Mobitz I (Wenckebach) block is characterized by

Mobitz I (Wenckebach) block is characterized by

• A. The PR interval progressively lengthens until a beat is dropped; usually benign; no treatment
• B. The PR interval remains constant with dropped beats
• C. The rhythm always requires pacemaker
• D. Definitive pacing is immediately required

Answer: (A)

Mobitz I (Wenckebach) block is a pattern of AV nodal conduction where the signal through the AV node slows with each beat, so the PR interval lengthens progressively until a P wave is not followed by a QRS complex. This dropped beat is the hallmark of the block and points to a nodal-level problem rather than a conduction issue below the AV node. Because the block is usually at the AV node and often benign, most people don’t need pacing or intervention—addressing any reversible factors, like stopping an offending drug or treating underlying conditions, is the main approach. If symptoms or significant bradycardia occur, temporary measures such as addressing the cause or using temporary pacing or atropine may be considered, but permanent pacing is not routinely required for Wenckebach. This pattern is distinct from Mobitz II, where the PR interval stays constant with dropped beats, and from higher-degree blocks that typically require pacing.

Mobitz I (Wenckebach) block is a pattern of AV nodal conduction where the signal through the AV node slows with each beat, so the PR interval lengthens progressively until a P wave is not followed by a QRS complex. This dropped beat is the hallmark of the block and points to a nodal-level problem rather than a conduction issue below the AV node. Because the block is usually at the AV node and often benign, most people don’t need pacing or intervention—addressing any reversible factors, like stopping an offending drug or treating underlying conditions, is the main approach. If symptoms or significant bradycardia occur, temporary measures such as addressing the cause or using temporary pacing or atropine may be considered, but permanent pacing is not routinely required for Wenckebach. This pattern is distinct from Mobitz II, where the PR interval stays constant with dropped beats, and from higher-degree blocks that typically require pacing.