A P-R interval longer than 0.2 seconds on ECG indicates what condition?

The P-R interval, which is the time between the onset of atrial depolarization and the onset of ventricular depolarization, is an important measure in interpreting an ECG. A P-R interval longer than 0.2 seconds indicates a delay in the electrical conduction through the atrioventricular (AV) node.

In this context, a prolonged P-R interval is characteristic of first-degree AV block. This condition signifies that all atrial impulses are conducted to the ventricles, but there is a prolonged conduction time through the AV node. The identifying feature in first-degree AV block is this persistent prolongation of the P-R interval without any dropped beats or inconsistencies in the pattern.

Understanding that a normal P-R interval ranges from 0.12 to 0.20 seconds helps clarify the implications of any interval longer than that threshold. In this case, since the interval exceeds 0.2 seconds, it supports the diagnosis of first-degree AV block, as the distinction relies on the length of the conduction delay without the complete failure of impulses through the AV node, which would categorize it differently.

Thus, a P-R interval over 0.2 seconds indicates a first-degree AV block, confirming the selected answer.