Dynamics of P wave Morphological Variability Preceding the Onset of Atrial Fibrillation

Although the problem of predicting atrial fibrillation (AF) has been extensively studied, the electrophysiological changes that precede AF onset remain insufficiently understood. From a clinical perspective, better understanding of such changes should facilitate future monitoring, prediction strategies, and therapeutic decisions. OBJECTIVE: To investigate the temporal characteristics of P wave morphological variability (PMV) in a 60-min segment preceding the onset of atrial fibrillation (AF). METHODS: Ambulatory ECG recordings from 32 patients comprising 176 AF episodes are analyzed. The P wave is emphasized by a linear, spatial transformation of the ECG. Using a novel, robust parameter, the PMV is computed in successive 2-min subsegments of a 60-min pre-AF segment. A piecewise linear model, accounting for basic PMV characteristics, is fitted to the resulting data points, followed by clustering of the model parameter estimates together with the supraventricular ectopic burden. RESULTS: In 63% of the segments, an increase in PMV was found with a change point ranging from 4 to 17 min before AF onset. Clustering demonstrated heterogeneous characteristics manifested by two clusters associated with an increase in PMV, and two other clusters associated with a low and stable PMV of which one had a much larger ectopic burden. CONCLUSIONS: Clustering suggests that an AF episode may be preceded by focal ectopic activity, conduction destabilization, or without any observed manifestation. SIGNIFICANCE: The proposed framework provides a physiologically interpretable stratification of the pre-AF dynamics of the P wave morphology.