Which characteristic is specific to a second-degree type 2 AV block on an EKG?

In a second-degree type 2 AV block, the key characteristic seen on an EKG is that the P-R intervals remain constant for each conducted beat, but some P waves are not followed by QRS complexes. This means that while the electrical impulse from the atria initiates a P wave at a regular interval, the atrioventricular (AV) node fails to conduct some of these impulses to the ventricles, leading to dropped QRS complexes. This pattern of consistent P-R intervals, with intermittent failure to transmit the impulse, distinguishes second-degree type 2 from other types of AV block, such as type 1 (Wenckebach), where the P-R intervals progressively lengthen before a drop occurs.

This consistency in the P-R interval is critical for identifying the block type; it indicates that there is a specific failure point in the conduction system that leads to missed beats, rather than a gradual change in conduction time. Understanding this pattern aids clinicians in diagnosing the nature and severity of the heart's conduction issues, enabling appropriate management strategies.