Which resolution for reliable ECG P-wave analysis in atrial fibrillation?

P-wave analysis is becoming more and more used to help indentifying patients at risk for AF. Particularly, precise measurement of P-wave duration is an important factor in determining the risk of atrial arrhythmias. However, the methods to extract P-wave duration must be precise and reliable. Automatic analysis of P-wave must take into account technical aspects, one of those being the bit resolution. The aim of this manuscript is to investigate the effects of amplitude resolution of ECG acquisition systems on P-wave analysis. Starting from ECG recorded by an acquisition system with a LSB of 31 nV (24-bit on an input range of 524mVpp), we reproduced ECG signal as acquired by systems with lower resolution (16, 15, 14, 13 and 12 bit). We found that, when LSB is of the order of 128 μV (12 bit), a single P-wave is not recognizable on ECG (figure 1, upper panel). However, when averaging is applied, a P-wave template can be extracted, apparently suitable for P-wave analysis. Results obtained in terms of P-wave duration revealed that at lowest resolution (from 12 to 14 bit) the error on P-wave duration estimation is important and could lead to misleading results. However, the resolution used nowadays in modern electrocardiographs (15 and 16 bit) lead to results rather similar to those obtained with higher resolution.