Maneuverable distal apparatus

Abstract: A maneuverable distal apparatus (10) includes a temperature-activated memory element (20) moving in a first direction to assume a predetermined shape when heated to a predetermined temperature and control means (34) for selectively heating the memory element so that the memory element is moved in the first direction. A spring (242) is provided for yieldably urging the memory element in a second direction away from the first direction upon cooling of the memory element to a temperature less than the predetermined temperature so that the memory element is moved to assume a shape other than the predetermined shape.

Description: The present invention relates to guide apparatus, probes, and the like, and particularly to guide apparatus that are steerable through body cavities and aimable at obstructions, organs, or tissue within the body from a position external to the body. More particularly, the present invention relates to maneuverable guide apparatus including spring means for biasing a temperature-activated memory element to alter the shape of the memory element upon cooling of the memory element to a temperature below its martensitic transformation temperature. Some attempts have been made in the past to provide catheters having distal ends which, when inserted into a body, are manipulatable to advance the catheter through body cavities. See for example, U.S. Patents 3,674,014 and 3,773,034. The catheter disclosed in patent 3,674,014 includes permanent magnets and employs a magnetic field to bend the distal end of the catheter. The catheter disclosed in patent 3,773,034 includes fluid conduits and employs a fluid to bend the distal end of the catheter. Other controlled devices are disclosed in U.S. Patents 3,605,725 and 4,176,662. However, these prior devices are quite difficult to control and manipulate. Some work has previously been done to produce a catheter which is readily insertable while being effectively anchorable in a body cavity. See, for example, U.S. Patents 3,729,008 and 3,890,977. In U.S. Patent 3,890,977 to Wilson, the distal end of the catheter is formed into a desired shape by using a material exhibiting mechanical memory that is triggered by heat. By heating the mechanical memory material, the distal end of the catheter is shaped to anchor the catheter within the body. However, the change of the shape or other movement of the distal end in these prior devices is limited to a single direction. Once the memory material has been heated causing the distal end to move in said single direction to assume its characteristic anchoring shape, it becomes necessary to deform the distal end manually at a temperature below the transition temperature of the mechanical memory material in order to change the shape of the distal end. The need for manual manipulation of a catheter once it is inserted into a body limits the steerability and aimability of the catheter. Other devices are known for guiding a catheter to a particular location within the body. See for example U.S. Patent 3,043,309. U.S. Patent 4,543,090 discloses a maneuverable distal apparatus comprising a temperature activated memory element moving in a first direction to assume a predetermined shape when heated to a predetermined temperature, means for urging the memory element in a second direction away from the first direction upon cooling of the element and control means for selectively heating the memory element. One object of the present invention is to provide a steerable guide apparatus, probe, and the like which is easy to operate and steerable in a plurality of different directions within the body. Another object of the present invention is to provide an aimable guide apparatus, probe, and the like which is easy to operate and which can be aimed at obstructions, organs, or tissues in a plurality of different directions within the body. Another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like of very simple design having only one temperature-activated memory element that is movable to a predetermined shape using remote controls to steer and aim the guide apparatus and yet is automatically returnable to an initial shape without manual manipulation by an operator. Still another object of the present invention is to provide a highly maneuverable guide apparatus, probe, and the like having at least one resilient element for biasing the distal end of the guide apparatus to assume an initial shape and a separate temperature-activated memory element that is movable under heat to bend the distal end of the guide apparatus to a multiplicity of shapes other than the initial shape. Another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like of simple construction wherein a memory element is employed to deflect a guide wire made of spring material. Yet another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like wherein the guide wire is made of a resilient shape-memory material. Still another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like wherein a temperature-activated memory element made of a shape-memory alloy and employed to deflect a guide wire made of spring material is coupled to the guide wire to apply an axial compression pulling force to the guide wire as the length of the memory element is shortened upon being heated to a predetermined temperature in accordance with a thermal property of the shape-memory alloy so that the guide wire is "pulled" along its axis by the memory element to assume a different shape. According to the present invention, a maneuverable distal apparatus is provided comprising a temperature activated memory element moving in a first direction to assume a predetermined shape when heated to a predetermined temperature, means for yieldably urging the memory element in a second direction away from the first direction upon cooling of the memory element to a temperature less than the predetermined temperature so that the memory element is moved to assume a shape other than the predetermined shape and control means for selectively heating the memory element so that the memory element is moved in the first direction, the apparatus characterized in that the means for urging the memory element in a second direction away from the first direction is spring means and in that insulation means is provided for preventing electrically conductive contact between the memory element and the spring means. In preferred embodiments, the spring means is an elongated coil spring formed to include a longitudinal cavity and the memory element is positioned in the longitudinal cavity. The insulation means includes a tubular sleeve positioned in the longitudinal cavity and the memory element is positioned in the tubular sleeve. An end cap is coupled to a distal end of the elongated coil spring and the insulation means includes means for preventing electrically conductive contact between the memory element and the end cap. The control means includes power supply means, first electrical lead means for coupling the power supply means and the spring means in electrical communication, and second electrical lead means for coupling the power supply means and the memory element in electrical communication. Circuit means interconnecting the spring means and the memory element is provided for establishing an electrical circuit electrically connecting the spring means, the memory element, and the control means in series. In yet another embodiment, the memory element is disposed inside a hollow axially compressible guide wire made of spring material and anchored at its opposite ends to spaced-apart distal and proximal portions of the guide wire. The "double-anchored" memory element shortens in length in accordance with due to a characteristic thermal property of the shape-memory alloy comprising the memory element upon being heated to a predetermined temperature. Such shortening acts to apply an axial compression load to the axially compressible guide wire, thereby effectively "pulling" the guide wire to assume a different shape. The guide wire returns toward its initial shape upon cooling of the memory element to a temperature less than the predetermined temperature due, in part, to spring characteristics of the guide wire. One notable advantage of this double-anchored feature is that the size and mass of the memory element can be reduced significantly in comparison to other embodiments since less force is required to pull the guide wire to a different shape than to push the guide wire to the same shape. It will be understood that "pulling" refers generally to axial compression loading or the like of the guide wire, while "pushing" refers generally to transverse shear loading or the like of the guide wire. Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived. Brief Description of the Drawings The detailed description particularly refers to the accompanying figures in which: Fig. 1 is a longitudinal sectional view of an embodiment of the present invention, partly broken away, showing the distal end of a guide apparatus in a relaxed position; Fig. 2 is a view of the embodiment of Fig. 1 , partly broken away, showing the distal end of the guide apparatus in a partially deflected position; Fig. 3 is a view of the embodiment of Fig. 1 , partly broken away, showing the distal end of the guide apparatus in a fully deflected position; Fig. 4 is a longitudinal sectional view of another embodiment of the present invention showing a temperature-activated memory element positioned within a coiled spring; Fig. 5 is a longitudinal sectional view of yet another embodiment of the present invention; Fig. 6 is a longitudinal sectional view of still another embodiment of the present invention showing a type of circuit means different than that shown in Figs. 4 and 5; Fig. 7 is a transverse sectional view, taken generally along lines 7-7 of Fig. 6, showing rotation of a guide wire in a clockwise direction about its longitudinal axis in response to heating the temperature-activated memory element inside above its transition temperature; Fig. 8 is a longitudinal sectional view of still another embodiment of the present invention having a double-anchored temperature-activated memory element arranged to apply pulling force to its companion spring return means during movement of the memory element to assume a predetermined shape under thermal loading; and Fig. 9 is a longitudinal sectional view of yet another embodiment of the present invention having a double-anchored temperature-activated memory element coupled directly to a current source. Detailed Description of the Drawings A catheter 210 embodying the present invention is shown generally in Fig. 1. Catheter 210 includes a tubular member 12, a temperature-activated memory element 20, and a sleeve 112 of the types described above. An electrically insulative hollow core member 240 is provided in the interior of tubular member 12 for receiving medical instruments, fiber optics lines, fluid-conducting tubes, or other medical or optical tools. Core member 240 is desirably made of plastics material such as urethane, TEFLON, KYNAR, or polyethylene and has a wall thickness of .005 - .010 inch (1.27 - 2.54 mm). Core member 240 is preformed using known techniques to assume a curved shape in its relaxed position as shown in Fig. 1. The catheter 210 further includes a spring 242 positioned on the exterior of curved core member 240 in diametrically opposed relation to memory element 20. The spring 242 is desirably made of stainless steel or plastics material and has a thickness of .010 inch (2.54 mm). The spring 242 is also preformed using known techniques to assume a curved shape. As shown in Fig. 1, the radius of curvature of preformed spring 242 is less than the radius of curvature of curved core member 240. Spring 242 effectively serves as a resilient memory element and cooperates with core 240 to load memory element 20 with a force that bends memory element 20 to an initial shape illustrated in Fig. 1. The spring constant of spring 242 is selected to cause spring 242 to bend the distal end of the catheter in one direction as shown in Fig. 1 and also yield under loading provided by the heated memory element 20 to permit the distal end of the catheter to bend in an opposite second direction as shown in Figs. 2 and 3. Sleeve 112 slidably couples memory element 20 and preformed spring 242 to curved core member 240 so that the memory element 20 and spring 242 are permitted to slip in relation to the adjacent core member 240 when either of the memory element 20 and the spring 242 move to assume its preset shape. The sleeve 112 also interconnects memory element 20 to spring 242 so that when the memory element 20 moves in a first direction 254 to assume its preset shape a force is applied to move the spring 242 in the first direction 254 and vice versa. In the diagrammatic embodiment illustrated in Figs. 1-3, the temperature-activated memory element 20 is electrically connected to a control device 234 and a power supply 244 by wires 130, 134, and 246. Control device 234 includes switch means 248 and power control means 250. Switch means 248 is operable to decouple the power supply 244 and the memory element 20 to prevent heating of memory element 20. Power control means 250 is operable to vary the electrical power provided to memory element 20, thereby regulating the amount of heat applied to memory element 20. Illustratively, power control means 250 is a rheostat. It will be appreciated by those skilled in the art that the manner of controlling the temperature of memory element 20 can be accomplished using a variety of control systems other than the illustrated system without departing from the scope of the present invention. One exemplary operation sequence of catheter 210 is illustrated in Figs. 1-3. In particular, the relaxed state of the distal end of tubular member 12 is shown in Fig. 1. The preset curved shapes of core member 240 and spring 242 act to bend the distal end of tubular member 12 in direction 252 as shown in Fig. 1. At this stage, switch means 248 is in its open circuit position, preventing current generated by power supply 244 from being applied to heat the memory element 20. Thus, the relatively cool memory element 20 is also bent in direction 252 due to the interconnection with core member 240 and spring 242 established by sleeve 112 and tubular member 12. Such bending resulting from the preset curved shapes of core member 240 and spring 242 effectively defines an "initial position" of the memory element 20 and the distal end tubular member 12. Steering and aiming of catheter 210 is accomplished by operation of control device 234 in the following manner. Once switch means 248 is moved to its closed circuit position shown in Figs. 2 and 3, the operator can control the heating and cooling of the temperature-activated memory element 20 by using power control means 250. Movement of power control means 250 to a first setting illustratively depicted in Fig. 2 causes a sufficient amount of power to be applied to memory element 20 so that the memory element 20 is heated and moves in direction 254 away from its initial curved shape to assume a substantially straight shape. The steering force generated by such movement is transmitted to core member 240 and spring 242 in part via sleeve 112. This steering force is sufficient to overcome opposing "return" forces generated by core member 240 and spring 242. Continued movement of power control means 250 to another power setting illustratively depicted in Fig. 3 causes still more power to be applied to memory element 20. This heats memory element 20 to a higher "predetermined" temperature, causing the memory element 20 to continue to move in direction 254 to assume a "predetermined" curved shape. Return of the catheter 210 to its initial relaxed state shown in Fig. 1 is easily accomplished by using control device 234 to lessen the amount of power applied to memory element 20. This step allows memory element 20 to cool, thereby permitting preset core member 240 and spring 242 to cooperate to exert a return force on the distal end of the tubular member 12 and memory element 20. Such a return force acts in direction 252 in the absence of a steering force generated by memory element 20, thereby causing catheter 210 to be returned to its relaxed state. It will be appreciated that a plurality of pairs of temperature-activated memory elements 20 and springs 242 could be positioned in the distal end of the catheter to provide a great deal of flexibility in steering and aiming the catheter. However, it will be understood that it is possible to steer and aim a catheter provided with only a single temperature-activated memory element 20 and return spring 242 in a multiplicity of radial directions by rotating the catheter about its central longitudinal axis during heating of memory element 20 using control device 234. Several other embodiments of the present invention are shown in Figs. 4-9. In each of the embodiments illustrated in Figs. 4-9, a heatable temperature-activated memory element is positioned within a guide wire made of spring material. Figs. 4-9 illustrate preferred embodiments of using a temperature-activated shape-memory alloy to deflect a guide wire or the like. Although such steerable guide wire assemblies are easily installed in catheters as shown, it will be appreciated that the steerable guide wire concept has much broader application and does not necessarily have to be inserted within a catheter. In other words, the guide wire itself can provide a catheter for insertion into canals, vessels, passageways, or body cavities to permit injection or withdrawal of fluids or to keep a passage open. One embodiment of a steerable guide wire assembly is illustrated in Fig. 4. Memory element 310 is positioned in an interior chamber 312 of guide wire 314. Memory element 310 is oriented to deflect guide wire 314 from an initial position (solid lines) to a deflected position (phantom lines) upon bending movement of memory element 310 to assume a predetermined bent shape (not shown). Memory element 310 is desirably made of a shape-memory alloy such as nitinol and configured to include a pair of lead-attachment portions 316a, b and a shape-memory portion 318. Reference is hereby made to U.S. Patent No. 4,777,799, entitled "Memory Element" and filed concurrently herewith, for a description of the construction, function, and operation of portions 316 and 318. Guide wire 314 is desirably a coil made of TEFLON-coated 304 stainless steel spring material. Guide wire 314 includes a proximal portion 320 disposed in base 324 and a distal portion 322 to provide an assembly for steering and aiming the base 324. It will be understood that base 324 can be configured to provide a catheter, cannula, or the like for receiving guide wire 314 or that guide wire 314 can function in accordance with the present invention on its own as a catheter independent of any such base means. A rounded cap 326 is coupled to the distal portion 322 of guide wire 314 to provide a smooth probe tip for the assembly. An insulative sleeve 328 having a side wall 330 and a top wall 332 is positioned in the interior chamber 312 of guide wire 314 so that top wall 332 lies in abutting relation to cap 326 and side wall 330 lies intermediate guide wire 314 and memory element 310. Advantageously, insulative sleeve 328 prevents electrical communication between memory element 310 and each of guide wire 314 and cap 326. An electrical system is provided for selectively heating memory element 310 to a temperature in excess of its transition temperature by varying the current passing through memory element 310 so that memory element 310 moves to assume a predetermined shape and deflect guide wire 314. Such deflection results from engagement of guide wire 314 by the moving memory element 310 disposed within interior chamber 312 of guide wire 314. Thus, movement of guide wire 314 is induced by moving memory element 310 without depending upon a fixed coupling between guide wire 314 and memory element 310. The electrical system includes a power supply 334, first lead means 336 for electrically connecting one terminal of the power supply 334 to lead-attachment portion 316b, and second lead means 338 for electrically connecting another terminal of power supply 334 to lead-attachment portion 316a. Another embodiment of the invention is illustrated in Fig. 5. Reference numerals from Fig. 4 have been applied to the assembly as shown in Fig. 5 where the same or similar parts are being used. In this embodiment, an insulative coating material (not shown) is applied to at least one of memory element 310, guide wire 314, and cap 326 in lieu of insulative sleeve 328. Thus, the insulative coating also acts to prevent change in the magnitude of current flowing through memory element 310 due to either incidental or sustained contact with guide wire 314 and/or cap 326 during movement of memory element 310 upon being heated above its transition temperature. Yet another embodiment of the invention is illustrated in Fig. 6. Reference numerals from Figs. 4 and 5 have been applied to the assembly as shown in Fig. 6 where the same or similar parts are being used. In this embodiment, the second lead means is different than that shown in Figs. 4 and 5 in that the power supply 334 and lead-attachment portion 316a are electrically coupled by means of an electrical connection established by cap 326, guide wire 314, band 340, and lead 342. Cap 326 includes slot 344 for receiving lead-attachment portion 316a and is made of an electrically conductive material. Preferably, lead-attachment portion 316a is welded or soldered in place in slot 344. Alternatively, a mechanical connection could be employed by deforming cap 326 about memory element 310 to clamp lead-attachment portion 316a in place. Conductive band 340 electrically communicates with proximal portion 320 of guide wire 314 and lead 342 to introduce current from power supply 334 to conductive guide wire 314 for distribution to lead-attachment portion 316a of memory element 310. It will be appreciated that either an insulative sleeve or coating of the types described above could be employed to prevent unwanted electrical communication between memory element 310 and guide wire 314. Fig. 7 illustrates rotation of guide wire 314 about its longitudinal axis in response to heating memory element 310 above its transition temperature so that memory element 310 moves to assume its predetermined shape. The solid line position B' of guide wire 314 in Fig. 7 corresponds to the bent phantom line position B in Fig. 6, while phantom line C' in Fig. 7 corresponds to solid line position C in Fig. 6. Thus, in Fig. 7, the guide wire is not shown in its straight position, but rather in each of two of its bent positions. Double arrow 346 represents rotational movement of guide wire 314 relative to base 324. It has been observed that the above-described rotational movement occurs during use of each of the embodiments illustrated in Figs. 4-6 and 8-9. In particular, cap 326 moves along a path (not shown) orbiting its initial position shown in solid lines in Figs. 4-6 and 8-9 during deflection of the guide wire 314 by the heated memory element 310. The guide wire 314 is coiled or otherwise configured to provide means for converting bending forces applied to the guide wire 314 by the memory element 310 to rotation-inducing forces so that the guide wire 314 rotates about its longitudinal axis in response to movement of memory element 310 to assume its predetermined bent shape. It has further been observed that the amount of rotation is controlled by the amount of current applied. In each of the embodiments of Figs. 4-6, 8, and 9, the guide wire 314 is configured to apply a yieldable biasing force to the memory element 310 upon engagement of guide wire 314 and memory element 310 so that memory element 310 is moved to assume a shape (e.g., straight) other than its predetermined bent shape upon cooling of the memory element 310 to a temperature below its transition temperature. Advantageously, guide wire 314 provides yieldable means for returning a cooling memory element to its initial straight position after being heated to assume a predetermined bent position. Such a "yieldable" construction advantageously does not interfere with movement of the memory element 310 to assume its predetermined position. Yet another embodiment of the invention is illustrated in Fig. 8. Reference numerals from Figs. 4-7 have been applied to the assembly as shown in Fig. 8 where the same or similar parts are being used. In this embodiment, memory element 310 is mounted to apply pulling forces to cap 326, thereby inducing movement of guide wire 314 to assume a different position. One characteristic thermal property of shape-memory alloys generally is that such alloys exhibit a negative coefficient of thermal expansion. In other words, shape-memory alloys contract when heated and expand, at least under an externally applied load, when cooled. It will be appreciated that the change in length per unit of length per degree change of temperature is practically constant for each shape-memory alloy. Thus, one can select or design a particular shape-memory alloy which will contract in a predetermined manner upon heating of the alloy to its transition temperature. The embodiment illustrated in Fig. 8 is configured to exploit the above-noted thermal expansion property of shape-memory alloys by anchoring the memory element 310 at its opposite ends 316a, b so that memory element 310 will apply an axial compression load to cap 326 as it contracts under heat. Such loading will tend to pull cap 326 and the attached distal portion 322 of coiled spring 314 from the bent solid line position D to Fig. 8 to the straight phantom line position E also in Fig. 8. In the embodiment of Fig. 8, memory element 310 is annealed to have a straight predetermined shape so that if memory element 310 is bent or twisted while cool and then heated to its transition temperature, it will move to regain its original straight shape. Also, guide wire 314 is preformed to have a bent shape at its distal end, one example of which is illustrated in Fig. 8. Thus, guide wire 314 will act to deflect the memory element 310 housed within as long as the memory element 310 is cooled below its transition temperature. Plug means 354 is disposed in the interior chamber 312 of guide wire 314' and rigidly fixed to proximal portion 320 as illustrated in Fig. 8. It is within the scope of the present invention to insert and mount the plug 354 in guide wire 314 using a variety of techniques, including, for example, providing a plug having external threads for threadedly engaging a coiled spring. Of course, adhesive, soldering, welding, or the like can be employed to provide suitable alternatives. Plug means 354 desirably has at least an electrically conductive portion for interconnecting lead-attachment portion 316b of memory element 310 to first lead means 336 to establish an electrical path coupling memory element 310 and power supply 334. It will be appreciated that insulation means can be interposed between the electrically conductive portion of plug means 354 and guide wire 314 to prevent electrically conductive contact therebetween. Insulation means, for example, could comprise a separate element, a coating, or a portion of plug means 354. In the illustrated embodiment, first anchor means is provided, in part, by a coupling of the distal lead-attachment portion 316a to the end cap 326 while a second anchor means is provided, in part, by a coupling of the proximal lead-attachment portion 316b to fixed plug means 354. Although memory element 310 is effectively anchored at its opposite ends to spaced-apart portions of guide wire 314, significant temperature stresses will not develop in the memory element 310 since the memory element 310 enjoys sufficient freedom for expansion and contraction due to the lengthening and shortening of resilient guide wire 314. In operation, the bent memory element 310 shown in solid lines in Fig. 8 will both straighten and contract to the phantom line position in Fig. 8 upon being heated to its transition temperature. One result of such straightening is that a transverse shear load will be applied to cap 326 by the memory element 310, which load will tend to urge guide wire 314 toward its straightened phantom line position. One result of such contraction is that an axial compression load will be applied to cap 326 by the double-anchored memory element 310, which load will tend to pull the distal portion 32 of the guide wire 314 toward the proximal portion 320 to assist substantially in moving the guide wire to its straightened phantom line position. Thus, these transverse shear load and axial compression load cooperate to induce movement of the guide wire to its straightened phantom line position. One advantage of this feature is that contraction of a shape-memory alloy under heat is used to apply additional movement-inducing forces to the distal portion 322 of guide wire 314. By generating such new forces, it is possible to decrease the size and mass of memory element 310 without significantly degrading the force generation potential of such a memory element. It will be understood that it is within the scope of the present invention to exploit expansion/contraction of the widths or other dimensions of memory elements 310 to generate such guide wire-pulling forces of the type described above and that the invention is not just limited to length expansion/contraction as illustrated in a preferred embodiment as shown in Fig. 8. Still another embodiment of the invention is illustrated in Fig. 9. Reference numerals from Figs. 4-7 and 8 have been applied to the assembly as shown in Fig. 9 where the same or similar parts are being used. In this embodiment, a double-anchored memory element of the type shown in Fig. 8 is directly coupled to power supply 334. Plug means 356 is configured to accommodate a different technique for mounting memory element 310 and applying a current to memory element 310. Nevertheless, plug means 356 is assembled and functions in a manner similar to plug means 354. As shown in Fig. 9, plug means 356 is formed to include first passageway means 358 for allowing memory element 310 to extend through plug means 356 and second passageway means 360 for allowing lead 352 to extend through plug means 356. Memory element 310 is anchored to plug means 356 using any suitable external and/or internal coupling means (e.g., epoxy, adhesive, weld, solder, clamp, etc.). It will be appreciated that in the case of welding, soldering, or the like the lead attachment portion 316b will be sized and positioned relative to plug means 356 to accommodate any such welding or the like to the plug means 356 to preserve the shape-memory characteristics of shape-memory portion 318. Lead 336 is electrically coupled to the rearwardly extending exposed end of lead-attachment portion 316b. Lead 342 extends into interior chamber 312 and through second passageway means 360 and is electrically coupled to lead attachment portion 316a adjacent to the point at which lead attachment portion 316a is anchored to cap 326. In this embodiment, current from power supply 334 is passed directly to memory element 310 via leads 336, 242 without passing through guide wire 314. While illustrative embodiments and uses of guide apparatus, probes, and the like embodying the present invention have been shown and described, it will be appreciated that various modifications may be made to the illustrative embodiments without departing from the scope of the present invention.

Claims: A manoeuvrable distal apparatus (210;310) comprising a temperature activated memory element (20;310) moving in a first direction to assume a predetermined shape when heated to a predetermined temperature, means for yieldably urging the memory element (20;310) in a second direction away from the first direction upon cooling of the memory element to a temperature less than the predetermined temperature so that the memory element is moved to assume a shape other than the predetermined shape and control means (234;334) for selectively heating the memory element (20;310) so that the memory element is moved in the first direction, the apparatus characterised in that the means for urging the memory element in a second direction away from the first direction is spring means (242; 314) and in that insulation means (240;328) is provided for preventing electrically conductive contact between the memory element (20;310) and the spring means (242;314). The apparatus of claim 1, characterised in that the spring means (314) is an elongated coil spring (314) formed to include a longitudinal cavity (312) and the memory element (310) is positioned in the longitudinal cavity. The apparatus of claim 1, characterised in that the insulation means (328) includes a tubular sleeve (328) positioned in the longitudinal cavity (312) and the memory element (310) is positioned in the tubular sleeve. The apparatus of claim 2, further characterised in that it comprises an end cap (326) coupled to a distal end (322) of the elongated coil spring (314), the insulation means (328) including means for preventing electrically conductive contact between the memory element (310) and the end cap (326). The apparatus of claim 1, characterised in that insulation means (328) is provided by an insulative member (328) situated intermediate the memory element (310) and the spring means (314). The apparatus of claim 1, characterised in that insulation means (328) is provided by a coating material on at least one of the memory element (310) and the spring means (314). The apparatus of claim 1, characterised in that control means (334) includes power supply means (334), first electrical lead means (342) for coupling the power supply means and the spring means (314) in electrical communication, and second electrical lead means (336) for coupling the power supply means and the memory element (310) in electrical communication, and circuit means interconnecting the spring means (314) and the memory element (310) for establishing an electrical circuit electrically connecting the spring means (314), the memory element (310), and the control means (334) in series. The apparatus of claim 7, characterised in that memory element (310) is made of an electrically conductive shape-memory alloy, the memory element (310) includes one end (316b) coupled to the second electrical lead means (336) and an opposite end, the spring means (314) includes an electrically conductive coil spring having one end coupled to the first electrical lead means (342) and an opposite end, and in that an electrically conductive end cap (326) is provided, first means (344) being provided for coupling the opposite end of the coil spring and the end cap in electrical communication, and second means being provided for coupling the end cap and the opposite end of the memory in electrical communication. The apparatus of claim 1, characterised in that spring means (314) includes a longitudinal axis, the memory element (310) is positioned along the longitudinal axis to apply a bending force to the spring means (314) upon movement of the memory element (310) to assume its predetermined shape, and the spring means (314) is configured to provide means for converting bending forces to rotation-inducing forces so that the spring means (314) rotates about its longitudinal axis in response to movement of the memory element (310) to assume its predetermined shape. The apparatus of claim 1, characterised in that the spring means (314) includes spaced-apart distal and proximal portions (322,320) and in that the apparatus further comprises first means (326) for anchoring one end of the memory element to the distal portion and second means (354) for anchoring the other end of the memory element to the proximal portion. The apparatus of claim 10, characterised in that spring means (314) is an elongated coil spring (314) formed to include a longitudinal cavity (312), the memory element (310) is positioned in the longitudinal cavity, the first anchor means (326) includes an end cap (326) coupled to the distal portion (322) and means for coupling said one end of the memory element to the end cap, and the second anchor means (354) includes a plug (354) disposed in the longitudinal cavity and fixed to the proximal portion (320), and means for coupling said other end of the memory element to the fixed plug. The apparatus of claim 11, characterised in that the plug (354) provides means for interconnecting the control means (334) and said other end of the memory element. A manoeuvrable distal apparatus comprising a temperature-activated memory element (310) moving to assume a predetermined shape when heated to predetermined temperature, means (242;314) for yieldably applying a biasing force to the memory element so that the memory element is moved to assume a shape other than the predetermined shape upon cooling of the memory element to a temperature less than the predetermined temperature, and control means (234;334) for selectively heating the memory element (20;310) so that the memory element is moved to assume its predetermined shape, characterised in that a guide member (314) is provided and formed to include an interior cavity in which the memory element (20;310) is located, the guide member providing spring means (314) for yieldably applying the biasing force to the memory element. The apparatus of claim 13, characterised in that it further comprises insulation means (240;328) for preventing electrical communication between the memory element (20;310) and the guide member (314). The apparatus of claim 14, characterised in that the insulation means (328) includes at least one of a sleeve (328) positioned in the cavity intermediate the memory element (310) and the guide member (314) and a coating material on at least one of the memory element and the guide member. The apparatus of claim 13, characterised in that the guide member (314) is an elongated, tubular coil spring (314) formed to provide the cavity and the control means (364) includes means (356) for supporting the memory element (310) within the cavity for movement relative to the coil spring (314) so that the memory element applies a displacement force to the coil spring as the memory element moves to assume its predetermined shape causing the guide member to change shape and impart the biasing force to the memory element. The apparatus of claim 16, characterised in that the support means (356) includes at least one electrical lead (336) coupled to the memory element (310). The apparatus of claim 16, characterised in that the coil spring (314) includes spaced-apart distal and proximal portions (322, 320), the support means (356) includes a plug (356) disposed in the interior cavity provided by the tubular coil spring (314) and rigidly fixed to the proximal portion (320) of the coil spring and the memory element (310) is coupled at opposite ends to the distal portion (322) and the plug (356). The apparatus of claim 13, characterised in that control means (334) includes power supply means (334), first electrical lead means (342) for coupling the power supply means and the guide member in electrical communication, and second electrical lead means (336) for coupling the power supply means (334) and the memory element (310) in electrical communication and circuit means interconnecting the guide member (314) and the memory element (310) for establishing an electrical circuit electrically connecting the guide member, the memory element, and the control means in series. A manoeuvrable distal apparatus comprising a temperature-activated memory element (310) moving to assume a predetermined shape when heated to a predetermined temperature, means (314) for yieldably applying a biasing force to the memory element so that the memory element is moved to assume a shape other than the predetermined shape upon cooling of the memory element to a temperature less than the predetermined temperature and control means (334) for selectively heating the memory element (310) so that the memory element moves to its predetermined shape, characterised in that a base member (324) is provided and formed to include an interior chamber and an exterior opening communicating with the interior chamber, in that guide means (314) is provided for selectively steering and aiming the base member (314), the guide means having a proximal portion (320) anchored in the interior chamber to the base member and a distal portion (32) extending through the exterior opening in a direction away from the base member, the guide means (314) including a tubular coiled spring (314) formed to include a longitudinally extending chamber having an open mouth, an end cap (326) coupled to the tubular spring to close the open mouth, the temperature-activated memory element (310) being positioned within the longitudinally extending chamber, the tubular spring (314) being configured to provide spring means for yieldably applying the biasing force to the memory element and in that insulation means (328) is provided for preventing electrically conductive contact between the memory element (310) and the tubular spring (314). The apparatus of claim 20 characterised in that the memory element (310) includes opposite ends (316a, 316b) the guide means (314) further includes first means (344) for anchoring one end of the memory element to the end cap (326) and second means (354;356) for anchoring the other end of the memory element to a portion of the coiled spring situated in spaced-apart relation to the portion coupled to the end cap so that the memory element (310) is fixed at its opposite ends to spaced-apart portions of the coiled spring. The apparatus of claim 21 characterised in that the second anchor means (354;356) includes a plug (354;356) disposed in the longitudinally extending chamber in spaced relation to the end cap (326) and fixed to the coiled spring (314), and the memory element (310) is arranged to interconnect the end cap and the plug. The apparatus of claim 22 characterised in that the control means (334) includes power supply means (334), first electrical lead means (342) for coupling the power supply means and the coiled spring (314) in electrical communication, second electrical lead means (336) for coupling the power supply means (334) and the plug (354) in electrical communication, the end cap (326) and the plug being electrical conductors, and insulation means for preventing electrically conductive contact between the plug and coiled spring (314). A manoeuvrable distal apparatus comprising an elongated temperature-activated memory element (310) moving in a first direction to assume a predetermined shape and shortening in length when heated to a predetermined temperature, and control means (334) for selectively heating the memory element (310) so that the memory element is moved in the first direction characterised in that the apparatus further comprises an elongated coiled spring (314) formed to include a longitudinal cavity and spaced-apart distal (322) and proximal (320) portions, the memory element (310) being disposed in the longitudinal cavity and including opposite ends, first means (326) for anchoring one end of the memory element (310) to the distal portion (322) of the coiled spring (314), second means (354) for anchoring the other end of the memory element (310) to the proximal portion (320) of the coiled spring (314) and in that the memory element (310) is moved in the first direction to apply a movement-inducing transverse shear load to the coiled spring (314) and shortened to apply a movement inducing axial compression load to the coiled spring (314), thereby moving the coiled spring to assume a shape corresponding to the predetermined shape of the memory element (310). The apparatus of claim 24, characterised in that the coiled spring (314), first means (326), and second means (354) co-operate to provide means for yieldably urging the memory element in a second direction away from the first direction upon cooling of the memory element (310) to a temperature less than the predetermined temperature so that the memory element (310) is lengthened and is moved to assume a shape other than the predetermined shape. The apparatus of claim 24, characterised in that the second anchor means (354) includes a plug (354) disposed in the longitudinal cavity and fixed to the proximal portion (320). The apparatus of claim 26, characterised in that the first means (326) includes an end cap (326) interconnecting the distal portion (322) of the coiled spring (314) and said one end of the memory element (310), the control means (334) includes power supply means (334) first electrical lead means (342) for coupling the power supply means (334) and the coiled spring (314) in electrical communication, second electrical lead means (336) for coupling the power supply means (334) and the plug (354) in electrical communication, the end cap and the plug being electrical conductors, and insulation means (328) for preventing electrically conductive contact between the plug and the coiled spring. The apparatus of claim 26 characterised in that the control means (334) includes power supply means (334), first electrical lead means (342) for coupling the power supply means and said one end of the memory element in electrical communication at a point adjacent the first anchor means (326), and second electrical lead means (336) for coupling the power supply means and said other end of the memory element in electrical communication at a point adjacent the second anchor means (354). The apparatus of claim 26 characterised in that the plug (356) is formed to include longitudinally extending passageway and the memory element (310) extends through the passageway to provide an exposed distal end (318) disposed in the longitudinal cavity.

Inventors: MCCOY WILLIAM C, MCCOY, WILLIAM C.
Applicants: CATHETER RES INC, CATHETER RESEARCH, INC.
Application year: 1988
Main classification: A61M25
IPC codes: H01H37, A61B1, A61M25, A61B18, B25J13