Implantable intravenous cardiac stimulation system with pulse generator housing serving as optional additional electrode

Abstract

Described is an implantable pulse generator housing for enclosing and containing pulse generator circuitry. The housing is formed of electrically conductive metal defining an electrically conductive outer surface which may be connected to the pulse generator circuitry for delivering electrical energy to the heart. A programmable switch operable by the pulse generator circuitry is provided to discharge electrical pulses between selected electrodes and the conductive pulse generator housing in accordance with whether a first or second cardiac condition is detected.

1 . An apparatus, comprising: 
 a lead having proximal and distal electrodes for disposition near the heart;    an implantable pulse generator including pulse generator circuitry for delivering electrical pulses to the heart;    wherein the pulse generator circuitry includes cardiac detection circuitry for detecting cardiac conditions based upon cardiac rhythm;    a conductive pulse generator housing enclosing the pulse generator circuitry;    a programmable switch operable by the pulse generator circuitry to discharge electrical pulses between selected ones of the proximal and distal electrodes and the conductive pulse generator housing in accordance with whether a first or second cardiac condition is detected.    
   
   
       2 . The apparatus of  claim 1  wherein the programmable switch is operable to discharge a first type of electrical pulse between the proximal and distal electrodes when a first cardiac condition is detected and to discharge a second type of electrical pulse between the conductive pulse generator housing and the proximal electrode when a second cardiac condition is detected.  
   
   
       3 . The apparatus of  claim 2  wherein the first and second types of electrical pulses are both pacing pulses.  
   
   
       4 . The apparatus of  claim 2  wherein the first type of electrical pulse is a pacing pulse and the second type of electrical pulse is a defibrillation pulse.  
   
   
       5 . The apparatus of  claim 4  wherein the first heart condition is bradycardia and the second heart condition is fibrillation.  
   
   
       6 . The apparatus of  claim 4  wherein the first heart condition is tachycardia and the second heart condition is fibrillation.  
   
   
       7 . The apparatus of  claim 1  wherein the programmable switch is operable to discharge a first type of electrical pulse between the proximal and distal electrodes when a first cardiac condition is detected and to discharge a second type of electrical pulse between the conductive pulse generator housing and the distal electrode when a second cardiac condition is detected.  
   
   
       8 . The apparatus of  claim 7  wherein the first and second types of electrical pulses are both pacing pulses.  
   
   
       9 . The apparatus of  claim 7  wherein the first type of electrical pulse is a pacing pulse and the second type of electrical pulse is a defibrillation pulse.  
   
   
       10 . The apparatus of  claim 9  wherein the first heart condition is bradycardia and the second heart condition is fibrillation.  
   
   
       11 . The apparatus of  claim 9  wherein the first heart condition is tachycardia and the second heart condition is fibrillation  
   
   
       12 . The apparatus of  claim 1  wherein the programmable switch is operable to discharge a first type of electrical pulse between the proximal and distal electrodes when a first cardiac condition is detected and to discharge a second type of electrical pulse between the conductive pulse generator housing and the proximal and distal electrodes connected in common when a second cardiac condition is detected.  
   
   
       13 . The apparatus of  claim 12  wherein the first and second types of electrical pulses are both pacing pulses.  
   
   
       14 . The apparatus of  claim 12  wherein the first type of electrical pulse is a pacing pulse and the second type of electrical pulse is a defibrillation pulse.  
   
   
       15 . The apparatus of  claim 14  wherein the first heart condition is bradycardia and the second heart condition is fibrillation.  
   
   
       16 . The apparatus of  claim 14  wherein the first heart condition is tachycardia and the second heart condition is fibrillation.  
   
   
       17 . A method comprising: 
 sensing cardiac activity in order to detect a first or second cardiac condition; and,    operating a programmable switch so that an electrical pulse is delivered between selected ones of a first electrode, a second electrode, and a conductive housing enclosing pulse generator circuitry in accordance with whether a first or second cardiac condition is detected.    
   
   
       18 . The method of  claim 17  further comprising operating the programmable switch to discharge a first type of electrical pulse between the first and second electrodes when a first cardiac condition is detected and to discharge a second type of electrical pulse between the conductive pulse generator housing and the first electrode when a second cardiac condition is detected.  
   
   
       19 . The method of  claim 18  wherein the first and second types of electrical pulses are both pacing pulses.  
   
   
       20 . The method of  claim 18  wherein the first type of electrical pulse is a pacing pulse and the second type of electrical pulse is a defibrillation pulse.