Following basic ABC assessment, patients are classified as being stable or unstable according to the presence of any adverse signs:

• shock: hypotension (systolic blood pressure < 90 mmHg), pallor, sweating, cold, clammy extremities, confusion or impaired consciousness
• syncope
• myocardial ischaemia
• heart failure

If any of the above adverse signs are present then synchronised DC shocks should be given. Up to 3 shocks can be given; after this expert help should be sought.

Treatment following this is given according to whether the QRS complex is narrow or broad and whether the rhythm is regular or irregular. The full treatment algorithm can be found at the Resuscitation Council website, below is a very limited summary:

Broad-complex tachycardia

Regular

• assume ventricular tachycardia (unless previously confirmed SVT with bundle branch block)
• loading dose of amiodarone followed by 24 hour infusion

Irregular

• seek expert help. Possibilities include:
  • atrial fibrillation with bundle branch block - the most likely cause in a stable patient
  • atrial fibrillation with ventricular pre-excitation
  • torsade de pointes

Narrow-complex tachycardia

Regular

• vagal manoeuvres followed by IV adenosine
• if above unsuccessful consider diagnosis of atrial flutter and control rate (e.g. beta-blockers)

Irregular