Peri-arrest Arrhythmias

General advice

Assessment and treatment of all arrhythmias should address two factors: the condition of the patient (stable versus unstable) and the nature of the arrhythmia.

Adverse signs

The presence or absence of adverse signs or symptoms will dictate the appropriate treatment for most arrhythmias. The following adverse factors indicate that a patient is unstable because of the arrhythmia:

Clinical evidence of low cardiac output - pallor, sweating, cold, clammy extremities (increased sympathetic activity), impaired consciousness or syncope (reduced cerebral blood flow), and hypotension (e.g. systolic blood pressure <90mmHg).

Excessive tachycardia - very high heart rates (e.g. >150 beats/minute) reduce coronary blood flow and can cause myocardial ischaemia. Broad-complex tachycardias are tolerated by the heart less well than narrow-complex tachycardias.

Excessive bradycardia - this is defined as a heart rate of <40 beats/minute, but rates of <60 beats/minute may not be tolerated by patients with poor cardiac reserve.

Heart failure - pulmonary oedema indicates failure of the left ventricle, and raised jugular venous pressure and hepatic engorgement indicate failure of the right ventricle.

Chest pain - the presence of chest pain implies that the arrhythmia, particularly a tachyarrhythmia, is causing myocardial ischaemia.

Treatment options

Having determined the rhythm and presence or absence of adverse signs, there are broadly three options for immediate treatment:

  • Anti-arrhythmic (and other) drugs
  • Attempted electrical cardioversion
  • Cardiac pacing

Anti-arrhythmic drugs act more slowly and less reliably than electrical cardioversion in converting a tachycardia to sinus rhythm. Thus, drugs tend to be reserved for stable patients without adverse signs, and electrical cardioversion is usually the preferred treatment for the unstable patient displaying adverse signs.

Once an arrhythmia has been treated successfully, repeat the 12-lead ECG to enable detection of any underlying abnormalities that may require long-term therapy.

Tachycardia - treatment algorithm

Reproduced with the kind permission of the Resuscitation Council (UK)

Bradycardia - treatment algorithm

Reproduced with the kind permission of the Resuscitation Council (UK)


Guideline reviewed: May 2023

Page last updated: June 2023