Supraventricular Tachycardia (SVT) in Singapore: Symptoms, Causes and Treatment

Supraventricular tachycardia (SVT) is a heart arrhythmia (abnormal heart rhythm) that causes sudden episodes of a very fast heartbeat, starting in or above the heart’s upper chambers. Episodes typically begin and end abruptly – like a switch being flicked – and often affect younger people with otherwise healthy hearts. SVT can be frightening, but it is rarely life-threatening, and effective treatments exist, including a procedure that targets the cause itself. This page explains what SVT is, its symptoms and triggers, how it is diagnosed, and the treatment options from simple manoeuvres to catheter ablation. It is general information and not a substitute for advice from your own doctor.

What Is Supraventricular Tachycardia?

A normal resting heartbeat runs at around 60 to 100 beats per minute. During an SVT episode, the heart suddenly races – often to 150 beats per minute or more – because an electrical short circuit above the ventricles (the lower pumping chambers) sends signals spinning in a rapid loop. The main forms, in plain words:

• AVNRT (atrioventricular nodal re-entrant tachycardia) – the most common type. A small extra circuit sits within or beside the heart’s electrical junction box (the AV node), allowing signals to chase themselves in a loop. It is seen more often in women.
• AVRT (atrioventricular re-entrant tachycardia) – an extra electrical pathway, present from birth, connects the upper and lower chambers and lets signals loop between them.
• Wolff-Parkinson-White (WPW) syndrome – a form of AVRT in which the extra pathway is visible on a resting heart tracing even between episodes. It is usually very treatable, but needs specialist assessment because the pathway can occasionally conduct dangerously fast rhythms.
• Atrial tachycardia – a small cluster of cells in the upper chambers fires rapidly on its own.

SVT Symptoms

• A sudden racing heartbeat that starts and stops abruptly
• Rapid heart palpitations, sometimes felt as pounding in the neck or throat
• Breathlessness
• Chest tightness or discomfort
• Light-headedness or, occasionally, fainting
• Anxiety or a sense of unease during episodes
• Tiredness, or passing more urine than usual, after an episode ends

Episodes may last seconds, minutes or hours, and can occur anywhere from several times a week to once every few years.

When to Seek Emergency Help

Call 995 if a racing heartbeat occurs together with chest pain, fainting or severe breathlessness, or if an episode will not stop and you feel increasingly unwell. If you have been told you have WPW and develop a very fast or irregular heartbeat, seek emergency care rather than waiting for it to pass.

Causes and Risk Factors

The underlying cause of most SVT is an extra electrical circuit or pathway that has been present since birth – it is not caused by lifestyle, and having SVT does not mean your heart is diseased. Episodes, however, are often set off by triggers:

• Caffeine and energy drinks
• Alcohol
• Stress and anxiety
• Tiredness and lack of sleep
• Fever and acute illness
• Stimulant medications, including some decongestants
• Hormonal changes, including pregnancy

SVT can appear at any age, and symptoms often first appear in the teens or young adulthood.

How SVT Is Diagnosed

The key is capturing the rhythm during an episode:

• An electrocardiogram (ECG) recorded while the heart is racing usually identifies SVT and often its type. Between episodes the ECG is commonly normal, although WPW leaves a telltale pattern even at rest.
• A 24-hour Holter monitor or longer wearable recorder increases the chance of catching an episode; smartwatch and smartphone recordings made during symptoms can also be helpful for your cardiologist to review.
• An event recorder suits infrequent episodes.
• An echocardiogram (ultrasound scan of the heart) and blood tests check for structural or thyroid causes.
• An electrophysiology (EP) study – a specialised keyhole test in which thin wires map the heart’s electrical system from the inside – pinpoints the exact circuit, and is usually performed at the same sitting as ablation treatment.

Treatment Options

Stopping an episode. Many people can end an episode with vagal manoeuvres – simple techniques that stimulate the vagus nerve, which slows the heart’s electrical junction box. Examples include the Valsalva manoeuvre (bearing down as if straining, or blowing hard against resistance such as a syringe), doing this while lying back with the legs raised, or applying an ice-cold wet towel to the face. Your doctor can teach you the technique that suits you. If an episode persists, a fast-acting anti-arrhythmic medication given through a vein at a clinic or emergency department can usually restore normal rhythm.

Preventing episodes. For infrequent, brief episodes, avoiding triggers may be all that is needed. If episodes are more frequent or troublesome, daily medication such as beta-blockers or calcium channel blockers can reduce how often they occur; other anti-arrhythmic medication is used in selected cases.

Catheter ablation. Because SVT is caused by a discrete extra circuit, it can often be treated at its source. In an ablation, performed together with the electrophysiology study, thin flexible tubes are passed to the heart through a vein in the groin, the circuit is located, and heat or freezing energy is applied to interrupt it. As it addresses the underlying cause rather than just suppressing symptoms, ablation is potentially curative for many people with SVT, and may be discussed if episodes are frequent, poorly tolerated, or you would prefer not to take long-term medication. Your cardiologist will explain the benefits and risks as they apply to you.

Living With SVT

Most people with SVT lead completely normal lives. It helps to learn a vagal manoeuvre properly, keep a note of when episodes happen and how long they last, moderate caffeine and alcohol, prioritise sleep, and record your pulse rate during an episode if you can – all of this sharpens the diagnosis and guides treatment.

When to See a Cardiologist

See a cardiologist if you have recurrent episodes of a sudden racing heartbeat, especially if they start and stop abruptly, cause light-headedness, or are becoming more frequent. A clear diagnosis matters because SVT is treatable – and because it needs to be distinguished from other rhythm problems such as atrial fibrillation, which is managed differently.

Frequently Asked Questions

Is SVT dangerous?

For most people, SVT is not life-threatening, although episodes can be very unpleasant. Certain situations – such as WPW, fainting during episodes, or underlying heart disease – need closer specialist attention, which is why a proper diagnosis is important.

What triggers SVT episodes?

Common triggers include caffeine, alcohol, stress, tiredness, illness and stimulant medications. The underlying circuit is usually present from birth, so triggers set off episodes rather than cause the condition itself.

Can SVT go away on its own?

Individual episodes usually stop on their own or with vagal manoeuvres. The tendency to have episodes, however, generally persists because the extra circuit remains – which is why ablation is considered when episodes are frequent.

Is SVT the same as atrial fibrillation?

No. SVT is usually a fast but regular rhythm caused by a discrete extra circuit, while atrial fibrillation is an irregular rhythm with different risks, including stroke. Treatment differs, so telling them apart on a recording matters.

Can SVT be cured?

Catheter ablation targets the extra circuit that causes SVT and is potentially curative for many people. Your cardiologist can advise whether ablation is suitable for your type of SVT and discuss the risks and benefits.