Patent ID: 8280510

Claim:
A method for operating a cardiac 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 buffer for storing a plurality of 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, storing the indeterminately classified BB interval in the buffer, and returning to step 1, 3) if the buffer contains N intervals, computing a statistic from the stored BB intervals and 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 a 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 metric from the filtered BB intervals.