US 20050165391 A1
This invention is related to a tissue ablation system and method that treats atrial arrhythmia by ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. The system includes a circumferential ablation member with an ablation element and also includes a delivery assembly for delivering the ablation member to the location. The circumferential ablation member is generally adjustable between different configurations to allow both the delivery through a delivery sheath into the atrium and the ablative coupling between the ablation element and the circumferential region of tissue.
1. A tissue ablation system for treating atrial arrhythmia by ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium, comprising:
a delivery member with a proximal end portion and a distal end portion having a longitudinal axis and a radial axis; and
a circumferential ablation member coupled to the distal end portion and having a plurality of cantilevered splines, each with a proximal end portion and a distal end portion, and also having one or more ablation elements each supported along a support region of one of the splines, wherein the plurality of splines are circumferentially spaced around the longitudinal axis, each of the splines being adjustable between a first condition and a second condition wherein the respectively supported ablation element is adjustable between a first radial position and a second radial position,
wherein each spline in the first condition is substantially radially collapsed and extends substantially along the longitudinal axis such that the circumferential ablation member is adapted to be delivered through a delivery sheath into the atrium, and in the second condition the support region of each spline extends at least in part radially away from the longitudinal axis such that each of the individual ablation elements is held by the supporting spline in the second radial position with the one or more ablation elements being spaced along a circumferential pattern that surrounds the longitudinal axis, said circumferential pattern being configured such that the one or more ablation elements is adapted to engage and ablate the circumferential region of tissue when the splines are adjusted to the second condition at the location.
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17. A tissue ablation system for ablating a circumferential region of tissue comprising:
a delivery member with a proximal end portion and a distal end portion having a longitudinal axis and a radial axis; and
a circumferential ablation member coupled to the distal end portion and having a plurality of cantilevered splines, each with a proximal end portion and a distal end portion, and also having one or more ablation elements each supported along a support region of one of the splines, wherein the plurality of splines are circumferentially spaced around the longitudinal axis, each of the splines being adjustable between a first condition and a second condition wherein the respectively supported ablation element is adjustable between a first radial position and a second radial position.
18. A circumferential ablation member comprising:
A plurality of cantilevered splines circumferentially spaced around a longitudinal axis, each of the splines being adjustable between a first condition and a second condition;
and one or more ablation elements each supported along a support region of one of the splines, wherein the respectively supported ablation element is adjustable between a first radial position and a second radial position when the supporting spline is adjusted between the first condition and the second condition.
This application is a continuation of U.S. patent application Ser. No. 10/274,729 filed on Oct. 21, 2002, to which this application claims priority under 35 U.S.C. §120. Application Ser. No. 10/274,729 is a divisional of U.S. patent application Ser. No. 09/435,281 filed on Nov. 5, 1999, and claims priority thereto under 35 U.S.C. § 121. U.S. application Ser. No. 09/435,281 is a continuation-in-part of U.S. patent application Ser. No. 08/889,798 filed on Jul. 8, 1997, now U.S. Pat. No. 6,024,740; and Ser. No. 09/199,736 filed on Nov. 25, 1998, now U.S. Pat. No. 6,117,101. This application also claims priority pursuant to 35 U.S.C. § 119 (e) to provisional application 60/133,677 filed on May 11, 1999.
1. Field of the Invention
The present invention relates to a surgical device and method. More specifically, it is a device assembly and method adapted to form a circumferential conduction block along a circumferential region of tissue along a posterior left atrial wall and surrounding a pulmonary vein.
2. Description of the Related Art
Many abnormal medical conditions in humans and other mammals have been associated with disease and other aberrations along the walls that define several different body spaces. In order to treat such abnormal wall conditions of the body spaces, medical device technologies adapted for delivering specific forms of ablative energy to specific regions of targeted wall tissue from within the associated body space have been developed and disclosed.
Cardiac arrhythmias, and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population. In patients with normal sinus rhythm, the heart, which is comprised of atrial, ventricular, and excitatory conduction tissue, is electrically excited to beat in a synchronous, patterned fashion. In patients with cardiac arrhythmia, abnormal regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue in patients with sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct to adjacent tissue, thereby disrupting the cardiac cycle into an asynchronous cardiac rhythm. Such abnormal conduction has been previously known to occur at various regions of the heart, such as, for example, in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers.
Cardiac arrhythmias, including atrial arrhythmia, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self-propagating. In the alternative or in addition to the multiwavelet reentrant type, cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. These foci may act as either a trigger of paroxysmal atrial fibrillation or may sustain the fibrillation. Recent studies have suggested that focal arrhythmia often originates from a tissue region along the pulmonary veins of the left atrium, and even more particularly in the superior pulmonary veins.
Percutaneous catheter ablation techniques have been disclosed which use end-electrode catheter designs with the intention of ablating and thereby treating focal arrhythmias in the pulmonary veins. These ablation procedures are typically characterized by the incremental application of electrical energy to the tissue to form focal lesions designed to ablate the focus and thereby interrupt the inappropriate conduction pathways.
One example of a focal ablation method intended to destroy and thereby treat focal arrhythmia originating from a pulmonary vein is disclosed by Haissaguerre, et al. in “Right And Left Atrial Radiofrequency Catheter Therapy Of Paroxysmal Atrial Fibrillation” in Journal of Cardiovascular Electrophysiology 7 (12), pp. 1132-1144 (1996). Haissaguerre, et al. discloses 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.
In another focal ablation example, Jais et al. in “A Focal Source Of Atrial Fibrillation Treated By Discrete Radiofrequency Ablation” Circulation 95: 572-576 (1997), applies an ablative technique to patients with paroxysmal arrhythmias originating from a focal source. 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.
There is a need, however, for a circumferential ablation device assembly and method adapted to electrically isolate a substantial portion of a posterior left atrial wall from an arrhythmogenic focus along a pulmonary vein. In particular there is still a need for such an assembly and method which provides a circumferential ablation member secured to the distal end of an elongate catheter body and which includes an ablation element adapted to form a circumferential conduction block along a circumferential region of tissue which either includes the arrhythmogenic focus or is between the arrhythmogenic focus and a substantial portion of the posterior left atrium wall.
This invention is a tissue ablation system and method that treats atrial arrhythmia by ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. In general, the system includes a circumferential ablation member with an ablation element that ablates the tissue at the location, and also includes a delivery assembly for delivering the ablation member to the location. The circumferential ablation member is generally adjustable between different configurations to allow for in one configuration the delivery through a delivery sheath into the atrium, and in another configuration the ablative coupling between the ablation element and the circumferential region of tissue at the location.
According to one mode of the tissue ablation system, the circumferential ablation member is adjustable to a position wherein a circumferential wall has a distal facing surface that surrounds the longitudinal axis of a cooperating delivery member. The ablation element ablatively couples to a circumferential area that is normal to the distal facing surface. The distal facing surface is configured such that the circumferential area coincides with the circumferential region of tissue when the wall is adjusted to the second position at the location, and therefore the ablatively coupled ablation element is adapted to ablate the circumferential region of tissue there.
According to another mode of the invention, a circumferential ablation member has a circumferential support member that is adjustable between a first position that is adapted to be delivered through a delivery sheath into the atrium and a second position having a substantially circumferentially looped shape. An ablation element is located substantially along the circumferential support member and is adapted to ablatively couple to a circumferential area adjacent to the support member in the second position. The looped shape of the circumferential support member is configured such that the circumferential area coincides with the circumferential region of tissue when the circumferential support member is adjusted to the second position at the location. A positioning assembly that is coupled to the circumferential support member such that the circumferential support member may be adjusted between the first and second positions when the circumferential support member is substantially radially unconfined within the atrium. In addition, a delivery assembly cooperates with the circumferential ablation member and is adapted to at least in-part deliver the circumferential ablation member to the location.
In one aspect of this mode, the circumferential support member has an elongate body that extends distally from a delivery member and is sufficiently straight in the first position to fit within a delivery sheath. The elongate body is reconfigured into the looped shape for ablation when the circumferential support member is adjusted to the second position.
In one variation of the system according to this aspect, the delivery member has a passageway extending between a distal port adjacent the proximal end of the elongate body and a proximal port located along the proximal end portion of the delivery member. The positioning assembly adjusts the position of the ablation member by use of a pull-wire that is moveably engaged within the passageway such that the proximal end portion of the pull-wire extends proximally through the proximal port, and the distal end portion of the pull-wire extends distally through the distal port where the pull-wire is secured to the distal end of the elongate body. In the first position the first and second ends of the elongate body are spaced along the pull-wire with the intermediate region of the elongate body extending along the longitudinal axis adjacent to the pull-wire. The circumferential support member is adjustable to the second position at least in part by adjusting the relative position of the pull-wire with respect to its moveable engagement within the passageway of the delivery member such that the proximal and distal ends of the elongate body are longitudinally collapsed toward each other. Such longitudinal repositioning of the ends of the elongate body cause the intermediate region to deflect radially into the desired looped shape.
According to a further feature of this variation, at least one indicator which indicates when the circumferential ablation member is in the second position, such as in one further variation by use of first and second radiopaque markers on the opposite ends of the elongate body, or by use of visible indicators on the proximal aspects that indicate the relative positioning of the pull-wire versus the delivery member.
In another aspect of this mode, the circumferential support member comprises an elongate body with a distal end secured to the distal end portion of the first delivery member and a proximal end secured to the distal end portion of the second delivery member. The positioning assembly comprises an outer member with a proximal end portion and a distal end portion that surrounds the distal end portions of the first and second delivery members and that has a longitudinal axis. The distal end portion of at least one of the delivery members is moveable along the outer member, such that in the first position the elongate body extends distally from the first delivery member substantially along the longitudinal axis, and in the second position the delivery members are longitudinally adjusted relative to each other and also relative to the outer member such that the elongate body is positioned externally of the distal end portion of the outer member with the elongate body adjusted into the substantially circumferentially looped shape.
According to various of the modes and more particular aspects herein summarized, one further variation provides an anchor along a distal end portion of a delivery member associated with the system and which is adapted to secure the delivery member within the pulmonary vein while the circumferential ablation member is being ablatively coupled to the circumferential region of tissue. In one more detailed example the anchor includes an expandable member that radially expands to engage the pulmonary vein in order to secure the delivery member in place during ablation.
In another aspect of this mode, the positioning assembly includes an array of circumferentially spaced splines that are positioned around the longitudinal axis. Each spline has a proximal end portion coupled to the distal end portion of the delivery member and a distal end portion coupled to the circumferential support member. Each spline is adjustable between a first configuration, wherein the distal end portion of the spline extends substantially along the longitudinal axis, and a second configuration, wherein the distal end portion of the spline extends radially away from the longitudinal axis. The first position for the circumferential support member according to this aspect is characterized at least in part by each of the splines being adjusted to the first configuration. The respective second position is characterized at least in part by each spline being adjusted to the second configuration.
According to one variation of the spline aspect of this mode, each spline provides a single elongate member that terminates distally where it is secured to the circumferential support member. In another variation, each spline provides a looped member having an apex along the distal end portion of the spline and two legs extending proximally from the apex along the proximal end portion of the spline. Further to this latter variation, the circumferential support member is threaded through the apexes of the circumferentially spaced splines. Moreover, according to a further feature at least one of the splines is used to help couple the ablation element to the ablation actuator, such as by allowing an ablation actuating member to extend along the spline to an energy source of the ablation element, and more specifically by providing fluid coupling along a passageway along the spline in the case of a fluid ablation element, or electrical coupling of electrical conductor leads along the spline passageway in the case of an electrical ablation element.
In another spline variations: the ablation element has a plurality of individual ablation elements, each extending along the circumferential support member between two adjacent splines; or, the splines comprises a material having a memory to the second configuration, such as by means of a shape memory material such as a nickel titanium alloy.
Further to other aspects of this mode, the ablation element may be one or more specific types of ablation elements, such as fluid, electrical, cryo, microwave, thermal, light-emitting, or ultrasound ablation elements.
In one specific variation incorporating the electrical ablation aspect of this mode, at least one electrode is provided along the circumferential support member that is adapted to be coupled to an electrical current source. A porous wall substantially surrounds the electrode within an enclosed fluid chamber that is adapted to be fluidly coupled to a source of electrically conductive fluid. The porous wall is further adapted to electrically couple an ablative electrical current between the circumferential region of tissue positioned coincident to the circumferential area and the electrode via the electrically conductive fluid.
According to another mode of the invention, a circumferential ablation member includes a housing, a mechanical positioning assembly that adjusts the housing between certain specific first and second conditions, and an ablation element also cooperating with the housing to ablate the circumferential region of tissue. Further to this mode, the housing is mechanically adjustable between a first condition and a second condition. In the first condition the distal wall is substantially radially collapsed such that the housing is adapted to be delivered through a delivery sheath into the atrium. In the second condition the distal wall is radially extended at least in part from the longitudinal axis with a distal orientation and a distal facing surface located along a circumferential region that surrounds the longitudinal axis. A mechanical positioning assembly is coupled to the housing to mechanically adjust the housing between the first and second conditions. An ablation element cooperates with the housing and is adapted to ablatively couple to a circumferential area normal to the distal facing surface along the circumferential region when the housing is in the second position. The distal facing surface is configured such that the circumferential area coincides with the circumferential region of tissue when the housing is adjusted to the second condition at the location, and therefore the ablation element is adapted to ablate the circumferential region of tissue in that position.
In one beneficial aspect of this mode, the distal wall in the second condition comprises a porous membrane that encloses at least in part a fluid chamber within the housing. The distal facing surface is located along the porous membrane, and the porous membrane is adapted to ablatively couple a volume of ablative fluid within the fluid chamber to the circumferential area. In one further regard, the porous membrane is adapted to allow the volume of ablative fluid to flow from within the fluid chamber and into the circumferential area. Still further, the ablation element may comprise a volume of ablative fluid medium within the fluid chamber and that ablatively couples with the circumferential area across the porous membrane. In a still further variation, the porous membrane is constructed at least in part from a porous tetrafluoropolymer. In another variation, the ablation element includes an ablative energy source located within the fluid chamber.
In another more detailed aspect of this mode, the housing has an outer jacket with a distal end portion and a proximal end portion, the distal wall is located along the distal end portion, and a proximal wall is located along the proximal end portion. The mechanical positioning assembly comprises an array of longitudinal splines that are circumferentially spaced around the longitudinal axis, wherein each of the longitudinal splines has a distal end portion and a proximal end portion and an intermediate region therebetween. The distal and proximal end portions of the outer jacket are positioned to surround at least a part of the proximal and distal end portions of the splines, respectively. According to this relationship, in the first condition the proximal and distal end portions of each spline are respectively spaced along the longitudinal axis with the intermediate region being substantially radially collapsed within the outer jacket. The housing is adjusted to the second condition by longitudinally collapsing the relative position of the proximal and distal end portions of each spline such that the intermediate region of each spline and outer jacket adjacent thereto deflects radially outwardly from the longitudinal axis such that distal and proximal orientations, respectively, are given to the distal and proximal walls. In one variation of this aspect, the outer jacket comprises an elastomeric material.
In another aspect of this mode the housing also has a proximal wall that in the second condition has a proximally facing surface. The proximal wall according to this aspect is connected to the distal wall, such as in a still further variation by being formed from an integral member. In a still more detailed variation however, the distal and proximal walls are connected along at least one of (a) an outer circumferential region that circumscribes the circumferential region that includes the distal facing surface, or (b) an inner circumferential region that is circumscribed by the circumferential region that includes the distal facing surface. In yet another variation, the mechanical positioning assembly provides at least one support member extending between the distal and proximal walls at least across an inner circumferential region, which is circumscribed by the circumferential region that includes the distal facing surface, and the circumferential region with that distal facing surface.
According to another aspect of the mechanically adjustable ablative housing mode, the mechanical positioning assembly is coupled to the delivery member.
In another more detailed aspect of this mode, the mechanical positioning assembly comprises an array of splines that are circumferentially spaced around the longitudinal axis of the delivery member. Each spline has a distal end portion coupled to the distally oriented wall and a proximal end portion coupled to the distal end portion of the delivery member. Also, each spline is adjustable between a first position that is substantially radially collapsed and extending along the longitudinal axis and a second position wherein the distal end portion of the spline extends radially outwardly from the longitudinal axis. Accordingly, the first and second positions for the splines characterize at least in part the first and second conditions for the housing.
Further to this aspect, in one variation the ablation element comprises an energy source that is located along a spline at a position corresponding to the circumferential region.
According to another mode of the invention, a circumferential ablation member coupled to the distal end portion of a delivery member includes an array of splines supporting an array of individual ablation elements with each ablation element being supported along a support region of one of the splines. The splines are circumferentially spaced around the longitudinal axis. Each spline is adjustable between a first condition and a second condition, wherein the respectively supported individual ablation element is adjustable between a first radial position and a second radial position. Further to this assembly, each spline is substantially radially collapsed and extends substantially along the longitudinal axis in the first condition such that the circumferential ablation member is adapted to be delivered through a delivery sheath into the atrium. In the second condition, the support region of each spline extends at least in part radially away from the longitudinal axis. Each of the individual ablation elements is thus held by the supporting spline in the second radial position with the array of individual ablation elements being spaced along a circumferential pattern that surrounds the longitudinal axis. This circumferential pattern is specifically configured such that the array of individual ablation elements is adapted to engage and ablate the circumferential region of tissue when the splines are adjusted to the second condition at the location.
In one aspect of this mode, each of the splines has a memory to the second condition, such as by being constructed from a shape-memory material that more specifically may be a nickel-titanium alloy.
In another aspect, an outer member surrounds the distal end portion of the delivery member. The splines are adapted to be moved in and out of the outer member in order to adjust their shape between the first and second positions.
According to additional aspects of this mode, the distal end portion of each of the splines in the second position may have a radius of curvature either away from the longitudinal axis, or in another aspect the radius of curvature may be toward the longitudinal axis.
According to still further aspects of this mode, the ablation element may be one of a number of different types, including one or more of the following: an electrical current ablation element; a thermal ablation element; an ultrasound ablation element; a microwave ablation element; a thermal ablation element; a cryoablation element; a fluid ablation element; or a light emitting ablation element.
In another mode, the invention provides a contact member in combination with a distally oriented ablation element, both being coupled to a delivery member. The contact member is adjustable between a first condition for delivery through a delivery sheath into the atrium and a second condition for circumferential ablation wherein the contact member comprises a circumferential wall that surrounds the longitudinal axis. The ablation element has an ablative energy source that is located along the distal end portion of the delivery member, and cooperates with the contact member such that the ablative energy source emits a circumferential pattern of energy having a distal orientation through the circumferential wall and into a circumferential area normal to the circumferential wall. Electrical current is not ablatively coupled between the ablative energy source and the circumferential area according to this mode. The ablation element and contact member are configured such that the circumferential area coincides with the circumferential region of tissue when the contact member is adjusted to the second condition at the location.
In one aspect of this mode, the contact member is an inflatable balloon and the ablation element cooperates with the circumferential area as described above through the balloon's outer skin.
According to still further aspects of this mode, the ablation element may be one of a number of different types, including one or more of the following: an electrical current ablation element; a thermal ablation element; an ultrasound ablation element; a microwave ablation element; a thermal ablation element; a cryoablation element; a fluid ablation element; or a light emitting ablation element.
In one variation of the ultrasound ablation element aspect, an ultrasound transducer assembly is mounted onto the distal end portion with a distally oriented face that is adapted to emit an ultrasonic energy signal distally at an angle relative to the longitudinal axis and through the circumferential wall of the contact member. In still a further more detailed variation, the transducer is conically shaped with an outer conical surface having a distal orientation. In another detailed variation the transducer has a curved distal face.
In still a further detailed variation, the ultrasound transducer assembly has at least one ultrasound transducer panel that is adjustable from a radially collapsed position to a radially extended position having a distally oriented face that is adapted to emit the circumferential pattern of energy with the distal orientation. Further to this transducer panel variation, the transducer panel may be adjustable as described by use of an expandable member located between the panel and the distal end portion of the delivery member, which expandable member may be a balloon structure or a cage structure.
Other modes, aspects, variations, and features of the invention shall become apparent to one of ordinary skill upon review of this application, and in particular by reference to the detailed disclosure of the invention which follows below.
FIGS. 2A-E show schematic, perspective views of various exemplary circumferential conduction blocks formed at a location where a pulmonary vein extends from an atrium with a circumferential ablation device assembly.
FIGS. 8A-B show perspective views of another circumferential ablation catheter during use in a left atrium according to the method of
FIGS. 11A-B show perspective views of one circumferential ablation member for use in a circumferential ablation device assembly, showing a circumferential ablation electrode circumscribing the working length of an expandable member with a secondary shape along the longitudinal axis of the working length which is a modified step shape, the expandable member being shown in a radially collapsed position and also in a radially expanded position, respectively.
FIGS. 11C-D show perspective views of two circumferential ablation electrodes which form equatorial or otherwise circumferentially placed bands that circumscribe the working length of an expandable member and that have serpentine and sawtooth secondary shapes, respectively, relative to the longitudinal axis of the expandable member when adjusted to a radially expanded position.
FIGS. 12A-B show perspective views of another circumferential ablation element which includes a plurality of individual ablation electrodes that are spaced circumferentially to form an equatorial band which circumscribes the working length of an expandable member either in an equatorial location or an otherwise circumferential location that is bounded both proximally and distally by the working length, and which are adapted to form a continuous circumferential lesion while the working length is adjusted to a radially expanded position.
FIGS. 23A-D show various transverse cross-sectional views of various particular embodiments for engaging the spline members within a delivery sheath such as for use according to the assemblies shown in
FIGS. 25A-B show a perspective schematic views of another circumferential ablation device assembly having a plurality of spline members that are rotatably engaged in first and second positions, respectively, relative to a circumferential ablation element according to the invention.
FIGS. 38A-B respectively show various actuating members for adjusting the ultrasound transducer panels such as those shown in FIGS. 37A-C to a radially extended position relative to an interior support shaft which is adapted to ablate a circumferential region of tissue according to
The terms “body space,” including derivatives thereof, is herein intended to mean any cavity or lumen within the body that is defined at least in part by a tissue wall. For example, the cardiac chambers, the uterus, the regions of the gastrointestinal tract, and the arterial or venous vessels are all considered illustrative examples of body spaces within the intended meaning.
The term “lumen,” including derivatives thereof, is herein intended to mean any body space which is circumscribed along a length by a tubular tissue wall and which terminates at each of two ends in at least one opening that communicates externally of the body space. For example, the large and small intestines, the vas deferens, the trachea, and the fallopian tubes are all illustrative examples of lumens within the intended meaning. Blood vessels are also herein considered lumens, including regions of the vascular tree between their branch points. More particularly, the pulmonary veins are lumens within the intended meaning, including the region of the pulmonary veins between the branched portions of their ostia along a left ventricle wall, although the wall tissue defining the ostia typically presents uniquely tapered lumenal shapes.
The following disclosure referring to
The terms “circumference” or “circumferential”, including derivatives thereof, are herein intended to mean a continuous path or line that forms an outer border or perimeter that surrounds and thereby defines an enclosed region of space. Such a continuous path starts at one location along the outer border or perimeter, and translates along the outer border or perimeter until it is completed at the original starting location to enclose the defined region of space. The related term “circumscribe,” including derivatives thereof, is herein intended to mean to enclose, surround, or encompass a defined region of space. Therefore, according to these defined terms, a continuous line which is traced around a region of space and which starts and ends at the same location “circumscribes” the region of space and has a “circumference” which is defined by the distance the line travels as it translates along the path circumscribing the space.
Still further, a circumferential path or element may include one or more of several shapes, and may be, for example, circular, oblong, ovular, elliptical, or otherwise planar enclosures. A circumferential path may also be three dimensional, such as, for example, two opposite-facing semi-circular paths in two different parallel or off-axis planes that are connected at their ends by line segments bridging between the planes.
For purpose of further illustration, FIGS. 2A-D therefore show various circumferential paths A, B, C, and D, respectively, each translating along a portion of a pulmonary vein wall and circumscribing a defined region of space, shown at a, b, c, and d also respectively, each circumscribed region of space being a portion of a pulmonary vein lumen. For still further illustration of the three-dimensional circumferential case shown in
The term “transect”, including derivatives thereof, is also herein intended to mean to divide or separate a region of space into isolated regions. Thus, each of the regions circumscribed by the circumferential paths shown in FIGS. 2A-D transects the respective pulmonary vein, including its lumen and its wall, to the extent that the respective pulmonary vein is divided into a first longitudinal region located on one side of the transecting region, shown, for example, at region “X” in
Therefore, a “circumferential conduction block” according to the present invention is formed along a region of tissue that follows a circumferential path along the pulmonary vein wall, circumscribing the pulmonary vein lumen and transecting the pulmonary vein relative to electrical conduction along its longitudinal axis. The transecting circumferential conduction block therefore isolates electrical conduction between opposite longitudinal portions of the pulmonary wall relative to the conduction block and along the longitudinal axis.
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: an electrode element adapted to couple to a direct current (“DC”) or alternating current (“AC”) current source, such as 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 beat such as by convective or conductive heat transfer, by resistive heating due to current flow, or by optical heating with light; a light emitting element, such as a fiber optic element which transmits light sufficient to ablate tissue when coupled to a light source; 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.
In addition, other elements for altering the nature of tissue may be suitable as “ablation elements” under the present invention when adapted according to the detailed description of the invention below. For example, a cryoablation element adapted to sufficiently cool tissue to substantially alter the structure thereof may be suitable if adapted according to the teachings of the current invention. Furthermore, a fluid delivery element, such as a discrete port or a plurality of ports that are fluidly coupled to a fluid delivery source, may be adapted to infuse an ablating fluid, such as a fluid containing alcohol, into the tissue adjacent to the port or ports to substantially alter the nature of that tissue.
The term “anchor” is herein intended to broadly encompass any structure that functions to secure at least a portion of the disclosed ablation device assemblies to a pulmonary vein or pulmonary vein ostium, such that the circumferential and/or linear ablation elements are positioned sufficiently close to posterior wall of the left atrium to ablatively engage the targeted tissue. Examples of suitable anchors within the scope of the present disclosure include, conventional guidewires, guidewires with balloons, deflectable/steerable guidewires, shaped stylets, radially expandable members, inflatable members, etc.
The term “diagnose”, including derivatives thereof, is intended to include patients suspected or predicted to have atrial arrhythmia, in addition to those having specific symptoms or mapped electrical conduction indicative of atrial arrhythmia.
Returning to the inventive method as shown in
In another aspect of the method of
In still a further aspect of the method shown in
Further to positioning step (3) according to the method of
Once in the right atrium, the distal tip of the guiding catheter is positioned against the fossa ovalis in the intraatrial septal wall. A “Brockenbrough” needle or trocar is then advanced distally through the guide catheter until it punctures the fossa ovalis. A separate dilator may also be advanced with the needle through the fossa ovalis to prepare an access port through the septum for seating the guiding catheter. The guiding catheter thereafter 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 however further contemplated that other left atrial access methods may be suitable substitutes for using the circumferential ablation device assembly of the present invention. In one alternative variation not shown, a “retrograde” approach may be used, wherein the 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, for example, at a femoral artery. The guiding catheter is advanced retrogradedly through the aorta, around the aortic arch, into the ventricle, and then into the left atrium through the mitral valve.
Subsequent to gaining transeptal access to the left atrium as just described, positioning step (3) according to
Suitable guidewire designs for use in the overall circumferential ablation device assembly of the present invention may be selected from previously known designs, while generally any suitable choice should include a shaped, radiopaque distal end portion with a relatively stiff, torquable proximal portion adapted to steer the shaped tip under X-ray visualization. Guidewires having an outer diameter ranging from 0.010 inch to 0.035 inch may be suitable. In cases where the guidewire is used to bridge the atrium from the guiding catheter at the fossa ovalis, and where no other sub-selective guiding catheters are used, guidewires having an outer diameter ranging from 0.018 inch to 0.035 inch may be required. It is believed that guidewires within this size range may be required to provide sufficient stiffness and maneuverability in order to allow for guidewire control and to prevent undesirable guidewire prolapsing within the relatively open atrial cavity.
Subsequent to gaining pulmonary vein access, positioning step (3) of
As would be apparent to one of ordinary skill, the distal guidewire tracking member shown in
In addition, the inclusion of a guidewire lumen extending within the elongate catheter body between first and second ports, as provided in
While the assemblies and methods shown variously throughout the FIGS. include a guidewire coupled to a guidewire tracking member on the circumferential ablation catheter, other detailed variations may also be suitable for positioning the circumferential ablation element at the ablation region in order to form a circumferential conduction block there. For example, an alternative circumferential ablation catheter not shown may include a “fixed-wire”-type of design wherein a guidewire is integrated into the ablation catheter as one unit. In another alternative assembly, the same type of sub-selective sheaths described above with reference to U.S. Pat. No. 5,575,766 to Swartz for advancing a guidewire into a pulmonary vein may also be used for advancing a circumferential ablation catheter device across the atrium and into a pulmonary vein.
Circumferential ablation member 150 also includes a circumferential band (hatched) on the outer surface of working length L that is coupled to an ablation actuator 190 at a proximal end portion of the elongate catheter body (shown schematically). After expandable member 170 is adjusted to the radially expanded position and at least a portion of working length L circumferentially engages the pulmonary vein wall in the ablation region, the circumferential band of the circumferential ablation member 150 is actuated by ablation actuator 190 to ablate the surrounding circumferential path of tissue in the pulmonary vein wall, thereby forming a circumferential lesion that circumscribes the pulmonary vein lumen and transects the electrical conductivity of the pulmonary vein to block conduction in a direction along its longitudinal axis.
Further to the perfusion design shown in FIGS. 6A-B, guidewire 102 is positioned in a guidewire lumen which extends the entire length of the elongate catheter body 230 in an “over-the-wire”-type of design, which facilitates the proximal withdrawal of the guidewire to allow for perfusion while maintaining the ability to subsequently re-advance the guidewire distally through the first distal guidewire port 242 for catheter repositioning. In one alternative variation not shown, the guidewire is simply withdrawn and disengaged from the second distal guidewire port, in which case the circumferential ablation catheter must generally be withdrawn from the body in order to re-couple the distal guidewire tracking member with the guidewire.
In another alternative perfusion variation not shown which is a modification of the embodiment of
Passive perfusion during expansion of the expandable member is believed to minimize stasis and allow the target pulmonary vein to continue in its atrial filling function during the atrial arrhythmia treatment procedure. In addition, in cases where the ablation element is adapted to ablate tissue with heat conduction at the ablation region, as described by reference to more detailed embodiments below, the perfusion feature according to the variation of FIGS. 6A-B may also provide a cooling function in the surrounding region, including in the blood adjacent to the expandable member.
Moreover, in addition to the specific perfusion structure shown and described by reference to FIGS. 6A-B, it is to be further understood that other structural variants which allow for perfusion flow during expansion of the expandable element may provide suitable substitutes according to one of ordinary skill without departing from the scope of the present invention.
It is believed, however, that circumferential catheter ablation with a circumferential ablation element according to the present invention may leave some tissue, either transmurally or along the circumference of the lesion, which is not actually ablated, but which is not substantial enough to allow for the passage of conductive signals. Therefore, the terms “transmural” and “continuous” as just defined are intended to have functional limitations, wherein some tissue in the ablation region may be unablated but there are no functional gaps which allow for symptomatically arrhythmogenic signals to conduct through the conduction block and into the atrium from the pulmonary vein.
Moreover, it is believed that the functionally transmural and continuous lesion qualities just described are characteristic of a completed circumferential conduction block in the pulmonary vein. Such a circumferential conduction block thereby transects the vein, isolating conduction between the portion of the vein on one longitudinal side of the lesion and the portion on the other side. Therefore, any foci of originating arrhythmogenic conduction which is opposite the conduction block from the atrium is prevented by the conduction block from conducting down into the atrium and atrial arrhythmic affects are therefore nullified.
FIGS. 8A-B show a further variation of the present invention, wherein a circumferential ablation member 350 includes a radially compliant expandable member 370 which is adapted to conform to a pulmonary vein ostium 54 at least in part by adjusting it to a radially expanded position while in the left atrium and then advancing it into the ostium. A circumferential ablation element 352 forms a band around expandable member 370, and is coupled to ablation actuator 190.
In addition to conforming to the pulmonary vein ostium, the proximal portion 372 of expandable member is also shown in
FIGS. 8D-E show another highly beneficial circumferential ablation device embodiment and use-thereof for electrically isolating pulmonary vein and ostium from a substantial portion of the left posterior atrial wall. However, unlike the embodiment previously shown and described by reference to FIGS. 8A-C, the
In more detail,
In another variation, a “pear-shaped” expandable member or balloon that includes a contoured taper may be suitable for use according to the
The method of forming a circumferential conduction block along a circumferential path of tissue along a left posterior atrial wall and which surrounds a pulmonary vein ostium without ablating the tissue of the vein or ostium should not be limited to the particular device embodiments just illustrated by reference to FIGS. 8D-F. Other device variations may be acceptable substitute for use according to this method. In one particular example which is believed to be suitable, a “looped” ablation member such as the embodiment illustrated below by reference to
FIGS. 9A-D collectively show a circumferential ablation device assembly according to the present invention as it is used to form a circumferential conduction block adjunctively to the formation of long linear lesions in a less-invasive “maze”-type procedure, as introduced above for the treatment of multiwavelet reentrant type fibrillation along the left atrial wall.
In a further variation to the specific embodiments shown in FIGS. 9B-C,
A shaped stylet 466 is shown in shadow in
Moreover, the method shown schematically in
In addition to the particular embodiments just shown and described by reference to FIGS. 9A-E, other methods are also contemplated for combining circumferential and linear conduction blocks device assemblies and uses in order to perform a less-invasive “maze”-type procedure. For example,
To this end, the invention further contemplates one further variation for a less-invasive “maze”-type procedure (not shown) wherein multiple circumferential conduction blocks are formed in atrial wall tissue such that each pulmonary vein ostium is surrounded by and is electrically isolated with one circumferential conduction block. A series of four linear lesions may be formed between the various pairs of adjacent ostia and with just sufficient length to intersect with and bridge the corresponding adjacent circumferential blocks. A box-like conduction block is thereby formed by the four circumferential conduction blocks and the four bridging linear lesions. A fifth linear lesion may be also formed between at least a portion of the box-like conduction block and another predetermined location, such as for example the mitral value annulus.
In addition or in the alternative to monitoring electrical conduction signals in the pulmonary vein prior to ablation, electrical signals along the pulmonary vein wall may also be monitored by the sensing element subsequent to circumferential ablation, according to step (9) of the method of
A test electrode may also be used in a “post ablation” signal monitoring method according to step (10) of
Further to the signal monitoring and test stimulus methods just described, such methods may be performed with a separate electrode or electrode pair located on the catheter distal end portion adjacent to the region of the circumferential ablation element, or may be performed using one or more electrodes which form the circumferential ablation element itself, as will be further developed below.
The designs for the expandable member and circumferential ablation element for use in a circumferential ablation device assembly as herein described have been described generically with reference to the embodiments shown in the previous FIGS. Examples of various specific expandable member and ablation element structures that are adapted for use in such assemblies and methods are further provided as follows.
Notwithstanding their somewhat schematic detail, the circumferential ablation members shown in the previous FIGS. do illustrate one particular embodiment wherein a circumferential electrode element circumscribes an outer surface of an expandable member. The expandable member of the embodiments shown may take one of several different forms, although the expandable member is generally herein shown as an inflatable balloon that is coupled to an expansion actuator which is a pressurizeable fluid source. The balloon is preferably made of a polymeric material and forms a fluid chamber that communicates with a fluid passageway (not shown in the FIGS.) that extends proximally along the elongate catheter body and terminates proximally in a proximal fluid port that is adapted to couple to the pressurizeable fluid source.
In one expandable balloon variation, the balloon is constructed of a relatively inelastic polymer such as a polyethylene (“PE”; preferably linear low density or high density or blends thereof), polyolefin copolymer (“POC”), polyethylene terepthalate (“PET”), polyimide, or a nylon material. In this construction, the balloon has a low radial yield or compliance over a working range of pressures and may be folded into a predetermined configuration when deflated in order to facilitate introduction of the balloon into the desired ablation location via known percutaneous catheterization techniques. In this variation, one balloon size may not suitably engage all pulmonary vein walls for performing the circumferential ablation methods of the present invention on all needy patients. Therefore, it is further contemplated that a kit of multiple ablation catheters, with each balloon working length having a unique predetermined expanded diameter, may be provided from which a treating physician may chose a particular device to meet a particular patient's pulmonary vein anatomy.
In an alternative expandable balloon variation, the balloon is constructed of a relatively compliant, elastomeric material, such as, for example (but not limited to), a silicone, latex, polyurethane, or mylar elastomer. In this construction, the balloon takes the form of a tubular member in the deflated, non-expanded state. When the elastic tubular balloon is pressurized with fluid such as in the previous, relatively non-compliant example, the material forming the wall of the tubular member elastically deforms and stretches radially to a predetermined diameter for a given inflation pressure. It is further contemplated that the compliant balloon may be constructed as a composite, such as, for example, a latex or silicone balloon skin which includes fibers, such as metal, Kevlar, or nylon fibers, which are embedded into the skin. Such fibers, when provided in a predetermined pattern such as a mesh or braid, may provide a controlled compliance along a preferred axis, preferably limiting longitudinal compliance of the expandable member while allowing for radial compliance.
It is believed that, among other features, the relatively compliant variation may provide a wide range of working diameters, which may allow for a wide variety of patients, or of vessels within a single patient, to be treated with just one or a few devices. Furthermore, this range of diameters is achievable over a relatively low range of pressures, which is believed to diminish a potentially traumatic vessel response that may otherwise be presented concomitant with inflation at higher pressures, particularly when the inflated balloon is oversized to the vessel. In addition, the low-pressure inflation feature of this variation is suitable for the present invention because the functional requirement of the expandable balloon is merely to engage the ablation element against a circumferential path along the inner lining of the pulmonary vein wall.
Moreover, a circumferential ablation member is adapted to conform to the geometry of the pulmonary vein ostium, at least in part by providing substantial compliance to the expandable member, as was shown and described previously by reference to FIGS. 8A-B. Further to this conformability to pulmonary vein ostia as provided in the specific design of FIGS. 8A-B, the working length L of expandable member is also shown to include a taper which has a distally reducing outer diameter from a proximal end to a distal end. In either a compliant or the non-compliant balloon, such a distally reducing tapered geometry adapts the circumferential ablation element to conform to the funneling geometry of the pulmonary veins in the region of their ostia in order to facilitate the formation of a circumferential conduction block there.
Further to the circumferential electrode element embodiment as shown variously throughout the previous illustrative FIGS., the circumferential electrode element is coupled to an ablation actuator 190. Ablation actuator 190 generally includes a radio-frequency (“RF”) current source (not shown) that is coupled to both the RF electrode element and also a ground patch 195 that is in skin contact with the patient to complete an RF circuit. In addition, ablation actuator 190 preferably includes a monitoring circuit (not shown) and a control circuit (not shown) which together use either the electrical parameters of the RF circuit or tissue parameters such as temperature in a feedback control loop to drive current through the electrode element during ablation. Also, where a plurality of ablation elements or electrodes in one ablation element are used, a switching means may be used to multiplex the RF current source between the various elements or electrodes.
FIGS. 11A-D show various patterns of electrically conductive, circumferential electrode bands as electrode ablation elements, each circumscribing an outer surface of the working length of an expandable member. FIGS. 11A-B show circumferential ablation member 550 to include a continuous circumferential electrode band 552 that circumscribes an outer surface of an expandable member 570.
The shapes shown collectively in FIGS. 11A-D allow for a continuous electrode band to circumscribe an expandable member's working length over a range of expanded diameters, a feature which is believed to be particularly useful with a relatively compliant balloon as the expandable member. In the particular embodiments of FIGS. 11A-D, this feature is provided primarily by a secondary shape given to the electrode band relative to the longitudinal axis of the working length of the expandable member. Electrode band 552 is thus shown in FIGS. 11A-B to take the specific secondary shape of a modified step curve. Other shapes than a modified step curve are also suitable, such as the serpentine or sawtooth secondary shapes shown respectively in FIGS. 11C-D. Other shapes in addition to those shown in FIGS. 11A-D and which meet the defined functional requirements are further contemplated within the scope of the present invention.
In addition, the electrode band provided by the circumferential ablation elements shown in FIGS. 11C-D and also shown schematically in
In another aspect of the narrow equatorial band variation for the circumferential ablation element, the circumferential lesion formed may also be relatively narrow when compared to its own circumference, and may be less than two-thirds or even one-half its own circumference on the expandable element when expanded. In one arrangement, which is believed to be suitable for ablating circumferential lesions in the pulmonary veins as conduction blocks, the band width w is less than 1 cm with a circumference on the working length when expanded that is greater than 1.5 cm.
FIGS. 12A-B show a further variation of a circumferential ablation element which is adapted to maintain a continuous circumferential lesion pattern over a range of expanded diameters and which includes electrode elements that form a relatively narrow equatorial band around the working length of an expandable balloon member. In this variation, a plurality of individual electrode/ablation elements 562 are included in the circumferential ablation element and are positioned in spaced arrangement along an equatorial band which circumscribes an outer surface of the expandable member's working length L.
The size and spacing between these individual electrode elements 562, when the balloon is expanded, is adapted to form a substantially continuous circumferential lesion at a location where a pulmonary vein extends from an atrium when in intimal contact adjacent thereto, and is further adapted to form such a lesion over a range of band diameters as the working length is adjusted between a variety of radially expanded positions. Each individual electrode element 562 has two opposite ends 563,564, respectively, along a long axis LA and also has a short axis SA, and is positioned such that the long axis LA is at an acute angle relative to the longitudinal axis La of the elongate catheter body and expandable member 560. At least one of the ends 563,564 along the long axis LA overlaps with an end of another adjacent individual electrode element, such that there is a region of overlap along their circumferential aspect, i.e., there is a region of overlap along the circumferential coordinates. The terms “region of overlap along their circumferential coordinate” are herein intended to mean that the two adjacent ends each are positioned along the working length with a circumferential and also a longitudinal coordinate, wherein they share a common circumferential coordinate. In this arrangement, the circumferential compliance along the working length, which accompanies radial expansion of the expandable member, also moves the individual electrode elements apart along the circumferential axis. However, the spaced, overlapping arrangement described allows the individual ablation elements to maintain a certain degree of their circumferential overlap, or at least remain close enough together, such that a continuous lesion may be formed without gaps between the elements.
The construction for suitable circumferential electrode elements in the RF variation of the present invention, such as the various electrode embodiments described with reference to
Still further to the RF electrode embodiments, another circumferential ablation member variation (not shown) may also include an expandable member, such as an inflatable balloon, that includes a porous skin that is adapted to allow fluid, such as hypertonic saline solution, to pass from an internal chamber defined by the skin and outwardly into surrounding tissues. Such a porous skin may be constructed according to several different methods, such as by forming holes in an otherwise contiguous polymeric material, including mechanically drilling or using laser energy, or the porous skin may simply be an inherently porous membrane. In any case, by electrically coupling the fluid within the porous balloon skin to an RF current source (preferably monopolar), the porous region of the expandable member serves as an RF electrode wherein RF current flows outwardly through the pores via the conductive fluid. In addition, it is further contemplated that a porous outer skin may be provided externally of another, separate expandable member, such as a separate expandable balloon, wherein the conductive fluid is contained in a region between the porous outer skin and the expandable member contained therein. Various other “fluid electrode” designs than those specifically herein described may also be suitable according to one of ordinary skill upon review of this disclosure.
In the alternative, or in addition to the RF electrode variations just described, the circumferential ablation element may also include other ablative energy sources or sinks, and particularly may include a thermal conductor that circumscribes the outer circumference of the working length of an expandable member. Examples of suitable thermal conductor arrangements include a metallic element that may, for example, be constructed as previously described for the more detailed RF embodiments above. However, in the thermal conductor embodiment such a metallic element would be generally either resistively heated in a closed loop circuit internal to the catheter, or conductively heated by a heat source coupled to the thermal conductor. In the latter case of conductive heating of the thermal conductor with a heat source, the expandable member may be, for example, a polymeric balloon skin that is inflated with a fluid that is heated either by a resistive coil or by bipolar RF current. In any case, it is believed that a thermal conductor on the outer surface of the expandable member is suitable when it is adapted to heat tissue adjacent thereto to a temperature between 40° and 80° C.
Further to the thermal conduction variation for the circumferential ablation element, the perfusion balloon embodiment as shown in FIGS. 6A-B may be particularly useful in such a design. It is believed that ablation through increased temperatures, as provided by example above may also enhance coagulation of blood in the pulmonary vein adjacent to the expandable member, which blood would otherwise remain stagnant without such a perfusion feature.
One further circumferential ablation element design that is believed to be highly useful in performing the methods according to the present invention is shown in
The thermal insulator embodiment just described by reference to
In a further example using the insulator embodiment in combination with a circumferential RF electrode embodiment, a metallized balloon, which includes a conductive balloon skin, may have an electrical insulator, such as a polymeric coating, at each end of the working length and thereby selectively ablate tissue with electricity flowing through the uninsulated equatorial band. In this and other insulator embodiments, it is further contemplated that the insulators described may be only partial and still provide the equatorial band result. For instance, in the conductive RF electrode balloon case, a partial electrical insulator will allow a substantial component of current to flow through the uninsulated portion due to a “shorting” response to the lower resistance in that region.
In still a further example of an insulator combined with a RF ablation electrode, a porous membrane comprises the entire balloon skin of an expandable member. By insulating the proximal and distal end portions of the working length of the expandable member, only the pores in the unexposed equatorial band region are allowed to effuse the electrolyte that carries an ablative RF current.
Further to the expandable member design for use in a circumferential ablation element according to the present invention, other expandable members than a balloon are also considered suitable. For example, in one expandable cage embodiment shown in
The radial expansion of cage 650 is accomplished as follows. Sheath 652 is secured around the wires proximally of cage 650. However, core 653, which may be a metallic mandrel such as stainless steel, extends through sheath 652 and distally within cage 650 wherein it terminates in a distal tip 656. Wires 651 are secured to distal tip 656, for example, by soldering, welding, adhesive bonding, heat shrinking a polymeric member over the wires, or any combination of these methods. Core 653 is slideable within sheath 652, and may, for example, be housed within a tubular lumen (not shown) within sheath 652, the wires being housed between a coaxial space between the tubular lumen and sheath 652. By moving the sheath 652 relative to core 653 and distal tip 656 (shown by arrows in
Further to the particular expandable cage embodiment shown in
Further to the construction of the embodiment shown in
In a further cage embodiment (not shown) to that shown in
Another circumferential ablation element adapted for use in the circumferential conduction block assembly according to the present invention is shown in
Looped member 710 is shown in more detail in
Pusher 730 is further shown in
The embodiments shown and described with reference to
According to the circumferential ablation device assembly 1600 shown in FIGS. 16A-C, a plurality of electrodes 1630 are spaced along elongated member 1625, which is disposed on the distal end portion of catheter body 1610. Elongated member 1625 is adjustable between a first shape (shown in
More specifically, an actuating assembly incorporating pull wire 1667 is used to adjust the elongated member 1625 between shapes. Pull wire 1627 is secured to tip 1626 distally of elongated member 1625 and extends proximally along the side of elongated member 1625 and further through port 1618 where it is slideably engaged within a passageway (not shown) along catheter body 1610, terminating along the proximal end portion of catheter body 1610, where it may be manipulated. Because the distal end 1626 of elongated member 1625 is also secured to tip 1619, pulling pull wire 1627 relative to catheter body 1610 longitudinally collapses distal end 1626 toward proximal end 1624 along pull wire 1627 and thereby deflects elongated member 1625 radially outwardly from the catheter assembly. By pre-forming a bias onto elongated member, the elongated member 1625 forms a loop along a plane that is orthogonal to the longitudinal axis of the catheter body 1610, as shown in FIGS. 16B-C.
Moreover, the assembly 1600 is further shown to be adapted to track over a guidewire 1602 via a guidewire lumen 1615 that is shown in FIGS. 16A-C to extend along elongated member 1625 and further proximally along catheter body 1610. As such, elongated member 1625 is preferably positioned over a sufficiently flexible portion of the guidewire in order to form the looped shape as just described. Moreover, it is further contemplated that distal and proximal guidewire tracking members or bores (not shown) may be provided on distal tip 1619 and catheter body 1610, respectively, such that the guidewire 1602 may also extend along the outside of elongated member 1625 and pull wire 1627, such that the elongate member's shape when deflected is not affected by guidewire 1602. Further to this dual tracking member embodiment, a stop (not shown) may be provided on guidewire 1602 distally of distal tip 1619 such that pull wire 1627 is no longer necessary to adjust the shapes of elongated body 1610. In this embodiment, by advancing distal tip 1619 against a stop, the proximal and distal ends 1624,1626 of elongated member 1625 are longitudinally collapsed together along guidewire 1602 to provide the desired deflection for elongated member 1625.
Circumferential ablation device assembly 1700 shown in
Circumferential ablation device assembly 1800 shown in
It is further contemplated that braided cages such as the types just described may be also used in combination with an inner or outer wall, such as a flexible polymeric wall, in order to expand an enclosed structure into a desired shape for ablation. Such a composite expandable member provides a suitable substitute to the inflatable balloon ablation embodiments herein shown and described.
Circumferential ablation device assembly 1900 shown in
Other alternative spline configurations to that just described for FIGS. 19A-B are contemplated which are adapted to position individual ablation elements along a circumferential pattern to form a circumferential ablation element for ablating tissue along or surrounding a pulmonary vein ostium according to the invention.
For example, circumferential ablation device assembly 2000 shown in FIGS. 20A-C provides each of a plurality of ablation elements on the distal end portions 2026 of a plurality of longitudinally oriented spline members 2025. During use in a left atrium or pulmonary vein ostium according to the invention, these spline members 2025 extend distally from a delivery passageway 2017 (shown in
More specifically to the components of assembly 2000 shown in FIGS. 20A-C, a delivery assembly 2000 includes an outer member 2011 that is a tubular member coaxially surrounding an inner member 2012 that is also a tubular member extending distally from a distal port 2018 of outer member 2011. A coaxial space is formed between outer and inner members 2011,2012 and provides a delivery passageway 2017 within which spline members 2025 are positioned in a circumferential array (
The configuration shown in FIGS. 20A-B represents a second position for the ablation elements 2030. However, in a different mode of operation during delivery to the left atrium (not shown), the distal end portions 2026 of spline members 2025 are radially confined in a longitudinal orientation within delivery passageway 2017 (
Other spline member configurations than that specifically shown in FIGS. 20A-C for assembly 2000 are also contemplated. For example, FIGS. 21A-C variously show similar assemblies to that shown in FIGS. 20A-C, but with some specific aspects varied. More specifically, each of FIGS. 21A-C show a higher number of spline members 2125 and associated ablation elements 2130. This embodiment illustrating that closer spacing may be required in some circumstances over a given circumference. Or, alternatively this illustrates that more ablation elements may be needed in order to maintain the requisite spacing between the individual elements so that a continuous circumferential lesion may be formed along circumferential regions of tissue with greater radii.
The distal end portions 2126 of spline members 2125 shown in
Circumferential ablation device assembly 2200 shown in
Lines 23-23 shown in
More specifically, the cross-section shown in
A cross-section of a further assembly is shown in
The spline members 2325 employed in the embodiments illustrated in FIGS. 23A-D may have diameters in the range of about 0.010 to about 0.020 inches, more preferably ranging from about 0.013 to about 0.015 inches. Where the spline members are hypotubes, as shown in
The overall combination of spline members 2425, ablation elements 2430, elongate member 2432, and cooperating engagement between elongate member 2432 and spline members 2425, through eyelets 2426, cooperate to form circumferential ablation member 2420. Moreover, circumferential ablation member 2420 is specifically shown in
It is to be appreciated that various ablation elements herein generally described above may be suitable substitutes for use with the assembly just described by reference to FIGS. 24A-B, wherein coiled electrode ablation elements are specifically shown in
For further illustration,
As would be apparent to one of ordinary skill from this disclosure, similar ablation element/actuator sub-assemblies, such as including individual electrodes and associated electrical conductors/couplers, or including fluid electrodes and associated electrical and fluid couplers, are also considered applicable to others of the various embodiments illustrated, though they may not be specifically shown or described with reference thereto. The use of thermocouples to monitor ablation temperature in the embodiments of the ablation devices are considered applicable.
FIGS. 24E-F show still a further illustrative embodiment for coupling a circumferential ablation element 2435 to associated spline members and actuating members in order to form a circumferential ablation member such as that shown in FIGS. 24A-B. More specifically, spline member 2425 is coupled to shaped elongate member 2432 via eyelet 2426 in much the same threaded manner as previously described for
As shown in further detail in
Other moveable engagement means are contemplated as suitable substitutes for the specific “eyelet” embodiment shown in
Additional variations for the spline members are further contemplated as suitable substitutes for those previously described above, such as by specific reference to spline members 2425 shown in
One such illustrative embodiment is shown in FIGS. 26A-B, wherein spline members 2625 are provided with predetermined arcuate and convoluted shapes. More specifically,
The specific geometry shown and just described for spline members 2625 by reference to FIGS. 26A-C is also believed to be beneficial for adapting the desired circumferential ablation element to ablate regions of tissue against the posterior left atrial wall and surrounding a pulmonary vein. More specifically, the side-by-side leg configurations bordered in the middle by a bended loop is believed to provide a robust support structure along the plane along which the circumferential ablation element is patterned. Notwithstanding this feature, however, such shaped spline structures may be further provided with angled orientations out of the plane of the resulting circumferential ablation element's shape without departing from the scope of the invention. Additionally, the opposing concavity and convexity of the reciprocally shaped legs provides wider base of their separation along the proximal and distal end portions 2627,2628 than along a mid region 2626, such that there is robust support along the proximal and distal end portions, but an overall flexibility provided by the mid region 2626.
A further circumferential ablation member 2720 according to the invention is shown variously in
The proximal 2750 and distal 2760 walls are not sealed to one another in the intermediate circumferential region 2745 between the sealed inner and outer portions 2741, 2743, respectively, along this radius, yielding a void space between the walls in that circumferential region, but for the presence of the spline members 2725 which extend between all three of the respectively sealed and unsealed regions as shown in
Further to the sealed regions 2741,2743 for housing 2740, an adhesive or other sufficient filler material may be used in order to ensure a fluid tight seal around the fluid tubing 2729 and spline members 2725 and between the housing's respectively sealed walls, as shown along intermediate layer 2747 between proximal and distal walls 2750,2760 in
When circumferential ablation member 2720 is withdrawn into a delivery sheath (not shown), spline members 2725 are adjusted to a radially collapsed condition which adjusts the housing 2740 to a folded position that is adapted for delivery to and from the atrium for ablation (not shown). Once in the left atrium, spline members 2725 are advanced distally from the delivery sheath in the radially extended condition as shown in FIGS. 27A-B. Accordingly, circumferential region 2745 is positioned to form a circumferential ablation element when an ablative fluid couples to tissue through the porous portion of distal wall 2760 along that region. As previously described for other embodiments, this fluid coupling may include for example a chemically ablative fluid, or may incorporate an electrically conductive fluid energized with current from electrodes, such as shown schematically at electrodes 2730 which are positioned along spline members along the porous and ablative circumferential region 2745. It is further contemplated that the elongated member forming the spline members 2725 themselves may be electrically conductive, such as a conductive metal construction, and provide such electrode function over an above the support and positioning functions otherwise herein described.
A further circumferential ablation member 2820 forming an ablative circumferential region along a distal wall of a radially adjustable housing is shown in FIGS. 28A-C. This embodiment however allows for the radial adjustment of a housing 2840 by manipulation of cooperating portions of catheter body 2810 and without the need for withdrawal or advancement of a separate, confining delivery sheath as with the
With reference to
With reference to
As shown in
Spline members 2925 may be made by cutting longitudinal grooves into outer member 2911, but should not be limited as such. For example, spline members 2925 may alternatively be separate components secured to outer and inner members 2911,2912, such as for example separate shaped members such as spline members 2625 shown and described by reference to
In another specific embodiment, the electrode elements 2930 is incorporated along spline members 2925. In this embodiment, distal wall 2960 is porous along circumferential ablative surface 2961, and housing 2940 further includes a backing or proximal wall (not shown) that covers proximal end portions 2922 of spline members 2925.
With reference to
With reference to
Further to the various embodiments just described incorporating housings that are controllably positioned by use of deflectable spline members, the porous wall aspects of such embodiments may be constructed according to several known structures and methods. Porous fluoropolymers such as porous polytetrafluoroethylene (PTFE), and in particular the expanded variety (e-PTFE), may be suitable. In such case, however, the corresponding porous wall would be relatively non-elastomeric, and therefore must be adjusted between folded and taut conditions between the delivery and ablation positions described by reference to the particular embodiments. However, such porous material may also be constructed from an elastomer, such as for example a porous silicone material, which beneficially may have an elastomeric memory to a tubular state in the corresponding delivery position and which stretches to the ablation positions as herein described. Such porous elastomer embodiment is believed to be highly beneficial for use in the embodiments described by reference to
As common to each of the following embodiments, a source of acoustic energy is provided a delivery device that also includes an anchoring mechanism. In one mode, the anchoring device comprises an expandable member that also positions the acoustic energy source within the body; however, other anchoring and positioning devices may also be used, such as, for example, a basket mechanism. In a more specific form, the acoustic energy source is located within the expandable member and the expandable member is adapted to engage a circumferential path of tissue either about or along a pulmonary vein in the region of its ostium along a left atrial wall. The acoustic energy source in turn is acoustically coupled to the wall of the expandable member and thus to the circumferential region of tissue engaged by the expandable member wall by emitting a circumferential and longitudinally collimated ultrasound signal when actuated by an acoustic energy driver. The use of acoustic energy, and particularly ultrasonic energy, offers the advantage of simultaneously applying a dose of energy sufficient to ablate a relatively large surface area within or near the heart to a desired heating depth without exposing the heart to a large amount of current. For example, a collimated ultrasonic transducer can form a lesion, which has about a 1.5 mm width, about a 2.5 mm diameter lumen, such as a pulmonary vein and of a sufficient depth to form an effective conductive block. It is believed that an effective conductive block can be formed by producing a lesion within the tissue that is transmural or substantially transmural. Depending upon the patient as well as the location within the pulmonary vein ostium, the lesion may have a depth of about 1 to 10 mm. It has been observed that the collimated ultrasonic transducer can be powered to provide a lesion having these parameters so as to form an effective conductive block between the pulmonary vein and the posterior wall of the left atrium.
With specific reference now to the embodiment illustrated in
Each lumen extends between a proximal port (not shown) and a respective distal port, which distal ports are shown as distal guidewire port 805 for guidewire lumen 804, distal inflation port 807 for inflation lumen 806, and distal lead port 809 for electrical lead lumen 808. Although the guidewire, inflation and electrical lead lumens are generally arranged in a side-by-side relationship, the elongate catheter body 802 can be constructed with one or more of these lumens arranged in a coaxial relationship, or in any of a wide variety of configurations that will be readily apparent to one of ordinary skill in the art.
In addition, the elongate catheter body 802 is also shown in
One more detailed construction for the components of the elongate catheter body 802 that is believed to be suitable for use in transeptal left atrial ablation procedures is as follows. The elongate catheter body 802 itself may have an outer diameter provided within the range of from about 5 French to about 10 French, and more preferable from about 7 French to about 9 French. The guidewire lumen preferably is adapted to slideably receive guidewires ranging from about 0.010 inch to about 0.038 inch in diameter, and preferably is adapted for use with guidewires ranging from about 0.018 inch to about 0.035 inch in diameter. Where a 0.035 inch guidewire is to be used, the guidewire lumen preferably has an inner diameter of 0.040 inch to about 0.042 inch. In addition, the inflation lumen preferably has an inner diameter of about 0.020 inch in order to allow for rapid deflation times, although may vary based upon the viscosity of inflation medium used, length of the lumen, and other dynamic factors relating to fluid flow and pressure.
In addition to providing the requisite lumens and support members for the ultrasound transducer assembly, the elongate catheter body 802 of the present embodiment must also be adapted to be introduced into the left atrium such that the distal end portion with balloon and transducer may be placed within the pulmonary vein ostium in a percutaneous translumenal procedure, and even more preferably in a transeptal procedure as otherwise herein provided. Therefore, the distal end portion 812 is preferably flexible and adapted to track over and along a guidewire seated within the targeted pulmonary vein. In one further more detailed construction that is believed to be suitable, the proximal end portion is adapted to be at least 30% stiffer than the distal end portion. According to this relationship, the proximal end portion may be suitably adapted to provide push transmission to the distal end portion while the distal end portion is suitably adapted to track through bending anatomy during in vivo delivery of the distal end portion of the device into the desired ablation region.
Notwithstanding the specific device constructions just described, other delivery mechanisms for delivering the ultrasound ablation member to the desired ablation region are also contemplated. For example, while the
More specifically regarding expandable balloon 820 as shown in varied detail between
The expandable balloon 820 may be constructed from a variety of known materials, although the balloon 820 preferably is adapted to conform to the contour of a pulmonary vein ostium. For this purpose, the balloon material can be of the highly compliant variety, such that the material elongates upon application of pressure and takes on the shape of the body lumen or space when fully inflated. Suitable balloon materials include elastomers, such as, for example, but without limitation, Silicone, latex, or low durometer polyurethane (for example, a durometer of about 80A).
In addition or in the alternative to constructing the balloon of highly compliant material, the balloon 820 can be formed to have a predefined fully inflated shape (i.e., be preshaped) to generally match the anatomic shape of the body lumen in which the balloon is inflated. For instance, as described below in greater detail, the balloon can have a distally tapering shape to generally match the shape of a pulmonary vein ostium, and/or can include a bulbous proximal end to generally match a transition region of the atrium posterior wall adjacent to the pulmonary vein ostium. In this manner, the desired seating within the irregular geometry of a pulmonary vein or vein ostium can be achieved with both compliant and non-compliant balloon variations.
Notwithstanding the alternatives that may be acceptable as just described, the balloon 820 is preferably constructed to exhibit at least 300% expansion at 3 atmospheres of pressure, and more preferably to exhibit at least 400% expansion at that pressure. The term “expansion” is herein intended to mean the balloon outer diameter after pressurization divided by the balloon inner diameter before pressurization, wherein the balloon inner diameter before pressurization is taken after the balloon is substantially filled with fluid in a taut configuration. In other words, “expansion” is herein intended to relate to change in diameter that is attributable to the material compliance in a stress strain relationship. In one more detailed construction which is believed to be suitable for use in most conduction block procedures in the region of the pulmonary veins, the balloon is adapted to expand under a normal range of pressure such that its outer diameter may be adjusted from a radially collapsed position of about 5 mm to a radially expanded position of about 2.5 cm (or approximately 500% expansion ratio).
The ablation member illustrated in FIGS. 31A-D, takes the form of annular ultrasonic transducer 830. In the illustrated embodiment, the annular ultrasonic transducer 830 has a unitary cylindrical shape with a hollow interior (i.e., is tubular shaped); however, the transducer applicator 830 can have a generally annular shape and be formed of a plurality of segments. For instance, the transducer applicator 830 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 sector 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.
As is shown in detail in
The outer and inner tubular members 833,834 enclose central layer 832 within their coaxial space and are constructed of an electrically conductive material. In the illustrated embodiment, these transducer electrodes 833,834 comprise a metallic coating, and more preferably a coating of nickel, copper, silver, gold, platinum, or alloys of these metals.
One more detailed construction for a cylindrical ultrasound transducer for use in the present application is as follows. The length of the transducer 830 or transducer assembly (e.g., multi-element array of transducer elements) desirably is selected for a given clinical application. In connection with forming circumferential conduction blocks in cardiac or pulmonary vein wall tissue, the transducer length can fall within the range of approximately 2 mm up to greater than 10 mm, and preferably equals about 5 to 10 mm. A transducer accordingly sized is believed to form a lesion of a width sufficient to ensure the integrity of the formed conductive block without undue tissue ablation. For other applications, however, the length can be significantly longer.
Likewise, the transducer outer diameter desirably is selected to account for delivery through a particular access path (e.g., percutaneously and transseptally), for proper placement and location within a particular body space, and for achieving a desired ablation effect. In the given application within or proximate of the pulmonary vein ostium, the transducer 830 preferably has an outer diameter within the range of about 1.8 mm to greater than 2.5 mm. It has been observed that a transducer with an outer diameter of about 2 mm generates acoustic power levels approaching 20 Watts per centimeter radiator or greater within myocardial or vascular tissue, which is believed to be sufficient for ablation of tissue engaged by the outer balloon for up to about 2 cm outer diameter of the balloon. For applications in other body spaces, the transducer applicator 830 may have an outer diameter within the range of about 1 mm to greater than 3-4 mm (e.g., as large as 1 to 2 cm for applications in some body spaces).
The central layer 832 of the transducer 830 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 830 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 transducer 830 is vibrated across the wall thickness and to radiate collimated acoustic energy in the radial direction. For this purpose, as best seen in
The proximal ends of these leads are adapted to couple to an ultrasonic driver or actuator 840, which is schematically illustrated in
The transducer also can be sectored by scoring or notching the outer transducer electrode 833 and part of the central layer 832 along lines parallel to the longitudinal axis L of the transducer 830, as illustrated in
The ultrasound transducer just described is combined with the overall device assembly according to the present embodiment as follows. In assembly, the transducer 830 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 803 does not contact an appreciable amount of the inner surface of transducer inner tubular member 834. This is because the piezoelectric crystal which forms central layer 832 of ultrasound transducer 830 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 833,834 of the crystal via the electrical leads 836,837. 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 830 seats coaxial about the inner member 803 and is supported about the inner member 803 in a manner providing a gap between the inner member 803 and the transducer inner tubular member 834. That is, the inner tubular member 834 forms an interior bore 835 that loosely receives the inner member 803. Any of a variety of structures can be used to support the transducer 830 about the inner member 803. For instance, spacers or splines can be used to coaxially position the transducer 830 about the inner member 803 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 803 and lie between the inner member 803 and the transducer 830 can support the transducer 830 in a manner similar to that illustrated in U.S. Pat. No. 5,606,974 to Castellano issued Mar. 4, 1997, and entitled “Catheter Having Ultrasonic Device.” 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.” The disclosures of these references are herein incorporated in their entirety by reference thereto.
In the illustrated embodiment, at least one stand-off region 838 is provided along inner member 803 in order to ensure that the transducer 830 has a radial separation from the inner member 803 to form a gap filled with air and/or other fluid. In one preferred mode shown in
In a further mode, the elongate catheter body 802 can also include additional lumens which lie either side by side to or coaxial with the guidewire lumen 804 and which terminate at ports located within the space between the inner member 803 and the transducer 830. A cooling medium can circulate through space defined by the stand-off 838 between the inner member 803 and the transducer 830 via these additional lumens. By way of example, carbon dioxide gas, circulated at a rate of 5 liters per minute, can be used as a suitable cooling medium to maintain the transducer at a lower operating temperature. It is believed that such thermal cooling would allow more acoustic power to transmit to the targeted tissue without degradation of the transducer material.
The transducer 830 desirably is electrically and mechanically isolated from the interior of the balloon 820. Again, any of a variety of coatings, sheaths, sealants, tubing and the like may be suitable for this purpose, such as those described in U.S. Pat. Nos. 5,620,479 to Diederich and 5,606,974 to Castellano. In the illustrated embodiment, as best illustrated in
An ultra thin-walled polyester heat shrink tubing 844 or the like then seals the epoxy coated transducer. Alternatively, the epoxy covered transducer 830, inner member 803 along stand-off region 838 can be instead inserted into a tight thin wall rubber or plastic tubing made from a material such as TeflonŽ, polyethylene, polyurethane, silastic or the like. The tubing desirably has a thickness of 0.0005 to 0.003 inches.
When assembling the ablation device assembly, additional epoxy is injected into the tubing after the tubing is placed over the epoxy coated transducer 830. As the tube shrinks, excess epoxy flows out and a thin layer of epoxy remains between the transducer and the heat shrink tubing 844. These layers 842,844 protect the transducer surface, help acoustically match the transducer 830 to the load, makes the ablation device more robust, and ensures air-tight integrity of the air backing.
Although not illustrated in
The ultrasonic actuator 840 generates alternating current to power the transducer 830. The ultrasonic actuator 840 drives the transducer 830 at frequencies within the range of about 5 MHz to about 20 MHz, and preferably for the illustrated application within the range of about 7 MHz to about 10 MHz. In addition, the ultrasonic driver can modulate the driving frequencies and/or vary power in order to smooth or unify the produced collimated ultrasonic beam. For instance, the function generator of the ultrasonic actuator 840 can drive the transducer at frequencies within the range of 6.8 MHz and 7.2 MHz by continuously or discretely sweeping between these frequencies.
The ultrasound transducer 830 of the present embodiment sonically couples with the outer skin of the balloon 820 in a manner that forms a circumferential conduction block at a location where a pulmonary vein extends from an atrium as follows. Initially, the ultrasound transducer is believed to emit its energy in a circumferential pattern that is highly collimated along the transducer's length relative to its longitudinal axis L (see
Further to the transducer-balloon relationship just described, the energy is coupled to the tissue largely via the inflation fluid and balloon skin. It is believed that, for in vivo uses of the present invention, the efficiency of energy coupling to the tissue, and therefore ablation efficiency, may significantly diminish in circumstances where there is poor contact and conforming interface between the balloon skin and the tissue. Accordingly, it is contemplated that several different balloon types may be provided for ablating different tissue structures so that a particular shape may be chosen for a particular region of tissue to be ablated.
In one particular balloon-transducer combination shown in
The ultrasound transducer described in various levels of detail above has been observed to provide a suitable degree of radiopacity for locating the energy source at a desired location for ablating the conductive block. However, it is further contemplated that the elongate catheter body 802 may include an additional radiopaque marker or markers (not shown) to identify the location of the ultrasonic transducer 830 in order to facilitate placement of the transducer at a selected ablation region of a pulmonary vein via X-ray visualization. The radiopaque marker is opaque under X-ray, and can be constructed, for example, of a radiopaque metal such as gold, platinum, or tungsten, or can comprise a radiopaque polymer such as a metal loaded polymer. The radiopaque marker is positioned coaxially over an inner tubular member 803, in a manner similar to that described in connection with the embodiment of
The present circumferential ablation device is introduced into a pulmonary vein of the left atrium in a manner similar to that described above. Once properly positioned within the pulmonary vein or vein ostium, the pressurized fluid source inflates the balloon 820 to engage the lumenal surface of the pulmonary vein ostium. Once properly positioned, the ultrasonic driver 840 is energized to drive the transducer 830. It is believed that by driving the ultrasonic transducer 830 at 20 acoustical watts at an operating frequency of 7 MHz, that a sufficiently sized lesion can be formed circumferentially about the pulmonary vein ostium in a relatively short period of time (e.g., 1 to 2 minutes or less). It is also contemplated that the control level of energy can be delivered, then tested for lesion formation with a test stimulus in the pulmonary vein, either from an electrode provided at the tip area of the ultrasonic catheter or on a separate device such as a guidewire through the ultrasonic catheter. Therefore, the procedure may involve ablation at a first energy level in time, then check for the effective conductive block provided by the resulting lesion, and then subsequent ablations and testing until a complete conductive block is formed. In the alternative, the circumferential ablation device may also include feedback control, for example, if thermocouples are provided at the circumferential element formed along the balloon outer surface. Monitoring temperature at this location provides indicia for the progression of the lesion. This feedback feature may be used in addition to or in the alternative to the multi-step procedure described above.
FIGS. 32A-C show various alternative embodiments of the present invention for the purpose of illustrating the relationship between the ultrasound transducer and balloon of the present invention just described above. More specifically,
The balloon 820 in
As mentioned above, the transducer 830 can be formed of an array of multiple transducer elements that are arranged in series and coaxial. The transducer can also be formed to have a plurality of longitudinal sectors. These modes of the transducer have particular utility in connection with the tapering balloon designs illustrated in
The circumferential ablation device 800 can also include additional mechanisms to control the depth of heating. For instance, the elongate catheter body 802 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 820 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.
The depth of heating can also be controlled by selecting the inflation material to have certain absorption characteristics. For example, by selecting an inflation material with higher absorption than water, less energy will reach the balloon wall, thereby limiting thermal penetration into the tissue. It is believed that the following fluids may be suitable for this application: vegetable oil, silicone oil and the like.
Uniform heating can also be enhanced by rotating the transducer within the balloon. For this purpose, the transducer 830 may be mounted on a torquable member that is movably engaged within a lumen that is formed by the elongate catheter body 802.
Another aspect of the balloon-transducer relationship of the present embodiment is illustrated by reference to FIGS. 33A-B. In general, as to the variations embodied by those FIGS., the circumferential ultrasound energy signal is modified at the balloon coupling level such that a third order of control is provided for the tissue lesion pattern (the first order of control is the transducer properties affecting signal emission, such as length, width, shape of the transducer crystal; the second order of control for tissue lesion pattern is the balloon shape, per above by reference to FIGS. 32A-C).
This third order of control for the tissue lesion pattern can be understood more particularly with reference to
For various reasons, the “narrow pass filter” embodiment of
In each of the embodiments illustrated in
The inverted transducer section produces a highly directional beam pattern. By sweeping the transducer through 360 degrees of rotation, as described above, a circumferential lesion can be formed while using less power than would be required with a planar or tubular transducer.
The embodiments shown in
FIGS. 35B-D show a specific mode wherein transducer assembly 3531 has an arcuate, circumferential distal face 3533 that emits a distally or forward oriented circumferential pattern. A pair-shaped or distally-tapered expandable member 3527 surrounds the transducer and engages the pulmonary vein ostium. The distal end 3529 is adapted to engage the pulmonary vein. The forwardly focused ultrasonic energy passes through the distally tapered wall 3528 of expandable member 3527. In addition, shown schematically such transducer assembly 3531 may comprise a plurality of flat panels such as at 3532 that are individually driven. It is contemplated that such arcuate transducer crystal surfaces may require complex poling in the forward or angled direction desired for emission, as would be apparent to one of ordinary skill based upon this disclosure.
FIGS. 35E-G show a further variation, wherein the transducer crystal 3536 is conically shaped with a distally facing surface 3537 for emitting the desired energy through distally tapered wall 3528 of balloon 3527. This shape similarly requires poling in the orthogonal plane to the surface for desired ablation. In a further variation,
A series of circumferentially spaced ultrasonic panels may also be used in the circumferential ablation member of the present invention, as shown variously in
FIGS. 36A-C show circumferentially spaced arcuate panels 3630 which surround inner member 3611 in radially extended positions such that distal surfaces 3632 are pointing toward the region to ablate along a distal aspect of the assembly such as along inner member 3611. FIGS. 37A-C show a further variation wherein such ultrasound panels 3730 have a substantially flat shape. In a radially extended position, the flat panel 3730 presents a distal surface 3732 that is angled toward the region of tissue to be ablated.
One more detailed construction for such ultrasound transducer panels is shown in
The transducer panels are adjustable from a radially collapsed position to a radially extended position by use of an expansion member, as shown in various modes by balloon 3825, braided cage 3826, adjustable splines 3827, and adjustable stand-off 3828, in
It is to be further understood that the various modes of the ultrasound-balloon embodiments just illustrated by reference to
As discussed above, the embodiments described herein are believed to be particularly useful in catheter assemblies that are specifically adapted for ablating tissue along a region where a pulmonary vein extends from a left atrium in the treatment of atrial fibrillation. Therefore, the assemblies and methods of the present invention are also contemplated for use in combination with, or where appropriate in the alternative to, the various particular features and embodiments shown and described in the following co-pending U.S. Patent Applications that also address circumferential ablation at a location where a pulmonary vein extends from an atrium: U.S. Ser. No. 08/889,798 for “CIRCUMFERENTIAL ABLATION DEVICE ASSEMBLY” to Michael D. Lesh et al., filed Jul. 8, 1997; U.S. Ser. No. 08/889,835 for “DEVICE AND METHOD FOR FORMING A CIRCUMFERENTIAL CONDUCTION BLOCK IN A PULMONARY VEIN” to Michael D. Lesh, filed Jul. 8, 1997; U.S. Ser. No. 09/199,736 for “CIRCUMFERENTIAL ABLATION DEVICE ASSEMBLY” to Chris J. Diederich et al., filed Feb. 3, 1998; and U.S. Ser. No. 09/260,316 for “DEVICE AND METHOD FOR FORMING A CIRCUMFERENTIAL CONDUCTION BLOCK IN A PULMONARY VEIN” to Michael D. Lesh. The disclosures of these references are herein incorporated in their entirety by reference thereto.
It is further contemplated that the embodiments shown and described herein may be combined, assembled together, or where appropriate substituted for, the various features and embodiments which are disclosed in the following co-pending provisional and non-provisional U.S. patent applications: the co-pending non-provisional U.S. patent application Ser. No. ______ for “FEEDBACK APPARATUS AND METHOD FOR ABLATION AT PULMONARY VEIN OSTIUM”, filed on the same day as this application, and claiming priority to Provisional U.S. Patent Application No. 60/122,571, filed on Mar. 2, 1999; co-pending Provisional U.S. Patent Application No. 60/133,610 for “BALLOON ANCHOR WIRE”, filed May 11, 1999; the co-pending non-provisional U.S. patent application for “TISSUE ABLATION DEVICE ASSEMBLY AND METHOD FOR ELECTRICALLY ISOLATING A PULMONARY VEIN OSTIUM FROM A POSTERIOR LEFT ATRIAL WALL”, filed on the same day as this application, and which claims priority to Provisional U.S. Patent Application No. 60/133,677, filed May 11, 1999; the co-pending non-provisional U.S. patent application for “APPARATUS AND METHOD INCORPORATING AN ULTRASOUND TRANSDUCER ONTO A DELIVERY MEMBER”, filed on the same day as this application, and which claims priority to Provisional U.S. Patent Application No. 60/133,680, filed May 11, 1999; and co-pending Provisional U.S. Patent Application Ser. No. 60/133,807 for “CATHETER POSITIONING SYSTEM”. The disclosures of these references are herein incorporated in their entirety by reference thereto.
In addition, a circumferential ablation device assembly according to the present invention may be used in combination with other linear ablation assemblies and methods, and various related components or steps of such assemblies or methods, respectively, in order to form a circumferential conduction block adjunctively to the formation of long linear lesions, such as in a less-invasive “maze”-type procedure. Examples of such assemblies and methods related to linear lesion formation and which are contemplated in combination with the presently disclosed embodiments are shown and described in the following additional co-pending U.S. patent applications and patents: U.S. Pat. No. 5,971,983, issued on Oct. 26, 1999, entitled “TISSUE ABLATION DEVICE AND METHOD OF USE” filed by Michael Lesh, M.D. on May 9, 1997; U.S. Ser. No. 09/260,316 for “TISSUE ABLATION SYSTEM AND METHOD FOR FORMING LONG LINEAR LESION” to Langberg et al., filed May 1, 1999; and U.S. Ser. No. 09/073,907 for “TISSUE ABLATION DEVICE WITH FLUID IRRIGATED ELECTRODE”, to Alan Schaer et al., filed May 6, 1998. The disclosures of these references are herein incorporated in their entirety by reference thereto.
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 might be made of equivalents without departing from the spirit of the invention or the scope of the following claims.
The following claims are provided to illustrate examples of some beneficial aspects of the subject matter disclosed herein which are within the scope of the present invention.