How does the P wave characteristically appear on EKG when there is atrial enlargement?

How does the P wave characteristically appear on EKG when there is atrial enlargement?

• A. Broad and tall
• B. Diphasic, having both positive and negative waves
• C. Flat with no deflection
• D. Spiked and narrow

Answer: (B)

The appearance of the P wave on an EKG can provide significant insight into the structural and functional status of the atria. When there is atrial enlargement, particularly of the left atrium, the P wave can exhibit a specific character.

In the context of left atrial enlargement, the P wave may take on a diphasic form, which means it has both positive and negative components. This change occurs because the electrical activity of the enlarged left atrium causes a longer conduction time, leading to an alteration in the normal P wave morphology. The positive part of the diphasic wave reflects the depolarization of the right atrium, followed by a negative component that corresponds to the delayed depolarization of the enlarged left atrium.

In cases of right atrial enlargement, the P wave can also become tall and peaked, but the description as diphasic aligns best with the classical understanding of how atrial enlargement is represented on an EKG.

The presence of this diphasic P wave is a critical finding in EKG interpretation as it indicates changes in atrial size and function, thereby highlighting potential underlying cardiac issues.