When right atrial enlargement occurs, it does not take longer for cardiac action potentials to travel through the atrial myocardium (similar to left atrial enlargement). However, the amplitude of the P wave is exaggerated due to the close proximity of the hypertrophied right atrial myocardium to the SA node. This is referred to as p-pulmonale since lung disease can cause severe right heart strain and right atrial enlargement. Thus, the P wave height becomes larger. The ECG criteria for diagnosing right atrial enlargement (RAE) are as follows:
The P wave amplitude in lead II > 2.5 mm, or
The upward deflection of the P wave in lead V1 > 1.5 mm in amplitude.
- Surawicz B, et al. Circulation. 2009;119:e235-240.
- Chou's Electrocardiography in Clinical Practice: Adult and Pediatric, Sixth Edition, Saunders, Philadelphia, 2008.