefrom. With ' regard to Figure 26, this alternative embodiment includes a laser-heated cautery cap 76, similar to the embodiments of Figurel2. The proximal portion of the side wall is secured to the jacket of the optical fiber 16 as described previously. The extended tip 108 is provided with a central bore 111 dimensioned to receive a tapered wire 112 having a bead 113 welded to the inner end thereof. The wire is pulled through the bore tightly so that the taper creates a press fit in the bore as the weld bead impinges on the inside face of the cap. The bead may then be tack welded to the inside of the cap, although the press fit connection is generally sufficient. An outer spring coil 114 of a typical flexible guide wire is pulled over the tapered wire and secured by a weld bead 116 to provide resilience and flexibility. SUBSTITUTE SHEET It may be appreciated that the guide wire-spring coil assembly 112- 114, termed a unicom guide wire, extends in advance of the cap itself, and that the assembly has the flexibility and strength to be pushed through a narrowed lumen, and that it will follow a tortuous path. The guide assembly 112-114 thus leads the cap through constrictions and bends of a typical blood vessel. The unicorn guide wire may be applied to any of the laser-heated cautery cap constructions of the present invention. For example, shown in Figure 27 is the blunt-nose cap configuration generally shown in Figure 3, with the added modification of a unicorn guide wire assembly. The end wall 70 is provided with a central bore 118 dimensioned to receive a tapered wire 119 having a bead 121 welded to the inner end thereof. As before, the wire is pulled through the bore tightly so that the taper creates a press fit in the bore as the weld bead impinges on the inside face of the cap. The bead may then be tack welded to the inside of the cap. An outer spring coil 122 of a typical flexible guide wire is pulled over the tapered wire and secured by a bead weld 116 to provide resilience and flexibility. It may be noted that the overall diameter of the assembly shown in Figure 27 is less than the diameter of the cap-guide sleeve of Figure 25 or the unicom guide-cap assembly of Figure 26, so that the embodiment of Figure 27 may be used in smaller blood vessels. SUBSTITUTE SHEET In the embodiments of Figures 26 and 27, the unicom guide wire assemblies are shown extending generally axially from the end wall of the respective cautery cap. However, it may be advantageous to position the tapered wire eccentrically with respect to the axis of the cap. This approach permits the treatment of an eccentric lesion in the vessel, and also permits the cap-fiber assembly to be rotated about the axis of the post to sweep a volume greater than volume of the cap itself; e.g., to create a re¬ opened lumen greater in diameter than the diameter of the cap. A salient feature of the present invention concerns the manner in which the laser-heated cautery cap, and in particular the end wall and side wall assembly, is joined to the optical fiber. A unique aspect of the invention in the provision of a standardized arrangement for connecting cap structures to mounting assemblies secured to the ends of optical fibers, so that the economies of production and assembly which derive from standardized parts are realized in this art. With regard to Figure 18, one embodiment featuring such a concept includes a laser-heated cautery cap 126 having a transverse end wall 127 and a cylindrical side wall 128 extending therefrom. The cap 126 is joined to a the jacket 17 of the end of an optical fiber 16, as described in Figure 15. That is, a strap 29 extends longitudinally and rearwardly from the end of the optical fiber, and is integrally joined to a ring 31 secured about the fiber jacket. Also, a helical SUBSTITUTE SHEET reinforcing filament wrap 32 is secured about the jacket end portion by the ring 31, as also shown in Figure 16. A unique feature of this embodiment is that the strap 29 extends not to a cap, but to a sleeve 130 secured about the end of the optical fiber. The sleeve 130 extends distally from the fiber end, and terminates in a flared end 131 through which the laser beam is directed toward the inner surface of the end wall 127. A ceramic or metal bushing 133 is secured about the outer end of the sleeve 130, and is held in place by the flared end 131 as well as by high temperature adhesive or the like. The flare 131 prevents a failure mode in which the fiber end pulls out and free of the cap, an " occurrence having potentially disastrous consequences. The bushing 133 has a standardized outer diameter which permits any of a variety of cap configurations to be secured thereto. For example, the cap 126 may be installed on the assembly by inserting the bushing 133 into the proximal end opening of the side wall. The components are dimensioned to form a press fit, and the proximal edge 132 of the side wall 128 is crimped over the bushing to join the cap permanently to the assembly. A bead of adhesive or sealant may be placed about the crimped edge 132 to seal the assembly. It should be noted that any cap having a proximal end opening substantially equal in diameter to the bushing 133 may be secured to the connector arrangement of Figure 18. Any of the cap configuration SUBSTITUTE SHEET embodiments of Figures 3-17, 26, and 27 may be adapted to fit onto the bushing 133, so that a common fiber termination may suffice for a wide range of revascularization tools. A similar form of standardized fiber end connection, shown in Figure 19, also includes a sleeve 130 secured about the end portion of the fiber jacket 17, with a flared distal end 131 extending beyond the end of the fiber 16. In this embodiment a ceramic insulating bushing 136 is secured about the sleeve 130 and is spaced rearwardly of the flared end 131. An inner bushing 137 is press fit about the ceramic bushing 136, with the proximal edge 138 crimped over the proximal edge of the bushing. The bushing 137 extends distally approximately the same extent as the flared end 131. A high temperature ceramic filling material 139 is disposed within the annular spaces between the bushing 137 and the sleeve 130 to join those two opposed members and form a thermally insulated bond therebetween. The crimped edge 138 reinforces that bond and prevents cap separation under high tensile loads. The bushing 137 presents a smooth outer annular surface of standardized diameter to which may be joined the entire variety of cap configurations described herein. A generalized cylindrical cap sidewall 141 is secured about the bushing 137 by press fitting the two components. The proximal edge 142 of the side wall is then crimped about the proximal SUBSTSTUTE SHEET edge of the bushing to further reinforce the tensile strength of the bond. Any cap may be installed in this fashion. Another facet of the invention is the provision of constructions which reinforce the optical fiber for use like an arterial catheter, but which are far smaller in diameter than such devices. As shown in Figure 21, it includes a standard fiber end connection in accordance with the invention, including a retaining ring 31 secured about the fiber end portion and joined to a strap 29 extending to a cautery cap, as shown also in Figure 16. In this embodiment a fine metal spring coil 151 is drawn over the jacket of the optical fiber. The coil 151 provides mechanical protection for the fiber, provides greater rigidity to enable a small fiber to be pushed more easily through a catheter and blood vessel, and also provides a safety tether if the fiber breaks or if the cap separates from the fiber connection. The coil 151 is held in place by an inner bushing 152 glued to the fiber jacket, and an outer bushing press fit thereabout and abutting the proximal end of the coil. At the distal end, a bushing 154 is glued about the ring 31, and a sleeve 156 is press fit about the bushing 154. The sleeve 156 overhangs the distal end of the coil, securing it to the cap connector structure. Thus in case of breakage of the fiber the coil is connected directly to the cap for easy withdrawal. A strap 157 is disposed longitudinally between the coil and the fiber jacket, and extends between the two bushings 154 and 152. Indeed, the two bushings are grooved to SUBSTITUTE SHEET receive the strap thereunder, the strap being secured by bead welds 159 and 158, respectively. The strap reinforces the tensile strength of the coil 151, and also prevents longitudinal extension of the coil which might adversely affect the bending strength of the coil. As shown in Figure 22, the spring coil assembly of Figure 21 may be applied to join a laser-heated cautery cap directly to the spring coil, rather than to the retaining ring of the cap. As in all the Figures herein, like reference numerals refer to like components. A further aspect of the invention is the provision of laser-heated cautery cap constructions adapted for special purposes. With regard to Figure 23, a cap 161 includes an inner side wall 162 and an outer side wall 163 disposed in concentric relationship about the axis of the optical fiber. The distal end wall 166 is fairly thick, providing high thermal conduction to the distal surface and to the distal side wall portions. The annular gap 164 provides an insulating barrier between the interior chamber and the outer side wall. An example of the utility of the cap construction of Figure 23 is illustrated in Figure 24. The jacket 17 of the fiber 16 is received within the inner side wall 162, with the fiber end directed toward the distal end wall 166. The proximal end of the outer wall 163 is received within the sleeve 168 of a catheter or the like. The annular space 171 between the sleeve 168 and the fiber jacket defines a flow channel for cooling liquid SUBSTITUTE SHEET which extends to the annular chamber 164. A plurality of vent holes 167 are drilled through the end wall from the interior chamber 164 to the exterior periphery of the end wall to eject cooling liquid peripherally to the heated working surface 166 of the cap. A bushing 169 is secured about the distal end of the outer side wall, so that the impinging vessel wall will be urged outwardly to avoid contact with the heated end surface. With regard to Figures 32 and 33, another version of the concentric wall cap includes the inner and outer walls 162 and 163 described previously, and the annular chamber 164 disposed therebetween. The end wall 166 is substantially machined away, delineating a central open passage 172. A bushing 173 lines the passage 172, and a standard arterial guide .wire 174 is received within the bushing 173 in slidable fashion. A plurality of jacketed optical fibers 176 extend longitudinally into the chamber 164 with the fiber ends directed toward the end wall thereof. The fibers 176 are spaced peripherally about the chamber 164, and the interstitial spaces are filled with ceramic or epoxy filler 178. A spacer bushing 169 is received about the distal end portion of the exterior side wall to establish spacing between the vessel wall and the heated end wall. It may be appreciated that the embodiment of Figures 32 and 33 may be advanced coaxially over an arterial guide wire or over the shaft of a balloon catheter introduced previously into a vessel. Upon encountering an atherosclerotic lesion, the annular end wall of the cap may be heated SUBSTITUTE SHEET uniformly ' by use of all the optical fibers to bore through the plaque deposits. Alternatively, the fibers 176 may be used singly or in pairs to preferentially heat a portion of the working surface, so that eccentric lesions may be treated. The thermal energy is generally directed axially and distally of the cap for penetrating atherosclerotic lesions and gaining access through a lesion. Fig. 30-31 depicts a further refinement of the multiple fiber coaxial cautery cap of Figures 32 and 33 which is adapted for annealing vessel walls after balloon angioplasty procedure or laser revascularization or the like. It includes the same double wall concentric design, with an annular chamber 164 and a central passage 172 extending therethrough. As before, a plurality, of optical fibers 176 extend into the chamber 164 and are directed toward the annular end wall. However, in this embodiment an annular target member 177, formed of tantalum or the like, is disposed in the distal end of the chamber 164 and press fit into contact with the outer wall 163. The target member is disposed to receive the plurality of beams from the optical fibers 176, the resulting thermal energy being conducted towards the shoulder 178 that joins the end wall and the outer side wall. The shoulder is thus heated by the laser energy, transferring heat to the vessel wall for annealing purposes, as explained previously. It should be noted that the fibers can be illuminated in any combination to heat any of the quadrants of the shoulder 178. SUBSTiTUTE SHEET A hollow guide wire 179 extends through the passageway 172 in slidable fashion, the guide wire being introduced into a vessel first and advanced toward the lesion or area to be treated. The guide wire 179 includes concentric flow channels in the central bore 181 for fluids or gas. One flow channel includes a port 183 opening into an inflatable balloon 182 secured about the distal end portion of the guide wire. The other flow channel extends to a port 184 which opens distally of the end wall to emit flushing solution and to aspirate debris and fluid from the revascularization or annealing site. It may be appreciated that the balloon may be inflated as in Figure 31 to block the vessel while the flushing procedure is carried out. It may be noted that in either of the two coaxial configurations described above the.. guide wire can be removed, leaving the cap-fiber assembly in the vessel. A coherent viewing bundle of optical fibers may then be advanced through the lumen of the assembly to the distal end of the cap to view the vessel beyond the cap. This feature allows direct visualization of the treatment site to augment other data, a feature generally not possible with prior art devices. Another special configuration of the present invention, shown in ■ Figure 34, includes a cap construction as in Figure 10 that is designed to be heated eccentrically along a side wall portion for selective annealing procedures and the like. The jacket 77 of the optical fiber is housed within a sleeve 187, and the sleeve 187 extends through an arterial catheter 186. SUBSTITUTE SHEET An annular flow channel between the sleeve and catheter has a port 189 opening into an annular balloon 188 secured about the distal end of the catheter. An eccentric balloon 191 is secured to the distal end of the sleeve; a flow channel between the jacket 77 and the sleeve 187 includes a port 192 opening into the balloon 191. The balloon 191 is oriented to be diametrically opposite the heated zone 97 of the cap 76. In large vessels requiring annealing of eccentric vessel wall portions, the balloon 188 may be inflated to grip the vessel wall and hold the assembly in place. The cap is then heated as described previously, and the balloon 191 is inflated. The expansion of the balloon 191 pushes against the confronting vessel wall, thereby urging the assembly drive the heated surface 97 into the opposed portion of the vessel wall. A further embodiment of the present invention is adapted for use in conjunction with a flexible catheter, for example in larger blood vessels. As shown in Figures 28 and 29, the cap construction 67' is substantially the same as in Figure 3, although any of the constructions described herein could also be used. In this embodiment the sidewall of the cap is substantially longer in the axial direction, and an annular bushing 72 is received about the proximal portion of the sidewall. The bushing is spaced a sufficient distance from the heated end wall 70 to avoid thermal damage thereto. The diameter of the bushing is such that it is received within the lumen 73 of an arterial catheter 75 in freely translating fashion with SUBSTITUTE SHEET minimal radial clearance. The assembly consisting of the catheter, the cap, and the optical fiber assembly may be advanced to the site of the atherosclerotic occlusion. The catheter acts to center the assembly in the vessel, with the. cap spaced from the catheter sidewall and thus from the sidewall of the blood vessel. The cap is advanced slightly from the distal end of the catheter to impinge on the atherosclerotic deposits, and laser heated to destroy the plaque. The spacing created by the bushing prevents thermal damage to the catheter and to the vessel wall. It may be appreciated that all of the several embodiments of the present invention may be used singly or in various combination to improve the operational characteristics of the laser-heated cautery cap. SUBSTITUTE SHE Cf

Claims: CLAIMS 1. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, the improvement comprising: a closed continuous curved sidewall joined to said closed end, and means for restricting thermal conduction from said closed end through said sidewall. 2. The improved laser-heated cautery cap of claim 1, wherein said means for restricting thermal conduction further includes an outer annular portion of said closed end having a reduced thickness substantially less than the thickness of the central portion of said closed end which receives said laser iUumination. 3. The improved laser-heated cautery cap of claim 1, wherein said means for restricting thermal conduction further includes a first portion of said sidewall adjacent to said closed end and having a reduced thickness substantially less than the thickness of the remaining portions of said sidewall. SUBSTITUTE SHEET 4. The improved laser-heated cautery cap of claim 1, further including means for securing a flexible guide wire to said cap to guide said cap through the vessel. 5. The improved laser-heated cautery cap of claim 4, wherein said means for securing a flexible guide wire includes a flared end of said flexible guide wire, a hole extending through said closed end and dimensioned to receive said flared end of said flexible guide wire. 6. The improved laser-heated cautery cap of claim 4, wherein said means for securing a flexible guide wire includes a guide sleeve joined to .said sidewall, . said sleeve having a bore extending longitudinally therethrough, said bore being of sufficient diameter to receive said flexible guide wire in freely sliding fashion therethrough. 7. The improved laser-heated cautery cap of claim 4, wherein said optical fiber includes a sleeve-like jacket,, and further including means spaced from said cap to mechanically join said cap to said jacket. 8. The improved laser-heated cautery cap of claim 7, wherein said means to mechanically join said cap to said jacket includes a strap extending from said sidewall away from said closed end and along the outer surface SUBSTITUTE SHEET of said jacket, an annular member extending about said jacket and spaced longitudinally from said cap, said strap joined to said annular member, and means for joining said annular member to said jacket. 9. The improved laser-heated cautery cap of claim 1, further including an arterial guide catheter having a lumen extending therethrough, said optical fiber extending through said lumen, said cap being disposed to protrude from the distal end of said catheter, and a bushing secured about a proximal portion of said sidewall to define an annular gap between said cap and said catheter. 10. The improved laser-heated cautery cap of _ claim 9. wherein said optical fiber includes a sleeve-like jacket, and further including at least one band of tensile filaments wrapped about said jacket in helical fashion, means for mechanically joining said cap and one end of said band to said jacket, said band extending from said cap along said jacket away from said closed end. 11. The improved laser-heated cautery cap of claim 10, further including a pair of bands of tensile filaments, said bands being wrapped in opposite helical directions about said jacket. SUBSTITUTE SHEE " 12. The improved laser-heated cautery cap of claim 1, wherein said optical fiber includes a sleeve-like jacket, and further including a braided wire sleeve secured about said jacket, means for mechanically joining said cap and one end of said braided wire sleeve to said jacket, said braided wire sleeve extending from said cap along said jacket away from said closed end. 13. The laser-heated cautery cap of claim 1, wherein said closed continuous curved sidewall is formed in a prolate spheroidal configuration having a major axis generally coaxial with the axis of said optical fiber. 14. The laser-heated cautery cap of claim 13, wherein said, means for restricting thermal conduction from said closed end includes at least one annular portion of reduced thickness interposed between said closed end and said sidewall. 15. The laser-heated cautery cap of claim 13, further including a tapered tip extending from the outer surface of said closed end and disposed generally parallel to said axis of said optical fiber. SUBSTITUTE SHEET 16. The laser-heated cautery cap of claim 13, further including a guide wire extending from the outer surface of said closed end and disposed generally parallel to said axis of said optical fiber. 17. A laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including a closed curved sidewall having an prolate form, means for joining one end of said prolate sidewall to one end of an optical fiber, said prolate form having a major axis generally parallel to the axis of the optical fiber, said cap including interior surface means for receiving illumination from said optical fiber and undergoing heating thereby. 18. The laser-heated cautery cap of claim 17, wherein said interior surface means includes a target member disposed within said cap to receive illumination from said optical fiber, said target member impinging on portions of the inner surface of said closed curved sidewall to conduct thermal energy thereto. 19. The laser-heated cautery cap of claim 18, wherein said target member comprises a disc having a peripheral edge impinging on an annular portion of said inner surface of said closed curved sidewall. TVT UTE HEE SUBS 20. The laser-heated cautery cap of claim 18, wherein said target member comprises a disc having a peripheral edge impinging on a portion of an annulus of said interior surface of said closed curved sidewall. 21. The laser-heated cautery cap of claim 18, wherein said target member is disposed to receive substantially all of the illumination from said optical fiber and to shield the other end of said oblate sidewall from illumination and heating. 22. The laser-heated cautery cap of claim 18, wherein said target member is selectively positioned along said major axis to conduct thermal energy to predetermined portions of said closed curved sidewall, and further including means for restricting thermal conduction to the remaining portions of said closed curved sidewall. 23. The laser-heated cautery cap of claim 17, further including means for restricting thermal conduction from said interior surface means to selected portions of said closed curved sidewall. 24. The laser-heated cautery cap of claim 23, wherein said means for restricting thermal conduction includes at least one annular portion of SUBSTITUTE SHEET said sidewall having reduced thickness with respect to the remainder of said sidewall. 25. The laser-heated cautery cap of claim 17, further including guide wire means extending from the other end of said prolate form and oriented generally parallel to said major axis. 26. The laser-heated cautery cap of claim 17, further including a tapered tip extending from the other end of said prolate form and oriented generally parallel to said major axis. 27. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, the improvements comprising: a closed continuous curved sidewall joined to said closed end, and means for restricting thermal conduction from said closed end through said sidewall, means for securing a flexible guide wire to said cap to guide said cap through the vessel to atherosclerotic lesions, said optical fiber including a sleeve-like jacket, and further including means spaced from said cap to mechanically join said cap to said jacket, SUBSTITUTE SHEET at least one band of tensile filaments wrapped about said jacket in helical fashion, means for mechanically joining said cap and one end of said band to said jacket, said band extending from said cap along said jacket away from said closed end, and further including an arterial guide catheter having a lumen extending therethrough, said optical fiber extending through said lumen, said cap being disposed to protrude from the distal end of said catheter, and a bushing secured about a proximal portion of said sidewall to define an annular gap between said cap and said catheter. 28. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, the improvement comprising: means for securing a flexible guide wire to said cap to guide said cap through the vessel to atherosclerotic lesions. 29. The improved laser-heated cautery cap of claim 28, wherein said means for securing a flexible guide wire includes a flared end of said flexible guide wire, and a hole through said closed end dimensioned to receive said flared end in permanent fit relationship. SUBSTITUTE SHEET 30. The improved laser-heated cautery cap of claim 29, wherein said flared end is welded to the inner surface of said closed end of said cap. 31. The improved laser-heated cautery cap of claim 28, wherein said means for securing a flexible guide wire includes a guide sleeve joined directly to said sidewall, said sleeve having a bore extending longitudinally therethrough, said bore being of sufficient diameter to receive said flexible guide wire in freely sliding fashion therethrough. 32. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the jacket and having a closed end disposed to be heated by laser illumination from the optical fiber, the improvement comprising: means for mechanically joining said cap to said jacket, including means spaced from said cap to mechanically connect said cap to said jacket. 33. The improved laser-heated cautery cap of claim 32, wherein said means to mechanically join said cap to said jacket includes a strap extending from said sidewall away from said closed end and along the outer surface of said jacket, an annular member disposed about said jacket and spaced longitudinally from said cap, said strap joined to said annular SUBSTITUTE SHEET member, and said annular member being adapted to be permanently secured to said jacket. 34. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, the improvement comprising: an arterial guide catheter having a lumen extending therethrough, said optical fiber extending through said lumen, said cap being disposed to protrude from the distal end of said catheter, and a bushing secured about a proximal portion of said sidewall to define a thermally insulating annular gap between said cap and said catheter. 35. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including a jacketed optical fiber and a cap secured to one end of the jacket and having a closed end disposed to be heated by laser illumination from the optical fiber, the improvement comprising: at least one band of tensile filaments wrapped about said jacket in helical fashion, means for mechanically joining said cap and one end of said band to said jacket, said band extending from said cap along said jacket away from said closed end, whereby tension applied to said jacket and said SUBSTITUTE SHEET band will constrict said band about said jacket and compress said jacket about said optical fiber. 36. The improved laser-heated cautery cap of claim 35, further including a pair of bands of tensile filaments, said bands being wrapped in opposite helical directions about said jacket. 37. The improved laser-heated cautery cap of claim 35, wherein said tensile filaments are formed as a braided sleeve secured about said optical fiber jacket. 38. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, the improvement comprising: means for heating a selected eccentric portion of said cap and restricting thermal conduction to the remainder of said cap. 39. The laser-heated cautery cap of claim 38, further including an arterial guide catheter having a lumen extending therethrough, said optical fiber. extending through said lumen, said cap being disposed to protrude from the distal end of said catheter, and inflatable balloon means secured to SUBSTITUTE SHEET a portion of said distal end of said catheter diametrically opposed to said heated, eccentric portion of said cap and disposed to be inflated and drive said eccentric portion into contact with a vessel wall. 40. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, the improvement comprising: terminal connection means secured to said one end of said fiber and having an outer diameter of standardized dimension, a plurality of said caps of various shaped and sizes, said plurality of caps each having an open end dimensioned to be received about said terminal connection means in interchangeable fashion, and means for securing one of said plurality of caps to said terminal connection means. 41. The improved laser-heated cautery cap of claim 40, wherein said terminal connection means includes a bushing secured about said one end of said optical fiber, said bushing having an outer diameter of said standardized dimension. 42. The improved laser-heated cautery cap of claim 41, further including a sleeve interposed between said bushing and said optical fiber, SUBSTITUTE SHEET said sleeve including a flared end having a diameter greater than the inner diameter of said bushing to retain said bushing at said one end of said optical fiber. 43. The improved laser-heated cautery cap of claim 42, wherein said means for securing one of said plurality of caps includes crimp means for joining the open end of a cap about said bushing. 44. In a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to one end of the fiber and having a closed end disposed to be heated by laser iHumination therefrom, the improvement comprising: means for reinforcing and strengthening said optical fiber to comprise an integral catheter, including a spring coil secured about said optical fiber, means for securing a distal end of said spring coil to said optical fiber adjacent to said cap, and means for securing the proximal end of said spring coil to said optical fiber. 45. The improved laser-heated cautery cap of claim 44, further including strap means extending the length of said spring coil to maintain the spacing of said proximal end and distal end thereof. SUBSTITUTE SHEET 46. A laser-heated cautery cap, including an outer cylindrical sidewall, an inner cylindrical sidewall disposed concentrically thereto, a closed end wall joining said concentric sidewalls, and at least one optical fiber secured to said cap and having an output end disposed to deliver laser illumination toward said closed end wall to heat said cap. 47. The laser-heated cautery cap of claim 46, further including a bore extending through said inner sidewall and through said closed end wall and adapted to receive a guide wire therethrough. 48. The laser-heated cautery cap of claim 47, further including an annular chamber defined between said concentric sidewalls, and a plurality of optical fibers having said output ends disposed within said annular chamber. 49. The laser-heated cautery cap of claim 48, further including preferential directional heating means disposed within said annular chamber to receive illumination from said optical fibers and undergo heating thereby, and to conduct thermal energy primarily to said outer concentric sidewall. SUBSTITUTE SHEET 50. The laser-heated cautery cap of claim 46, wherein said closed end wall extends continuously across said inner and outer concentric sidewalls, said optical fiber output end disposed within said inner sidewall. 51. The laser-heated cautery cap of claim 50, wherein said concentric sidewalls define an annular space therebetween, and port means extending from said annular space through said outer sidewall to permit fluid flow from said annular space to the exterior of said cap. 52. hi a laser-heated cautery cap for revascularization of atherosclerotic blood vessels, including an optical fiber and a cap secured to .one end of the fiber and having a closed end disposed to be heated by laser illumination therefrom, a system for controlling the temperature of said cap, comprising; a laser light source coupled to the other end of said optical fiber, a beam splitter interposed between said laser light source and said optical fiber to receive thermal radiation from said heated cap, photodetector means disposed to receive said thermal radiation from said beam splitter and generate a voltage signal in proportion to the temperature of said cap, and display means for receiving said said voltage signal and indicating the temperature of said cap. SUBSTITUTE SHEET 53. The cautery cap temperature control system of claim 52, further including filter means interposed between said beam splitter and said photodetector means for selectively blocking said laser light source and passing said thermal radiation. 54. The cautery cap temperature control system of claim 53, further including means for selectively controlling the output power of said laser light source in accordance with said voltage signal level to maintain a preselected operating temperature of said cap. SUBSTϊTUTΞ SHEET

Inventors: LEE GARRETT, RINK DAN L, RINK JOHN L, LEE, GARRETT, RINK, DAN, L., RINK, JOHN, L.
Applicants: XINTEC CORP, XINTEC CORPORATION
Application year: 1988
Main classification: A61B19
IPC codes: A61B17, A61B18, A61F7, B23K26