P wave

The P wave is the first waveform in the cardiac cycle and represents atrial depolarization

Atrial activity is best seen in the inferior leads (II, III, aVF) and lead V1

P wave duration (time) is normally between 80-110 ms (2-3 small boxes)

Normal P wave amplitude (height, voltage) is < 2.5 mm/mV in limb leads and < 1.5 mm/mV in precordial leads

Normal sinus P wave morphology is upright in limb leads, inverted in aVR, and biphasic in V1

• • P waves may be upright, inverted, biphasic, pokey, fluttering, or fibrillating

Normal P wave axis is between 0° and +75°

The beginning of the P wave reflects right atrial activity and the end reflects left atrial activity