Supraventricular tachycardia (SVT) is a group of arrhythmias that cause sudden episodes of a rapid heart rate. Despite the unfamiliar name, SVT is common and, in the vast majority of people, benign.
What is SVT?
The term ‘supraventricular’ means the rapid heartbeat originates above the ventricles — in the atria or the tissue connecting the atria to the ventricles. During an episode, the heart rate is typically 150–220 beats per minute.
Symptoms
The hallmark of SVT is sudden-onset palpitation — a rapid, regular fluttering in the chest that stops just as abruptly as it starts. Some people also notice:
- Dizziness or light-headedness
- Shortness of breath
- Chest tightness or discomfort
- A sense of anxiety
Fainting can occur, particularly with AVNRT (see below). SVT does not cause heart attack or stroke, and serious consequences are rare.
Types of SVT
AV node reentrant tachycardia (AVNRT) is the most common type. A short-circuit forms near the AV node — the electrical bridge between the atria and ventricles. AVNRT is the type most likely to cause dizziness or fainting.
Accessory pathway tachycardia occurs when an extra electrical connection between the atria and ventricles is present from birth. If this pathway is visible on a resting ECG, the condition is called Wolff-Parkinson-White syndrome. The extra pathway allows electrical signals to cycle between the two parts of the heart, driving a rapid rate.
Atrial tachycardia arises from an irritable focus within one of the atria that fires repeatedly, driving the heart rate up. It is less common than AVNRT and accessory pathway tachycardia.
Diagnosis
SVT is confirmed on an ECG recorded during an episode. If episodes are infrequent, a prolonged monitor — such as a Holter monitor or wearable patch — may be used to capture one. Many patients now record their SVT on a smart watch or portable single-lead ECG device.
A 12-lead ECG gives the most information and can often identify the specific type of SVT, which guides treatment decisions.
Treatment
SVT does not shorten life expectancy and does not damage the heart. Treatment is aimed at controlling symptoms. There are three main approaches:
No regular treatment — Episodes can often be terminated using a Valsalva manoeuvre: a breath-holding technique that briefly increases pressure in the chest and slows conduction through the AV node. This is reasonable if SVT is infrequent or reliably self-terminating.
Medication — Beta blockers or calcium channel blockers reduce the frequency and rate of SVT episodes. Medication controls rather than cures SVT and must be taken daily.
Catheter ablation — A minimally invasive procedure that permanently eliminates the SVT circuit. Cure rates exceed 90% when the SVT can be induced during the procedure. Most patients are discharged the same day.
For full details of what catheter ablation involves — including the procedure itself, recovery, and risks — see SVT Ablation.