Method and apparatus for reducing defibrillation threshold

Abstract

An antitachyarrhythmia system uses vagal nerve stimulation in combination with one or more additional techniques to lower the defibrillation threshold (DFT). Examples of such additional techniques include using electrical shock waveforms each including a plurality of pulses and using defibrillation electrode configurations each including an electrode placed in the coronary sinus or coronary vein.

1 . A system configured to be coupled to a heart including a right atrium (RA) connected to a superior vena cava (SVC), a right ventricle (RV), a left ventricle (LV), a coronary sinus, and a coronary vein, the system comprising:
 a sensor configured to detect a cardiac activity indicated for a defibrillation shock;   a vagal nerve stimulator configured to deliver vagal nerve stimulation to lower a defibrillation threshold in preparation for delivering the defibrillation shock;   a plurality of defibrillation electrodes including at least one LV electrode configured to be placed in the coronary sinus or coronary vein; and   a defibrillator configured to deliver the defibrillation shock to the heart through the plurality of defibrillation electrodes.   
   
   
       2 . The system of  claim 1 , comprising an implantable housing configured to house both the vagal nerve stimulator and the defibrillator. 
   
   
       3 . The system of  claim 1 , comprising a first implantable housing configured to house the vagal nerve stimulator and a second implantable housing configured to house the defibrillator. 
   
   
       4 . The system of  claim 1 , comprising a controller configured to initiate and time a neurostimulation period in response to the detection of the cardiac activity, and wherein the vagal nerve stimulator is configured to deliver the vagal nerve stimulation during the neurostimulation period. 
   
   
       5 . The system of  claim 4 , wherein the controller is configured to initiate the delivery of the defibrillation shock in response to an expiration of the neurostimulation period. 
   
   
       6 . The system of  claim 5 , wherein the controller is configured to initiate the delivery of the defibrillation shock if the cardiac activity remains detected at the end of the neurostimulation period. 
   
   
       7 . The system of  claim 4 , wherein the controller is configured to control a waveform of the defibrillation shock, the waveform including a plurality of pulses. 
   
   
       8 . The system of  claim 7 , wherein the controller is configured to control a waveform of the defibrillation shock, the waveform including an auxiliary pulse followed by a primary pulse. 
   
   
       9 . The system of  claim 8 , wherein the controller is configured to time an interpulse interval between the auxiliary pulse and the primary pulse. 
   
   
       10 . The system of  claim 8 , comprising a plurality of electrodes coupled to the defibrillator, the plurality of electrodes including:
 an auxiliary electrode set through which the auxiliary pulse is delivered; and   a primary electrode set through which the primary pulse is delivered,   wherein the auxiliary electrode set is different from the primary electrode set by at least one electrode.   
   
   
       11 . The system of  claim 1 , comprising an implantable housing and a plurality of electrodes, the implantable housing configured to house at least the defibrillator, the plurality of electrodes coupled to the defibrillator and including:
 the at least one LV electrode;   a supraventricular defibrillation electrode configured to be placed in one or more of the SVC and the RA;   an RV defibrillation electrode configured to be placed in the RV; and   a can electrode including at least a portion of the implantable housing.   
   
   
       12 . The system of  claim 11 , wherein the plurality of electrodes are connected to the defibrillator such that the RV defibrillation electrode is used as a cathode for delivering the defibrillation shock, and the at least one LV electrode, the SVC defibrillation electrode, and the can electrode are electrically wired to be used as an anode for delivering the defibrillation shock. 
   
   
       13 . The system of  claim 11 , comprising a lead including a primary end, a distal end, and an elongate body coupled between the primary end and the distal end, the primary end configured to be coupled to the defibrillator, the distal end including the at least one LV electrode, the lead configured to allow the distal end to be placed in the coronary sinus. 
   
   
       14 . The system of  claim 11 , comprising a lead including a primary end, a distal end, and an elongate body coupled between the primary end and the distal end, the primary end configured to be coupled to the defibrillator, the distal end including the at least one LV electrode, the lead configured to allow the distal end to be placed in the coronary vein. 
   
   
       15 . A method for defibrillating a heart including a right atrium (RA) connected to a superior vena cava (SVC), a right ventricle (RV), a left ventricle (LV), a coronary sinus, and a coronary vein, comprising:
 detecting a cardiac activity indicated for a defibrillation shock;   applying neural stimulation to lower a defibrillation threshold in preparation for the defibrillation shock; and   delivering the defibrillation shock using a plurality of defibrillation electrodes including at least one LV electrode placed in the coronary sinus or coronary vein.   
   
   
       16 . The method of  claim 15 , comprising:
 initiating and timing a neurostimulation period in response to the detection of the cardiac activity; and   delivering a vagal nerve stimulation during the neurostimulation period.   
   
   
       17 . The method of  claim 16 , comprising establishing the neurostimulation period to a period between 1 second and 20 seconds. 
   
   
       18 . The method of  claim 16 , comprising initiating the delivery of the defibrillation shock in response to an expiration of the neurostimulation period. 
   
   
       19 . The method of  claim 18 , comprising initiating the delivery of the defibrillation shock if the cardiac activity sustains at the end of the neurostimulation period. 
   
   
       20 . The method of  claim 15 , wherein delivering the defibrillation shock comprises delivering a defibrillation shock having a waveform including a plurality of pulses. 
   
   
       21 . The method of  claim 20 , wherein delivering the defibrillation shock having the waveform including the plurality of pulses comprises delivering a defibrillation shock having a waveform including an auxiliary pulse followed by a primary pulse, and wherein delivering the defibrillation shock using the plurality of defibrillation electrodes comprises delivering the auxiliary pulse using an auxiliary electrode set and delivering the primary pulse using a primary electrode set, the auxiliary electrode set different from the primary electrode set by at least one electrode. 
   
   
       22 . The method of  claim 21 , comprising controlling an interpulse interval between the auxiliary pulse and the primary pulse. 
   
   
       23 . The method of  claim 22 , comprising setting the interpulse interval to a time interval between 0 and 20 milliseconds. 
   
   
       24 . The method of  claim 15 , wherein delivering the defibrillation shock using the plurality of defibrillation electrodes comprises using the at least one LV electrode, a supraventricular defibrillation electrode placed in one or more of the SVC and the RA, an RV defibrillation electrode placed in the RV, and a can electrode including at least a portion of an implantable housing configured to house at least a defibrillator from which the defibrillation is delivered. 
   
   
       25 . The method of  claim 24 , wherein delivering the defibrillation shock using the plurality of defibrillation electrodes comprises:
 using the RV defibrillation electrode as a cathode; and   using the at least one LV electrode, the SVC defibrillation electrode, and the can electrode as an anode, the at least one LV electrode, the SVC defibrillation electrode, and the can electrode electrically wired to each other.   
   
   
       26 . The method of  claim 24 , wherein using the at least one LV electrode comprises using an electrode placed in the coronary sinus. 
   
   
       27 . The method of  claim 24 , wherein using the at least one LV electrode comprises using an electrode placed in the coronary vein. 
   
   
       28 . A system coupled to a heart including a right atrium (RA) connected to a superior vena cava (SVC), a right ventricle (RV), a left ventricle (LV), a coronary sinus, and a coronary vein, the system comprising:
 means for detecting a cardiac activity indicated for a defibrillation shock;   means for applying neural stimulation to lower a defibrillation threshold in preparation for the defibrillation shock; and   means for subcutaneously delivering the defibrillation shock using a plurality of defibrillation electrodes including at least one LV electrode placed in the coronary sinus or coronary vein.