Whilst strictly speaking the term supraventricular tachycardia (SVT) refers to any tachycardia that is not ventricular in origin the term is generally used in the context of paroxysmal SVT. Episodes are characterised by the sudden onset of a narrow complex tachycardia, typically an atrioventricular nodal re-entry tachycardia (AVNRT). Other causes include atrioventricular re-entry tachycardias (AVRT) and junctional tachycardias.

ECG showing AV Nodal Re-entry Tachycardia (AVNRT) - e Image used on license from Dr Smith, University of Minnesota

ECG showing a supraventricular tachycardia - e Image used on license from Dr Smith, University of Minnesota

Management

Acute management

• vagal manoeuvres:
  • Valsalva manoeuvre: e.g. trying to blow into an empty plastic syringe
  • carotid sinus massage
• intravenous adenosine
  • rapid IV bolus of 6mg → if unsuccessful give 12 mg → if unsuccessful give further 18 mg
  • contraindicated in asthmatics - verapamil is a preferable option
• if vagal manoeuvres and adenosine ineffective:
  • verapamil or beta-blocker
  • electrical cardioversion

Prevention of episodes

• beta-blockers
• radio-frequency ablation