Targeted Pathway Ablation
SVT Ablation
Many supraventricular tachycardias depend on a small circuit that catheter ablation can target. This page explains ablation for AVNRT, accessory pathways including WPW, and related rhythms.
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Rationale
When Is Ablation Considered for SVT?
Supraventricular tachycardia (SVT) describes fast rhythms that depend on tissue above the ventricles. Episodes usually start and stop suddenly, may cause palpitations, breathlessness or light-headedness, and often occur in otherwise healthy hearts.
Options include observation, manoeuvres taught for episodes, medication and catheter ablation. Ablation is often discussed when episodes are frequent or disabling, when medicines are not suitable or tolerated, or when a patient prefers a procedure to long-term medication.
In certain forms, such as WPW with pre-excitation, assessment of risk may make ablation more strongly considered.
What Is Treated
The Main SVT Mechanisms
AVNRT
A re-entry circuit within or near the AV node. Ablation modifies one of its pathways while aiming to preserve normal conduction. See AVNRT.
AVRT and accessory pathways
An extra electrical connection between atria and ventricles forms part of the circuit. The pathway is located and ablated. In WPW it may be visible on the resting ECG. See WPW.
Atrial tachycardia
A focus in the atrium drives a regular rhythm. Mapping is used to locate its origin.
Your electrophysiologist will explain which mechanism applies to you; the approach and risks differ between them.
Diagnosis at the Same Time
Electrophysiology Study and Mapping
SVT ablation normally begins with an electrophysiology study. Catheters record electrical signals and the rhythm is studied from inside the heart, often with stimulation to reproduce the arrhythmia.
3D electroanatomical mapping may be used to reduce reliance on X-ray imaging and to visualise the target and nearby conduction tissue in complex or high-risk locations.
Targets
AVNRT, AVRT and Accessory Pathways
In AVNRT the circuit lies in or beside the AV node. Ablation targets the slow-pathway region while aiming to preserve normal AV conduction. See AVNRT.
In AVRT the circuit uses an extra electrical connection, an accessory pathway, between the upper and lower chambers. The electrophysiology study shows where along the valve rings the pathway lies, and ablation targets that connection.
Some pathways conduct only in one direction and are not visible on the resting ECG. Others cause pre-excitation, as in WPW syndrome. Pathways near the normal conduction system need particular care, and mapping or a different energy source may be chosen for that reason.
Pathways on the left side of the heart can need a different catheter route. The approach is planned individually.
The Procedure
How SVT Ablation Is Performed
Ablation is catheter-based and does not involve open surgery.
Access
Catheters are placed through veins, typically at the groin, with local anaesthesia and, where appropriate, sedation.
Study
The circuit is characterised and the rhythm may be induced under controlled conditions.
Radiofrequency energy is commonly used. Cryoablation may be selected when the target is close to the normal conduction system.
Check
The team tests whether the circuit can still be activated.
Recovery
Observation, then discharge when you are stable, as advised by your team.
After the Procedure
Results, Recurrence and Risks
For many patients ablation can end or greatly reduce SVT episodes, but no outcome can be guaranteed and the arrhythmia may recur, in which case a second procedure may be discussed.
Your physician will discuss these with you before the procedure.
Safety and choice
Recovery, Risks and Alternatives
Recovery
Observation after the procedure is followed by discharge once you are stable, as advised by your team. The groin site needs care for some days, with individual advice on lifting and exercise.
Possible risks
Bruising or bleeding at the groin, injury to a blood vessel and, rarely, injury to the heart. For AVNRT and for pathways near the AV node there is a small possibility of damaging normal conduction, which could require a pacemaker. Your doctor explains the risks that apply to you.
Recurrence
SVT can return after ablation. A repeat assessment then clarifies whether a second procedure or another strategy is appropriate.
Alternatives
Observation, vagal manoeuvres taught for episodes, medicines (see Antiarrhythmic Medication) and treatment of episodes in hospital when needed. Ablation is chosen when episodes are frequent or disabling, medicines are unsuitable or not tolerated, or a person prefers a procedure.
Questions
Frequently Asked Questions
Will I be awake during SVT ablation?
Do I need ablation for my first episode of SVT?
Is ablation for WPW different?
What if SVT returns?
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