What does an elongated PQ interval signify?

An elongated PQ interval, also known as the PR interval, signifies a delay in the conduction through the atrioventricular (AV) node, which is characteristic of a first-degree heart block. In a normal EKG, the PR interval ranges from 120 to 200 milliseconds. When the interval exceeds 200 milliseconds, it indicates that the electrical signal from the atria to the ventricles is taking longer than normal to propagate through the AV node.

This prolonged conduction time can be caused by various factors such as increased vagal tone, medications, or structural changes to the conduction system. In the case of a first-degree heart block, while all impulses are still conducted to the ventricles, the delay is uniform, resulting in a consistent elongation of the PQ interval.

Recognizing an elongated PQ interval as indicative of first-degree heart block is crucial because it requires monitoring to ensure it does not progress to a more severe block. Understanding this relationship between the PQ interval and conduction delay enhances the interpretation of EKG findings and highlights the importance of considering the implications of conduction abnormalities in clinical practice.