What are the management options for Supraventricular Tachycardia (SVT)?

Management of Supraventricular Tachycardia (SVT)

For acute SVT management, perform vagal maneuvers first (modified Valsalva in supine position with legs raised), followed by adenosine 6 mg IV bolus if unsuccessful, and proceed to synchronized cardioversion for hemodynamically unstable patients or when pharmacological therapy fails. 1, 2, 3

Acute Management Algorithm

Step 1: Initial Assessment and Vagal Maneuvers

• Always obtain a 12-lead ECG before treatment to distinguish SVT from ventricular tachycardia and identify pre-excitation patterns 2, 3
• Perform vagal maneuvers immediately as first-line therapy (Class I recommendation) 1, 3:
  • Modified Valsalva maneuver: Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) in supine position, then immediately lies flat with legs raised 1, 2, 3
  • Carotid sinus massage: Apply steady pressure over right or left carotid sinus for 5-10 seconds after confirming absence of bruit by auscultation 1, 3
  • Cold stimulus: Apply ice-cold wet towel to face (diving reflex) 1, 3
  • Switching between techniques increases success rate to 27.7% 1, 3
  • The modified Valsalva maneuver is superior to standard Valsalva and carotid massage, with the highest effectiveness (SUCRA: 0.9992) 4

Critical pitfall: Never apply pressure to the eyeball—this practice is dangerous and abandoned 1, 3

Step 2: Pharmacological Therapy (Hemodynamically Stable Patients)

First-Line: Adenosine

• Adenosine 6 mg rapid IV bolus followed by saline flush (Class I recommendation) 1, 2, 3
• If ineffective, give up to two subsequent 12 mg doses 1
• Effectiveness: 90-95% conversion rate 1, 2, 3
• Serves both therapeutic and diagnostic purposes by unmasking atrial activity 1

Second-Line Options (if adenosine fails or contraindicated)

• IV calcium channel blockers (diltiazem or verapamil) are highly effective for AVNRT conversion (Class IIa recommendation) 1, 3
• IV beta-blockers are reasonable but less effective than calcium channel blockers (Class IIa recommendation) 1, 3

Critical contraindications for AV nodal blocking agents (verapamil, diltiazem, beta-blockers):

• Pre-excited atrial fibrillation (may accelerate ventricular rate and cause ventricular fibrillation) 3
• Ventricular tachycardia 3
• Suspected systolic heart failure 1

Step 3: Electrical Cardioversion

Hemodynamically Unstable Patients

• Immediate synchronized cardioversion (Class I recommendation) when vagal maneuvers and adenosine fail or are not feasible 1, 3

Hemodynamically Stable Patients

• Synchronized cardioversion when pharmacological therapy fails or is contraindicated (Class I recommendation) 1, 3
• Success rates: 80-98% for pharmacological therapy, but cardioversion is highly effective when drugs fail 1

Special Population: Pre-Excited Atrial Fibrillation

• Hemodynamically unstable: Immediate synchronized cardioversion (Class I) 3
• Hemodynamically stable: IV ibutilide or procainamide (Class I recommendation) 3
• Absolutely avoid: AV nodal blocking agents (adenosine, verapamil, diltiazem, beta-blockers) as they may precipitate ventricular fibrillation 3

Long-Term Management

Pharmacological Prevention

• Beta-blockers are first-line for long-term prevention of recurrent SVT 2
• Calcium channel blockers (oral diltiazem or verapamil) are alternative first-line options 2, 3
• Flecainide or propafenone are reasonable alternatives for patients without structural heart disease who are not candidates for ablation 3, 5, 6

Critical contraindications for flecainide:

• Recent myocardial infarction 5
• Structural heart disease or ventricular dysfunction 1, 5
• Proarrhythmic risk: 13% in sustained VT patients, with 26% incidence at higher doses 5

Definitive Treatment: Catheter Ablation

• Catheter ablation is the most effective long-term therapy with single-procedure success rates of 94.3-98.5% 7
• Provides potential cure without need for chronic pharmacological therapy 2, 3
• Indications for ablation:
  • Frequent symptomatic episodes 2
  • Poor tolerance or ineffectiveness of medications 2
  • Patient preference for non-pharmacological approach 2, 3
  • Occupational requirements 3

Patient Education

• Teach proper vagal maneuver techniques for self-management of future episodes 3
• Modified Valsalva maneuver in supine position is most effective for patient self-administration 2, 3

Pregnancy Considerations

• Vagal maneuvers remain first-line and are safe during pregnancy (Class I) 1, 2
• Adenosine is safe due to short half-life preventing fetal circulation exposure (Class I) 1, 2
• Synchronized cardioversion can be performed safely at all stages of pregnancy if necessary 2
• Avoid medications in first trimester when possible; use lowest effective doses with regular monitoring 1

Key Clinical Pitfalls to Avoid

• Never use calcium channel blockers or beta-blockers before confirming absence of pre-excitation or ventricular tachycardia 3
• Do not initiate flecainide in patients with structural heart disease or ventricular dysfunction 1, 5
• Avoid chronic atrial fibrillation treatment with flecainide (not adequately studied) 5
• Always confirm absence of carotid bruits before carotid massage 3
• Refer all SVT patients to heart rhythm specialist regardless of acute management success 8