A 1st Degree AV Block is characterized by a P-R interval greater than what duration?

A 1st Degree AV Block is characterized by a prolonged P-R interval, which is the duration from the start of the P wave to the start of the QRS complex. This block occurs when there is a delay in the conduction through the atrioventricular (AV) node, but the electrical impulses still reach the ventricles.

A normal P-R interval ranges from 0.12 to 0.20 seconds. When the P-R interval exceeds 0.20 seconds, this indicates that there is a delay, which is consistent with a 1st Degree AV Block. Therefore, recognizing this threshold is crucial in identifying the presence of this type of block.

The other options represent durations that do not accurately define the criteria for a 1st Degree AV Block, as they either fall below the threshold for a normal P-R interval or suggest a more severe conduction delay that correlates with different types of blocks. Specifically, intervals longer than 0.20 seconds indicate a 1st Degree AV Block, while options beyond this duration would pertain to other conduction disturbances or are simply outside normal conduction range.