What characterizes a Wenckebach AV block?

What characterizes a Wenckebach AV block?

• A. Consistent AV conduction without interruption
• B. Progressive blocking of AV node conduction
• C. Permanent complete block of atrial stimuli
• D. Normal PR intervals with occasional drops

Answer: (B)

A Wenckebach AV block, also known as Mobitz type I block, is characterized by progressive blocking of atrioventricular (AV) node conduction. In this condition, there is a gradual lengthening of the PR interval on the electrocardiogram, until one of the atrial impulses is completely blocked and does not result in a QRS complex. This pattern indicates a malfunction in the AV node where the electrical signals from the atria are not consistently transmitted to the ventricles.

This progressive nature differentiates Wenckebach from other types of AV block. For instance, a consistent AV conduction without interruption reflects normal conduction, while a permanent complete block of atrial stimuli represents a different advanced stage of heart block (such as a third-degree AV block). Normal PR intervals would indicate typical electrical conduction without interruptions, which does not apply to Wenckebach. Therefore, the defining characteristic of this block is indeed the progressive nature of conduction failure within the AV node.