Abstract:
Medical apparatus includes a flexible insertion shaft, which is adapted for insertion into a body of a patient. A resilient end section is fixed to the distal end of the insertion shaft and is formed so as to assume, when unconstrained, an arcuate shape. One or more electrodes are disposed at respective locations along the end section. A first lumen runs from the insertion shaft through the end section so as to convey an irrigation fluid to exit the end section through perforations of the electrodes. A second lumen runs through the insertion shaft to a distal opening and is configured to permit a guide wire to pass through the second lumen from the proximal end of the insertion shaft to exit distally through the distal opening, while conveying the irrigation fluid from the proximal end through the distal opening together with the guide wire.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to methods and devices for invasive medical treatment, and specifically to catheters. 
       BACKGROUND 
       [0002]    Ablation of myocardial tissue is well known as a treatment for cardiac arrhythmias. In radio-frequency (RF) ablation, for example, a catheter is inserted into the heart and brought into contact with tissue at a target location. RF energy is then applied through an electrode on the catheter in order to create a lesion for the purpose of breaking arrhythmogenic current paths in the tissue. 
         [0003]    Recently, circumferential ablation of the ostia of the pulmonary veins has gained acceptance as a treatment for atrial arrhythmias, and particularly for atrial fibrillation. For example, U.S. Patent Application Publication 2005/0033135, whose disclosure is incorporated herein by reference, describes a lasso for pulmonary vein mapping and ablation. A catheter for circumferentially mapping a pulmonary vein (PV) includes a curved section shaped to generally conform to the shape of the interior surface of the PV. The curved section comprises one or more sensing electrodes, and its proximal end is joined at a fixed or generally known angle to a base section of the catheter. The catheter is inserted into the heart, and the curved section is positioned in contact with the wall of the PV, while the base section remains within the left atrium, typically positioned such that the joint with the curved section is at the ostium of the vein. The sensing electrodes may additionally perform ablation of selected sites, or the catheter may further comprise ablation elements. 
         [0004]    U.S. Patent Application Publication 2010/0168548, whose disclosure is incorporated herein by reference, describes a lasso catheter for use in a system for electrical mapping of the heart. The catheter has an array of raised, perforated electrodes, which are in fluid communication with an irrigating lumen. There are position sensors on a distal loop section and on a proximal base section of the catheter. The electrodes are sensing electrodes that may be adapted for pacing or ablation. The raised electrodes securely contact cardiac tissue, forming electrical connections having little resistance. 
         [0005]    U.S. Patent Application Publication 2008/0281312 describes an ablation therapy system and systematic method for treating continuous atrial fibrillation. A carrier assembly and flexible outer catheter tube are percutaneously advanced over a guide wire whose distal end has been inserted into a pulmonary vein of the patient. After proper deployment of the carrier assembly, and after proper orientation and location of the electrodes relative to the targeted PV tissue, the carrier assembly is advanced distally, as a unit, along the guide wire to contact with the ostial tissue surrounding the Left Superior Pulmonary Vein (LSPV). Once sufficient tissue contact has been established, and the mapping procedure has confirmed the presence of aberrant conductive pathways, ablation energy may be passed through the output electrodes. 
       SUMMARY 
       [0006]    Embodiments of the present invention that are described hereinbelow provide invasive devices and methods for contacting tissue within the body with enhanced ease of use and therapeutic results. 
         [0007]    There is therefore provided, in accordance with an embodiment of the invention, medical apparatus, which includes a flexible insertion shaft, having a proximal end and a distal end, which is adapted for insertion into a body of a patient. A resilient end section is fixed to the distal end of the insertion shaft and is formed so as to assume, when unconstrained, an arcuate shape. One or more electrodes are disposed at respective locations along the end section and have perforations therein. A first lumen runs from the insertion shaft through the end section so as to convey an irrigation fluid from the proximal end of the insertion shaft to exit the end section through the perforations of the electrodes. A second lumen runs through the insertion shaft to a distal opening at the distal end of the insertion shaft, and is configured to permit a guide wire to pass through the second lumen from the proximal end of the insertion shaft to exit distally through the distal opening, while conveying the irrigation fluid from the proximal end through the distal opening together with the guide wire. 
         [0008]    In some embodiments, the guide wire is configured for insertion through a vascular system of a patient into a target vessel, and the insertion shaft is configured to be advanced distally, after the insertion of the guide wire into the target vessel, over the guide wire toward the target vessel. Typically, the resilient end section is configured, when the insertion shaft has been advanced to within a proximity of the target vessel, to contact tissue in the body along an arc surrounding the target vessel. In one embodiment, the target vessel is a pulmonary vein, and the guide wire is configured for insertion through a left atrium of a heart of the patient into the pulmonary vein, and the resilient end section is configured to contact and apply electrical energy to myocardial tissue surrounding the pulmonary vein via the one or more electrodes so as to ablate the tissue. Optionally, a distal tip of the resilient end section may be configured for attachment to the guide wire while the insertion tube is being advanced distally over the guide wire. 
         [0009]    In a disclosed embodiment, the apparatus includes a manifold, which is coupled to supply the irrigation fluid from a single fluid source to both of the first and second lumens and may be configured to inhibit a flow of the irrigation fluid through the second lumen in response to back-pressure from the first lumen. 
         [0010]    There is also provided, in accordance with an embodiment of the invention, medical apparatus, which includes a flexible insertion shaft, having a proximal end and a distal end, which is adapted for insertion into a body of a patient. First and second lumens run through the insertion shaft so as to convey an irrigation fluid from the proximal end of the insertion shaft to respective first and second outlets in a vicinity of the distal end. A manifold is coupled to supply the irrigation fluid from a single fluid source to both of the first and second lumens while inhibiting a flow of the irrigation fluid through the second lumen in response to back-pressure from the first lumen. 
         [0011]    In a disclosed embodiment, the manifold includes a flexible diaphragm, which is coupled to an actuator and is configured to deform in response to the back-pressure so as to cause the actuator to close a valve on the second lumen. Typically, the manifold has a single inlet for receiving the irrigation fluid from an irrigation pump and first and second outlets, separated by the diaphragm, for supplying the irrigation fluid to the first and second lumens, respectively. 
         [0012]    In some embodiments, the apparatus includes one or more electrodes, which are coupled to the distal end of the insertion shaft and are configured to be brought into contact with and to apply electrical energy to tissue in the body so as to ablate the tissue, wherein at least the first outlets include perforations in the electrodes. 
         [0013]    There is additionally provided, in accordance with an embodiment of the invention, a method for treatment, which includes providing a medical probe including a flexible insertion shaft having a resilient end section at the distal end of the insertion shaft and containing at least first and second lumens. A guide wire is inserted into a body of a patient so as to reach a target location in the body. The medical probe is advanced over the guide wire to the target location while passing the guide wire through the second lumen, wherein the guide wire exits the second lumen through a distal opening of the second lumen at the distal end of the insertion shaft, so as to bring the end section of the medical probe into contact with tissue in the body along an arc at the target location. One or more electrodes at respective locations on the end section are actuated to apply electrical energy to the tissue along the arc. While actuating the one or more electrodes, irrigation fluid is conveyed through the first lumen via perforations in the electrodes to the tissue and through the second lumen to exit the distal opening together with the guide wire. 
         [0014]    The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic, pictorial illustration of a system for ablation of tissue in the heart, in accordance with an embodiment of the present invention; 
           [0016]      FIG. 2  is a schematic sectional view of a heart showing insertion of a catheter into the left atrium, in accordance with an embodiment of the present invention; 
           [0017]      FIG. 3  is a schematic, pictorial illustration showing engagement of ostial tissue by the end section of a catheter, in accordance with an embodiment of the present invention; 
           [0018]      FIG. 4A  is a schematic internal view of a catheter handle, showing an irrigation manifold therein, in accordance with an embodiment of the present invention; 
           [0019]      FIG. 4B  is a schematic detail view of a part of a distal section of a catheter, showing lumens within the catheter, in accordance with an embodiment of the present invention; and 
           [0020]      FIG. 5  is a schematic, cutaway view of an irrigation manifold, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    Cardiologists often find it difficult to position and align a lasso catheter precisely around the pulmonary veins. Embodiments of the present invention address this problem by means of a guide wire, which is inserted into the pulmonary vein ahead of the catheter. 
         [0022]    In the disclosed embodiments, a medical probe, such as a lasso catheter, contains a lumen (also referred to as a channel) in the catheter shaft, through which the guide wire may pass. In typical operation, a sheath is inserted through the vascular system and into the left atrium through the interatrial septum. The guide wire is then inserted through the sheath to a target location, typically into a target vessel, such as one of the pulmonary veins. Finally, the lasso catheter (with the lasso straightened by the sheath) is inserted through the sheath and advanced over the guide wire. Once the lasso passes out of the sheath into the left atrium, it resumes its arcuate form. As the operator continues to push the catheter forward, the guide wire guides the shaft toward the pulmonary vein until the lasso seats against the ostium of the vein and contacts the tissue along an arc. 
         [0023]    It is desirable that the channel through which the guide wire passes be irrigated with positive pressure of irrigation fluid, in order to prevent formation or blood clots in the area of the wire outlet at the distal end of the shaft. The electrodes on the end section of the catheter may also be irrigated, so as to deliver irrigation fluid through perforations in the electrodes to the tissue during ablation. In an embodiment that is described hereinbelow, the catheter contains two irrigation lumens, one of which serves as the channel for the guide wire, and the other of which delivers the irrigation fluid to the electrodes. A manifold in the catheter delivers irrigation fluid from a single source, such as an irrigation pump, to both lumens, while controlling fluid pressure in order to inhibit excessive flow in one of the lumens in the event that the outlet of the other lumen is blocked. 
         [0024]    A guide wire and modified lasso catheter of this sort may be used not only in ablating around the pulmonary veins, but also in other diagnostic and therapeutic applications of medical probes having specially-shaped distal ends. The manifold may similarly be used to control flow and pressure in other applications in which an irrigation fluid is conveyed simultaneously through multiple lumens in an invasive medical probe. 
         [0025]      FIG. 1  is a schematic pictorial illustration of a system  20  for ablation of tissue in a heart  26  of a patient  28 , in accordance with an embodiment of the present invention. An operator  22 , such as a cardiologist, inserts a flexible probe, such as a catheter  24 , through the vascular system of patient  28  so that the distal end of the catheter enters a chamber of the patient&#39;s heart. Operator  22  advances the catheter so that the end section of the catheter engages endocardial tissue at a target location or locations, as shown in the figures that follow. The operator typically uses a handle  30  to manipulate and control the motion of the catheter inside the patient&#39;s body. 
         [0026]    Catheter  24  is connected by a suitable cable  32  to a console  31 . The console comprises an RF generator  36  for applying RF energy through electrodes on the end section of the catheter in order to ablate the tissue contacted by the distal section. In addition, an irrigation pump  34  supplies an irrigation fluid, such as saline solution, to irrigate the distal end of catheter  24 , as described further hereinbelow. Alternatively or additionally, catheter  24  may be used for other diagnostic and/or therapeutic functions, such as intracardiac electrical mapping or other types of ablation therapy, and similar sorts of probes may be used for diagnostic and therapeutic functions in organs other than the heart. 
         [0027]    System  20  may use position sensing to track the end section of catheter  24  inside heart  26 . For example, the system may use magnetic position sensing to find position coordinates of the end section of the catheter, as described, for example, in the above-mentioned U.S. Patent Application Publication 2005/0033135 or in U.S. Patent Application Publication 2011/0160719, whose disclosure is incorporated herein by reference. This sort of position sensing is implemented in the CARTO™ system produced by Biosense Webster Inc. (Diamond Bar, Calif.). Alternatively or additionally, system  20  may use other position-sensing techniques that are known in the art, such as impedance-based or ultrasonic position sensing. 
         [0028]      FIG. 2  is a schematic sectional view of heart  26 , showing insertion of catheter  24  into the heart, in accordance with an embodiment of the present invention. To insert the catheter in the pictured embodiment, operator  22  first passes a sheath  40  percutaneously through the vascular system and into right atrium  44  of the heart through ascending vena cava  42 . The sheath penetrates through interatrial septum  48 , typically via the fossa ovalis, into left atrium  46 . Alternatively, other approach paths may be used. A guide wire  54  is then threaded through sheath  40  and into one of pulmonary veins  50 . Operator  22  may align sheath  40  and guide wire  54  inside left atrium  46  with the axis of pulmonary vein  50  using the position sensing methods described above, for example, along with a pre-acquired map or image of heart  26 . Alternatively or additionally, the alignment may be performed under fluoroscopic or other means of visualization. 
         [0029]    Catheter  24  is then advanced over wire  54  through the lumen of sheath  40  until an end section  52  of the catheter passes out of the distal opening at the end of the sheath into left atrium  46 , as shown in  FIG. 2 . The end section is resilient and is formed so as to define an arc when unconstrained, as is shown and described in greater detail hereinbelow with reference to  FIG. 3 . While end section  52  is passing through sheath  40 , however, the smaller inner diameter of the sheath holds the end section straight and roughly parallel to the catheter axis. 
         [0030]      FIG. 3  is a schematic, pictorial illustration showing engagement of ostial tissue by end section  52  of catheter  24 , in accordance with an embodiment of the present invention. End section  52  is connected at its base to the distal end of a flexible insertion shaft  60  of the catheter. Shaft  60  and end section  52  typically comprise an outer shell made from a suitable flexible biocompatible material, such as polyurethane, having a diameter around 2-3 mm, with internal lumens as described below and internal wiring (not shown) as required. In one embodiment, in which the catheter is designed for therapeutic ablation, the size of the shaft is 7 Fr (about 2.3 mm diameter), while the end section is of the same or slightly larger size (such as 7.5 Fr). In other embodiments, for diagnostic measurements, the shaft is 7 Fr, while the end section may have a diameter between 1 and 2.5 mm. 
         [0031]    End section  52  is formed as a complete or partial lasso, i.e., as a preformed arcuate structure, which typically subtends between 180° and 360°. The radius of curvature of end section  52 , when unconstrained, is typically between 7.5 mm and 15 mm. Because the arc structure is resilient and, possibly, slightly helical, when end section  52  is positioned in the heart (against the ostium of pulmonary vein  50 , for example), and insertion shaft  60  is advanced distally over wire  54 , the end section will press against the heart tissue over the entire length of the arc, thus facilitating good tissue contact. The arcuate and possibly helical shape of end section  52  may be maintained, for example, by incorporating a thin strut made from a shape memory material, such as Nitinol (not shown in the figures), in the desired shape within the end section. The strut is made sufficiently flexible to permit the end section to straighten during insertion and withdrawal through sheath  40 , but to resume its arcuate form when it is unconstrained inside the heart chamber. 
         [0032]    End section  52  comprises an array of electrodes coupled along its length, including, in this example, a tip electrode  64  extending over the distal tip of the end section and proximal electrodes  66  distributed along the end section. Typically, electrodes  66  have a width between 1 mm and 4 mm, and are spaced between 1 mm and 10 mm apart. Electrodes  64  and  66  are connected to the proximal end of catheter  24  by wires (not shown) running through the catheter. Alternatively, other electrode configurations may be used. For example, the end section may include smaller “bump” electrodes, as described in the above-mentioned U.S. Patent Application Publication 2010/0168548. In any of these configurations, the electrodes may be used for sensing and/or ablation. In order to ablate an entire annulus around a pulmonary vein, for example, catheter  24  may be rotated (“clocked”) about its axis while actuating the electrodes to apply RF electrical energy to the tissue, as noted above. 
         [0033]    Guide wire  54  passes through a lumen (shown in  FIGS. 4A and 4B ) in shaft  60  and exits the shaft through a distal opening  68  of the lumen. After inserting the guide wire into pulmonary vein  50 , as shown in  FIG. 3 , the operator advances shaft  60  over the wire until end section  52  reaches the ostium of the target pulmonary vein  50 . Optionally, the distal tip of end section  52 , in the vicinity of electrode  64 , may be attached to wire  54 , as well, to aid in directing the end section straight toward the axis of vein  50 . This attachment may be temporary, so that the distal tip is released once it reaches the target location. 
         [0034]    In this manner, operator  22  brings the arcuate end section  52  of catheter  24  into contact with the ostium of vein  50 , so that the end section either partly or fully surrounds the vein (depending on the angle subtended by the arc), as shown in  FIG. 3 . Position sensors, such as magnetic transducers, in shaft  60  and/or in end section (not shown in the figures) may provide position readings to assist the operator in positioning and manipulating catheter  24 , as described, for example, in the above-mentioned U.S. Patent Application Publications 2005/0033135 and 2010/0168548. The operator then rotates the catheter about its axis within the sheath so that the end section traces an annular path around the circumference of the vein. Meanwhile, the operator actuates RF generator  36  to ablate the tissue along the path. After completing this procedure around one pulmonary vein, the operator may shift the sheath and catheter and repeat the procedure around one or more of the other pulmonary veins. 
         [0035]    To provide local cooling and prevent adhesion during ablation, one or more of electrodes  64  and  66  may have perforations to serve as outlets for irrigation. Any suitable sort of perforations may be formed in the electrodes, such as those described and shown, for example, in U.S. Patent Application Publication 2010/0168548. The perforations are coupled to one or more lumens in end section  52 , which carry irrigation fluid from shaft  60  to the electrodes and to the tissue surrounding them. In addition, it is desirable that the lumen through which guide wire  54  passes in shaft  60  be irrigated as well, to prevent formation of blood clots in the vicinity of opening  68 . Details of an arrangement of irrigation lumens that may be used for this purpose are described hereinbelow and are shown in the figures that follow. 
         [0036]      FIGS. 4A and 4B  are schematic detail views showing lumens  74  and  76  inside catheter  24 , in accordance with an embodiment of the present invention.  FIG. 4A  shows the proximal end of the catheter, in the vicinity of handle  30 , while  FIG. 4B  shows the distal end, at the base of end section  52 . Lumen  74  conveys irrigation fluid to electrodes  64  and  66 , while lumen  76  serves as the channel for passage of guide wire  54  through shaft to distal opening  68 . At the proximal end of shaft  60 , the guide wire is threaded out through a port  78 , which may be located, for example, in handle  30  as shown in FIG.  4 A. Port  78  typically has a seal to prevent leakage of irrigation fluid from the handle. Optionally, shaft  60  may contain one or more additional lumens (not shown), such as a dedicated lumen for irrigating tip electrode  64  separately from proximal electrodes  66 . 
         [0037]    Irrigation fluid is supplied to lumens  74  and  76  by pump  34  via a feed tube  70  passing through cable  32 . To avoid the need for two pumps or for a pump with a specialized dual outlet, an irrigation manifold  72  in catheter  24  divides the fluid provided at the manifold inlet by the single feed tube  70  between outlets to lumens  74  and  76 . Manifold  72  may conveniently be located in handle  30 , as shown in  FIG. 4A . Alternatively, a manifold of this sort may be deployed at any suitable location along insertion shaft  60 , including at the distal end of the insertion shaft, or possibly may be integrated into cable  32 . 
         [0038]      FIG. 5  is a schematic, cutaway view of irrigation manifold  72 , in accordance with an embodiment of the present invention. Manifold  72  contains a pressure regulator  80 , whose function is to automatically distribute fluid from pump  34  between lumens  74  and  76  so as to ensure that the flow rate through both lumens is maintained within desired limits notwithstanding possible blockages of the fluid outlets at the distal end of catheter  24 . Such blockages may occur, for example, when electrodes  64  and/or  66  press against tissue in the heart, so that the tissue closes off at least some of the perforations in the electrodes through which the irrigation fluid would otherwise flow out. In such a case, in the absence of regulator  80 , back-pressure in lumen  74  will propagate to lumen  76  and may cause excessive outflow of irrigation fluid through distal opening  68  along with reduced irrigation of the electrodes. 
         [0039]    To inhibit flow through lumen  76  under such conditions, regulator  80  comprises a piston  82 , which is coupled to a flexible diaphragm  86  located between the outlets of manifold  72  to lumens  74  and  76 . A grooved actuator  84  at the end of piston  82  adjacent to lumen  76  defines a valve, which is opened and shut by the movement of the piston (vertical movement in the view shown in the figure). Excess back-pressure from lumen  74  will distort diaphragm  86  in the downward direction, causing piston  82  to move downward with the diaphragm and thus close the valve on lumen  86 , as shown in the figure. In other words, increased fluid pressure in lumen  74  will automatically give rise to inhibit fluid flow, due to motion of piston  82 , in the path to lumen  76 . Thus, the desired proportion of flow between lumens  74  and  76  is maintained notwithstanding changes in back-pressure. 
         [0040]    Although regulator  80 , as shown in  FIG. 5 , is advantageous in terms of compactness and simplicity, other fluid regulation mechanisms may alternatively be used to maintain the desired distribution of irrigation fluid between lumens  74  and  76 . On the other hand, the principles of regulator  80  may similarly be applied in other sorts of medical devices in which fluid from a single source is to be distributed among multiple lumens. For example, an arrangement of this sort may be used to maintain a desired distribution of irrigation fluid among multiple electrodes at the distal end of a catheter, such as between electrodes  64  and  66 . 
         [0041]    It will thus be appreciated that the embodiments described above are cited by way of example, and 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 subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.