| Overall key points |
Supraventricular tachycardia (SVT) is rarely life-threatening, but can cause troublesome symptoms.
It occurs more frequently in women than men; most commonly in 30-50 year olds.
Atrio-ventricular nodal re-entrant tachycardia (AVNRT) and atrio-ventricular re-entrant tachycardia (AVRT) are the most common forms of SVT.
Appropriate ECG documentation should be sought to aid diagnosis of SVT.
Part 1: Aetiology and epidemiology
Supraventricular tachycardia (SVT) describes a regular narrow complex tachycardia (NCT) (usually > 100bpm) with a QRS duration of 120ms or less.¹ SVT is a relatively common arrhythmia affecting approximately 2-3 per cent of the population; it is usually paroxysmal and rarely life-threatening but can impact on quality of life due to troublesome symptoms.²
SVT is commonly used to describe any arrhythmia originating above the ventricles, but arrhythmia specialists will describe the most common mechanisms as atrio-ventricular nodal re-entrant tachycardia (AVNRT) and atrio-ventricular re-entrant tachycardia (AVRT).The mechanism responsible for both AVNRT and AVRT is re-entry.