What is the first-line drug for treating supraventricular tachycardia (SVT)?

First-Line Drug for Supraventricular Tachycardia (SVT)

Adenosine is the recommended first-line drug for treating hemodynamically stable supraventricular tachycardia (SVT) when vagal maneuvers have been unsuccessful. 1, 2

Treatment Algorithm for SVT

1. Initial Management:

   • First attempt vagal maneuvers (Valsalva maneuver or carotid sinus massage)
   • If vagal maneuvers fail, proceed to adenosine

2. Adenosine Administration:

   • Initial dose: 6 mg IV rapid bolus via proximal IV access
   • If ineffective after 1-2 minutes: 12 mg IV push
   • May repeat 12 mg dose once more if needed
   • Success rate: 90-95% for terminating SVT 1
   • Administer with continuous ECG monitoring

3. If Adenosine Fails:

   • For hemodynamically stable patients:

     • Calcium channel blockers (diltiazem or verapamil) with 64-98% termination rate 1
     • Beta blockers (esmolol, metoprolol, propranolol)

   • For hemodynamically unstable patients:

     • Immediate synchronized cardioversion (50-100 J) 1

Evidence Supporting Adenosine as First-Line

Adenosine is recommended as the first-line pharmacological treatment for SVT based on:

• High efficacy (95% success rate in terminating AVNRT) 2
• Rapid onset of action (peak effect within 3-5 minutes)
• Short half-life (approximately 4 minutes) 3
• Diagnostic utility in unmasking underlying rhythm disorders 1
• Safety profile (transient side effects)

Recent data from 2023 confirms an overall response rate of 86% to adenosine for paroxysmal SVT in emergency department settings 4.

Important Considerations and Precautions

• Contraindications to adenosine:

  • Second or third-degree AV block
  • Sick sinus syndrome
  • Known hypersensitivity

• Calcium channel blockers (verapamil/diltiazem) should be avoided in:

  • Suspected systolic heart failure
  • Hypotension
  • Pre-excited atrial fibrillation
  • Ventricular tachycardia 1

• Beta blockers should be used cautiously in:

  • Severe conduction abnormalities
  • Sinus node dysfunction
  • Bronchospastic disease 1

• Common pitfall: Recurrence of SVT after initial conversion with adenosine (reported in up to 57% of cases) 5. In such cases, consider alternative antiarrhythmic agents rather than repeated adenosine doses.

• Special populations:

  • Pregnant patients: Vagal maneuvers and adenosine are preferred, starting with lower doses 1
  • Children: Adenosine is effective but may require weight-based dosing 6

Long-term Management Considerations

After successful acute termination with adenosine, consider:

• Electrophysiological study with catheter ablation (95% success rate for AVNRT)
• Oral medications for ongoing management (beta blockers, diltiazem, or verapamil)
• Flecainide or propafenone for patients without structural heart disease 1

Adenosine's rapid action and safety profile make it the optimal first-line agent for SVT, with calcium channel blockers or synchronized cardioversion as appropriate next steps if adenosine fails.