Is supraventricular tachycardia (SVT) that fails initial therapy an indication for electrophysiological study and therapeutic ablation?

From the Guidelines

Yes, electrophysiological study (EPS) and therapeutic ablation are indicated for supraventricular tachycardia (SVT) with a heart rate of 241 beats per minute that has failed initial therapy. When SVT fails to respond to first-line treatments such as vagal maneuvers and adenosine, or if it recurs despite medical therapy with beta-blockers, calcium channel blockers, or antiarrhythmic drugs, catheter ablation becomes an appropriate next step 1. The procedure involves mapping the electrical pathways of the heart to identify the abnormal circuit or focus causing the tachycardia, followed by targeted ablation of this area using radiofrequency energy or cryotherapy.

Key Considerations

• This approach offers a potential cure rather than just symptom management, with success rates exceeding 95% for common SVT mechanisms like AV nodal reentrant tachycardia (AVNRT) or accessory pathway-mediated tachycardias 1.
• The procedure typically takes 2-4 hours, requires only conscious sedation or light anesthesia, and patients usually return home the same day or after overnight observation.
• Complications are rare (1-2%) but may include bleeding, infection, vascular damage, or rarely, the need for a pacemaker if the AV node is affected 1.

Decision Making

The decision to proceed with EPS and therapeutic ablation depends on various factors including the frequency and duration of tachycardia, tolerance of symptoms, effectiveness and tolerance of antiarrhythmic drugs, the need for lifelong drug therapy, and the presence of concomitant structural heart disease 1. Given the high success rate and low complication rate of catheter ablation, it has become a preferred therapy over long-term pharmacologic therapy for management of patients with AVNRT.

Recommendations

• Catheter ablation should be considered as a first-line therapy for patients with symptomatic SVT who have failed initial medical therapy or have a high burden of symptoms.
• The choice between ablation and medical therapy should be individualized based on patient preferences, lifestyle, and specific clinical circumstances.
• Slow-pathway ablation is the preferred approach for AVNRT due to its lower risk of complications, including heart block 1.

From the Research

Indications for Electrophysiological Study and Therapeutic Ablation

• Supraventricular tachycardia (SVT) that is unresponsive to initial therapy may be indicated for electrophysiological study and therapeutic ablation 2, 3, 4, 5, 6
• The decision to proceed with electrophysiological study and ablation is based on several factors, including the frequency and severity of symptoms, the presence of underlying heart disease, and the patient's preference 3, 4
• Electrophysiological study and ablation have been shown to be effective in treating SVT, with a success rate of 95% and a recurrence rate of less than 5% 2

Predictors of Successful Ablation

• Several studies have identified predictors of successful ablation, including:
  • A characteristic EKG recording of SVT 6
  • Termination of SVT with adenosine 6
  • Termination of SVT or symptoms with vagal maneuvers 6
  • An episode of SVT lasting ≥ 30 s on a monitor recording 6
  • Pre-excitation on the baseline EKG 6
• Patients who exhibit at least one of these features have a high probability of SVT induction and ablation, while those who exhibit none have a low probability 6

Underuse of Catheter Ablation

• Despite its effectiveness, catheter ablation is often underused as a first-line treatment for SVT 4
• The underuse of catheter ablation may be due to biases in the decision-making process, including the patient's age, symptoms, and number of antiarrhythmic drugs used before ablation 4