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Haemodynamically unstable Lyme carditis — MSRA MCQ

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HardInfectious DiseasesHaemodynamically unstable Lyme carditisMSRA

A 47-year-old man presents to his GP with 6 days of episodic palpitations, dizziness and two near-syncopal episodes. Five weeks ago, after hillwalking in the Scottish Highlands, he developed an expanding, non-pruritic annular erythematous rash, approximately 11 cm in diameter, on his thigh. It resolved spontaneously after 10 days. He does not recall a tick bite. He is afebrile. His pulse is 34 beats/minute and regular, BP 88/52 mmHg, and oxygen saturation 98% on air. An ECG shows complete heart block. He has no previous cardiac disease and takes no regular medication. What is the most appropriate management today?

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Correct answer: A — Arrange emergency ambulance transfer for cardiac monitoring and specialist-led intravenous ceftriaxone treatment

This is haemodynamically unstable Lyme carditis. The preceding expanding annular rash after likely tick exposure is clinically consistent with erythema migrans; absence of a recalled tick bite does not exclude Lyme disease. New complete heart block, marked bradycardia, hypotension and presyncope indicate a cardiac complication requiring emergency referral rather than community management. NICE advises emergency referral for cardiac complications such as complete heart block even when Lyme disease is suspected. For Lyme carditis with haemodynamic instability, intravenous ceftriaxone is recommended; cardiac monitoring is essential because high-grade atrioventricular block may deteriorate and require urgent specialist intervention. A and D use oral doxycycline, which is recommended for haemodynamically stable Lyme carditis but is inadequate for this unstable presentation. B appropriately recognises possible Lyme disease and seeks same-day assessment, but oral amoxicillin and a non-emergency route fail to address complete heart block with hypotension. E inappropriately delays both emergency management and antimicrobial treatment while awaiting serology; testing must not postpone transfer in suspected cardiac Lyme disease.

Reference: NICE NG95: Lyme disease, Recommendations (2018; checked 15 August 2026) — https://www.nice.org.uk/guidance/ng95/chapter/Recommendations NICE NG95: Lyme disease, Recommendations (2018; checked 15 August 2026) — https://www.nice.org.uk/guidance/ng95/chapter/Recommendations