Abstract:
An esophageal catheter for displacing and fixing the position of the esophagus in relation to the atrium of the heart is composed of a long flexible tube to be inserted into the esophagus. A control wire is associated with the tube to change the shape of the catheter and displace the esophagus relative to the heart to reduce the risk of an esophageal fistula resulting from atrial RF ablation.

Description:
FIELD OF THE INVENTION 
   This invention relates to heart surgery and more particularly to RF (radio frequency) catheter ablation of atrial fibrillation (AF) and other atrial arrythmias. 
   BACKGROUND OF THE INVENTION 
   The goal of the surgical treatment of atrial fibrillation is to block or interfere with impulses radiating from ectopic foci inside the pulmonary veins that triggered atrial fibrillation. Among the first intra-heart surgical treatments for atrial fibrillation was demonstrated by the Leipzig group in a procedure referred to as, endocardial linear lesion, to connect the pulmonary vein to the mitral annulus during open heart surgery. 
   The Mayo Clinic is known for another open heart surgical procedure, termed the Maze procedure, in which multiple cuts are created in the atrial muscle in a maze pattern. These cuts produce scar tissue which does not carry electrical impulses and as a result the stray impulses causing atrial fibrillation are eliminated producing a normal coordinated heartbeat. 
   More recently, cardiology specialists called, electrophysiologists, have used cardiac catheters to ablate the heart tissue without the need for open heart surgery. In this procedure, an RF catheter is inserted into the atrium and a series of ablations or burns are performed around the mouth of the pulmonary vein and the left atrial wall. The ablations also form scar tissue blocking stray electrical impulses to restore normal heartbeat. During RF catheter ablation, lesion depth, extension and volume are related to the design of the ablation electrode and the RF power delivered. 
   Among the complications that may arise is pulmonary vein stenosis, if the ablations are too close to the mouth of the pulmonary vein. Another serious and, possibly fatal, complication is atrial-esophageal fistula caused by thermal penetration of the walls of the atrium and esophagus. The atrial-esophageal fistula can lead to pericarditis, or fluid between the outer wall of the heart and the pericardium restricting the heartbeat, hemorrhage, or other life threatening conditions. 
   The atrial-esophageal fistula or hole in the esophageal wall may result, in part, from simple anatomy and the RF power needed to develop ablations, as well as the design of the catheter electrode tip and other contributing factors, such as movement of the esophagus during the procedure. 
   The esophagus is located at the center of the posterior mediastinum and is separated from the atrium only by the pericardial sac and/or a thin layer of fatty tissue and may be in contact with the atrium. The left atrium wall thickness is about 2-4 mm and the esophagus thickness is about 2-3 mm. The esophagus is supported at it&#39;s upper end near the trachea and transits the diaphragm to connect with the stomach. The esophagus is supported at its lower end by the diaphragm. The thoracic portion of the esophagus between the trachea and the stomach is mobile and loosely restrained only by soft tissue. This allows the esophagus to move in response to swallowing food, cardiac and lung movement, as well as upper body movements. This flexibility of the esophagus complicates the problem of avoiding atrial-esophageal fistula. 
   DESCRIPTION OF THE PRIOR ART 
   Currently, several techniques are employed by the electrophysiologists to reduce the likelihood of an atrial-esophageal fistula developing during the RF atrial ablation. The most comprehensive technique involves a pre-operative procedure of developing a 3-D map of the operative field by CT scan or MRI displayed with real time 3-D electroanatomical maps to reveal the cardiac anatomical relationships. This mapping system may or, may not, be used with a contrast medium in the esophagus to better locate the position of the esophagus. The mapping systems allow the ablations to be precisely plotted on the atrium wall. The locations of some ablations may be changed or adjusted because of anatomical considerations. Contrast placement in the esophagus may be used independently of CT/MRI to allow real time visualization of the esophagus. 
   In some cases, the area of the atrium traversed by the esophagus is avoided during the ablation procedure when the outcome is not comprised. 
   The electrical energy of the electrode can be controlled, eg., reducing power in the vicinity of the esophagus. However, the adjustment is not significant. 
   Therefore, what is needed in the art is a device for controlling the location of the esophagus in relation to the atrium during RF catheter ablation. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is a primary objective of the instant invention to provide an esophageal catheter capable of moving and restraining the esophagus away from certain areas overlying the posterior portion of the heart. 
   It is a further objective of the instant invention to provide a naso-gastric catheter capable of laterally displacing an intermediate portion of the esophagus along the longitudinal axis. 
   It is yet another objective of the instant invention to provide a control wire for insertion through an esophageal catheter to control the longitudinal shape. 
   It is a still further objective of the invention to provide an esophageal catheter with embedded control wires for changing longitudinal direction. 
   It is yet another objective of the invention to utilize the support provided to the esophagus in the area of the trachea and the area of the diaphragm to anchor the ends of the esophagus and induce lateral movement of the esophagus in the mid-portion dorsal to the atrium. 
   Other objects and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a representation of the heart and esophagus showing a pattern of optimal ablation lesions; 
       FIG. 2  is a representation of the heart and esophagus of  FIG. 1  with an esophageal catheter inserted; 
       FIG. 3  is a representation of the heart and esophagus of  FIG. 1  with the control wires changing the direction of the catheter and esophagus; 
       FIG. 4  is a representation of one of the control wires of  FIG. 3 ; 
       FIG. 5  is a representation of another of the control wires of  FIG. 3 ; 
       FIG. 6  is a cross section of another esophageal catheter with control wires in the sidewall; 
       FIG. 7  is a cross section of the esophageal catheter with the control wire in the lumen; and 
       FIG. 8  is a partial longitudinal cross section of another embodiment of the esophageal catheter and control wire. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , a posterior view of the patient shown with the heart  11  in phantom lines lying in front of the esophagus  10 . The esophagus is supported by the trachea  21  at one end and by the diaphragm  22  at the other end. Normal anatomical variation in the exact location of the atrium-esophageal relationship does occur. The right pulmonary vein  12  enters the atrium  13  and the desired pattern of optimal ablation lesions  14  are shown as they might appear in the mapping procedure. When viewing these proposed ablation lesions  14 , either pre-operatively or intra-operatively, the surgeon may decide to change the location of some of the ablations because of the proximity to the esophagus  10 . If a particular ablation(s) is considered necessary regardless of the location of the esophagus, the RF power to the electrode may be reduced. 
   To manage the surgical field to eliminate the possibility of an esophageal fistula, an esophageal catheter or tube  15  is inserted through the mouth or nose into the esophagus  10  and through the length of the esophagus past the diaphragm  22 , as shown in  FIG. 2 . The catheter  15  may include a radiologic marker or markers  16  to improve visualization of the location of the catheter  15  and esophagus  10 . 
   To move the esophagus laterally, in the surgical field, and to fix the displaced portion of the esophagus beyond the area of thermal lesions, a control wire  17  is inserted through the lumen of the catheter  15 . As shown in  FIGS. 4 and 5 , the control wires have a preformed curved intermediate portion  18 . As the curved portion moves through the catheter, the catheter is displaced along it&#39;s longitudinal axis to follow the curve of the control wire. The control wire may be round, flattened, single strand or multi-strand, such as a guide wire. The control wire  17  is manipulated within the catheter to place the curved portion  18  near the atrium and to rotate the control wire to displace the catheter and esophagus away from the ablation lesions  14  laterally and posteriorly as the patient&#39;s anatomy permits, as shown in  FIG. 3 . Depending on the relative size of the catheter lumen  21  and the control wire, a second control wire  19  may be used having a similar curved portion  20 . The control wires  17  and  19  may be used in conjunction with each other to produce one curve or, independently, to form the catheter in other shapes. The use of separate control wires allows the catheter to remain in place, once inserted, and to be bent in the area dictated by the anatomy of each individual patient. As shown in  FIG. 3 , the curvature of the catheter is left lateral however, the control wires may be manipulated to force the esophagus in the dorsal direction away from the heart or to the right laterally. 
   As shown in  FIG. 6 ,  FIG. 7  and  FIG. 8 , the catheter  15  has control wires attached to the sidewall at discrete points  26  along the catheter. By differential movement of the control wires and the catheter, respectively, as shown in  FIG. 8 , the longitudinal shape of the catheter can be changed. In  FIG. 8 , either the plunger  23  or the barrel  24  is moved relative to the other, thereby shortening one member in relation to the other and causing the catheter to bend in the mid-portion. In  FIG. 6 , separate control wires  17  and  19  located in the sidewall of the catheter  15  can be moved to bend the catheter in different directions. In  FIG. 7  the control wire  25  is located in the lumen  27  and attached to the side wall at  26 . The catheter may be rotated in the esophagus to move the esophagus, as desired. 
   Also, control wires made from shape retaining memory materials, such as Nitinol, can be used. These wires are pre-formed at a certain temperature with the desired curve and then cooled and straightened. When the catheter is placed in the body, the wires assume their original curved shape as they become heated. 
   All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. 
   It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
   One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.