Cardiac arrhythmia management in the ICU

Also known as Atrial fibrillation · Ventricular tachycardia · Bradycardia and heart block · Cardiac arrhythmia · Supraventricular tachycardia · Atrial flutter · Torsades de Pointes · Complete heart block · Ventricular fibrillation · Antiarrhythmic pharmacology

Arrhythmias are common in ICU (up to 20% of patients). Types: atrial fibrillation (1 — new-onset AF in ICU is associated with worse outcomes), ventricular tachycardia/fibrillation (life-threatening — usually cardiac origin), bradyarrhythmias (heart block, sinus bradycardia), supraventricular tachycardia (AVNRT/AVRT), atrial flutter. Management principles: (1) is the patient haemodynamically unstable? → cardiovert/defibrillate immediately. (2) Identify and treat underlying cause (electrolytes, ischaemia, sepsis, drugs). (3) Rate vs rhythm control. AF: rate control (beta-blocker, diltiazem) usually first; rhythm control (amiodarone, DC cardioversion) if unstable. VT/VF: defibrillate + amiodarone. Bradycardia: atropine → adrenaline/pacing. SVT: vagal manoeuvres → adenosine 6→12→12 mg. Torsades: IV magnesium, stop QT-prolonging drugs, overdrive pacing.

high33 referencesUpdated 17 Aug 202618 min readSource-verified · Sept 2026

Checked against its sources on 2 Sept 2026

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The first decision in any ICU arrhythmia is stability, not the rhythm strip. Unstable (hypotension, shock, ischaemia, heart failure, altered mental status) → electricity now: synchronised cardioversion for an organised tachycardia with a pulse, unsynchronised defibrillation for VF or pulseless VT. Stable → correct K+ and Mg2+ first, then pick rate or rhythm control. AF: rate first (a beta-blocker or diltiazem; a lenient target of under 110 beats/min is as safe as a strict one), rhythm control (amiodarone or DC cardioversion) if unstable, in heart failure, or new-onset within 48 h. Atrial flutter: same rules, and it typically terminates with lower shock energies than AF. SVT: vagal manoeuvres, then adenosine 6 mg IV, then 12 mg if needed. VT with a pulse: if stable, procainamide 10 mg/kg IV over 20 min or amiodarone 5 mg/kg IV over 20 min; cardiovert if unstable; Torsades: magnesium sulphate 2 g IV, stop the QT drugs, speed the heart. Bradycardia: atropine 0.5 mg IV (1.0 mg is the alternative initial dose), then an infusion or pacing.

^[1] ^[5] ^[9] ^[13] ^[23] ^[25]

Meet the patient

A 68-year-old man is admitted to ICU with septic shock from a urinary source — intubated, on noradrenaline 0.3 mcg/kg/min, BP 95/60, lactate 3.2. At 3am the monitor shows a new irregularly irregular rhythm at 150, and the blood gas comes back K+ 3.3, Mg2+ 0.6. He has no cardiac history.^[2] ^[4]

The two questions that will decide his next hour are the two that decide every ICU arrhythmia: is he haemodynamically unstable? (he is not yet — BP held by noradrenaline, no ischaemia, no failure) and what provoked this? (sepsis, catecholamines, and a low potassium — exactly the triad that drives new-onset AF in the ventilated septic patient). Hold those two questions and the rate-versus-rhythm choice answers itself.^[3]

References33Show

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