What are the first-line drugs for treating supraventricular tachycardia (SVT)?

First-Line Drugs for Supraventricular Tachycardia (SVT)

For hemodynamically stable SVT, adenosine IV is the first-line drug treatment, followed by intravenous diltiazem, verapamil, or beta blockers as second-line options. 1

Acute Management Algorithm for SVT

Hemodynamically Unstable Patients

1. Synchronized cardioversion (Class I, Level B-NR) 2, 1
   • Immediate treatment for patients with:
     • Hypotension
     • Acutely altered mental status
     • Signs of shock
     • Chest pain
     • Acute heart failure symptoms

Hemodynamically Stable Patients

1. First-line: Vagal maneuvers (Class I, Level B-R) 1

   • Can terminate up to 25% of paroxysmal SVTs
   • Should be attempted before pharmacological intervention

2. Second-line: Adenosine IV (Class I, Level B-R) 2, 1

   • Initial dose: 6 mg rapid IV bolus
   • If ineffective, may increase to 12 mg (up to two additional doses)
   • Acts within 12-25 seconds 3
   • Highly effective in terminating SVT involving the AV node

3. Third-line: IV calcium channel blockers (Class IIa, Level B-R) 2, 1

   • Diltiazem or verapamil
   • Effective in 64-98% of patients 2
   • Contraindicated in heart failure
   • Caution: Ensure tachycardia is not VT or pre-excited AF

4. Third-line alternative: IV beta blockers (Class IIa, Level C-LD) 2, 1

   • Less evidence for effectiveness compared to calcium channel blockers
   • Excellent safety profile

5. Fourth-line: Synchronized cardioversion (Class I, Level B-NR) 2

   • For cases resistant to pharmacological therapy

Long-Term Management Options

1. Oral medications (Class I, Level B-R) 2, 1

   • Beta blockers
   • Calcium channel blockers (diltiazem, verapamil)
   • Contraindicated in heart failure patients

2. Second-line oral options 1, 4

   • Flecainide (for patients without structural heart disease)
   • Propafenone (for patients without structural heart disease)
   • Starting dose for flecainide: 50 mg every 12 hours 4

3. Catheter ablation (Class I, Level B-NR) 1

   • Success rates of 93-95%
   • Low complication rates (approximately 3%)
   • Recommended for recurrent, symptomatic SVT
   • More cost-effective than long-term medical therapy for frequent episodes

Important Considerations and Pitfalls

• Avoid diltiazem/verapamil in patients with:

  • Suspected ventricular tachycardia
  • Pre-excited atrial fibrillation
  • Systolic heart failure 2

• Avoid flecainide in patients with:

  • Recent myocardial infarction
  • Structural heart disease 4

• Avoid digoxin in SVT management:

  • Potentially harmful and contraindicated in pre-excited AF
  • May increase risk of ventricular fibrillation 1

• Rapid identification of hemodynamic instability is crucial:

  • Delaying cardioversion in unstable patients can have significant consequences 1

• Drug selection considerations:

  • Adenosine has a very short half-life (0.6-10 seconds) with transient side effects 5
  • Verapamil takes longer to convert SVT (average 248 seconds) compared to adenosine (30 seconds) 6
  • Beta blockers have excellent safety profile but may be less effective than calcium channel blockers 2

By following this evidence-based approach to SVT management, clinicians can effectively treat both acute episodes and provide appropriate long-term management strategies to reduce recurrence and improve patient outcomes.