Patent ID: 7970467

Claim:
A method for operating an implantable medical device, comprising: sensing electrical activity in a cardiac chamber and generating a chamber sense signal when the sensed electrical activity exceeds a predetermined threshold; measuring time intervals between each pair of successive chamber senses, referred to as BB intervals, the measured BB intervals constituting a BB time series; filtering the BB intervals to exclude particular BB intervals as ectopic using a first-in-first-out buffer for storing a plurality of previous BB intervals and from which a statistic is computed, where the buffer can contain a maximum number N of such preceding BB intervals, by: 1) acquiring a present BB interval, 2) if the buffer contains less than N intervals, classifying the present BB interval as indeterminate, updating the buffer with the indeterminately classified BB interval, and returning to step 1, 3) if the buffer contains N intervals, comparing the present BB interval to the computed statistic, 4) excluding the present BB interval as an ectopic interval if the present BB interval is greater or less than the computed statistic by the specified threshold value, removing the oldest BB interval from the buffer, and returning to step 1, 5) updating the buffer by removing the oldest BB interval and storing the present BB interval therein if the present BB interval is not excluded as ectopic and then returning to step 1; and, computing a heart rate variability metrics from the filtered BB intervals.