Method and apparatus for improving the accuracy of atrial fibrillation detection in lossy data systems

A method of detecting a cardiac atrial fibrillation event in a non-continuous electrocardiogram (EKG) signal carried in a data stream that comprises time-stamped packets, the method comprising:

• a) detecting a portion of the data stream carrying the EKG signal comprising cardiac beats, wherein the portion includes at least one gap;
• b) comparing a time-stamp of each time-stamped packet to an expected time-stamp to measure a duration of the gap in the portion of the EKG signal data stream;
• c) computing a plurality of inter-beat intervals, wherein a computed inter-beat interval of the plurality is selected if the measured gap duration in the portion of the EKG signal data stream is not more than a fraction alpha of the computed inter-beat interval;
• d) computing a variance of the selected inter-beat intervals for a predetermined number of cardiac beats N if no selected inter-beat interval is greater than a predetermined time T;
• e) classifying the portion of the EKG signal data stream as indicative of an atrial fibrillation event if the computed variance of the classified portion of the EKG signal data stream exceeds a pre-determined value V;
• f) discarding the portion of the EKG signal data stream classified as indicative of atrial fibrillation if the classified portion has a duration less than a pre-determined number of cardiac beats M;
• and
• g) annotating the EKG signal data stream, a non-discarded portion of the EKG signal data stream having the computed variance that exceeds the pre-determined value V being annotated as an atrial fibrillation event.

An apparatus that detects a cardiac atrial fibrillation event in a non-continuous electrocardiogram (EKG) signal, the apparatus comprising:

• a) means for detecting a portion of the EKG signal comprising cardiac beats, wherein the portion includes at least one gap;
• b) means for measuring a duration of the gap in the portion of the EKG signal;
• c) means for computing inter-beat intervals that selects a computed interval if the measured gap duration in the portion of the EKG signal is not more than a fraction alpha of the computed inter-beat interval;
• d) means for computing a variance of the selected inter-beat intervals;
• e) means for classifying the portion of the EKG signal as indicative of an atrial fibrillation event if the computed variance of the classified portion of the EKG signal exceeds a pre-determined value V;
• f) means for discarding the portion of the EKG signal classified as indicative of atrial fibrillation if the classified portion has a duration less than a pre-determined threshold S;
• and
• g) means for annotating the EKG signal, a non-discarded portion of the EKG signal having the computed variance that exceeds the pre-determined value V being annotated as an atrial fibrillation event.

An apparatus that detects a cardiac atrial fibrillation event in a non-continuous electrocardiogram (EKG) signal carried in a data stream that comprises time-stamped packets, the apparatus comprising:

• a) means for detecting a portion of an EKG signal comprising cardiac beats, wherein the portion includes at least one gap;
• b) means for comparing a time-stamp of each time-stamped packet to an expected time-stamp to measure a duration of the gap in the portion of the EKG signal;
• c) means for computing inter-beat intervals that selects a computed inter-beat interval if the measured gap duration in the portion of the EKG signal is not more than a fraction alpha of the computed inter-beat interval;
• d) means for computing a variance of the computed inter-beat intervals selected by the means for computing inter-beat intervals, the variance being computed for a pre-predetermined number of cardiac beats N, wherein the means for computing a variance computes the variance if no selected inter-beat interval is greater than a predetermined time T;
• e) means for classifying the portion of the EKG signal as indicative of an atrial fibrillation event if the computed variance of the portion of the EKG signal exceeds a pre-determined value V;
• f) means for discarding the portion of the EKG signal classified as indicative of atrial fibrillation if the classified portion has a duration less than a number of cardiac beats M;
• and
• g) means for annotating the EKG signal, a non-discarded portion of the EKG signal having the computed variance that exceeds V being annotated as an atrial fibrillation event.