Supraventricular Tachycardia (SVT): ECG & Treatment

Supraventricular tachycardia is a fast, narrow-complex rhythm that starts at or above the AV node. It's usually not life-threatening and often stops with simple bedside measures.

What is SVT?

Supraventricular tachycardia (SVT) is a fast heart rhythm — typically 150–250 bpm — that originates at or above the AV node, producing a regular, narrow-complex tachycardia. Because the impulse still uses the normal conduction system, the QRS is narrow, which distinguishes it from ventricular tachycardia.

SVT on the ECG

• Narrow QRS (< 0.12 s)
• Regular and fast (often 150–250 bpm)
• P waves are often hidden in the preceding T wave

Common types

Type	Mechanism
AVNRT	Reentry within the AV node — the most common
AVRT	Reentry using an accessory pathway (e.g. WPW)
Atrial tachycardia	A single fast atrial focus

Treatment

For a stable patient, treatment escalates gently:

1. Vagal maneuvers — Valsalva or carotid sinus massage to slow AV conduction.
2. Adenosine — briefly blocks the AV node to break the reentry.
3. AV-nodal blockers — beta-blockers or calcium channel blockers for control.

An unstable patient needs synchronised cardioversion. Recurrent SVT is often cured with catheter ablation.

Key takeaways

• SVT is a regular, narrow-complex tachycardia from at or above the AV node.
• AVNRT is the most common type.
• Stable SVT: vagal maneuvers, then adenosine.
• Unstable SVT: synchronised cardioversion.
• Ablation can cure recurrent SVT.

Frequently asked questions

What is supraventricular tachycardia?

A fast, regular, narrow-complex heart rhythm (often 150–250 bpm) that originates at or above the AV node.

How is SVT different from VT?

SVT is narrow-complex (using the normal conduction system) while ventricular tachycardia is wide-complex; a wide regular tachycardia is treated as VT until proven otherwise.

What is the first treatment for stable SVT?

Vagal maneuvers such as the Valsalva maneuver or carotid sinus massage, followed by adenosine if they don't work.

What is AVNRT?

AV-nodal reentrant tachycardia — reentry within the AV node — the most common type of SVT.

How do you treat unstable SVT?

With synchronised cardioversion; recurrent SVT can be cured with catheter ablation.