P-wave complexity in normal subjects and computer models

•P waves have complex shapes with 4.1 peaks on average.•The shape of the P wave cannot be recovered by filtering.•P waves have considerable signal content above 40 Hz.

BackgroundP waves reported in electrocardiology literature uniformly appear smooth. Computer simulation and signal analysis studies have shown much more complex shapes.ObjectiveWe systematically investigated P-wave complexity in normal volunteers using high-fidelity electrocardiographic techniques without filtering.MethodsWe recorded 5-min multichannel ECGs in 16 healthy volunteers. Noise and interference were reduced by averaging over 300 beats per recording. In addition, normal P waves were simulated with a realistic model of the human atria.ResultsMeasured P waves had an average of 4.1 peaks (range 1-10) that were reproducible between recordings. Simulated P waves demonstrated similar complexity, which was related to structural discontinuities in the computer model of the atria.ConclusionThe true shape of the P wave is very irregular and is best seen in ECGs averaged over many beats.