A wide, notched P wave on an ECG indicates what type of atrial enlargement?

A wide, notched P wave on an electrocardiogram (ECG) is indicative of left atrial enlargement. This characteristic shape of the P wave occurs due to the prolonged conduction time through the enlarged left atrium, which results in a delay in atrial depolarization. Specifically, the notch represents the bifid nature of the P wave, reflecting that the left atrial component is taking longer to depolarize due to the increased size and volume of the left atrium.

Unlike right atrial enlargement, which typically causes tall, peaked P waves due to increased right atrial pressure, left atrial enlargement manifests in a different morphology on the ECG. Recognizing these changes is essential for interpreting ECGs accurately and understanding the underlying cardiac conditions.