Intravascular filter device with piezoelectric transducer

An intravascular filter assembly is disclosed for fragmenting a thrombotic or atherosclerotic occlusion and capturing thrombotic or atherosclerotic debris within a blood vessel. The intravascular filter assembly includes an elongate shaft and an expandable filter coupled to the distal region of the elongate shaft. One or more piezoelectric elements are secured to the elongate shaft at a location proximal of the expandable filter. A conducting wire is attached to the one or more piezoelectric elements and extends toward the proximal end of the elongate shaft. The one or more piezoelectric elements are configured to generate ultrasonic waves when subjected to an electrical voltage to fragment a thrombotic or atherosclerotic occlusion within a blood vessel.

TECHNICAL FIELD

The disclosure is directed to elongated medical devices designed to fragment and capture thrombi or plaque within a blood vessel. More particularly, the disclosure is directed to an intravascular filter device including a piezoelectric transducer capable of fragmenting and capturing thrombi or plaque in a blood vessel.

BACKGROUND

Millions of people suffer from thrombotic or atherosclerotic occlusions in blood vessels. Such occlusions restrict the blood flow through the vessel, and if left untreated, these occlusions may lead to a heart attack, or even death. A variety of available medical devices have been manufactured to treat occlusions in a blood vessel within a patient's body. For example, directional atherectomy and percutaneous translumenal coronary angioplasty (PTCA) with or without stent deployment have been found useful in treating patients with coronary occlusions, as well as occlusions of other vessels. Atherectomy uses a device which physically removes plaque by cutting, pulverizing, or shaving in atherosclerotic vessels. Angioplasty utilizes an expandable balloon on a catheter which exerts a mechanical force on the vascular wall to enlarge the luminal diameter of an occluded vessel.

Atherectomy and angioplasty techniques typically include advancing one or more elongate medical devices (e.g., atherectomy cutter or angioplasty balloon catheter) along a guidewire to the site of the occlusion and then performing a therapeutic procedure at the site of the occlusion. During such a procedure, it is often necessary to exchange one medical device for a different medical device, increasing the time required to complete the procedure. Additionally, during a catheter exchange, it may be challenging to maintain the position of the guidewire without compromising guidewire access across the occlusion. In view of the aforementioned, there is an ongoing need to provide alternative apparatus, assemblies, systems and methods of treating an occlusion within a blood vessel of a patient's body.

SUMMARY

The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies.

Accordingly, one illustrative embodiment is an intravascular filter assembly for fragmenting a thrombotic or atherosclerotic occlusion and capturing thrombotic or atherosclerotic debris within a blood vessel. The vascular filter assembly includes an elongate shaft and an expandable filter coupled to the distal region of the elongate shaft. The filter includes a support hoop forming a proximal mouth and a filter mesh attached to the support hoop. One or more piezoelectric elements are secured to the elongate shaft at a location proximal of the expandable filter. A conducting wire is attached to the one or more piezoelectric elements and extends toward the proximal end of the elongate shaft. The one or more piezoelectric elements are configured to generate ultrasonic waves to fragment a thrombotic or atherosclerotic occlusion within a blood vessel.

Another illustrative embodiment is an intravascular filter assembly for fragmenting a thrombotic or atherosclerotic occlusion and capturing thrombotic or atherosclerotic debris within a blood vessel. The vascular filter assembly includes a guidewire including an elongate core wire having a distal end, a proximal end, and a distal tip including a helical coil disposed at the distal end of the elongate core wire; and a filter including a filter hoop defining a proximal mouth of the filter, a filter mesh attached to the filter hoop, and at least one strut extending from the filter hoop to the elongate core wire for coupling the filter to the guidewire. A plurality of piezoelectric elements are secured to the elongate core wire at a location proximal of the filter, wherein each of the plurality of piezoelectric elements are longitudinally spaced away from an adjacent piezoelectric element. A conducting wire is connected to each of the piezoelectric elements and extends proximally along the elongate core wire from the plurality of piezoelectric elements. A length of insulating material is disposed on the elongate core wire intermediate the filter and the plurality of piezoelectric elements.

Yet another illustrative embodiment is a method of fragmenting a thrombotic or atherosclerotic occlusion and capturing thrombotic or atherosclerotic debris within a blood vessel. The method includes providing a guidewire including an elongate core wire and an expandable filter coupled to a distal region of the guidewire. The guidewire includes one or more piezoelectric elements positioned on the elongate core wire at a location proximal of the expandable filter. The guidewire is positioned in a blood vessel such that the one or more piezoelectric elements are adjacent a thrombotic or atherosclerotic occlusion within the blood vessel. The filter is then expanded at a location downstream of the thrombotic or atherosclerotic occlusion. An electrical current is transmitted along the guidewire to the one or more piezoelectric elements, generating ultrasonic waves with the piezoelectric elements. The ultrasonic waves resonating from the piezoelectric elements fragment the thrombotic or atherosclerotic occlusion within the blood vessel. Fragmented thrombotic or atherosclerotic debris is captured in the filter. At the completion of the ultrasonic fragmenting process, the intravascular filter device may be withdrawn from the blood vessel.

The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the invention.

DETAILED DESCRIPTION

An exemplary intravascular filter device10is illustrated inFIG. 1. The device includes a guidewire12having an elongate core wire14extending from a proximal end16to a distal end18. The distal end18of the guidewire12may include a distal tip20, such as a helical coil, attached to the distal end of the elongate core wire14.

The elongate core wire14, which may have a solid cross-section or a hollow cross-section, may be made from a variety of suitable materials. In some embodiments, the elongate core wire14may be formed of an electrically conductive material. For example, the core wire14may be made from a metal, a metal alloy, or any other suitable material. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; titanium or titanium alloys; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; combinations thereof; and the like; or any other suitable material.

In at least some embodiments, portions or all of the elongate core wire14, distal tip20and/or other components of the guidewire12may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of the intravascular filter device10in determining its location within a blood vessel. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymeric material loaded with a radiopaque filler, and the like.

A filter22, configured for capturing thrombotic or atherosclerotic fragments suspended in the blood stream, may be coupled to a distal region of the guidewire12. Some examples of suitable filters which may be used include those disclosed in U.S. Pat. Nos. 7,094,249 and 6,245,089, the disclosures of which are incorporated herein by reference.

The intravascular filter device10may also include a piezoelectric transducer24including one or more piezoelectric elements26secured to the guidewire12. The piezoelectric transducer24may be positioned at a location proximal of the filter22. In some embodiments, an insulative (e.g., non-conductive) material28may be disposed on the outside surface of the guidewire12(e.g., on the outside surface of the elongate core wire14) at a location intermediate the filter22and the piezoelectric transducer24. The insulative material28may prevent the filter22from experiencing ultrasonic vibrations generated from the piezoelectric transducer24. In some embodiments, the insulative material28may comprise a polymer, such as polyether block amide (PEBA), polytetraflouroethylene (PTFE), polyamide, polyether-ester, polyurethane, polypropylene, polyethylene, or other suitable polymeric materials, or mixtures, combinations, copolymers, and the like.

A conducting wire30may extend distally from the proximal end16of the guidewire12to the piezoelectric transducer24. In some embodiments, the conducting wire30may be formed of an electrically conducting material, such as stainless steel, gold, tungsten, titanium, or a nickel-titanium alloy, such as nitinol. As shown inFIG. 1, the conducting wire30may be helically wound around a length of the elongate core wire14of the guidewire12. In other embodiments, the conducting wire30may longitudinally extend along a length of the elongate core wire14, or extend along a length of the elongate core wire14in any other desired fashion.

An electronic control unit32may also be present for generating an electrical current to activate ultrasonic vibrations of the piezoelectric transducer24. The electronic control unit32, which may generate an alternating current, may include a first terminal34and a second terminal36. In some embodiments, the conducting wire30, used as a first electrode, may be electrically connected to the first terminal34of the electronic control unit32. Furthermore, the elongate core wire14, used as a second electrode, may be electrically connected to the second terminal36of the electronic control unit32. Thus, an alternating electrical current may be transmitted from the electrical control unit32distally to the piezoelectric elements26of the piezoelectric transducer24and back to the electrical control unit32proximally through the electrical circuit established through the elongate core wire14and the conducting wire30. Thus, the electronic control unit32may apply a voltage across the piezoelectric elements26between the outer surface of the piezoelectric elements26and the inner surface of the piezoelectric elements26.

In other embodiments, instead of passing an electrical current, such as an alternating electrical current, through the elongate core wire14, the intravascular filter device10may include two conducting wires extending along the guidewire12, a first conducting wire electrically connected to the inner surface of the piezoelectric elements26of the piezoelectric transducer24, and a second conducting wire connected to the outer surface of the piezoelectric elements26of the piezoelectric transducer24. Thus, an alternating current may be transmitted from the electrical control unit32distally to the piezoelectric elements26of the piezoelectric transducer24and back to the electrical control unit32proximally through the electrical circuit established through the first conducting wire and the second conducting wire extending along the guidewire12. Thus, the electronic control unit32may apply a voltage across the piezoelectric elements26.

As the electrical current passes through the piezoelectric elements26of the piezoelectric transducer24, a voltage forms across the piezoelectric elements26, exciting the molecules of the piezoelectric elements26. As the molecules are excited by the applied voltage, the dimensions of the piezoelectric elements26are changed. Dimensional changes in the piezoelectric elements26generate ultrasound waves propagating from the piezoelectric element26. The ultrasound waves may be longitudinal waves, shear waves, or a combination of longitudinal waves and shear waves. As discussed later herein, the ultrasound waves generated by the piezoelectric elements26may be used to fragment plaque and/or thrombi within a blood vessel.

The electrical current, and thus the voltage, across the piezoelectric elements26can be varied to generate ultrasonic vibrations at a desired frequency. For example, in some embodiments it may be desirable to generate ultrasonic vibrations at a frequency of 400 kHz or less, at a frequency of 300 kHz or less, or at a frequency of 200 kHz or less. In some embodiments, ultrasonic vibrations may be generated at about 200 kHz to about 400 kHz, at about 200 kHz to about 300 kHz, at about 300 kHz to about 400 kHz, or about 350 kHz to about 400 kHz, for example. In some embodiments, ultrasonic vibrations may be generated at about 400 kHz, at about 350 kHz, at about 300 kHz, at about 250 kHz, or at about 200 kHz, for example. It is noted that the chosen material and thickness of the piezoelectric elements26are dependent on the desired frequency of operation. An operator may use the electrical control unit32to select and/or control the desired frequency of ultrasonic waves and/or the desired power generated. For example, the operator may select and/or control the frequency and/or magnitude of the electrical current transmitted to the piezoelectric elements26with the electrical control unit32.

FIG. 2is an enlarged view of a portion of the intravascular filter device10further illustrating the piezoelectric elements26of the piezoelectric transducer24attached to the guidewire12. As shown inFIG. 2, the piezoelectric transducer24may include three piezoelectric elements26secured to the elongate core wire14of the guidewire12. However, in other embodiments the piezoelectric transducer24may include any number of piezoelectric elements26. For example, in some embodiments the piezoelectric transducer may include one, two, four, five, six or more piezoelectric elements26secured to the elongate core wire14of the guidewire12.

The piezoelectric elements26may be formed of any desired piezoelectric material. A piezoelectric material is a material having a crystalline micro-structure, such as a crystal, ceramic or polymer, which is permanently polarized such that the material will produce voltage in response to a dimension-changing mechanical force, or conversely, will undergo dimensional changes in response to an applied voltage. In this way piezoelectric materials are similar to electrostrictive materials. Some suitable piezoelectric materials include quartz, barium titanate, lead zirconate titanate (known as PZT), lead niobate, and polyvinylidene fluoride (PVDF).

The piezoelectric elements26may have any size, shape and/or configuration as desired. For example, as shown inFIG. 2, the piezoelectric elements26may be circular or annular rings extending around the circumference of the elongate core wire14of the guidewire12. In other embodiments, the piezoelectric elements26may be strips or segments of piezoelectric material extending longitudinally, helically, circumferentially, or at another desired orientation on the elongate core wire14. The piezoelectric elements26may be fixed to the elongate core wire14by any suitable means. For example, in some embodiments the piezoelectric elements26may be secured to the elongate core wire14with an interference fit between the inner surface of the piezoelectric elements26and the outer surface of the elongate core wire14. In other embodiments, the piezoelectric elements26may be welded, crimped or swaged to the elongate core wire14.

The piezoelectric elements26may have an outer surface40and an opposing inner surface42. For instance, in embodiments in which the piezoelectric elements26are annular rings, the outer surface40may be an outer peripheral surface of the piezoelectric element26, and the inner surface42may be an inner peripheral surface of the piezoelectric element26. The inner surface42of the piezoelectric elements26may be in contact with the outer surface44of the elongate core wire14, and the outer surface40of the piezoelectric elements26may be in contact with the conducting wire30. Thus, an applied electrical voltage may be generated across the piezoelectric elements26between the outer surface40and the inner surface42of the piezoelectric elements26.

The conducting wire30may be connected to each of the piezoelectric elements26as the conducting wire30extends distally along the guidewire12. For instance, the conducting wire30may be connected to a first piezoelectric element26along a first helical turn of the conducting wire30. As the conducting wire30extends further distally, the conducting wire30may be connected to a second piezoelectric element26along a second helical turn of the conducting wire30. And as the conducting wire30extends further distally, the conducting wire30may be connected to a third piezoelectric element26along a third helical turn of the conducting wire30, etc. The conducting wire30may be connected to the piezoelectric elements26in any desired way. For example, the conducting wire30may be welded (e.g., laser welding or ultrasonic welding) to the piezoelectric elements26, or the piezoelectric elements26may include one or more grooves or channels in which the conducting wire30may be placed in or along to connect the conducting wire30to the piezoelectric elements26.

In embodiments in which the piezoelectric elements26are annular rings, the piezoelectric elements26may have an inner diameter D1, and outer diameter D2, and a radial thickness T (T=½(D2−D1). Thus, in embodiments when the piezoelectric elements26are secured to the elongate core wire14such that the inner surface42of the piezoelectric elements26is in contact with the outer surface44of the elongate core wire14, the inner diameter D1of the piezoelectric elements26may be substantially equal to the outer diameter of the elongate core wire at the longitudinal location of the piezoelectric elements26. In some embodiments the thickness T of the piezoelectric elements26may be about 40 to about 60 micrometers (i.e., about 0.04 millimeters to about 0.06 millimeters), or about 50 micrometers (i.e., about 0.05 millimeters). As mentioned above the ultrasonic frequency generated by the piezoelectric elements26may be dictated, at least in part, by the thickness T of the piezoelectric elements26.

Each of the piezoelectric elements26may have a longitudinal length L of about 2 to about 6 millimeters or about 3 to about 5 millimeters. In some embodiments, the longitudinal length L of each of the piezoelectric elements26may be about 3 millimeters, about 4 millimeters, or about 5 millimeters, for example.

Furthermore, as shown inFIG. 2, each of the piezoelectric elements26may be longitudinally spaced away from an adjacent piezoelectric element26by a distance X. For instance, a first piezoelectric element26may be longitudinally spaced away from a second, adjacent piezoelectric element26by a distance X of about 1 to about 3 millimeters or about 1 to about 2 millimeters.

The filter22coupled to the guidewire12is further illustrated inFIGS. 3 and 4. The filter22may include a support hoop46defining a proximal mouth48of the filter22. In some embodiments, the support hoop46may centrically encircle the guidewire12or the support hoop46may eccentrically encircle the guidewire12. In other embodiments, the support hoop46may be offset such that the support hoop46may be directly connected to the guidewire12. The support hoop46may be biased to radially expand within a blood vessel when removed from a delivery tube.

The filter22may also include a filter mesh50attached to the support hoop46. For example, a proximal rim of the filter mesh50may be attached to the perimeter of the support hoop46. In some embodiments the filter mesh50may include a plurality of wound, twisted, woven, interconnected, braided and/or overlapping fibers or wires. In other embodiments, the filter mesh50may include a microporous membrane or other suitable filtering or netting-type material. The filter mesh50may include a plurality of openings or pores52configured to allow the flow of blood therethrough, while filtering debris (e.g., thrombotic or atherosclerotic debris) suspended in the bloodstream. The distal end of the filter mesh50may also be attached to the guidewire12.

The filter22may additionally include one or more, or a plurality of struts coupling the support hoop46to the guidewire12. For example, as shown inFIGS. 3 and 4, the filter22may include a strut54extending between the support hoop46and the guidewire12. As shown inFIG. 3, the strut54may be attached to the guidewire12exterior of the insulative material28such that any vibrations or electrical current passing through the elongate core wire14of the guidewire12will not be transmitted to the support hoop46and/or other components of the filter22.

FIGS. 5A-5Care three alternative cross-sectional views taken transverse to the longitudinal axis of the guidewire12at a location proximal of the piezoelectric transducer24. As shown in the figures, the conducting wire30is electrically insulated and/or isolated from the elongate core wire14of the guidewire12. As illustrated in FIG. SA, in some embodiments the elongate core wire14may be surrounded with or encased with an insulative layer56to insulate the elongate core wire14and/or isolate the elongate core wire14from the conducting wire30. As illustrated inFIG. 5B, in other embodiments the conducting wire30may be surrounded with or encased with an insulative layer58to insulate conducting wire30and/or isolate the conducting wire30from the elongate core wire14. As illustrated inFIG. 5C, in yet other embodiments the conducting wire30and the elongate core wire14may both be surround by or encased within an insulative layer60, insulating and/or isolating the conducting wire30from the elongate core wire14. Thus, an insulative layer56,68,60may be located between the elongate core wire14and the conducting wire30to prevent an electrical current from shorting across between the elongate core wire14and the conducting wire30.

Another exemplary intravascular filter device110is illustrated inFIG. 6. The device includes a guidewire112having an elongate core wire114extending from a proximal end116to a distal end118. The distal end118of the guidewire112may include a distal tip120, such as a helical coil, attached to the distal end of the elongate core wire114.

The elongate core wire114, which may have a solid cross-section or a hollow cross-section, may be made from a variety of suitable materials. In some embodiments, the elongate core wire114may be formed of an electrically conductive material. For example, the core wire114may be made from a metal, a metal alloy, or any other suitable material. Some examples of suitable metals and metal alloys include those listed above regarding the elongate core wire14. Furthermore, in at least some embodiments, portions or all of the elongate core wire114, distal tip120and/or other components of the guidewire112may also be doped with, made oft or otherwise include a radiopaque material.

A filter122, configured for capturing fragments suspended in the blood stream, may be coupled to a distal region of the guidewire112. In some embodiments the filter122may substantially resemble the filter22as describe above. For instance, the filter122may include a support hoop146, a filter mesh150attached to the support hoop146, and at least one strut154coupling the support hoop146of the filter122to the guidewire112. In the interest of brevity, further discussion of the filter122will not be reiterated.

The intravascular filter device110may also include a piezoelectric transducer124including one or more piezoelectric elements126secured to the guidewire112. The piezoelectric transducer124is positioned at a location proximal of the filter122. In some embodiments, an insulative (e.g., non-conductive) material128may be disposed on the outside surface of the guidewire112(e.g., on the outside surface of the elongate core wire114) at a location intermediate the filter122and the piezoelectric transducer124. The insulative material128may prevent the filter122from experiencing vibrations generated from the piezoelectric transducer124. In some embodiments, the insulative material128may comprise a polymer, such as polyether block amide (PEBA), polytetraflouroethylene (PTFE), polyamide, polyether-ester, polyurethane, polypropylene, polyethylene, or other suitable polymeric materials, or mixtures, combinations, copolymers, and the like.

A conducting wire130may be secured to and extend proximally from the piezoelectric elements126of the piezoelectric transducer124toward the proximal end116of the guidewire112. For example, the conducting wire130may be secured to the outer surface of each of the piezoelectric elements126. In some embodiments, the conducting wire130may be formed of an electrically conducting material, such as stainless steel, gold, tungsten, titanium, or a nickel-titanium alloy, such as nitinol. As shown inFIG. 6, the conducting wire130may be helically wound around a length of the elongate core wire114of the guidewire112. In other embodiments, the conducting wire130may longitudinally extend along a length of the elongate core wire114.

An electronic control unit132may also be present for generating an electrical current to activate ultrasonic vibrations of the piezoelectric transducer124. The electronic control unit132, which may generate an alternating current, may include a first terminal134and a second terminal136. In some embodiments, the conducting wire130, used as a first electrode, may be electrically connected to the first terminal134of the electronic control unit132. Furthermore, the elongate core wire114, used as a second electrode, may be electrically connected to the second terminal136of the electronic control unit132. Thus, an alternating electrical current may be transmitted from the electrical control unit132distally to the piezoelectric elements126of the piezoelectric transducer124and back to the electrical control unit132proximally through the electrical circuit established through the elongate core wire114and the conducting wire130. Thus, the electronic control unit132may apply a voltage across the piezoelectric elements126.

It is noted that in other embodiments, instead of passing an electrical current, such as an alternating electrical current, through the elongate core wire114, the intravascular filter device10may include two conducting wires extending along the guidewire112, a first conducting wire electrically connected to the inner surface of the piezoelectric elements126of the piezoelectric transducer124, and a second conducting wire connected to the outer surface of the piezoelectric elements126of the piezoelectric transducer124. Thus, an alternating current may be transmitted from the electrical control unit132distally to the piezoelectric elements126of the piezoelectric transducer124and back to the electrical control unit132proximally through the electrical circuit established through the first conducting wire and the second conducting wire extending along the guidewire112. Thus, the electronic control unit132may apply a voltage across the piezoelectric elements126.

As the electrical current passes through the piezoelectric elements126of the piezoelectric transducer124, a voltage forms across the piezoelectric elements126, exciting the molecules of the piezoelectric elements126. As the molecules are excited by the applied voltage, the dimensions of the piezoelectric elements126are changed. Dimensional changes in the piezoelectric elements126generate ultrasound waves propagating from the piezoelectric element126. The ultrasound waves may be longitudinal waves, shear waves, or a combination of longitudinal waves and shear waves. As discussed later herein, the ultrasound waves generated by the piezoelectric elements126may be used to fragment plaque and/or thrombi within a blood vessel.

The electrical current, and thus the voltage, across the piezoelectric elements126can be varied to generate ultrasonic vibrations at a desired frequency. For example, in some embodiments it may be desirable to generate ultrasonic vibrations at a frequency of 400 kHz or less, at a frequency of 300 kHz or less, or at a frequency of 200 kHz or less. In some embodiments, ultrasonic vibrations may be generated at about 200 kHz to about 400 kHz, at about 200 kHz to about 300 kHz, at about 300 kHz to about 400 kHz, or about 350 kHz to about 400 kHz, for example. In some embodiments, ultrasonic vibrations may be generated at about 400 kHz, at about 350 kHz, at about 300 kHz, at about 250 kHz, or at about 200 kHz, for example. It is noted that the chosen material and thickness of the piezoelectric elements126are dependent on the desired frequency of operation. An operator may use the electrical control unit132to select and/or control the desired frequency of ultrasonic waves and/or the desired power generated. For example, the operator may select and/or control the frequency and/or magnitude of the electrical current transmitted to the piezoelectric elements126with the electrical control unit132.

The intravascular filter device110also may include a hypotube170extending along a proximal portion of the guidewire112proximal of the piezoelectric transducer124. As may be better seen fromFIG. 7, which is an enlarged view of a portion of the guidewire112including the hypotube170, the hypotube170may be a metallic tubular member having a plurality of slots172cut into the wall of the metallic tubular member to impart desired flexibility characteristics to the metallic tubular member.

As shown inFIG. 7, the hypotube170may be spaced away from the elongate core wire114and secured in place by one or more spacers. For example, a first spacer180may be used to secure the proximal end174of the hypotube170, and a second spacer182may be used to secure the distal end176of the of the hypotube170. One or more additional spacers may be located at locations intermediate the proximal end174and the distal end176of the hypotube170to further secure the hypotube170in place.

The conducting wire130may extend through the lumen178of the hypotube170, such that the conducting wire130is enclosed within the hypotube170. Thus, the conducting wire130may be protected from contacting other structures, such as other medical devices and/or the inner surface of a blood vessel. An insulating layer156may separate the conducting wire130from the elongate core wire114of the guidewire112. As shown inFIG. 7, the insulating layer156may be disposed around the outer surface of the elongate core wire114. However, as discussed above, in other embodiments, the conducting wire130may alternatively or additionally be surrounded by an insulating layer.

An alternative embodiment of the proximal portion of the intravascular filter device110is illustrated inFIG. 8. The proximal portion of the intravasucular filter device110includes a hypotube170including a plurality of slots172formed therein to provide the hypotube170with desired flexibility characteristics. In this embodiment the conducting wire130is discontinuous, having a distal length192distal of the hypotube170and a proximal length194proximal of the hypotube170. As shown inFIG. 8, the distal length192of the conducting wire130is connected to the distal end176of the hypotube170and the proximal length194of the conducting wire130is connected to the proximal end174of the hypotube170. For example, the ends of the conducting wire130may be welded to the hypotube170. Thus, an electrical current may pass through the hypotube170, which may be formed of an electrically conductive material such as those disclosed above, between the proximal length194and the distal length192of the conducting wire130. Spacers180,182may be used to space the hypotube170from the elongate core wire114and/or secure the hypotube170in place along the guidewire112. Additionally, an insulating layer156may separate the conducting wire130and/or the hypotube170from the elongate core wire114of the guidewire112.

A method for fragmenting and capturing thrombi or plaque within a blood vessel using the intravascular filter device10will now be illustrated inFIGS. 9A-9E. As shown inFIG. 9A, the intravascular filter device10may be initially advanced through a blood vessel200within a delivery sheath210. The filter22may be delivered in a collapsed configuration within the lumen212of the delivery sheath210. The delivery sheath210, with the intravascular filter device10disposed within the lumen212of the delivery sheath210, may be advanced through the blood vessel200until the piezoelectric transducer24of the intravascular filter device10is positioned adjacent an occlusion202, such as an thrombotic or atherosclerotic occlusion, on the interior wall of the blood vessel200. With the piezoelectric transducer24positioned adjacent the occlusion202, the filter22coupled to the guidewire12distal of the piezoelectric transducer24is located at a location distal of the occlusion202.

Once the piezoelectric transducer24is positioned adjacent the occlusion202, the delivery sheath210may be withdrawn proximally, allowing the filter22to expand into a deployed configuration as shown inFIG. 91B. In the deployed configuration, the support hoop46of the filter22may substantially extend across the lumen of the blood vessel200with the proximal mouth48facing the occlusion202. With the filter22deployed, the piezoelectric elements26of the piezoelectric transducer24may remain positioned adjacent the occlusion202. Thus, in some embodiments, the filter22may be expanded into the deployed configuration subsequent to positioning the piezoelectric elements adjacent the occlusion202.

An electrical current (e.g. an alternating electrical current) may then be transmitted along the guidewire12to the piezoelectric elements26from the electronic control unit32(not shown) to activate the piezoelectric transducer24. For example, an electrical pathway may be formed extending from the electronic control unit32distally along the conducting wire30, across the piezoelectric elements26, and proximal along the elongate core wire14back to the electronic control unit32.

Voltage across the piezoelectric elements26excites the piezoelectric elements26, generating ultrasonic waves220resonating from the piezoelectric elements26. In some embodiments, the ultrasonic waves220generated by the piezoelectric elements26by the vibrations of the piezoelectric elements26may be longitudinal waves, shear waves, or a combination of longitudinal and shear waves. The frequency of the ultrasonic waves220may be controlled by adjusting the voltage across the piezoelectric elements26as desired. For example, the electrical current, and thus the voltage, across the piezoelectric elements26can be varied to generate ultrasonic waves220at a desired frequency. For instance, in some embodiments it may be desirable to generate ultrasonic waves220at a frequency of 400 kHz or less, at a frequency of 300 kHz or less, or at a frequency of 200 kHz or less. In some embodiments, ultrasonic waves220may be generated at about 200 kHz to about 400 kHz, at about 200 kHz to about 300 kHz, at about 300 kHz to about 400 kHz, or about 350 kHz to about 400 kHz, for example. In some embodiments, ultrasonic waves220may be generated at about 400 kHz, at about 350 kHz, at about 300 kHz, at about 250 kHz, or at about 200 kHz, for example. An operator may use the electrical control unit32to select and/or control the desired frequency of ultrasonic waves220and/or the desired power generated. For example, the operator may select and/or control the frequency and/or magnitude of the electrical current transmitted to the piezoelectric elements26with the electrical control unit32.

As shown inFIG. 9C, the ultrasonic waves220propagate toward the occlusion202, fragmenting the tissue (e.g., plaque and/or thrombi) forming the occlusion202into small fragments230of debris. The thrombotic or atherosclerotic fragments230broken away from the vessel wall200are suspended in the bloodstream and float downstream. The filter22, positioned downstream (e.g., distal) of the occlusion202, extends across the vessel200to capture the fragments230suspended in the bloodstream. Fragments230enter the filter22through the proximal mouth48defined by the support hoop46of the filter22and are retained by the filter mesh50, while allowing blood to flow through.

As shown inFIG. 9D, ultrasonic waves generated from vibrations of the piezoelectric elements26reduce and/or eliminate the occlusion202in the blood vessel200, thus reducing any restrictions of blood flow through the lumen of the blood vessel200. The filter22, containing captured fragments230of debris (e.g., thrombotic or atherosclerotic debris) from the occlusion202, prevents fragments230from flowing to other regions of the vasculature, such as the heart, lungs and/or brain of the patient.

After completing the application of ultrasonic vibrations waves in which the fragments230are captured in the filter22, a retrieval sheath240may be advanced distally over the guidewire12. The distal end242of the retrieval sheath240may be passed distally over at least a portion of the filter22, such that the filter22is at least partially collapsed within the lumen244of the retrieval sheath240. Thus, the collapsed filter22, including the captured thrombotic or atherosclerotic fragments230, and the piezoelectric transducer24disposed on the guidewire12may be retained within the lumen244of the retrieval sheath240. The intravascular filter device10may then be withdrawn from the blood vessel200at the completion of the medical procedure.