Performance comparison of parameters characterizing P wave variability before the onset of atrial fibrillation.

Short-term characterization of P waves occurring before the onset of atrial fibrillation (AF) is essential to better understand triggering mechanisms. The characterization is challenged by a low signal-to-noise ratio which makes P wave delineation difficult. This study compares the performance of a parameter characterizing P wave morphological variability (MV) to that of four previously published P wave variability parameters: amplitude dispersion, duration, arc length, and power ratio of principal components. The comparison is based on the St.Petersburg Atrial Fibrillation Database comprising 176 one-hour sinus rhythm segments just before AF onset, obtained from 32 patients. Following a linear, spatial transformation that emphasizes the P wave, the MV parameter is computed in consecutive, overlapping subsegments and normalized by a reference value taken one hour before AF onset. The results show that the MV parameter exhibits the highest reactivity to AF onset, with a mean relative increase of 19% 10 min before AF onset, whereas the other four parameters had lower reactivities (amplitude dispersion: 10%, duration: 0%, arc length: 10%, and power ratio: 2%). The conclusion is that the MV parameter better reflects the short-term instability of the atrial substrate than the other parameters.