Cardiac pacing/sensing lead providing far-field signal rejection

Abstract

A proximal end of a lead body carries a connector assembly. A first electrical conductor within the lead body electrically connects a tip electrode to a first electrical contact on the connector assembly. A collar electrode is carried by a distal end portion of the lead body. A second electrical conductor within the lead body electrically connects the collar electrode to a second electrical contact on the connector assembly. A ring electrode, carried by the distal end portion of the lead body, is disposed proximally of the collar electrode in spaced-apart relationship thereto and is connected through a switching device to a node point along the second conductor. The switching device has a first state permitting an electrical current to be conducted between the ring electrode and the node point and a second state in which the ring electrode is electrically isolated from the node point. Preferably, the switching device comprises a diode.

1 . A cardiac lead for transmitting electrical pacing and sensing signals between an electrical medical device and selected cardiac tissue, the lead comprising: 
 a lead body having a proximal end, a distal tip and a distal end portion extending proximally from the distal tip, the proximal end of the lead body carrying a connector assembly electrically connectable to the electrical medical device;    a helical screw-in pacing/sensing electrode extendable and retractable relative to the distal tip of the lead body;    a first electrical conductor within the lead body electrically connecting the helical screw-in pacing/sensing electrode to a first electrical contact on the connector assembly;    a collar pacing/sensing electrode carried by the distal end portion of the lead body at the distal tip thereof;    a second electrical conductor within the lead body electrically connecting the collar pacing/sensing electrode to a second electrical contact on the connector assembly;    a ring pacing/sensing electrode carried by the distal end portion of the lead body, the ring pacing/sensing electrode being disposed proximally of the collar pacing/sensing electrode in spaced-apart relationship thereto, the ring pacing/sensing electrode being connected through a switching device to a node point along the second electrical conductor to electrically separate a pacing dipole from a sensing dipole; and    a resistor connected between the node point and the collar pacing/sensing electrode;    wherein pacing is performed between the helical pacing/sensing electrode and the ring pacing/sensing electrode, wherein a pacing signal is applied to the first electrical conductor and hence to the helical pacing/sensing electrode and a return pacing signal flows through the switching device from the ring pacing/sensing electrode and to the second conductor, and wherein the resistor assures that no significant return pacing current is drawn through the collar pacing/sensing electrode; and    wherein sensing is performed between the helical pacing/sensing electrode and the collar pacing/sensing electrode, wherein during sensing the sensing signal passes the resistor from the collar pacing/sensing electrode and to the second electrical conductor, and wherein during sensing the switching device blocks the sensing signal from the ring pacing/sensing electrode.    
   
   
       2 . The lead of  claim 1  in which: 
 the helical screw-in pacing/sensing electrode and the collar pacing/sensing electrode comprise a sensing dipole.    
   
   
       3 . The lead of  claim 1  in which: 
 the helical screw-in pacing/sensing electrode and the ring pacing/sensing electrode comprise a pacing dipole.    
   
   
       4 . The lead of  claim 1  in which: 
 the switching device comprises a diode.    
   
   
       5 . The lead of  claim 4  in which: 
 the diode is a small form factor, low forward voltage drop diode.    
   
   
       6 . The lead of  claim 4  in which: 
 the diode comprises an anode electrically connected to the node point and a cathode electrically connected to the ring pacing/sensing electrode.    
   
   
       7 . The lead of  claim 1  in which: 
 the lead body carries a shocking electrode positioned proximally of the ring pacing/sensing electrode, the shocking electrode being adapted to be electrically connected to a separate contact on the connector assembly.    
   
   
       8 . A cardiac lead for transmitting electrical pacing and sensing signals between an electrical medical device and selected cardiac tissue, the lead comprising: 
 a lead body having a proximal end, a distal tip and a distal end portion extending proximally from the distal tip, the proximal end of the lead body carrying a connector assembly electrically connectable to the electrical medical device;    a helical screw-in pacing/sensing electrode extendable and retractable relative to the distal tip of the lead body;    a first electrical conductor within the lead body electrically connecting the helical screw-in pacing/sensing electrode to a first electrical contact on the connector assembly;    a collar pacing/sensing electrode carried by the distal end portion of the lead body at the distal tip thereof;    a second electrical conductor within the lead body electrically connecting the collar pacing/sensing electrode to a second electrical contact on the connector assembly;    a ring pacing/sensing electrode carried by the distal end portion of the lead body, the ring pacing/sensing electrode being disposed proximally of the collar pacing/sensing electrode in spaced-apart relationship thereto, the ring pacing/sensing electrode being connected through a switching device to a node point along the second conductor, the switching device having a first state permitting an electrical current to be conducted between the ring pacing/sensing electrode and the node point and a second state in which the ring pacing/sensing electrode is electrically isolated from the node point; and    an electrical resistor disposed between the collar pacing/sensing electrode and the node point.    
   
   
       9 . The lead of  claim 8  in which: 
 the helical screw-in pacing/sensing electrode and the collar pacing/sensing electrode comprise a sensing dipole.    
   
   
       10 . The lead of  claim 8  in which: 
 the helical screw-in pacing/sensing electrode and the ring pacing/sensing electrode comprise a pacing dipole.    
   
   
       11 . The lead of  claim 8  in which: 
 the switching device comprises a diode.    
   
   
       12 . The lead of  claim 11  in which: 
 the diode is a small form factor, low forward voltage drop diode.    
   
   
       13 . A cardiac lead for transmitting electrical pacing and sensing signals between an electrical medical device and selected cardiac tissue, the lead comprising: 
 a lead body having a proximal end, a distal tip and a distal end portion extending proximally from the distal tip, the proximal end of the lead body carrying a connector assembly electrically connectable to the electrical medical device;    a first pacing/sensing electrode at the distal tip of the lead body;    a first electrical conductor within the lead body electrically connecting the first pacing/sensing electrode to a first electrical contact on the connector assembly;    a second pacing/sensing electrode carried by the distal end portion of the lead body at the distal tip thereof;    a second electrical conductor within the lead body electrically connecting the second electrode to a second electrical contact on the connector assembly;    a third pacing/sensing electrode carried by the distal end portion of the lead body, the third pacing/sensing electrode being disposed proximally of the second electrode in spaced-apart relationship thereto, and a switching device connecting the third electrode to a node point along the second conductor, the switching device having a first state permitting an electrical current to be conducted between the third electrode and the node point and a second state in which the third electrode is electrically isolated from the node point; and    an electrical resistor disposed between the collar electrode and the node point.    
   
   
       14 . The lead of  claim 13  in which: 
 the switching device comprises a diode.    
   
   
       15 . The lead of  claim 13  in which: 
 the diode comprises an anode electrically connected to the node point and a cathode electrically connected to the third pacing/sensing electrode.    
   
   
       16 . The lead of  claim 13  in which: 
 the lead body carries a shocking electrode positioned proximally of the third pacing/sensing electrode, the shocking electrode being adapted to be electrically connected to a separate contact on the connector assembly.    
   
   
       17 . The lead of  claim 13  in which: 
 the first sensing/pacing electrode and the second pacing/sensing electrode comprise a sensing dipole.    
   
   
       18 . The lead of  claim 13  in which: 
 the first pacing/sensing electrode and the third pacing/sensing electrode comprise a pacing dipole.    
   
   
       19 . The lead of  claim 13  in which: 
 the interelectrode spacing between a distal extremity of the third pacing/sensing electrode and a proximal extremity of the second pacing/sensing electrode ranges from 5 to 30 mm.    
   
   
       20 . The lead of  claim 13  in which: 
 the first pacing/sensing electrode is a helical screw-in electrode, the second pacing/sensing electrode is a collar electrode, and the third pacing/sensing electrode is a ring electrode.