Subcutaneous cardiac sensing and stimulation system

Abstract

Cardiac systems and methods using ECG and blood information for arrhythmia detection and discrimination. Detection circuitry is configured to produce an ECG. An implantable blood sensor configured to produce a blood sensor signal is coupled to a processor. The processor is coupled to the detection and energy delivery circuitry, and used to evaluate and treat cardiac rhythms using both the cardiac electrophysiologic and blood sensor signals. The blood sensor is configured for subcutaneous non-intrathoracic placement and provided in or on the housing, on a lead coupled to the housing, and/or separate to the housing and coupled to the processor via hardwire or wireless link. The blood sensor may be configured for optical sensing, using a blood oxygen saturation sensor or pulse oximeter. A cardiac rhythm may be evaluated using the electrocardiogram signal and the blood sensor signal, and tachyarrhythmias may be treated after confirmation using the blood sense signal.

1 . (canceled) 
     
     
         2 . An implantable subcutaneous defibrillator comprising:
 a housing configured for subcutaneous placement;   detection circuitry provided in the housing and configured to produce an electrocardiogram signal;   energy delivery circuitry provided in the housing and configured to provide a defibrillation therapy output;   at least one electrode configured for subcutaneous non-intrathoracic placement and coupled to the detection and energy delivery circuitry;   wherein the implantable subcutaneous defibrillator is configured to communicate with a second implantable device;   wherein the implantable subcutaneous defibrillator is configured to operate in the following manner:   using the detection circuitry, determine ether a potentially treatable condition is occurring;   using the communications circuitry, request information from the second implantable device relating to the potentially treatable condition; and   after requesting information from the second implantable device, either:
 confirm the potentially treatable condition and deliver therapy using the energy delivery circuitry; or 
 using information received from the second implantable device, determine that the potentially treatable condition is not to be treated. 
   
     
     
         3 . The implantable subcutaneous defibrillator of  claim 2  further comprising communications circuitry for establishing a short range wireless communication link. 
     
     
         4 . The implantable subcutaneous defibrillator of  claim 2  wherein the second implantable device is a non-electrophysiologic sensor, and the implantable subcutaneous defibrillator is configured to request data related to sensed non-electrophysiologic conditions from the second implantable device. 
     
     
         5 . The implantable subcutaneous defibrillator of  claim 4  wherein the second implantable device is configured for pulse oximetry, and the implantable subcutaneous defibrillator is configured to compare electrocardiogram signals from the detection circuitry to pulse oximetry data from the second implantable device. 
     
     
         6 . The implantable subcutaneous defibrillator of  claim 4  wherein the second implantable device is configured for sensing an acoustic signal, and the implantable subcutaneous defibrillator is configured to compare electrocardiogram signals from the detection circuitry to acoustic signal data from the second implantable device. 
     
     
         7 . The implantable subcutaneous defibrillator of  claim 2  second implantable device is an electrophysiologic sensor, and the implantable subcutaneous defibrillator is configured to request data related to sensed electrophysiologic conditions from the second implantable device. 
     
     
         8 . A method of making a therapy decision in an implantable subcutaneous defibrillator having a housing for subcutaneous placement with at least one electrode coupled thereto and detection and therapy delivery circuitry therein, the method comprising:
 sensing an electrocardiogram via the at least one electrode and using the detection circuitry;   determining a cardiac arrhythmia is present by analyzing the electrocardiogram;   obtaining information from a second implantable device;   confirming the presence of the cardiac arrhythmia using the information from the second implantable device; and   delivering therapy in response to the confirmed cardiac arrhythmia.   
     
     
         9 . The method of  claim 8  wherein the second implantable device is a non-electrophysiologic signal detector, and the step of confirming the presence of the cardiac arrhythmia includes setting a detection window and evaluating a non-electrophysiologic signal from the second implantable device within the detection window. 
     
     
         10 . The method of  claim 9  wherein the second implantable device is configured to sense blood oxygen levels. 
     
     
         11 . The method of  claim 9  wherein the second implantable device is configured to sense pulsatile blood volume. 
     
     
         12 . The method of  claim 8  wherein the second implantable device is a non-electrophysiologic signal detector, and the step of confirming the presence of the cardiac arrhythmia includes analyzing a correlation between the electrocardiogram signal and the non-electrophysiologic signal data. 
     
     
         13 . The method of  claim 12  wherein the second implantable device is configured to sense blood oxygen levels. 
     
     
         14 . The method of  claim 12  wherein the second implantable device is configured to sense pulsatile blood volume. 
     
     
         15 . A method of making a therapy decision in an implantable subcutaneous defibrillator having a housing for subcutaneous placement with at least one electrode coupled thereto and detection and therapy delivery circuitry therein, the method comprising:
 sensing an electrocardiogram via the at least one electrode and using the detection circuitry;   determining a cardiac arrhythmia is present by analyzing the electrocardiogram;   obtaining information from a second implantable device;   rejecting the presence of the cardiac arrhythmia using the information from the second implantable device; and   inhibiting therapy in response to the confirmed cardiac arrhythmia.   
     
     
         16 . The method of  claim 15  wherein the second implantable device is a non-electrophysiologic signal detector, and the step of rejecting the presence of the cardiac arrhythmia includes setting a detection window and evaluating a non-electrophysiologic signal from the second implantable device within the detection window. 
     
     
         17 . The method of  claim 16  wherein the second implantable device is configured to sense blood oxygen levels. 
     
     
         18 . The method of  claim 16  wherein the second implantable device is configured to sense pulsatile blood volume. 
     
     
         19 . The method of  claim 15  wherein the second implantable device is a non-electrophysiologic signal detector, and the step of confirming the presence of the cardiac arrhythmia includes analyzing a correlation between the electrocardiogram signal and the non-electrophysiologic signal data. 
     
     
         20 . The method of  claim 19  wherein the second implantable device is configured to sense blood oxygen levels. 
     
     
         21 . The method of  claim 19  wherein the second implantable device is configured to sense pulsatile blood volume.