What does a PR interval greater than 0.20 seconds indicate?

A PR interval greater than 0.20 seconds indicates a first-degree AV block. In this condition, there is a prolonged conduction time through the atrioventricular (AV) node, but every atrial impulse still successfully reaches the ventricles. The hallmark of first-degree AV block on an electrocardiogram (ECG) is the consistent prolongation of the PR interval beyond the normal range of 0.12 to 0.20 seconds, typically measuring over 0.20 seconds.

This type of block is often asymptomatic and can be seen in various situations, such as with increased vagal tone or in athletes. Importantly, there is no dropped beats in first-degree AV block, which differentiates it from the other types of blocks listed. Understanding this distinction is crucial for the appropriate assessment of AV nodal conduction and the implications it has on cardiac function.