Abstract:
A device and system are disclosed for selective inflation of an inflatable body, such as a balloon, received through an oral cavity and into the esophagus of a patient. The inflatable body is operably coupled to a pressurized fluid source. The inflatable body has a relatively flexible portion and a relatively inflexible portion. When pressurized fluid is delivered to the body to inflate the body, the flexible portion expands more than the inflexible portion, resulting in asymmetrical expansion and movement of the esophagus away from the ablation site to avoid accidental injury while performing a procedure on the patient&#39;s left atrium. This movement may be opposite from or directly away from the heart or, alternatively, may be sideways relative to the heart to a location in which the esophagus is interposed between the ablation site and the phrenic nerve. The supplied fluid may be radio-opaque liquid to allow for imaging thereof to assist in positioning the balloon. The liquid may additionally be relatively cool as compared to the patient&#39;s body temperature so serve as a heat sink against heat applied to surrounding areas.

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 61/272,564, filed on Oct. 6, 2009, the entire contents of which is hereby expressly incorporated by reference into the present application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention generally relates to atrial ablation procedures. More particularly, the invention relates to an intra-esophageal balloon system that is configured to move a patient&#39;s esophagus away from an ablation site to prevent accidental damage to the esophagus during the performance of an ablation. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Atrial fibrillation is the most common human arrhythmia. The incidence of atrial fibrillation increases with the age of the patient, and thus, the incidence of atrial fibrillation is becoming more prevalent as the average lifespan continue to increase. Atrial fibrillation is associated with increased morbidity and mortality and, in particular, a general decrease in quality of life for those afflicted with atrial fibrillation. Patients are at an increased risk of stroke unless they are treated adequately with anticoagulants. Anticoagulant treatment however, increases a patient&#39;s risk of bleeding, which carries with it its own set of dangers. Medications currently available for treating atrial fibrillation have proven to be only moderately effective in decreasing the incidence of recurrent atrial fibrillation, and these mediations do not decrease the patient&#39;s risk of having a stroke. 
         [0006]    One method of treating atrial fibrillation has been to perform ablation of selected areas of the left atrium. There is evidence to suggest that ablating these areas of the left atrium serves to cure or prevent further incidences of atrial fibrillation, which thereby has shown to reduce the risk of stroke and reduce the necessity of anticoagulant therapy. Typically, ablations of this type are carried out via an intravascular catheter using radiofrequency or microwave energy to cause thermal damage to the selected parts of the left atrial tissue. 
         [0007]    The posterior wall of the left atrium is particularly targeted for ablation because the pulmonary veins enter the atrium at this area of the left atrium. Thus, encircling the pulmonary veins with continuous rings of lesions is common in this procedure. The esophagus may however, be positioned so as to overlie one or more of these veins, thereby making the desired encirclement difficult or impossible. A significant and lethal complication of atrial fibrillation ablation is the accidental creation of an atrio-esophageal fistula following the development of lesions on the posterior wall of the left atrium. Because the esophagus is generally closely positioned to the posterior wall of the left atrium, thermal injury may be communicated to the esophageal wall resulting in disruption of the wall and formation of the atrio-esophageal fistula. 
         [0008]    In addition to the foregoing, fractionated electrograms and vagal plexi are also frequently present on the posterior wall of the left atrium. These are also common targets of atrial fibrillation ablation. Again, the location of the esophagus may hinder application of a sufficient energy to successfully ablate enough tissue of the left atrium to prevent recurrence of atrial fibrillation. Further, the esophagus is a mobile structure. Thus, peristaltic movements thereof may cause the esophagus to move and change its position relative to the left atrium. Advanced intracardiac ultrasound systems that are used to locate the esophagus to prevent accidental damage thereto are often incapable of accounting for or tracking such movements, thus rendering these relatively complex and expensive systems ineffective. Fluoroscopic evaluation of the esophagus is also used to determine the position of the esophagus during ablation procedures like this however; such methods provide only two-dimensional information and thus may lead to misreading of the position of the esophagus as it relates to the left atrium. 
         [0009]    In addition to the foregoing disadvantages, left atrial ablation of this kind also experiences a great deal of unwanted heat dissipation from the ablation catheter tip. Upon application of the catheter tip to the ablation site, the tissue immediately contiguous to the tip is heated, thereby disrupting cellular function thereof. A sufficient amount of heat must be generated to coagulate and denature the proteins in the myocardial cells. If a heat sink is present in close approximation of the ablation site, generating sufficient heat becomes difficult if not impossible using presently available RF generators. For instance, arteries in close approximation to the ablation site experience rapid blood flow sufficient to conduct heat away from the area rapidly. 
         [0010]    Other methods, such as cryoablation and high frequency ultrasound, are still considered experimental and are associated with particular disadvantages specific to these types of ablation. 
         [0011]    It has recently been discovered that successful atrial fibrillation ablation may require the introduction of lesions near the location of the inferior right pulmonary vein, which is located in close proximity to the phrenic nerve. Thus, it is has become more common for accidental injury to the phrenic nerve to occur. The phrenic nerve is responsible for operation of the diaphragm, and thus, injury to the phrenic nerve can be quite catastrophic. Thus a method or system for preventing such injuries is deemed highly desirable. 
         [0012]    The need therefore exists to provide a device for carrying out atrial fibrillation ablation of the left atrium that does not suffer from the foregoing disadvantages. In particular, a device for moving the esophagus away from the left atrium of the heart is desired. 
       SUMMARY OF THE INVENTION 
       [0013]    In accordance with a first aspect of the invention, a system for safely performing left atrial fibrillation ablation is provided. In particular, the system according to the invention is configured for selective movement of the esophagus away from the heart and the left atrium thereof such that the necessary areas of the left atrium may be ablated to prevent recurrent atrial fibrillation. By moving the esophagus from the ablation site, the esophagus is maintained at a safe distance from the ablation site and in particular the ablation RF catheter such that the esophagus is not accidentally injured during the performance of the ablation procedure. 
         [0014]    The system of the invention includes an inflatable body, most typically a balloon, constructed primarily of a flexible material adapted for insertion into a patient&#39;s body through the oral cavity of the patient and into the esophagus. The balloon expands asymmetrically upon inflation to force the esophagus which contains the balloon to also bend and move away from the posterior wall of the atrium. Bending of the esophagus may be directed to also push the phrenic nerve away from the inferior pulmonary vein. The balloon may be inflated by a fluid such as air or another inert gas or, more preferably, by a liquid. 
         [0015]    Asymmetrical expansion may be facilitated by forming one strip or portion of the balloon from a material that has a relatively flexible portion and a remainder of the balloon from a relatively inflexible portion when viewed in transverse cross section. For example, a portion adjacent the patent&#39;s heart could be made relatively inflexible through the use of a stiffening strip. Because the stiff area of the balloon does not expand as much as the remainder of the balloon, the area of the esophagus adjacent thereto is not contacted by the balloon at this area. Thus, the inflexible portion of the balloon preferably is positioned in the esophagus adjacent the left atrium of the heart such that this portion of the esophagus remains a sufficient distance away from the left atrium such that, upon inflation of the balloon, the balloon is inflated and the esophagus bends away from the area of the left atrium to be ablated 
         [0016]    The system may include a relief valve for selective expulsion of excess fluid therefrom. 
         [0017]    A liquid used to inflate the balloon may be radio-opaque so as not to interfere with imaging of the esophagus and/or heart with X-ray or fluoroscopic examination and/or may be cooled to act as a heat sink during ablation. 
         [0018]    In one embodiment of the invention, a number of electrodes are embedded, attached, or otherwise coupled to the wall of the balloon and interconnected by way of a conductor to an electrical power source. The electrodes may communicate with a 3D mapping system such that the location of the esophagus vis-à-vis the electrodes can be determined such that the operator may assess the position of the esophagus while performing the ablation procedures. In addition to or instead of the electrodes, one or more magnetic dipoles may be provided in communication with a magnetically operated 3D mapping system to operate in much the same manner. One or more temperature sensors also may be provided for monitoring the effects of the ablation procedure on the esophagus. 
         [0019]    Various other features, embodiments and alternatives of the present invention will be made apparent from the following detailed description taken together with the drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration and not limitation. Many changes and modifications could be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    In the Drawings: 
           [0021]      FIG. 1  is a schematic illustration of a patient having an intra-esophageal balloon system constructed in accordance with a preferred embodiment the invention inserted into the patient&#39;s esophagus; 
           [0022]      FIG. 2  is a partially cut away isometric view corresponding to  FIG. 1 ; 
           [0023]      FIG. 3  is a side elevation view of part of a balloon of the intra-esophageal balloon of the system of  FIGS. 1 and 2 , showing the balloon in a deflated state; 
           [0024]      FIG. 4  is a side el elevation view of the balloon of  FIG. 3 , showing the balloon in an inflated state; 
           [0025]      FIG. 5  is a side sectional elevation view of the balloon in its inflated state of  FIG. 4 ; 
           [0026]      FIG. 6  is an end sectional elevation view of the balloon of the invention; and 
           [0027]      FIG. 7  is a schematic representation of the intra-esophageal balloon system of  FIGS. 1 and 2 . 
       
    
    
       [0028]    Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, and in which: 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    Referring now to the drawings, and initially  FIG. 1 , a schematic illustration of a portion of the internal organs of a patient  10  is provided with an intra-esophageal balloon system  20  constructed in accordance with a preferred embodiment of the invention inserted therein. Patient  10  has a mouth  12  leading to the esophagus  14 , which then terminates at an opening of the stomach  16 . The esophagus  14  is in close proximity to patient&#39;s heart  18 , placing the esophagus at risk to injury during left atrial ablation. 
         [0030]    The intra-esophageal balloon system  20  is inserted through the patient&#39;s mouth  12  and oral cavity  13  and into the esophagus  14 . In particular, a balloon  22  of the system  20  is positioned within the esophagus  14  at a point substantially lateral to a left atrium  24  of the heart  18 . Balloon  22  comprises a proximal or upper end  26  and a distal or lower end  28  opposite proximal end  26 . Proximal end  26  is interconnected with a tube  30  that extends upwardly through the esophagus  14  and through patient&#39;s mouth  12  to a source of pressurized liquid, shown at  40  in  FIG. 6  and described in detail below. The balloon  22  is designed to expand asymmetrically when inflated by fluid from the source  38 ,  40  ( FIG. 7 ) to bend, distort, or otherwise move the esophagus  14  away from the heart  18  and facilitate left atrial ablation without thermal injury to the esophagus. When inflated in the absence of an obstruction such as in the open air to a pressure of x, the balloon  22  expands at least 5% more, and preferably 15% more on one side of a longitudinal bisector “B” of the balloon  22  than the other side. Balloon  22  may be configured to be inflated to pressures of approximately 8-10 atmospheres. When balloon  22  is inflated, balloon  22  may be 4-7 cm long and less than or equal to 2 cm in diameter, although alternative ranges are envisioned and are within the scope of the present invention. A relief valve  32  is disposed at the distal end  28  of the balloon  22  to prevent its overinflation. The balloon  22  preferably is inflated with a liquid such as saline, admixed with radiopaque contrast material, although air or another inert gas could be used to inflate balloon  22 . 
         [0031]    Referring now to  FIGS. 3-6 , balloon  22  comprises an elongate, relatively narrow balloon constructed of silicone, rubber or a similar flexible material that may be safely introduced into the esophagus. With momentary reference to  FIG. 6 , balloon  22  is generally circular cross-section when uninflated so as to be symmetrical about a longitudinal bisector B, though it is contemplated that the balloon  22  may be more ovoid or have other shapes, so long as the balloon can be inserted into the patient&#39;s esophagus  14  in its deflated state and inflated as discussed below. 
         [0032]    As mentioned briefly above, balloon  22  is configured to expand asymmetrically when inflated so as to distort the esophagus  14  away from the heart  18 . Asymmetrical expansion may be made possible by rendering the balloon circumferentially non-uniformly flexible. This effect is most easily achieved by making at least one side or edge portion of the balloon more or less flexible than at least one other side or edge portion of the balloon. In the illustrated embodiment, this capability is enabled by providing a stiffening strip  34  along a portion thereof. Stiffening strip  34  is constructed of a material that is substantially more rigid than the remainder of the material of which balloon  22  is constructed, such as a relatively hard plastic material. Stiffening strip  34  is mounted on, in, or integrally formed with the remainder of the balloon  22 . Stiffening strip  34  preferably is applied along one relatively narrow portion of balloon  22  at a location at or near the portion of the esophagus  14  that is closest to the patient&#39;s heart  18  and extends lengthwise from proximal end  26  to distal end  28 . Stiffening strip  34  preferably has a width similar to that of an average width of a patient&#39;s esophagus for reasons that will be made apparent from the ensuing description. In particular, stiffening strip  34  may have a width of approximately 1 mm to 2 cm. In particular, as can be best seen in  FIG. 4 , stiffening strip  34  is configured to inhibit or prevent a portion of balloon  22  from expanding during inflation of balloon  22 . Stiffening strip  34  may be a wire or piece of fishing line embedded into or attached to a wall of balloon  22 . In one embodiment, stiffening strip  34  has a radiopaque marker affixed to it to identify the location of the stiffening strip  34  when using imaging equipment. In this manner, balloon  22  may be oriented under fluoroscopy or other imaging techniques to ensure proper positioning of stiffening strip  34  with respect to the esophagus  14 . 
         [0033]    As will be explained in detail, balloon  22  is configured to be inflated by way of a fluid or preferably a liquid that is introduced through tube  30 . As the liquid is introduced into balloon  22 , balloon  22  begins to inflate and expand around the portions constructed from the flexible material. On the other hand, the portion of balloon  22  incorporating the stiffening strip  34  will expand less than the remainder of the balloon, if at all. The resultant inflation of balloon  22  in a non-uniform or asymmetrical manner causes the balloon  22  to bend or move the esophagus  14  away from the patient&#39;s heart. The bending increases progressively from the ends of the balloon towards its center such that esophageal distortion is maximized at or near the ablation site. 
         [0034]    Other mechanisms could be used instead of or in addition to the stiffening strip to cause asymmetrical inflation. For example, the stiffness of a strip of the balloon extending along the side of the balloon opposite the heart could be reduced, e.g., by reducing its thickness. This “reduced stiffness strip” could be provided instead of or in addition to a stiffening strip at the opposite side of the balloon near the heart. Either strip could have varying stiffening or weakening properties at different locations along its length so as to tailor the location of maximum asymmetrical distortion to a desired portion of the balloon  22 . Either strip could be continuous and extend at least generally the entire length of the balloon as illustrated, or could extend along only along part of the length of the balloon  22 , as a continuous strip or in discrete aligned or misaligned segments. Alternatively, strips of reduced and/or enhanced stiffness could be provided along portion(s) of the balloon that are between the side adjacent the heart and the side opposite the heart, causing the balloon to bend sideways away from the ablation site. 
         [0035]    Relief valve  32  is configured to prevent over-inflation of balloon  22  and resultant possible injury to esophagus  14  by preventing the fluid pressure in the balloon from exceeding a certain predetermined level. Relief valve  32  can be any kind of relief valve generally known in the art that simply opens at the threshold pressure to release the excess liquid into the esophagus  14  and the stomach  16  and that automatically closes when the pressure in the balloon  22  drops below the predetermined pressure. The predetermined pressure preferably is settable using suitable controls located on or in the valve  32 . 
         [0036]    Referring now to  FIGS. 1-7 , opposite the relief valve  32 , balloon  22  is coupled to tube  30  at the proximal end  26  thereof. Tube  30  extends upwardly from balloon  22  through the oral cavity and out of mouth  12 . An inner lumen of balloon  22  is continuous with the lumen of tube  30  to thereby prevent leaking of fluid from tube  30 . Tube  30  preferably is constructed from a relatively flexible medical grade material that is compatible with insertion into a patient and is generally cylindrical in shape. The opposite end of tube  30  is connected to a liquid delivery device, such as a pump  38 , shown schematically in  FIG. 7 . Tube  30  and pump  38  may be coupled by way of a stopcock, valve, or similar such interconnection permitting the selected supply of pressurized fluid to the balloon  22 . A pressure reducer and/or pressure regulator may be provided within the pump  38  or between the pump  38  and the balloon  22  to supplement or even replace the relief valve  32 . 
         [0037]    Pump  38  may be a mechanical or electrical pump. Pump  38  is connected to a reservoir  40  holding a quantity of fluid for delivery to balloon  22 . Preferably, the fluid held in reservoir  40  is cooled to promote esophageal cooling during ablation. In particular, reservoir  40  may hold iced saline or a similar such biocompatible fluid. In a preferred embodiment, the fluid held in reservoir  40  is a radiopaque coolant fluid. As stated briefly above, by using a relatively cool fluid to inflate balloon  22 , the tube  30  and balloon  22  serve to provide a so-called heat-sink to further reduce the risk of perforating or otherwise damaging the esophagus during ablation of the heart  18 . 
         [0038]    The coolant also preferably is radiopaque, such as having been treated with a radiopaque dye of the kind known in the art. In this manner, the esophagus  14  is readily visible using X-rays or other imaging techniques while the fluid is flowing through the tube  30  while tube  30  is inserted into the esophagus  14 . Accordingly, the operator carrying out the procedure is able to view the esophagus  14  during inflation of balloon  22  such that he or she may better observe the location of the esophagus  14  with respect to the heart  18  and, in particular, the left atrium  24  of the heart. Thus, the operator is able to determine whether esophagus  14  has been moved sufficiently far from the heart  18  such that he or she may safely perform an ablation thereon. A radio-opaque fluid also permits the ablation process to be imaged without obstruction from the balloon  22 . 
         [0039]    With particular reference to  FIG. 5 , one embodiment of the invention is shown in which a number of electrodes  42  are inserted into the balloon  22  via tube  30 . In particular, electrodes  42  are disposed within the wall of balloon  22 . Electrodes  42  are coupled to a power source  44  (see  FIG. 7 ) by way of an electrical conductor  46 , which extends upwardly through tube  30  and out of the tube  30  for interconnection with power source  44 . Power source  44  may be an electrical connection assembly of the kind known in the art configured to supply a predetermined amount of electricity to the electrodes  42 . The electrodes  42  by way of conductor  46  may be interfaced with a three-dimensional electro-anatomical mapping system of the kind generally known in the art. In this manner, balloon  22  is capable of being viewed by the operator at a display screen in three-dimensions. Thus, balloon  22  may be viewed in relation to the ablation site on heart  18  at any given time. Alternatively, electrodes  42  may be replaced by magnetic dipoles that allow the location of the balloon  22  to be detected using a magnetically-based three-dimensional mapping system such as CARTO 3D or a similar known system. 
         [0040]    Alternatively, or in addition to, electrodes  42 , balloon  22  may include a number of temperature sensors  47  incorporated into the balloon  22  cavity or wall. The temperature sensors may be interconnected with a temperature monitoring assembly such that the operator may be able to determine a temperature of the balloon  22  during ablation of left atrium  24  of heart  18 . In one embodiment of the invention, if the temperature exceeds a predetermined value, the system  20  of the invention may be configured to automatically respond. For example, system  20  may be configured to respond to prevent a lesion from forming or expanding by flooding the balloon  22  with additional fluid when a particular predetermined temperature is detected. The system  20  may be interfaced with the power source of the ablation mechanism such that the ablation itself is also terminated. 
         [0041]    In operation, balloon  22  is introduced into the esophagus  14  through the oral cavity  13  via the mouth  12  to a location in which it is substantially adjacent to, and preferably parallel with, the left atrium  24  of heart  18 . It is positioned such that the stiffening strip  34  is located adjacent a portion of the esophagus that is relatively close to the heart. Accordingly, when balloon  22  is inflated asymmetrically, the adjacent portion of the esophagus  14  will be moved away from the heart  18 . More specifically, the operator actuates pump  38  and/or related controls to supply pressurized fluid into the tube  30  and thence into balloon  22 . As balloon  22  begins to inflate with the introduction of the fluid thereto, the balloon  22  expands asymmetrically in the direction of the flexible portion  48  thereof. As can be seen from a review of  FIG. 4 , the expansion of the flexible portion  48  of balloon  22  causes the balloon  22  to bow or bend in the direction of the expansion, eventually contacting the sidewall of the esophagus adjacent thereto. As the flexible portion  48  continues to expand, it begins to exert a force on the esophagus  14  such that esophagus  14  moves in a direction of the applied force or away from the heart  18 . In this manner, as can best be seen from  FIG. 2 , the esophagus becomes bowed at or about the region adjacent heart  18  to move directly away from or sideways relative to the left atrium such that the caregiver is free to begin the ablation of left atrium  24  of heart  18 . If the balloon  22  is configured and oriented such that, when the balloon is inflated, the esophagus  14  moves sideways away from the ablation site to interpose itself between the phrenic nerve and the left atrial lesion, the esophagus  14  can provide a barrier or protection against accidental damage to the phrenic nerve. At its maximum point of distortion, the esophagus preferably moves at least 5 mm, and more preferably at least 20 mm, laterally away from its initial position. 
         [0042]    When the fluid used to inflate the balloon is a coolant, the coolant in the balloon  22  also serves as a heat sink sufficient to mitigate or even prevent injury to the phrenic nerve, or balloon  22  may assist in mobilizing the nerve such that it is positioned out of the way of the ablation site. 
         [0043]    After the ablation procedure is complete, the balloon  22  is deflated by operation of the relief valve  32  or otherwise and removed from the esophagus. 
         [0044]    Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the aspects and features of the present invention may be made in addition to those described above without deviating from the spirit and scope of the underlying inventive concept. The scope of some of these changes is discussed above. The scope of other changes to the described embodiments that fall within the present invention but that are not specifically discussed above will become apparent from the appended claims and other attachments.