Patent ID: 7155275

Claim:
A cardiac sensing system, comprising: a sensing circuit to sense a cardiac signal, the sensing circuit including a signal filter configured to produce a filtered cardiac signal based on the cardiac signal, the filtered cardiac signal having a signal frequency band and a signal amplitude; a noise estimation circuit coupled to the sensing circuit, the noise estimation circuit including: a noise filter configured to produce a noise signal based on the cardiac signal, the noise signal having a noise frequency band substantially different from the signal frequency band; and a noise floor generator adapted to produce a dynamic noise floor based on the noise signal; and an event detection circuit coupled to the sensing circuit and the noise estimation circuit, the event detection circuit including: a threshold circuit adapted to dynamically produce a detection threshold based on at least the filtered cardiac signal and the dynamic noise floor; and a comparator having a first input to receive the filtered cardiac signal, a second input to receive a detection threshold, and an output to indicate a detection of a cardiac electrical event based on a comparison between the signal amplitude and the detection threshold.