Supraventricular tachycardia (SVT) is a group of cardiac arrhythmias characterised by a rapid heart rate originating above the ventricles (in the atria, sinoatrial node, or atrioventricular node). The heart rate in SVT is typically 150 to 250 beats per minute, and the rhythm is usually regular. SVT is the most common group of arrhythmias causing symptoms in adults, particularly in young and otherwise healthy people.
SVT encompasses several distinct arrhythmias. Atrioventricular nodal re-entrant tachycardia (AVNRT, the most common form) is caused by a circular electrical circuit within or around the AV node. Atrioventricular re-entrant tachycardia (AVRT), including Wolff-Parkinson-White syndrome, involves an accessory electrical pathway connecting the atria and ventricles. Atrial flutter is a rapid organised atrial arrhythmia driving the ventricles at a fixed ratio.
Symptoms include sudden onset palpitations, breathlessness, chest tightness, and dizziness. Episodes start and stop abruptly (paroxysmal). Vagal manoeuvres (bearing down or the Valsalva manoeuvre) can terminate AVNRT and AVRT by increasing vagal tone and slowing AV node conduction. If vagal manoeuvres fail, intravenous adenosine is used in hospital to terminate the arrhythmia.
For long-term management, catheter ablation is the definitive treatment for AVNRT and AVRT, with high success rates and low recurrence. SVT itself is rarely life-threatening in structurally normal hearts, but episodes can be distressing and significantly impact quality of life. See also: Paroxysmal SVT.
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