Patent Publication Number: US-2010114269-A1

Title: Variable geometry balloon catheter and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part-of Patent Application Ser. No. 11/476,928, filed Jun. 28, 2006, the entirety of which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     n/a 
     FIELD OF THE INVENTION 
     The present invention relates to a method and system having a variable geometry treatment element in a medical device, and in particular, to a cooling chamber of a medical device capable of having multiple geometric configurations 
     BACKGROUND OF THE INVENTION 
     Minimally invasive devices, such as catheters, are often employed for surgical procedure, including those involving ablation, dilation, and the like. In a particular situation, an ablation procedure may involve creating a series of inter-connecting lesions in order to electrically isolate tissue believed to be the source of an arrhythmia. During the course of such a procedure, a physician may employ several different catheters having variations in the geometry and/or dimensions of the ablative element in order to produce the desired ablation pattern. Each catheter may have a unique geometry for creating a specific lesion pattern, with the multiple catheters being sequentially removed and replaced to create the desired multiple lesions. Each exchange represents an added risk to the patient as inserting and removing catheters in the vasculature carries a number of inherent risks, mainly embolism. Exchanging these various catheters during a procedure can cause inaccuracies or movement in the placement and location of the distal tip with respect to the tissue to be ablated, and may further add to the time required to perform the desired treatment. These potential inaccuracies and extended duration of the particular procedure increase the risk to the patient undergoing treatment. Accordingly, it would be desirable to provide a single medical device having the ability to provide ablative patterns of various shapes, without the need for additional catheters or the like having a single geometric orientation, and thus, limited in the ability to provide multiple ablative patterns. 
     SUMMARY OF THE INVENTION 
     The present invention advantageously provides a medical device, including a shaping element selectively transitionable from a first geometric configuration to a second geometric configuration; and an expandable element at least partially disposed within the shaping element, wherein expansion of the expandable element is restricted at least in part by the shaping element. The shaping element may be at least partially constructed from a shape-memory material, may include a substantially non-compliant balloon, and/or may be constructed from a non-compliant or very little compliant material such as Nylon, Pebax, or Polyester (or composites thereof) for example. The shaping element may be biased towards the first geometric configuration, which may include an elongated, substantially cylindrical shape. The second geometric configuration can include a substantially spherical shape. Also, the first geometric configuration can include a diameter of approximately 23 mm and the second geometric configuration can include a diameter of approximately 32 mm. An actuator element can be coupled to the shaping element, where the actuator element is able to cause the shaping element to transition from the first geometric configuration to the second geometric configuration. 
     A medical device is also provided, including an elongate body defining a proximal portion, a distal portion, and a fluid injection lumen; an expandable element coupled to the elongate body, wherein the expandable element is in fluid communication with the fluid injection lumen; and a substantially non-compliant balloon at least partially surrounding the expandable element and restricting the expansion of the expandable element at least in part, where the shaping element is configurable in an elongated, substantially cylindrical shape and a substantially spherical shape. 
     A method for thermally affecting a tissue region, such as cardiac tissue, is provided, including positioning a medical device proximate to the tissue region, the medical device having a shaping element in a first geometric configuration, and an expandable element at least partially disposed within the shaping element; directing a coolant into the expandable element to expand at least a portion of the expandable element, where the expansion of the expandable element is restricted at least in part by the shaping element; and thermally affecting the tissue region. The method may include configuring the shaping element into a second geometric configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  illustrates an embodiment of a medical device in accordance with the present invention; 
         FIG. 2  shows an additional view of an embodiment of a medical device in accordance with the present invention; 
         FIG. 3  shows a geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 4  depicts an additional geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 5  illustrates another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 6  shows still another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 7  depicts an additional geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 8  illustrates another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 9  shows still another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 10  shows still another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 11  depicts an additional geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 12  illustrates another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 13  shows still another geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 14  depicts an additional geometric configuration of an embodiment of a medical device in accordance with the present invention; 
         FIG. 15  illustrates an embodiment of a medical device in accordance with the present invention; and 
         FIG. 16  shows an embodiment of a medical device in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now referring to  FIGS. 1 and 2 , an embodiment of the present invention provides a medical device  10  defining an elongate body  12  such as a catheter. The elongate body  12  may define a proximal portion and a distal portion, and may further include one or more lumens disposed within the elongate body thereby providing mechanical, electrical, and/or fluid communication between the proximal portion of the elongate body  12  and the distal portion of the elongate body. For example, the elongate body  12  may include an injection lumen  14  and an exhaust lumen defining a fluid flow path therethrough. In addition, the elongate body may include a guidewire lumen  16  extending along at least a portion of the length of the elongate body  12  for over-the-wire applications, where the guidewire lumen  16  may define a proximal end and a distal end. The guidewire lumen  16  may be disposed within the elongate body  12  such that the distal end of the guidewire lumen  16  extends beyond the and out of the distal portion of the elongate body  12 . 
     The elongate body  12  may further include a deflection mechanism whereby the elongate body and components coupled thereto may be maneuvered in one or more planes of motion. For example, a pull wire with a proximal end and a distal end may have its distal end anchored to the elongate body at or near the distal end. The proximal end of the pull wire may be anchored to a knob or lever  18  controllable and responsive to an input from an operator or physician. 
     The medical device  10  of the present invention may include a tip portion  20  towards the distal portion of the elongate body  12 , which may be coupled to a portion of the guidewire lumen  16 . For example, the tip portion  20  may circumscribe a portion of the distal end of the guidewire lumen  16 . The tip portion  20  may define a cavity in fluid communication with the injection lumen  14 , yet be isolated from fluid communication with the guidewire lumen  16 , i.e., the tip portion  20  may be able to receive a fluid therein while the guidewire lumen  16  remains excluded from any fluid flow originating and/or flowing through the elongate body  12  of the catheter. Accordingly, the tip portion  20  may be able to receive a fluid flow, such as a coolant, thereby allowing the tip portion  20  to thermally affect a desired tissue region and/or to create a spot lesion or focalized ablative pattern. 
     The medical device  10  of the present invention may further include a shaping element  22  coupled to the distal portion of the elongate body  12  that is configurable into a plurality of geometric configurations, such as those shown in  FIGS. 3-14 . The shaping element  22  may also be biased or predisposed to take on a particular geometric configuration. The shaping element  22  may define a mesh or wire structure, and may be constructed from a combination of elastic materials, non-elastic materials, and/or shape-memory materials, such as a nickel-titanium alloy or the like, for example. The shaping element can also be constructed of non-metallic materials, such as Nylon, Dacron, Kevlar or other fiber-type materials woven or otherwise set into the desired configuration. As used herein, the term “mesh” is intended to include any element having an openwork fabric or structure, and may include but is not limited to, an interconnected network of wire-like segments, a sheet of material having numerous apertures and/or portions of material removed, or the like. 
     The shaping element  22  may further include a substantially non-compliant and/or minimally elastic structure able to impart its geometric characteristics or configuration onto interior expandable structures or components having increased elasticity, compliance, or stretchability (discussed in more detail below). That is, the shaping element may have a lesser modulus of elasticity and/or a greater rigidity than that of one or more expandable structures contained at least partially therein. For example, the shaping element  22  may include a preformed balloon or inflatable structure constructed from a non-compliant or very little compliant material such as Nylon, Pebax, or Polyester (or composites thereof) for example. The shaping element  22  may be preformed by blow-molding, thermally setting or other suitable means to obtain a predefined shape. 
     A particular geometric configuration of the shaping element  22  may be achieved through the application of mechanical force, thermal energy, and/or electrical energy. For example, the shaping element  22  may be predisposed and/or biased towards a first geometric configuration, which may include a substantially elongated, cylindrical shape. Upon the application of a particular mechanical, thermal, and/or electrical force, the shaping element  22  may be selectively transitioned from the first geometric configuration to a second geometric configuration, having a substantially spherical shape, for example. The transitionable geometric configurations may also include discrete dimensions, such as an outer diameter. For example, the shaping element  22  may be selectively transitionable from a first geometric configuration having a first diameter (such as 23 mm for example), to a second geometric configuration having a second diameter (such as 32 mm for example). Additional geometric configurations having selectable, discrete, and predetermined diameters may also be available. 
     As discussed, the transition from a first particular configuration to a second particular configuration of the shaping element  22  may be achieved by the application of mechanical, thermal, or electrical forces. Further, the transition may be a result of particular material properties exhibited by the construction of the shaping element  22 . For example, the shaping element  22  may include a mesh structure including components made from a shape-memory material, as well as components made from a relatively non-elastic material. The components made from the shape-memory material may be predisposed and/or biased towards a first geometric configuration, while the non-elastic components may be predisposed and/or biased towards a second geometric configuration. When the shaping element  22  is placed under a first thermal condition, such as a temperature range between 10.degree. C. to 40.degree. C., the shape-memory material may be dominant over the non-elastic components, causing the shaping element  22  to retain the first geometric configuration. When subjected to a second thermal condition, between −100.degree. C. and 10.degree. C. for example, the shape-memory components may become increasingly pliable, thereby allowing the non-elastic components to dominate and causing the shaping element  22  to assume the second geometric configuration. 
     An additional example of a shaping element  22  being configurable into multiple geometric configurations may include a shaping element  22  constructed from a single material being predisposed and/or biased towards a first geometric configuration. However, the medical device of the present invention may include an actuator element  24  that may impart a mechanical force on the shaping element  22  and/or a component coupled thereto to overcome the predisposition of the shaping element  22  to retain the first geometric configuration. As shown in  FIGS. 1 and 2 , the actuator element  24  may include a pull wire or the like affixed to a portion of the shaping element  22  and/or portions of the medical device in proximity to the shaping element, such as the guidewire lumen  16 . For example, a portion of the shaping element  22  may be coupled to a portion of the movable guidewire lumen  16 . Upon manipulation of the actuator element  24 , the guidewire lumen  16  may be longitudinally moved in a proximal direction, whereby the predisposed first geometric configuration of the shaping element  22  is attained. However, the guidewire lumen  16  may then be moved in a distal direction, thereby tensioning the shaping element  22  in order to overcome the bias of the shaping element. As a result, the shaping element  22  attains a second geometric configuration different than the first geometric configuration. Additionally, the actuator element  24  may include a push rod or other mechanical coupling for imparting a mechanical and/or physical force on the shaping element  22  to overcome and thereby dominate the first geometric configuration that the shaping element  22  may be predisposed to provide. For example, as shown in  FIGS. 15 and 16 , a pull wire  25  may be coupled to a portion of the shaping element  22  for tensioning and/or loosening of the shaping element  22  during a procedure. Moreover, the shaping element  22  may be slideably disposed about the guidewire lumen  16  such that the guidewire lumen  16  remains in place while the shaping element  22  is manipulated into the desired configuration. 
     In addition to providing desired geometric configurations, the shaping element  22  may be electrically conductive. For example, the shaping element  22  may be used to provide the ability to map electrical properties of a particular tissue region, such as in the heart, whereby an electrocardiogram may be obtained. Further, the shaping element  22  may be used to provide a conductive surface for delivering radiofrequency energy to a particular tissue site, and/or to provide the ability to measure a relative impedance and/or resistance for the purpose of fluid leak detection. 
     The medical device  10  of the present invention may further include an expandable element  26  at least partially disposed on the elongate catheter body  12 , and may further be disposed within a portion of the shaping element  22 . The expandable element  26  may include a balloon or other expandable structure, which may define a proximal end coupled to the distal portion of the elongate body  12  of the catheter, while further defining a distal end coupled to the tip portion and/or the distal end of the guidewire lumen  16 . The expandable element  26  may include a greater elasticity, compliance, or stretchability compared to the shaping element  22 . For example, the expandable element  26  may be constructed from a material, such as an elastomer, like polyurethane, latex, polyolefin, styrene butadiene styrene for example, that has a greater modulus of elasticity or lesser rigidity than the shaping element  22 . The resulting comparative elastic or stiffness characteristics of the shaping element  22  and the expandable element  26  may allow the shaping element  26  to limit, restrict, or otherwise inhibit at least a portion of the expansion or inflation of the expandable element  26 . This allows the shaping element  22  to impart or otherwise project its geometric configurations, including shape and dimensions, onto the underlying expandable element  22 . 
     The expandable element  26  may have any of a myriad of shapes, and may further include one or more material layers providing for puncture resistance, radiopacity, or the like. The expandable element  26  may be in communication with the fluid injection and exhaust lumens of the medical device as described above, i.e., a fluid flow path may provide an inflation fluid, such as a cryogenic fluid or the like, to the interior of the expandable element  26 . The expandable element  26  may be inflated within the shaping element  22 , thereby conforming to the shape of the shaping element  22 . As such, irrespective of whether the expandable element  26  has a particular shape or dimensional capacity, the shaping element  22  may be used to provide a guide and/or “shell” within which the expandable element  26  may be inflated to ensure a desired geometric configuration and/or a desired volume. 
     The shaping element  22  may, therefore, limit certain portions of the expandable element  26  from expanding, while other areas or regions of the expandable element  26  may be stretched. As portions of the expandable element  26  are stretched, the particular thermal properties of that region may change, i.e., the stretched portions may more readily conduct thermal energy than portions of the expandable element  26  that have not been stretched to the same extent, if at all. Accordingly, the shaping element  22  may provide a particular shape or geometric configuration in which particular areas of the expandable element  26  are allowed to stretch to thereby conduct heat more readily, while other portions of the expandable element  26  are not stretched to provide a degree of thermal insulation. As a result, the shaping element  22  and thus the expandable element  26  may be configured to provide varying thermal conductivity to different regions of tissue while the medical device  10  remains in a fixed position. 
     In an exemplary system, the medical device of the present invention may be coupled to a console  28 , which may contain a fluid supply and exhaust, as well as various control mechanisms for operation of the medical device  10 . 
     An exemplary use of the medical device  10  of the present invention may include making multiple ablative lesions having varying geometric shapes and/or dimensions on a desired tissue region. In an exemplary procedure, the medical device  10  may be selectively transitioned from one or more geometric configurations in order to thermally treat a cardiac tissue region, such as one or more pulmonary veins. Pulmonary veins are often targeted for tissue ablation in order to treat various arrhythmias of the heart, and can present anatomical and dimensional variations from patient to patient, rendering desirable the ability of the medical device  10  to treat a range of shapes and dimensions. For example, an interior or surface circumference of a selected pulmonary vein may range from approximately 20 mm to 40 mm, and the medical device  10  may correspondingly have a plurality of selectable geometric configurations in that measurement range to affect treatment. 
     In such a procedure, the distal portion of the medical device  10  may be positioned in proximity to a tissue region to be treated. Primarily, the tip portion  20  of the medical device  10  may be subjected to a fluid flow, including a cryogenic coolant or the like, to create a focalized and/or spot lesion within a desired tissue region. Additionally, the shaping element  22  of the medical device  10  may be in a first geometric configuration, such as an elongated cylindrical shape, for example. Subsequently, a fluid, such as a cryogenic coolant, may be used to expand the expandable element  26  such that the expandable element  26  substantially fills the interior cavity defined by the shaping element  22 . The expandable element  26  may be inflated such that portions of the expandable element protrude through a mesh construct of the shaping element  22  to contact and/or be in position to thermally affect the desired tissue region, while substantially retaining the geometric configuration of the shaping element  22 . Where a non-compliant structure is employed as the shaping element  22 , the expandable element  26  may be inflated to abut or otherwise substantially fill an interior cavity defined by the shaping element  22 , and thermal exchange with the targeted tissue region may be affected with the shaping element  22 . While the shaping element  22  ensures the expandable element  26  retains the first geometric configuration, coolant may be circulated through the expandable element  26  in order to thermally affect the tissue region and/or to create a tissue lesion having a desired shape, such as a linear tissue lesion. 
     Upon achieving the desired effect, the flow of coolant through the expandable element  26  may be discontinued such that the expandable element  26  s at least partially deflated. The medical device  10  may then be repositioned in proximity to a tissue region where additional thermal treatment may be performed. The shaping element  22  may subsequently be transitioned from the first geometric configuration to the second geometric configuration, which may include a substantially spherical shape, for example. The transition may be achieved by imparting a mechanical, thermal, and/or electrical force on the shaping element, and may further include manipulation of the actuator element  24 . Once the desired geometric configuration has been achieved, the expandable element  26  may once again be inflated within the shaping element  22 , using the aforementioned coolant, for example. Accordingly, the second geometric configuration may be used to impart a second tissue lesion and/or thermally affected area having a varied geometric pattern and/or dimension to that of the first tissue lesion, such as a substantially circular shape, for example. Additional configurations may include larger or smaller dimensions to treat subsequent tissue areas. 
     Although the exemplary use described above employed first and second geometric configurations, it is contemplated that a shaping element capable of more than two configurations may be employed and achieved through a combination of mechanical, thermal, and/or electrical forces, as well as through characteristics provided through material selection in the construction of the shaping element. Moreover, while examples and illustrations of particular geometric configurations have been provided, it is understood that virtually any shapes, configurations, and/or dimensions may be included and/or achieved by the medical device of the present invention, including but not limited to those shapes illustrated and described herein. A particular geometric configuration may include circular, conical, concave, convex, rounded, or flattened features and/or combinations thereof. Accordingly, an embodiment of the medical device of the present invention may be able to provide focal lesions, circular lesions, linear lesions, circumferential lesions, and combinations thereof. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.