7. Atrial Enlargement

Topics for Study:

Right Atrial Enlargement (RAE)

P wave amplitude > 2.5 mm in II and/or > 1.5 mm in V1 (these criteria are not very specific or sensitive)
Better criteria can be derived from the QRS complex; these QRS changes are due to both the high incidence of RVH when RAE is present, and the RV displacement by an enlarged right atrium.
- QR, Qr, qR, or qRs morphology in lead V1 (in absence of coronary heart disease)
- QRS voltage in V1 is < 5 mm and V2/V1 voltage ratio is > 6 (Sensitivity = 50%; Specificity = 90%)

P wave duration ≥ 0.12s in frontal plane (usually lead II)
- Notched P wave in limb leads with the inter-peak duration ≥ 0.04s
- Terminal P negativity in lead V1 (i.e., "P-terminal force") duration ≥ 0.04s, depth ≥ 1 mm.
- Sensitivity = 50%; Specificity = 90%

Features of both RAE and LAE in same ECG
P wave in lead II > 2.5 mm tall and ≥ 0.12s in duration
Initial positive component of P wave in V1 > 1.5 mm tall and prominent P-terminal force