What is the normal length of a PR interval?

The normal length of a PR interval is indeed between .12 to .20 seconds. This interval is crucial as it reflects the time taken for electrical impulses to travel from the atria to the ventricles through the AV node. A PR interval within this range indicates that the conduction through the AV node is functioning properly, allowing for coordinated contraction of the atria and ventricles.

When assessing an ECG, a PR interval shorter than .12 seconds may suggest a pre-excitation syndrome or other conduction anomalies, while a length longer than .20 seconds could indicate a first-degree heart block, where there is a delay in conduction through the AV node. Maintaining a PR interval within the normal range is essential for effective cardiac function and rhythm, as irregularities can lead to inadequate ventricular filling or other rhythm disturbances.