Abstract:
A catheter has an inflatable assembly at its distal portion, including a containment chamber, an axial core and a plurality of longitudinally oriented partitions extending from the axial core to the wall of the chamber to divide the containment chamber into at least four inflatable sectors. Hydraulic valves are connected to respective sectors to enable selective inflation of the sectors by a fluid when the valves are connected to a source of the fluid, and at least one surface electrode is mounted on each of the sectors. When introduced into a heart chamber and diametrically opposed sectors are inflated the assembly is stably fixed against the walls of the heart chamber and readings can be obtained from the surface electrodes of the inflated sectors.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to methods and devices for invasive medical treatment. More particularly, this invention relates to improvements in catheters. 
     2. Description of the Related Art 
     Cardiac arrhythmias, such as atrial fibrillation, occur when regions of cardiac tissue abnormally conduct electric signals to adjacent tissue, thereby disrupting the normal cardiac cycle and causing asynchronous rhythm. 
     Procedures for treating arrhythmia include surgically disrupting the origin of the signals causing the arrhythmia, as well as disrupting the conducting pathway for such signals. By selectively ablating cardiac tissue by application of energy via a catheter, it is sometimes possible to cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. 
     One such catheter is proposed in PCT patent document WO 2012/174375. The catheter has a balloon that may be expanded at some portions along its length through inflation. The catheter may have one or more differently compliant sections along its length, or may have a generally noncompliant body with one or more separate compliant portions overlying it. The compliant portions may be separately inflated to create, in one section of the catheter an expanded disk-like configuration with a circular, somewhat planar surface that is oriented orthogonally to the direction of the guide wire and facing in a distal direction. The catheter bears one or more RF electrodes that are capable of conducting RF energy and may be positioned on the surface of the balloon such that they take a circular configuration on the planar surface. 
     SUMMARY OF THE INVENTION 
     There is provided according to embodiments of the invention a medical apparatus, including a catheter having an elongated shaft and a distal portion. The distal portion includes an inflatable assembly, wherein the inflatable assembly includes a containment chamber, an axial core and a plurality of longitudinally oriented partitions extending from the axial core to the wall of the chamber to divide the containment chamber into at least four inflatable sectors. The sectors are externally delimited by respective bounding portions of the outer surface. Hydraulic valves are connected to respective sectors to enable selective inflation of the sectors by a fluid when the valves are connected to a source of the fluid, and at least one surface electrode is mounted on each of the bounding portions. 
     The apparatus may include a tip electrode disposed on the catheter distal to the inflatable assembly. 
     According to another aspect of the apparatus, the outer surface has perforations formed therethrough for egress of the fluid from the containment chamber. 
     The apparatus may include a control processor operative to control the valves. 
     According to another aspect of the apparatus, the at least one surface electrode is deformable when their respective sectors inflate and deflate. 
     There is further provided according to embodiments of the invention a method of catheterization, which is carried out by introducing a catheter into a heart chamber of a subject. The distal portion of the catheter includes an inflatable assembly. The inflatable assembly includes a containment chamber, an axial core and a plurality of longitudinally oriented partitions extending from the axial core to the wall of the chamber to divide the containment chamber into at least four inflatable sectors. The sectors are externally delimited by respective bounding portions of the outer surface. Hydraulic valves are connected to respective sectors to enable selective inflation of the sectors by a fluid when the valves are connected to a source of the fluid, and at least one surface electrode is mounted on each of the bounding portions. The method is further carried out by inflating a selected one of the pairs of the sectors sufficiently to stably press the outer surface of the pairs of the inflated sectors against the walls of the heart chamber while avoiding inflation of others of the sectors, wherein the at least one surface electrode of each sector of the selected pair contacts the walls of the heart chamber. 
     Another aspect of the method is performed after inflating the selected pair of sector by measuring electrical potentials from the at least one surface electrode of the sectors of the selected pair. The method may include passing an electric current through at least one surface electrode to ablate a portion of the walls of the heart chamber. 
     One aspect of the method is performed after inflating the selected pair of sectors by deflating the selected pair of the sectors, and thereafter inflating another one of the pairs. 
     In a further aspect of the method the outer surface has perforations formed therethrough, wherein inflating comprises flowing the fluid through the valves into the selected pairs of the sectors. The method further includes controlling the valves to admit the fluid into the selected pair and to exclude the fluid from sectors other than the selected pair, and cooling a surface electrode of the selected pair during ablation of the selected pair by egressing the fluid from the containment chamber via the perforations. 
     According to still another aspect of the method, the members of the selected pair of the sectors are inflated concurrently. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       For a better understanding of the present invention, reference is made to the detailed description of the invention, by way of example, which is to be read in conjunction with the following drawings, wherein like elements are given like reference numerals, and wherein: 
         FIG. 1  is a schematic, pictorial illustration of a vascular catheterization system, in accordance with an embodiment of the present invention; 
         FIG. 2  is a longitudinal schematic view of the distal portion of a catheter in accordance with an embodiment of the invention; 
         FIG. 3  is a schematic cross-sectional view of the catheter shown in  FIG. 2  through line  3 - 3 , in accordance with an embodiment of the invention; and 
         FIG. 4  is a flow chart of a method of cardiac catheterization using a segmented balloon catheter, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various principles of the present invention. It will be apparent to one skilled in the art, however, that not all these details are necessarily always needed for practicing the present invention. In this instance, well-known circuits, control logic, and the details of computer program instructions for conventional algorithms and processes have not been shown in detail in order not to obscure the general concepts unnecessarily. 
     System Description 
     Turning now to the drawings, Reference is initially made to  FIG. 1 , which is a schematic, pictorial illustration of a vascular catheterization system  10  in accordance with an embodiment of the present invention. Use of the system  10  involves inserting a catheter  12  into the body of a subject  14  at an insertion point  30 , for example a femoral artery or vein; thence into an internal body cavity, such as a heart chamber. Typically, the catheter  12  is used for diagnostic or therapeutic treatment performed by a medical practitioner  16 , such as mapping electrical potentials in the heart or performing ablation of heart tissue. The catheter  12  may alternatively be used for other purposes, by itself or in conjunction with other treatment devices. Supporting elements related to the medical procedure are found in a control unit  26 , which contains processors for data reported by signals from sensors in the catheter  12 , e.g., via a cable  32 . The control unit  26  may include an ablator power generator, irrigation pump and electrocardiographic circuitry. Events and data reported to the control unit  26  may be displayed on a monitor  34 . However, as explained below, the control unit  26  need not include position-locating circuitry to track the location and orientation of the catheter  12  in the heart and elsewhere in the body of the subject  14 . The catheter  12  typically contains hydraulic lines to transfer fluid from the irrigation pump via the catheter&#39;s handle to the distal portion of the catheter  12  as explained below. The hydraulic connection to the pump is not shown in  FIG. 1  in order to preserve clarity of illustration. 
     Reference is now made to  FIG. 2 , which is a longitudinal schematic view of the distal portion of a catheter  36 , which is useful for mapping regions in and around the heart and for tissue ablation in accordance with an embodiment of the invention. The catheter  36  comprises an elongated tubular shaft  38 . An inflatable balloon assembly  40  is provided at the distal end of the catheter body. The inflatable balloon assembly  40  comprises a containment chamber, which is internally partitioned into sectors  42 ,  44 ,  46 ,  48  by a plurality of septa. The septa extend to an outer surface  50  from an axial core  52  and are oriented longitudinally about the axial core  52 . The sectors  42 ,  44 ,  46 ,  48  are externally delimited by respective bounding portions of the outer surface  50 . Although four sectors are shown in  FIG. 2 , the inflatable balloon assembly  40  may comprise any number of sectors greater than four. Surface features and functionality of the inflatable balloon assembly  40  are described below. 
     The sectors  42 ,  44 ,  46 ,  48  of the inflatable balloon assembly  40  must be flexible enough to maintain mechanical contact between the outer surface  50  and the wall of the heart chamber so that when inflated, they stably press the outer surface of the pairs of the inflated sectors against the wall of the heart chamber, but are not so rigid as to interfere with the movements of heart wall. The inflation pressure may be determined empirically by the operator, or may be determined using the teachings of U.S. patent application Ser. No. 13/343,024, entitled “Contact Assessment Based on Phase Measurement”, Govari et al., now published as U.S. Patent Publication No. 2013/0172875, which is herein incorporated by reference. 
     The deflated sectors occupy little space and blood readily flows around them through the heart chamber, and thus blood flow through the heart is not substantially obstructed. 
     A tip electrode  54  can optionally be used for local measurements and ablation when the inflatable balloon assembly  40  is deflated. 
     Reference is now made to  FIG. 3 , which is a schematic cross-sectional view of the catheter  36  through line  3 - 3  of  FIG. 2 , in accordance with an embodiment of the invention. On this view, it can be appreciated that the inflatable balloon assembly  40  comprises a tubular structure comprising a pre-formed generally circular main region generally transverse and distal to the catheter body and having a circumferential outer surface  50 . Septa  56 ,  58 ,  60 ,  62  extending radially from the core  52  to the outer surface  50  and define the sectors  42 ,  44 ,  46 ,  48 . 
     Each of the sectors  42 ,  44 ,  46 ,  48  is independently connected to a fluid source  64 , and is selectively inflatable using control valves  66 , which deliver an irrigation fluid, typically saline, to the sectors  42 ,  44 ,  46 ,  48  via respective fluid lines  68 . For example, sectors  44 ,  48 , which oppose one another diametrically, are inflated concurrently, while the other sectors  42 ,  46  remain deflated. Fluid may be supplied to the sectors  44 ,  48  by simultaneously opening their respective control valves  66 . In any case, both of the sectors  44 ,  48  become inflated in an operating position for taking measurements. The control unit  26  ( FIG. 1 ) may comprise a processor to regulate the control valves  66 . Alternatively, the control valves  66  may be controlled manually by the practitioner  16  or an assistant. 
     The portion of the outer surface  50  overlying respective sectors  42 ,  44 ,  46 ,  48  has a flexible array of electrodes  70  mounted thereon, which can be used for mapping and ablation. The electrodes  70  and associated connectors are required to deform as the sectors  42 ,  44 ,  46 ,  48  expand and contract. Construction of flexible, stretchable electronic elements is known, for example from the documents Controlled Buckling of Semiconductor Nanoribbons for Stretchable Electronics, Yugang Sun et al., Nature Nanotechnology 1, 201-207 (2006) and U.S. Patent Application Publication No. 2011/0254171. Devices constructed in such manner are capable of conforming to curved surfaces and withstanding mechanical deformations. 
     Optionally, perforations  72  may be formed through the outer surface  50  near the electrodes  70 . In such case, the fluid selectively delivered to the sectors  42 ,  44 ,  46 ,  48  from the fluid source  64  egresses the inflatable balloon assembly  40  via the perforations  72  and cools the electrodes  70  and the ablation site during ablation. 
     Operation 
     Reference is now made to  FIG. 4 , which is a flow chart of a method of cardiac catheterization using a segmented balloon catheter, in accordance with an embodiment of the invention. Not all illustrated process steps may be required to implement the process. At initial step  74  the catheter  36  ( FIG. 2 ) is inserted into the heart in a known manner, and positioned within a chamber of interest. At this point the sectors  42 ,  44 ,  46 ,  48  are all deflated. 
     Next, at step  76 , a diametrically opposing pair of sectors is selected, for example the sectors  44 ,  48  ( FIG. 3 ). 
     Next, at step  78 , the pair of sectors selected in step  76  are inflated. All non-selected sectors remain deflated. 
     Next, at step  80 , electrical contact between the wall of the cardiac chamber and those electrodes  70  that are mounted on the selected sectors is verified. 
     Next, at step  82  a measurement or procedure is performed using the electrodes  70  of the two opposing inflated sectors, for example bipolar measurements of electrical potentials during the cardiac cycle. 
     Next, at decision step  84 , it is determined if more pairs of sectors of the inflatable balloon assembly  40  remain to be processed. If the determination at decision step  84  is affirmative, then control proceeds to step  86 . The current pair of inflated sectors is deflated. Control returns to step  76  to iterate the procedure with another pair of sectors. 
     If the determination at decision step  84  is negative then at step  88  the current pair of inflated sectors is deflated. This could occur if all pairs have been inflated, or if it was decided to evaluate the signals obtained from fewer than all pairs of sectors. Indeed, it may be appropriate to evaluate the signals obtained from one pair of sectors before inflating the next pair. At step  90 , signals thus far collected from the endocardial surfaces via the electrodes of the pairs of inflated sectors are evaluated, either by the physician or automatically. 
     After evaluating the ECG signals, as indicated by a broken line, selected pairs of sectors may optionally be reflated, and control would then return to step  76 . Alternatively, the physician typically makes a decision regarding ablation at final step  92 . 
     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 hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.