Although most patients with atrial fibrillation present without haemodynamic compromise, there is a small group of patients who are considerably compromised by the onset of atrial fibrillation. These patients require immediate hospitalisation and urgent intervention to prevent further deterioration.

The rate versus rhythm debate and the efficacy and safety of anticoagulation are just two examples of key management decisions the clinician and patient must face. This situation is compounded in the haemodynamically unstable patient, both by the need to act speedily and by the lack of research in this area. Although there is general agreement that such patients should be immediately hospitalised, supportive treatment (eg, oxygen) provided, and treatment of any precipitants (eg, fever and myocardial infarction) started, the decision regarding what specific atrial fibrillation treatment should be embarked on is more controversial.

Consensus statements by the Resuscitation Council (UK)¹ and the American College of Cardiology/American Heart Association Task Force/European Society of Cardiology² have given guidance on those patients considered at highest risk of haemodynamic instability—that is, those with atrial fibrillation with a ventricular rate >150 bpm, ongoing chest pain or critical perfusion. Patients with lower rates and certainly rates <120 bpm are more probably compromised by co-morbidities, such as myocardial ischaemia, pneumonia or chronic obstructive pulmonary disease exacerbation, and treatment should be aimed at resolving these. In the setting of haemodynamic instability, concerns about intervention in the absence of anticoagulation and echocardiography are counterbalanced by the need for urgent treatment. This may include the need to treat important problems such as hypoxia, left ventricular failure, acute ischaemia, pyrexia and electrolyte disorders.

There are several specific precipitants and comorbidities that mandate specific treatments. These include primary cardiac electrophysiological abnormalities, such as Wolf–Parkinson–White syndrome, in which patients may develop ventricular rates >200 bpm with the potential for acute ventricular …