When is the PR interval considered normal in sinus rhythm?

The PR interval is a crucial measurement on an electrocardiogram (ECG) that represents the time it takes for electrical impulses to travel from the atria to the ventricles. A normal PR interval indicates that this conduction is occurring effectively and within an expected range.

In sinus rhythm, the normal PR interval is considered to be between 0.12 and 0.20 seconds. This duration reflects a healthy conduction pathway through the atrioventricular (AV) node, ensuring that the contraction of the atria is properly coordinated with the contraction of the ventricles. When the PR interval falls within this range, it suggests that the electrical activity of the heart is functioning properly, without significant delay or blockage.

Intervals shorter than 0.12 seconds may indicate a pre-excitation syndrome where impulses bypass the normal conduction pathway. In contrast, a PR interval longer than 0.20 seconds suggests a delay in conduction, which may indicate conditions like first-degree AV block. Therefore, recognizing a normal PR interval is essential for assessing overall cardiac function and diagnosing potential issues.