The P waves represent atrial depolarization. In a diseased heart, the P wave aberrations in sinus rhythm do not indicate a more serious cardiac condition compared to the aberrations in the QRS complex. However, the P waves can provide some information regarding changes in the hemodynamic state of the diseased heart, especially if the P wave is associated with abnormalities in the QRS complexes.
Left and right atrial enlargement are caused by a chronic overload in the atria that leads to hypertrophy and dilatation. Abnormalities in the P wave are commonly attributed to atrial enlargement. However, other diseases also affect the P wave.
When describing ECG characteristics of patients with left and right atrial enlargement, the terms P mitrale, P pulmonale, and P biatriale are commonly used.