Method and apparatus for sensing R-waves using both near field and far field sensing simultaneously

An R-wave sensing system for an implantable cardiac arrythmia therapy device, the system comprising:

• local detection electrodes that sense a local electrical signal representing cardiac activity in a local area of a patient's heart;
• global detection electrodes that sense a global electrical signal representing cardiac activity in a global area of the patient's heart;
• a first amplifier that amplifies the local electrical signal;
• a second amplifier that amplifies the global electrical signal;
• a first filter that filters the local electrical signal;
• a second filter that filters the global electrical signal;
• a converter that converts the local electrical signal into a digital signal so as to generate a masking pulse;
• and
• a multiplier that multiplies the masking pulse with the filtered global electrical signal to produce a correlation signal representative of an R-wave sensed in the patient's heart.

An R-wave sensing system for an implantable cardiac arrythmia therapy device, the system comprising:

• local detection means for sensing a local electrical signal representing cardiac activity in a local area of a patient's heart;
• global detection means for sensing a global electrical signal representing cardiac activity in a global area of the patient's heart;
• a first filtering means for filtering the local electrical signal so as to generate a masking pulse;
• a second filtering means for filtering the global electrical signal;
• and
• multiplication means for multiplying the masking pulse with the filtered global electrical signal to produce a correlation signal representative of an R-wave sensed in the patient's heart.

A method of sensing R-waves in an implantable cardiac arrythmia therapy device, the method comprising the steps of:

• detecting local electrical signals of a patient's heart representing cardiac activity in a local area of the heart;
• detecting global electrical signals representing cardiac activity in a global area of the patient's heart;
• filtering the local electrical signals so as to generate a masking signal;
• filtering the global electrical signals;
• and
• combining the masking signal with the filtered global signals to produce a correlation signal representative of an R-wave sensed in the patient's heart.