Apparatus and method for occluding a vessel by rf embolization

Abstract

An RF ablation system includes an electrode element of elongate form and a cathode pad. A control unit includes a processing unit, a power unit and, optionally, a temperature sensor and/or an impedance sensor. The control unit in one embodiment carries out RF ablation in at least two phases, the first phase at a higher energy level and a second phase, after at least partial retraction of the anode element, at a second lower phase in order to close any remaining lumen within a blood clot formed within the vessel during the first phase. Other embodiments provide for sensing retraction of the anode terminal and effecting RF ablation during and/or after the retraction process in order to create a more effective occlusion barrier.

1 . An apparatus for closing a blood vessel, the apparatus comprising:
 an elongate electrode element for being passed endoluminally to a treatment site and having at least one electrical terminal at a distal end thereof;   a detection unit for detecting at least one operational change at the at least one electrical terminal; and   a control unit connected to the detection unit; wherein the control unit is programmed:
 to supply energy to the electrode element in a first step at a first power level to heat blood within the blood vessel to cause a primary blood clot formation around the electrical terminal, the first power level being substantially constant during the first step, 
 to retract the electrical terminal a distance in a proximal direction, and 
 to supply energy to the electrode element in a second step at a second power level lower than the first power level to cause a secondary blood clot formation within the primary blood clot, the second power level being substantially constant during the second step. 
   
     
     
         2 . The apparatus according to  claim 1 , wherein the control unit is programmed to detect at least one operational change at the at least one electrical terminal. 
     
     
         3 . The apparatus according to  claim 1 , wherein the control unit is operable to command a partial retraction of the electrode element in a proximal direction on detection of an operational change at the at least one electrical terminal. 
     
     
         4 . The apparatus according to  claim 3 , including a positioning unit coupled to the control unit, the positioning unit being operable to effect said partial retraction of the electrode element in a proximal direction on detection of said operational change. 
     
     
         5 . The apparatus according to  claim 3 , wherein the control unit is operable to generate a notification to effect said partial retraction of the electrode element. 
     
     
         6 . The apparatus according to  claim 1 , including an electrode position sensor coupled to the control unit, wherein the control unit is operable to control the power supply to supply energy to the electrode element at the or a second power level lower than the first power level when partial retraction of the electrode element has been detected. 
     
     
         7 . The apparatus according to  claim 6 , wherein the control unit is operable to command the power supply to supply power to the electrode element until the electrode element has been retracted by a predetermined distance. 
     
     
         8 . The apparatus according to  claim 7 , wherein the predetermined distance is equivalent to a desired length of closure of the vessel. 
     
     
         9 . The apparatus according to  claim 2 , wherein the operational change includes at least one of: change in measured impedance and change in temperature. 
     
     
         10 . The apparatus according to  claim 9 , including a temperature sensor at the distal end of the electrode element. 
     
     
         11 . The apparatus according to  claim 1 , wherein the electrode element includes an anode terminal, the apparatus including a cathode pad; or the electrode element includes anode and cathode terminals. 
     
     
         12 . A method of closing a blood vessel by means of apparatus including an elongate electrode element for being passed endoluminally to a treatment site and having at least one electrical terminal at a distal end thereof, the method including the steps of:
 supplying energy to the electrode element in a first step at a first power level to cause a primary blood clot formation around the electrical terminal, the first power level being substantially constant during the first step;   retracting the elongate electrode a distance in a proximal direction; and   supplying energy to the electrode element in a second step at a second power level lower than the first power level to cause a secondary blood clot formation within the primary blood clot, the second power level being substantially constant during the second step.   
     
     
         13 . The method according to  claim 12 , further including detecting at least one operational change at the at least one electrical terminal 
     
     
         14 . The method according to  claim 13 , including the step of partially retracting the electrode element in a proximal direction on detection of the operational change. 
     
     
         15 . The method according to  claim 12 , including the step of generating a user notification on detection of the operational change in the at least one electrical terminal. 
     
     
         16 . The method according to  claim 12 , including the step of detecting partial retraction of the electrode element. 
     
     
         17 . A method according to  claim 12 , wherein the electrode element is retracted by a predetermined distance while supplying power thereto. 
     
     
         18 . The method according to  claim 17 , wherein the predetermined distance is equivalent to a desired length of closure of the vessel. 
     
     
         19 . The method according to  claim 13 , wherein the operational change includes at least one of: change in measured impedance and change in temperature.