Patent ID: 8396542

Claim:
A cardiac monitor for estimating the value of a heart signal parameter, the monitor comprising: (a) a sensor for sensing an analog signal from a human heart; (b) a device coupled to the sensor, the device having an analog-to-digital circuit system contained therein for digitizing the analog signal to produce a digitized waveform; and (c) a processor electrically coupled to the analog-to-digital circuit system, said processor configured to: (i) analyze the waveform to detect a plurality of beats; (ii) analyze the plurality of beats to generate a corresponding plurality of values of a heart signal parameter; (iii) compute a parameter value time series which is a running estimate of the value of the heart signal parameter by low pass filtering at least a portion of the plurality of values of the heart signal parameter; (iv) compute a long term average value of the heart signal parameter from the time series over a time period that is at least ten minutes long; (v) measure the value of the heart signal parameter for a current beat that is one of the plurality of beats, thereby generating a current beat value; (vi) compare the current beat value with the long term average value of the heart signal parameter, thereby generating a first comparison result indicative of the distance between the current beat value and the long term average value; and, (vii) based on the first comparison result, selectively update the low pass filtered time series based on the value of the heart signal parameter for the current beat, thereby generating a new estimate of the value of the heart signal parameter responsive to the addition of the value of the heart signal parameter for the current beat to the low pass filtered time series.