A method for identifying a susceptibility of a subject to atrial-rhythm disturbances includes a) placing a plurality of sensors on the subject to measure a physiologic signal of the subject, and b) recording the physiologic signal from the sensor. The physiologic signal includes an atrial electrical activity of the subject. The method includes c) determining a beat-to-beat variability in the atrial electrical activity of the subject. The beat-to-beat variability includes alternans of electrocardiographic waveforms of a predetermined number of a sequence of heart beats. The method includes d) determining a susceptibility to atrial-rhythm disturbances of the subject using the beat-to-beat variability in the atrial electrical activity determined in step c), and e) generating a report of the susceptibility to atrial-rhythm disturbances of the subject.
