Patent Publication Number: US-2006009755-A1

Title: Method and system for ablation of atrial fibrillation and other cardiac arrhythmias

Description:
RELATED APPLICATION  
      This application claims the benefit of U.S. Provisional Application No. 60/600,112 filed on Sep. 4, 2003. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to methods and systems for ablation of atrial fibrillation and other cardiac arrhythmias and, in particular, to methods and systems for delivering energy from an outside source to electrodes positioned inside the heart.  
     BACKGROUND OF THE INVENTION  
      Successful ablation of the pulmonary veins, various trigger sites for atrial fibrillation, and other strategic areas within the left atrium through use of a catheter has limitations due to the complex 3D geometry of this heart chamber. One of these limitations involves moving the ablation catheter from one spot to the next within a cardiac chamber. Another difficulty is that inherent limitations of technology, size and geometry prevent multiple electrodes on the catheter from being used to delivery radio-frequency current, either simultaneously or sequentially. Design limitations also contribute to the problem of delivering energy to these different electrodes when positioned inside the heart. There is, therefore, a need for a more innovative delivery process for ablating AF and other heart rhythm problems.  
     SUMMARY OF THE INVENTION  
      One aspect of this invention provides a method for treating a heart arrhythmia in a patient with ablation that includes the steps of (1) positioning a catheter apparatus with multiple electrodes within a chamber of the heart, (2) visualizing the catheter apparatus upon an interventional system such as a fluoroscopic system, (3) navigating the catheter apparatus within this cardiac chamber, and (4) delivering energy to selected electrodes of the catheter apparatus from an external source whereby the electrodes can ablate heart tissue at select locations within the cardiac chamber.  
      In certain preferred embodiments, the energy delivered by the external source is radio-frequency energy in a manner where the electrodes are inductively coupled to the external source. More preferred is where the external source comprises an external patch placed on the patient, the patch being connected to the electrodes through a patient interface unit. The interface unit can selectively choose the electrodes to which the radio-frequency energy is delivered.  
      Another desirable embodiment is where the method includes the steps of obtaining cardiac image data from a digital imaging system, generating a 3D model of the cardiac chamber and surrounding structures from this image data, registering the 3D model with the interventional system, visualizing the catheter apparatus over the registered 3D model upon the interventional system, and navigating the catheter apparatus within the cardiac chamber utilizing the registered 3D model.  
      In a most desirable embodiment, the digital imaging system is a computer tomography (CT) system. Highly desirable is where the heart arrhythmia being treated is atrial fibrillation and the 3D model provides 3D imaging of the left atrium and pulmonary veins.  
      In another aspect of this invention, a system is provided for treatment of a heart arrhythmia in a patient that has a catheter apparatus with multiple electrodes, an interventional system for visualizing the catheter apparatus within a chamber of the heart, and an external source that delivers energy to select electrodes of the catheter apparatus while inside the cardiac chamber to enable these electrodes to ablate heart tissue at certain chosen locations.  
      Preferred embodiments find the energy being delivered is radio-frequency energy such that the electrodes are inductively coupled to the external source to receive delivery of this energy. More preferred is where the system has an external patch placed on the patient as the external source and the patch is connected to the electrodes through a patient interface unit. The interface unit permits the electrodes to be selected that are to receive the radio-frequency energy delivered.  
      Certain desirable embodiments of this system also include a digital imaging system for obtaining cardiac image data, an image generation system for generating a 3D model of the cardiac chamber and surrounding structures from this image data, and a workstation for registering the 3D model with the interventional system and for visualizing the catheter apparatus over the registered 3D model with the interventional system. Most desirable is where the heart arrhythmia is atrial fibrillation and wherein the 3D model is of the left atrium and pulmonary veins. Highly desirable in such systems is where the digital imaging system is a computer tomography (CT) system and the interventional system is a fluoroscopic system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic overview of a system for ablation in treatment of a heart arrhythmia in accordance with this invention.  
       FIG. 2A  depicts 3D cardiac images of the left atrium.  
       FIG. 2B  illustrates localization of a standard mapping and ablation catheter over an endocardial view of the left atrium registered upon an interventional system.  
       FIG. 3  is an illustration of a catheter sheath and catheter with electrodes as it conforms to the 3D geometry of the left atrium.  
       FIG. 4  is a flow diagram of a method for ablation of atrial fibrillation and other cardiac arrhythmias in accordance with this invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  illustrates a schematic overview of an exemplary system for the ablation of heart tissue in a patient with a heart arrhythmia such as atrial fibrillation in accordance with this invention. A digital imaging system such as a CT scanning system  10  is used to acquire image data of the heart. Although the embodiments discussed hereinafter are described in the context of a CT scanning system, it will be appreciated that other imaging systems known in the art, such as MRI and ultrasound, are also contemplated.  
      Cardiac image data  12  is a volume of consecutive images of the heart collected by CT scanning system  10  in a continuous sequence over a short acquisition time. The shorter scanning time through use of a faster CT scanning system and synchronization of the CT scanner with the QRS on the patient&#39;s ECG signal reduces the motion artifacts in images of a beating organ like the heart. The resulting cardiac image data  12  allows for reconstruction of images of the heart that are true geometric depictions of its structures.  
      Cardiac image data  12  is then segmented using protocols optimized for the left atrium and pulmonary arteries by image generation system  14 . It will be appreciated that other chambers of the heart and their surrounding structures can be acquired in a similar manner. Image generation system  14  further processes the segmented data to create a 3D model  16  of the left atrium and pulmonary arteries using 3D surface and/or volume rendering. Additional post-processing can be performed to create navigator (view from inside) views of these structures.  
      3D model  16  is then exported to workstation  18  for registration with an interventional system such as a fluoroscopic system  20 . The transfer of 3D model  16 , including navigator views, can occur in several formats such as the DICOM format and geometric wire mesh model. Information from CT scanning system  10  will thus be integrated with fluoroscopic system  20 . Once 3D model  16  is registered with fluoroscopic system  20 , 3D model  16  and any navigator views can be seen on the fluoroscopic system  20 .  
      A detailed 3D model of the left atrium and the pulmonary veins, including endocardial or inside views, is seen in  FIG. 2A . The distance and orientation of the pulmonary veins and other strategic areas can be calculated in advance from this 3D image to create a roadmap for use during the ablation procedure.  
      Using a transeptal catheterization, which is a standard technique for gaining access to the left atrium, a catheter apparatus  22 , having a mapping and ablation catheter  26  with multiple electrodes  24 , is introduced into the left atrium. Catheter  26  is visualized on the fluoroscopic system  20  over the registered 3D model  16 . Catheter  26  is then navigated real time over 3D model  16  to the appropriate site within the left atrium.  FIG. 2B  illustrates localization of a standard mapping and ablation catheter over an endocardial view of the left atrium registered upon an interventional system.  
      Electrodes  24  of catheter apparatus  22  are capable of both mapping and ablation. Electrodes  24  are spaced apart along catheter  26  of the catheter apparatus  22  and are fabricated from commercially available conductive material such as platinum or copper. Preferably, each electrode  24  will be about 2 mm in size but it will be appreciated that different shapes and sizes can be used as needed. The electrodes are positioned upon a spline made from commercially available material such as stainless steel or nitinol.  
      Catheter  26  has at least  60  electrodes  24  capable of delivering energy; however, more can be used as needed. Catheter sheath  28  of catheter apparatus  22  encloses catheter  26  until sheath  28  has been placed inside the left atrium or other heart chamber of interest. Inside the left atrium, catheter  26  is projected outward from sheath  28 . Catheter  26  expands upon exiting sheath  28  to conform to the 3D anatomy of the left atrium.  
       FIG. 3  illustrates, as an example, the introduction of catheter  26  into the left atrium using the transeptal approach and shows how catheter  26  expands in conformity to the 3D left atrial anatomy.  FIG. 3  presents the anterior view of the left atrium with the right pulmonary veins on the left side and left pulmonary veins on the right side. As illustrated, catheter sheath  28  can be adjusted to achieve different orientations before catheter  26  is deployed depending upon the pulmonary veins or other strategic areas that need to be accessed. Once catheter sheath  28  has been placed in the desired orientation, catheter  26  can be extended outward.  
      The structure and configuration of catheter  26  can vary to accommodate different atrial or other chamber sizes. Such structures include one where catheter  26  expands inside the left atrium into the shape of a basket as shown in  FIG. 3  with multiple electrodes  24  secured along its length.  
      One or more external patches  30  are then positioned on the surface of the body of the patient as illustrated in  FIG. 1 . Patches  30  are connected to electrodes  24  of catheter apparatus  22  through a patient interface unit  32 . Patient interface unit  32  is electrically linked to an external generator (not shown). Patches  30  direct radio-frequency energy to certain selected electrodes  24  inside the heart using inductively coupled delivery of the radio-frequency current.  
      Intracardial recordings and real-time visualizations of catheter  26  over the registered 3D model with the fluoroscopic system  20  permit a determination of which electrodes  24  are to be used for ablation. The externally controlled circuitry of patient interface unit  32  is programed with a map of electrodes  24  to enable unit  32  to identify the precise electrodes  24  to which radio-frequency energy needs to be delivered. One or more electrodes  24  can be used simultaneously for ablation. Patient interface unit  32  can be operated manually by the physician or provided with predetermined programs that the physician can select from to modify or operate automatically.  
      One skilled in the art will recognize that delivery of radio-frequency energy utilizing external patches  30  can also be accomplished when the catheter apparatus  22  is visualized and navigated within a cardiac chamber using an interventional system such as fluoroscopy but without any registered 3D models or images.  
      There is shown in  FIG. 4  an overview of a method for ablation of atrial fibrillation and other cardiac arrhythmias in accordance with this invention. As seen in step  110 , a 3D image of the heart is obtained from which a 3D model of the chamber of interest is created through segmentation of the image data using protocols optimized for the appropriate structures. 3D images of the heart can be acquired using CT scan or MRI. Once this 3D model has been obtained, it can be stored as an electronic data file using various means of storage. The stored model can then later be transferred to a computer workstation linked to an interventional system.  
      As illustrated in step  120 , after it has been transferred to the workstation, the 3D model is registered with the interventional system. The registration process allows medical personnel to correlate the stored 3D image of the cardiac chamber with the interventional system which is being used with a particular patient. The process also allows the physician to select a catheter that is the proper configuration for the cardiac chamber being ablated. This permits the portion of the catheter apparatus having electrodes to be tailored for the specific arrhythmia and for the specific anatomy of that chamber of the heart.  
      The next step  130  involves visualization of the catheter over the 3D model registered upon the interventional system. Thus at step  140 , as the catheter is navigated inside the chamber, the position and location of the electrodes is superimposed on the 3D image such that medical personnel can accurately localize the electrode or electrodes for ablation at the desired location.  
      In step  150 , external patches are placed on the patient. These patches are connected to the multiple electrodes of the mapping and ablation catheter inside the cardiac chamber of interest through a patient interface unit. The patient interface unit is configured in such a way that its external circuitry can be used to direct radio-frequency energy to the desired electrodes inside the heart.  
      As seen in step  160 , ablation of heart tissue at specifically selected locations is accomplished using ablation electrodes that receive their energy through the inductively coupled delivery of radio-frequency current. The use of external patches and the inductive coupled delivery of radio-frequency energy allows the catheter apparatus to perform additional functions, especially ones that utilize the 3D model registered upon the interventional system.  
      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.