What is the initial management for a patient presenting with Supraventricular Tachycardia (SVT)?

Initial Management of Supraventricular Tachycardia (SVT)

For patients presenting with SVT, vagal maneuvers should be performed as the first-line intervention for acute treatment, followed by adenosine if vagal maneuvers are unsuccessful, and synchronized cardioversion for hemodynamically unstable patients. 1, 2

Step-by-Step Management Algorithm

1. Assess Hemodynamic Stability

• If patient is hemodynamically unstable (hypotension, altered mental status, signs of shock, severe chest pain):
  • Proceed directly to synchronized cardioversion (0.5-1 J/kg) 2

2. For Hemodynamically Stable Patients

• First-line: Vagal Maneuvers 1, 2

  • Modified Valsalva maneuver (most effective): 3, 4
    • Patient in supine position
    • Bear down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure)
    • Immediately after strain, lie flat and elevate legs (modified technique)
  • Carotid sinus massage (after confirming absence of carotid bruit):
    • Apply steady pressure over right or left carotid sinus for 5-10 seconds
  • Cold stimulus:
    • Apply ice-cold, wet towel to face

• Second-line: Adenosine IV (if vagal maneuvers fail) 1, 2, 5

  • Initial dose: 6 mg rapid IV bolus
  • If ineffective: Up to 2 subsequent doses of 12 mg may be administered
  • Administer via large peripheral vein followed by saline flush
  • Warn patient about transient side effects (chest discomfort, flushing, dyspnea)

• Third-line: IV Beta-Blockers or Calcium Channel Blockers 2

  • Beta-blockers (metoprolol, propranolol)
  • Calcium channel blockers (diltiazem, verapamil)
    • Contraindicated in heart failure, suspected ventricular tachycardia, or pre-excited atrial fibrillation

• Fourth-line: Synchronized Cardioversion 1, 2

  • For persistent SVT despite pharmacological therapy

Important Considerations and Pitfalls

Diagnostic Considerations

• Obtain 12-lead ECG to differentiate tachycardia mechanisms
• Critical to distinguish SVT from ventricular tachycardia (VT)
• When uncertain between SVT with aberrancy and VT, treat as VT 2

Contraindications and Cautions

• Adenosine: 5

  • Contraindicated in second/third-degree AV block (except with functioning pacemaker)
  • Contraindicated in sick sinus syndrome or symptomatic bradycardia
  • Contraindicated in bronchospastic lung disease
  • Can cause transient AV block, bronchospasm, hypotension

• Calcium Channel Blockers: 2

  • Avoid in pre-excited atrial fibrillation (can accelerate ventricular rate)
  • Avoid in systolic heart failure
  • Contraindicated in infants (risk of cardiovascular collapse)

• Common Errors to Avoid:

  • Delaying cardioversion in unstable patients
  • Using verapamil/diltiazem in pre-excited atrial fibrillation or VT
  • Applying pressure to eyeballs (dangerous and abandoned practice) 1

Special Populations

• Pregnancy: 1
  • Same management algorithm applies
  • Vagal maneuvers are first-line
  • Adenosine is safe (short half-life limits fetal exposure)
  • For cardioversion, position electrode pads to direct energy away from uterus

Follow-up Considerations

• Obtain follow-up ECG to assess for pre-excitation (WPW syndrome)
• Consider referral for electrophysiology study and catheter ablation for recurrent SVT 6
• Success rates for catheter ablation are 93-95% with low complication rates (3%) 2

The evidence strongly supports starting with vagal maneuvers, particularly the modified Valsalva technique which has shown superior efficacy compared to standard Valsalva or carotid sinus massage 3, 4. This approach prioritizes non-invasive methods first, escalating to pharmacological and electrical interventions as needed based on patient response and hemodynamic stability.