Unstable atrial fibrillation with shock — FFICM MCQ

Correct answer: D — Synchronised DC cardioversion

The correct answer is D, synchronised DC cardioversion. This patient has fast atrial fibrillation with life-threatening adverse features (shock with MAP 48 mmHg, pulmonary oedema, and reduced consciousness) of sudden onset, which places him firmly in the unstable, peri-arrest category of the Resuscitation Council UK tachycardia algorithm. In this situation the arrhythmia itself is causing haemodynamic collapse, so the immediate priority is electrical termination of the rhythm rather than pharmacological rate or rhythm control, which act too slowly and carry their own risks of worsening hypotension. Sedation should be given if the patient retains any awareness, but cardioversion must not be delayed for this or for magnesium correction, since instability defines the need for immediate shock regardless of the underlying rhythm label. Why the other options are wrong: A. Start oral bisoprolol: oral beta blockade has a slow onset and negative inotropic effect, offering no immediate benefit and risking further hypotension in a patient already in shock. C. Commence digoxin and review tomorrow: digoxin has a delayed onset of action (hours) and provides no immediate haemodynamic rescue; deferring review is inappropriate in an unstable, deteriorating patient. E. Give intravenous verapamil: verapamil is a negative inotrope and vasodilator that can precipitate cardiovascular collapse in a hypotensive patient, and calcium channel blockers are contraindicated when adverse features are present. B. Observe while correcting magnesium: magnesium correction is useful adjunctive therapy but is not a substitute for definitive treatment of an unstable tachyarrhythmia; observation alone risks cardiac arrest. Key point: presence of adverse features (shock, pulmonary oedema, syncope, or myocardial ischaemia) in a tachyarrhythmia mandates immediate synchronised DC cardioversion ahead of any drug therapy.

Reference: Resuscitation Council UK, Adult Tachycardia Algorithm, Advanced Life Support Guidelines 2021 (updated 2025), https://www.resus.org.uk/library/2021-resuscitation-guidelines/tachycardia-algorithm