Treatment Of Ischaemia

Abstract

An endovascular apparatus for crossing through an obstruction in a blood vessel comprises an elongate endovascular wire and a coupling. The coupling when in use transmits ultrasonic energy along the wire from an ultrasonic energy source to an active tip at a distal end of the wire. The coupling is arranged to couple the source to the wire at any of a plurality of discrete operational positions along the length of the wire for said transmission of ultrasonic energy to the active tip.

Claims

1. Endovascular apparatus for crossing through an obstruction in a blood vessel, the apparatus comprising: an elongate endovascular wire; and a coupling for, in use, transmitting ultrasonic energy along the wire from a source of the ultrasonic energy to an active tip at a distal end of the wire; wherein the coupling is arranged to couple the source to the wire at any of a plurality of discrete operational positions along the length of the wire for said transmission of ultrasonic energy to the active tip.

2. The apparatus of claim 1, wherein the coupling is arranged to enable relative longitudinal movement between the source and the wire when moving between the operational positions.

3. The apparatus of claim 2, wherein the coupling is arranged to enable said relative longitudinal movement while remaining attached to the wire.

4. The apparatus of claim 2, wherein the coupling is arranged to enable said relative longitudinal movement by being removed from and reattached to the wire.

5. The apparatus of claim 4, wherein the coupling and/or the source comprises distal and proximal or lateral openings for longitudinal insertion and withdrawal of the wire.

6. The apparatus of claim 4, wherein the coupling and/or the source comprises at least one longitudinal slot for entry or exit of the wire in a lateral direction transverse to a longitudinal axis of the wire.

7. The apparatus of claim 6, further comprising a locking mechanism that is arranged to capture the wire after lateral entry of the wire through the slot and to release the wire for lateral exit of the wire through the slot.

8. The apparatus of claim 7, wherein the locking mechanism comprises at least one locking member that is rotatable about the wire to capture and to release the wire.

9. The apparatus of any preceding claim, wherein the coupling is arranged to clamp the wire when at any of the operational positions.

10. The apparatus of claim 9, wherein the coupling comprises a collet that is compressible radially onto the wire in response to longitudinal movement or longitudinal compression of the collet.

11. The apparatus of claim 10, wherein the collet comprises at least one mating face that is engaged with the source, that face being inclined relative to a longitudinal axis of the collet.

12. The apparatus of claim 11, wherein the mating face is defined by a tapered end of the collet.

13. The apparatus of claim 11 or claim 12, wherein the collet is movable longitudinally within or relative to a transducer that serves as the source.

14. The apparatus of claim 13, comprising a screw thread between the collet and the transducer, which screw thread is arranged to move the collet longitudinally and to couple the collet to the transducer.

15. The apparatus of any preceding claim, wherein the wire extends through the source and has portions that extend, respectively, proximally and distally from the source.

16. The apparatus of claim 15, wherein the proximally-extending portion of the wire exits a proximal end of the source.

17. The apparatus of claim 15, wherein the proximally-extending portion of the wire exits the source on an axis transverse to a longitudinal axis of the distally-extending portion of the wire.

18. The apparatus of any preceding claim, wherein the operational positions are marked on the wire.

19. The apparatus of any preceding claim, wherein the operational positions are characteristic of harmonics of the wire at an activation frequency of the source.

20. Endovascular apparatus for crossing through an obstruction in a blood vessel, the apparatus comprising: an electrically-driven source of ultrasonic energy; a coupling for exciting an endovascular wire, in use, to transmit ultrasonic energy along the wire from the source thereby coupled to the wire to an active tip at a distal end of the wire; and a signal acquisition and processing system that is configured to capture and respond to operational parameters of the apparatus as the active tip approaches or crosses through an obstruction in use.

21. The apparatus of claim 20, wherein the signal acquisition and processing system is configured to monitor variations of frequency and/or amplitude of current drawn by, or voltage dropped across, the source of ultrasonic energy.

22. The apparatus of claim 20 or claim 21, wherein the signal acquisition and processing system is configured to modulate excitation voltage applied to, or excitation current supplied to, the source of ultrasonic energy.

23. The apparatus of claim 22, wherein the signal acquisition and processing system is configured to control the source of ultrasonic energy by varying frequency and/or amplitude of the excitation voltage applied to the source of ultrasonic energy.

24. The apparatus of claim 23, wherein the signal acquisition and processing system is configured to drive the frequency of the excitation voltage by employing a phase difference between the excitation voltage and the excitation current in conjunction with amplitude of the excitation voltage.

25. The apparatus of any of claims 20 to 24, wherein the signal acquisition and processing system is configured to monitor variations in frequency or amplitude of vibration of the wire via the coupling.

26. The apparatus of claim 25, wherein the signal acquisition and processing system comprises an amplitude feedback controller and is configured to use a resonant frequency as an operating point of control.

27. The apparatus of claim 25 or claim 26, wherein the signal acquisition and processing system is configured to infer displacement of the active tip of the wire from waveforms in the wire determined from said variations in frequency of vibration of the wire.

28. The apparatus of claim 27, wherein the signal acquisition and processing system is configured to employ numerical algorithms selected for specific types of the wire.

29. The apparatus of claim 27 or claim 28, wherein the signal acquisition and processing system is configured to estimate an area mapped out by said displacement of the active tip of the wire in open and occluded vasculature for gelatinous, fibrous and calcified lesions.

30. The apparatus of any of claims 20 to 29, wherein the signal acquisition and processing system is configured to monitor approach to an obstruction and/or to determine characteristics of an obstruction from the captured operational parameters.

31. The apparatus of any of claims 20 to 30, wherein the signal acquisition and processing system is configured to compare relative contributions of losses from anatomical tortuosity in navigating the active tip to the obstruction versus losses arising from the passage of the active tip through the obstruction.

32. The apparatus of claim 31, wherein the signal acquisition and processing system is configured to pulse or vary a drive signal to the source of ultrasonic energy.

33. The apparatus of any of claims 20 to 32, wherein the signal acquisition and processing system is configured to run an algorithm specific to the endovascular wire type to estimate deflection of the active tip, when excited, and to estimate a tunnel diameter extending through the obstruction.

34. The apparatus of any of claims 20 to 33, wherein the signal acquisition and processing system is configured: to monitor modulation of transmitted signals and to control voltage applied to the source of ultrasonic energy automatically to compensate for background energy loss encountered in the wire as the active tip approaches the obstruction; and to distinguish the background energy loss from additional energy loss as the active tip passes through the obstruction and to compensate for the background energy loss to sustain displacement at the active tip.

35. The apparatus of any of claims 20 to 34, further comprising a manual override that is operable to modulate power output of the source of ultrasonic energy.

36. The apparatus of any of claims 20 to 35, wherein the signal acquisition and processing system is configured to compare the captured operational parameters with stored data that characterises known obstructions, and to characterise the obstruction with reference to that comparison.

37. The apparatus of any of claims 20 to 36, wherein the signal acquisition and processing system further comprises an output to a user interface and/or to an external data acquisition system.

38. The apparatus of any of claims 20 to 37, wherein the signal acquisition and processing system further comprises an input from a user interface and/or from an external data network.

39. The apparatus of any of claims 20 to 38, wherein the signal acquisition and processing system is configured to modify or change a control algorithm in response to variation in the operational parameters of the apparatus arising from interaction of the active tip with an obstruction in use.

40. The apparatus of any of claims 20 to 39, wherein the signal acquisition and processing system is configured to output data to an external data network and to receive data from the network in response and, on receiving data from the network, to modify or change a control algorithm accordingly.

41. The apparatus of claim 40, wherein the signal acquisition and processing system is configured to output data to the network representing variation in the operational parameters of the apparatus arising from interaction of the active tip with an obstruction in use.

42. The apparatus of any preceding claim, wherein the source comprises a transducer vibrating at a frequency of between 20 kHz and 60 kHz.

43. The apparatus of claim 42, wherein the transducer vibrates at a frequency of between 35 kHz and 45 kHz.

44. The apparatus of claim 43, wherein the transducer vibrates at a frequency of between 37 kHz and 43 kHz.

45. The apparatus of claim 44, wherein the transducer vibrates at a frequency substantially equal to 40 kHz.

46. The apparatus of any preceding claim, further comprising a follow-on endovascular diagnostic or therapeutic device that is transportable distally along the wire into a patient's vasculature after uncoupling the source from the wire.

47. A communication system comprising the apparatus of any preceding claim in data communication with a computer system that is arranged to receive data from the apparatus, to optimise and update control algorithms accordingly and to output the optimised, updated control algorithms to the apparatus.

48. The communication system of claim 47, wherein two or more such apparatuses are in data communication with the computer system, which is arranged to optimise control algorithms in accordance with data received from multiple procedures performed using the apparatuses and to output the optimised, updated control algorithms to the apparatuses.

49. An elongate endovascular wire for crossing through an obstruction in a blood vessel, the wire comprising a coupling for, in use, transmitting ultrasonic energy along the wire from a source of the ultrasonic energy to an active tip at a distal end of the wire, wherein the coupling is arranged to couple the source to the wire at any of a plurality of discrete operational positions along the length of the wire for said transmission of ultrasonic energy to the active tip.

50. An elongate endovascular wire for crossing through an obstruction in a blood vessel, the wire comprising: a coupling for, in use, transmitting ultrasonic energy along the wire from a source of the ultrasonic energy to an active tip at a distal end of the wire; and a cutting device on the coupling or on the wire for cutting through or scoring the wire to sever the coupling from a portion of the wire extending distally from the cutting device.

51. The wire of claim 50, wherein the cutting device comprises at least one blade that is movable transversely relative to a longitudinal axis of the wire.

52. An elongate endovascular wire for crossing through an obstruction in a blood vessel, the wire comprising: a coupling for, in use, transmitting ultrasonic energy along the wire from a source of the ultrasonic energy to an active tip at a distal end of the wire; wherein the coupling comprises: a screw connector that is fixed to a proximal end of the wire; and a rotary sleeve that, in a first longitudinal position, is engaged with the screw connector to turn the screw connector into engagement with the source of the ultrasonic energy and that is then movable into a second longitudinal position to decouple the sleeve from the screw connector and the wire.

53. The wire of claim 52, wherein the first longitudinal position is disposed proximally with respect to the second longitudinal position.

54. An elongate endovascular wire for crossing through an obstruction in a blood vessel, the wire comprising a proximal section; a distal tip section of smaller diameter than the proximal section; and a distally-tapering intermediate section extending between the proximal and distal tip sections, wherein the wire is unsleeved over substantially its entire length.

55. The wire of claim 54, comprising at least one welded join between at least two of said sections.

56. The wire of claim 54 or claim 55, wherein the distal tip section comprises a bulbous distal extremity.

57. The wire of any of claims 54 to 56, wherein the distal tip section comprises a distal portion that is offset angularly with respect to a longitudinal axis of the wire.

58. The wire of any of claims 54 to 57, wherein a marker band encircles at least the distal tip section.

59. The wire of any of claims 54 to 58, having an overall length of between 500 mm and 2500 mm.

60. The wire of any of claims 54 to 59, wherein the proximal section is of uniform diameter along its length.

61. The wire of claim 60, wherein the diameter of the proximal section is from 0.014″ to 0.035″ (about 0.36 mm to about 0.89 mm).

62. The wire of any of claims 54 to 61, wherein the proximal section of the wire has a length of from 500 mm to 2000 mm.

63. The wire of any of claims 54 to 62, wherein the length of each of said sections is a function or multiple of λ/4, where λ is a driving frequency that results in resonance in the wire.

64. The wire of any of claims 54 to 63, wherein the distal section is tapered or of a constant diameter along its length.

65. The wire of claim 64, wherein the distal section has a diameter of from 0.003″ to 0.014″ (about 0.08 mm to about 0.36 mm).

66. Endovascular apparatus comprising the wire of any of claims 49 to 65 and a source of ultrasonic energy coupled to the wire.

67. An activation unit for conveying ultrasonic energy into an elongate endovascular wire, the unit comprising: a source of the ultrasonic energy; and a coupling that is arranged to couple the source to the wire at any of a plurality of discrete operational positions along the length of the wire.

68. The unit of claim 67, wherein the coupling is arranged to enable relative longitudinal movement between the source and the wire when moving between the operational positions.

69. The unit of claim 68, wherein the coupling is arranged to enable said relative longitudinal movement while remaining attached to the wire.

70. The unit of claim 68, wherein the coupling is arranged to enable said relative longitudinal movement by being removed from and reattached to the wire.

71. The unit of any of claims 67 to 70, wherein the source comprises a transducer vibrating at a frequency of between 20 kHz and 60 kHz.

72. The unit of claim 71, wherein transducer vibrates at a frequency of between 35 kHz and 45 kHz.

73. The unit of claim 72, wherein transducer vibrates at a frequency of between between 37 kHz and 43 kHz.

74. The unit of claim 73, wherein transducer vibrates at a frequency of between or substantially equal to 40 kHz.

75. The unit of any of claims 67 to 74, further comprising a visual, haptic and/or audio user interface.

76. A method of mitigating an obstruction in a passageway, the method comprising: coupling a source of ultrasonic energy to an elongate wire at any of a plurality of discrete operational positions along the length of the wire; and transmitting ultrasonic vibrations from the source along the wire to vibrate an active tip at a distal end of the wire in contact with the obstruction.

77. The method of claim 76, comprising effecting relative longitudinal movement between the source and the wire when moving between the operational positions.

78. The method of claim 77, comprising effecting said relative longitudinal movement while the source remains attached to the wire.

79. The method of claim 78, comprising moving the wire longitudinally while holding the source substantially stationary.

80. The method of claim 77, comprising effecting said relative longitudinal movement by removing the source from the wire and reattaching the source to the wire at a different longitudinal position.

81. The method of claim 80, comprising moving the source longitudinally while holding the wire substantially stationary.

82. The method of claim 80 or claim 81, comprising removing the source from the wire or attaching the source to the wire by relative movement between the source and the wire in a lateral direction transverse to a longitudinal axis of the wire.

83. The method of any of claims 76 to 82, comprising clamping the wire when the source is at any of the operational positions.

84. A method of mitigating an obstruction in a passageway, the method comprising: transmitting ultrasonic vibrations from a source of ultrasonic energy along an elongate wire to vibrate an active tip at a distal end of the wire in contact with the obstruction; and delivering a follow-on diagnostic or therapeutic device distally along the wire.

85. The method of claim 84, comprising removing the source from the wire before delivering the follow-on device along the wire.

86. A method of mitigating an obstruction in a passageway, the method comprising: transmitting ultrasonic vibrations along a wire from an electrically-driven source coupled with the wire to vibrate an active tip at a distal end of the wire in contact with the obstruction; and sensing the response of the vibrating wire to interaction with the obstruction as the active tip encounters and crosses through the obstruction.

87. The method of claim 86, further comprising comparing sensed data representing the response of the vibrating wire with stored data representing the response of a corresponding vibrating wire to interaction with a known obstruction.

88. The method of claim 86 or claim 87, further comprising, in response to sensing the response of the vibrating wire, adjusting amplitude or frequency of the ultrasonic vibrations transmitted to the active tip along the wire.

89. The method of any of claims 86 to 88, comprising sensing amplitude of vibration of the wire and controlling the source to maintain a resonant frequency in the wire.

90. The method of any of claims 86 to 89, comprising modifying or changing a control algorithm in response to variation in the response of the vibrating wire.

91. The method of any of claims 86 to 90, comprising: outputting data to an external data network; receiving data from the network in response; and, on receiving data from the network, modifying or changing a control algorithm accordingly.

92. The method of claim 91, comprising: outputting data to the network representing variation in the response of the vibrating wire.

93. The method of any of claims 86 to 92, comprising: outputting data to an external computer system; in the external computer system, optimising and updating a control algorithm in accordance with that data; outputting the optimised, updated control algorithm from the external computer system; and using the optimised, updated control algorithm to control vibration of the wire.

94. The method of claim 93, wherein the computer system optimises the control algorithm in accordance with data received from multiple procedures.

95. A method of characterising an obstruction in a blood vessel, the method comprising comparing measured data, representing the response of a pre-delivered vibrating endovascular wire to interaction with the obstruction, with stored data representing the response of a corresponding vibrating endovascular wire to interaction with a known obstruction.

96. The method of claim 95, comprising adjusting vibration of the pre-delivered endovascular wire in response to the comparison between the measured data and the stored data.

97. The method of claim 95 or claim 96, comprising the preliminary steps of selecting an endovascular wire of a particular type and selecting an algorithm specific to that type of endovascular wire for use in determining the response of the selected wire to an obstruction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0154] In order that the invention may be more readily understood, reference will now be made, by way of example, to the accompanying drawings in which:

[0155] FIG. 1 is a schematic view of a system in accordance with the invention, including a compact housing unit;

[0156] FIG. 2 is a perspective view of the system shown in FIG. 1;

[0157] FIG. 3 is a schematic side view that shows another embodiment in which the ultrasonic generator is housed in a separate unit;

[0158] FIG. 4 is a diagram that shows the analog and digital data flow in the system;

[0159] FIG. 5 is a flow chart showing a preferred method of operation of the system;

[0160] FIG. 6 is a diagram that shows the operational functional flow of the system;

[0161] FIG. 7 is a flow chart showing the operation of a semi-autonomous and intelligent control system of the invention;

[0162] FIGS. 8a, 8b and 8c are schematic side views that illustrate the active wire assembly prior to connection to the horn, then connected to the horn using an appropriate mechanical coupling method, and decoupled from the main housing and proximal assembly by means of a decoupling method;

[0163] FIGS. 9a, 9b and 9c are sectional views that show an embodiment of a connection method;

[0164] FIGS. 10 and 11 are enlarged partial sectional views that show other embodiments of a linear push-and-screw connection method;

[0165] FIG. 12 is an enlarged partial sectional view that shows another embodiment of a connection method that employs mechanical locking;

[0166] FIG. 13 is an enlarged partial sectional view that shows an embodiment of a screw connection method that employs a radial release mechanism;

[0167] FIG. 14 shows a coupling method with proximal interlocking features on a transmission member;

[0168] FIG. 15 is a perspective view of a wire release mechanism that fractures or cuts the active wire between opposed blades;

[0169] FIG. 16 is a schematic view of a wire release mechanism that fractures or cuts the active wire between blades carried by roller-actuated gears;

[0170] FIG. 17 is a schematic view of a wire release mechanism that fractures or cuts the active wire between blades carried by linearly-actuated gears;

[0171] FIGS. 18a to 18c are schematic detail side views that show a method of fracturing an active wire;

[0172] FIG. 19 is a sectional side view of a proximal sub assembly that can measure displacement of the active wire as it traverses;

[0173] FIG. 20 is a schematic side view that shows the housing unit supported by an automated drive system;

[0174] FIG. 21 is a sectional side view of an embodiment in which the acoustic horn and transducer assembly have a hollow port through the full length of the assembly, with an internal wire connect/disconnect mechanism or locking collet;

[0175] FIG. 22 is a sectional side view of an embodiment in which the acoustic horn/transducer assembly of the activation unit has a hollow port through most of the body length of the assembly but the wire exits the assembly through a side port, enabling the activation unit to lock along the wire through a mechanism in the transducer tip;

[0176] FIGS. 23a to 23c are schematic side views acoustic horn/transducer assembly that show a further method for connecting the active wire;

[0177] FIGS. 24a to 24c are schematic side views of a variant of the arrangement shown in FIGS. 23a to 23c, where the active wire extends through the full length of the horn/transducer assembly;

[0178] FIGS. 25a to 25c are schematic side views, and FIG. 25d is a schematic perspective view, of a further variant of the arrangement shown in FIGS. 23a to 23c, where the active wire exits the horn/transducer assembly through a side port;

[0179] FIGS. 26a to 26c are schematic side views, and FIG. 26d is a schematic detail view, of a variant of the arrangement shown in FIGS. 25a to 25c, where the active wire can be removed laterally from the horn/transducer assembly in a direction transverse to the longitudinal axis of the active wire;

[0180] FIGS. 27a to 27c are schematic side views showing the housing unit positioned at various longitudinal positions along a proximal portion of the active wire protruding from a patient's body;

[0181] FIGS. 28 to 31 are exploded perspective views of various collet arrangements for securing the active wire to a horn/transducer assembly;

[0182] FIGS. 32a and 32b are enlarged perspective views of the collet shown in FIG. 30;

[0183] FIG. 33 is a schematic sectional side view of a further collet arrangement;

[0184] FIGS. 34a and 34b are schematic side views of a further active wire of the invention;

[0185] FIG. 35 is a schematic side view of an active wire of the invention;

[0186] FIG. 36 is a perspective view of a variant of the invention in which the active wire has an angularly-offset distal end portion;

[0187] FIG. 37 is a schematic side view of an active wire having an angularly-offset distal end portion like that shown in FIG. 35;

[0188] FIGS. 38a and 38b are schematic side views of a further active wire of the invention, including marker bands;

[0189] FIG. 39 is a schematic side view of another active wire of the invention;

[0190] FIGS. 40 and 41 are schematic side views of other active wires of the invention, each having an enlarged, bulbous distal tip; and

[0191] FIGS. 42a to 42c are schematic side views that show a wire of the invention being used initially as an active wire to cross a lesion and then as a guide wire to transport a follow-on device to the lesion.

DETAILED DESCRIPTION OF THE INVENTION

[0192] FIG. 1 includes a schematic view of a compact housing unit 2. In this configuration the compact housing unit 2 includes an ultrasonic generator 4, an ultrasonic transducer 6 and an acoustic horn 8. The housing unit 2 is connected to an available electricity supply via a power cable 10.

[0193] FIG. 1 also shows an active crossing wire assembly 12 that can be connected to the housing unit 2. The active wire assembly 12 comprises a flexible transmission member in the form of a wire 14.

[0194] A proximal section of the active crossing wire assembly 12 includes an attachment module 16 and a decoupling module 18 and provides for one or more additional ports 20. A distal section of the active crossing wire assembly 12 is also shown, including an enlarged view 22 of the distal tip 24 of the wire 14. In this example, the distal tip 24 is bulbous.

[0195] When coupled and activated, the transducer 6 and the wire 14 vibrate with sufficient amplitude at a proximal end that the distal end of the wire 14 is able to effect crossing of a lesion by virtue of energy transmitted along the wire 14.

[0196] The wire 14 may, for example, be more than 2 m in length. For example, access to a lesion in or through the foot may involve the wire 14 travelling a distance of typically 1200 mm to 2000 mm within the vasculature depending on whether an ipselateral or contralateral approach is chosen. In this respect, a wire 14 tapering distally to a fine wire at its tip can navigate to the pedal arteries and around the pedal arch between the dorsal and plantar arteries. However, the invention is not limited to pedal or other peripheral applications and could, for example, be used in coronary applications, where the ability of the wire 14 to navigate to and excavate tortuous small diameter arteries is also beneficial.

[0197] FIG. 2 also shows the compact housing unit 2 and the active crossing wire assembly 12. Also shown are user input controls 26 and a means for providing feedback to a user, exemplified here by a display 28.

[0198] The wire 14 may be coupled to the transducer 6 via the acoustic horn 8 or may instead be coupled directly to the transducer 6, in which case the acoustic horn 8 may be omitted. For example, referring to FIG. 2, an attachment module 16 may attach the wire 14 directly to the transducer 6 within the body of the housing unit 2, beneath the display 28 of the housing unit 2.

[0199] FIG. 3 shows a variant in which the ultrasonic transducer 6 and the acoustic horn 8 are integrated into the compact housing unit 2 whereas the ultrasonic generator and circuitry 4 are housed in a separate generator housing unit 30. In this instance, the housing unit is connected to the generator housing unit via a connector cable 32.

[0200] FIG. 4 illustrates the components and elements of the system and the flow of data through the system, including communications. A controller within the housing unit controls the ultrasonic generator to generate a signal that is converted to ultrasonic energy by the transducer. The ultrasonic energy is fed via the optional acoustic horn to the active wire that navigates the vasculature and crosses a blockage such as a chronic total occlusion (CTO).

[0201] Feedback from the active wire is received by a feedback receiver, amplified by an amplifier and filtered by a series of bandpass filters before passing through analog-to-digital conversion to generate feedback data that is sent to a processor. The controller controls a preferably wireless communications system, for example using a Wi-Fi network or a Bluetooth connection, to receive data from the processor and to communicate that data from the housing unit to local storage and/or to the cloud. FIG. 4 also shows means in the housing unit for providing feedback to a user, such as the aforementioned display and/or a haptic feedback system.

[0202] Turning next to FIG. 5, this shows that the system can be used in a passive or active mode. Initially, the active wire assembly is introduced into an artery and the distal tip of the wire is navigated to a target blockage, which may be calcified or diffuse. If the blockage can be crossed without ultrasound activation of the wire, the system is left in passive mode and the blockage is crossed. Conversely if the blockage cannot be crossed without ultrasound activation of the wire, the active wire assembly is connected to the housing unit and is then activated ultrasonically to effect crossing.

[0203] Once the blockage has been crossed, the active wire assembly is disconnected from the housing unit. The wire is then ready to serve as a guide wire to facilitate the introduction and navigation of follow-on therapeutic or diagnostic devices as required.

[0204] FIG. 6 further summarises the operation of the system and the procedure and the decision points associated with use of the system.

[0205] FIG. 7 is a flow chart that summarises semi-autonomous control of the system. In practice, the system can gather data input by a user prior to operation, such as the anticipated lesion type and its anatomical location. This data can be coupled with real-time inputs as the active wire crosses the lesion, such as power requirements.

[0206] Automatically, the system can sense changes in frequency and power and using on-board algorithms can optimise the performance of the active wire. This information can be fed back to the user via haptic, visual or audio means, such as the display on the housing unit.

[0207] The variation in the magnitude of the input and control parameters of current, voltage and frequency with the characteristic capacitance of the converter provide a matrix of measurements and controls that are used to determine the power required and to characterise the lesion being crossed.

[0208] As the input is kept constant, a variation in current is indicative of the strain energy absorbed or the damping effect along the wire and especially the distal tip of the wire as it crosses the lesion at the sustained frequency of the system.

[0209] Monitoring current allows behaviour of the wire to be interpreted and modulation of the voltage allows for the amplification of power and the recovery of frequency as the wire actuates the contact surface and reduces the offset. This array of measurements in the small-frequency range then allows for gross characterisation of the composition of the lesion, be it calcified, fibrous or gelatinous over its entire length.

[0210] These interpolated characteristic components are not absolute characteristics of the lesion but are indicative of its composition and consistency, such as: calcific, rigid compacted or disaggregated; or compacted calcific particulate versus non-compacted fibrotic versus hard or soft gelatinous. These characteristics can be indicative of the nature and severity of the lesion and inform the clinician of the optimal therapy to consider.

[0211] The system can also both transmit this data and receive optimised performance algorithms via existing wireless or wired communication networks.

[0212] FIGS. 8a to 8c show a method of attachment, where initially the active crossing wire assembly 12 and the compact housing unit 2 are not mechanically coupled together. In this configuration, as shown in FIG. 8a, the wire 14 can be used as a conventional guidewire in its passive mode i.e. without ultrasonic activation.

[0213] FIG. 8b shows how, if and when required, the active crossing wire assembly 12 can be mechanically coupled to the housing unit 2. In particular, engagement of the attachment module 16 with a distal end of the housing unit 2 effects alignment and mechanical coupling of a proximally-protruding end portion of the wire 14 within a central bore 34 at the distal end of the acoustic horn 8. Once coupled in this way, ultrasonic vibrations can be transmitted from the acoustic horn 8 along the wire 14 to cross through a lesion.

[0214] After crossing the lesion, FIG. 8c shows the wire 14 now decoupled from the acoustic horn 8 following operation of the decoupling module 18. Specifically, opposed blades of the decoupling module 18 are brought together around the wire 14 to break or cut the wire 14. The compact housing unit 2 and the proximal section of the active crossing wire assembly 12 can now be removed from the wire 14, hence separating all other components from the wire 14.

[0215] FIGS. 9a to 9c show one embodiment of a proximal section of the active crossing wire assembly 12, in particular the attachment module 16. In this embodiment, the wire 14 is mechanically bonded 36 to a screw connector 38 that comprises an enlarged head and a proximally-extending male thread. The head of the screw connector 38 is gripped and engaged by a surrounding sleeve 40 with a longitudinally-stepped shape. A narrower tubular distal end of the sleeve 40 provides strain relief around the wire 14.

[0216] The sleeve 40 and the head of the screw connector 38 are constrained to turn together about the central longitudinal axis of the wire 14. For example, the cross-sectional views of FIG. 9c show that the head of the screw connector 38 may have various rotationally-asymmetrical external shapes 42 that complement, and interlock with, corresponding internal shapes of the sleeve 40. However, relative axial movement is possible between the sleeve 40 and the head of the screw connector 38.

[0217] The acoustic horn 8 is shown within the housing unit 2. The acoustic horn 8 comprises a central distal threaded bore 44 that is opposed to, and complements, the male thread of the screw connector 38.

[0218] When coupled as shown in FIG. 9b, the proximal section of the active crossing wire assembly 12 axially push-connects to the housing unit 2 via click connectors 46, 48. The click connectors 46 of the housing unit 2 are integral with an axially-retractable tube 50 that is biased distally by springs 52. Retraction of the tube 50 against the bias of the springs 52 allows the male thread of the screw connector 38 to be screwed into the bore 44 of the acoustic horn 8 by turning the sleeve 40, which applies torque to the head of the screw connector 38. Once the thread of the screw connector 38 is fully engaged with the bore 44 of the acoustic horn 8, the sleeve 40 is released and the springs 52 acting on the tube 50 then push the proximal section of the active wire assembly 12, comprising the sleeve 40, clear of the wire 14 and the acoustic horn 8.

[0219] FIG. 10 shows another embodiment of the screw connector, in which a spring mechanism 54 is located in the proximal section of the active wire assembly 12. The screw connector 38 and the wire 14 are shown as before. The active crossing wire assembly 12 and the housing unit 2 are coupled via snap-fit formations 56. FIG. 11 shows a variant of the arrangement of FIG. 10, further comprising a distally-extended snap fit section 58.

[0220] FIG. 12 shows a screw connector 38 comprising a manual push-screw-pull slotted entry and lock system 60, best appreciated here in the perspective detail view of the distal end of the housing unit 2. The proximal section of the active crossing wire assembly 12 comprises an inwardly-facing lug 62 that initially aligns with an external slot 64 formed in the distal end of the housing unit 2. After the lug 62 travels proximally along the slot 64, the proximal section of the active crossing wire assembly 12 is turned about the central longitudinal axis of the wire 14. This brings the lug 62 into alignment with a notch 66 formed in the distal end of the housing unit. The lug 62 engages distally with the notch 66 to lock the proximal section of the active crossing wire assembly 12 to the distal end of the housing unit 2 as shown in the sectional view of FIG. 12.

[0221] FIG. 13 shows a radial connector grip-and-release mechanism 68. The screw connector 38 is held by a radial retainer 70 that is initially held in a radially-inward position by an axially-movable sleeve 72. The retainer 70 transmits torque from the sleeve 72 to the screw connector 38 to screw the male thread of the screw connector 38 into the bore 44 of the acoustic horn 8. Once the screw connector 38 is fully engaged with the acoustic horn 8, sliding the sleeve 72 proximally over the distal section of the housing unit 2 frees the radial retainer 70 to spring radially away from the screw connector 38. This decouples the wire 14 from the sleeve 72 and from the remainder of the proximal section of the active wire assembly 12.

[0222] FIG. 14 shows a connection arrangement in which the proximal end of the wire 14 has a series of geometric features such as circumferential ridges 74 that are embedded within and interlock with a coupling connector 76. The coupling connector 76 has a male screw thread at its proximal end that is engaged with the threaded bore 44 at the distal end of the acoustic horn 8.

[0223] Turning next to FIGS. 15 to 17, these drawings shows show various convenient arrangements for breaking the wire 14 to free the wire 14 from the housing unit 2 after successfully crossing a lesion.

[0224] FIG. 15 shows the internal mechanism of a squeeze-action wire-break system 76. A surrounding housing has been omitted for clarity. Here, the wire 14 supports a pair of sharpened blades 78 that are opposed about the wire 14. The blades 78 are integral with resilient levers 80 that, when squeezed together, pinch and sever the wire 14 between the blades 78.

[0225] FIGS. 16 and 17 show blades 82 attached to respective meshed gears 84, one gear each side of the wire 14. Opposed rotation of the gears 84 brings the blades 82 together to pinch and cut the wire 14. In FIG. 16, the gears 84 are rotated by a user rolling an exposed side of at least one of the gears 84, which in turn rotates the other gear. Conversely, in FIG. 17, a linear push-button mechanism 86, when depressed, turns one of the gears which in turn rotates the other gear.

[0226] FIGS. 18a to 18c show another approach to breaking the wire. This involves creating a defect of sharpness and applying a cyclical load that causes fatigue.

[0227] FIG. 18a shows the wire 14 in its original form with a smooth outer surface, as it will be used to cross a lesion. FIG. 18b shows the wire 14 scored or notched 88, for example with a blade, after crossing the lesion. On then being vibrated by the transducer with sufficient energy at an appropriate frequency, the wire 14 will quickly fracture as shown in FIG. 18c. This is due to propagation of a crack 90 across the diameter of the wire 14 from the transverse score or notch 88, which serves as a point of weakness or stress concentration to initiate the crack 90.

[0228] This failure mechanism is apt to be used to detach a crimped nitinol wire by exploiting ultrasonic energy and the intrinsic toughness of the nitinol. Scoring the surface of the wire 14 creates a scratch defect that concentrates stress. As the critical crack length for nitinol is relatively low, ultrasonic loading at high amplitude will cause the wire 14 to break there by creating a perfectly plane strain surface failure.

[0229] FIG. 19 shows a measuring attachment 92 that can measure and display the distance over which the wire 14 and a proximal sheath 94 travel longitudinally with respect to a housing 96 and a foresheath 98. In this example, a linear graduated scale is etched, printed or moulded into the proximal sheath 94. An attachment 92 such as this allows the distance of travel of the distal tip of the wire 14 within the vasculature to be measured conveniently at the proximal end of the wire 14.

[0230] FIG. 20 shows a linear drive system 100 that can cradle or otherwise hold the housing unit 2, and that can advance and retract the housing unit 2 longitudinally as shown. For this purpose, the drive system 100 includes a drive mount 102 and a unit 104 comprising a motor, an encoder and a force sensor unit. The drive system 100 facilitates autonomous or robotic insertion and navigation of the wire 14 through the vasculature and across a lesion.

[0231] FIG. 21 shows an active wire 14 passing through a threaded ultrasonic transducer and horn assembly 106. A locking collet 108 has a tapped section that screws onto a thread to close a spring collet clamp 110. The spring collet clamp 110 clamps to the wire 14 over a long interface. This configuration allows for the proximal end of the wire 14 to be fed through the acoustic horn/transducer assembly 106, and to be connected to the assembly 106 at any of multiple points along the length of the wire 14.

[0232] FIG. 22 shows a variant of the arrangement of FIG. 21, in which the acoustic horn/transducer assembly 106 has a hollow port through most but not all of the body length of the assembly 106. In this instance, the wire 14 exits through a side port 112, enabling this activation unit to lock at any of multiple points along the wire 14 through a mechanism in the distal tip of the assembly 106.

[0233] FIGS. 23a to 23c show an arrangement in which a proximal end of the wire 14 is received in a central distal bore 114 of the acoustic horn 8 within the housing 2. After inserting the wire 14 into the bore 114 as shown in FIG. 23a, a twist-lock mechanism 116 on the distal end of the housing 2 is turned to lock the wire 14 to the acoustic horn 8 as shown in FIG. 23b. The acoustic horn 8 can then feed ultrasonic energy into the wire 14 as shown. When there is no longer a need for ultrasonic activation of the wire 14, the wire 14 can be unlocked from the acoustic horn 8 by reversing the twist-lock mechanism 116 and can then be withdrawn longitudinally as shown in FIG. 23c.

[0234] FIGS. 24a to 26d illustrate various additional concepts relating to adjustable location activation. They show further arrangements in which an activation system comprising a housing 118 containing a transducer/horn 120 can slide and lock, or ‘slip and stick’, over the crossing wire 14 and so be coupled to the crossing wire 14 at any location along the proximal portion of the wire 14 outside the patient's body.

[0235] For this purpose, FIGS. 24a to 24c show a variant of the arrangement shown in FIGS. 23a to 23c, in which the central bore 114 in the transducer/horn 120 extends longitudinally through the housing 118 and opens out to both the distal and proximal ends of the housing 118. This allows the wire 14 to extend through and protrude from both ends of the housing 118 as shown in FIG. 24b, thus allowing the housing 118 to be repositioned longitudinally relative to the wire 14.

[0236] In this arrangement, the wire 14 is still inserted longitudinally into the distal end of the transducer/horn 120 as shown in FIG. 23a and is withdrawn longitudinally from the distal end of the transducer/horn 120 as shown in FIG. 23c. Again, a twist-lock mechanism 116 on the distal end of the housing 118 is turned to lock the wire 14 to the transducer/horn 120 as shown in FIG. 23b.

[0237] FIGS. 25a to 25d show that the wire 14 can emerge from the housing 118 through an opening other than a central opening 122 at the proximal end of the housing 118. In the example shown here, the wire 14 exits the transducer/horn 120 through a lateral port 124 that communicates with the central distal opening of the bore 34. The laterally-exiting part of the wire 126 extends from the port 124 to exit the housing 118 through a lateral opening aligned with the port 124. Thus, the wire 14 deflects from the central longitudinal axis of the transducer/horn 120 through an acute angle to exit the transducer/horn 120 laterally.

[0238] As before, the wire 14 is inserted longitudinally into the distal end of the transducer/horn 120 as shown in FIG. 23a and is withdrawn longitudinally from the distal end of the transducer/horn 120 as shown in FIG. 23c. Again, a twist-lock mechanism 116 on the distal end of the housing 118 is turned to lock the wire 14 to the transducer/horn 120 as shown in FIG. 23b.

[0239] In a further variant of the lateral-exit principle shown in FIGS. 25a to 25c, FIGS. 26a to 26d show an arrangement in which the wire 14 can be pulled laterally from (and optionally also inserted laterally into) the transducer/horn 120 within the housing 118. The wire 14 is received in a longitudinal slot 130 that can be closed and opened by turning pivotable jaws 128 of the acoustic horn 118 as shown in the detail view of FIG. 26d. When closed, the jaws 128 encircle and engage the wire 14 to couple the wire 14 to the transducer/horn 120. When opened by relative angular movement around the central longitudinal axis, the jaws 128 free the wire 14 from the transducer/horn 120 to exit the transducer/horn 120 through the slot 130. The housing 118 has a corresponding slot 132 that allows the wire to exit the housing 118 laterally to free the wire 14.

[0240] As excitation of the wire 14 is only required in the distal direction from the housing 118, damping materials in the housing 118 may prevent or damp excitation of the portion of the wire 14 that extends proximally from the housing 118 in the embodiments shown in FIGS. 24a to 26d. Various, typically elastomeric, materials can be used to effect damping such as a silicone seal or gasket. More generally, unwanted excitation may be damped by contact between the wire 14 and a wall of the housing 118 around a side port of the housing 118.

[0241] FIGS. 27a to 27c show that a physician can disconnect and reconnect the housing 118 at any location along the external proximal portion of the wire 14, allowing the wire 14 to be loaded and unloaded as required. As shown in FIG. 27c, the wire 14 can be marked at regular or irregular intervals 133 along its length that are characteristic of harmonics at an activation frequency of say 40 kHz, such as λ/2 and λ/4.

[0242] The housing 118 can be released from the wire 14, relocated at specific longitudinal intervals and reconnected to the wire 14 multiple times as the wire 14 is fed in a forward or distal direction. In general, the housing 118 or the wire 14 may move relative to each other, allowing the physician to move the wire 14 to cross a lesion or to find a better location for the housing 118 at which to activate the wire 14. Removing the housing 118 from the wire 14 and later recoupling it to the wire 14 allows for other devices to be placed on or left on the wire 14 and for the wire 14 not to be moved in the course of a procedure, which greatly enhances the ease of use for the physician.

[0243] For example, the housing 118 can be hitched onto the wire 14 close to where the wire 14 enters an introducer sheath 135 and the patient's body 137, as shown in FIG. 27a. FIGS. 27b and 27c show other locations at which the housing 118 can be coupled to the wire 14. FIG. 27b shows the housing at an intermediate location between the introducer sheath 135 and the proximal end of the wire 14, whereas FIG. 27c shows the housing 118 at a proximal location at or adjacent to the proximal end of the wire 14.

[0244] Turning next to FIGS. 28 to 33, these drawings show various connector concepts whose primary objective is to achieve excellent acoustic coupling between the crossing wire and the rest of the system. In this respect, the transducer and the coupling method have to work in unison. In particular, the transducer, with coupling interface components optionally including an acoustic horn, is designed to resonate at the driving frequency of the system.

[0245] The transducer may, for example, be constructed from Grade 5 titanium or aluminium alloy or steel alloy with a step configuration. The shape and dimensions of the transducer are selected to achieve an amplification gain while ensuring that the system remains near to its operating resonant frequency. In addition, any modifications to a distal driving face of the transducer so as to accommodate a connector have to be considered and accounted for with regard to resonant response.

[0246] FIG. 28 shows a transducer 134 fitted with a double-taper collet 136 and a cap screw 138. The cap screw 138 has external formations to facilitate gripping and turning by a user.

[0247] The wire 14 enters through a central hole 140 in the cap screw 138 opposed to a countersunk base hole 142 in the distal face of the transducer 134. The wire 14 extends through the collet 136, which is interposed between the base hole 142 and the cap screw 138. The taper at the proximal end of the collet 136 complements the countersunk base hole 142. The cap screw 138 similarly receives and complements the taper at the distal end of the collet 136.

[0248] The collet 136 comprises a first pair of slits 144 at its proximal end and a second pair of slits 146 at its distal end. Each pair of slits 144, 146 extends longitudinally by more than half of the length of the collet 136. The slits 144, 146 of each pair are in mutually-orthogonal planes that intersect along the central longitudinal axis of the collet 136. The slits of the second pair 146 are rotated about the central longitudinal axis by 45° relative to the slits of the first pair 144.

[0249] Torque applied to the cap screw 138 advances the cap screw 138 to compress the collet 136 longitudinally. Consequently, the tapered ends cause, and the slits 144,146 allow, the collet 136 to compress radially to grip the wire 14. Advantageously, the collet 136 provides a substantially uniform loading pattern based upon uniform radial reduction and therefore uniform gripping of the wire 14, improving transmission of energy and fatigue life.

[0250] FIG. 29 shows a transducer 148 fitted with a single-taper male-threaded collet 150. The tapered proximal end of the collet 150 has orthogonal slits 152 like the collet 136 of FIG. 28. The collet 150 anchors the wire 14 within a complementary threaded bore 154 in the distal end of the transducer 148 when torque is applied to the collet 150 to advance the collet 150 along the bore 154. A complementary taper at the proximal base of the bore 154 then compresses the collet 150 radially to grip the wire 14.

[0251] FIG. 30 shows a variant of the arrangement shown in FIG. 29, in which the wire 14 extends through the full length of the transducer 148 from the distal end to emerge from the proximal end.

[0252] FIGS. 31, 32a and 32b show a transducer 156 with a double-tapered counter-locking wire release collet 158. The counter-locking system embodies the concept of mutual alignment and misalignment between twin longitudinally-split collet parts 160, 162 that can turn relative to each other about a common central longitudinal axis. When longitudinal slots 164 in the collet parts 160, 162 are misaligned as shown in FIG. 32a, the wire 14 is trapped within the collet 158. Conversely, when longitudinal slots 164 in the collet parts 160, 162 are aligned as shown in FIG. 32b, the wire 14 is freed from the collet 158 to be able to exit the collet 158 in a direction transverse to the central longitudinal axis of the collet 158.

[0253] Correspondingly, the cap screw 166 and the transducer 156 comprise slots 168 that can be aligned to free the wire 14 for lateral removal from the transducer 156, or for lateral insertion, in the manner of the embodiment shown in FIG. 26c.

[0254] The principle here is that the wire 14 may be released from the collet 158 as the clamping torque force is released and as the slots 164 in the parts 160,162 of the collet 158 are brought into alignment with each other and with the slots 168 in the cap screw 166 and the transducer 156. This is achieved by anchoring the proximal part 162 of the collet 158 to the transducer 156 and applying torque from the cap screw 166 to the distal part 160 of the collet 158 as the cap screw 166 is turned to release the clamping force.

[0255] The proximal part 162 of the collet 158 may, for example, locate onto a spline formation of the transducer 156 to align and lock it from rotating. The distal part 160 of the collet 158 may have facets with which the cap screw 166 can mate to turn the distal part 160 relative to the proximal part 162 to an extent necessary to release the wire 14.

[0256] The collets shown in these embodiments may include an internal counter-taper to optimise the land length over which the wire 14 is gripped. This advantageously limits the point loading on the wire 14 and possible consequent micro-structural damage that could otherwise promote the formation of microstructural defects.

[0257] FIG. 33 shows an internal expanding collet 168 housed in a head of a transducer 170. In this embodiment, the collet 168 is integrated into the transducer 170 and so is integral to the device itself. A wire 14 extends through the full length of the collet 168 and protrudes distally and proximally from the transducer 170.

[0258] The transducer 170 shown in FIG. 33 has a tubular body 172 that surrounds the collet 168. The collet 168 has an enlarged distal head 174 that protrudes from the distal end of the body 172 and has a diameter greater than the internal diameter of the body 172. Inclined ramp surfaces 176 on a proximal side of the head 174 bear against the distal end of the body 172.

[0259] A torque screw 178 is disposed at the proximal end of the body 172. An annular backing nut 180 and a piezo stack 182 are sandwiched between the torque screw 178 and the body 172.

[0260] The collet 168 has a threaded proximal part in threaded engagement with the torque screw 178. The torque screw 178 therefore couples the collet 168 and hence the wire 14 to the transducer 170 to transmit ultrasonic energy from the transducer 170 into the wire 14. Moreover, turning the torque screw 178 draws the collet 168 proximally into the body of the transducer 170. As the collet 168 moves proximally relative to the body 172, the inclined ramp surfaces 176 of the enlarged distal head 174 bear against the distal end of the body 172 and cause the collet 168 to clamp radially onto the wire 14.

[0261] FIGS. 34a and 34b show a wire 14 that has a substantially straight proximal section 184, a distally-tapering intermediate section 186 and a substantially straight distal excavating section 188 for crossing a lesion. By virtue of the taper of the intermediate section 186 between them, the distal section 188 has a smaller diameter than the proximal section 184. For example, the proximal section 184 may have a diameter of 0.43 mm and the distal section 188 may have a diameter of 0.25 mm. As the intermediate section 186 may extend over a metre in length, the taper between the proximal and distal sections 184, 188 is very slight and so is greatly exaggerated in these drawings.

[0262] The overall geometry of the wire including its nominal diameter and length are determined by the characteristic speed of sound in the material of the wire. This characteristic is determined for the materials chosen for the transducer and the wire. The dimensions of the straight and tapered sections of the wire are machined at functional intervals of wavelength.

[0263] Where nitinol materials are chosen, λ, λ/2 and λ/4 are determined to be 168 mm, 84 mm and 42 mm in this example. The chosen frequency will produce harmonics along the length of the wire and the loading of the tip of the wire will assist in establishing standing waves for non-characteristic lesions.

[0264] The distal section 188 can be tapered or can be uniform in diameter along its length and the harmonics can be λ or at least λ/4. The system can produce harmonics over a range.

[0265] As the goal of the activated wire 14 is to excavate a lesion, dimensions are optimised with the purpose of excavating as great a volume as possible at a given waveform. In this respect, FIG. 34b shows that the distal section 188 of the wire 14, once activated, moves in a primary longitudinal mode, moving in and out, and also in a radial direction which maps out and excavates a greater volume at the distal end through the longitudinal movement of the wire 14. The distal section 188 of the wire 14 is also seen to move in other modes through lateral and undulating movements under the resonant wave and secondary modes of differential harmonics, dependent on the activating frequency and also the length of the distal section 188.

[0266] FIG. 35 exemplifies how a wire 14 may be fabricated from sections welded together end-to-end. In this embodiment, the proximal section 184 is machined as a standard diameter to provide for amplification as well as to provide a standard connection for a proximally-loaded activation device. The proximal section 184 serves as a shaft that can be welded at a join 190, circled in FIG. 35, to one of a selection of different-diameter wires that may have custom distal ends and tips. This beneficially reduces the requirement to hold stock of various wire diameters as sections of a few different wire diameters may be assembled to produce wires of many required configurations. As the welded join 190 of the wire 14 is at a location of low stress, the loads applied to the join 190 in the course of activation will not lead to catastrophic fatigue failure.

[0267] Moving on to FIGS. 36 and 37, these drawings show a wire 14 that is formed or shaped to have an angularly-offset distal excavating section for crossing a lesion. In this embodiment, the distal section is not straight but is angled by virtue of a heat-set shaped tip 192. The dimensions of the tip 192 are optimised to provide improved performance in terms of steering to a lesion and excavation of the lesion. In particular, the angle of the tip 192 relative to the longitudinal axis of the distal section and the length of the tip 192 determine the ability of the wire 14 to turn into a specific side-branch artery. The angle and the length of the tip 192 also affect the manner in which the wire 14, once activated, will excavate a section of stenosed material

[0268] If the dimensions of the tip 192 are characteristic of a harmonic, e.g. λ/8 or about. 22 mm in length, the wire 14 will open out a significantly larger tunnel in a lesion than say a 25 mm tip section. The amplitude of the waveform and the number of times the distal section of the wire 14 is passed through a calcific section will determine the diameter of the tunnel that is excavated.

[0269] If the angle of the tip 192 is too great, it will create a larger lever arm and so could fatigue the wire 14 excessively; conversely if the angle of the tip 192 is too small, then the wire 14 may not be steerable effectively. In this respect, FIG. 37 shows that the tip 192 may be offset from the longitudinal axis of the wire 14 by about 15° to 45°, allowing the tip 192 to disrupt and excavate a greater volume of a lesion. The tip 192 is suitably heat-treated, for example at over 500° C. for less than 10 minutes, in order to create a microstructure that is reliably resistant to crack propagation and hence to fatigue.

[0270] FIGS. 38a and 38b show how visibility of the location of the wire 14 in the patient's body may be enhanced by the use of marker bands 194, for example of gold. Such marker bands 194 may, for example, be fixed at locations close to (for example, about 3 mm from) the distal tip 196 of the wire 14 and also from the distal end of the proximal section 184, just before the start of the tapered intermediate section 186. The marker bands 194 are placed at locations of minimal load in use of the wire 14. This minimises the possibility that the marker bands 194 could become detached or that the wire 14 could fail at those locations. The marker bands 194 are apt to be flush-fitted into circumferential grooves that are ground around the wire 14.

[0271] FIG. 39 shows a variant in which the distal tip 196 of the wire 14 is rounded, with no sharp transitions. By way of example, in this instance the proximal section 184 may be 1800 mm long, the tapered intermediate section 186 may be 84 mm long and the distal section 188 may be 10 mm long. Again, marker bands 194 encircle the wire 14 close to the distal tip 196 of the wire 14 and the distal end of the proximal section 184.

[0272] FIGS. 40 and 41 show other variants of the wire 14 that each have a bulbous distal tip 198, which is rounded to avoid sharp transitions. The bulbous tip 198 may, for example, be 3 mm to 4 mm in length and may have a diameter of just over 0.4 mm.

[0273] Apart from its bulbous tip 198, the wire shown in FIG. 40 is otherwise analogous to the wire 14 shown in FIG. 39.

[0274] Again, the wires 14 shown in FIGS. 40 and 41 have circumferential marker bands 194 that may be flush-fitted into circumferential grooves ground around the wire 14. Conveniently, as shown, the bulbous tip 198 may be encircled by one of the marker band 194.

[0275] In the example shown in FIG. 41, the wire has a proximal portion that comprises a straight section 200 and a distally-tapering section 202. The straight section 200 may have a textured surface as shown, to improve engagement with an activation device.

[0276] The proximal portion is welded to an intermediate portion that constitutes most of the length of the wire 14. The intermediate portion also comprises a straight section 204 and a short distally-tapering section 206. A marker band 194 is shown encircling the straight section 204 close to the distally-tapering section 206 of the intermediate portion 194. Finally, a short, narrow distal section 208 extends distally from the intermediate portion 186 to the bulbous tip 198.

[0277] Turning finally to FIGS. 42a to 42c, these schematic views illustrate how the wire 14 can be used initially as an active wire to cross a lesion 210 and then as a guide wire to transport a follow-on diagnostic or therapeutic device 214 to the lesion 210.

[0278] In FIG. 42a, the wire 14 is shown extending distally through an introducer sheath 135 and into the patient's body 137. The distal tip of the wire 14 has been navigated through the patient's vasculature 212 to reach the lesion 210. The wire 14 is shown here activated by an activation unit 2 and hence excavating and crossing the lesion 210 by virtue of vibration of the distal tip.

[0279] In this example, the activation unit 2 is shown at the proximal end of the wire 14. However, the activation unit 2 could instead be positioned at any of a plurality of intermediate positions along the proximal portion of the wire 14 that protrudes from the patient's body 137.

[0280] Once the lesion 210 has been successfully crossed as shown in FIG. 42b, the wire 14 is deactivated and left in situ within the patient's vasculature 212. The activation unit 2 is then removed from the wire 14, exposing the proximal end of the wire 14.

[0281] The deactivated wire 14 can now serve as a guide wire to transport the follow-on diagnostic or therapeutic device 214 to the lesion 210 as shown in FIG. 42c. The device 214 may most conveniently be threaded onto the proximal end of the wire 14. However, in principle, the device 214 could instead be attached to the wire 14 at any location along the proximal portion of the wire 14 that remains outside the patient's body 137.