Supraventricular Tachycardia (SVT)
What is It?
Supraventricular tachycardia (SVT) is an abnormally fast heartbeat that originates from the top chambers of the heart (atria). Unlike atrial fibrillation, the heart rate in SVT is often steady and regular. SVT affects approximately 2-3 per 1,000 people, and is more common in women. The main types include AV nodal re-entry tachycardia (AVNRT), AV re-entrant tachycardia (including Wolff-Parkinson-White syndrome), and atrial tachycardia. In most cases, episodes of SVT are harmless and may self-terminate, but prolonged episodes warrant medical assessment.
What are the symptoms?
The most common symptom of SVT is palpitations, described as a rapid heartbeat that often starts and stops suddenly. Episodes may be associated with dizziness, breathlessness, chest tightness, neck pounding, or sweating, and in some cases fainting. Even though the heart can beat at very fast rates, SVTs are usually not life-threatening.
What are the causes?
At One Heart Centre our cardiologists screen for all causes of supraventricular tachycardia. Causes and triggers include:
- Congenital extra electrical pathways (such as in Wolff-Parkinson-White syndrome), which have been present since birth.
- Re-entry circuits near the AV node causing a ‘short circuit’ in the heart’s electrical system.
- Lifestyle triggers: High caffeine or alcohol intake, nicotine, stress, anxiety, and lack of sleep.
- Medical factors: Thyroid disease, pregnancy, certain medications (including decongestants and asthma inhalers), and structural heart disease.
How is it investigated?
If you have had a previous episode of SVT, your One Heart Centre cardiologist will perform a 12-lead ECG and echocardiogram to ensure your heart is structurally normal. If the diagnosis is not clear but SVT is suspected, ambulatory ECG monitoring is used to try to capture an episode. Further tests may include exercise stress testing, prolonged ambulatory monitoring, or an electrophysiology (EP) study to map the heart’s electrical system.
What are the treatments?
At One Heart Centre our cardiologists have post-fellowship training in managing supraventricular tachycardia and will provide a personalised treatment plan for your SVT. Treatment options include:
- Vagal manoeuvres: Physical techniques such as the Valsalva manoeuvre or splashing cold water on the face to stop an episode.
- Medical therapy: Daily medications (beta-blockers or calcium channel blockers) to prevent episodes, or single doses to take during an attack.
- Catheter ablation: A minimally invasive procedure that is potentially curative with a 95-99% success rate. At One Heart Centre we have cardiologists who subspecialise in SVT ablation.
- Electrical cardioversion: Used in emergency situations if medications are ineffective.