Intravascular device for crossing an intravascular obstruction - Patents.com

Abstract

To provide an intravascular element which is easier to manufacture and easier to navigate at a site of a lesion, can be more simply and effectively activated and controlled, facilitates a flow along a blood vessel, and can more efficiently transverse a lesion while forming a larger lumen capable of better coping with a subsequent treatment.SOLUTION: Provided is an elongate intravascular element for transversing an obstruction in a blood vessel, comprising: a proximal section; a distal tip section 126 of smaller diameter than the proximal section; and a distal tapered intermediate section 130 extending between the proximal section and the distal tip section 126; wherein the length of the distal tapered intermediate section 130 is substantially λ / 2 or a multiple of λ / 2, or a number sequence λ / 4, λ / 8, so on which are fractions of even denominators, where λ is the wavelength of a drive frequency that produces longitudinal resonance in the element.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to the treatment of ischemia by using ultrasonically activated wires or other elongated elements to cross blockages in blood vessels and facilitate the introduction of subsequent therapeutic devices.

[0002] Prior Patent Applications The present invention develops concepts described in our international patent application published as WO 2020 / 094747, and in our unpublished UK patent application No. 2006665.0, the contents of which are incorporated herein by reference. [Background technology]

[0003] In endovascular procedures, an artery is selected and employed for use in gaining access to the vascular system based on the artery's ability to accommodate passage of the intended diagnostic or therapeutic device to the target site and the extent to which tissue and patient trauma can be minimized.

[0004] For example, in peripheral arterial or venous revascularization procedures, access is often achieved by surgical incision and puncture into the femoral, popliteal, tibial, and / or foot arteries, commonly known in medical terms as the Seldinger technique. Once access is achieved, an introducer wire and introducer sheath are inserted into the vessel and secured at the site. The sheath serves as a port for device introduction, withdrawal, and exchange, minimizing abrasion of the arterial tissue. A guide catheter and guidewire are then introduced into the artery to provide additional protection and aid in device navigation to the target site, and delivery of therapy.

[0005] The guidewire is carefully pushed along the lumen of the vessel so as not to cause trauma to the vessel wall and navigated to the site of the obstruction. In a successful procedure, the guidewire is then pushed across or through the obstruction and held in place to act as a guide over which diagnostic or therapeutic devices, such as balloon catheters and stents, are tracked to the site of the blockage. Guidewires are used in other minimally invasive procedures to introduce other devices and instruments into vessels or other cavities within the body to allow for examination, diagnosis, and different types of treatment.

[0006] Guidewires are used, for example, for balloon angioplasty, gastrointestinal, urological, and gynecological procedures, all of which require a passageway to be formed through an obstruction to facilitate the passage of larger, often more cumbersome devices to the site of the lesion, or to other targeted tissue distal to the lesion within the body.

[0007] Guidewires are important for therapeutic interventions and are manufactured from a variety of materials, most typically stainless steels and various alloys including NiTi (nitinol), cobalt chromium (CoCr), etc., with many different designs. Their manufacture often involves modification of the material's chemical composition and microstructural morphology, for example, by cold working the material while forming it into a wire, then machining the wire to various dimensional designs, and applying various heat treatments to produce the desired performance. As an example, a specific taper can be machined over the length of the wire to produce a differential degree of flexibility along the length of the wire. Thus, at its distal end, the wire will have sufficient flexibility to conform to the shape of the vessel and strength to transmit forces to the tip ("tip stiffness") or to traverse through a lesion.

[0008] In conventional guidewires, the tapered segment is enclosed in a coil or jacketing material that allows flexibility through the taper while still allowing force transmission through the coil to the distal tip of the wire. As explained below, such a coil or jacketing material is not required in the wires of the present invention, since the force to excavate the lumen is transmitted by ultrasonic energy even if the wire is not coated or jacketed.

[0009] The length of wires used in endovascular procedures varies according to the distance they are likely to operate. As an example, wires of 750mm to up to 900mm in length are typically used in many peripheral applications where they may be introduced into the femoral or popliteal anatomy, or tracked to and through blockages in the ipsilateral iliac-femoral and infrapopliteal arteries. Wire lengths used in ipsilateral and coronary applications tend to be on the order of 1200mm, 1500mm, or 1700mm in length. In fact, wire lengths that may be tracked antilaterally may be even longer, perhaps on the order of 2000mm to 2250mm or 2500mm or 3000mm. The most common wire lengths on the market are 1750mm, 1950mm, and 3000mm.

[0010] In many instances, extension wires can be used to facilitate the deployment of certain therapeutic devices, referred to as over-the-wire (OTW) devices, in which case the proximal end of the wire may require certain features.

[0011] Many conventional intravascular wires are passive mechanical devices with no active parts. Passive wires transmit nothing but energy applied by the clinician. They are manipulated by pushing, pulling and torquing their proximal ends to navigate to the site of the blockage and then push through or around the blockage. They come in a variety of configurations and designs to facilitate access and crossing of lesions in different anatomies and for different devices. However, very often the blockage is too difficult for conventional wires to cross. These passive wires are limited when attempting to cross a mostly or completely occluded blockage, where the guidewire does not function as intended or may be heavily calcified. In situations where passive wires are tracked down around the blockage, e.g., in subintimal situations, such wires are often unsuccessful in re-entering the true lumen.

[0012] The present invention relates to the use of ultrasonic vibrations transmitted along a wire to cross obstructions. The transmission of ultrasonic vibrations along small diameter catheters and assemblies is disclosed in U.S. Pat. No. 3,433,226. U.S. Pat. No. 5,971,949 describes the transmission of ultrasonic energy through waveguides of different configurations and tip shapes. U.S. Pat. No. 5,427,118 describes an ultrasonic guidewire system but does not discuss in detail the proximal shape of the wire or how it facilitates subsequent devices via the over-the-wire method.

[0013] Many current single transducer systems are not ultrasonically activated guidewires, but instead are ultrasonically activated catheters that include a wire member for agitating and cauterizing material. U.S. Patent Nos. 6,855,123 and 4,979,939 describe such systems. These catheters themselves require separate passive guidewires to help them navigate, and are therefore tools to facilitate separate guidewires crossing blockages. U.S. Patent No. 9,629,643 shows systems with various distal tip configurations, but all require separate guidewires for access.

[0014] These devices are directed to delivering alternative methods of revascularization and are often described as atherectomy devices, crossing devices, or vessel preparation devices. With limited exceptions, they are not considered to be the same as crossing a lesion for the purpose of functioning as a device delivery system. In the present technology, these ultrasound and recanalization wire devices provide or affect atherectomy by enhancing revascularization and debulking the lesion by removing the platelets that form the lesion.

[0015] In early, later, and current designs, ultrasound generator systems have become bulky due to the acoustics used, producing multiple frequencies and being large units scaled to control the pulse waves. Also, considerations of practical utility mean that known systems generally include separate elements. For example, many systems are designed with the signal generator housed in a separate unit from the transducer, and some are mounted on large trolley units, consoles, or stands that take up significant space in the clinical environment. U.S. Pat. No. 6,450,975, U.S. Pat. App. Pub. No. 2008 / 0228111, and U.S. Pat. No. 9,282,984 all describe such systems.

[0016] Ultrasonically activated catheter and wire systems have been considered in the past as a method of transection or atherectomy, and to prepare vessels for angioplasty treatment. Several products have been commercially available in the past, some remain on the market, and several new systems have recently come onto the market. Such catheter and wire systems often include an ultrasound generator and an ultrasound transducer. The ultrasound generator converts a mains power source into an ultrasonic waveform defined by its voltage amplitude, current, and frequency. The ultrasound transducer, and often an amplifying horn, converts the electrical energy into high frequency mechanical vibrations defined by the frequency and amplitude of the vibrations.

[0017] A small diameter wire waveguide is coupled at its proximal end to a transducer, either directly or through an optional horn, which transmits the mechanical vibrations to the distal tip of the wire, causing the distal tip of the wire to vibrate at a desired amplitude and frequency, intended to excavate material and ultimately facilitate revascularization or recanalization of vasculature and anatomical structures throughout the body. Tissue and material near the distal tip is affected by the ultrasonic movement of the tip in combination with its direct mechanical ablation, ablation and cavitation from the pressure wave component, and acoustic streaming that removes the ablated material from the zone around the tip.

[0018] In known intravascular wire systems activated by ultrasound, the proximal end of the guidewire is connected to a transducer. In our patent application published as WO 2020 / 094747, the wire travels through the transducer and extends not only distally from it, but also proximally. This allows the user to couple the transducer to the wire at any desired location and adjust the total length of the distal portion of the wire without having to cut it. The ability of the wire to travel or extend through the transducer and be coupled to the transducer in multiple locations has very useful practical advantages that arise from the ability to adjust the total length of the distal portion of the wire, for example to accommodate the length of the trajectory that the wire tip is expected to need to travel within the patient's body. Also, control of the wire is enhanced in holding its placement in place within the lumen of the vessel while adjusting or reconnecting the activation source. Furthermore, the adjustable length distal portion of the wire helps to achieve and optimize resonance at the distal tip at any desired frequency.

[0019] In developing the concepts disclosed in WO 2020 / 094747, the inventors recognized that existing endovascular wires needed to be improved in various ways, whether used with the concepts of WO 2020 / 094747 or otherwise. There is a need for endovascular wires that can be more easily manufactured, more easily navigated to the site of a lesion, more simply and effectively activated and controlled, and that can more efficiently traverse a lesion while forming a larger lumen that facilitates flow along the vessel and better allows for subsequent treatment to be accommodated. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] U.S. Pat. No. 3,433,226 [Patent Document 2] U.S. Pat. No. 5,971,949 [Patent Document 3] U.S. Pat. No. 5,427,118 [Patent Document 4] U.S. Patent No. 6,855,123 [Patent Document 5] U.S. Pat. No. 4,979,939 [Patent Document 6] U.S. Patent No. 9,629,643 [Patent Document 7] U.S. Patent No. 6,450,975, [Patent Document 8] US Patent Application Publication No. 2008 / 0228111 [Patent Document 9] U.S. Patent No. 9,282,984 [Patent Document 10] International Publication No. 2020 / 094747 [Patent Document 11] International Publication No. 2020 / 094747 Summary of the Invention [Problem to be solved by the invention]

[0021] It is an object of the present invention to address one or more of the shortcomings associated with the prior art. [Means for solving the problem]

[0022] Summary of the Invention According to one aspect of the present invention, there is provided an elongate intravascular element for traversing an obstruction within a blood vessel, the element comprising: A proximal section; a distal tip section having a smaller diameter than the proximal section; a distal tapered intermediate section extending between the proximal section and the distal tip section; The length of the tapered intermediate section is substantially λ / 2 or a sequence of multiples or even denominators of λ / 2, such as λ / 4, λ / 8, ..., where λ is the wavelength of the driving frequency that produces longitudinal resonance in the element.

[0023] The present invention also pertains to an intravascular device for crossing an obstruction in a blood vessel, the device comprising an elongate intravascular element of the present invention and an ultrasonic transducer mechanically coupled to the element for ultrasonically exciting a distal tip section of the element to facilitate crossing of the obstruction.

[0024] The present invention also provides a method of ultrasonically exciting a distal tip section of an elongated waveguide element, the method comprising inputting ultrasonic energy to a proximal section of the element at a drive frequency that excites a longitudinal resonance of the element, and generating transverse subharmonic vibrations in the distal tip section in addition to the longitudinal vibrations.

[0025] The ultrasonic drilling guidewire of the present invention differs from other ultrasonic wires and conventional guidewires in a variety of important aspects.

[0026] The present invention assists in navigating the wire through the anatomy, crossing lesions, and opening lumens of a diameter larger than the diameter of the wire or bulb, or any other enlarged features at the distal end of the wire. To this end, the distal end portion can be tapered or made to a smaller diameter than the proximal portion of the wire, and left bare to facilitate lateral drilling in the distal region. In conventional wires, and competing ultrasound guidewires, the distal end of the wire tapers to a smaller diameter to help the wire navigate tortuous anatomy. However, these wire portions are covered with a sleeve of spring-like coils and / or polymeric covering to allow such flexible elements to push through the anatomy.

[0027] The coil or jacket of prior art wires may have the secondary function of allowing longitudinal load transmission and maintaining a constant diameter over the length of the wire so that subsequent treatment devices introduced into the vascular system over the guidewire can be done so beyond the maximum working length. However, in the ultrasonic wires of the present invention, the energy in the form of ultrasonic displacement waveforms transmitted through the wire provides the means for enabling the wire to pass through obstacles, and thus a coil or jacket on the distal end portion of the wire is not required.

[0028] The absence of a distal coil or jacket in the present invention, and optimization of the length and diameter of the taper and distal land to provide lateral excavation of occlusion material, provides dual excavation by longitudinal and lateral displacement of the wire to affect erosive damage, abrasion, and cauterization. The present invention allows for preferential selection of lateral or radial subharmonics in addition to longitudinal.

[0029] To select the subharmonic frequency at the distal end that will drill in the lateral mode, the distal end portion of the wire is machined in a configuration according to the invention to match the dominant subharmonic resonant frequency that is preferentially selected. This maximizes the lateral displacement of the distal end portion through the design of the shaped profile of the wire relative to its taper and the length and diameter of its distal land.

[0030] For a given material selected for its mechanical properties of elasticity, toughness, and characteristic acoustic performance at 37C, the optimum properties of the wire in terms of overall length are odd multiples of λ / 4 (n=1, 3, 5, ..., n), where λ is the wavelength of the material for a given input frequency and specific material properties.

[0031] The transition region of the taper provides a step gain or amplification of the ultrasonic energy transmitted distally down the wire. However, the inventors have realized that natural selection of the dominant subharmonic can be achieved by making the taper length λ / 2. It has also been found that optimal lateral transmission of the wire is obtained with a distal land length of λ.

[0032] An important aspect determining ease of use is that the wires of the present invention have tip flexibility that allows them to conform to the shape of the artery or other vessel they navigate, and are flexible so that the lateral mode of vibration causes significant force displacement. Thus, wires with distal land diameters of 0.005 inches to 0.008 inches are preferred, with 0.007 inches being preferred, for example, to achieve a specific A at 5°C to 18°C. f The optimum performance is achieved in a Type 1 Nitinol wire having a

[0033] It is necessary to utilize longitudinal and lateral displacement modes of excitation without subjecting the wire to high levels of stress or strain that could catastrophically break it. Thus, the wire is mechanically coupled to an ultrasonic transducer and excited primarily in the longitudinal direction at a predetermined frequency and displacement amplitude. The wire geometry is selected to resonate primarily in the longitudinal mode at or near this input drive frequency, which creates standing waves in the wire along its length while resonating. This results in a significant longitudinal component of vibration near the distal tip.

[0034] Another challenge is that while transverse modes of displacement can occur anywhere along the length of the wire, it is desirable to transport and focus the energy toward the distal end. In particular, in addition to the longitudinal modes at or near the system's driving frequency, there will be a variety of additional longitudinal sub-harmonics that will be excited in a length of wire suitable for the anatomical entry. Furthermore, the wire will have transverse or lateral mode vibrations near the primary longitudinal frequency and its sub-harmonic frequencies. Any offset or imbalance introduced in the anisotropy or morphology of the wire, or geometry, will promote vibration of these transverse modes, especially if they are at or near the longitudinal modes. However, it is desirable to promote transverse excitation to occur preferentially in the distal region of the wire.

[0035] The lateral displacements occur at frequencies lower than the drive or input frequency, and the damping and amplification of their motion in the wire is governed by the drive frequency, as well as the geometry and material used in the wire. Such lateral modes are superimposed on the longitudinal motion of the distal region and, according to the invention, can be preferentially selected by incorporating certain design features in the wire. In principle, these lateral displacements can be present in a wire, but the selection of specific frequencies and vibration modes can be achieved by adjusting the geometry of the wire, including the position and length of the taper, and the magnitude of the motion can be determined by the diameter and material properties of the distal portion of the wire.

[0036] The wire needs to be optimized to displace the wire at optimal levels of force and displacement to excavate the obstacle. Thus, in the optimized wire of the present invention, different tapers and different land constructions along the length of the wire can affect different lateral and longitudinal responses at the distal end region of the wire. These responses can then be optimized for different use cases envisioned in different anatomies and different types of lesions.

[0037] There is also a need for a guidewire that can rapidly navigate through and through chronic total occlusions consisting of hard calcified lesions, and thus provide a lumen large enough to allow for the passage of a subsequent treatment device over the wire. Accordingly, it is an object of the present invention to selectively excavate occlusive material within a vessel and open an aperture or lumen substantially larger than the cross-sectional area of ​​the wire to facilitate the delivery of subsequent treatment. To this end, the excavation mechanism of the distal tip region of the wire includes a direct longitudinal vibration coupled to a lateral motion that act in concert to cauterize and open the lumen of the lesion. This cauterization or other drilling mechanism can occur not only when the distal tip of the wire contacts the lesion, but also when the distal tip of the wire contacts the lesion after initially penetrating the lesion.

[0038] A variety of interrelated variables can be modified in accordance with the present invention to optimize lesion drilling. Specifically, the wire directs ultrasonic energy from where it is coupled to the transducer to the distal end of the wire. Drilling at this distal tip region of the wire is determined by the mode (i.e., lateral and longitudinal motion) and amplitude in which the energy is contained within the wire, and thus the driving frequency and amplitude that drives the ultrasonic signal / displacement in the wire through its length, the characteristics of acoustic transmission in the wire, and the diameters at different sections of the wire, i.e., the proximal land section, the intermediate tapered section, and the distal land section, affecting the amplification and amplitude of the wire displacement in various regions along the length of the wire as it responds to excitation.

[0039] Thus, the dimensions and uniformity of the wire affect its response in terms of the internal composition of the wire and the nature of its material; the wire profile and any discontinuities or shaped features or formations in the wire; the uniformity of the wire with respect to the shape and dimensions of the wire, such as tolerances over its length; the taper dimensions, transition region section and their appropriateness to the applied ultrasonic energy; the change in diameter of the wire from the proximal diameter of the wire at the transducer to the diameter of its distal drilled land and the amplification associated with this decrease in diameter over the length of the wire; the location and length of the tapered section and how it corresponds to wavelength.

[0040] As the mechanical properties and design of the wire are selected to optimize its performance, it is found that these attributes are related to the physical manifestations of lateral motion or lateral motion.

[0041] All of these objectives of the invention must be achieved with a wire that is also flexible enough to validate the shape of the anatomical structures it passes through during use. In particular, the flexibility and elasticity or resilience of the wire determine whether it can fit within the lumen of an artery or other blood vessel. The diameter and mechanical strength of the wire also determine whether it can track or navigate through tortuous anatomical structures and thus accommodate the shape of the vessel, without clogging, getting stuck, or aggravating and penetrating the vessel wall due to its inability to deflect and conform to the shape of the anatomical structure. In this regard, in the case of the femoral artery, the ability of the wire to conform to the shape of the vessel is less challenging than, for example, in the case of the leg artery, since the vessel is larger, and its bending is comparable to that of the coronary arteries and some of the larger neurovascular anatomical structures.

[0042] In summary, wire design parameters can be selected to control how much energy is coupled into the longitudinal and transverse modes. In a preferred embodiment, the ratio of the diameter of the proximal segment that defines the working length of the wire to the diameter of the distal segment that defines the drilling section of the wire is between 2:1 and 3:1, which gives the optimum gain or amplification.

[0043] The optimum length of the tapered section to select the dominant secondary frequency is λ / 2, i.e., the ratio of the length of the tapered section to the length of the distal land is λ / 2:λ, and the effective length of the wire from its junction to the distal tip is an odd multiple of λ / 4 ((2n+1)λ / 4).

[0044] A wire is one example of an elongate intravascular element of the invention that can be used as a waveguide or wave delivery system. For example, the element can be a hybrid of a wire and a catheter. In particular, the proximal portion of the element, e.g., one meter of the element from the proximal end, can have an encapsulated wire in a manner similar to a catheter, whereas the distal portion of the element extending to the distal end can be an unencapsulated wire. The wire or other element of the invention can be the inner component of an overall wave delivery system.

[0045] The design of the transmission member or waveguide wire is optimized to control the transmission of the wave pattern through different anatomical structures and through different materials to the distal tip. The morphology of the materials used is important: while they can be manifested as a highly elastic isotropic material morphology at the "macroscopic" level, they can have anisotropic micromorphological features that can delay the onset of initial cracks or inhibit crack progression.

[0046] The materials used in this embodiment are extensively cold worked stainless steels, nickel titanium alloys, and / or cobalt / chromium alloys, e.g., linear elastic nitinol. Specifically, for NiTi only alloys, strict control is exercised over inclusion size and population to limit the chance of fracture. For other alloys, control is exercised over other morphological features that may act to promote premature failure of the wire.

[0047] The present invention allows for the introduction of specific features machined into the wire at the proximal and distal ends and along its length that enhance the wire's ability to cross lesions, strengthen the wire, allow for better control of the wire, and allow for bonding of the wire and efficient transmission through the wire. The composition of the design will vary depending on the materials used and the intended use.

[0048] The wire geometry, as well as the materials used, are optimized for various applications. The wires are machined to minimize defects and optimize transmission through tightly controlled tapers and keying splines throughout the length of the material and through sections of the length. [Brief description of the drawings]

[0049] Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: [Figure 1] 1 is a schematic perspective view of an ultrasound wire system according to the present invention; [Diagram 2] FIG. 1 is a perspective view of a handheld ultrasonic activation unit and a wire with markings placed thereon. [Diagram 3] 1 is a schematic side view of a wire according to the present invention; [Figure 4] FIG. 2 is an enlarged side view of a distal end portion of a wire according to the present invention. [Diagram 5] FIG. 13 is an enlarged view of a distal end portion of a wire in a variation of the present invention. [Figure 6]FIG. 2 is a side view of a wire of the present invention showing its response to excitation. [Figure 6a] FIG. 2 is a side view of a wire of the present invention showing its response to excitation. [Figure 7] FIG. 2 is a schematic side view of an active wire having an obliquely offset distal end portion. [Figure 8a] 1 is a schematic side view of a further active wire of the present invention, including a marker band. [Figure 8b] 1 is a schematic side view of a further active wire of the present invention, including a marker band. [Figure 9] FIG. 2 is a schematic side view of another active wire of the present invention. [Figure 10] 1A-1C are schematic side views of other active wires of the present invention, each having an enlarged bulbous distal tip. [Figure 11] 1A-1C are schematic side views of other active wires of the present invention, each having an enlarged bulbous distal tip. [Figure 12] FIG. 2 is a side view of a wire of the present invention showing the effect of jacketing the wire. [Figure 13a] FIG. 11 is a schematic perspective view showing a portion of the end of a wire in a modified example of the present invention. [Figure 13b] FIG. 11 is a schematic perspective view showing a portion of the end of a wire in a modified example of the present invention. [Figure 13c] FIG. 11 is a schematic perspective view showing a portion of the end of a wire in a modified example of the present invention. [Figure 14a] FIG. 11 is a schematic perspective view showing a portion of the end of a wire in a further variant of the invention; [Figure 14b] FIG. 11 is a schematic perspective view showing a portion of the end of a wire in a further variant of the invention; [Figure 14c] FIG. 11 is a schematic perspective view showing a portion of the end of a wire in a further variant of the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Figure 1 of the drawings shows the overall configuration of a system according to the present invention and illustrates some of the main components of such a system. This example features a handheld ultrasound activation unit 2 having a flexible transmission member in the form of an intravascular wire 4 extending therethrough in central alignment.

[0051] The wire 4 can be inserted into the patient's vascular system and traversed to bring its distal end to the location of the lesion. When the wire 4 encounters a complex lesion that resists crossing, the activation unit 2 can be coupled to the wire 4 at a suitable longitudinal location. When activated, the activation unit 2 transmits ultrasonic vibrations to and along the wire 4, enhancing the ability of the wire 4 to traverse the lesion via cauterization and other mechanisms. The wire 4 thereby functions as a traversing wire to traverse an obstruction in a vessel and then as a guidewire to remain in place to deliver a subsequent therapeutic device to treat the lesion.

[0052] Typically, the length of the wire 4 can be, for example, greater than 2 m up to 3 m. For example, accessing a lesion in or through the foot may require the wire to travel a distance of typically 1200 mm to 2000 mm within the vascular system, depending on whether an ipsilateral, antilateral, or radial approach is selected. In this regard, the wire 4, tapered distally to a fine wire at its tip, can navigate into the pedicle arteries and around the arch of the foot between the dorsal and plantar arteries. However, the present invention is not limited to foot or other peripheral applications, but can be used, for example, in coronary applications, where the ability of the wire 4 to navigate and drill within tortuous, small diameter arteries is also beneficial.

[0053] The diameter of the distal section of wire 4 will determine the flexibility of wire 4 and the ability of the wire to easily conform to the shape of the anatomy it is intended to pass through. Thus, for example, in tortuous (foot or coronary) anatomy, a distal section of 0.005" to 0.007" diameter will combine flexibility with the ability to excavate occlusive material.

[0054] The activation unit 2 also includes a user control 6 and, optionally, a display. The activation unit 2 further comprises a distal manual toggle 8 that the user can rotate about a central longitudinal axis of the unit 2 and the wire 4. In particular, the activation unit 2 can be slid over the wire 4 and can be coupled to the wire 4 at multiple longitudinally spaced locations by applying torque to rotate the toggle 8. To effect the coupling, the toggle 8 acts on a coupling, such as a collet, within the activation unit 2 that surrounds and is coaxial with the wire 4. When the toggle 8 is tightened, the collet grips the wire 4 to transmit ultrasonic energy from an integrated ultrasonic transducer within the activation unit 2, optionally via an amplifier horn that is coupled to the transducer. The wire 4 can be directly coupled to the transducer in some embodiments, in which case the horn can be omitted.

[0055] The toggle 8 makes it possible to reversibly release the activation unit 2 from the wire 4. Provision is thereby made for exchanging wires 4 of different dimensions, configurations or materials for different purposes. There is also the possibility to exchange the transducer or horn in the activation unit 2.

[0056] FIG. 1 shows an exploded configuration in which the ultrasonic signal generator 10 is separate from the activation unit 2. In this example, the ultrasonic signal generator 10 is connected to the activation unit 2 by a connector cable 12. In an alternative configuration, the ultrasonic signal generator 10 can be incorporated within the housing of the activation unit 2. The example shown in FIG. 1 has the ultrasonic signal generator 10 powered externally and therefore includes a power cable 14 that connects to an external source of power. Alternative embodiments can be powered by an internal battery, which can be incorporated, for example, into the ultrasonic signal generator unit 10 or the activation unit 2.

[0057] In general, the system components are preferably portable, and more preferably handheld. They may be wireless, rechargeable, reusable, and recyclable. Any external cables 12, 14 for carrying power or signals may be coupled via slip rings to allow free rotation of the cables 12, 14 and avoid entanglement with the wires 4, or to provide a conduit for the proximal portion of the wires 4.

[0058] A semi-automatic control system can control or modulate the signal from generator 10 applied to the transducers and horns of activation unit 2, i.e., to the traversing wire 4, based on feedback from the wire-tissue interaction to control the signal transmitted and adjust for inhibition or increased resistance or losses due to modulating the applied force. Visual and tactile feedback indicators can provide visual, audio, and / or tactile feedback to the user regarding the status of the device, the nature of the tissue being ablated, and indicate the level of force that can be applied to cause tissue ablation and destruction, and progression of the traversing wire.

[0059] The system may include a means for providing a manually operated override to aid in controlling the amplitude of vibrations delivered to the distal tip, allowing the system to be controlled by a user operating the device during the course of a procedure, via controllers and user input mechanisms located on the generator and delivery unit, or to be controlled autonomously.

[0060] As described below, the distal end of wire 4 is also preferably optimized to have a marker band for tracking through the anatomy under ultrasound imaging modes as well as highlighting the location under x-ray. The distal end can have radiopaque markers to indicate the working length and traversing tip of the wire.

[0061] 2 illustrates how the wire 4 may be etched or otherwise marked with a series of optimal band-like markings 92 to guide the user in selecting a length of wire 4 that will facilitate distal activation. The user may then align the mating of the activation unit 2 with the band-like markings 92 on the wire 4, optionally using other markings appropriately positioned on the housing 18 of the activation unit 2. This approach applies to both straight embodiments in which the proximal portion of the wire 4 emerges axially from the housing 18 of the activation unit 2, and other embodiments in which the proximal portion of the wire 4 emerges laterally at a position along the length of the housing 18.

[0062] The markings 92 address the challenge in controlling the system, namely, how the ultrasonic energy is coupled to the wire, and the importance of placing the connection point in a specific area that will best couple. The markings 92 placed on the proximal segment of the wire 4 ensure that this alignment is clear to the physician. These markings 92 also make it easy for the physician to reconnect the activation unit 2 to the wire 4 at different locations during the procedure.

[0063] To address visibility and alignment of the excitation, the markings 92 may be aligned with a reference point on the activation unit 2, for example, a reference point on a stress relief feature at the distal end of the housing 18 to indicate the best location point. Visualization of the markings 92 may be improved by adding lighting and / or a transparent or translucent window to the activation unit 2, for example, positioned over the stress relief feature distal to the unit 2.

[0064] The markings 92 tend to be applied by laser etched beading or other means such as application of a coating and / or jacket to mark the surface of the wire 4 in a manner that allows the user to discern the best connection points along the length of the wire 4. It is believed that the best way to accomplish this is to modify an oxide surface layer or finish of the wire 4. The period or longitudinal spacing of these markings is λ / 2, and their length is a function of the efficiency of coupling energy into the wire 4, which is also a function of the mechanical and dimensional properties of the wire.

[0065] In one example of the invention, the markings 92 on the wire 4 may indicate any of a number of lengths at which the distal section of the wire 4 emerging from the activation unit housing 18 is at or near the resonant length and the proximal section is not at the resonant length. In other words, the attachment zone markers 92 are optimally positioned on the wire 4 so that when coupled to an acoustic source, the length of the distal portion from the attachment point to the distal tip is equal to the resonant length, whereas the length of the proximal portion from the attachment point to the proximal tip is equal to the non-resonant length. In practice, these markings 92 may be placed in adjusted positions relative to the system to account for bends and other design features that may affect the resonant response.

[0066] When ultrasonic energy is used to excite the wire 4, it is desirable to optimize the displacement amplitude at the distal tip of the wire to excavate the lesion. Conversely, it is desirable to minimize the displacement or movement of the proximal end of the wire, which is outside the patient's body and may in fact hang freely proximal to the activation unit 2.

[0067] To achieve this, the distal length of the wire 4, from the distal tip to where the activation unit 2 is coupled to the wire 4, should be an odd multiple of a quarter wavelength of the ultrasonic wave motion. This creates a standing wave in the wire with an oscillating antinode at the distal tip, thus maximizing the amplitude of vibration at the distal tip.

[0068] As a result, placing the distal end of the transducer an odd multiple of a quarter wavelength from the distal tip of the wire 4 will maximize vibrations at the distal tip. Conversely, ensuring that the length of the proximal section is a multiple of a half wavelength from the transducer fixation location will minimize vibrations at the proximal end of the wire 4.

[0069] When coupled to the ultrasonic transducer 20 in the activation unit 2, the wire 4 of the present invention is subjected to axial ultrasonic vibrations and can be considered as an unfixed rod under longitudinal or axial vibration. The natural frequency of an unfixed rod under longitudinal or axial vibration is given by:

number

[0070] The ultrasonic activation unit 2 applies a constant, known frequency and the speed of sound in the wire 4, c, can be measured experimentally or approximated by the following equation:

number

[0071] For a system applying a constant or nearly constant frequency, the length L of the wire 4 at which resonance occurs is given by:

number

[0072] Indeed, in a through-wire system, from the connection point of the wire 4 to the transducer, the wire 4 can be considered as two non-fixed rods undergoing vibrations in their longitudinal axes: one rod extends distally from the activation unit 2 and the other rod extends proximally.

[0073] As an example, the speed of sound in a particular Nitinol alloy is about 3400 m / s. For a driving frequency of 40 kHz, the wavelength λ can be calculated to be about 85 mm. The resonant length can therefore be determined and marked at the optimum location on the wire 4. The wavelength also has a large impact on the choice of taper location along the wire 4 and the taper length.

[0074] 3-7 show various preferred and optional features of the wire 4. FIG.

[0075] Generally, the wire 4 has features that allow it to be integrated with the handheld activation unit 2. For example, location markers are provided to guide optimal positioning and attachment of the activation unit 2 to facilitate attachment and release at multiple longitudinal locations. Thus, a series of optimal attachment locations are etched or otherwise marked on the wire 4 over a substantial length of the proximal section of the wire to guide the user in placing and selecting optimal attachment locations for distal ultrasound transmission from the activation unit 2. The housing 18 of the activation unit 2 can also have markers that can be aligned with the markings on the wire 4 prior to bonding.

[0076] As with all intravascular wires, a balance between flexibility or "trackability" and stiffness or "propulsion" is required. However, unlike passive wires, this wire must be able to transmit ultrasonic energy to distal regions to aid in traversing the lesion. In this way, the wire 4 acts as a driller not only at its tip but also along part of its length. The wire 4 has a length of distal land that acts radially as a lateral drilling device to open the aperture. The wire can have a distal shaped length to amplify the radial drilling.

[0077] The wire 4 includes regions where the geometry tapers to affect a change in diameter, either from a larger diameter to a smaller diameter, or from a smaller diameter to a larger diameter. In regions where tapering is required, and elsewhere, the sections may be welded or otherwise joined together end to end. Such welds or joints must be able to withstand normal bending and cyclic fatigue modes, as well as stresses resulting from the transmission of ultrasonic energy. Alternatively, the entire wire 4, or portions of the wire 4, may be polished or similarly treated to achieve the desired geometry.

[0078] Thus, the wire 4 can be manufactured from sections welded end-to-end. For example, a proximal section can be machined as a standard diameter to provide amplification as well as a standard connection for a proximally loaded activation unit 2. This proximal section can be welded to one of a selection of wires of various diameters that may have custom distal ends and tips. Thus, the sections can be selected and combined in a variety of ways. This effectively alleviates the need to hold an inventory of various wire diameters, as sections of several different wire diameters can be assembled to produce wire 4 in many required configurations. Welding the proximal segment to the distal segment facilitates more efficient manufacturing and more efficient transfer when post processing is performed on the wire, and various materials can be welded to the proximal NiTi base as needed.

[0079] Ideally, the taper can be selected to start at a length equal to or nearly equal to a multiple of half the wavelength of the wire system. This places the start of the taper at an antinode of the standing wave in the wire 4, where the amplitude of the vibration is at its maximum. The length of the tapered section is preferably selected to be equal to or nearly equal to a half wavelength of the resonant system. In general, the welds or joints should be located at longitudinal positions where the stresses are minimal. Because the welds or joints are in places of low stress, the loads applied to them during the activation of the wire will not lead to catastrophic fatigue failure.

[0080] The wire 4 shown in Figure 3 comprises a proximal section 124 for crossing the lesion, a central or intermediate section 128, and a distal drilling section 130. The intermediate section 128 is thinner than the proximal section 124 but thicker than the distal section 130. Thus, the intermediate section 128 is joined to the proximal section 124 by a tapered proximal transition region 132 and joined to the distal section by a tapered distal transition region 134. Each section is welded to the next by a weld 122 proximal to the respective transition region.

[0081] The proximal section 124 has a series of longitudinally spaced band-like markings 92, similar to those of FIG. 2, which guide the user in selecting a wire length that promotes distal activation and inhibits proximal activation. The wire 4 further includes radiopaque marker bands 136 to aid in tracking the intermediate section 128 and distal section 130 within the patient's anatomy during the procedure. These various markers 136 tend to be created by plasma deposition, atomic layer deposition, or sputtering, for example, of sputtered gold, to resist ultrasonic loading.

[0082] The proximal section 124, intermediate section 128, and distal section 130 are all generally straight and aligned with one another along a central longitudinal axis of the wire, although they are substantially flexible to bend along their lengths, except that a composite distal end portion 138 of the wire 4 has a shape set to bend away from the general axis of the wire 4 in the remainder of the distal section 130. These bends or heat set shapes enhance lateral movement in addition to longitudinal movement of the wire 4.

[0083] Specifically, as also shown in Figure 4, the distal end portion 138 includes an inwardly angled leg 140 and an outer distal tip 126 at the distal end of the angled leg 140. The leg 140 is angled relative to the general axis of the wire 4, and the distal tip 126 is angled relative to the angled leg 140. The distal tip 126 may be a bulbous or otherwise enlarged feature, such as 25 shown in Figure 4, and the coating 142 may extend partway along the length of the angled leg 140, with the distal end of the angled leg 140 and the distal tip 126 remaining uncoated.

[0084] In this example, the distal tip 126 is angled further away from the general axis of the wire 4 than the angled leg 140. Thus, the distal tip 126 and the angled leg 140 are both angled in roughly the same direction away from the general axis of the wire 4. However, in other examples, the angle of the distal tip 126 is closer to the general axis of the wire 4 than the angled leg 140. In some cases, the distal tip 126 can be more approximately parallel to the general axis of the wire 4 in the remainder of the distal section 130.

[0085] In summary, the total length of the distal portion of wire 4, from distal tip 126 to the connection point or junction of activation unit 2, can be equal to the resonant length of wire 4. Ideally, the taper length is equal to a multiple of half wavelengths. The diameters of the various sections of wire 4 are selected for an optimal balance between propulsion and trackability, in addition to allowing standard size subsequent devices to use wire 4 as a guidewire.

[0086] In this example, the wire 4 includes an angled portion positioned at a location to enhance the maneuverability of the wire 4 when tracking the location of a lesion. By way of example, the length of the angled leg 140 can be 15 mm to 25 mm, and the length of the distal tip 126 can be 2 mm to 5 mm. The angled leg 140 facilitates steering through anatomy, whereas the distal tip 126 facilitates tracking through small diameter lesions. The angle between the angled leg and the remainder of the distal section 130 is typically 10° to 40°. This angle provides a means to navigate to bifurcations, but is not so large as to promote stress beyond the fatigue limit of the wire 4. The angle between the distal tip 126 and the angled leg 140 is typically 10° to 30°. This allows navigation in diseased small diameter vessels.

[0087] The wire 4 may be heat treated, for example by annealing after machining and shaping the tip 126, to optimize its microstructure to resist fatigue.

[0088] Visibility of the wire 4 under x-ray or other imaging modes may be enhanced by the addition of a radiopaque marker band or coating 136 selected to optimize visibility under well-established imaging modes. The wire 4 may also have a coating 142, such as a hydrophilic coating, to reduce friction with the surrounding catheter or tissue.

[0089] 5 shows that the wire 4 may have a distal coil or polymer jacket 144 attached or bonded onto the distal section 130. The jacket shown here terminates distally just before a bend in the wire 4 that facilitates deflection of the distal tip 126. The distal tip 126 of the wire 4 may be coated or treated to harden its surface or enhance its ablation properties.

[0090] 6 and 6a show a wire 4 having a substantially straight drilled portion or land 124, a distally tapered intermediate section 130, and a distal tip portion 126 for crossing the lesion. The distal tip portion 126 has a smaller diameter than the proximal section 124 by virtue of the taper of the intermediate section 130 therebetween. For example, the diameter of the proximal section 124 may be 0.43 mm and the diameter of the distal tip portion 126 may be 0.18 mm or 0.25 mm. The taper in the intermediate section 130 is slight and is therefore greatly exaggerated in these drawings. The length of the tapered intermediate section 130 may extend over a multiple of λ or a fraction of λ, preferably a fraction with a numerator of 1 and an even denominator, e.g., the sequence 1 / 2, 1 / 4, 1 / 8..., while the length of the distal tip portion 126 may be λ / 2, or a multiple of λ / 2, or a fraction of λ / 2, such as λ / 4.

[0091] The overall geometry of the wire 4, including its nominal diameter and length, as well as the drive frequency of the system, is determined by the sound speed characteristic of the wire's material, which is a function of the properties of that material, and its geometry. The dimensions of the straight and tapered sections of the wire are machined in functional intervals of wavelengths.

[0092] For the example of Nitinol, which has a Young's modulus of approximately 75 GPa, in this example, λ, λ / 2, and λ / 4 are determined to be 84 mm, 42 mm, and 21 mm. The selected frequency creates harmonics along the length of the wire, and the load at the tip of the wire assists in establishing a standing wave for featureless lesions. The distal section 126 can be tapered along its length or its diameter can be uniform. The system can create lateral and longitudinal displacements over a range of frequencies away from the range of the drive frequency, often creating subharmonics of the frequency of the distal section 126.

[0093] As an example, and not exclusive of other dimensional values, a wire with a core cross-sectional diameter of 0.43 mm has a tapered section 130 optimally positioned to transition to a distal wire diameter of 0.18 mm. The length of each section of wire can be selected to have a longitudinal resonant mode at or near a drive frequency such as 40 kHz, with strong subharmonics at or near 20 kHz, 10 kHz, or other. Through proper design, adjacent transverse modes near 40 kHz and 20 kHz, etc. may exist. There may be amplification across the taper by a factor of about 2.4 or other suitable value. When the wire emerges from the catheter or sheath, additional low frequency transverse vibrations may be induced via cantilever actuation.

[0094] As a result, through proper selection of wire material, geometry, and distal design features, the desired transverse mode will be activated even when the wire is driven with longitudinal vibrations. Simultaneously, both longitudinal and transverse vibrations contribute to excavating the lesion, resulting in the wire opening an aperture or lumen within the lesion whose inner diameter is substantially larger than the diameter of the wire.

[0095] In terms of length, the total length of the wire can be a function of an odd multiple of λ / 4. The effective length, which is the distance from the proximal connection point to the distal tip of the wire, can also be a function of an odd multiple of λ / 4.

[0096] The purpose of the tapered transition region 130 is to provide gain and maintain the transfer of energy through the wire. The tapered section will also affect how the transverse mode displacement can be established in the distal land section 126 of the wire.

[0097] The introduction of a taper can also serve to facilitate a change in material between one portion of the wire and another, which can create a wavelength difference between the distal and proximal segments.

[0098] The diameter of the tapered transition region can be changed in a step, exponential, radial, or linear fashion. For amplification purposes, the change in cross-sectional area represents the gain level of both the lateral and longitudinal displacement amplitude of the wire. The length and diameter of the distal section 126 will determine the mode and magnitude of the axial and radial displacement.

[0099] Since the purpose of the activated wire 4 is to traverse and excavate the lesion, its dimensions are optimized with the goal of excavating the largest aperture possible for a given input power. In this regard, FIG. 6 shows that when the distal section 126 of the wire 4 is activated, it moves in a primary longitudinal mode, moving in and out, and also in a radial direction that projects and excavates a larger volume at the distal end via the longitudinal motion of the wire 4. The distal section 126 of the wire 4 is also seen to move via lateral and wavy motions at or near the secondary modes of the drive frequency and differential harmonics depending on the activation frequency and also the length of the distal section 126. These waveforms interfere with each other and may be more or less effective at excavating material at various moments.

[0100] 6 further illustrates how the distal end section 126 of the wire 4 excavates an aperture whose diameter is larger than that of the wire, thus creating a larger lumen through which therapy may be introduced to the lesion. Again, in this example, a catheter sleeve or polymer jacket 144 terminates before the unjacketed distal section 130 of the wire. When the distal section 126 of the wire 4 is activated, it moves in a primary longitudinal mode, moving in and out, and also radially planning and excavating a larger volume at the distal end via the longitudinal motion of the wire 4. The distal section 126 of the wire 4 is also seen to move in other modes via lateral and wavy motion under resonant waves 146, and differential harmonic secondary modes, depending on the activation frequency, the length of the distal section, and the torsion of the anatomy.

[0101] Thus, when activated with ultrasonic energy, the wire 4 functions as a drilling tool to excavate material distally towards the distal tip of the wire 4 through the offset translational or lateral motion of the wire 4 within the vasculature, which by virtue of the longitudinal motion then provides a lateral offset. Thus, the wire 4 erodes the inner surface of the occlusion not only right at its distal tip, but also along a portion of its length extending proximally from the distal tip, thus forming a wider aperture for the passage of a subsequent treatment device over the wire 4. As the wire 4 extends beyond the distal end of the lesion, the lateral displacement continues to excavate within the lesion, thus forming a larger lumen.

[0102] FIG. 7 shows a wire 4 formed or shaped with an obliquely offset distal drilling section for crossing a lesion. In this embodiment, the distal section is not straight, but angled by a heat-set shaped tip 126. The dimensions of the tip 126 are optimized to provide improved performance for steering and drilling into the lesion. In particular, the angle of the tip 126 relative to the longitudinal axis of the distal section, and the length of the tip 126 determine the ability of the wire 4 to turn into a particular side branch vessel. The angle and length of the tip 126 also affect the way in which the wire 4 will drill into a section of stenosed material when activated. If the dimensions of the tip 126 exhibit harmonic characteristics, for example, λ / 8 or about 11 mm in length, the wire 4 will open a significantly larger tunnel into the lesion than, for example, a 25 mm tip section. The amplitude of the waveform and the number of times the distal section of the wire 4 passes through the calcified section will determine the diameter of the tunnel drilled.

[0103] The wire 4 does not necessarily have to be shaped or beveled at its tip, but if the wire is shaped or beveled at its tip, the angle is carefully selected. If the angle of the tip 126 is too large, the lever arm may be large and cause the wire 4 to fatigue excessively. Conversely, if the angle of the tip 126 is too small, the wire 4 may not be effectively steerable. In this regard, FIG. 7 shows that the tip 126 may be offset from the longitudinal axis of the wire 4 by about 15° to 45°, allowing the tip 126 to mill and drill a larger volume of the lesion. The tip 126, when suitably heat treated, for example, above 500° C. for less than 10 minutes, creates a microstructure that is reliably resistant to crack propagation and, therefore, fatigue.

[0104] 8a and 8b show how the visibility of the location of the wire 4 within the patient's body can be enhanced, for example, by using a gold marker band 194. Such a marker band 194 can be secured, for example, close to the distal tip 126 of the wire 4 (e.g., about 3 mm from the distal tip 126) and also from the distal end of the proximal section 184, just before the start of the tapered mid-section 186. The marker band 194 is placed in the location of least stress when using the wire 4. This minimizes the chance of the marker band 194 becoming detached or the wire 4 failing at those locations. The marker band 194 tends to be a flush fit into a circumferential groove ground around the wire 4.

[0105] 9 shows a variation in which the distal tip 126 of the wire 4 is rounded and has no sharp transition regions. By way of example, in this example the proximal section 184 may be 1800 mm long, the tapered middle section 186 may be 84 mm long, and the distal section 188 may be 10 mm long. Again, a marker band 194 surrounds the wire 4 near the distal tip 126 of the wire 4 and the distal end of the proximal section 184.

[0106] 10 and 11 show other variations of wires 4 each having a bulbous distal tip 198, which is rounded to avoid sharp transition areas, but may be chamfered or faceted, preferably with obtuse angles between facets and distally converging facets to facilitate passage of the wire through the anatomy. An enlargement such as a bulb may be located at the distal tip and / or spaced slightly from the distal tip to cover a radiopaque coil or other material.

[0107] The spherical tip 198 may be, for example, 3 mm to 4 mm in length and may have a diameter of just over 0.4 mm, or, for example, 0.010 inches to 0.035 inches. Except for its spherical tip 198, the wire shown in FIG. 10 is otherwise similar to the wire 4 shown in FIG. 9. Again, the wire 4 shown in FIGS. 10 and 11 has a circumferential marker band 194 that may be flush-fit into a circumferential groove ground around the wire 4. Conveniently, the spherical tip 198 may be surrounded by one of the marker bands 194, as shown in the figures.

[0108] In the example shown in FIG. 11, the wire has a proximal portion including a straight section 200 and a distally tapered section 202. The straight section 200 may have a ridged or textured surface to improve engagement with an activation device, as shown. The proximal portion is welded to an intermediate portion that comprises the majority of the length of the wire 4. The intermediate portion also includes a straight section 204 and a short, distally tapered section 206. The marker band 194 is shown surrounding the straight section 204 of the intermediate portion 194 near the distally tapered section 206. Finally, a short, thin distal section 208 extends distally from the intermediate portion 186 to the bulbous tip 198.

[0109] FIG. 12 illustrates how a desired distal length can be left clear or uncoated while still being free to vibrate laterally, as shown, by coating or thickly coating the wire, for example with a polymer jacket or coil 144. The effect of the jacket or coating can also be mimicked by a catheter around the wire 4. It has been found that the distal extent of the jacket controls the aperture created by the distal drilling section 130 of the wire 4. The wire 4 drills into the lesion up to the collar or edge 148 at the distal end of the jacket 144. It has been found that if the unjacketed distal length of the wire is not long enough, an aperture not as large as the diameter of the wire can be created in the lesion, inhibiting even progression of the wire through the occlusion.

[0110] In particular, jacketing the wire 4 below or above the resonant length or harmonic wavelength results in the distal edge 148 of the jacket 144 not matching the resonant length or harmonic wavelength, preventing the formation of an aperture. Conversely, jacketing the wire 4 up to the resonant length or harmonic wavelength results in the distal edge 148 of the jacket 144 substantially matching the resonant length or harmonic wavelength, allowing the wire 4 to excavate a larger aperture.

[0111] 13a, 13b, and 13c show a selection of distal tip 126 configurations. Figure 13a shows a wire 4 surrounded by a radiopaque band 136 and provided with a rounded convex tip 150, for example of beryllium. Figure 13b shows a radiopaque coil 151 welded around the distal tip section 126 of the wire 4. Figure 13c shows an oversized beryllium tip 152 for increased effectiveness when traversing long calcified sections. The distal tip section 126 can be heat treated to increase its fatigue resistance.

[0112] Figures 14a, 14b, and 14c show other configurations of the distal tip 126. Figure 14a shows a looped tip 154 ​​with an outer surface that is coated or otherwise modified to optimize drilling or excavation across the loop rather than being limited to the tip. The loop can also aid in navigation to the site of the occlusion. Figure 14b shows a diamond coated tip burr 156. Figure 14c shows a drilling end tip 158 or segment coated with a diamond and / or carbide coating. Coatings and hardened materials such as these provide aggressive machining of the lesion.

[0113] In general, the wire 4 of the present invention tends to be made of a superelastic alloy such as Nitinol (nickel titanium), which is known to have preferential properties in the transmission of ultrasound waves while providing a balance of flexibility and propulsion. Linear elastic Nitinol, which has arisen from advances in processing nickel and titanium alloys, can also be used in the wire of the present invention, as can beta titanium. Surface finishes and coatings applied to the wire 4 can include resilient fluoropolymers and hydrophilic coatings to reduce friction.

[0114] Many other variations within the concept of the invention are possible. For example, the coating can be provided along separate segments of the wire, such as by coating a central section of the length of the wire and leaving distal and proximal end portions of the wire uncoated for drilling and for clamping the activation unit, respectively. Continuous and interrupted segments of coating along the length of the wire can allow for selective clamping and unclamping of the activation unit at desired locations.

[0115] A PTFE or alternative polymer jacket may be used to reduce friction and the risk of damage to the inside of the guide catheter.

[0116] A polymer jacket may be used in the distal section to improve radiopacity, or more generally to provide lubricity along the wire or to provide marking points for connection to the transducer of the activation unit.

[0117] Surface modification includes adding grooves or burrs to the surface of the distal end portion to further fragment calcified lesions, aid in excavation, and resist damage. Such features are directional, thus utilizing the direction of motion and amplifying the efficiency of cutting or abrading occlusive material. Nevertheless, individual features have smooth contours rather than sharp edges, thus avoiding damage to the vessel wall. Similarly, various materials can be applied to the wire to create additional abrasive surfaces and aid in excavating material. Such materials can effectively reduce the area of ​​the wire in contact with the lesion to facilitate cutting and prevent calcified material from impeding the vibration and movement of the wire.

[0118] When using a drawn-fill tube (DFT), the NiTi core is surrounded by a second metal with different properties, such as stainless steel, and since the relative thickness of the secondary layer can be controlled, it can be used to create marker bands for wire bonding or shaping, or to facilitate lateral restraint.

[0119] The formed alloy jacket can provide navigation and / or opacity. The use of a more ductile, compliant outer jacket can avoid the need for cold working of Nitinol and post-process heat treatment.

[0120] Potentially there could be multiple cutting planes defined by multiple lands at the distal tip or end region of the wire. This could facilitate obtaining a different and potentially more anatomically optimal distal end, as well as a second proximal land, perhaps of a larger diameter, to work better at the lesion. This is one way of creating multiple lateral drilling zones, others being different cross-sectional diameters, different tapers, and different drilling land contours.

[0121] It should be noted that many features of the various embodiments described above are not limited to only those particular embodiments, and that those skilled in the art will be able to combine features from one embodiment with features of other embodiments whenever the invention is technically possible and makes sense from a practical standpoint.

[0122] (Summary of this embodiment) The embodiments described above will be summarized below.

[0123] 1. An elongated intravascular element for crossing an obstruction in a blood vessel, said element comprising: A proximal section; a distal tip section having a smaller diameter than the proximal section; a distal tapered mid-section extending between the proximal section and the distal tip section; An elongated intravascular element, wherein the length of the tapered intermediate section is substantially λ / 2 or a sequence of λ / 4, λ / 8, ... that is a multiple or even denominator fraction of λ / 2, where λ is a wavelength of a driving frequency that produces longitudinal resonance in the element.

[0124] The elongate intravascular element is preferably such that the proximal section of the element is marked with a series of longitudinally spaced location markers to guide a user when coupling an activation unit for optimal activation of the distal tip section.

[0125] The elongate intravascular element is preferably such that the location markers are spaced substantially apart from one another by a distance of λ / 2, where λ is the wavelength of a driving frequency which creates longitudinal resonance in the element.

[0126] The elongate intravascular element is preferably such that the location marker is applied to the element by modifying a surface layer or finish of the element or by applying a coating or covering to the element.

[0127] The elongate intravascular element is preferably such that the length of the distal tip section is substantially λ / 2, or a multiple of λ / 2, where λ is the wavelength of a driving frequency that creates longitudinal resonance in the element.

[0128] The elongate intravascular element preferably has a length at the distal tip section that is substantially λ.

[0129] The elongate intravascular element preferably has a diameter at the distal tip section that is 1 / 8 to 1 / 2 the diameter of the proximal section.

[0130] The elongate intravascular element preferably has a diameter at the proximal section of between 0.014 inches and 0.035 inches (about 0.36 mm to about 0.89 mm).

[0131] The elongate intravascular element preferably has a diameter at the distal tip section of between 0.003 inches and 0.014 inches (about 0.08 mm to about 0.36 mm).

[0132] The elongate intravascular element preferably has a diameter at the distal tip section between 0.005 inches and 0.008 inches.

[0133] The elongate intravascular element preferably has a diameter at its distal tip section of substantially 0.007 inches.

[0134] The elongate intravascular element preferably has a total length that is a function or multiple of (2n+1)λ / 4, where λ is the wavelength of the driving frequency that creates longitudinal resonance in the element.

[0135] The elongate intravascular element preferably has a length of the proximal section of λ / 4+nλ / 2, where λ is the wavelength of the driving frequency which creates longitudinal resonance in the element.

[0136] The elongate intravascular element preferably has a length of the proximal section that is an odd multiple of λ / 4, where λ is the wavelength of the driving frequency that creates longitudinal resonance in the element.

[0137] The elongate intravascular element preferably comprises at least one welded joint between at least two of the sections.

[0138] The elongate intravascular element preferably has a distal tip section that is bulbous or otherwise enlarged at the distal end.

[0139] The elongate intravascular element preferably comprises a distal portion where the distal tip section is obliquely offset relative to the longitudinal axis of the wire.

[0140] The elongate intravascular element preferably has a marker band surrounding at least the distal tip section.

[0141] The elongated intravascular element preferably has a total length of 500 mm to 3000 mm.

[0142] The elongate intravascular element is preferably such that the proximal section is of substantially uniform diameter along its length.

[0143] The elongate intravascular element preferably has a length of the proximal section of between 500mm and 2900mm.

[0144] The elongate intravascular element is preferably such that the distal section is tapered or of constant diameter along its length.

[0145] The elongate intravascular element is preferably such that the length of each of the sections is a function or multiple of λ / 4, where λ is the wavelength of the driving frequency that causes longitudinal resonance of the wire.

[0146] The elongate intravascular element preferably further comprises a marker band positioned on the distal tip portion and near the distal end of the proximal section.

[0147] The elongate intravascular element preferably has a distal tip portion that is partially sheathed or coated or partially covered by the catheter, with the length of the element extending to its distal tip remaining unsheathed or uncoated.

[0148] The elongated intravascular element is preferably such that the jacket, coating or catheter extends to the resonant length or harmonic wavelength of the element.

[0149] The elongate intravascular element is preferably jacketed or coated over a central section of the length of the element and at least a portion of the proximal section is unjacketed or uncoated.

[0150] The elongate intravascular element is preferably such that the proximal section has a discontinuous, longitudinally interrupted jacket or coating.

[0151] The elongate intravascular element preferably comprises a bare wire, with at least a distal portion of the distal tip section being unjacketed or coated.

[0152] 1. An intravascular device for crossing an obstacle in a blood vessel, the device comprising an elongated intravascular element as described above, and an ultrasonic transducer mechanically coupled to the element for ultrasonically exciting the distal tip section of the element to facilitate crossing of the obstacle.

[0153] The intravascular device preferably comprises a coupling between the element and the transducer and is configured to input ultrasonic energy to the element at a drive frequency having a wavelength λ.

[0154] The intravascular device preferably has the coupling positioned substantially an odd multiple of λ / 4 from the distal tip of the element.

[0155] The intravascular device preferably has the bond positioned substantially a distance of (2n+1)λ / 4 from the distal tip of the element.

[0156] The intravascular device is preferably such that the length of the proximal portion of the wire extending proximally from the bond is substantially a multiple of λ / 2.

[0157] The intravascular device preferably has a length selected such that each of the sections has a longitudinal resonant mode at or near the drive frequency having first and second subharmonics at or near 1 / 2 and 1 / 4, respectively, of the drive frequency.

[0158] The intravascular device is preferably such that the activation unit comprises at least one visualization feature which is a reference point for alignment with a location marker or illumination and / or a window for visualizing the location marker.

[0159] 1. A method of ultrasonically exciting a distal tip section of an elongated waveguide element, the method comprising: inputting ultrasonic energy into a proximal section of the element at a drive frequency that excites longitudinal resonance of the element; generating lateral subharmonic vibrations at the distal tip section in addition to the longitudinal vibrations.

[0160] Preferably, the method includes amplifying the ultrasonic energy between the proximal section and the distal tip section.

[0161] The method preferably includes amplifying the ultrasonic energy by conveying the energy along a distal tapered mid-section extending between the proximal section and the distal tip section, the length of the mid-section being substantially λ / 2 or a progression λ / 4, λ / 8, ... that is a multiple or even denominator of λ / 2, where λ is the wavelength of the drive frequency.

[0162] Preferably the method includes damping lateral vibration of the element proximal to the distal tip section.

[0163] The method preferably includes inputting the ultrasonic energy into the proximal section using a longitudinally vibrating transducer coupled to the element.

[0164] The method preferably includes pressing the distal tip section against a barrier, such as an obstruction, and excavating a lumen through the barrier by virtue of the lateral and longitudinal vibrations of the distal tip section.

[0165] The method preferably includes expanding the lumen by virtue of lateral and longitudinal vibration of the distal tip section disposed within the lumen.

Claims

1. An intravascular device for crossing an obstacle in a blood vessel, said device comprising an elongated intravascular element; The elongated intravascular element comprises: Proximal section, a catheter sleeve, coating or jacket terminating before an unjacketed or uncoated distal tip section having a smaller diameter than said proximal section; and 、 a distal tapered mid-section extending between the proximal section and the distal tip section; the length of the distal tapered intermediate section is substantially λ / 2 or a sequence of multiples of λ / 2 or fractions with even denominators λ / 2n (where n=2, 3, ...), the length of the distal tip section is substantially λ / 2 or a multiple of λ / 2, where λ is the wavelength of a driving frequency that creates longitudinal resonance in the intravascular element; The device comprises an ultrasonic transducer mechanically coupled to the intravascular element, the ultrasonic transducer ultrasonically exciting the distal tip section of the intravascular element to facilitate passage through obstacles by activating the distal tip section to move in a primary longitudinal mode, radially, laterally and in a wave-like motion at or near the drive frequency, and through a secondary mode of a differential harmonic.

2. The device described in claim 1, wherein the diameter of the distal tip section of the intravascular element is 1 / 8 to 1 / 2 the diameter of the proximal section.

3. The device described in claim 1 or 2, wherein the intravascular element has a total length that is a function or multiple of (2n+1)λ / 4.

4. The device described in any one of claims 1 to 3, wherein the length of the proximal section of the intravascular element is λ / 4 + nλ / 2.

5. The device of claim 1, wherein the length of the proximal section of the intravascular element is an odd multiple of λ / 4.

6. A device described in any one of claims 1 to 5, wherein the distal tip section of the intravascular element has a spherical or otherwise enlarged feature at the distal end.

7. An apparatus as described in any one of claims 1 to 6, wherein the distal tip section of the intravascular element has a distal portion that is obliquely offset relative to the longitudinal axis of the intravascular element.

8. An apparatus as described in any one of claims 1 to 7, wherein a marker band surrounds at least a distal tip section of the intravascular element.

9. A device described in any one of claims 1 to 8, wherein the distal tip section of the intravascular element is tapered or of constant diameter along its length.

10. The device of claim 1, wherein the length of each of the sections of the intravascular element is a function or multiple of λ / 4.

11. An apparatus as described in any one of claims 1 to 10, further comprising a marker band positioned on a distal tip portion and near the distal end of the proximal section of the intravascular element.

12. A device described in any one of claims 1 to 11, wherein a central section of the length of the intravascular element is sheathed or coated, and at least a portion of the proximal section is unsheathed or uncoated.

13. The device described in claim 12, wherein the proximal section has a discontinuous, longitudinally interrupted outer covering or coating.

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