What is the treatment for supraventricular tachycardia (SVT)?

Treatment of Supraventricular Tachycardia (SVT)

The most effective treatment approach for SVT follows a stepwise algorithm beginning with vagal maneuvers, followed by adenosine, then calcium channel blockers or beta blockers, and finally synchronized cardioversion if necessary. 1, 2

Acute Management of SVT

First-Line: Vagal Maneuvers

• Modified Valsalva maneuver is the most effective vagal technique with a success rate of approximately 43% 3
  • Technique: Patient bears down against closed glottis for 10-30 seconds
  • Modified technique (patient supine with legs elevated after strain) has significantly higher success rates than standard Valsalva 4
• Carotid sinus massage is an alternative but less effective than modified Valsalva 4
• These techniques increase vagal tone to slow conduction through the AV node 2

Second-Line: Adenosine

• Recommended dose: 6 mg rapid IV push followed by saline flush 2, 5
• If unsuccessful, may administer 12 mg IV push after 1-2 minutes
• Success rate approximately 91% 2, 3
• Mechanism: Temporarily blocks AV nodal conduction
• Extremely short half-life (< 10 seconds) 5
• Common side effects: flushing, chest discomfort, dyspnea, headache 5
• Contraindications:
  • Second or third-degree AV block (without functioning pacemaker)
  • Sick sinus syndrome
  • Bronchospastic lung disease
  • Known hypersensitivity 5

Third-Line: Calcium Channel Blockers or Beta Blockers

• Options for hemodynamically stable patients:
  • IV diltiazem or verapamil (Class IIa, Level B-R) 1, 2
  • IV beta blockers (Class IIa, Level C-LD) 1, 2
• Verapamil contraindications:
  • Severe left ventricular dysfunction
  • Accessory bypass tracts (Wolff-Parkinson-White syndrome)
  • Concurrent beta-blocker use 6

Fourth-Line: Synchronized Cardioversion

• Indicated for:
  • Hemodynamically unstable patients (first-line in this scenario)
  • When medications are ineffective or contraindicated 1, 2
• Initial energy: 0.5-1 J/kg, increasing to 2 J/kg if unsuccessful 2

Long-Term Management

Pharmacological Options

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

   • Oral beta blockers
   • Oral diltiazem
   • Oral verapamil 1

2. Second-line medications (Class IIa, Level B-R):

   • Flecainide or propafenone (for patients without structural heart disease) 1

3. Third-line medications:

   • Sotalol (Class IIb, Level B-R)
   • Dofetilide (Class IIb, Level B-R)
   • Amiodarone (Class IIb, Level C-LD) 1

Definitive Treatment

• Electrophysiology study with catheter ablation is highly effective (success rates 94-98%) 3
• Recommended for:
  • Recurrent symptomatic episodes
  • Patients who prefer definitive treatment over long-term medication
  • Those with tachycardia-induced cardiomyopathy 1, 3

Special Considerations

• Wolff-Parkinson-White Syndrome: Avoid verapamil and digoxin as they can accelerate conduction through accessory pathways, potentially causing ventricular fibrillation 6
• Pregnancy: Follow same algorithm but position electrodes to direct energy away from uterus if cardioversion is needed 2
• Hemodynamically unstable patients: Proceed directly to synchronized cardioversion 1, 2
• Pediatric patients: Higher weight-based dosing of adenosine may be required; avoid verapamil in infants due to risk of cardiovascular collapse 2

Treatment Algorithm Summary

1. Vagal maneuvers (modified Valsalva preferred)
2. Adenosine IV if vagal maneuvers fail
3. IV calcium channel blockers or beta blockers if adenosine fails
4. Synchronized cardioversion if medications fail or patient is unstable
5. Consider long-term oral medications or catheter ablation for recurrent episodes