Patent ID: 8135456

Claim:
A cardiac rhythm monitoring device comprising: electrodes adapted to be coupled to a patient to sense cardiac electrical activity; and a processor coupled to the electrodes to receive the electrical activity and programmed to detect ventricular events within the electrical activity, wherein a plurality of successive detected ventricular events define a first beat window; and for the first beat window: calculate RR intervals for each pair of adjacent ventricular events; calculate the differences (dRR) between successive RR intervals; determine a first probability of AF based on the presence of irregularity of the ventricular events, wherein to determine the first probability the programmer is further programmed to convert the dRR values into bin values based on a plurality of bin thresholds; calculate a transition measurement between successive bin values; calculate a sample chain of statistics using the transition measurements; compare the sample chain of statistics to a known AF chain of statistics and to a known non-AF chain of statistics; determine a measure of AF quality based on the comparisons; calculate a heart rate index based on the RR intervals; use a look-up table that correlates AF quality and heart rate index to a probability of AF to determine the first probability of AF; determine a second probability of AF based on variances of R-R intervals of the ventricular events, wherein to determine the second probability the programmer is further programmed to calculate a first variance over positive and negative dRR values; calculate a second variance only over the negative dRR values; calculate a third variance only over the positive dRR values; use a look-up table that correlates the first, second and third variances to a probability of AF to determine the second probability of AF; and combine the first and second probabilities of AF to obtain a first-beat-window combined probability of AF, wherein the combined probability of AF ranges between a minimum value and a maximum value; compare the combined probability of AF to an AF trigger threshold, wherein the AF trigger threshold is a predetermined value between the minimum value and the maximum value; and detect AF onset when the first-beat-window combined probability of AF is greater than or equal to the AF trigger threshold.