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Wenckebach Block Pre-Assessment — FRCA Final MCQ

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ModeratePreoperative AssessmentWenckebach Block Pre-AssessmentFRCA Final

A 70-year-old man attends preoperative assessment for elective total knee replacement. His heart rate is 45 beats min⁻¹ and blood pressure 130/70 mmHg. He reports no syncope, presyncope or breathlessness, climbs two flights of stairs without symptoms, and his pulse rises above 100 beats min⁻¹ on exertion. His ECG shows narrow-complex Mobitz type I (Wenckebach) second-degree atrioventricular block; an identical pattern is present on ECGs in his records over the past five years. He takes no atrioventricular nodal blocking drugs, and electrolytes and thyroid function are normal with no clinical signs of structural heart disease. What is the most appropriate preoperative management?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Proceed with surgery, with antimuscarinic drugs and external pacing capability available

Explanation lettering: E = shown as A · C = shown as B · D = shown as C · B = shown as D · A = shown as E

A is correct. Progressive PR prolongation before a dropped beat with narrow QRS localises block to the atrioventricular node, where vagal tone predominates and conduction improves with sympathetic drive — shown here by the normal chronotropic response to exertion. The block is long-standing, asymptomatic, and not drug-, electrolyte- or thyroid-related, so it rarely progresses to complete heart block; surgery proceeds with routine vigilance plus antimuscarinics and external pacing immediately available, since anaesthesia can provoke vagally mediated bradycardia. Temporary transvenous pacing (B) carries vascular, tamponade and infection risk and is not indicated prophylactically. Permanent pacing (C) is reserved for symptomatic or intra-/infra-Hisian block, Mobitz II or complete heart block. Exercise testing (D) and ambulatory monitoring with echocardiography (E) are appropriate when block is new, symptomatic, wide-complex or of uncertain level; here the level and chronicity are already established, so deferring elective surgery adds no benefit.

Reference: Glikson M, et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy — recommendations for pacing in atrioventricular block. Eur Heart J 2021;42:3427–3520. https://pubmed.ncbi.nlm.nih.gov/34455427/