What is the treatment for Supraventricular Tachycardia (SVT) episodes?

Treatment for Supraventricular Tachycardia (SVT)

The first-line treatment for SVT episodes is vagal maneuvers, particularly the modified Valsalva maneuver (MVM), which is significantly more effective than standard Valsalva maneuver or carotid sinus massage for converting SVT to normal sinus rhythm. 1, 2

Acute Management Algorithm

Step 1: Vagal Maneuvers

• Modified Valsalva maneuver is the most effective vagal technique with success rates of 43.7% initially and 28.1% sustained at 5 minutes 3
• Perform in supine position: patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure), then immediately lie flat with legs raised 2, 4
• Alternative vagal maneuvers if MVM fails:
  • Standard Valsalva maneuver (success rate 24.2%) 3
  • Carotid sinus massage after confirming absence of carotid bruits (success rate 9.1%) 2, 3
  • Cold stimulus to face (applying ice-cold wet towel) to trigger diving reflex 4

Step 2: Pharmacological Management (if vagal maneuvers fail)

• Adenosine: First-line medication with 90-95% effectiveness 2

  • Initial dose: 6 mg rapid IV bolus followed by saline flush
  • If ineffective, up to 2 subsequent doses of 12 mg may be administered 2
  • Be prepared for potential brief side effects and have cardioversion equipment ready (adenosine may precipitate atrial fibrillation) 2

• For hemodynamically stable patients who don't respond to adenosine:

  • IV beta blockers (e.g., metoprolol, esmolol) 2, 4
  • IV calcium channel blockers (e.g., diltiazem, verapamil) 2, 4
  • Caution: Avoid verapamil or diltiazem in patients with pre-excited AF as they may accelerate ventricular rate 2, 4

Step 3: Electrical Cardioversion

• Indicated for:
  • Hemodynamically unstable patients 2
  • When pharmacological therapy is ineffective or contraindicated 2
  • Pre-excited AF (synchronized cardioversion is highly effective) 2
• Initial energy: 50-100J for SVT 4

Long-term Management Options

Pharmacological Prevention

• Beta blockers: First-line for long-term prevention 4
• Calcium channel blockers (non-dihydropyridine): Alternative to beta blockers 4
• Class IC antiarrhythmics:
  • Flecainide: Indicated for prevention of PSVT and PAF in patients without structural heart disease 5
    • Warning: Should not be used in patients with recent myocardial infarction or significant ventricular dysfunction 2, 5
  • Propafenone: Effective for prevention of recurrent episodes 6

Definitive Treatment

• Catheter ablation: Curative in majority of patients with SVT 7
  • Consider for patients with:
    • Frequent symptomatic episodes
    • Poor tolerance or ineffectiveness of medications
    • Patient preference for non-pharmacological approach

Special Considerations

Pregnancy

• Vagal maneuvers are first-line and safe during pregnancy 2
• Adenosine is considered safe due to its short half-life 2
• Synchronized cardioversion can be performed safely at all stages of pregnancy if necessary 2

Patients with Pre-excitation

• Avoid AV nodal blocking agents (beta blockers, calcium channel blockers) in patients with pre-excited AF 2, 4
• For hemodynamically stable pre-excited AF, ibutilide or IV procainamide is recommended 2
• Immediate synchronized cardioversion for hemodynamically unstable pre-excited AF 2

Common Pitfalls and Caveats

• Always record a 12-lead ECG to differentiate tachycardia mechanisms before treatment 2
• Distinguish SVT with aberrancy from ventricular tachycardia before initiating treatment 2
• Monitor for transient side effects of adenosine (chest discomfort, flushing) 2
• Be prepared for potential induction of atrial fibrillation after adenosine administration 2, 4
• Flecainide can cause proarrhythmic effects, particularly in patients with structural heart disease 5