What does the PR segment represent on an ECG?

The PR segment on an ECG represents the delay at the AV node during atrial depolarization, which is crucial for allowing the ventricles time to fill with blood before they contract. This segment begins at the end of the P wave and extends to the beginning of the QRS complex, encapsulating the time it takes for the electrical impulse to travel through the atria and the AV node into the ventricles.

The concept also includes the overall duration from the beginning of the P wave to the end of the PR segment, encompassing both atrial depolarization and the conduction delay. Therefore, highlighting the significance of this segment enhances understanding of the electrophysiology of the heart, particularly the importance of the AV node's function in managing heart rhythm and ensuring efficient hemodynamic performance.

Recognizing both the time required for ventricular depolarization (which is seen in the QRS complex rather than the PR segment) and distinguishing it from other elements of ECG interpretation reinforces the importance of accuracy in identifying the specific phases of cardiac electrical activity.