Right atrial enlargement can result from increased pressure in the pulmonary artery. A P wave >2.5 mm in leads II, III and aVF or a P wave >1.5 mm in lead V1 indicates right atrial enlargement. Despite the increase in the height of the P wave, the width of the P wave does not change. Sometimes these large P waves can be referred to as Himalayan P waves.

In alphabetical order:

• Atrial aneurysm
• Atrial septal defect
• Cor pulmonale or right heart failure
• Ebstein’s anomaly
• Pulmonic stenosis
• Tricuspid prolapse
• Tricuspid regurgitation
• Tricuspid stenosis
• Tumor

Right atrial enlargement is defined as either:

• A P wave >2.5 mm in leads II, III and aVF
• A P wave >1.5 mm in lead V1

Shown below is an illustration of right atrial enlargement:

Shown below is an EKG demonstrating large P waves in leads to 2,3, and aVF which have a P-wave height greater than 2.5 mm consistent with right each one enlargement:

Shown below is the chest x-ray of a patient with Ebstein’s anomaly in whom the right atrium is markedly enlarged as demonstrated by the convex curvature to the right border the heart.

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