# Patent

## Title
Ultrasound ablation catheter with cooling infusion and centering basket

## Abstract

Systems for nerve and tissue modulation are disclosed. An illustrative system may include an intravascular nerve modulation system including a catheter shaft, a first flexible mount, and a cylindrical ablation transducer. The ablation transducer may be affixed to the catheter shaft through the flexible mount to allow an infusion fluid to pass through a lumen of the transducer. Another illustrative system may include an intravascular nerve modulation system including an expandable basket for centering an ablation tra7nsducer within a lumen.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/891,241, filed Oct. 15, 2013, the entirety of which is incorporated herein by reference.


TECHNICAL FIELD
The present disclosure relates generally to systems and methods for nerve modulation techniques such as ablation of nerve tissue or other modulation techniques through the walls of blood vessels.
BACKGROUND
Certain treatments may require the temporary or permanent interruption or modification of selected nerve function. One exemplary treatment is renal nerve ablation, which is sometimes used to treat conditions related to congestive heart failure or hypertension. The kidneys produce a sympathetic response to congestive heart failure, which, among other effects, increases the undesired retention of water and/or sodium. Ablating some of the nerves running to the kidneys may reduce or eliminate this sympathetic function, which may provide a corresponding reduction in the associated undesired symptoms.
Many nerves (and nervous tissue such as brain tissue), including renal nerves, run along the walls of or in close proximity to blood vessels and thus can be accessed intravascularly through the walls of the blood vessels. In some instances, it may be desirable to ablate perivascular nerves using ultrasonic energy. In other instances, the perivascular nerves may be ablated by other means including application of thermal, radiofrequency, laser, microwave, and other related energy sources to the target region. Ultrasound transducers may dissipate some energy as heat into the blood and surrounding tissue as well as causing the ultrasound transducers to become hot. This may result in blood damage, clotting, and/or protein fouling of the transducer among other undesirable side effects. In some instances, overheating of the ultrasound transducer may result in the failure of the transducers.
SUMMARY
The present disclosure is directed to an intravascular nerve modulation system for performing nerve ablation.
Accordingly, one illustrative embodiment includes an intravascular nerve modulation system having a catheter shaft. The catheter shaft may define a first lumen and having a proximal end and a distal end. Further, the system includes a first flexible mount member affixed to the distal end of the catheter shaft and defining one or more through holes. Furthermore, the system includes a cylindrical ablation transducer coupled to the first flexible mount and defining a lumen extending distally from the first flexible mount. Here, the lumen of the catheter shaft, the through holes of the first flexible mount member, and the lumen of the transducer are in fluid communication with one another.
Another illustrative embodiment includes an intravascular nerve modulation system that may include an elongate shaft having a proximal end, a distal end, and a lumen extending therebetween. Further, the system may include an ablation transducer affixed to the elongate shaft adjacent the distal end thereof. Furthermore, the intravascular modulation system may include an expandable basket having a proximal end affixed to the elongate shaft and a distal end affixed to an end cap positioned distal of a distal end of the ablation transducer. Here, the expandable basket may be configured to actuate between a first collapsed configuration and a second expanded configuration. In addition, the expandable basket can include two or more longitudinally extending struts and one or more temperature sensors may be coupled to the expandable basket. The system can further include a pull wire affixed to the end cap such that actuation of the pull wire moves the expandable basket between the first collapsed position and the second expanded position. Alternatively, the expandable basket may be configured to self-expand. The system can further include an infusion sheath secured adjacent to the distal end of the elongate tubular member such that the infusion sheath is configured to extend over the ablation transducer. In some instances, the distal end of the expandable basket may be affixed to the elongate shaft.
Another example intravascular nerve modulation system may include an elongate shaft having a proximal end region and a distal end region. An ablation transducer may be coupled to the distal end region of the shaft. An expandable basket may be coupled to the distal end region of the shaft. The expandable basket may have a proximal end dispsoed proximal of the ablation transducer and a distal end disposed distal of the ablation transducer. The expandable basket may be capable of shifting between a first configuration and an expanded configuration. A sensor may be coupled to the expandable basket.
Another example intravascular nerve modulation system may include an elongate shaft having a proximal end region and a distal end region. An ultrasound transducer may be coupled to the distal end region of the shaft. An expandable basket may be coupled to the distal end region of the shaft. The expandable basket may have a proximal end disposed proximal of the ultrasound transducer and a distal end disposed distal of the ultrasound transducer. The expandable basket may be capable of shifting between a first configuration and an expanded configuration. A sensor may be coupled to the expandable basket. The sensor may be capable of contacting a vessel wall when the basket is in the expanded configuration. The sensor may also be designed to monitor the progress of ablation by the ultrasound transducer during an ablation procedure.
Although discussed with specific reference to use with the renal nerves of a patient, the intravascular nerve modulation systems in accordance with the disclosure may be adapted and configured for use in other parts of the anatomy, such as the nervous system, the circulatory system, or other parts of the anatomy of a patient.
The above summary of an example embodiment is not intended to describe each disclosed embodiment or every implementation of the present disclosure.



BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which:
FIG. 1 illustrates an exemplary renal nerve modulation system in situ.
FIG. 2 illustrates a schematic side-view of a portion of an illustrative intravascular nerve modulation system disposed within a body lumen.
FIG. 3A illustrates a schematic side-view of a portion of another illustrative intravascular nerve modulation system in a collapsed configuration.
FIG. 3B illustrates a schematic side-view of the intravascular nerve modulation system of FIG. 3A in an expanded configuration.
FIG. 4 illustrates a schematic side-view of a portion of another illustrative intravascular nerve modulation system.
FIG. 5 illustrates a schematic side-view of a portion of another example of an intravascular nerve modulation system disposed within a body lumen.
FIG. 6 illustrates a cross-sectional view of a portion of another illustrative intravascular nerve modulation system.
FIG. 7 illustrates a cross-sectional view of the illustrative nerve modulation system of FIG. 6.



While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
DETAILED DESCRIPTION
For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.
All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may be indicative as including numbers that are rounded to the nearest significant figure.
The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4 , and 5).
Although some suitable dimensions ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of the skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed.
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
For purposes of this disclosure, “proximal” refers to the end closer to the device operator during use, and “distal” refers to the end further from the device operator during use.
The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.
It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with one embodiment, it should be understood that such feature, structure, or characteristic may also be used connection with other embodiments whether or not explicitly described unless clearly stated to the contrary.
Certain treatments are aimed at the temporary or permanent interruption or modification of select nerve function. In some instances, the nerves are sympathetic nerves. One example treatment is renal nerve ablation, which is sometimes used to treat conditions related to hypertension, congestive heart failure, diabetes, or other conditions impacted by high blood pressure or salt retention. The kidneys produce a sympathetic response to congestive heart failure, which, among other effects, increases the undesired retention of water and/or sodium. Ablating some of the nerves running to the kidneys may reduce or eliminate this sympathetic function, which may provide a corresponding reduction in the associated undesired symptoms.
Some embodiments of the present disclosure relate to a power generating and control apparatus, often for the treatment of targeted tissue in order to achieve a therapeutic effect. In some embodiments, the target tissue is tissue containing or proximate to nerves. In one embodiment, the target tissue includes renal arteries and associated renal nerves. In other embodiments, the target tissue is sympathetic nerves including, for example, sympathetic nerves disposed adjacent to blood vessels. In still other embodiments the target tissue is luminal tissue, which may further comprise diseased tissue such as that found in arterial disease.
While the systems and methods described herein are discussed relative to renal nerve modulation, it is contemplated that the systems and methods may be used in other locations and/or applications where nerve modulation and/or other tissue modulation including heating, activation, blocking, disrupting, or ablation are desired, such as, but not limited to: blood vessels, urinary vessels, or in other tissues via trocar and cannula access. For example, the devices and methods described herein can be applied to hyperplastic tissue ablation, tumor ablation, benign prostatic hyperplasia therapy, nerve excitation or blocking or ablation, modulation of muscle activity, hyperthermia or other warming of tissues, etc. In some instances, it may be desirable to ablate perivascular renal nerves with ultrasound ablation. The term modulation refers to ablation and other techniques that may alter the function of affected nerves.
Ultrasound energy may be used to generate heat at a target location. The high frequency acoustic waves produced by an ultrasonic transducer may be directed at a target region and absorbed at the target region. As the energy emitted is absorbed, a temperature of the target region may rise. In order to perform renal nerve ablation, target nerves should be heated sufficiently to make them nonfunctional, while thermal injury to the artery wall is undesirable. Heating of the artery wall during the procedure may increase pain, which is also undesirable. When a portion of tissue is ablated, tissue properties change, and increased attenuation of the ultrasound energy can make ablation past this ablated tissue difficult. Ultrasound ablation catheters may also generate significant heat in the ultrasound transducer. That heat may consequently form blood clots on or around the transducer, damage the surrounding blood, and/or damaging the transducers, among other undesirable side effects. As the ablation transducer(s) heat, the energy conversion efficiency of those devices is lowered, thus generating even more heat. Thus, normal operations of ablation transducers may be characterized by increasingly lower efficiency during operation. The efficiency of the ablation transducers may be enhanced using a cooling mechanism. One possible cooling mechanism is passing an infusion fluid over the transducers.
FIG. 1 is a schematic view of an illustrative nerve modulation system 100 in situ. The nerve modulation system 100 may include an element 102 for providing power to a transducer disposed adjacent to, about, and/or within a central elongated shaft 104 and, optionally, within a guide catheter 106. A proximal end of the element 102 may be connected to a power and control element 108, which supplies the necessary electrical energy to activate the one or more transducers at or near a distal end of the element 102. The power and control element 108 may include monitoring elements to monitor parameters such as power, temperature, voltage, pulse size and/or frequency and other suitable parameters as well as suitable controls for performing the desired procedure. In some instances, the control unit 108 may control an ultrasound ablation transducer. The ablation transducer may be configured to operate at a frequency of about 9-10 megahertz (MHz). It is contemplated that any desired frequency may be used, for example, from 1-20 MHz. In addition, it is contemplated that frequencies outside this range may also be used, as desired. While the term “ultrasound” is used herein, this is not meant to limit the range of vibration frequencies contemplated. For example, it is contemplated that the perivascular nerves may be ablated by other means including application of thermal, radiofrequency, laser, microwave, and other related energy sources to the target region.
FIG. 2 illustrates a schematic side view of a distal end portion of an illustrative intravascular nerve modulation system 200 disposed within a body lumen 204 having a vessel wall 202. Local body tissue (not shown) may surround the vessel wall 202. The local body tissue may comprise adventitia and connective tissues, nerves, fat, fluid, etc., in addition to the muscular vessel wall 202. A portion of the surrounding tissue may constitute the desired treatment region. For instance, one or more renal nerves (not shown) may extend along the outer wall of the body lumen 204.
The system 200 may include an elongate catheter shaft 208 having a proximal end (not shown) and a distal end region 211. The elongate shaft 208 may extend proximally from the distal end region 211 to the proximal end configured to remain outside of a patient's body. Although not shown, the proximal end of the elongate shaft 208 may include a hub attached thereto for connecting other treatment devices or providing a port for facilitating other treatments. It is contemplated that the stiffness of the elongate shaft 208 may be modified to form the modulation system 200 for use in various vessel diameters and various locations within the vascular tree.
In some instances, the elongate shaft 208 may have an elongate tubular structure and may include one or more lumens extending therethrough. For instance, in the illustrated embodiment, the elongate shaft 208 includes a lumen 209 having a guidewire wire 220 slidably disposed therein, however, this is not required. In some embodiments, the elongate shaft may include one or more auxiliary lumens. In some instances, the elongate shaft 208 may include a separate lumen(s) (not shown) for infusion of fluids or for other purposes such as the introduction of a medical device, and so forth. The fluid may facilitate cooling of the modulation system 200 during the ablation procedure, in addition to the cooling of body lumen 204. Further, the lumens may be configured in any way known in the art. For example, the lumen may extend along the entire length of the elongate shaft 208 such as in an over-the-wire catheter or may extend only along a distal portion of the elongate shaft 208 such as in a single operator exchange (SOE) catheter. These examples are not intended to be limiting, but rather examples of some possible configurations. While not explicitly shown, the modulation system 200 may further include temperature sensors/wire, an infusion lumen, radiopaque marker bands, fixed guidewire tip, a guidewire lumen, and/or other components to facilitate the use and advancement of the system 200 within the vasculature.
Further, the elongate shaft 208 may have a relatively long, thin, flexible tubular configuration. In some instances, the elongate shaft 208 may have a generally circular cross-section, however, other suitable configurations such as, but not limited to, rectangular, oval, irregular, or the like may also be contemplated. In addition, the elongate shaft 208 may have a cross-sectional configuration adapted to be received in a desired vessel, such as a renal artery. For instance, the elongate shaft 208 may be sized and configured to accommodate passage through the intravascular path, which leads from a percutaneous access site in, for example, the femoral, brachial, or radial artery, to a targeted treatment site, for example, within a renal artery.
Materials employed to manufacture the elongate shaft 208 may include any suitable biocompatible material. Examples may include metals, polymers, alloys, shape memory materials, etc. Other suitable materials known in the art may also be employed.
The system 200 may further include one or more ablation transducers 210 positioned adjacent the distal end region 211 of the elongate shaft 208. While FIG. 2 illustrates a single ablation transducer 210, it is contemplated that the modulation system 200 may include any number of ablation transducers desired, such as, but not limited to, one, two, three, or more. The ablation transducer 210 is configured to deliver acoustic energy (i.e., ultrasound waves) to the target region around the vessel wall 202. In some instances, the frequency of the ultrasound energy used for the procedure may be set so that the ablated area of tissue starts after it passes through the vessel wall 202 thereby minimizing potential heat damage of the vessel wall 202. While the ablation transducer 210 is described as an ultrasonic transducer, it is contemplated that other methods and devices for raising the temperature of the nerves may be used, such as, but not limited to: radiofrequency, microwave, other acoustic, optical, electrical current, direct contact heating, or other heating.
In some embodiments, the ablation transducer 210 may have a cylindrical shape, however, those skilled in the art will appreciate that any suitable shapes such as, but not limited to, square, rectangular, polygonal, circular, oblong, or the like may also be contemplated. In some instances, such as when a cylindrical transducer is provided, the ablation transducer 210 may extend around the entire circumference of the elongate shaft 208. In an alternative embodiment, however, the ablation transducer 210 may extend partially around the circumference of the elongate shaft 208. For instance, the ablation transducer 210 may include an array of one or more transducers (not shown) positioned about the circumference of the elongate shaft 208. In other embodiments, the ablation transducer 210 may comprise a focused or phased array of transducers. The array may be configured to be directed at a focus region such that multiple transducers are radiating energy at a common target region. It is further contemplated that the ablation transducer 210 may comprise a plurality of longitudinally spaced transducers. Those skilled in the art will appreciate that other suitable configurations of the ablation transducer 210 may also be contemplated without departing from the scope and spirit of the present disclosure.
The ablation transducer 210 may be formed from any suitable material such as, but not limited to, lead zirconate titanate (PZT). It is contemplated that other ceramic or piezoelectric materials may also be used. In some instances, the ablation transducer 210 may include a layer of gold, or other conductive layer, disposed on the acoustically functional areas of the transducer 210 surface for connecting electrical leads to the ablation transducer 210. It is contemplated that the sides/edges of the transducer crystal may be free of conductive material so as not to “short circuit” the transducer 210. In some instances, one or more tie layers may be used to bond the gold to the PZT. For example, a layer of chrome may be disposed between the PZT and the gold to improve adhesion. In other instances, the transducer 210 may include a layer of chrome over the PZT followed by a layer of nickel, and finally a layer of gold. These are just examples. It is contemplated that the layers may be deposited on the PZT using sputter coating, although other deposition techniques may be used as desired.
The ablation transducer 210 may have a radiating surface, and a perimeter surface extending around the outer edge of the ablation transducer 210. The acoustic energy from the radiating surface of the ablation transducer 210 may be transmitted in a spatial pressure distribution related to the shape of the ablation transducer 210. For instance, the cylindrical shape of the ablation transducer 210 may provide a circumferential ablation pattern. In such an instance, the ablation transducer 210 may include a backing layer to direct the acoustic energy in a single direction. In other embodiments, the ablation transducer 210 may be structured to radiate acoustic energy from two radiating surfaces.
In some embodiments, an electrical conductor, such as the element 102 (as shown in FIG. 1), may connect the ablation transducer 210 to a power and control unit (such as control unit 108 in FIG. 1). In some embodiments, the electrical conductor(s) may be disposed within a lumen of the elongate shaft 208. In other embodiments, the electrical conductor(s) may extend along an outside surface of the elongate shaft 208. The electrical conductor(s) may provide electricity to the ablation transducer 210, which may then be converted into acoustic energy. The acoustic energy may be directed from the ablation transducer 210 in a direction generally perpendicular to the radiating surfaces of the transducer 210. As discussed above, acoustic energy radiates from the ablation transducer 210 in a pattern related to the shape of the transducer 210 and lesions formed during ablation take shape similar to contours of the pressure distribution.
The system 200 can further include an expandable frame or basket 212 having a proximal end 213 and a distal end 215. The proximal end 213 of the expandable basket 212 may be affixed to the elongate shaft 208 proximal to the ablation transducer 210 and the distal end 215 may be affixed to elongate shaft 208 distal to the ablation transducer 210. However, it is contemplated that the expandable basket 212 may be positioned along any portion of the elongate shaft 208 desired. The proximal and distal ends 213, 215 of the basket 212 may be affixed to the elongate shaft 208 in any manner desired. For example, in some instances, a band or retaining element 218 may be used to secure the proximal and distal ends 213, 215. In other instances, the proximal and distal ends 213, 215 may be secured to the elongate shaft 208 with an adhesive or other suitable method. It is further contemplated that either or both of the proximal or distal ends 213, 215 may be secured to an element other than the elongate shaft 208 to facilitate expansion and/or contraction of the basket 212.
The expandable basket 212 may include one or more generally longitudinally extending struts 214a 214b , 214c , 214d , 214e , and 214f (collectively referred to hereinafter as struts 214). Although six struts 214 are shown in FIG. 2, it should be noted that any suitable number of struts 214 may be employed for desired purposes. Further, the expandable basket 212 may be configured to actuate between a first collapsed configuration and a second expanded configuration (shown in FIG. 2), which may include transition of the struts 214 from a generally straight configuration to a curved configuration, respectively. More particularly, the struts 214 in the collapsed configuration may extend and/or straighten to be generally parallel with or generally extend along the longitudinal length of the elongate shaft 208. In contrast, in the second expanded configuration, as shown in FIG. 2, the struts 214 may expand and/or curve like the ribs of an umbrella to surround the ablation transducer 210.
According to embodiments of the present disclosure, the expandable basket 212 may be adapted to align and position the ablation transducer 210 within the body lumen 204. In particular, the ultrasound transducer 210 may be positioned at the center of the expandable basket 212 in the expanded configuration. The centering of the ablation transducer 210 may result in better blood flow and accurate ablation geometry. To accomplish this, the expandable basket 212 may expand to meet the vessel wall 202, as discussed above. As shown in FIG. 2, the expandable basket 212 in the second expanded configuration may be arranged and positioned to surround the ablation transducer 210 circumferentially. In such an instance, the expandable basket 212 may facilitate circumferential ablation of the target region while allowing continued blood flow along the lumen 204. Therefore, the expandable basket 212 allows blood flow for cooling and for renal perfusion, unlike occlusive balloon approaches. In some other embodiments, although not shown, the expandable basket 212 may include one or more electrodes or transducers disposed along the struts 214 such as to contact the vessel wall 202, capable of creating one or more lesions during the ablation procedure.
The expandable basket 212 may be self-expandable, or may require external force to expand. A self-expandable basket 212 may be formed of any material or structure that is in a compressed state when force is applied and in an expanded state when force is released. Such material may include, for example, shape memory materials such as Nitinol or any other self-expandable material commonly known in the art. When employing such shape-memory materials, the expandable basket 212 may be heat set in the expanded state and then compressed to fit within a delivery sheath such as a guide sheath 222, for example. Upon reaching the target location within the body lumen 204, the guide sheath 222 can be retracted to deploy the expandable basket 212 in the expanded configuration. In another embodiment, a spring may be provided to effect expansion. Alternatively, external forces such as, but not limited to, pneumatic methods, compressed fluid, or the like may also be employed to expand the expandable basket 212.
In addition, the system 200 may include an actuation mechanism, for example, a pull wire, which may be employed to manipulate or actuate the expandable basket 212 between the collapsed and expanded configurations discussed above. In an embodiment, the pull wire may be attached to the proximal end 213 or distal end 215 of the basket 212 such that a push-pull mechanism of the pull wire may manipulate the expandable basket 212, thus actuating the expandable basket 212 between the collapsed and expanded configurations. To this end, the pull wire may be pulled proximally to pull the expandable basket 212, switching the expandable basket 212 to the expanded configurations. In addition, the pull wire may be pushed distally to switch the expandable basket 212 in the collapsed configuration. Alternatively, the pull wire may be pushed distally, which may allow the expandable basket 212 to move to the expanded state. In such instance, the pull wire may be pulled proximally, which may allow the expandable basket 212 to move to the collapsed state.
The system 200 can further include one or more temperature sensors 216a and 216b (collectively referred hereinafter as sensors 216) coupled to the expandable basket 212. Although two temperature sensors 216 are shown, it should be noted that any suitable number of temperature sensors 216 may employed for desired purposes. In addition, other suitable sensors such as impedance sensors may also be employed. As shown, the temperature sensors 216 may be placed on the struts 214 such as to contact the vessel wall 202 in the expanded configuration. The contact between the sensors 216 and the wall 202 may allow measuring of temperature of the vessel wall 202 during the ablation procedure. According to an example, the temperature sensors 216 may include one or more thermocouples, which may be employed to monitor wall 202 temperatures.
As discussed previously, the system 200 may include one or more guide sheaths 222 having a proximal end (not shown), a distal end 221, and a lumen extending therebetween. It should be noted that guide sheath 222 may include any suitable number of lumens as required or desired. The elongate shaft 208 may be slidably disposed within the lumen of the guide sheath 222. In some instances, the guide sheath 222 may also be used as an infusion sheath. For example, the distal end 221 of the guide sheath 222 may be open to allow an infusion fluid to exit. Saline or other suitable infusion fluid (not shown) may be flushed through the lumen 223. In an alternate embodiment, the infusion fluid may exit through the distal end region 211 of the elongate shaft 208, thereby displacing blood from and around the transducer 210. As the infusion fluid flows past the ablation transducer 210, the infusion fluid may provide convective cooling to the ablation transducer 210. It is further contemplated that by displacing and/or cooling the blood surrounding the transducer 210, blood damage, fouling of the transducer 210, and/or overheating of the transducer 210 may be reduced or eliminated. In some instances, this may allow the modulation system 200 to be operated at a higher power level, thus providing a shorter treatment and/or more effective modulation of the target tissue. In some embodiments, the modulation system may be structured to direct some or all of the infusion fluid along the inside of the vessel wall 202. While blood flowing through the vessel lumen 204 removed some heat from the wall tissue, the addition of a “cooling” flush via infusion fluid directed towards the vessel wall 202 may allow the application of more power for a shorter time period. It is contemplated that the infusion fluid may be introduced into the modulation system 200 before, during, or after ablation. Flow of the infusion fluid may begin before energy is supplied to the ablation transducer 210 and continue for the duration of the modulation procedure. In some instances, a separate infusion sheath (not explicitly shown) may be provided, as will be discussed in more detail below.
The infusion fluid may be saline or any other suitable infusion fluid. It is contemplated that the infusion fluid may be provided at a variety of different temperatures depending on the desired treatment. In some instances, the infusion fluid may be provided at room temperature, below room temperature, above room temperature, or at normal body temperature as desired. In addition, the salinity of the infusion fluid can be chosen to obtain desired electrical conductivity, such as to improve the discrimination capability of impedance monitoring. In some instances, such as when an imaging transducer is provided (not explicitly shown), a small amount of an imaging contrast material may be added to the infusion fluid to facilitate imaging of the vessel. Suitable examples of such imaging contrast material may include, but are not limited to fluorine, iodine, barium, or the like.
The modulation system 200 may be advanced through the vasculature in any manner known in the art. For example, system 200 may include a guidewire lumen to allow the system 200 to be advanced over a previously located guidewire, such as guidewire 220. In some embodiments, the modulation system 200 may be advanced, or partially advanced, within a delivery catheter such as the guide catheter 222. Once the transducer 210 of the modulation system 200 has been placed adjacent to the desired treatment area, positioning mechanisms, such as basket 212, may be deployed, if so provided. The transducer 210 may be connected to a power and control unit (such as control unit 108 in FIG. 1) by an electrical conductor. The transducer 210 may be connected to one or more control units, which may provide and/or monitor the system 200 with one or more parameters such as, but not limited to, frequency for performing the desired ablation procedure as well as imaging. In some embodiments, the electrical conductor may be disposed within a lumen of the elongate shaft 208. In other embodiments, the electrical conductor may be extended along an outside surface of the elongate shaft 208.
Once the modulation system 200 has been advanced to the treatment region, the expandable basket 212 may be moved to the expanded configuration to position and align the transducer 210 within the lumen 204. Further, an infusion fluid may be provided through a lumen of an infusion sheath. It is contemplated that energy may be supplied to the ablation transducer 210 before, during, and/or after the expandable basket 212 is shifted to the expanded configuration. The electrical conductor may provide electricity to the ablation transducer 210, and that energy may then be converted into acoustic energy. The acoustic energy may be directed from the ablation transducer 210 in a direction generally perpendicular to the radiating surfaces of the ablation transducer 210, generally in a pattern related to the shape of the ablation transducer 210. Although FIG. 1 illustrates a single electrical conductor 102, it is contemplated that the modulation system 200 may include any number of electrical conductors desired, such as, but not limited to, two, three, or more. For example, if multiple ablation transducers are provided, multiple electrical conductors may be required. The amount of energy delivered to the transducer 210 may be determined by the desired treatment as well as the feedback provided by monitoring devices, such as sensors 216.
In some instances, such as when a transducer does not extend around the entire circumference of the elongate shaft 208, the elongate shaft 208 may be rotated and additional ablation can be performed at multiple locations around the circumference of the lumen 204. In some instances, a slow automated “rotisserie” rotation can be used to work around the circumference of the lumen 204, or a faster spinning can be used to simultaneously ablate around the entire circumference. The spinning can be accomplished with a distal micro-motor or by spinning a drive shaft from the proximal end. In other instances, the elongate shaft 208 may be indexed incrementally between desired orientations. In some embodiments, temperature sensors 216 can provide information that can be used to selectively turn on and off the ablation transducer 210 to warm any cool spots or accommodate for veins, or other tissue variations. The number of times the elongate shaft 208 is rotated at a given longitudinal location may be determined by the number, size and/or shape of the transducer 210 on the elongate shaft 208. Once a particular location has been ablated, it may be desirable to perform further ablation procedures at different longitudinal locations. Once the elongate shaft 208 has been longitudinally repositioned, energy may once again be delivered to the transducer 210 to perform ablation and/or imaging as desired. If necessary, the elongate shaft 208 may be rotated to perform ablation around the circumference of the lumen 204 at each longitudinal location. This process may be repeated at any number of longitudinal locations desired. It is contemplated that in some embodiments, the system 200 may include multiple transducers 210 located at various positions along the length of the elongate shaft 208 such that a larger region may be treated without longitudinal displacement of the elongate shaft 208.
Referring now to FIGS. 3A and 3B, side views of a distal portion of another illustrative intravascular nerve modulation system 300 is depicted. The system 300 may include an elongate shaft 308 having a proximal end region (not shown), a distal end region 311, and a lumen 309 extending therebetween. The elongate shaft 308 may have similar form and function to the elongate shaft 208 discussed above.
The elongate shaft 308 may extend proximally from the distal end region 311 to the proximal end configured to remain outside of a patient's body. Although not shown, the proximal end of the elongate shaft 308 may include a hub attached thereto for connecting other treatment devices or providing a port for facilitating other treatments. It is contemplated that the stiffness of the elongate shaft 308 may be modified to form the modulation system 300 for use in various vessel diameters and various locations within the vascular tree.
The elongate shaft 308 may include one or more lumens extending therethrough. For instance, in the illustrated embodiment, the elongate shaft 308 may include a lumen 309 having a pull wire 320 slidably disposed therein. In some instances, the elongate shaft 308 may include a separate guidewire lumen and/or separate lumen(s) (not shown) for infusion of fluids or for other purposes such as introduction of a medical device, and so forth. The fluid may facilitate cooling of the modulation system 300 during the ablation procedure. Further, the lumen 309 may be configured in any way known in the art. For example, the lumen 309 may extend along the entire length of the elongate shaft 308 such as in an over-the-wire catheter or may extend only along a distal portion of the elongate shaft 308 such as in a single operator exchange (SOE) catheter. These examples are not intended to be limiting, but rather examples of some possible configurations.
Further, the elongate shaft 308 has a relatively long, thin, flexible tubular configuration. In some instances, the elongate shaft 308 may have a generally circular cross-section, however, other suitable configurations such as, but not limited to, rectangular, oval, irregular, or the like may also be contemplated. In addition, the elongate shaft 308 may have a cross-sectional configuration adapted to be received in a desired vessel, such as a renal artery. For instance, the elongate shaft 308 may be sized and configured to accommodate passage through the intravascular path, which leads from a percutaneous access site in, for example, the femoral, brachial, or radial artery, to a targeted treatment site, for example, within a renal artery.
Materials employed to manufacture the elongate shaft 308 may include any suitable biocompatible material. Examples may include metals, polymers, alloys, shape memory alloys, etc. Other suitable materials known in the art may also be employed.
The system 300 may further include one or more ablation transducers 310 positioned adjacent the distal end region 311 of the elongate shaft 308. While FIGS. 3A and 3B illustrate a single ablation transducer 310, it is contemplated that the modulation system 300 may include any number of ablation transducers desired, such as, but not limited to, one, two, three, or more. The ablation transducer 310 is configured to deliver acoustic energy (i.e., ultrasound waves) to the target region around a vessel wall. At the targeted tissue, the acoustic energy is converted to heat, resulting in protein denaturation and coagulative necrosis of the tissue and/or nerves at the target region. In some instances, the frequency of the ultrasound energy used for the procedure may be set so that the ablated area of tissue starts after it passes through the vessel wall thereby minimizing potential heat damage of the vessel wall. The ablation transducer 310 may be similar in form and function to ablation transducer 210 discussed above.
While the ablation transducer 310 is described as an ultrasonic transducer, it is contemplated that other methods and devices for raising the temperature of the nerves may be used, such as, but not limited to: radiofrequency, microwave, other acoustic, optical, electrical current, direct contact heating, or other heating.
Further, the ablation transducer 310 may have a cylindrical shape, however, those skilled in the art will appreciate that any suitable shapes such as, but not limited to, square, rectangular, polygonal, circular, oblong, or the like may also be contemplated. In some instances, such as when a cylindrical transducer is provided, the ablation transducer 310 may extend around the entire circumference of the elongate tubular member 308. In an alternative embodiment, however, the ablation transducer 310 may extend partially around the circumference of the elongate tubular member 208. For instance, the ablation transducer 310 may include an array of one or more transducers (not shown) positioned about the circumference of the elongate tubular member 308. In other embodiments, the ablation transducer 310 may comprise a focused or phased array of transducers. The array may be configured to be directed at a focus region such that multiple transducers are radiating energy at a common target region. It is further contemplated that the ablation transducer 310 may comprise a plurality of longitudinally spaced transducers. Those skilled in the art will appreciate that other suitable configurations of the ablation transducer 310 may also be contemplated without departing from the scope and spirit of the present disclosure.
The ablation transducer 310 may be formed from any suitable material such as, but not limited to, lead zirconate titanate (PZT). It is contemplated that other ceramic or piezoelectric materials may also be used. In some instances, the ablation transducer 310 may include a layer of gold, or other conductive layer, disposed on the acoustically functional areas of the transducer 310 surface for connecting electrical leads to the ablation transducer 310. It is contemplated that the sides/edges of the transducer crystal may be free of conductive material so as not to “short circuit” the transducer 310. In some instances, one or more tie layers may be used to bond the gold to the PZT. For example, a layer of chrome may be disposed between the PZT and the gold to improve adhesion. In other instances, the transducer 310 may include a layer of chrome over the PZT followed by a layer of nickel, and finally a layer of gold. These are just examples. It is contemplated that the layers may be deposited on the PZT using sputter coating, although other deposition techniques may be used as desired.
Although not shown, the ablation transducer 310 may have a radiating surface, and a perimeter surface extending around the outer edge of the ablation transducer 310. The acoustic energy from the radiating surface of the ablation transducer 310 may be transmitted in a spatial pressure distribution related to the shape of the ablation transducer 310. For instance, the cylindrical shape of the ablation transducer 310 may provide a circumferential ablation pattern. In such an instance, the ablation transducer 310 may include a backing layer to direct the acoustic energy in a single direction. In other embodiments, the ablation transducer 310 may be structured to radiate acoustic energy from two radiating surfaces.
In some embodiments, an electrical conductor such as the element 102 (as shown in FIG. 1) may connect the ablation transducer 310 to a control unit (such as control unit 108 in FIG. 1). In some embodiments, the electrical conductor(s) may be disposed within a lumen of the elongated shaft 308. In other embodiments, the electrical conductor(s) may extend along an outside surface of the elongated shaft 308. The electrical conductor(s) 102 may provide electricity to the ablation transducer 310, which may then be converted into acoustic energy. The acoustic energy may be directed from the ablation transducer 310 in a direction generally perpendicular to the radiating surfaces of the transducer 310. As discussed above, acoustic energy radiates from the ablation transducer 310 in a pattern related to the shape of the transducer 310 and lesions formed during ablation take shape similar to contours of the pressure distribution.
The system 300 can further include an expandable basket 312 having a proximal end 313 and a distal end 315. The proximal end 313 may be affixed adjacent the distal end region 311 of the elongate shaft 308 and the distal end 315 may be affixed to an end cap 318 positioned distal of a distal end of the ablation transducer 310. The end cap 318 may have a rounded distal portion 302, which may avoid any injury to the body tissue while the system 300 is introduced in a body lumen.
The expandable basket 312 may include two (or more) generally longitudinally extending struts 314a and 314b (collectively referred hereinafter as struts 314). Although two struts 314 are visible in FIGS. 3A and 3B, it should be noted that any suitable number of struts 314 may be employed for desired purposes. Further, the expandable basket 312 is configured to actuate between a first collapsed configuration and a second expanded configuration, which may include transition of the struts 314 from a generally straight or slightly bowed configuration (as shown in FIG. 3A) to a curved configuration (as shown in FIG. 3B), respectively. More particularly, the struts 314 in the collapsed configuration may extend and/or straighten to be generally parallel with or generally extend along the longitudinal length of the elongate shaft 308, as shown in FIG. 3A. In contrast, in the second expanded configuration, as shown in FIG. 3B, the struts 314 may expand and/or curve like the ribs of an umbrella to surround the ablation transducer 310. Further, the expandable basket 312 may have similar form and function to the expandable basket 212 discussed above.
According to embodiments of the present disclosure, the expandable basket 312 can be adapted to align and position the ablation transducer 310 within a body lumen. To accomplish this, the expandable basket 312 may expand to meet the vessel wall. As shown in FIG. 3B, the expandable basket 312 may expand to the second expanded configuration, which may be arranged and positioned to contact the vessel wall and may position the ablation transducer 310 approximately in the center of the lumen. In such an instance, the expandable basket 312 may facilitate circumferential ablation of the target region while allowing continued blood flow along the lumen. In some other embodiments, although not shown, the expandable basket 312 may include one or more electrodes or transducers disposed along the struts 314 capable of creating lesion(s) while being in contact with the vessel wall.
In the present embodiment, the expandable basket 312 may include an actuation mechanism for moving the basket 312 between the collapsed and expanded positions. For example, the pull wire 320 may be employed to manipulate or actuate the expandable basket 312 between the collapsed and expanded configurations. In an embodiment, the pull wire 320 may be distally attached to the end cap 318 such that a push-pull mechanism of the pull wire 320 may manipulate the expandable basket 312, thus actuating the expandable basket 312 between the collapsed and expanded configurations, respectively. To this end, the pull wire 320, while being affixed to the end cap 318, may be pulled proximally to pull the expandable basket 312, switching the expandable basket 312 to the expanded configurations, as shown in FIG. 3B. In other embodiments, the pull wire 320 may be affixed to the distal end 315 of the basket 312. In this instance, distal actuation of the pull wire 320 may expand the basket 312.
While not explicitly shown, the system 300 may include one or more temperature sensors coupled to the expandable basket 312. In addition, other suitable sensors such as impedance sensors may also be employed. Contact between the sensors and the lumen wall may allow measuring of temperature of the lumen wall during the ablation procedure. According to an example, the temperature sensors may include one or more thermocouples, which may be employed to monitor wall temperatures.
While not explicitly shown, the system 300 can also include one or more guide sheaths having a proximal end, a distal end, and a lumen extending therebetween. The guide sheath may have similar form and function to the guide sheath 222 as discussed above. The elongate shaft 308 may be slidably disposed within the lumen of the guide sheath. In some instances, the guide sheath may also be used as an infusion sheath. For example, the distal end of the guide sheath may be open to allow an infusion fluid to exit. Saline or other suitable infusion fluid (not shown) may be flushed through the lumen.
In an alternate embodiment, an infusion fluid may exit through the distal end region 311 of the elongate shaft 308, thereby displacing blood from and around the transducer 310. As the infusion fluid flows past the ablation transducer 310, the infusion fluid may provide convective cooling to the ablation transducer 310. It is further contemplated that by displacing and/or cooling the blood surrounding the transducer 310, blood damage, fouling of the transducer 310, and/or overheating of the transducer 310 may be reduced or eliminated. In some instances, this may allow the modulation system 300 to be operated at a higher power level, thus providing a shorter treatment and/or more effective modulation of the target tissue. In some embodiments, the modulation system 300 may be structured to direct some or all of the infusion fluid along the inside of the vessel wall. While blood flowing through the vessel lumen removed some heat from the wall tissue, the addition of a “cooling” flush via infusion fluid directed towards the vessel wall may allow the application of more power for a shorter time period. It is contemplated that the infusion fluid may be introduced into the modulation system 300 before, during, or after ablation. Flow of the infusion fluid may begin before energy is supplied to the ablation transducer 310 and continue for the duration of the modulation procedure. In some instances, a separate infusion sheath (not explicitly shown) may be provided, as will be discussed in more detail below.
Although not shown, the modulation system 300 may further include radiopaque marker bands, fixed guidewire tip, a guidewire lumen, and/or other components to facilitate the use and advancement of the system 300 within the vasculature. In addition, the system 300 can further include one or more sensors (e.g. temperature, impedance, etc.) for monitoring the ablation procedure. It should be noted that any suitable number of temperature sensors may employed for desired purposes. In addition, other suitable sensors such as impedance sensors may also be employed.
Turning now to FIG. 4, a side view of a distal portion of another illustrative intravascular nerve modulation system 400 is depicted. The system 400 may include an elongate shaft 408 having a proximal end (not shown), a distal end region 411, and a lumen 409 extending therebetween. The elongate shaft 408 may extend proximally from the distal end region 411 to the proximal end configured to remain outside of a patient's body. Although not shown, the proximal end of the elongate shaft 408 may include a hub attached thereto for connecting other treatment devices or providing a port for facilitating other treatments. It is contemplated that the stiffness of the elongate shaft 408 may be modified to form the modulation system 400 for use in various vessel diameters and various locations within the vascular tree. The elongate shaft 408 may be similar in form and function to elongate shafts 208, 308 discussed above.
The elongate shaft 408 may include one or more lumens extending therethrough. For instance, in the illustrated embodiment, the elongate shaft 408 may include a lumen 409 for receiving a guidewire therethrough. In some instances, the elongate shaft 408 may include a separate guidewire lumen and/or separate lumen(s) (not shown) for infusion of fluids or for other purposes such as introduction of a medical device, and so forth. The fluid may facilitate cooling of the modulation system 400 during the ablation procedure. Further, the lumen 409 may be configured in any way known in the art. For example, the lumen 409 may extend along the entire length of the elongate shaft 408 such as in an over-the-wire catheter or may extend only along a distal portion of the elongate shaft 408 such as in a single operator exchange (SOE) catheter. These examples are not intended to be limiting, but rather examples of some possible configurations. Further, the elongate shaft 408 has a relatively long, thin, flexible tubular configuration. In some instances, the elongate shaft 408 may have a generally circular cross-section, however, other suitable configurations such as, but not limited to, rectangular, oval, irregular, or the like may also be contemplated. In addition, the elongate shaft 408 may have a cross-sectional configuration adapted to be received in a desired vessel, such as a renal artery. For instance, the elongate shaft 408 may be sized and configured to accommodate passage through the intravascular path, which leads from a percutaneous access site in, for example, the femoral, brachial, or radial artery, to a targeted treatment site, for example, within a renal artery.
Materials employed to manufacture the elongate shaft 408 may include any suitable biocompatible material. Examples may include metals, polymers, alloys, shape memory alloys, etc. Other suitable materials known in the art may also be employed.
The system 400 can further include one or more ablation transducers 410 positioned adjacent the distal end region 411 of the elongate shaft 408. While FIG. 4 illustrates single ablation transducer 410, it is contemplated that the modulation system 400 may include any number of ablation transducers desired, such as, but not limited to, one, two, three, or more. The ablation transducer 410 is configured to deliver acoustic energy (i.e., ultrasound waves) to the target region around the vessel wall. At the targeted tissue, the acoustic energy is converted to heat resulting in protein denaturation and coagulative necrosis of the tissue and/or nerves at the target region. In some instances, the frequency of the ultrasound energy used for the procedure may be set so that the ablated area of tissue starts after it passes through the vessel wall thereby minimizing potential heat damage of the vessel wall. The ablation transducer 410 may be similar in form and function to ablation transducers 210, 310 discussed above.
While the ablation transducer 410 is described as an ultrasonic transducer, it is contemplated that other methods and devices for raising the temperature of the nerves may be used, such as, but not limited to: radiofrequency, microwave, other acoustic, optical, electrical current, direct contact heating, or other heating.
Further, the ablation transducer 410 may have a cylindrical shape, however, those skilled in the art will appreciate that any suitable shapes such as, but not limited to, square, rectangular, polygonal, circular, oblong, or the like may also be contemplated. In some instances, such as when a cylindrical transducer is provided, the ablation transducer 410 may extend around the entire circumference of the elongate tubular member 408. In an alternative embodiment, however, the ablation transducer 410 may extend partially around the circumference of the elongate tubular member 408. For instance, the ablation transducer 410 may include an array of one or more transducers (not shown) positioned about the circumference of the elongate tubular member 408. In other embodiments, the ablation transducer 410 may comprise a focused or phased array of transducers. The array may be configured to be directed at a focus region such that multiple transducers are radiating energy at a common target region. It is further contemplated that the ablation transducer 410 may comprise a plurality of longitudinally spaced transducers. Those skilled in the art will appreciate that other suitable configurations of the ablation transducer 410 may also be contemplated without departing from the scope and spirit of the present disclosure.
The ablation transducer 410 may be formed from any suitable material such as, but not limited to, lead zirconate titanate (PZT). It is contemplated that other ceramic or piezoelectric materials may also be used. In some instances, the ablation transducer 410 may include a layer of gold, or other conductive layer, disposed on the acoustically functional areas of the transducer 410 surface for connecting electrical leads to the ablation transducer 410. It is contemplated that the sides/edges of the transducer crystal may be free of conductive material so as not to “short circuit” the transducer 410. In some instances, one or more tie layers may be used to bond the gold to the PZT. For example, a layer of chrome may be disposed between the PZT and the gold to improve adhesion. In other instances, the transducer 210 may include a layer of chrome over the PZT followed by a layer of nickel, and finally a layer of gold. These are just examples. It is contemplated that the layers may be deposited on the PZT using sputter coating, although other deposition techniques may be used as desired.
Although not shown, the ablation transducer 410 may have a radiating surface, and a perimeter surface extending around the outer edge of the ablation transducer 410. The acoustic energy from the radiating surface of the ablation transducer 410 may be transmitted in a spatial pressure distribution related to the shape of the ablation transducer 410. For instance, the cylindrical shape of the ablation transducer 410 may provide a circumferential ablation pattern. In such an instance, the ablation transducer 410 may include a backing layer to direct the acoustic energy in a single direction. In other embodiments, the ablation transducer 410 may be structured to radiate acoustic energy from two radiating surfaces.
In some embodiments, an electrical conductor such as the element 102 (as shown in FIG. 1) may connect the ablation transducer 410 to a control unit (such as control unit 108 in FIG. 1). In some embodiments, the electrical conductor(s) may be disposed within a lumen of the elongated shaft 408. In other embodiments, the electrical conductor(s) may extend along an outside surface of the elongated shaft 408. The electrical conductor(s) may provide electricity to the ablation transducer 410, which may then be converted into acoustic energy. The acoustic energy may be directed from the ablation transducer 410 in a direction generally perpendicular to the radiating surfaces of the transducer 410. As discussed above, acoustic energy radiates from the ablation transducer 410 in a pattern related to the shape of the transducer 410 and lesions formed during ablation take shape similar to contours of the pressure distribution.
The system 400 can further include an expandable basket 412 having a proximal end 413 and a distal end 415. The proximal end 413 of the expandable basket 412 may be affixed adjacent the distal end region 411 of the elongate shaft 408 and the distal end 415 may be affixed to an end cap 418 positioned distal of a distal end of the ablation transducer 410. The end cap 418 may have a rounded distal portion 402, which may avoid any injury to the body tissue while the system 400 is introduced in a body lumen.
The expandable basket 412 may include two (or more) generally longitudinally extending struts 414a and 414b (collectively referred hereinafter as struts 414). Although two struts 414 are visible in FIG. 4, it should be noted that any suitable number of struts 414 may be employed for desired purposes. Further, the expandable basket 412 is configured to actuate between a first collapsed configuration and a second expanded configuration, which may include transition of the struts 414 from a generally straight or slightly bowed configuration to a curved configuration (shown in FIG. 4), respectively. More particularly, the struts 414 in the collapsed configuration may extend and/or straighten generally parallel (not explicitly shown) along the longitudinal length of the elongate shaft 408 similar to struts 314 shown in FIG. 3A. In contrast, in the second expanded configuration (shown in FIG. 4), the struts 414 may expand and/or curve like the ribs of an umbrella to surround the ablation transducer 410. Further, the expandable basket 412 may have similar form and function to the expandable baskets 212, 312 discussed above.
According to embodiments of the present disclosure, the expandable basket 412 can be adapted to align and position the ablation transducer 410 within a body lumen. To accomplish this, the expandable basket 412 may expand to meet the vessel wall. As shown in FIG. 4, the expandable basket 412 may expand to the second expanded configuration, which may be arranged and positioned to contact the vessel wall and may position the ablation transducer 410 approximately in the center of the lumen. In such an instance, the expandable basket 412 may facilitate circumferential ablation of the target region while allowing continued blood flow along the lumen. In some other embodiments, although not shown, the expandable basket 412 may include one or more electrodes or transducers disposed along the struts 414 capable of creating lesion(s) while being in contact with the vessel wall, or to monitor temperature or other characteristics.
In present embodiment, the expandable basket 412 may be self-expandable and may not require external force to expand. Self-expandable expandable basket 412 may be formed of any material or structure that is in a compressed state when force is applied and in an expanded state when force is released. Such material may include, for example, shape memory alloys such as Nitinol or any other self-expandable material commonly known in the art. When employing such shape-memory materials, the expandable basket 412 may be heat set in the expanded state and then compressed to fit within a delivery sheath such as a guide sheath 422, for example. Upon reaching the target location within the body lumen, the infusion sheath 422 can be retracted proximally to deploy the expandable basket 412 in the expanded configuration. In some embodiment, a spring may be provided to effect expansion. Alternatively, external forces such as, but not limited to, pneumatic methods, compressed fluid, or the like may also be employed to expand the expandable basket 412.
Although not shown, the system 400 may include one or more temperature or other suitable sensors coupled to the expandable basket 412. Other suitable sensors may include impedance sensors or other sensors for monitoring the ablation procedure. According to an example, the sensors may be placed on the struts 414 such as to contact the vessel wall in the expanded configuration. The contact between the sensors and the wall may allow for measuring of temperature or other expected physiological parameter of the vessel wall during the ablation procedure. For example, the temperature sensor may include one or more thermocouple, which may be employed to monitor wall temperatures.
In some embodiments, ultrasound imaging may be used to monitor the ablation procedure. It is contemplated that ultrasound imaging may be used to monitor changes deeper in the tissue and adjust the therapy parameter as needed during the ablation procedure. In some instances, this may allow for the identification of nearby vessels that could be removing heat from the targeted tissue around it, thereby allowing increased power delivery, and thus increased heating, to be concentrated in the targeted location.
As discussed above, the system 400 may include a guide sheath 422 having a proximal end (not shown), a distal end 421, and a lumen 423 extending therebetween. The guide sheath may have similar form and function to the guide sheath 222 as discussed above. The elongate shaft 408 may be slidably disposed within the lumen 423 of the guide sheath 422. In some instances, the guide sheath 422 may also be used as an infusion sheath. For example, the distal end 421 of the guide sheath 422 may be open to allow an infusion fluid to exit. Saline or other suitable infusion fluid (not shown) may be flushed through the lumen.
In an alternate embodiment, an infusion fluid may exit through the distal end region 411 of the elongate shaft 408, thereby displacing blood from and around the transducer 410. As the infusion fluid flows past the ablation transducer 410, the infusion fluid may provide convective cooling to the ablation transducer 410. It is further contemplated that by displacing and/or cooling the blood surrounding the transducer 410, blood damage, fouling of the transducer 410, and/or overheating of the transducer 410 may be reduced or eliminated. In some instances, this may allow the modulation system 400 to be operated at a higher power level, thus providing a shorter treatment and/or more effective modulation of the target tissue. In some embodiments, the modulation system 400 may be structured to direct some or all of the infusion fluid along the inside of the vessel wall. While blood flowing through the vessel lumen removed some heat from the wall tissue, the addition of a “cooling” flush via infusion fluid directed towards the vessel wall may allow the application of more power for a shorter time period. It is contemplated that the infusion fluid may be introduced into the modulation system 400 before, during, or after ablation. Flow of the infusion fluid may begin before energy is supplied to the ablation transducer 410 and continue for the duration of the modulation procedure. In some instances, a separate infusion sheath (not explicitly shown) may be provided, as will be discussed in more detail below.
While not explicitly shown, the modulation system 400 may further include radiopaque marker bands, guidewire, a guidewire lumen, and/or other components to facilitate the use and advancement of the system 400 within the vasculature.
FIG. 5 illustrates a side view of a distal portion of another example of an intravascular nerve modulation system 500. The system 500 is disposed within a body lumen 504 having a vessel wall 502 surrounded by local body tissue (not shown). The local body tissue may comprise adventitia and connective tissues, nerves, fat, fluid, etc., in addition to the muscular vessel wall 502. A portion of the surrounding tissue may constitute the desired treatment region. For instance, one or more renal nerves (not shown) may extend substantially longitudinally along the outer wall of the body lumen 504.
The system 500 may include an elongate shaft 508 having a distal end region 511. The elongate shaft 508 may extend proximally from the distal end region 511 to a proximal end configured to remain outside of a patient's body. The proximal end of the elongate shaft 508 may include a hub attached thereto for connecting other treatment devices or providing a port for facilitating other treatments. It is contemplated that the stiffness of the elongate shaft 508 may be modified to form a modulation system 500 for use in various vessel diameters and various locations within the vascular tree. The elongate shaft 508 may further include one or more lumens extending therethrough. For example, the elongate shaft 508 may include a guidewire lumen and/or one or more auxiliary lumens. In some instances, the elongate shaft 508 may include an infusion lumen, as will be discussed in more detail below. The lumens may be configured in any way known in the art. For example, the guidewire lumen may extend the entire length of the elongate shaft 508 such as in an over-the-wire catheter or may extend only along a distal portion of the elongate shaft 508 such as in a single operator exchange (SOE) catheter. These examples are not intended to be limiting, but rather examples of some possible configurations. While not explicitly shown, the modulation system 500 may further include temperature sensors/wire, an infusion lumen, radiopaque marker bands, fixed guidewire tip, a guidewire lumen, external sheath, centering basket, and/or other components to facilitate the use and advancement of the system 500 within the vasculature.
In some embodiments, the elongated catheter shaft 508 may have a relatively long, thin, flexible tubular configuration. In some instances, the elongated shaft 508 may have a generally circular cross-section, however, other suitable configurations such as, but not limited to, rectangular, oval, irregular, or the like may also be contemplated. In addition, the elongated shaft 508 may have a cross-sectional configuration adapted to be received in a desired vessel, such as a renal artery. For instance, the elongated shaft 508 may be sized and configured to accommodate passage through the intravascular path, which leads from a percutaneous access site in, for example, the femoral, brachial, or radial artery, to a targeted treatment site, for example, within a renal artery. Materials employed to manufacture the elongate shaft 508 may include any suitable biocompatible material. Examples may include metals, polymers, alloys, shape memory alloys, etc. Other suitable materials known in the art may also be employed.
The elongated shaft 508 may include a first tubular member 522 and a second tubular member 524. The first tubular member 522 may have a proximal end (not shown), a distal end 521 and a lumen 528 extending between the proximal end and the distal end. In some embodiments, the lumen 528 may be an infusion lumen and may be in fluid communication with an infusion fluid source configured to remain outside of a patient's body. The second tubular member 524 may have a proximal end (not shown), a distal end 530, and a lumen 509 extending therebetween. In some embodiments, the lumen 509 of the second tubular member may be a guidewire lumen for receiving a guidewire 520 therein. The distal end region 532 of the second tubular member 524 extends distally beyond the distal end 521 of the first tubular member 522. In some embodiments, the second tubular member 524 may be disposed within or partially within the lumen 528 of first tubular member 522. In some instances, the second tubular member 524 may be coaxially disposed within the first tubular member 522. In other instances, the longitudinal axis of the second tubular member 524 may be offset from the first tubular member 522. In some instances, the first tubular member 522 and the second tubular member 524 may be advanced through the vasculature together.
In addition, the system 500 may include one or more ablation transducers 510 positioned adjacent to the distal end region 532 of the second tubular member 524. While the ablation transducer 510 is shown and described as being positioned on the second tubular member 524, it is contemplated that in some instances, ablation transducers may be provided on the first tubular member 522. While FIG. 5 illustrates one ablation transducer 510, it is contemplated that the modulation system 500 may include any number of ablation transducers desired, such as, but not limited to, one, two, three, or more.
The ablation transducer 510 is configured to deliver acoustic energy (i.e., ultrasound waves) to the target region around the vessel wall 502. At the targeted tissue, the acoustic energy is converted to heat resulting in protein denaturation and coagulative necrosis of the tissue and/or nerves at the target region. In some instances, the frequency of the ultrasound energy used for the procedure may be set so that the ablated area of tissue starts after it passes through the vessel wall 502 thereby minimizing potential heat damage of the vessel wall 502.
While the ablation transducer 510 is described as an ultrasonic transducer, it is contemplated that other methods and devices for raising the temperature of the nerves may be used, such as, but not limited to: radiofrequency, microwave, other acoustic, optical, electrical current, direct contact heating, or other heating.
Further, the ablation transducer 510 may have a cylindrical shape, however, those skilled in the art will appreciate that any suitable shapes such as, but not limited to, square, rectangular, polygonal, circular, oblong, or the like may also be contemplated. In some instances, such as when a cylindrical transducer is provided, the ablation transducer 510 may extend around the entire circumference of the elongate shaft 508. In an alternative embodiment, however, the ablation transducer 510 may extend partially around the circumference of the elongate shaft 508. For instance, the ablation transducer 510 may include an array of one or more transducers (not shown) positioned about the circumference of the elongate shaft 508. In other embodiments, the ablation transducer 510 may comprise a focused or phased array of transducers. The array may be configured to be directed at a focus region such that multiple transducers are radiating energy at a common target region. It is further contemplated that the ablation transducer 510 may comprise a plurality of longitudinally spaced transducers. Those skilled in the art will appreciate that other suitable configurations of the ablation transducer 510 may also be contemplated without departing from the scope and spirit of the present disclosure.
The ablation transducer 510 may be formed from any suitable material such as, but not limited to, lead zirconate titanate (PZT). It is contemplated that other ceramic or piezoelectric materials may also be used. In some instances, the ablation transducer 510 may include a layer of gold, or other conductive layer, disposed on the acoustically functional areas of the transducer 510 surface for connecting electrical leads to the ablation transducer 510. It is contemplated that the sides/edges of the transducer crystal may be free of conductive material so as not to “short circuit” the transducer 510. In some instances, one or more tie layers may be used to bond the gold to the PZT. For example, a layer of chrome may be disposed between the PZT and the gold to improve adhesion. In other instances, the transducer 510 may include a layer of chrome over the PZT followed by a layer of nickel, and finally a layer of gold. These are just examples. It is contemplated that the layers may be deposited on the PZT using sputter coating, although other deposition techniques may be used as desired.
Although not shown, the ablation transducer 510 may have a radiating surface, and a perimeter surface extending around the outer edge of the ablation transducer 510. The acoustic energy from the radiating surface of the ablation transducer 510 may be transmitted in a spatial pressure distribution related to the shape of the ablation transducer 510. For instance, the cylindrical shape of the ablation transducer 510 may provide a circumferential ablation pattern. In such an instance, the ablation transducer 510 may include a backing layer to direct the acoustic energy in a single direction. In other embodiments, the ablation transducer 510 may be structured to radiate acoustic energy from two radiating surfaces.
In some embodiments, an electrical conductor such as the element 102 (as shown in FIG. 1) may connect the ablation transducer 510 to a control unit (such as control unit 108 in FIG. 1). In some embodiments, the electrical conductor(s) may be disposed within a lumen of the elongated shaft 508. In other embodiments, the electrical conductor(s) may extend along an outside surface of the elongated shaft 508. The electrical conductor(s) may provide electricity to the ablation transducer 510, which may then be converted into acoustic energy. The acoustic energy may be directed from the ablation transducer 510 in a direction generally perpendicular to the radiating surfaces of the transducer 510. As discussed above, acoustic energy radiates from the ablation transducer 510 in a pattern related to the shape of the transducer 510 and lesions formed during ablation take shape similar to contours of the pressure distribution.
The system 500 can further include an expandable frame or basket 512 having a proximal end 513 and a distal end 515. The proximal end 513 of the basket 512 may be affixed to the elongate shaft 508 proximal to the transducer 510. In some instances, the proximal end 513 of the basket 512 may be secured to the first tubular member 522, although this is not required. The distal end 515 of the basket 512 may be affixed to the elongate shaft 508 distal to the transducer 510. In some instances, the distal end 515 of the basket 512 may be secured to the second tubular member 524, although this is not required. The proximal and distal ends 513, 515 of the basket 512 may be affixed to the elongate shaft 508 in any manner desired. For example, in some instances, a band or retaining element may be used to secure the proximal and distal ends 513, 515. In other instances, the proximal and distal ends 513, 515 may be secured to the elongate shaft 508 with an adhesive or other suitable method. It is further contemplated that either or both of the proximal or distal ends 513, 515 may be secured to an element other than the elongate shaft 508 to facilitate expansion and/or contraction of the basket 512.
The expandable basket 512 may include one or more longitudinally extending struts 514a , 514b , 514c , 514d , 514e , and 514f (collectively referred to hereinafter as struts 514). Although six struts 514 are shown in FIG. 5, it should be noted that any suitable number of struts 514 may be employed for desired purposes. Further, the expandable basket 512 may be configured to actuate between a first collapsed configuration and a second expanded configuration (shown in FIG. 5), which may include transition of the struts 514 from a generally straight configuration to a curved configuration, respectively. More particularly, the struts 514 in the collapsed configuration may extend and/or straighten to be generally parallel with or generally extend along the longitudinal length of the elongate shaft 508. In contrast, in the second expanded configuration, the struts 514 may expand and/or curve like the ribs of an umbrella to surround the ablation transducer 510.
According to embodiments of the present disclosure, the expandable basket 512 is adapted to align and position the ablation transducer 510 within the body lumen 504. To accomplish this, the expandable basket 512 may expand to meet the vessel wall 502, as discussed above. As shown in FIG. 5, the expandable basket 512 in the second expanded configuration may be arranged and positioned to generally surround the ablation transducer 510 circumferentially to approximately center the ablation transducer 510 within the lumen 504. In such an instance, the expandable basket 512 may facilitate circumferential ablation of the target region while allowing continued blood flow along the lumen 504. In some other embodiments, although not shown, the expandable basket 512 may include one or more electrodes, sensors, or transducers disposed along the struts 514 such as to contact the vessel wall 502, thereby monitoring a particular characteristic or creating one or more lesions during the ablation procedure.
The expandable basket 512 may be self-expandable, or may require external force to expand. A self-expandable expandable basket 512 may be formed of any material or structure that is in a compressed state when force is applied and in an expanded state when force is released. Such material may include, for example, shape memory alloys such as Nitinol or any other self-expandable material commonly known in the art. When employing such shape-memory materials, the expandable basket 512 may be heat set in the expanded state and then compressed to fit within a delivery sheath such as a guide sheath (not explicitly shown), for example. Upon reaching the target location within the body lumen 504, the guide sheath can be retracted to deploy the expandable basket 512 in the expanded configuration. The guide sheath may have similar form and function to the guide sheath 222 as shown in FIG. 2.
In addition, the system 500 may include an actuation mechanism, for example, a pull wire, which may be employed to manipulate or actuate the expandable basket 512 between the collapsed and expanded configurations discussed above. Although not shown, an actuation element such as a wire may be attached to the proximal end 513 or distal end 515 of the expandable basket 512 such that a push-pull mechanism of the wire may manipulate the expandable basket 512, thus actuating the expandable basket 512 between the collapsed and expanded configurations, respectively. In some instances, the wire may be pulled proximally to compress the length of expandable basket 512, switching the expandable basket 512 to the expanded configurations. In addition, the wire may be pushed distally to elongate the expandable basket 512 into the collapsed configuration. Alternatively, the wire may be pushed distally, compress the length of the expandable basket 512 thus expanding the struts 514 into the expanded state. In such an instance, the wire may be pulled proximally, which may allow the expandable basket 512 to elongate the basket 512 into the collapsed state.
The system can further include one or more temperature sensors 516a and 516b (collectively referred to hereinafter as sensors 516) coupled to the expandable basket 512. Although two temperature sensors 516 are shown, it should be noted that any suitable number of temperature sensors 516 may employed for desired purposes. In addition, other suitable sensors, such as impedance sensors, may also be employed. As shown, the temperature sensors 516 may be placed on the struts 514 such as to contact the vessel wall 502 in the expanded configuration. The contact between the sensors 516 and the wall 502 may allow measuring of temperature of the vessel wall 502 during the ablation procedure. According to an example, the temperature sensors 516 may include one or more thermocouple, which may be employed to monitor wall 502 temperatures.
Further, the system 500 may include one or more infusion sheaths 518 having a proximal end 534, a distal end 536 and a lumen 538 extending therethrough. In some embodiments, the proximal end 534 of the infusion sheath 518 may be secured to the catheter shaft 508 adjacent to the distal end 521 of the first tubular member 522. It is contemplated that the infusion sheath 518 may be attached either temporarily or permanently to the catheter shaft 508. Suitable attachment means may include adhesives, heat shrinking, or other suitable means known to those skilled in the art. The distal end 536 of the infusion sheath 518 may be open to allow an infusion fluid 506 to exit the sheath 518. The infusion sheath 518 may be configured to extend distally from the distal end 521 of the first tubular member 522 such that a portion of the distal end region 532 of the second tubular member 524 is disposed within or partially within the lumen 538 of the infusion sheath 518. In some instances, the distal end 530 of the second tubular member 524 may extend beyond the distal end 536 of the infusion sheath 518, but this is not required. In some instances, the ablation transducer 510 may be disposed within or partially within the lumen 538 of the infusion sheath 518, although this is not required. In some instances, the lumen 538 of the infusion sheath may be in fluid communication with the lumen 528 of the first tubular member 522 for receiving an infusion fluid. Saline or other suitable infusion fluid 506 may be flushed through the infusion lumen 528 and into the lumen 538 of the infusion sheath 518. The infusion fluid 506 may displace blood from around the transducer 510. As the infusion fluid 506 flows past the ablation transducer 510, the infusion fluid 506 may provide convective cooling to the transducer 510. It is further contemplated that by displacing and/or cooling the blood surrounding the transducer 510, blood damage, fouling of the transducer 510, and/or overheating of the transducer 510 may be reduced or eliminated. In some instances, this may allow the modulation system 500 to be operated at a higher power level, thus providing a shorter treatment and/or more effective modulation of the target tissue. In some embodiments, the infusion sheath 518 may be structured to direct some or all of the infusion fluid 506 along the inside of the vessel wall 502. While blood flowing through the vessel lumen 504 removed some heat from the wall tissue, the addition of a “cooling” flush via infusion fluid 506 directed towards the vessel wall 502 may allow the application of more power for a shorter time period. It is contemplated that the infusion fluid 506 may be introduced into the modulation system 500 before, during, or after ablation. Flow of the infusion fluid 506 may begin before energy is supplied to the ablation transducer 510 and continue for the duration of the modulation procedure.
It is contemplated that the infusion sheath 518 may be formed from a material that is sonically translucent such that the ultrasound energy may pass through the infusion sheath 518. In some instances, the infusion sheath may be formed from a polymeric material having a low loss proper acoustic impedance. It is contemplated that the infusion sheath 518 may have a thickness such that significant attenuation of the ultrasound energy is avoided.
The infusion fluid 506 may be saline or any other suitable infusion fluid. It is contemplated that the infusion fluid 506 may be provided at a variety of different temperatures depending on the desired treatment. In some instances, the infusion fluid 506 may be provided at room temperature, below room temperature, above room temperature, or at normal body temperature as desired. In some instances, such as when an imaging transducer is provided (not explicitly shown), a small amount of an imaging contrast material may be added to the infusion fluid 506 to facilitate imaging of the vessel. Suitable examples of such imaging contrast material may include, but are not limited to fluorine, iodine, barium, or the like.
In some embodiments, the infusion sheath 518 may be configured to transition between an expanded state and a collapsed state. It is contemplated that the infusion sheath 518 may be self-expanding or may be expanded using an actuation mechanism
Turning now to FIG. 6, a cross-section of a distal portion of another illustrative intravascular nerve modulation system 600 is depicted. The system 600 may include a hollow cylindrical ablation transducer 610, which may allow for cooling fluid 614 to pass through the lumen 609 of the transducer 610. The system 600 may further include an elongate catheter shaft 602 a support mandrel 612, and flexible mount members 606 and 616.
The catheter shaft 602 may include a first lumen 605, which may extend between a proximal end (not shown) and a distal end 603. The catheter shaft 602 is configured to be introduced within a body lumen (for example, body lumen 204 of FIG. 2). Although not shown, the proximal end of catheter shaft 602 may include a hub attached thereto for connecting other treatment devices or providing a port for facilitating other treatments. It is contemplated that the stiffness of the catheter shaft 602 may be modified to form the modulation system 600 for use in various vessel diameters and various locations within the vascular tree.
In the illustrated embodiment, the first lumen 605 may be configured to slidably receive a guidewire 620 therein. In some embodiments, a guide sheath similar to guide sheaths discussed above (not explicitly shown) may be used in addition to or in place of guidewire 620 to facilitate advancement of the system 600. In addition, the first lumen 605 may be employed for infusion of a fluid 614. Alternatively, the catheter shaft 602 may include separate lumen(s) (not shown) for infusion of fluid 614 or for other purposes such as introduction of a medical device, and so forth. The fluid 614 may facilitate cooling of the modulation system 600 and/or vessel wall during the ablation procedure. Further, the first lumen 605 may be configured in any way known in the art. For example, the first lumen 605 may extend along the entire length of the catheter shaft 602 such as in an over-the-wire catheter or may extend only along a distal portion of the catheter shaft 602 such as in a single operator exchange (SOE) catheter. These examples are not intended to be limiting, but rather examples of some possible configurations.
Further, the catheter shaft 602 may have a relatively long, thin, flexible tubular configuration. In some instances, the catheter shaft 602 may have a generally circular cross-section, however, other suitable configurations such as, but not limited to, rectangular, oval, irregular, or the like may also be contemplated. In addition, the catheter shaft 602 may have a cross-sectional configuration adapted to be received in a desired vessel, such as a renal artery. For instance, the catheter shaft 602 may be sized and configured to accommodate passage through the intravascular path, which leads from a percutaneous access site in, for example, the femoral, brachial, or radial artery, to a targeted treatment site, for example, within a renal artery.
Materials employed to manufacture the catheter shaft 602 may include any suitable biocompatible material. Examples may include metals, polymers, alloys, shape memory alloys, etc. Other suitable materials known in the art may also be employed.
While FIG. 6 illustrates a single ablation transducer 610, it is contemplated that the modulation system 600 may include any number of ablation transducers desired, such as, but not limited to two, three, or more. The ablation transducer 610 is configured to deliver acoustic energy (i.e., ultrasound waves) to a target tissue. At the targeted tissue, the acoustic energy is converted to heat resulting in protein denaturation and coagulative necrosis of the tissue and/or nerves at the target region. In some instances, the frequency of the ultrasound energy used for the procedure may be set so that the ablated area of tissue starts after it passes through the vessel wall thereby minimizing potential heat damage of the vessel wall.
As shown, the ablation transducer 610 may have a hollow cylindrical shape that may define a lumen 609. The lumen 609 may remain in fluid communication with the first lumen 605 and the through holes 607. Those skilled in the art, however, will appreciate that any suitable shape such as, but not limited to, square, rectangular, polygonal, circular, oblong, or the like may also be contemplated.
While the ablation transducer 610 is described as an ultrasonic transducer, it is contemplated that other methods and devices for raising the temperature of the target tissue (e.g., nerve) may be used, such as, but not limited to: radiofrequency, microwave, other acoustic, optical, electrical current, direct contact heating, or other heating.
The ablation transducer 610 may be formed from any suitable material such as, but not limited to, lead zirconate titanate (PZT). It is contemplated that other ceramic or piezoelectric materials may also be used. In some instances, the ablation transducer 610 may include a layer of gold, or other conductive layer, disposed on the acoustically functional areas of the transducer 610 surface for connecting electrical leads to the ablation transducer 610. It is contemplated that the sides/edges of the transducer crystal may be free of conductive material so as not to “short circuit” the transducer 610. In some instances, one or more tie layers may be used to bond the gold to the PZT. For example, a layer of chrome may be disposed between the PZT and the gold to improve adhesion. In other instances, the transducer 610 may include a layer of chrome over the PZT followed by a layer of nickel, and finally a layer of gold. These are just examples. It is contemplated that the layers may be deposited on the PZT using sputter coating, although other deposition techniques may be used as desired.
Although not shown, the ablation transducer 610 may have a radiating surface, and a perimeter surface extending around the outer edge of the ablation transducer 610. The acoustic energy from the radiating surface of the ablation transducer 610 may be transmitted in a spatial pressure distribution related to the shape of the ablation transducer 610. For instance, the cylindrical shape of the ablation transducer 610 may provide a circumferential ablation pattern. In such an instance, the ablation transducer 610 may include a backing layer to direct the acoustic energy in a single direction. In other embodiments, the ablation transducer 610 may be structured to radiate acoustic energy from two radiating surfaces.
Further, the ablation transducer 610 can be operably coupled to the distal end 603 of the catheter shaft 602 through a first flexible mount member 606. As shown, the first flexible mount member 606 may have a generally trapezoidal shape, however, it should be noted that the flexible mount may take on any suitable shape such as rectangular, cylindrical, triangular, or the like. The first flexible mount member 606 may be affixed to the distal end 603 of the catheter shaft 602 at a proximal end 624, while being coupled to a proximal end 618 of the ablation transducer 610 at a distal end 626 thereof. In some instances, the first flexible mount 606 may include a proximal end 624 sized and shaped to be received within the lumen 605 of the catheter shaft 602, although this is not required. In some instances, the first flexible mount member 606 may be positioned along and secured to an outside surface of the catheter shaft 602. It is contemplated that the first flexible mount 606 may be secured to the catheter shaft 602 using any method desired, such as, but not limited to, adhesives, thermal bonding, heat shrinking, etc. The distal end 626 of the first flexible mount 606 may be secured to the proximal end 618 of the transducer 610 through a flexible adhesive 608a. In some instances, the flexible adhesive 608a may comprise silicone or other like materials.
Referring to FIGS. 6 and 7, the first flexible mount 606 may include a central lumen having an inner surface 628. The inner surface 628 may be fixedly secured to the proximal end 630 of the support mandrel 612 through any means desired. The first flexible mount 606 may further include one or more through holes 607a , 607b , 607c, 607d (collectively 607) extending from the proximal end 624 to the distal end 626 of the mount 606. For clarity, not all of the through holes 607 have been numbered in FIG. 7. The through holes 607 may be sized and shaped to allow an infusion fluid 614 to pass through the flexible mount 606. It is contemplated that the first flexible mount 606 may include any number of through holes desired, such as, but not limited to, one, two, three, four, or more. It is further contemplated that the through holes 607 may be arranged in any manner desired. For example, in some instances, the through holes 607 may be randomly scattered about the cross-section of the first flexible mount 606. In other instances, the through holes 607 may be arranged in a pattern. While FIG. 7 illustrates the through holes 607 as a single ring of holes, it is contemplated that there may be multiple rings (or other geometric configurations) across the cross-section of the first flexible mount 606. The through holes 607 may be in fluid communication with the first lumen 605 of the catheter shaft 602 and the lumen 609 of the transducer 610.
Further, the ablation transducer 610 can be operably coupled to the distal end 632 of the support mandrel 612 through a second flexible mount member 616. As shown, the second flexible mount member 616 may have a generally tapered proximal end 636 and a rounded atraumatic distal end 638, however, the second flexible mount may take on any suitable shape such as rectangular, cylindrical, triangular, or the like. The second flexible mount member 616 may be affixed to the distal end 622 of the ablation transducer 610 at a proximal end 636 thereof. The proximal end 636 of the second flexible mount 616 may be secured to the distal end 622 of the transducer 610 through a flexible adhesive 608b. In some instances, the flexible adhesive 608b may comprise silicone or other like materials.
The second flexible mount 616 may include a central lumen having an inner surface 634. The inner surface 634 may be fixedly secured to the distal end 632 of the support mandrel 612 through any means desired. The second flexible mount 616 may further include one or more through holes 615a , 615b (collectively 615) extending from the proximal end 636 to the distal end 638 of the mount 616. The through holes 615 may be sized and shaped to allow an infusion fluid 614 to pass through the flexible mount 616. It is contemplated that the second flexible mount 616 may include any number of through holes desired, such as, but not limited to, one, two, three, four, or more. number of through holes desired, such as, but not limited to, one, two, three, four, or more. It is further contemplated that the through holes 615 may be arranged in any manner desired. For example, in some instances, the through holes 615 may be randomly scattered about the cross-section of the second flexible mount 616. In other instances, the through holes 607 may be arranged in a pattern. The through holes 615 may be in fluid communication with the lumen 609 of the transducer 610 and may have a distal opening thus allowing the infusion fluid 614 to exit the system 600.
The support mandrel 612 may be configured to be disposed within the lumen 609 of the hollow cylindrical ablation transducer 610. As illustrated, the support mandrel may extend generally parallel with and along the length of the ablation transducer 610. As discussed above, the support mandrel 612 may be fixedly secured to inner lumens of the first and the second flexible mount members 606, 616. The flexible mounts 606, 616 may attached the transducer 610 to the support mandrel 612 to minimize interference with the transducer vibration. The support mandrel 612 may have a generally hollow cylindrical shape defining a lumen 611 extending from the proximal end 630 to the distal end 632 of the support mandrel 612. However, other suitable shapes of the support mandrel 612 including, for example, rectangular, irregular, or the like may also be contemplated. Further, the material employed to manufacture may include any suitable biocompatible material such as, but not limited to, metals, polymers, alloys, shape memory alloys or the like. The lumen 611 may be configured to receiving a guidewire 620 therethrough. In some embodiments, the lumen 611 may be in fluid communication with the lumen 605 of the catheter shaft 602 and thus some infusion fluid 614 may pass through lumen 611 and exit the system 600.
Saline or other suitable infusion fluid 614 may be flushed through the lumen 605 of the catheter shaft 602, through the through holes 607 of the first flexible mount 606, and into the lumen 609 of the transducer 610. The infusion fluid 614 may cool the transducer 610, reduce transducer damage, reduce surface fouling, reduce damage to the blood and other non-target tissue, and/or reduce overheating of the transducer 610 may be reduced or eliminated. The infusion fluid 614 may exit the system 600 via through holes 615 in the second flexible mount 616. It is contemplated that some infusion fluid 614 may also enter the lumen 611 of the support mandrel 613 from the lumen 605 of the catheter shaft 602 and exit the system via the distal end 632 of the support mandrel. In some instances, this may allow the modulation system 600 to be operated at a higher power level, thus providing a shorter treatment and/or more effective modulation of the target tissue. It is contemplated that the infusion fluid 614 may be introduced into the modulation system 600 before, during, or after ablation. Flow of the infusion fluid 614 may begin before energy is supplied to the ablation transducer 610 and continue for the duration of the modulation procedure.
Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departure in form and detail may be made without departing from the scope and spirit of the present disclosure as described in the appended claims.

## Claims

1. An intravascular nerve modulation system, comprising:
an elongate shaft having a proximal end, a distal end, and an infusion lumen extending therebetween;
an ablation transducer comprising an ultrasound transducer affixed to the elongate shaft adjacent the distal end thereof;
an expandable basket having a proximal end and a distal end, the proximal end affixed to the elongate shaft proximal of a proximal end of the ablation transducer and the distal end is affixed to the elongate shaft distal of a distal end of the ablation transducer;
an infusion sheath secured adjacent to the distal end of the elongate shaft in fluid communication with the infusion lumen, wherein the infusion sheath extends over the ablation transducer and is located within the expandable basket;
wherein the system is configured to transport infusion fluid through the infusion lumen and past the ablation transducer thereby providing convective cooling to the ablation transducer; and
wherein the expandable basket is configured to actuate between a first collapsed configuration and a second expanded configuration.

2. The nerve modulation system of claim 1, further comprising one or more temperature sensors coupled to the expandable basket.

3. The nerve modulation system of claim 1, wherein the expandable basket comprises two or more generally longitudinally extending struts.

4. The nerve modulation system of claim 1, further comprising a pull wire affixed to one of the distal end or the proximal end of the expandable basket.

5. The nerve modulation system of claim 4, wherein actuation of the pull wire moves the expandable basket between the first collapsed position and the second expanded position.

6. The nerve modulation system of claim 1, wherein the expandable basket is configured to self-expand.

7. The intravascular nerve modulation system at claim 1, wherein the elongate shaft comprises a first tubular member and a second tubular member and wherein said infusion lumen is located between the first tubular member and the second tubular member.

8. The intravascular nerve modulation system of claim 1, wherein the ablation transducer is a hollow ablation transducer that comprises a transducer lumen in fluid communication with the infusion lumen.

9. The intravascular nerve modulation system of claim 8, further comprising a flexible mount, wherein the ablation transducer is affixed to the elongate shaft through the flexible mount, and wherein the flexible mount comprises one or more lumens establishing fluid communication between the infusion lumen and the transducer lumen to allow the infusion fluid to be transported through the transducer lumen.

10. An intravascular nerve modulation system, comprising:
an elongate shaft having a proximal end region, a distal end region and an infusion lumen extending therebetween;
an ablation transducer comprising an ultrasound transducer coupled to the distal end region of the shaft;
an expandable basket coupled to the distal end region of the shaft, the expandable basket having a proximal end disposed proximal of the ablation transducer and a distal end disposed distal of the ablation transducer;
an infusion sheath secured adjacent to the distal end of the elongate shaft in fluid communication with the infusion lumen, wherein the infusion sheath extends over the ablation transducer and is located within the expandable basket;
wherein the system is configured to transport infusion fluid through the infusion lumen and past the ablation transducer thereby providing convective cooling to the ablation transducer;
wherein the expandable basket is capable of shifting between a first configuration and an expanded configuration;
and a sensor coupled to the expandable basket.

11. The intravascular nerve modulation system claim 10, wherein the sensor includes a temperature sensor.

12. The intravascular nerve modulation system of claim 11, wherein the sensor is designed to monitor the temperature of a vessel wall during an ablation procedure.

13. The intravascular nerve modulation system claim 10, wherein the sensor includes an impedance sensor.

14. The intravascular nerve modulation system of claim 10, wherein the sensor is designed to contact a vessel wall during an ablation procedure.

15. The intravascular nerve modulation system of claim 10, wherein the sensor is designed to monitor the progress of an ablation procedure.

16. The intravascular nerve modulation system of claim 10, wherein the expandable basket includes a plurality of struts and wherein the sensor is coupled to one of the struts.

17. The intravascular nerve modulation system of claim 10, wherein a plurality of sensors are coupled to the expandable basket.

18. An intravascular nerve modulation system, comprising:
an elongate shaft having a proximal end region, a distal end region and an infusion lumen extending therebetween;
an ultrasound transducer coupled to the distal end region of the shaft;
an expandable basket coupled to the distal end region of the shaft, the expandable basket having a proximal end disposed proximal of the ultrasound transducer and a distal end disposed distal of the ultrasound transducer;
an infusion sheath secured adjacent to the distal end of the elongate shaft in fluid communication with the infusion lumen, wherein the infusion sheath extends over the ablation transducer and is located within the expandable basket;
wherein the system is configured to transport infusion fluid through the infusion lumen and past the ablation transducer thereby providing convective cooling to the ablation transducer;
wherein the expandable basket is capable of shifting between a first configuration and an expanded configuration;
a sensor coupled to the expandable basket;
wherein the sensor is capable of contacting a vessel wall when the basket is in the expanded configuration; and wherein the sensor is designed to monitor the progress of ablation by the ultrasound transducer during an ablation procedure.

19. The intravascular nerve modulation system claim 18, wherein the sensor includes a temperature sensor, an impedance sensor, or both.