Time‐Domain and Morphological Analysis of the P‐Wave. Part I: Technical Aspects for Automatic Quantification of P‐Wave Features

Abstract

We found that alignment is necessary for a reliable extraction of P-wave template by the averaging procedure, in order to perform time-domain and morphological analysis. On simulated and real data, the error on P-wave duration can be as high as 30 ms on a template obtained without alignment; if alignment procedure is performed, the error on P-wave duration is negligible. Analogously, morphological features are correctly estimated only on a P-wave template obtained with P-waves alignment. We also found that the proposed algorithm for the automatic estimation of the P-wave duration gave reliable results.

Spatial Pattern of P Waves in Paroxysmal Atrial Fibrillation Patients in Sinus Rhythm and Controls

“…Finally, considering the maximum dipole amplitude across the whole depolarization cycle and its timing, there were no significant differences between groups in the maximum amplitudes of the positive or negative poles with values of 93 (37) μV (PAF), 81 (20) μV (HC) and -69 (23) μV (PAF), -68 (15) μV (HC), respectively. Compared to controls, the PAF group positive poles reached peak amplitude sooner (49 [11] ms vs 65 [14] ms, P = 0.012) and negative poles reached peak amplitude later (74 [13] ms vs 62 [8] ms, P = 0.019).…”

“…Beats with similar RR interval were used to minimize the effects of morphology changes associated with changes in heart rate, and therefore only beats with RR intervals within 1% of the most common (mode) RR interval across the recording were included in the average beat calculation. This method of P averaging avoids the necessity of time-alignment of individual P waves, based, for example, on template matching, 14 when beats having different RR intervals are used. As illustrated in Figure 2, the average P waves retain detailed morphological features such as notching while minimizing the recording noise.…”

Wavelet Entropy Automatically Detects Episodes of Atrial Fibrillation from Single-Lead Electrocardiograms

“…However, the classification rate directly increased as a function of L up to a value of about 97% for L = 20 beats. A reasonable explanation for this trend is due to the improvement in the signal-to-noise ratio of a P-wave as the number of considered TQ intervals in SR increases; thus, a clearer P-wave can be obtained [55]. Conversely, when TQ intervals only related to AF are considered to obtain their median, f -waves tend to be attenuated because, as previously mentioned, they present random morphological variations [22].…”

The P Wave Time‐Frequency Variability Reflects Atrial Conduction Defects before Paroxysmal Atrial Fibrillation

“…Given the relatively low amplitude of the P wave in the ECG with respect to the background noise, this noise had to be removed before estimating the P wave variability. For that purpose, data series obtained from the single wave‐to‐wave analysis associated with each feature were divided into segments of 10 samples.…”