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Mobitz Type I AV Block — EECC MCQ

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EasyArrhythmia & ElectrophysiologyMobitz Type I AV BlockEECC

A 60-year-old man presents with syncope. ECG shows sinus rhythm with grouped beating: progressive PR prolongation followed by a dropped QRS, then the cycle repeats. What is the diagnosis and does it require pacing?

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Correct answer: B — Second-degree AV block Mobitz type I (Wenckebach) — pacing is generally not required unless symptomatic with documented correlation

Mobitz type I (Wenckebach) AV block is characterised by progressive PR prolongation with eventual non-conduction (dropped QRS), producing grouped beating. The block is usually at the AV node level (supra-Hisian) and is often benign, particularly in younger patients and athletes. The ESC Pacing Guidelines (2021) state that permanent pacing is generally not indicated for Mobitz I unless: (1) symptoms are clearly attributable to the bradycardia, (2) the block is infranodal (rare for Mobitz I), or (3) it occurs in the context of neuromuscular disease. In contrast, Mobitz type II (constant PR interval with sudden dropped QRS) is infranodal and carries a higher risk of progression to complete heart block, warranting pacing.

Reference: ESC (2021): Guidelines on Cardiac Pacing and CRT