The analysis of P-wave template has been widely used to extract indices of Atrial Fibrillation (AF) risk stratification. The aim of this paper was to assess the potential of the analysis of the P-wave variability over time in patients suffering from atrial fibrillation. P-wave features extracted from P-wave template together with novel indices of P-wave variability have been estimated in a population of patients suffering from persistent AF and compared to those extracted from control subjects. We quantify the P-wave variability over time using three algorithms and we extracted three novel indices: one based on the cross-correlation coefficients among the P-waves (Cross-Correlation Index, CCI), one associated to variation in amplitude of the P-waves (Amplitude Dispersion Index, ADI), one sensible to the phase shift among P-waves (Warping Index, WI). The control group resulted to be characterized by shorter P-wave duration and by a less amount of fragmentation and variability, respect to AF patients. The parameter CCI shows the highest sensitivity (97.3%) and a good specificity (95%).

P wave morphology has been shown to be modified in patients with paroxysmal atrial fibrillation (AF) and in healthy subjects of different age. These changes are commonly evaluated in the signal averaged ECG, thus in average P waves. Aim of this study is to assess beat-tobeat variations in P wave characteristics. Five-minute 12-lead ECG were recorded from 10 healthy subjects (C group), 10/10 patients with/without an AF recurrence (R/NR groups), after electrical cardioversion. Principal component analysis was performed on a beat-to-beat basis. The dynamic of the first three eigenvalues series and the beat-to-beat variability of the first three principal components (PCs) morphology were analyzed by calculating the distance between the average morphology over all the beats acquired and the morphology identified on each beat for the first three PCs. Most of the indexes were statistically different between C group and the patients with history of AF, highlighting higher regularity of the eigenvalues series as well as more similar PCs in healthy subjects. In addition, the series of the first eigenvalues was significantly less regular in R group compared NR group (Reg: 0.029 ± 0.020, 0.062 ± 0.033, p<0.05, R vs NR group).

The aim of this paper was to analyze the P-wave variability over time in patients suffering from Atrial Fibrillation (AF). Behind some time-domain and morphological features of the P-wave template, two novel indexes of P-wave variability have been estimated: one based on the cross-correlation coefficients among the P-waves (Correlation Index, CI), and one associated to variation of P-waves amplitude (Amplitude Index, AI). These indexes were estimated in two experimental models: patients suffering from persistent AF respect to control subjects and patients developing post-operative AF (POAF) after coronary artery bypass grafting respect to patients without POAF. The control group resulted to be characterized by shorter P-wave duration and by a less amount of fragmentation and variability, respect to AF patients (with a sensitivity and specificity of 98.4% and 95 % respectively). Also P-wave features resulted to be different for patients with POAF respect to patients without. In conclusion the quantification of the P-wave variability over time can add information in the understanding of the association between the anatomical atrial substrate and atrial arrhythmias.