What is the treatment for refractory supraventricular tachycardia (SVT)?

Treatment of Refractory Supraventricular Tachycardia (SVT)

Synchronized cardioversion is the recommended treatment for refractory SVT when pharmacological therapy is ineffective or contraindicated. 1

Initial Management Algorithm for SVT

1. First-line approaches for hemodynamically stable patients:

   • Vagal maneuvers (Class I, Level B-R) 2
     • Modified Valsalva maneuver (more effective than standard Valsalva) 3
     • Carotid sinus massage
     • Ice-cold wet towel to face (diving reflex)
   • Adenosine IV (Class I, Level B-R) 2
     • Highly effective in terminating AVNRT
     • Rapid onset and short half-life
     • Use with caution in patients on digoxin or verapamil due to rare risk of ventricular fibrillation 4

2. Second-line pharmacological options:

   • IV calcium channel blockers (Class IIa, Level B-R) 1, 2
     • Diltiazem or verapamil can terminate SVT in 64-98% of patients
     • Contraindicated in systolic heart failure
     • Avoid in suspected VT or pre-excited AF
   • IV beta blockers (Class IIa, Level B-R) 1, 2
     • Less effective than calcium channel blockers but excellent safety profile

Management of Refractory SVT

When SVT is refractory to the above measures:

1. Synchronized cardioversion (Class I, Level B-NR) 1, 2

   • Highly effective for terminating persistent SVT
   • Indicated when:
     • Pharmacological therapy is ineffective or contraindicated
     • Patient becomes hemodynamically unstable
   • Requires adequate sedation or anesthesia in stable patients

2. Alternative pharmacological approaches:

   • Consider higher doses of initial agents or a second drug bolus 1
   • For long-term prevention in patients without structural heart disease:
     • Flecainide (Class IIa) 2, 5
       • Indicated for prevention of PSVT
       • Contraindicated in patients with recent MI or structural heart disease
     • Amiodarone (Class IIa, Level B) 2
       • Consider for refractory cases

Long-term Management of Recurrent SVT

1. Catheter ablation (Class I, Level B-R) 2

   • Recommended for recurrent, symptomatic SVT
   • Curative in majority of patients
   • First-line therapy for patients with WPW syndrome

2. Chronic pharmacological therapy:

   • Beta blockers (first-line) 2
   • Calcium channel blockers (Class IIa, Level B-R) 2
   • Flecainide for prevention of PSVT in patients without structural heart disease 5

Important Clinical Considerations

• Always rule out pre-excited AF before administering calcium channel blockers or beta blockers, as these can accelerate ventricular rate and lead to ventricular fibrillation 1, 2

• Synchronized cardioversion should not be delayed in hemodynamically unstable patients 2

• Adenosine effects are antagonized by methylxanthines (caffeine, theophylline) and potentiated by dipyridamole, requiring dose adjustments 4

• In pediatric patients with difficult IV access, intraosseous (IO) administration of adenosine has been reported as effective 6

• Recurrence of SVT may occur within minutes after successful conversion with adenosine due to its short half-life 7

By following this stepwise approach, most cases of refractory SVT can be successfully managed, with synchronized cardioversion being the definitive treatment when pharmacological options fail.