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

Initial Treatment for Supraventricular Tachycardia (SVT)

The initial treatment for SVT should follow a stepwise approach beginning with assessment of hemodynamic stability, followed by vagal maneuvers in stable patients, and adenosine administration if vagal maneuvers fail. 1

Assessment and Treatment Algorithm

Step 1: Assess Hemodynamic Stability

• If patient is unstable (hypotension, altered mental status, chest pain, heart failure):
  • Proceed immediately to synchronized cardioversion (Class I, Level B-NR) 1
  • Do not delay cardioversion to administer medications in an unstable patient

Step 2: For Hemodynamically Stable Patients

1. Vagal Maneuvers (Class I, Level B-R) 1

   • Position patient supine
   • Techniques include:
     • Modified Valsalva maneuver (most effective at 43% success rate) 2
     • Standard Valsalva maneuver
     • Carotid sinus massage (contraindicated in patients with carotid bruits)
     • Facial application of ice-cold wet towel

2. If vagal maneuvers fail, administer Adenosine (Class I, Level B-R) 1

   • Highly effective (91% success rate) 2
   • Acts as both diagnostic and therapeutic agent
   • Safe in pregnancy due to short half-life 1

3. If adenosine fails, consider:

   • IV calcium channel blockers (diltiazem or verapamil) (Class IIa, Level B-R) 1
     • Contraindicated in suspected pre-excited AF or VT
   • IV beta blockers (esmolol or metoprolol) (Class IIa, Level B-R) 1
     • Good safety profile but less effective than calcium channel blockers

4. If pharmacological therapy fails:

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

Important Considerations and Pitfalls

• Never attempt vagal maneuvers in a hypotensive patient as they may worsen hemodynamic status 1
• Adenosine should be administered rapidly via a large peripheral vein followed by saline flush
• Monitor patients closely when administering IV medications, especially for hypotension
• For patients with renal impairment, medication dosages may need adjustment and more careful monitoring 1
• In patients with structural heart disease, avoid Class IC antiarrhythmics like flecainide due to proarrhythmic risk 1, 3

Long-term Management

After initial treatment and stabilization:

• Refer to cardiology or electrophysiology within 1-2 weeks 1
• Consider catheter ablation as definitive treatment (94-98% success rate) 1, 2
• If pharmacological management is preferred:
  • AV nodal blockers (oral beta blockers, diltiazem, verapamil) for patients without ventricular pre-excitation 1
  • For paroxysmal SVT, flecainide starting at 50 mg every 12 hours may be used in patients without structural heart disease 3
  • Dosage may be increased in increments of 50 mg bid every four days until efficacy is achieved (maximum 300 mg/day) 3

Patient education should include teaching proper vagal maneuver techniques for self-management of episodes at home 1.