In which type of second-degree atrioventricular block is the block anatomically located below the AV node?

In second-degree atrioventricular block, there are two primary types: Type 1 (Wenckebach) and Type 2. Type 1 generally occurs due to a block at the level of the AV node, characterized by a progressively lengthening PR interval until a beat is dropped. This reflects a more functional or transient block within the AV node itself.

Type 2 second-degree AV block, on the other hand, is typically caused by a more permanent structural issue, often occurring below the AV node in the His-Purkinje system. This type is characterized by a consistent PR interval, followed by the sudden dropping of QRS complexes (conduction failure). Because the block is lower in the conduction system, it tends to be more serious and has a higher risk of progressing to complete heart block compared to Type 1.

This differentiation in anatomical location is crucial for both diagnosis and treatment, as management strategies may vary significantly based on the type and location of the block.