Complete AV Block in AF — EECC MCQ
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Correct answer: D — Complete (third-degree) AV block with junctional escape rhythm — the regular ventricular rate despite AF indicates complete dissociation between atrial and ventricular activity, with a junctional or ventricular escape pacemaker
In AF, the baseline ventricular rhythm is characteristically irregularly irregular. A regular ventricular rate during AF indicates complete AV block — the ventricles are no longer controlled by conducted atrial impulses (which would be irregular) but instead by an escape pacemaker (junctional: narrow QRS, 40-60 bpm; ventricular: wide QRS, 20-40 bpm). Common causes include: digoxin toxicity (classic presentation), degenerative conduction disease, infiltrative disease (amyloidosis, sarcoidosis), and post-ablation (inadvertent AV node injury). The 2021 ESC Pacing Guidelines recommend permanent pacemaker for symptomatic complete AV block (Class I). In digoxin toxicity, stopping digoxin and administering digoxin-specific antibodies (Fab fragments) may restore AV conduction.
Reference: ESC (2021): Pacing Guidelines