What is the management approach for a patient experiencing supraventricular tachycardia (SVT)?

Management of Supraventricular Tachycardia

For acute SVT management, perform the modified Valsalva maneuver first (patient bears down for 10-30 seconds then immediately lies supine with legs raised), followed by adenosine 6 mg rapid IV push if vagal maneuvers fail, and proceed to synchronized cardioversion if the patient is hemodynamically unstable. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• If hemodynamically unstable (hypotension, altered mental status, chest pain, acute heart failure): proceed immediately to synchronized cardioversion at 50-100J 1, 3
• If hemodynamically stable: proceed with vagal maneuvers 1, 2

Step 2: Vagal Maneuvers (First-Line for Stable Patients)

• Modified Valsalva maneuver is superior to standard techniques, with a 43.7% success rate versus 17-24% for standard Valsalva 4, 2
  • Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) 1, 3
  • Immediately after, patient lies flat with legs raised 2
• Alternative vagal maneuvers if modified Valsalva fails 1, 3:
  • Carotid sinus massage: apply steady pressure over carotid sinus for 5-10 seconds after confirming absence of bruit 1, 3
  • Cold stimulus: apply ice-cold wet towel to face to trigger diving reflex 1, 3

Pitfall: Standard Valsalva alone has only 5-20% success rate; the modified technique with leg elevation significantly improves outcomes 5, 4

Step 3: Pharmacological Management (If Vagal Maneuvers Fail)

• Adenosine 6 mg rapid IV bolus through large vein, followed immediately by saline flush 2, 3

  • Success rate: 90-95% for AVNRT 2, 1
  • If unsuccessful, give 12 mg, then another 12 mg if needed 2
  • Caution: May precipitate atrial fibrillation; have cardioversion ready 3

• If adenosine fails or is contraindicated, use IV beta blockers or calcium channel blockers 2

Critical Warning: In patients with pre-excitation (Wolff-Parkinson-White syndrome) and atrial fibrillation, avoid AV nodal blocking agents (adenosine, beta blockers, calcium channel blockers) as they can accelerate ventricular rate and cause hemodynamic collapse 3, 6. Use IV procainamide instead if hemodynamically stable, or immediate cardioversion if unstable 6

Step 4: Synchronized Cardioversion

• Indicated when pharmacological therapy fails or is contraindicated in stable patients 1
• Initial energy: 50-100J for SVT 3
• Safe at all stages of pregnancy if necessary 2

Long-Term Management

Pharmacological Prevention

• Beta blockers are first-line for long-term prevention of recurrent SVT 2
• Calcium channel blockers (diltiazem, verapamil) are alternative options 2
• Flecainide may be used for paroxysmal SVT: start 50 mg every 12 hours, increase by 50 mg twice daily every 4 days as needed (maximum 300 mg/day for PSVT) 7

Important consideration: Steady-state levels with flecainide take 3-5 days; do not increase dose more frequently than every 4 days 7

Catheter Ablation (Definitive Treatment)

Catheter ablation is recommended as first-line for long-term management in patients with: 2, 8

• Frequent symptomatic episodes
• Poor medication tolerance or ineffectiveness
• Patient preference for non-pharmacological approach
• Wolff-Parkinson-White syndrome 8

Ablation has high success rates and should be considered early, with low threshold for cardiology referral 8

Special Populations

Pregnancy

• Vagal maneuvers remain safe and first-line 2
• Adenosine is safe due to short half-life 2
• Synchronized cardioversion can be performed safely at all stages 2

Patients with Low Baseline Heart Rate

• Use vagal maneuvers without concern for worsening bradycardia 3
• Consider reduced adenosine dosing with careful monitoring 3
• Consider synchronized cardioversion earlier in algorithm 3
• Avoid high doses of beta blockers and calcium channel blockers as they may exacerbate bradycardia 3

Diagnostic Essentials

• Always obtain 12-lead ECG to differentiate tachycardia mechanisms before treatment 2
• Distinguish SVT with aberrancy from ventricular tachycardia before initiating treatment 2
• Extended cardiac monitoring (Holter or event recorder) may be needed for diagnosis confirmation 8

Key Pitfall: Automatic tachycardias (ectopic atrial tachycardia, multifocal atrial tachycardia) may not respond to cardioversion and require different treatment approaches 3