Alignment of P waves for signal averaging.

Signal averaged atrial activity recorded from the body surface is finding increased use in assessing atrial arrhythmias. The process of signal averaging is critically dependent upon precise alignment of the waveform of interest. The alignment accuracy of wide (0.01-300 Hz) and narrow (10-300 Hz) bandpass filtered P waves recorded from the body surface were compared to atrial electrograms recorded from temporary pacing wires. The locations of the filtered P waves relative to the atrial electrogram were calculated beat-by-beat for 100 beats in 15 patients aged 1 month to 71 years. The standard deviation of the alignment error for the wide filtered surface P wave averaged 1.7 +/- 0.8 msec and for the narrow filtered P waves was 0.8 +/- 0.4 ms. These results demonstrate that high pass filtering will improve alignment accuracy, and therefore, improve frequency resolution for the analysis of signal averaged P waves.