Abstract
Background: Although prolonged duration of the signal-averaged (SA) P wave has been proposed as a noninvasive marker of atrial arrhythmias, clinical value of atrial SAECG is limited, largely due to the difficulty with detection of the onset and offset of the high gain P wave. The aim of this study was to assess the reliability of automatic measurement of the atrial SAECG. Methods: Fifty-one healthy volunteers (30 men; 32 ± 8 years) underwent a session of 3 atrial and 3 ventricular SAECG recordings. Automatically detected onset and offset of SA QRS complex (QRStot) and SA P wave (Ptot) were subsequently-corrected by two independent observers. For ventricular SAECG, three conventional time-domain parameters were calculated. For atrial SAECG, the following five parameters were measured: Ptot, root mean square voltages of the entire Ptot (RMS-P) and of the terminal 40, 30, and 20 ms of Ptot. Relative errors of the different pairs of measurements were used to assess the interobserver and observer-computer variability. The Bland-Altman method was applied to express the agreement between measurements. Results: Although the mean interobserver relative errors were low for QRStot and Ptot (1.1% vs 1.5%), the observer-computer error was significantly higher for Ptot than for QRStot (1.7% vs 7.1%; P < 0.0001). For the voltage parameters, the lowest interobserver and observer-computer relative errors were found for RMS-P (6.6% vs 7.3%, P = ns). For RMS voltages of the terminal 40–20 ms of Ptot, relative errors exceeded 10%, but the interobserver error was significantly lower than the observer-computer error (P < 0.0001). Conclusion: Automatic detection of the SA P-wave onset and offset is unreliable and the atrial SAECG requires manual correction. Given a good interobserver agreement, such a correction is unlikely to introduce any significant observer-dependent bias. A.N.E. 2000; 5(2):133–138
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