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Topics for study:

1. Right Atrial Enlargement (RAE)
2. Left Atrial Enlargement (LAE)
3. Bi-Atrial Enlargement (BAE)

 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%)

  click here to view

In the above ECG, note the tall P waves in Lead II, and the Qr wave in Lead V1.

2. Left Atrial Enlargement (LAE)

 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%

  click here to view

 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