Complete Heart Block (Third-Degree AV Block)

Pacing is the answer - An unpaced complete block is unstable; ensure transcutaneous pacing is available and, for elective cases, a temporary or permanent pacemaker as indicated before proceeding.

Rate support - The escape rhythm is slow and unreliable; atropine often fails on a ventricular escape, so have isoproterenol or epinephrine and pacing ready.

Avoid further AV depression - Avoid drugs and maneuvers that worsen conduction or provoke vagal tone where possible.

Continuous monitoring - Watch for escape-rhythm failure, asystole, or ventricular arrhythmia and be ready to pace or resuscitate immediately.

Existing pacemaker - If one is in place, know its settings and the plan for surgery (magnet response, electrocautery interference).

Complete (third-degree) atrioventricular block is total failure of conduction between the atria and ventricles; they beat independently, and the ventricular rate is set by a slow, unreliable escape pacemaker.

The result is bradycardia with loss of AV synchrony, reduced cardiac output, and a risk of asystole or ventricular arrhythmia. It's an unstable rhythm that usually needs pacing, and anesthetic drugs and vagal stimuli can further depress an already marginal escape rhythm.