Atrial Fibrillation (AF) or Flutter – Recent Onset

Requiring admission, or onset during admission for other problem (e.g. post-surgery):

  • Haemodynamic compromise is an indication for rapid DC cardioversion - always use sedation or general anaesthesia (seek anaesthetist support).
  • If the patient is haemodynamically stable (no reduced conscious level, systolic BP >90mmHg, no chest pain and no heart failure) and onset <48 hours, consider chemical cardioversion.
  • For patients with complex congenital heart disease, heart disease in pregnancy, severe mitral stenosis and advanced cardiomyopathy, seek urgent expert cardiology advice.

Figure 1 – Algorithm for Cardioversion of AF

Haemodynamic compromise?

Adverse signs are: pallor, sweating, cold clammy extremities, impaired consciousness, systolic <90mmHg, pulmonary oedema, raised jugular venous pressure
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If Yes – Consider rapid DC cardioversion (see above). After DC cardioversion see ‘Maintenance of sinus rhythm’ section below.

If No – Continue below.
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Start treatment dose dalteparin SC as per VTE guidance unless active bleeding or high risk of bleeding – Consult senior before withholding.
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Consult with senior
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Chemical cardioversion
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IV amiodarone / IV flecainide – for dosing guidance see below.

N.B. These drugs should only be given with continuous ECG monitoring and where appropriate resuscitation facilities are available.
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Chemical cardioversion failed?
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  • Onset <48 hours – Consult with senior at once re urgent DC cardioversion.
  • Onset ≥48 hours – Consult with senior and continue below.
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Arrange echo – excludes mitral stenosis, gives structural and functional assessment of the heart (e.g. whether LV systolic dysfunction / hypertrophy)

N.B. Echo result should not delay initial treatment to slow the ventricular rate and reduce the risk of thromboembolism.

See ADTC290 (link only active via NHS network) for guidance on long-term anticoagulant choice. N.B. Dalteparin should only be used short-term until decision made on long-term anticoagulant choice.
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Aim for rate control (apex <110bpm).

Beta-blocker or rate limiting calcium channel antagonist (the latter only if no evidence of heart failure and no LV systolic dysfunction) are first choice. Digoxin can be added or used as first-line if signs of heart failure. See AF – Persistent guideline for dosing guidance.

N.B. Deal with precipitants of AF: infection, alcohol, hyperthyroidism, heart failure.

Patients with atrial fibrillation who are significantly overweight (BMI > 27kg/m2) should be encouraged to try to lose weight. Studies have shown that overweight and obese patients who manage to lose at least 10% of their body weight are more likely to have successful outcomes from treatment for atrial fibrillation compared to those who fail to lose weight (or who gain weight). 

 

Chemical cardioversion

Options include:

Amiodarone IV 300mg infused over 1 hour then 900mg over 24 hours through a central line (preferable) or large peripheral line or

Flecainide IV 2mg/kg, up to max. 150mg, over 30 minutes if no structural or coronary heart disease.

  • Continuous ECG monitoring required and provision of appropriate resuscitation facilities are mandatory.
  • If chemical cardioversion fails, consult senior medical staff re electrical cardioversion.
  • Remember – many cases of new onset AF or flutter will spontaneously revert to sinus rhythm – particularly if there is an obvious precipitating cause such as pneumonia, alcohol intoxication, hyperthyroidism or surgery.
  • Cardioversion (whether chemical or electrical) is more successful in new onset AF than when AF has been established for any significant length of time, and if being considered should not be delayed. Any patient where cardioversion is being considered requires anticoagulation as soon as possible. If a patient has been in AF for 48 hours without anticoagulation cardioversion becomes much more difficult: they will either require an up-front transoesophageal echo (TOE) or cardiac CT to exclude left atrial appendage thrombus before cardioversion, or instead will have to go onto an extended period (minimum 3 weeks) of uninterrupted anticoagulation before cardioversion can be safely performed.

Maintenance of Sinus Rhythm

Consult Cardiologist for advice. Options include beta-blocker or a variety of dedicated antiarrhythmic drugs (e.g. amiodarone, dronedarone, flecainide, sotalol) depending upon specific cardiac and patient factors.

Amiodarone loading regime is amiodarone oral 200mg three times daily for 1 week then 200mg twice daily for 1 week then 200mg daily.

There is a prescribing protocol available on CMM live (HEPMA prescribing system) entitled ‘Amiodarone Loading Regimen’ to support prescribing of this loading regimen. Other oral regimens (including the ‘Amiodarone High Dose Loading Regimen’) are sometimes used but only on the advice of a cardiologist.

Patients should be advised about potential side effects, skin care precautions (avoid direct exposure to strong UV light, use of high SPF 30 to 50 sun cream) and the need for ongoing monitoring (6 monthly LFTs and thyroid function, regular eye tests), and this should be documented in the case notes.

N.B. Check baseline CXR, LFTs, U&Es and thyroid function tests (ideally before starting or if not then as soon as possible). Note common interactions including antifungals, digoxin, macrolide antibiotics, simvastatin, warfarin (list not exhaustive; see BNF for a full list of drugs and more details).

Paroxysmal AF

In patients with known paroxysmal AF presenting with worsening symptoms. Otherwise, please refer to management of new onset AF as above.

If haemodynamic compromise, manage as above and consider urgent DC cardioversion. 

Ensure no reversible trigger for deterioration in symptoms (for example: electrolytes, alcohol, acute illness e.g. infection, thyroid function).

Review current anti-thrombotic and anti-arrhythmic therapy. It is likely that, assuming no clear reversible trigger for their deterioration, they will require an increase in dose of anti-arrhythmic therapy, assuming a contemporary 12-lead ECG in sinus rhythm does not show significant bradycardia or conduction delay (check PRi, QRS duration and QTc interval).  If antiarrhythmic therapy is increased ensure a repeat 12-lead ECG after 1-2 weeks on the higher dose is arranged.

Assuming the patient is otherwise fit and well (see section on 'Patients to refer for specialist assessment / consideration of cardioversion or ablation' within the Atrial Fibrillation (AF) - Persistent guideline) please discuss with cardiology regarding longer-term follow up and more definitive management.

 

Guideline reviewed April 2025
Page updated August 2025



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