Righ Atrial Enlargement (RAE):
- In lead II: Peaked P wave (A-like appearance)
- Normal P-wave duration
- Increase in the maximal amplitude of the P wave to >0.20 mV in leads II and aVF, and to >0.10 mV in leads V1 and V2
Left Atrial Enlargement (LAE):
- In lead II: gives a notch in the P-wave followed by a second hump (M-like appearance)
- Prolonged P-wave duration(>0.12s) and prollongation of the negative terminal portion of P-wave in lead V1
- Increase only in the amplitude of the terminal negatively directed portion of the P-wave in lead V1 to >0.10 mV
ECGs of patients with atrial enlargement. Arrows, P-wave changes in atrial enlargement; asterisks, left-atrial enlargement.(click image to enlarge)