Abstract:
The present invention discloses an ablation electrode used in a catheter. The ablation electrode includes an electrode shell, an optional cavity inside the electrode shell and a temperature sensor. An outflow liquid pathway for the perfusion liquid is arranged on the electrode shell, and an inflow liquid pathway for the perfusion liquid is arranged in the proximal end of the electrode shell. A thermal conduction isolation structure is arranged between the temperature sensor and the liquid pathway. The thickness of the electrode shell where the temperature sensor is located is less than 0.2 mm. The present invention also provides a perfusion electrode catheter which includes the ablation electrode. The perfused electrode catheter of the present invention can provide efficient prompts on the rising ablation temperature in the ablation process.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of International Patent Application No. PCT/CN2013/000335, filed Mar. 22, 2013, which in turn claims the benefit and priority of Chinese patent application 201210079501.4, filed Mar. 23, 2012, the entire contents of all applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an ablation electrode and a perfused electrode catheter using the electrode, and more particularly relates to an ablation electrode with a temperature sensor and a perfused electrode catheter using the same. 
       BACKGROUND OF THE INVENTION 
       [0003]    Electrode catheters have been widely applied to clinical practice for many years. They may be used in hearts to map and stimulate electrical activities and perform ablation therapy on positions occurring abnormal electrical activities. 
         [0004]    In clinical use, an electrode catheter enters the body through a main vein or artery, e.g. through a femoral vein, and then is guided into the concerned heart chamber. In some applications, the catheter is expected to have the capability of injecting and/or extracting liquid, and such a function may be completed by a perfused catheter. 
         [0005]    In a specific application example, an ablation injury is generated in the heart through catheter intracardiac ablation, so as to cut off an abnormal electrocardio conduction path in the heart. A typical ablation operation process includes that, a catheter provided with an ablation electrode at the distal end thereof is inserted into the heart chamber, a reference electrode is provided and generally attached and fixed to the skin surface of a patient, and a radio frequency (RF) voltage is applied between the ablation electrode and the reference electrode to generate RF electric current flowing through media therebetween, including blood and tissue. The distribution of the electric current depends on the ratio of the contact area of the ablation electrode and the tissue to the contact area of the ablation electrode and the blood. After the heart tissue is sufficiently heated by the heating effect of the RF electric current, tissue cells are destroyed to form an injury in the heart tissue, and the injured tissue does not form electrical conduction. In this process, the heated tissue simultaneously heats the ablation electrode through heat conduction. If the temperature of the electrode is high enough, e.g. higher than 60° C., a thin film formed by dehydration of blood protein may be formed on the surface of the electrode, and if the temperature is further raised, the dehydrated protein layer is gradually thickened, and thus blood coagulation occurs on the surface of the electrode. Because the electrical conductivity of the dehydrated biomaterial is lower than that of the intracardiac tissue, the impedance for the RF electric current flowing into the tissue is increased, and when the impedance becomes high up to a certain degree, the catheter must be taken out of the body to clean the ablation electrode. 
         [0006]    Another method for achieving the aforementioned desired effect is to perfuse the ablation electrode. For example, the ablation electrode is actively cooled by adopting normal saline at room temperature, rather than depending on the relatively passive cooling effect of the blood. Under such a condition, the electrode is effectively cooled, and the surface temperature thereof is no longer the main factor of producing impedance increase and even blood coagulation, so that the intensity of the RF electric current is no longer limited by the surface temperature, the electric current may be increased, and thus a larger injury closer to a sphere shape is formed, generally in a size of 10 mm to 12 mm. 
         [0007]    U.S. Pat. No. 5,643,197 and U.S. Pat. No. 5,462,521 disclose a perfused electrode made of a porous material, wherein the electrode has a metallic structure formed by sintering tiny particles, and the liquid cooling of the electrode structure is more effective through multiple interconnected channels. Moreover, the porous structure enables liquid flow to form a liquid film uniformly distributed on the surface of the electrode and becoming a blocking layer between the blood and the surface of the electrode. 
         [0008]    Therefore, a novel perfused catheter is needed. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides an ablation electrode for a catheter, including an electrode shell, and an optional cavity and a temperature sensor in the electrode shell; a liquid passage for outflow of perfusion liquid is provided in the electrode shell, and a liquid passage for inflow of the perfusion liquid is provided in the proximal end of the electrode shell; and a heat-conducting insulation structure is provided between the temperature sensor and the liquid passages, and the thickness of the electrode shell where the temperature sensor is located is less than 0.2 mm. 
         [0010]    The term “optional” used in the context expresses the meaning of “not indispensable” or “not essential”. For example, “optional cavity” indicates that there may be or may not be the cavity. This may be selected by those skilled in the art according to conditions. 
         [0011]    In an implementation of the present invention, the electrode shell is provided with a through hole, and the temperature sensor is provided in the through hole. 
         [0012]    In a specific implementation of the present invention, an insert is provided at the proximal end of the electrode shell, the distal end of the insert extends into the cavity, and the insert includes at least one through hole; the distal end of the through hole in the insert extends into the through hole of the electrode shell, the proximal end of the through hole in the insert is opened at the proximal end of the insert, the distal end of the through hole in the insert is opened on the outer surface of the electrode shell and is flush with the outer surface of the electrode shell, and the temperature sensor is provided at the distal end of the through hole in the insert. 
         [0013]    In a specific implementation of the present invention, the surface area of the electrode shell is greater than 15 square mm. 
         [0014]    In a specific implementation of the present invention, the surface of the electrode shell is provided with several small holes, the total orifice area of the small holes is less than the area of the smallest cross section of the liquid passage for inflow of the perfusion liquid. 
         [0015]    In a specific implementation of the present invention, an insert is provided at the proximal end of the electrode shell, the distal end of the insert extends into the cavity, and the insert includes at least one through hole; the distal end of the through hole in the insert extends to the inner surface of the electrode shell and is flush with the inner surface of the electrode shell, or the distal end of the through hole in the insert partially extends into the electrode shell; the proximal end of the through hole in the insert is opened at the proximal end of the insert, the distal end of the through hole in the insert is opened or has a closed construction, and the temperature sensor is provided at the distal end of the through hole in the insert. 
         [0016]    Preferably, the heat-conducting insulation structure is a nonmetallic heat insulation layer. 
         [0017]    The nonmetallic heat insulation layer may be provided on the inner wall and/or outer wall of the through hole in the insert; preferably, the inner wall and/or outer wall of the through hole in the insert is partially or completely provided with the nonmetallic heat insulation layer. 
         [0018]    Preferably, the nonmetallic heat insulation layer is made of a high polymer material or ceramic, or is a gas heat insulation layer. 
         [0019]    The distance between a temperature sensing portion of the temperature sensor and the top end of the temperature sensor may be less than 0.5 mm; preferably, the distance between the temperature sensing portion of the temperature sensor and the top end of the temperature sensor is less than 0.2 mm; and more preferably, the distance between the temperature sensing portion of the temperature sensor and the top end of the temperature sensor is less than 0.1 mm. 
         [0020]    The present invention provides a perfused electrode catheter, which is characterized by including: 
         [0000]    a catheter main body having a proximal end, a distal end and a central chamber penetrating through the catheter main body;
 
an ablation portion, comprising a section of elastic tip tube, and having a proximal end, a distal end and at least one chamber penetrating through ablation portion, the proximal end of the ablation portion is fixedly connected with the distal end of the catheter main body;
 
an ablation electrode, fixedly connected to the distal end of the ablation portion, and including an electrode shell, and an optional cavity and a temperature sensor in the electrode shell, wherein a liquid passage for outflow of perfusion liquid is provided in the electrode shell, and a liquid passage for inflow of the perfusion liquid is provided in the proximal end of the electrode shell; and a heat-conducting insulation structure is provided between the temperature sensor and the liquid passages, and the thickness of the electrode shell where the temperature sensor is located is less than 0.2 mm;
 
a perfusion passage, having a proximal end and a distal end, the distal end of the perfusion passage extends into the chamber of the ablation portion through the central chamber of the catheter main body and is communicated with the liquid passage for inflow of the perfusion liquid of the ablation electrode.
 
         [0021]    In an implementation of the present invention, the electrode shell is provided with a through hole, and the temperature sensor is provided in the through hole. 
         [0022]    In a specific implementation of the present invention, an insert is provided at the proximal end of the electrode shell, the distal end of the insert extends into the cavity, and the insert includes at least one through hole; the distal end of the through hole in the insert extends into the through hole of the electrode shell, the proximal end of the through hole in the insert is opened at the proximal end of the insert, the distal end of the through hole in the insert is opened on the outer surface of the electrode shell and is flush with the outer surface of the electrode shell, and the temperature sensor is provided at the distal end of the through hole in the insert. 
         [0023]    The diameter of the through hole in the electrode shell may be less than 1 mm; and preferably, the diameter of the through hole in the electrode shell is less than 0.5 mm. 
         [0024]    Preferably, the surface area of the electrode shell is greater than 15 square mm. 
         [0025]    Preferably, the surface of the electrode shell is provided with several small holes, the total area of the small holes is less than the area of the smallest cross section of the liquid passage for inflow of the perfusion liquid. 
         [0026]    In a specific implementation of the present invention, an insert is provided at the proximal end of the electrode shell, the distal end of the insert extends into the cavity, and the insert includes at least one through hole; the distal end of the through hole in the insert extends to the inner surface of the electrode shell and is flush with the inner surface of the electrode shell, or the distal end of the through hole in the insert partially extends into the electrode shell; the proximal end of the through hole in the insert is opened at the proximal end of the insert, the distal end of the through hole in the insert is opened or has a closed construction, and the temperature sensor is provided at the distal end of the through hole in the insert. 
         [0027]    A perfusion pipeline is provided in the perfusion passage, and the distal end of the perfusion pipeline may extend to the distal end of the chamber of the ablation portion through a control handle and the central chamber of the catheter main body and is communicated with the liquid passage of the ablation electrode, or extend to the distal end of the central chamber of the catheter main body through the control handle and is communicated with at least one chamber penetrating through the ablation portion. 
         [0028]    Preferably, the heat-conducting insulation structure is a nonmetallic heat insulation layer. 
         [0029]    The nonmetallic heat insulation layer may be provided on the inner wall and/or outer wall of the through hole in the insert. 
         [0030]    Preferably, the nonmetallic heat insulation layer is made of a high polymer material or ceramic, or is a gas heat insulation layer. 
         [0031]    The distance between a temperature sensing portion of the temperature sensor and the top end of the temperature sensor may be less than 0.5 mm; preferably, the distance between the temperature sensing portion of the temperature sensor and the top end of the temperature sensor is less than 0.2 mm; and more preferably, the distance between the temperature sensing portion of the temperature sensor and the top end of the temperature sensor is less than 0.1 mm. 
         [0032]    In a preferred implementation of the present invention, the perfused electrode catheter includes the heat-conducting insulation structure, so that the temperature sensor is separated from the cooling effect of the perfusion liquid, the cooling effect of the perfusion liquid on the part where the temperature sensor is located is weakened, and the heating effect of circumferential heat conduction from the outer wall of the electrode shell on the part where the temperature sensor is located is maintained; and the temperature sensor is provided on the inner surface of the electrode shell or in the through hole of the electrode shell or partially extends into the electrode shell, so that the temperature sensor may detect more temperature rise produced by the heating effect of radio-frequency electric currents. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]      FIG. 1  is a structural schematic diagram of a perfused electrode catheter according to the present invention; 
           [0034]      FIG. 2  shows a sectional view of a catheter main body  12  according to a preferable implementation of the present invention, illustrating the connection relationship between the catheter main body  12  and an ablation portion  13 ; 
           [0035]      FIG. 3  shows a sectional view along line A-A of  FIG. 1 ; 
           [0036]      FIG. 4  shows a sectional view along line B-B of  FIG. 3 ; 
           [0037]      FIG. 5  shows a sectional view along line C-C of  FIG. 3 ; 
           [0038]      FIG. 6  shows a schematic diagram of a temperature sensor  33  in an ablation electrode  17  according to a preferable implementation of the present invention; 
           [0039]      FIG. 7  shows a sectional view of an ablation electrode  17  according to a further preferable implementation of the present invention; 
           [0040]      FIG. 8  shows a structural diagram of an ablation electrode  17  according to a further preferable implementation of the present invention; 
           [0041]      FIG. 9  shows a sectional view of the ablation electrode  17  shown in  FIG. 8 ; 
           [0042]      FIG. 10  shows a sectional view of an ablation electrode  17  according to a further preferable implementation of the present invention; 
           [0043]      FIG. 11  shows a sectional view of the ablation electrode  17  shown in  FIG. 10 ; 
           [0044]      FIG. 12  shows a sectional view of an ablation electrode  17  according to a further preferable implementation of the present invention; 
           [0045]      FIG. 13  shows a sectional view of an ablation electrode  17  according to a further preferable implementation of the present invention; and 
           [0046]      FIG. 14  shows a sectional view of an ablation electrode  17  according to a further preferable implementation of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0047]    The technical solution of the present invention will be further described below in detail with reference to the implementations and in combination with the accompanying drawings, but the present invention is not merely limited to the following implementations. 
         [0048]      FIG. 1  shows a structural schematic diagram of a perfused electrode catheter  10  with a temperature sensor of the present invention, which includes a catheter main body  12  having a distal end, at which an ablation portion  13  is provided, and a proximal end, at which a control handle  11  is provided. 
         [0049]      FIG. 2  shows a sectional view of the catheter main body  12  according to one implementation of the present invention, illustrating the connection relationship between the catheter main body  12  and the ablation portion  13 . The catheter main body  12  includes a reinforcement tube  22  and a main body tube  28  sleeved outside the reinforcement tube, wherein the main body tube  28  may be made of a biocompatible high polymer material, e.g. polyether block amide, polyurethane or nylon material, and the wall of the main body tube  28  preferably includes therein at least one metal wire braided layer (not shown in the figure), which may be a stainless steel wire braided layer. There may be one, two or more metal wire braided layers. The reinforcement tube  22  includes a central chamber  23  and may be made of any suitable high polymer material, such as being made by extrusion molding of polyether block amide, polyurethane, polyimide or nylon material. The catheter main body is preferably elongated and bendable, but typically incompressible in the length direction thereof. The central chamber  23  extends in the axial direction of the catheter main body  12 ; and a conducting wire  25 , a traction wire  21  and a perfusion pipeline  26  extend inside the central chamber  23 . 
         [0050]    The ablation portion  13  includes an elastic tip tube  31 , which may be made of a biocompatible material and includes a distal end, a proximal end and at least one chamber, wherein the chamber may be a central or eccentric chamber. In one specific implementation of the present invention, as shown in  FIG. 2 , the elastic tip tube  31  includes a first eccentric chamber  35 , a second eccentric chamber  36  and a third eccentric chamber  37 . Preferably, the wall of the elastic tip tube  31  includes therein at least one metal wire braided layer (not shown in the figure), which may be a stainless steel wire braided layer. There may be one, two or more metal wire braided layers. 
         [0051]    Preferably, the proximal end of the elastic tip tube  31  is a thinned end  34  having an outer diameter matched with the inner diameter of the catheter main body  12 , as shown in  FIG. 2 . The thinned end  34  is inserted into the catheter main body  12  and may be fixed by bonding, welding or other appropriate means. For example, the thinned end  34  is bonded and fixed to the catheter main body  12  through UV cured adhesive. 
         [0052]      FIG. 3  shows a sectional view along line A-A of  FIG. 1 ,  FIG. 4  shows a sectional view along line B-B of  FIG. 3 ,  FIG. 5  shows a sectional view along line C-C of  FIG. 3 , and  FIG. 6  shows a schematic diagram of a temperature sensor  33  shown in  FIG. 4  and  FIG. 5 . An ablation electrode  17  is disposed at the distal end of the elastic tip tube  31 , and ring electrode(s)  16 , the number of which may vary according to actual needs, are provided in the length direction of the elastic tip tube  31 . There may be no ring electrode, or there may be one, two, three, four or more ring electrodes. Preferably, a ring electrode  16  is provided along the length direction of the elastic tip tube  31 . The distance between the ring electrode  16  and the ablation electrode  17  is in 0.5 to 5 mm, preferably in 1 to 2 mm. The ring electrode  16  and the ablation electrode  17  forms a pair of electrodes for high-frequency electrical stimulation of the renal vein, causing the variation in blood pressure of the patients. Thus the effectiveness of ablating the target may be determined according to the degree of variation of the blood pressure and heart rate of the patient. The ablation electrode  17  includes an electrode shell  71  and a cavity  76  therein. The electrode shell  71  is further provided with a through hole  79  having a diameter of less than 1 mm. Preferably, the through hole  79  has a diameter of less than 0.5 mm. The outer surface of the electrode shell  71  is a part which can be in contact with tissue to be ablated; and the cavity inside the electrode shell  71  is a part which cannot be in contact with the tissue. 
         [0053]    In a preferable implementation, as shown in  FIG. 4  and  FIG. 5 , an insert  74  is provided in the cavity  76 , wherein the insert  74  is provided at the proximal end of the electrode shell  71 , and the distal end of the insert  74  extends into the cavity  76 . The insert  74  may be cylindrical, disc-shaped or in other suitable shape and at least includes a through hole  81 . The distal end of the through hole  81  extends into the through hole  79  of the electrode shell  71 . The extending section of the through hole  81  and the insert  74  may be formed integrally or separately. For example, a hollow tube is inserted into the through hole  81 , or the distal end of the through hole  81  is connected with a pipeline or other suitable structure. The proximal end of the through hole  81  is opened at the proximal end of the insert  74 , and the distal end of the through hole  81  is opened on the outer surface of the electrode shell  71  and is flush with the outer surface of the electrode shell  71 . A temperature sensor  33  is provided at the distal end of the through hole  81  and is fixed by adhesive bonding. The temperature sensor  33  is located at the through hole in the electrode shell, where the thickness of the electrode shell is zero. The through hole  81  may be located close to the axis of the electrode shell  71  or close to the side wall of the electrode shell  71 . The insert further includes a through hole  80 , and the through hole  80  is a liquid passage for the inflow of perfusion liquid. 
         [0054]    As shown in  FIG. 6 , an outer sleeve  332  is sleeved outside the temperature sensor  33  and the outer sleeve is made of an insulating material or an insulating and thermal insulation material. The distance between a temperature sensing portion  331  of the temperature sensor  33  and the top end of the temperature sensor is less than 0.5 mm. Preferably, the distance between the temperature sensing portion of the temperature sensor and the top end of the temperature sensor is less than 0.2 mm. More preferably, the distance between the temperature sensing portion of the temperature sensor and the top end of the temperature sensor is less than 0.1 mm. Insulating but heat-conducting glue  333  may be provided between the temperature sensing portion  331  and the top end, so as to improve the sensitivity of the temperature sensor and provide enough insulating property at the same time. The top end of the temperature sensor  33  may be flush with the outer surface of the electrode shell or located nearby the outer surface of the electrode shell. For example, a small part of the top end of the temperature sensor  33  protrudes out of the outer surface or retracts inside the outer surface. 
         [0055]    The insert  74  further includes a blind hole  82  in which a traction wire  21  is fixed. The through hole  80 , the through hole  81  and the blind hole  82  are communicated with the first eccentric chamber  35 , the second eccentric chamber  36  and the third eccentric chamber  37  of the elastic tip tube  31  respectively. Preferably, a hollow tube, which may be made of a suitable high polymer material or metallic material, e.g. polyimide or stainless steel, may be welded or bonded on each of the three holes  80 ,  81  and  82  of the insert  74  respectively. 
         [0056]    A heat-conducting insulation structure is provided between the temperature sensor  33  and the liquid passage, and the heat-conducting insulation structure is a nonmetallic heat insulation layer  78 , which is disposed on the through hole  81 . When the extending section of the through hole  81  and the insert  74  are formed integrally and the insert  74  is made of a metallic material, the nonmetallic heat insulation layer  78  is disposed on the inner wall and/or outer wall of the through hole  81 . The inner wall and/or outer wall of the through hole  81  in the context may refer to the inner wall and/or outer wall of a section of the through hole  81  extending in the cavity, or the inner wall and/or outer wall of the entire through hole  81 . The nonmetallic heat insulation layer  78  may be a tubular heat insulation layer inserted into the inner wall and/or onto the outer wall of the through hole  81 , or may be a nonmetallic heat insulation layer coated on the inner wall and/or outer wall of the through hole  81 . When the insert  74  is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. When the extending section of the through hole  81  and the insert  74  are formed separately and the extending section of the through hole  81  is made of the metallic material, the nonmetallic heat insulation layer  78  is disposed on the inner wall and/or outer wall of the through hole  81 . When the extending section of the through hole  81  of the insert is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. 
         [0057]    The nonmetallic heat insulation layer  78  may completely or partially cover the inner wall and/or outer wall of the through hole  81 . When the nonmetallic heat insulation layer  78  partially covers the inner wall and/or outer wall of the through hole  81 , the degree of heat insulation may be adjusted, so as to adjust the temperature detected by the temperature sensor  33 . When the material or thickness of the nonmetallic heat insulation layer is changed, the degree of heat insulation may also be adjusted. The nonmetallic heat insulation layer  78  is made of a nonmetallic material with a heat insulation function, which may be a high polymer material or ceramic or other suitable nonmetallic material. The nonmetallic heat insulation layer  78  may also be a gas heat insulation layer. When using a gas heat insulation layer, the nonmetallic heat insulation layer  78  may be a heat insulation layer consisted of foaming material, a heat insulation layer consisted of one or more air-tight chambers filled with air, or other suitable structures. The nonmetallic heat insulation layer  78  may be made of a nonmetallic material with high temperature resistance. Because the nonmetallic heat insulation layer  78  is provided on the through hole  81 , the temperature sensor is separated from the cooling effect of the perfusion liquid. The cooling effect of the perfusion liquid on the part where the temperature sensor is located is weakened, and the temperature sensor will be able to detect more temperature rise produced by the heating effect of radio-frequency currents. 
         [0058]    The insert  74  may be completely placed in the cavity of the electrode shell  71 , or partially placed in the cavity of the electrode shell  71 , as shown in  FIG. 7 . 
         [0059]    The temperature sensor  33  may be a thermocouple, a thermistor or other device. There may be one, two, three or more temperature sensors. As shown in  FIG. 4 , the distal end of the temperature sensor  33  extends into the second eccentric chamber  36  of the elastic tip tube  31  through the central chamber  23  of the catheter main body  12 , then extends into the through hole  81 , and is fixed at the distal end of the through hole  81  by glue bonding. The proximal end of the temperature sensor  33  extends into the control handle  11  through the central chamber  23 , then extends out of the control handle  11  and is connected with a temperature monitoring device (not shown in the figure). A perfusion passage has a proximal end and a distal end, wherein the distal end of the perfusion passage extends into the first eccentric chamber  35  of the elastic tip tube  31  through the control handle  11  and the central chamber  23  of the catheter main body  12  and is communicated with the liquid passage of the ablation electrode  17 . The perfusion pipeline  26  is provided in the perfusion passage. The distal end of the perfusion pipeline  26  may extend to the distal end of the first eccentric chamber  35  of the elastic tip tube  31  through the control handle  11  and the central chamber  23  of the catheter main body  12  and is communicated with the liquid passage of the ablation electrode  17 , or may extend to the distal end of the central chamber  23  of the catheter main body  12  through the control handle  11  and is communicated with the first eccentric chamber  35  of the elastic tip tube  31 . 
         [0060]    The perfusion pipeline  26  may be made of any suitable material, and the distal end of the perfusion pipeline  26  extends into the first eccentric chamber  35  of the elastic tip tube  31  through the central chamber  23  of the catheter main body  12  and is communicated with the through hole  80  in the insert  74 . The proximal end of the perfusion pipeline  26  extends into the control handle  11  through the central chamber  23  of the catheter main body  12 , and may be fixed in any suitable method known by those skilled in the art. For example, the proximal end of the perfusion pipeline  26  is connected with a section of branch pipe  14 , as shown in  FIG. 1 , wherein the branch pipe  14  extends to the outside of the control handle  11 , and the end of the branch pipe  14  is connected and fixed with a Luer taper  15 . 
         [0061]    The electrode shell  71  is provided with a plurality of small holes (not shown in the figure) serving as liquid passages for outflow of the perfumed liquid. The small holes may be formed in any suitable manner. They may be formed in a manner of machining, laser processing or electro-machining and the like, or may also be formed by using a porous material. Preferably, the small holes are evenly distributed on the surface of the electrode shell  71 . The total orifice area of the small holes is less than the area of the smallest cross section of the perfusion pipeline. Such an implementation may ensure that the cool saline water may evenly cover the ablation electrode, so that the tissue abutted on by the ablation electrode may be evenly washed by the perfusion liquid, thus lowering the contact resistance of the tissue abutted on by the ablation electrode, and allowing the electric current entering into the tissue to make effective ablation. The surface area of the electrode shell  71  is greater than 15 square mm, so that the effectiveness and safety of the ablation may be ensured simultaneously. The effectiveness of the ablation is to ensure the depth of the ablation, so as to block the sympathetic nerves in the outer layers of the renal vein, and make the output power of the energy big enough. The safety is to lower the electric current density as much as possible, ensuring that the temperature of the tissue abutted on by the ablation electrode is not too high, and the tissue cells would not be injured. Therefore, increasing the surface area of the ablation electrode may ensure that the total power is increased, while at the same time the output power per unit area is kept at a low level. 
         [0062]    The perfusion liquid, which may be any suitable liquid, such as normal saline, enters the perfusion pipeline  26  through the branch pipe  14 , enters the cavity  76  of the ablation electrode  17  through the perfusion pipeline  26  and the through hole  80 , and flows out of the catheter  10  through the holes in the electrode shell. 
         [0063]    The traction wire  21  is preferably made of stainless steel or nickel-titanium alloy. As shown in  FIG. 2 ,  FIG. 3  and  FIG. 5 , the distal end of the traction wire  21  extends into the third eccentric chamber  37  of the elastic tip tube  31  through the central chamber  23 , and a spring tube  29  is preferably sleeved outside a section of the traction wire  21  extending in the catheter main body  12  The spring tube  29  is preferably of a tight structure with a tightening force, and a second protective sleeve (not shown in the figure) is sleeved outside the spring tube  29 . The second protective sleeve may be made of any suitable material, preferably a polyamide material, and is used for the extension of the spring tube  29  therein. The distal end and proximal end of the second protective sleeve may be fixed on the spring tube  29  by bonding, welding or other suitable manner, such as being bonded on the spring tube  29  with UV cured adhesive. As shown in  FIG. 5 , a first protective sleeve  32  is preferably sleeved outside a section of traction wire  21  extending in the elastic tip tube  31 . The first protective sleeve  32  may be made of any suitable material, preferably a polytetrafluoroethylene material, and is provided in the elastic tip tube  31  and used for the extension of the traction wire  21  therein. 
         [0064]    As shown in  FIG. 5 , the distal end of the traction wire  21  extends into the hole  82  in the insert  74 , and the end thereof is fixed by welding, bonding or other suitable manner, preferably being fixed by welding. 
         [0065]    The proximal end of the traction wire  21  is fixed on the control handle  11  by adopting any suitable method known by those skilled in the art. For example, a method for fixing a traction wire as disclosed in U.S. Pat. No. 6,120,476 may be used. 
         [0066]    As shown in  FIG. 2 ,  FIG. 3  and  FIG. 4 , the distal end of the conducting wire  25  extends into the second eccentric chamber  36  of the elastic tip tube  31  through the central chamber  23 , and is connected with the ablation electrode  17 , the ring electrode  16  and the temperature sensor  33  respectively in a manner of welding or other suitable manner, preferably being fixed by welding. Preferably, a conduit  27  is provided outside the conducting wire  25 . 
         [0067]    The proximal end of the conducting wire  25  is fixed on the control handle  11  by adopting any suitable method known by those skilled in the art, such as being fixed on a corresponding plug by welding. 
         [0068]    In a specific implementation of the present invention, during the ablation process of the ablation electrode  17 , the nonmetallic heat insulation layer  78  is provided on the through hole  81  of the insert  74 , and the temperature sensor  33  may be provided on the inner surface of the electrode shell  71  or in the through hole of the electrode shell  71  or partially provided in the electrode shell, so the temperature detected by the ablation electrode of the present invention is closer to the temperature of the tissue under the same catheter radio-frequency ablation power and perfusion condition commonly used in clinical practice. Wherein, according to a preferred specific implementation of the present invention, the temperature sensor  33  is provided on the inner surface of the electrode shell  71 , more preferably, the temperature sensor  33  is partially provided in the electrode shell  71 , and even more preferably, the temperature sensor  33  is provided in the through hole of the electrode shell  71 . 
         [0069]      FIG. 8  is a sectional view of the ablation electrode  17  according to a further implementation of the present invention. As shown in  FIG. 8 , the ablation electrode  17  includes an electrode shell  71  and a cavity  76  therein, and the insert  74  is provided at the proximal end of the electrode shell  71 . The insert  74  may be cylindrical, disc-shaped or in other suitable shape and at least includes a through hole  81 , and the distal end of the through hole  81  extends into a through hole  79  of the electrode shell  71 . The extending section of the through hole  81  and the insert  74  may be formed integrally or separately. For example, a hollow tube is inserted into the through hole  81 , or the distal end of the through hole  81  is connected with a pipeline or other suitable structure. The proximal end of the through hole  81  is opened at the proximal end of the insert  74 . The distal end of the through hole  81  turns in the cavity  76 , extends into the through hole  79  in the side wall of the electrode shell  71 , is opened on the side wall, and is flush with the outer surface of the electrode shell  71 , as shown in  FIG. 8 . A temperature sensor  33  is provided at the distal end of the through hole  81  and is fixed by glue bonding. The insert  74  further includes a through hole  80 , and the through hole  80  is a liquid passage for inflow of perfusion liquid. The through hole  80  and the through hole  81  are communicated with the first eccentric chamber  35  and the second eccentric chamber  36  of the elastic tip tube  31  respectively. 
         [0070]    A nonmetallic heat insulation layer  78  is provided on the through hole  81 . When the extending section of the through hole  81  and the insert  74  are formed integrally and the insert  74  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the insert  74  is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. When the extending section of the through hole  81  and the insert  74  are formed separately and the extending section of the through hole  81  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the extending section of the through hole  81  of the insert is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. 
         [0071]    In the embodiment shown in  FIG. 8 , the rest structures of the catheter  10  are the same as those in the embodiments shown in  FIG. 4  and  FIG. 5 . 
         [0072]      FIG. 9  shows a structural diagram of the ablation electrode  17  according to a further implementation of the present invention. The ablation electrode  17  includes a cylindrical side wall surface  77  and a rounded top surface  75 , and may be formed separately or integrally. Holes  72  for outflow of the perfusion liquid from the ablation electrode  17  are formed in the rounded top surface  75 . Annular grooves  73  are provided in the cylindrical side wall surface  77 , and the annular grooves  73  may be provided in a conventional manner for those skilled in the art. For example, the annular grooves  73  may be provided in a manner mentioned in United States Patent US20080294158. 
         [0073]      FIG. 10  shows a sectional view of the ablation electrode  17  shown in  FIG. 9 . The ablation electrode  17  includes a cavity  76 , and an insert  74  is provided at the proximal end of the electrode shell  71 . The insert  74  is provided at the proximal end of the ablation electrode  17 . The insert  74  may be cylindrical, disc-shaped or in other suitable shape and includes a through hole  81 , and the distal end of the through hole  81  extends into the through hole  79  of the electrode shell  71 . The extending section of the through hole  81  and the insert  74  may be formed integrally or separately. For example, a hollow tube is inserted into the through hole  81 , or the distal end of the through hole  81  is connected with a pipeline or other suitable structures. The proximal end of the through hole  81  is opened at the proximal end of the insert  74 , and the distal end of the through hole  81  is opened on the outer surface of the electrode shell  71  and is flush with the outer surface of the electrode shell  71 . A temperature sensor  33  is provided at the distal end of the through hole  81  and is fixed by glue bonding. The insert  74  further includes a through hole  80 , and the through hole  80  is a liquid passage for inflow of perfusion liquid, which may be a central chamber or an eccentric chamber. 
         [0074]    The nonmetallic heat insulation layer  78  is provided on the through hole  81 . When the extending section of the through hole  81  and the insert  74  are formed integrally and the insert  74  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the insert  74  is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. When the extending section of the through hole  81  and the insert  74  are formed separately and the extending section of the through hole  81  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the extending section of the through hole  81  of the insert is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. The nonmetallic heat insulation layer  78  may completely or partially cover the inner wall and/or outer wall of the through hole  81 . Preferably, an extension tube  83  may also be provided at the distal end of the hollow tube in the through hole  80 , and may be fixed by glue bonding, welding or other suitable manner. The extension tube  83  and the hollow tube may also be formed integrally. The insert  74  may be completely placed in the cavity of the electrode shell  71 , or partially placed in the cavity of the electrode shell  71 , as shown in  FIG. 10 . 
         [0075]    In the implementations shown in  FIG. 9  and  FIG. 10 , the rest structures of the catheter  10  may be the same as those in the embodiments shown in  FIG. 4  and  FIG. 5 , or the catheter structures in United States Patent US20080294158. 
         [0076]      FIG. 11  shows a sectional view of the ablation electrode  17  according to a further implementation of the present invention; and  FIG. 12  shows a sectional view of the ablation electrode  17  in  FIG. 11 . As shown in  FIG. 11  and  FIG. 12 , the ablation electrode  17  includes an electrode shell  71  and a cavity  76  therein, and the insert  74  is provided at the proximal end of the electrode shell  71 . The insert  74  may be circular or in other suitable shape, such as cylindrical, disc-shaped and the like. The insert includes a through hole  81 , and the distal end of the through hole  81  extends into the through hole  79  of the electrode shell  71 . The extending section of the through hole  81  and the insert  74  may be formed integrally or separately. For example, a hollow tube is inserted into the through hole  81 , or the distal end of the through hole  81  is connected with a pipeline or other suitable structures. The proximal end of the through hole  81  is opened at the proximal end of the insert  74 . The distal end of the through hole  81  is opened on the outer surface of the electrode shell  71  and is flush with the outer surface of the electrode shell  71 . A temperature sensor  33  is provided at the distal end of the through hole  81  and is fixed by glue bonding. Further, a stainless steel tube is welded on the inner wall of the through hole  81 , and the distal end of the traction wire  21  extends into the stainless steel tube and is fixed by welding. 
         [0077]    As shown in  FIG. 11 , the perfusion passage is provided with a proximal end and a distal end, wherein the distal end of the perfusion passage extends into the first eccentric chamber  35  of the elastic tip tube  31  through the control handle  11  and the central chamber  23  of the catheter main body  12 , and is communicated with the liquid passage of the ablation electrode  17 . A perfusion pipeline  26  is provided in the perfusion passage, and the distal end of the perfusion pipeline  26  extends to the distal end of the central chamber  23  of the catheter main body  12  through the control handle  11  and is communicated with the first eccentric chamber  35  of the elastic tip tube  31 . There is no perfusion pipeline in the first eccentric chamber  35  of the elastic tip tube  31 , and the perfusion liquid directly enters the cavity  76  of the electrode shell  71  from the first eccentric chamber  35  and the through hole  81 . The elastic tip tube  31  may also have a structure with four or more chambers, so that the perfusion liquid may flow into the cavity  76  of the electrode shell through at least two eccentric chambers of the elastic tip tube  31 . 
         [0078]    The distal end of the conducting wire  25  is welded on the stainless steel tube, and a sealant is filled at the distal end of the conducting wire and the proximal end of the through hole  81  to avoid direct contact with the perfusion liquid. 
         [0079]    The nonmetallic heat insulation layer  78  is provided on the through hole  81 . When the extending section of the through hole  81  and the insert  74  are formed integrally and the insert  74  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the insert  74  is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. When the extending section of the through hole  81  and the insert  74  are formed separately and the extending section of the through hole  81  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the extending section of the through hole  81  of the insert is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. 
         [0080]    In the embodiment shown in  FIG. 11  and  FIG. 12 , the rest structure of the catheter  10  is the same as that in the embodiments shown in  FIG. 4  and  FIG. 5 , the embodiment shown in  FIG. 8  or the embodiments shown in  FIG. 9  and  FIG. 10 . 
         [0081]      FIG. 13  shows a sectional view of the ablation electrode  17  according to a further implementation of the present invention. As shown in  FIG. 13 , the ablation electrode  17  includes at least one liquid passage  80 , the liquid passage  80  is provided with an opening at the proximal end of the ablation electrode  17 , and the perfusion liquid may flow to the outer surface of the ablation electrode  17  through the liquid passage  80 . There are multiple ways for the perfusion liquid to flow through the ablation electrode. For example, the liquid passage is provided with a plurality of branches which extend to and are opened on the outer surface of the ablation electrode. 
         [0082]    As shown in  FIG. 13 , the ablation electrode  17  further includes a through hole  81 , and the distal end of the through hole  81  is opened on the outer surface of the electrode shell  71  and is flush with the outer surface of the electrode shell  71 . The temperature sensor  33  is provided at the distal end of the through hole  81  and is fixed by glue bonding. The ablation electrode  17  further includes a blind hole  82  in which the traction wire  21  is fixed. The through hole  80 , the through hole  81  and the blind hole  82  are communicated with the first eccentric chamber  35 , the second eccentric chamber  36  and the third eccentric chamber  37  of the elastic tip tube  31  respectively. 
         [0083]    The nonmetallic heat insulation layer  78  is completely or partially provided on the inner wall of the through hole  81 . The nonmetallic heat insulation layer  78  may be a tubular heat insulation layer inserted into the through hole  81 , or may be a nonmetallic heat insulation layer coated on the inner wall of the through hole  81 . The nonmetallic heat insulation layer  78  is made of a material with a heat insulation function, and may be made of a nonmetallic material such as a high polymer material, ceramic or other suitable nonmetallic material. The nonmetallic heat insulation layer  78  may be made of a nonmetallic material with high temperature resistance. The liquid passage  80  may also be completely or partially provided with the nonmetallic heat insulation layer  78  therein. 
         [0084]    In the implementation shown in  FIG. 13 , the rest structures of the catheter  10  are the same as those in the implementations shown in  FIG. 4  and  FIG. 5  or the catheter structures in Chinese Patent CN201020215408.8. 
         [0085]      FIG. 14  is a sectional view of the ablation electrode  17  according to a further implementation of the present invention. 
         [0086]    As shown in  FIG. 14 , the ablation electrode  17  includes an electrode shell  71  and a cavity  76  therein, and an insert  74  is provided at the proximal end of the electrode shell  71 . The insert  74  may be cylindrical, disc-shaped or in other suitable shape and at least includes a through hole  81 , and the distal end of the through hole  81  extends into a through hole  79  of the electrode shell  71 . The extending section of the through hole  81  and the insert  74  may be formed integrally or separately. For example, a hollow tube is inserted into the through hole  81 , or the distal end of the through hole  81  is connected with a pipeline or other suitable structure. The proximal end of the through hole  81  is opened at the proximal end of the insert  74 . The distal end of the through hole  81  extends to the inner surface of the electrode shell  71  and is flush with the inner surface of the electrode shell  71 , or may partially extend into the electrode shell  71 . A temperature sensor  33  is provided at the distal end of the through hole  81  and is fixed by glue bonding. In this implementation, when the insert  74  and the extending section of the through hole  81  are separated structures, a hollow tube may be provided in the through hole  81 . The distal end of the hollow tube extends to the inner surface of the electrode shell  71  and is flush with the inner surface of the electrode shell  71 , or may partially extend into the electrode shell  71 . The distal end of the hollow tube has a closed construction. The temperature sensor  33  is glue bonded and fixed at the distal end of the hollow tube. The thickness of the electrode shell where the temperature sensor is located is less than 0.2 mm. Preferably, the thickness of the electrode shell where the temperature sensor is located is less than 0.1 mm. 
         [0087]    The insert  74  further includes a through hole  80 , and the through hole  80  is a liquid passage for inflow of perfusion liquid. The through hole  80  and the through hole  81  are communicated with the first eccentric chamber  35  and the second eccentric chamber  36  of the elastic tip tube  31  respectively. 
         [0088]    A nonmetallic heat insulation layer  78  is provided on the through hole  81 . When the extending section of the through hole  81  and the insert  74  are formed integrally and the insert  74  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the insert  74  is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. When the extending section of the through hole  81  and the insert  74  are formed separately and the extending section of the through hole  81  is made of a metallic material, the nonmetallic heat insulation layer  78  is provided on the inner wall and/or outer wall of the through hole  81 . When the extending section of the through hole  81  of the insert is made of a nonmetallic material, the through hole  81  itself may be used as a nonmetallic heat insulation layer. 
         [0089]    The temperature sensor  33  and a part of the electrode shell which is not directly cooled by the perfusion liquid may be in direct contact, or may be connected through a metallic material, such as welding, or connected through a nonmetallic heat-conducting material, such as bonding through a heat-conducting glue, or connected through both a metallic material and a nonmetallic heat-conducting material, or connected through other suitable connecting methods. Therefore, the heat conductivity between the temperature sensor  33  and the outer wall of the electrode shell  71  is better than that between the temperature sensor  33  and the liquid passage. The part of the electrode shell which is not directly cooled by the perfusion liquid in the present invention refers to such a part on the electrode shell that is not in direct contact with the perfusion liquid. The liquid passage in the present invention includes a part through which the perfusion liquid flows in the ablation electrode  17 , including the hole  80 , the cavity  76  of the electrode shell  17  and the part on the electrode shell for outflow of the perfusion liquid. 
         [0090]    In the embodiment shown in  FIG. 14 , the rest structures of the catheter  10  are the same as those in the embodiment shown in  FIG. 4  and  FIG. 5 , the embodiment shown in  FIG. 9  and  FIG. 10 , the embodiment shown in  FIG. 11  and  FIG. 12  or other embodiments. 
         [0091]    The implementations of the present invention are not limited to the above-mentioned embodiments, and in order to meet other requirements of the liquid passages or requirements of mechanical structures, the form of the electrode body and/or the insert may be changed (e.g. the diameter is changed, the number of passages is adjusted, and the length is changed), so as to meet the requirements upon cooling and temperature measuring during ablation and the requirements upon the connection between the ablation electrode and the catheter main body. Various variations and improvements of the present invention in forms and details may be made by those skilled in the art without departing from the spirit and scope of the present invention, all of which are considered to fall into the protection scope of the present invention.