Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
Atrial fibrillation
Cardiology · UK scope · Sources checked 25 Aug 2026 · Clinical review pending
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Escalate
If AF is causing shock, syncope with severe or ongoing hypotension, myocardial ischaemia, pulmonary oedema/severe heart failure, or occurs immediately after ROSC, call for senior/resuscitation help and perform synchronised cardioversion; do not delay a life-saving shock to establish anticoagulation.
Synopsis
Recognise atrial fibrillation, separate unstable from stable presentations, and make safe rate, rhythm and stroke-prevention decisions in a UK pathway.
Suspect AF with an irregular pulse in a patient with palpitations, breathlessness, dizziness/syncope, chest discomfort, stroke or TIA; confirm with a 12-lead ECG.
Typical ECG: no consistent sinus P waves and an irregularly irregular ventricular response; AF may be slow, controlled or rapid.
If a 12-lead ECG misses suspected paroxysmal AF, NICE uses a 24-hour monitor when episodes are asymptomatic or less than 24 hours apart, and longer event/ECG monitoring when symptoms are more than 24 hours apart.
Treat the patient, not the rate: haemodynamic instability caused by AF requires immediate synchronised cardioversion.
For stable acute AF, NICE allows rate or rhythm control when onset is under 48 hours, but favours rate control when onset is over 48 hours or uncertain.
Use CHA2DS2-VASc for stroke risk and ORBIT for bleeding risk; a high bleeding score should prompt modification and closer review, not automatic denial of anticoagulation.
NICE offers a DOAC at CHA2DS2-VASc 2 or more and says to consider one for a man scoring 1; do not use aspirin alone for AF stroke prevention.
Long-term rate control is usually a standard beta-blocker or rate-limiting calcium-channel blocker; digoxin is conditional, especially for non-paroxysmal AF in a sedentary person or when other options are unsuitable.
Never stop anticoagulation solely because sinus rhythm has returned or AF is no longer detected; reassess stroke and bleeding risks and the person's preferences.
Key red flags
Life-threatening instability
Shock (often SBP below 90 mmHg with hypoperfusion), syncope with severe or ongoing hypotension, myocardial ischaemia, severe heart failure with pulmonary oedema, or immediately post-ROSC.
Pre-excited AF
Very rapid, irregular broad-complex tachycardia with varying QRS morphology in a patient with an accessory pathway. It can deteriorate to VF: avoid AV-nodal blockers such as adenosine, verapamil/diltiazem, beta-blockers and digoxin; seek expert help for procainamide or cardioversion.
Associated emergency
Look for ACS, stroke/TIA, acute heart failure, sepsis, thyrotoxicosis, pulmonary embolism, hypoxia, electrolyte disturbance, bleeding or drug toxicity; AF may be a marker rather than the primary problem.
Investigation priorities
01
ABCDE assessment, observations, continuous ECG/BP/SpO2 monitoring and 12-lead ECGFirst step
Confirm AF, document rate/QRS/QT and identify instability, ischaemia, pre-excitation or another rhythm.
Management branches
ImmediateAF causing life-threatening instability
Shock, syncope with severe/ongoing hypotension, myocardial ischaemia, pulmonary oedema/severe heart failure, or immediately post-ROSC.
Call for expert/resuscitation help, perform ABCDE, attach monitor/defibrillator pads, obtain IV access and treat reversible causes.
Use synchronised cardioversion. RCUK considers an initial shock at the defibrillator's maximum output reasonable for AF; make up to three synchronised attempts with escalation/local device settings.
Provide careful sedation or anaesthesia if conscious and feasible, but do not let it create a dangerous delay.
If shocks fail and instability persists, RCUK permits amiodarone 300 mg IV over 10-20 minutes OR procainamide 10-15 mg/kg IV (maximum 1 g) over 20 minutes according to availability/contraindications, then repeat synchronised cardioversion.
Do not delay emergency cardioversion to anticoagulate. Start anticoagulation as soon as safe and complete stroke/bleeding assessment.
Acute stableChoose rate or rhythm control by duration and context
Confirmed AF without life-threatening instability.
Key medicines
Atenolol IV/PO (licensed SmPC example of beta-blockade; not a mandatory NICE preference)Acute arrhythmia: 2.5 mg IV over 2.5 minutes; repeat at 5-minute intervals to response, maximum 10 mg. Alternative infusion: 0.15 mg/kg over 20 minutes. After control, 50-100 mg PO once daily is the cited maintenance regimen.Avoid or reduce in bradycardia, hypotension, high-grade block, acute decompensated heart failure and severe bronchospasm; adjust for renal impairment. Do not combine IV beta-blockade with IV verapamil.
Verapamil IV5-10 mg by slow IV injection over at least 2 minutes with continuous ECG/BP observation; if necessary, a further 5 mg after 5-10 minutes.Do not use in hypotension, HFrEF/pulmonary oedema, high-grade AV block without pacing, broad-complex tachycardia, or pre-excited AF. IV verapamil with beta-blockers can cause profound hypotension or AV block.
Sources and review status15 sources · checked 25 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 25 Aug 2026; clinical approval remains outstanding.
Treat triggers and confirm onset. NICE: if onset is under 48 hours, offer either rate or rhythm control; if over 48 hours or uncertain, offer rate control and do not perform routine immediate cardioversion.
Select a rate-control class conditionally. With EF above 40%, RCUK lists a beta-blocker, verapamil, diltiazem or digoxin. With EF below 40%, it suggests a beta-blocker or digoxin and a resting target below 110/min; seek senior input in acute decompensated heart failure and do not use verapamil/diltiazem.
If pharmacological cardioversion is chosen, NICE offers flecainide or amiodarone when there is no structural/ischaemic heart disease, and amiodarone when structural disease is present. This is a specialist choice, not a universal sequence.
NICE says offer heparin at presentation in new-onset AF when anticoagulation is absent/subtherapeutic and no contraindication exists, continuing until full assessment and appropriate antithrombotic therapy; it does not specify one fixed dose, so use the local weight/renal protocol.
Threshold nuance: the March 2026 RCUK peri-arrest algorithm says anticoagulate when AF duration exceeds 24 hours, whereas NICE NG196 uses 48 hours for its acute rhythm-control branch. Treat this as a governance/senior decision, not permission to cardiovert between 24 and 48 hours without considering embolic risk.
Elective cardioversionProlonged or uncertain-duration AF
Rhythm control is appropriate but AF has lasted more than 48 hours or duration is uncertain.
NICE: maintain therapeutic anticoagulation for at least three weeks before cardioversion while controlling rate, or consider an experienced-service TOE-guided strategy when a shorter pre-cardioversion interval is appropriate.
For AF persisting over 48 hours, NICE prefers electrical rather than pharmacological cardioversion.
Non-NICE ESC typical: continue therapeutic anticoagulation for at least four weeks after cardioversion, then continue long term according to thromboembolic risk rather than apparent sinus rhythm alone.
Document adherence, renal function and dose appropriateness before calling a patient therapeutically anticoagulated.
Long termSymptoms, stroke prevention and specialist rhythm control
After acute stabilisation or for incidentally detected/chronic AF.
Offer rate control first in most people, except when AF has a reversible cause, is new-onset, is causing heart failure, atrial flutter is suitable for ablation, or clinical judgement favours rhythm control.
Use a standard beta-blocker or diltiazem/verapamil monotherapy according to symptoms, rate, comorbidity and preference. Consider digoxin monotherapy only for non-paroxysmal AF in a sedentary person or when other options are unsuitable.
If monotherapy fails and symptoms are due to poor rate control, NICE permits two of beta-blocker, diltiazem and digoxin; it does not recommend combining beta-blocker with verapamil.
Consider rhythm control when symptoms persist despite adequate rate control or rate control fails. Refer promptly, within four weeks of failed treatment or recurrence after cardioversion, when specialist management is needed.
Consider catheter ablation after discussion when antiarrhythmic treatment fails or is not tolerated; continue anticoagulation decisions according to CHA2DS2-VASc/ORBIT.