Source: http://www.google.com/patents/US7881807?ie=ISO-8859-1&dq=system+for+measuring+web+traffic
Timestamp: 2014-09-18 04:05:40
Document Index: 641991585

Matched Legal Cases: ['Art, 1993', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Art 1993', 'Art 1993']

Patent US7881807 - Balloon anchor wire - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsThe present invention relates to an anchor device comprising an elongated tubular body having an expandable member disposed on its distal end portion. The invention also relates to a system adapted to position and anchor the distal end of an ablation device at a location where a pulmonary vein extends...http://www.google.com/patents/US7881807?utm_source=gb-gplus-sharePatent US7881807 - Balloon anchor wireAdvanced Patent SearchPublication numberUS7881807 B2Publication typeGrantApplication numberUS 10/447,921Publication dateFeb 1, 2011Filing dateMay 29, 2003Priority dateMay 11, 1999Fee statusPaidAlso published asCA2369312A1, CA2369312C, DE60033232D1, DE60033232T2, EP1179995A2, EP1179995B1, EP2289448A1, EP2289448B1, EP2305161A1, US6595989, US20030195510, WO2000067832A2, WO2000067832A3Publication number10447921, 447921, US 7881807 B2, US 7881807B2, US-B2-7881807, US7881807 B2, US7881807B2InventorsAlan K. SchaerOriginal AssigneeSchaer Alan KExport CitationBiBTeX, EndNote, RefManPatent Citations (110), Non-Patent Citations (21), Referenced by (3), Classifications (34), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetBalloon anchor wireUS 7881807 B2Abstract The present invention relates to an anchor device comprising an elongated tubular body having an expandable member disposed on its distal end portion. The invention also relates to a system adapted to position and anchor the distal end of an ablation device at a location where a pulmonary vein extends from the atrium.
1. A method of ablating a region of tissue at a location where a pulmonary vein extends from an atrium, comprising:
inserting a transeptal sheath through an atrial septum that separates a right atrium from the left atrium;
inserting a guide member having a preshaped distal portion with a predetermined shape and a lumen in at least the preshaped distal portion through the transeptal sheath from the right atrium into the left atrium whereby the guide member takes the predetermined shape automatically external to the transeptal sheath;
pointing the preshaped distal portion of the guide member towards a predetermined pulmonary vein by adjustably advancing the guide member through the transeptal sheath, controlling the shape of the preshaped distal portion;
after advancing the guide member, slidably advancing an anchor device through the lumen of the guide member and into the atrium, the anchor device being adapted to be positioned within the pulmonary vein and having an elongate body with a proximal end portion and a distal end portion, and also having an expandable member along the distal end portion adjustable between a radially collapsed condition and a radially expanded condition that is adapted to engage the pulmonary vein;
2. The method of claim 1, wherein prior to advancing the ablation catheter over the anchor device, the guide member is removed.
RELATED APPLICATIONS This application is a divisional of U.S. application Ser. No. 09/569,735 filed on May 11, 2000, now U.S. Pat. No. 6,595,989 and claims priority thereto under 35 U.S.C. �120 and 121.
Normal cardiac rhythm is maintained by a cluster of pacemaker cells, known as the sinoatrial (�SA�) node, located within the wall of the right atrium. The SA node undergoes repetitive cycles of membrane depolarization and repolarization, thereby generating a continuous stream of electrical impulses, called �action potentials.� These action potentials orchestrate the regular contraction and relaxation of the cardiac muscle cells throughout the heart. Action potentials spread rapidly from cell to cell through both the right and left atria via gap junctions between the cardiac muscle cells. Atrial arrhythmia's result when electrical impulses originating from sites other than the SA node are conducted through the atrial cardiac tissue.
Several surgical approaches have been developed for the treatment of atrial fibrillation. For example, Cox, J L et al. disclose the �maze� procedure, in �The Surgical Treatment Of Atrial Fibrillation. I. Summary�, Thoracic and Cardiovascular Surgery 101(3):402-405 (1991) and �The Surgical Treatment Of Atrial Fibrillation. IV. Surgical Technique�, Thoracic and Cardiovascular Surgery 101(4):584-592 (1991). In general, the maze procedure is designed to relieve atrial arrhythmia by restoring effective SA node control through a prescribed pattern of incisions about the cardiac tissue wall. Although early clinical studies on the maze procedure included surgical incisions in both the right and left atrial chambers, more recent reports suggest that the maze procedure may be effective when performed only in the left atrium (see for example Sueda et al., �Simple Left Atrial Procedure For Chronic Atrial Fibrillation Associated With Mitral Valve Disease� (1996)).
For the purpose of comparison, ablation catheter devices and related methods have also been disclosed for the treatment of ventricular or supraventricular tachycardias, such as disclosed by Lesh, M D in �Interventional Electrophysiology�State Of The Art, 1993� American Heart Journal, 126:686-698 (1993) and U.S. Pat. No. 5,231,995 to Desai.
An example of an ablation method targeting focal arrhythmia's originating from a pulmonary vein is disclosed by Haissaguerre et al. in �Right And Left Atrial Radiofrequency Catheter Therapy Of Paroxysmal Atrial Fibrillation� in J. Cardiovasc. Electrophys. 7(12):1132-1144 (1996). Haissaguerre et al. describe radiofrequency catheter ablation of drug-refractory paroxysmal atrial fibrillation using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci in a screened patient population. The site of the arrhythmogenic foci was generally located just inside the superior pulmonary vein, and was ablated using a standard 4 mm tip single ablation electrode.
Another ablation method directed at paroxysmal arrhythmia's arising from a focal source is disclosed by Jais et al. �A Focal Source Of Atrial Fibrillation Treated By Discrete Radiofrequency Ablation� Circulation 95:572-576 (1997). At the site of arrhythmogenic tissue, in both right and left atria, several pulses of a discrete source of radiofrequency energy were applied in order to eliminate the fibrillatory process.
Application of catheter-based ablation techniques for treatment of reentrant wavelet arrhythmia's demanded development of methods and devices for generating continuous linear lesions, like those employed in the maze procedure. Initially, conventional ablation tip electrodes were adapted for use in �drag burn� procedures to form linear lesions. During the �drag� procedure, as energy was being applied, the catheter tip was drawn across the tissue along a predetermined pathway within the heart. Alternatively, sequentially positioning the distal tip electrode, applying a pulse of energy, and then re-positioning the electrode along a predetermined linear pathway also made lines of ablation.
Examples of catheter-based cardiac chamber segmentation procedures, particularly in the treatment of Wolff-Parkinson-White syndrome, are disclosed by Avitall et al. �Physics And Engineering Of Transcatheter Tissue Ablation� J. Am. College of Cardiology, 22(3):921-932 (1993) and Haissaguerre et al. �Right And Left Atrial Radiofrequency Catheter Therapy Of Paroxysmal Atrial Fibrillation� J. Cardiovasc. Electrophys. 7(12):1132-1144 (1996).
SUMMARY OF THE INVENTION The present invention relates to a tissue ablation system for ablating a region of tissue at the location where a pulmonary vein extends from an atrium in a patient. The tissue ablation system includes an anchor device adapted to be positioned within the pulmonary vein and an ablation device. The anchor device has an elongate body with a proximal end portion and a distal end portion. It also has an expandable member along the distal end portion that is adjustable between a radially collapsed condition and a radially expanded condition that is adapted to engage the pulmonary vein. The ablation device comprises an elongate catheter having a proximal region and a distal region. The ablation device has an ablation element located along the distal region, wherein the ablation device is adapted to slideably engage and track over the anchor device. By advancing the ablation device distally over the anchor device, which is positioned in the pulmonary vein, the ablation element can be positioned at the region of tissue to be ablated.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a cross-sectional view of the preferred fixed corewire balloon anchor wire in accordance with a preferred mode of the present invention, in which the corewire extends along the entire length of balloon anchor wire.
FIG. 1B is a cross-sectional view of a variation of the fixed corewire balloon anchor wire of the present invention, in which the corewire extends only partially through the balloon anchor wire.
FIG. 3A is a cross-sectional view of an over-the-wire variation of the balloon anchor wire of the present invention, in which a balloon anchor catheter slideably engages a guidewire and a balloon is expanded; FIG. 3B is an enlarged view of the balloon in FIG. 3A.
FIG. 4 is a perspective view of the fixed corewire variation of the balloon anchor wire showing the Y-adapter on the proximal end of the balloon anchor wire.
FIG. 5 is a perspective view of a transeptal sheath in accordance with the present invention.
FIG. 7A is a schematic view of the guide system of the present invention showing the relationship of the transeptal sheath, the pre-shaped guide member and the balloon anchor wire in situ.
FIG. 7B is a schematic view of the proximal guidewire variation of the guide system of the present invention, showing the relationship of the transeptal sheath, the pre-shaped guide member, the balloon anchor wire and the proximal guidewire in situ.
FIG. 8 is a perspective view of a variation of the ablation catheter of the present invention showing a proximal guidewire.
FIG. 9 is a perspective view of the guide system of the present invention, showing tracking of the distal end of the ablation catheter over the balloon anchor wire.
FIG. 10 is a schematic view of the proximal guidewire variation of the guide system of the present invention showing the relationship of the transeptal sheath, the balloon anchor wire, the proximal guidewire and the ablation catheter in situ.
FIG. 11 is a longitudinal cross-sectional view of an anchor device in accordance with a preferred mode of the present invention, showing an over-the-wire catheter with an ultrasound ablation element positioned along the distal end portion within an expandable member.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Balloon Anchor Wire
A cross-sectional view of the preferred �fixed corewire� balloon anchor wire of the present invention is shown in FIG. 1A. The balloon anchor wire 10 consists of a tubular member 12 with a balloon 14 attached to the distal region 16 of the tubular member. The tubular member is fitted over an integral corewire 18. The corewire 18 extends through the entire length of the tubular member, providing support (e.g., enhancing push force and kink resistance). The distal region 20 of the corewire 18 is tapered providing greater flexibility to the distal region 16 of the tubular member. The distal end 22 of the corewire 18 is bonded to the distal end 24 of the tubular member 12. The bond between the corewire and the tubular member is airtight, so that the balloon can be inflated. A wire coil 26 may be placed over the distal end 22 of the corewire to help provide support to the corewire and prevent kinking. Preferably, the wire coil 26 protrudes distally from the balloon as illustrated in FIGS. 1A & B to aid in atraumatic navigation of vessel branches.
(1) U.S. patent application Ser. No. 08/853,861 filed May 9, 1997 for �Tissue Ablation Device And Method Of Use�, now U.S. Pat. No. 5,971,983; (2) U.S. patent application Ser. No. 08/889,798 filed Jul. 8, 1997 for �Circumferential Ablation Device Assembly�, now U.S. Pat. No. 6,024,740; (3) U.S. patent application Ser. No. 08/889,835 filed Jul. 8, 1997 for �Device And Method For Forming A Circumferential Conduction Block In A Pulmonary Vein�, now U.S. Pat. No. 6,012,457; (4) U.S. patent application Ser. No. 09/073,907 filed May 6, 1998 for �Tissue Ablation Device With Fluid Irrigated Electrode�; (5) U.S. patent application Ser. No. 09/199,736 filed Nov. 25, 1998 for �Circumferential Ablation Device Assembly�; (6) U.S. patent application Ser. No. 09/240,068 filed Jan. 29, 1999 for �Device And Method For Forming A Circumferential Conduction Block In A Pulmonary Vein�; (7) U.S. patent application Ser. No. 09/260,316 filed Mar. 1, 1999 for �Tissue Ablation System And Method For Forming Long Linear Lesion�; (8) Provisional U.S. Application No. 60/122,571, Filed on Mar. 2, 1999 for �Feedback Apparatus And Method For Ablation At Pulmonary Vein Ostium�; (9) Provisional U.S. Application No. 60/125,509, filed Mar. 19, 1999 for �Circumferential Ablation Device Assembly And Methods Of Use And Manufacture Providing An Ablative Circumferential Band Along An Expandable Member�; (10) Provisional U.S. Application No. 60/125,928, filed Mar. 23, 1999 for �Circumferential Ablation Device Assembly And Methods Of Use And Manufacture Providing An Ablative Circumferential Band Along An Expandable Member�; (11) Provisional U.S. Application No. 60/133,807, filed May 11, 1999 for �Catheter Positioning System�; (12) Provisional U.S. Application No. 60/133,680, filed May 11, 1999 for �Apparatus And Method Incorporating An Ultrasound Transducer�; (13) Provisional U.S. Application No. 60/133,677, filed May 11, 1999 for �Tissue Ablation Device Assembly And Method For Electrically Isolating A Pulmonary Vein Ostium From A Posterior Left Atrial Wall�;
Exemplary variations of the tissue ablation catheter include ablation assemblies having an irrigated ablation member that is attached to a delivery member in order to access and position the ablation member at the site of the target tissue. The delivery member takes the form of an over-the-wire catheter, wherein the �wire� is the balloon anchor wire. The delivery member comprises an elongated body with proximal and distal end portions. As used herein, the terms �distal� and �proximal� are used in reference to a source of fluid located outside the body of the patient. The elongated body preferably includes a balloon anchor wire lumen, an electrical lead lumen and a fluid lumen, as described in greater detail below.
Notwithstanding the specific delivery device constructions just described, other delivery mechanisms for delivering the ablation member to a desired ablation region are also contemplated. For example, while an �over-the-wire� catheter construction was described, other balloon anchor wire tracking designs may also be suitable substitutes, such as for example catheter devices known as �rapid exchange� or �monorail� variations wherein the balloon anchor wire is only housed within a lumen of the catheter in the distal regions of the catheter. In another example, a deflectable tip design may also be a suitable substitute. The latter variation can also include a pullwire which is adapted to deflect the catheter tip by applying tension along varied stiffness transitions along the catheter's length. Further more detailed examples of deflectable tip members are disclosed in the following references: U.S. Pat. No. 5,549,661 to Kordis et al.; PCT Publication WO 94/21165 to Kordis et al.; and U.S. Pat. No. 5,592,609 to Swanson et al.; PCT Publication WO 96/26675 to Klein et al. The disclosures of these references are incorporated herein in their entirety by reference thereto.
As known in the art, the ablation actuator is connected to both of the electrical connectors and to a ground patch. A circuit thereby is created which includes the ablation actuator, the ablation member, the patient's body, and the ground patch that provides either earth ground or floating ground to the current source. In the circuit, an electrical current, such as a radiofrequency, (�RF�) signal may be sent through the patient between the ablation member and the ground patch, as well known in the art.
The ablation member has a generally tubular shape and includes an ablation element. The phrase �ablation element� as used herein means an element that is adapted to substantially ablate tissue in a body space wall upon activation by an actuator. The terms �ablate� or �ablation,� including derivatives thereof, are hereafter intended to mean the substantial altering of the mechanical, electrical, chemical, or other structural nature of tissue. In the context of intracardiac ablation applications shown and described with reference to the variations of the illustrative embodiment below, �ablation� is intended to mean sufficient altering of tissue properties to substantially block conduction of electrical signals from or through the ablated cardiac tissue. The term �element� within the context of �ablation element� is herein intended to mean a discrete element, such as an electrode, or a plurality of discrete elements, such as a plurality of spaced electrodes, which are positioned so as to collectively ablate a region of tissue. Therefore, an �ablation element� according to the defined terms may include a variety of specific structures adapted to ablate a defined region of tissue. For example, one suitable ablation element for use in the present invention may be formed, according to the teachings of the embodiments below, from an �energy emitting� type that is adapted to emit energy sufficient to ablate tissue when coupled to and energized by an energy source.
Suitable �energy emitting� ablation elements for use in the present invention may therefore include, for example, but without limitation: an electrode element adapted to couple to a direct current (�DC�) or alternating current (�AC�) source, or a radiofrequency (�RF�) current source; an antenna element which is energized by a microwave energy source; a heating element, such as a metallic element or other thermal conductor which is energized to emit heat such as by convection or conductive heat transfer, by resistive heating due to current flow, a light-emitting element such as a laser, or an ultrasonic element such as an ultrasound crystal element which is adapted to emit ultrasonic sound waves sufficient to ablate tissue when coupled to a suitable excitation source. It also is understood that those skilled in the art can readily adapt other known ablation devices for use with the present ablation member.
The porous membrane includes an inner surface and an outer surface that define the boundaries of a porous wall. The wall is formed of a porous, biocompatible, generally non-compressible material. As used herein, the term �non-compressible� means that the material generally does not exhibit appreciable or sufficient compressibility between its inner and outer surfaces to conform to surface irregularities of the tissue against which the ablation member is placed. The material, however, is sufficiently flexible in the longitudinal direction (i.e., deflectable) so as to track over and along a balloon anchor wire positioned within the left atrium, and more preferably seated within one of the pulmonary veins that communicates with the left atrium. In other words, the material of the tubular porous membrane allows it to bend through a winding access path during in vivo delivery of the ablation member into the desired ablation region.
The electrodes of the ablation member desirably have sufficient flexibility to bend to track through a venous or arterial access path to an ablation target site. The electrodes can have a variety of configurations as long as they afford similar flexibility. For instance, the electrode can have a tubular or cylindrical shape formed by a plurality of braided wires. The end bands link the ends of the wires together to prevent the braided structure from unraveling. The end bands can also electrically couple the wires together. The bands though are sufficiently narrow so as not to meaningfully degrade the flexibility of the ablation element. Any braided pattern can work, but a �diamond� pattern mesh is preferred. The wires of the braid can either have rectangular (�flat�) or rounded cross sections. The wire material can be any of a wide variety of known biocompatible materials (such as those identified above in connection with the coil electrodes). In one mode, the braided electrode can be �wounded� before inserting into the tubular porous membrane. Once inserted, the electrode can be uncoiled to press against the inner surface of the tube. In this manner, the membrane can support the electrode.
An electrode can be constructed where the electrode is formed from a flat wire mesh that has been rolled into an arcuate structure. The structure may have a semi-cylindrical shape; however, the structure can extend through either more or less of an arc. Alternatively, the electrode may have a �fishbone� pattern, wherein the electrode includes a plurality of arcuate segments that extend from an elongated section which generally lie parallel to a longitudinal axis of the ablation member when assembled. The ends of each arcuate segment can be squared or rounded.
An electrode may also be formed in an �arches� pattern. A plurality of arch segments lie in series with two side rails interconnecting the corresponding ends of the arch segments. The arch segments are spaced apart from one another along the length of the electrode. Such embodiments can be formed by etching or laser cutting a tube of electrode material.
The thermocouples desirably are blended into the outer surface of the ablation member in order to present a smooth profile. Transition regions formed by either adhesive or melted polymer tubing, �smooth out� the surface of the ablation member as the surface steps up from the porous member outer surface to the thermocouple surface.
The balloon may be blown by conventional methods from any low-density polymers or copolymers known in the art, such as polyethylene, polypropylene, polyolefins, PET, nylon, urethane, silicon, or Cflex. In a working example, the balloon was made from an irradiated linear low density polyethylene of about 0.015″/0.027″ using pressurized air at about 50 psi in a hot box at about 360� F. The balloon OD ranged from about 0.050″ to about 0.250″ but preferably measured approximately 0.118″ (3.0 mm)�0.004″ at 8 atm. The working length of the balloon varied from about 4 mm to about 16 mm. Preferably, the working length measured about 10�2 mm. The shaft of the balloon had an ID ranging from about 0.010″ to about 0.100″, preferably about 0.030″ for about 8 cm proximal and about 2 cm distal to the balloon.
To neck the proximal and distal ends of the balloon to the shaft, a heat shield was first placed against the proximal taper of the balloon. Using a hot box set at 360� F., the proximal end of the balloon was necked down onto a 0.029″ OD mandrel for 10.5 cm. The region was again necked for 10 cm onto a 0.022″ OD mandrel, leaving the proximal 0.5 cm at 0.029″ ID. A heat shield was then placed against the distal taper of the balloon and the distal end of the balloon was necked for at least 1 cm onto a 0.018″ OD mandrel. Finally, the proximal 0.029″ ID segment was trimmed down to 0.4 mm and the distal necked segment was trimmed at about 3 mm distal to the balloon taper.
The tubular member may be made from any polymer known in the art. In a working example, a tubular member having an intermediate region and integral corewire, and a proximal region with no corewire (see FIG. 1B) was made. The intermediate region was constructed from a 0.025″/0.029″ polyimide tube. Using a hot box set to 750� F., the distal end of the tube was necked at least 5 mm onto a 0.022″ OD mandrel. The necked distal end was trimmed to 4 mm. The tube was marked at 100 cm from the necked distal end. Using the same process parameters as described above, the proximal end was necked at least 5 mm onto a 0.020″ OD mandrel. The necked proximal end was trimmed to 4 mm.
The proximal segment of the tubular member was constructed from a 0.022″/0.032″ polyimide tube. Using a hot box set to 750� F., the distal end was flared onto a 0.026″ mandrel for 4 mm. A 0.020″ mandrel was placed into the flared distal end and a 1-2 mm wide notch was made in the wall of the tube about 1 cm proximal to the flared distal end. The two shaft members were then joined. A 0.020″ mandrel was inserted through the length of the intermediate region shaft for support. The necked distal end of the intermediate region shaft was inserted into the 0.029″ ID proximal end of the balloon shaft. Loctite 498 adhesive was applied to the joint. The adhesive preferably wicked around the circumference of the joint. Loctite accelerator was applied as needed.
The corewire was prepared from a 115 cm length of either 0.014″ Guidant/ACS High Torque �Standard� or �Traverse� guidewire. The Teflon coating was sanded off the proximal end for 2 cm. The edge of the cut core was rounded. The wire was wiped with a solvent such as heptane to remove the silicon coating.
After leak testing the assembly with air at about 70 psi, the balloon was placed in a sheath of 0.037″ ID Teflon tubing. The sheathed balloon was heated in a heat box at 140� F. for about 1 minute. Dow 360 Silicon and MDX was applied to the shaft of the tubular member proximal to the balloon and allowed to cure.
In positioning the ablation element at the ablation region, a distal tip of a balloon anchor wire is first positioned within the left atrium according to a transeptal access method, which will be described in more detail below, and through the fossa ovalis. The right venous system is first accessed using the �Seldinger� technique, wherein a peripheral vein (such as a femoral vein), is punctured with a needle and the puncture wound is dilated with a dilator to a size sufficient to accommodate a introducer sheath. An introducer sheath that has at least one hemostatic valve is seated within the dilated puncture wound while relative hemostasis is maintained. With the introducer sheath in place, the balloon anchor wire is introduced through the hemostatic valve of the introducer sheath and is advanced along the peripheral vein, into the region of the vena cavae, and into the right atrium.
Once in the right atrium, the distal tip of the guiding catheter is positioned against the fossa ovalis in the intra-atrial septal wall. A �Brochenbrough� needle or trocar is then advanced distally through the guiding catheter until it punctures the fossa ovalis. A separate dilator can also be advanced with the needle through the fossa ovalis to prepare an access port through the septum for seating the transeptal sheath. Thereafter, the transeptal sheath replaces the needle across the septum and is seated in the left atrium through the fossa ovalis, thereby providing access for object devices through its own inner lumen and into the left atrium.
It is also contemplated that other left atrial access methods may be utilized for using the balloon anchor wire and tissue ablation member of the present invention. In one alternative variation, a �retrograde� approach may be used, wherein a guiding catheter is advanced into the left atrium from the arterial system. In this variation, the Seldinger technique is employed to gain vascular access into the arterial system, rather than the venous system, such as at a femoral artery. The guiding catheter is advanced retrogradely through the aorta, around the aortic arch, into the left ventricle, and then into the left atrium through the mitral valve.
An ablation member for use in forming a circumferential lesion, in accordance with another aspect of the present invention may take the form of annular ultrasonic transducer. The annular ultrasonic transducer has a unitary cylindrical shape with a hollow interior (i.e., is tubular shaped); however, the transducer applicator can have a generally annular shape and be formed of a plurality of segments. For instance, the transducer applicator can be formed by a plurality of tube sectors that together form an annular shape. The tube sectors can also be of sufficient arc lengths so as when joined together, the sectors assembly forms a �clover-leaf� shape. This shape is believed to provide overlap in heated regions between adjacent elements. The generally annular shape can also be formed by a plurality of planar transducer segments that are arranged in a polygon shape (e.g., hexagon). In addition, although in the illustrated embodiment the ultrasonic transducer comprises a single transducer element, the transducer applicator can be formed of a multi-element array, as described in greater detail below.
The central layer of the transducer has a thickness selected to produce a desired operating frequency. The operating frequency will vary of course depending upon clinical needs, such as the tolerable outer diameter of the ablation and the depth of heating, as well as upon the size of the transducer as limited by the delivery path and the size of the target site. As described in greater detail below, the transducer in the illustrated application preferably operates within the range of about 5 MHz to about 20 MHz, and more preferably within the range of about 7 MHz to about 10 MHz. Thus, for example, the transducer can have a thickness of approximately 0.3 mm for an operating frequency of about 7 MHz (i.e., a thickness generally equal to � the wavelength associated with the desired operating frequency).
The ultrasound transducer just described is combined with the overall device assembly according to the present embodiment as follows. In assembly, the transducer desirably is �air-backed� to produce more energy and to enhance energy distribution uniformity, as known in the art. In other words, the inner member does not contact an appreciable amount of the inner surface of transducer inner tubular member. This is because the piezoelectric crystal which forms central layer of ultrasound transducer is adapted to radially contract and expand (or radially �vibrate�) when an alternating current is applied from a current source and across the outer and inner tubular electrodes of the crystal via the electrical leads. This controlled vibration emits the ultrasonic energy that is adapted to ablate tissue and form a circumferential conduction block according to the present embodiment. Therefore, it is believed that appreciable levels of contact along the surface of the crystal may provide a dampening effect that would diminish the vibration of the crystal and thus limit the efficiency of ultrasound transmission.
For this purpose, the transducer seats coaxial about the inner member and is supported about the inner member in a manner providing a gap between the inner member and the transducer inner tubular member. That is, the inner tubular member forms an interior bore that loosely receives the inner member. Any of a variety of structures can be used to support the transducer about the inner member. For instance, spacers or splines can be used to coaxially position the transducer about the inner member while leaving a generally annular space between these components. In the alternative, other conventional and known approaches to support the transducer can also be used. For instance, O-rings that circumscribe the inner member and lie between the inner member and the transducer can support the transducer. More detailed examples of the alternative transducer support structures just described are disclosed in U.S. Pat. No. 5,620,479 to Diederich, issued Apr. 15, 1997, and entitled �Method and Apparatus for Thermal Therapy of Tumors,� and U.S. Pat. No. 5,606,974 to Castellano, issued Mar. 4, 1997, and entitled �Catheter Having Ultrasonic Device.� The disclosures of these references are herein incorporated in their entirety by reference thereto.
The tubing extends beyond the ends of transducer and surrounds a portion of the inner member on either side of the transducer. A filler can also be used to support the ends of the tubing. Suitable fillers include flexible materials such as, for example, but without limitation, epoxy, Teflon� tape and the like.
In one particular balloon-transducer combination, the ultrasound transducer preferably has a length such that the ultrasonically coupled band of the balloon skin, having a similar length d according to the collimated electrical signal, is shorter than the working length D of the balloon. According to this aspect of the relationship, the transducer is adapted as a circumferential ablation member, which is coupled to the balloon to form an ablation element along a circumferential band of the balloon, therefore forming a circumferential ablation element band that circumscribes the balloon. Preferably, the transducer has a length that is less than two-thirds the working length of the balloon, and more preferably is less than one-half the working length of the balloon. By sizing the ultrasonic transducer length d smaller than the working length D of the balloon�and hence shorter than a longitudinal length of the engagement area between the balloon and the wall of the body space (e.g., pulmonary vein ostium)�and by generally centering the transducer within the balloon's working length D, the transducer operates in a field isolated from the blood pool. A generally equatorial position of the transducer relative to the ends of the balloon's working length also assists in the isolation of the transducer from the blood pool. It is believed that the transducer placement according to this arrangement may be preventative of thrombus formation that might otherwise occur at a lesion sight, particularly in the left atrium.
In an alternative embodiment of the present invention, the balloon may have a �straight� configuration with a working length D and a relatively constant diameter between proximal and distal tapers. This variation is believed to be particularly well adapted for use in forming a circumferential conduction block along a circumferential path of tissue that circumscribes and transects a pulmonary vein wall. However, unless the balloon is constructed of a material having a high degree of compliance and conformability, this shape may provide for gaps in contact between the desired circumferential band of tissue and the circumferential band of the balloon skin along the working length of the balloon.
A similar shape for the balloon includes a bulbous proximal end. In this embodiment, the proximate bulbous end of the central region gives the balloon a �pear�-shape. More specifically, a contoured surface is positioned along the tapered working length L and between proximal shoulder and the smaller distal shoulder of balloon. This pear shaped embodiment is believed to be beneficial for forming the circumferential conduction block along a circumferential path of atrial wall tissue that surrounds and perhaps includes the pulmonary vein ostium. Circumferential lesion electrically isolates the respective pulmonary vein from a substantial portion of the left atrial wall. The device is also believed to be suited to form an elongate lesion which extends along a substantial portion of the pulmonary vein ostium, e.g., between the proximal edge of the lesion and the dashed line which marks a distal edge of such an exemplary elongate lesion.
The circumferential ablation device can also include additional mechanisms to control the depth of heating. For instance, the elongate body can include an additional lumen that is arranged on the body so as to circulate the inflation fluid through a closed system. A heat exchanger can remove heat from the inflation fluid and the flow rate through the closed system can be controlled to regulate the temperature of the inflation fluid. The cooled inflation fluid within the balloon can thus act as a heat sink to conduct away some of the heat from the targeted tissue and maintain the tissue below a desired temperature (e.g., 90� C.), and thereby increase the depth of heating. That is, by maintaining the temperature of the tissue at the balloon/tissue interface below a desired temperature, more power can be deposited in the tissue for greater penetration. Conversely, the fluid can be allowed to warm. This use of this feature and the temperature of the inflation fluid can be varied from procedure to procedure, as well as during a particular procedure, in order to tailor the degree of ablation to a given application or patient.
For various reasons, the �narrow pass filter� embodiment may be particularly well suited for use in forming circumferential conduction blocks in left atrial wall and pulmonary vein tissues according to the present invention. It is believed that the efficiency of ultrasound transmission from a piezoelectric transducer is limited by the length of the transducer, which limitations are further believed to be a function of the wavelength of the emitted signal. Thus, for some applications a transducer may be required to be longer than the length that is desired for the lesion to be formed. Many procedures intending to form conduction blocks in the left atrium or pulmonary veins, such as, for example, less-invasive �maze�-type procedures, require only enough lesion width to create a functional electrical block and to electrically isolate a tissue region. In addition, limiting the amount of damage formed along an atrial wall, even in a controlled ablation procedure, pervades as a general concern. However, a transducer that is necessary to form that block, or which may be desirable for other reasons, may require a length which is much longer and may create lesions which are much wider than is functionally required for the block. A �narrow pass� filter along the balloon provides one solution to such competing interests.
Another type of ultrasonic transducer that can be mounted to a torquible member within the balloon is formed by curvilinear section and is mounted on the inner member with its concave surface facing in a radially outward direction. The inner member desirably is formed with recess that substantially matches a portion of the concave surface of the transducer. The inner member also includes longitudinal ridges on the edges of the recess that support the transducer above the inner member such that an air gap is formed between the transducer and the inner member. In this manner, the transducer is �air-backed.� This spaced is sealed and closed in the manner described above.
While a number of variations of the invention have been shown and described in detail, other modifications and methods of use contemplated within the scope of this invention will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or subcombinations of the specific embodiments may be made and still fall within the scope of the invention. For example, the embodiments variously shown to be �guidewire� tracking variations for delivery into a left atrium and around or within a pulmonary vein may be modified to instead incorporate a deflectable/steerable tip instead of guidewire tracking and are also contemplated. Moreover, all assemblies described are believed useful when modified to treat other tissues in the body, in particular other regions of the heart, such as the coronary sinus and surrounding areas. Further, the disclosed assemblies may be useful in treating other conditions, wherein aberrant electrical conduction may be implicated, such as for example, heart flutter. Indeed, other conditions wherein catheter-based, directed tissue ablation may be indicated, such as for example, in the ablation of fallopian tube cysts. Accordingly, it should be understood that various applications, modifications and substitutions may be made of equivalents without departing from the spirit of the invention or the scope of the following claims.
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"Transcatheter Endomyocardial Laser Revascularization: A Feasibility Test", The Thoracic and Cardiovascular Surgeon, vol. 46, pp. 74-76, Apr. 1998.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS8740849Jan 28, 2013Jun 3, 2014Ablative Solutions, Inc.Peri-vascular tissue ablation catheter with support structuresWO2012145300A1 *Apr 17, 2012Oct 26, 2012Ablative Solutions, Inc.Expandable catheter system for peri-ostial injection and muscle and nerve fiber ablationWO2012145304A2 *Apr 17, 2012Oct 26, 2012Ablative Solutions, Inc.Expandable catheter system for peri-ostial injection and muscle and nerve fiber ablation* Cited by examinerClassifications U.S. Classification607/122, 607/126, 606/41, 606/47, 128/898International ClassificationA61B18/14, A61N1/00, A61B17/00, A61B17/22, A61F2/958Cooperative ClassificationA61B2017/22038, A61B18/1492, A61M2025/09008, A61M2025/0681, A61B2017/00867, A61B2017/22069, A61M25/10, A61B2017/00243, C08L2201/12, A61B17/22004, A61M2025/0183, A61B2018/00898, A61B2018/00285, A61M2025/09083, A61B2018/00214, A61B17/22012, A61B2018/00839, A61B2017/003, A61B2017/00292, A61B2018/00577, A61M25/09European ClassificationA61B18/14V, A61B17/22B, A61M25/09Legal EventsDateCodeEventDescriptionJul 2, 2014FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google