Abstract:
A catheter design for ablating AF based upon the true anatomy of the left atrium and especially the left atrial pulmonary vein junction, obtained by unique imaging techniques. The catheter design will conform to the true anatomy of the anatomical structures to be ablated and takes into account the complex 3-D geometry of the left atrium and the various sizes and shapes of the pulmonary veins and their openings into the left atrium.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present invention is based on and claims priority to U.S. Provisional Patent Application Ser. No. 60/354,561 filed on Feb. 5, 2002. 

   FIELD OF THE INVENTION 
   The present invention generally relates to a catheter design which can be used to treat atrial fibrillation (AF). More specifically, the present invention relates to a catheter design that can be used to electrically isolate pulmonary veins from the left atrium and conform to the true anatomy of the pulmonary veins based on images obtained using computed tomographic (CT) imaging techniques. 
   BACKGROUND OF THE INVENTION 
   A short discussion of atrial fibrillation, or AF, and its mechanisms is useful in understanding the complexity of the problem and how the method and apparatus of the present invention will help treat this arrhythmia more effectively. 
   Atrial fibrillation, which is an arrhythmia in which the atria (upper chambers of the heart) stop contracting as they fibrillate, is the most common of the heart rhythm problems. Present data suggests that AF is the most common arrhythmia-related cause of hospital admissions. Patients with AF have a high incidence of medically significant complications such as stroke and congestive heart failure. Premature atrial contractions can act as triggers and initiate paroxysms of AF. These premature atrial contractions have been shown to predominantly originate in the pulmonary veins from the left atrium. Since infrequent and nonreproduceable premature atrial contractions limit the utility of ablating trigger sites, a variety of surgical and catheter techniques have been used to isolate the pulmonary veins from the left atrium. 
   One of the surgical techniques used to treat AF involves the use of radio-frequency waves (modified electrical energy) to create small scars on the heart&#39;s surface near the connection between the pulmonary veins and the left atrium. The small scars created by the radio-frequency waves stop the erratic impulses of atrial fibrillation by directing the impulses to follow a normal electrical pathway through the heart. Typically, this type of surgical procedure is performed through a chest incision. Surgeons use specially designed instruments to deliver radio-frequency waves to the abnormal tissue, typically during open heart surgery performed for other reasons, such as a mitral valve repair. Although this type of surgical technique is effective when the patient is undergoing open heart surgery for another reason, catheter-related treatment methods are more practical when the patient does not require the invasive open heart surgery for other reasons. 
   One of the catheter techniques involves the application of radio-frequency energy at areas showing double potentials suggestive of sites capable of conducting between the left atrium and the pulmonary veins. The currently crude three-dimensional reconstruction of the left atrium, the inability of the physician to visualize the pulmonary vein ostia from inside, the varying size of the pulmonary veins and thus the pulmonary vein ostia, the difficulty in keeping the mapping catheter stable at the pulmonary vein ostia sites, all make current approaches to mapping using fluoroscopically-guided imaging techniques cumbersome, lengthy and inadequate. 
   Because of these limitations, radio-frequency ablation is much less successful than surgery, especially in patients with persistent atrial fibrillation. In fact, less than 20 percent of patients undergoing radio-frequency catheter ablation for AF benefit from this approach. 
   A number of modalities presently exist for medical diagnostic imaging. One such approach utilizes computed tomographic imaging to delineate the precise anatomy of an organ. Once the left atrium and pulmonary veins are visualized, a catheter design which will conform to the anatomy of the different pulmonary veins will help isolate the pulmonary veins more precisely and easily and assure the same success rate for the radio-frequency approach as for surgery. 
   SUMMARY OF THE INVENTION 
   One aspect of the present invention is a catheter designed to be used in planning cardiac interventional procedures to treat AF. The catheter design is based upon the precise anatomy of the left atrium obtained using a medical imaging system, such as CT imaging, for left atrial mapping. 
   In accordance with the present invention, three-dimensional images of the left atrium and endocardial or navigator (inside views) of the left atrium are used as a guide to design a catheter that will conform to the anatomical structures which figure prominently in the treatment of AF and other heart rhythm problems. The catheter design of the present invention is utilized with a 3-D image of the left atrium created by using predetermined protocols. Endocardial (inside) or navigator views of the left atrium will then be obtained and stored on a transferable medium. The acquired database will be transferred to the computer workstation of the interventional system and registered with the interventional system over which the mapping and ablation catheter is visualized. 
   Using a transseptal catheterization, which is a standard technique for gaining access to the left atrium, the catheter of the present invention is introduced into the left atrium. The catheter consists of a main catheter shaft and a tip section that is capable of bidirectional steerability. The distance from the transition point from the catheter shaft to the outer tip of the tip section may vary to accommodate different atrial sizes. The catheter shaft length may also vary depending upon the height of the patient and the size of the left atrium. 
   The catheter of the present invention includes a recording and ablation catheter embedded in the main catheter shaft. The recording and ablation catheter includes an electrode section having three 5 mm electrodes. The electrode section of the ablation and recording catheter comes out of the catheter shaft in a circular fashion, such that one, two or all three electrodes may be out of the shaft. As the electrode section of the recording and ablation catheter is moved further and further out of the shaft, the pre-stressed curve of the electrode section causes the catheter to move in a circular fashion around the pulmonary vein ostium. Intracardiac recordings and real-time visualizations of the catheter determine which electrodes can be used for ablation. One, two, or all three electrodes can be used simultaneously for ablation. 
   The design of the steering handle of the catheter includes actuator controls that ensure a proper curve of the catheter shaft and the degree of protrusion of the catheter from the catheter shaft. The catheter steering handle further includes locking mechanisms to lock the catheter shaft and catheter in place. 
   Further aspects of the invention are disclosed herein. The above presentation and its advantages and the various features of the concept of this invention will be appreciated further from the drawings and the detailed descriptions which follow. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the present invention. 
     In the drawings: 
       FIG. 1  is a conceptual illustration of the method of the present invention to use a specifically designed catheter for the ablation of atrial fibrillation, including the 3-D modeling of the left atrium and pulmonary veins using a CT image; 
       FIG. 2  is a three-dimensional CT image of the left atrium and pulmonary veins; 
       FIG. 3  is a view of the steering handle for the catheter shaft and mapping and ablation catheter of the present invention; 
       FIGS. 4   a – 4   b  are a side view of the catheter shaft of the present invention and illustrating the movement of the catheter shaft in a bidirectional plane; 
       FIGS. 5   a – 5   b  are a side view illustrating the mapping and ablation catheter of the present invention as it is deployed from the catheter shaft; 
       FIGS. 6   a – 6   b  are a detailed view of the mapping and ablation catheter of the present invention illustrating three mapping and ablation electrodes; 
       FIG. 7  is a view of the deployment of the catheter shaft in the left atrium as imposed over a three-dimensional CT image; and 
       FIGS. 8A-8D  is a sequential illustration of the movement of the mapping and ablation catheter in a sequential fashion around the pulmonary vein ostium with the front end of the left atrium open to illustrate the pulmonary vein ostia and their orientation to the left atrium. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring first to  FIG. 1 , thereshown is a diagram illustrating the overview of an exemplary process in which a cardiac CT scan is performed to create a 3-D image of the left atrium of a patient&#39;s heart. Once the 3-D image of the left atrium is acquired, the image can be used for interventional planning for such things as atrial fibrillation (AF) ablation. The volume of patient data acquired using the CT imaging is optimized for the left atrium and cardiac gating is performed to acquire consecutive axial images from the same phase of the cardiac cycle. Once the CT imaging has been completed, a 3-D reconstruction of the left atrium is created. 
   Once the 3-D reconstruction of the left atrium is created, a segmentation process is used to extract the inner surface of the left atrium, as illustrated in  FIG. 2 . As shown in  FIG. 2 , the topographic contours of the left atrium can be readily viewed, as well as the ostium between two pulmonary veins and the left atrium. The 3-D and inner views of the left atrium are stored into a file and transferred to a computer workstation of the interventional system. Once the information is transferred to the computer workstation, the information is registered and viewed by an interventionalist. 
   The cardial CT imaging in accordance with the present invention provides information for AF interventional planning (i.e. an accurate rather than a crude 3-D geometric representation of the left atrial-pulmonary vein junction and other structures). The increased accuracy of the geometry of these structures, in combination with a catheter designed in accordance with the present invention, allows the interventionalist to identify and quickly ablate the relevant structure. 
   The present invention is directed to a catheter design that conforms to the anatomy of the left atrial-pulmonary vein junctions and other important structures such as the left atrial appendage and the left atrial wall between the right and left pulmonary veins. The catheter design of the present invention eliminates the flaws in current techniques used in AF ablation. Presently available catheter designs do not conform to the anatomy of the left atrial-pulmonary vein junction. Additionally, this junction is difficult to precisely identify using current fluoroscopic and echocardiographic techniques. 
   Referring now to  FIG. 3 , thereshown is a catheter  10  of the present invention. The catheter  10  includes a steering handle  12 , a catheter shaft  14  and an internal mapping and ablation catheter  16 . The internal wiring and controls for the catheter, and specifically the ablation catheter  16 , are not shown but will be described in detail below. The catheter shaft  14  extends from the steering handle  12  and encloses the mapping and ablation catheter  16 . The catheter shaft  14  provides support for the mapping and ablation catheter  16  as the catheter shaft is inserted into the patient using a standard technique for gaining access to the patient&#39;s left atrium, such as transseptal catheterization. It is contemplated by the inventor that at least three different catheter shaft lengths can be available depending upon the height of the patient and the size of the left atrium. 
   Referring now to  FIGS. 4   a  and  4   b , the catheter shaft  14  extends to an outer tip  18 . In the preferred embodiment of the invention, the outer tip  18  of the catheter shaft  14  is radio-opaque such that it can be visualized in real-time over the x-ray fluoroscopy. 
   As illustrated in  FIG. 4   a , the catheter shaft  14  extends along a central axis  20 . As illustrated in  FIG. 4   a , the tip section  22  is rotatable about the central axis  20 , as illustrated by the broken lines in  FIG. 4   a . The rotation of the tip section  22  about the center axis  20  allows the interventionalist to control the orientation of the catheter when inserted into the left atrium, as will be described below. 
   Referring back to  FIG. 3 , an upper actuator  24  is included on the catheter handle  12  for controlling the rotation of the catheter shaft tip section  22  about central the axis  20  illustrated in  FIG. 4   a . Thus, the operator can control the rotation of the tip section  22  by rotating the upper actuator  24 . 
   As illustrated in  FIG. 4   b , the tip section  22  of the catheter shaft  14  can be moved up to a 60° angle above the original bidirectional base plane  21  that passes through the transition between the main body  23  and the tip section  22 , as shown by reference numeral  22   a . Further, the tip section  22  is capable of a 300° angle curve downward relative to the base plane  21 , as illustrated by the dashed lines and reference character  22   b . The rotation of the catheter shaft  14  about the center axis  20 , as well as the angled movement of the tip section  22  relative to a bidirectional plane  21 , allows the catheter shaft to be moved both posteriorly or anteriorly from the original plane as desired. 
   In the embodiment of the invention illustrated, the tip section  22  may vary from 1.5 inches to 3 inches depending upon the size of the patient in which the catheter of the present invention is being used. The bidirectionality of the catheter shaft, the different curve sizes, and the ability to bend the catheter up to a 300° angle downward and 60° upward from the bidirectional plane allows the shaft to be oriented towards the appropriate pulmonary vein once inserted into the left atrium. 
   Referring back to  FIG. 3 , a lower actuator  26  on the steering handle  12  controls the angled movement of the tip section  22 , as illustrated in  FIG. 4   b . Specifically, rotation of the actuator  26  in a clockwise direction results in movement of the catheter up to a 300° angled curve to the position shown by reference numeral  22   b . If the lower actuator  26  is rotated in a counter-clockwise direction from a neutral location, the catheter tip section  22  is movable up to a 60° angle from the original bidirectional base plane  21 , as shown by reference numeral  22   a . Thus, rotation of the lower actuator  26 , in connection with the rotation of the upper actuator  24 , allows for the desired orientation of the tip section  22 . 
   Referring back to  FIG. 3 , the steering handle  12  includes a locking mechanism  28  for the movement of the catheter shaft  14 . The locking mechanism  28  secures the catheter shaft in a desired curve or position once the proper orientation of the catheter shaft has been achieved through movement of the upper actuator  28  and the lower actuator  26 . 
   As described previously, the catheter  10  of the present invention includes an internal mapping and ablation catheter  16  within the catheter shaft  14 . Referring now to  FIG. 6 , thereshown is a detailed view of the mapping and ablation catheter  16  of the present invention. As illustrated in  FIG. 6 , the mapping and ablation catheter  16  includes an electrode section  30  that includes three electrodes  32 . The electrodes  32  are spaced from each other by spacer sections  34 . In the preferred embodiment of the invention, each of the electrodes is approximately 5 mm in length while the interelectrode spacing is approximately 2 mm. 
   In the preferred embodiment of the invention, each of the electrodes  32  is configured to ablate heart muscle. The ablation can be carried out using various types of energy sources, such as microwave, laser, cryothermy, ultrasound and conventional radio-frequency signals. Each of the electrodes  32  is independently operable such that either one, two or three of the electrodes can be used to ablate heart tissue during a procedure performed using the catheter  16  of the present invention. 
   Referring now to  FIG. 6   b , each of the electrodes  32  includes a temperature recording site  36  and a bipolar electrocardiogram recording site  38 . The temperature recording site  36  allows the temperature to be recorded from the tip of each electrode  32  while the bipolar electrocardiogram recording site  38  allows an electrocardiogram to be determined in a bipolar fashion. 
   Referring now to  FIGS. 5   a  and  5   b , thereshown is the movement of the electrode section  30  of the mapping and ablation catheter  16  out of the catheter shaft  14 . As illustrated in  FIG. 5   a , only the first electrode  32  extends past the tip  18  of the catheter shaft  14 . As the mapping and ablation catheter  16  is moved out of the catheter shaft  14 , the catheter  16  comes out in a circular fashion as shown in  FIG. 5   b . The circular shape of the electrode section  30  is controlled by the pre-stressed curve of the electrode section  30 . The curvature of the electrode section  30  allows the electrode section  30  to move along the curved inner wall of the pulmonary vein. Depending upon the electrode or electrodes in contact with the atrial tissue, one, two or all three electrodes can be used to ablate the heart tissue. 
   When fully deployed, the proximal and distal ends of the catheter  16  are adjacent to each other as illustrated in  FIG. 5   b . Additionally, the catheter  16  is at a right angle to the catheter shaft  14  such that the electrode section  30  can be used to ablate a ring around the junction between the pulmonary vein and the atrial wall. As illustrated in  FIG. 5   b , a non-recording and ablating section  38  of the mapping and ablation catheter  16  provides for the required curvature of the mapping and ablation catheter  16 . The non-recording section  38  does not include any electrodes and thus does not function in the recording or ablation process. 
   Referring back to  FIG. 3 , the steering handle  12  includes an upper actuator  40  that is used to control the movement of the mapping and ablation catheter  16  into and out of the catheter shaft  14 . The upper actuator  40  is moveable both in a longitudinal direction, as illustrated by arrow  42 , and is rotatable about a longitudinal axis, as illustrated by arrow  44 . When the upper actuator  40  is moved in the direction illustrated by arrow  42 , the mapping and ablation catheter  16  is slowly extended from the catheter shaft  14 , as illustrated in  FIG. 5   a . When the upper actuator  40  is rotated as illustrated by arrow  44 , the curvature of the ablation catheter  16  is adjusted. It is contemplated that three separate curves of 10 mm, 15 mm and 20 mm can be created by rotating the upper actuator  40 . The different curvatures of the ablation catheter  16  allows the ablation catheter to be adjusted for different patient sizes and thus different pulmonary vein dimensions. 
   Once the mapping and ablation catheter  16  has been extended the required distance and achieved the desired curvature, an upper locking mechanism  46  can be actuated to lock the mapping and ablation catheter  16  into a desired configuration. 
   Referring now to  FIG. 7 , thereshown is the introduction of the catheter shaft of the present invention into the left atrium using the transseptal approach.  FIG. 7  shows the posterior view of the left atrium with the right pulmonary veins on the right side and the left pulmonary veins on the left side. As illustrated, the catheter shaft  14  can be bent at different curve angles and orientations depending upon the pulmonary vein that needs to be accessed. Once the catheter shaft has been bent to the desired orientation, the mapping and ablation catheter  16  can be extended from the outer tip of the catheter shaft to ablate the desired areas. 
   Referring now to  FIG. 8 , thereshown is the introduction of the catheter shaft  14  and the extension of the mapping and ablation catheter  16  therefrom to ablate a ring around the junction of the pulmonary vein and the atrium wall. As illustrated in  FIG. 8   d , once the ablation catheter  16  has been fully extended, the desired areas have been ablated as illustrated by the dark ring  50  of  FIG. 8 . 
   While the invention has been described with reference to the left atrium and AF, it is understood that it could be utilized for other rhythm problems and other chambers. Other imaging techniques such as magnetic resonance imaging or x-ray fluoroscopy, could be used in place of CT. 
   Similarly, although the concepts of the invention introduced above are discussed with respect to cardiac imaging and ablation, it is understood that the method of acquisition of data and ablation is not limited to cardiac and medical applications but may be utilized in non-cardiac applications such as ablation in other organs and structures. Also, the methodology described may be utilized in non-medical applications. Delivered energy may be understood to mean radio-frequency current, microwave energy, cryo or other forms of energy. 
   In addition, while the invention has been described with reference to its exemplary embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the scope of the invention. In addition, changes and modifications may be made in order to adapt to a particular situation or material without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best method for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 
   Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.