Patent ID: 8798742

Claim:
An implantable medical device, comprising: a sensing circuit adapted to sense a cardiac signal, the sensing circuit including a signal filter adapted to produce a filtered cardiac signal having a signal frequency band by filtering the sensed cardiac signal; a noise estimation circuit coupled to the sensing circuit, the noise estimation circuit adapted to dynamically generate a noise floor using a noise signal having a noise frequency band, the noise floor being an estimate of noise level in the signal frequency band, the noise estimation circuit including a noise filter adapted to produce the noise signal having the noise frequency band by filtering the sensed cardiac signal, the noise frequency band being substantially different from the signal frequency band; and an event detection circuit coupled to the sensing circuit and the noise estimation circuit, the event detection circuit adapted to dynamically adjust a detection threshold using at least the filtered cardiac signal and the noise floor and to detect cardiac electrical events using the filtered cardiac signal and the detection threshold, the noise floor used as a minimum value of the detection threshold.