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

SVT Treatment Algorithm

Hemodynamic Assessment First

Immediately assess hemodynamic stability before initiating any treatment—unstable patients require immediate synchronized cardioversion, while stable patients should begin with vagal maneuvers followed by adenosine. 1, 2

Signs of Instability:

• Hypotension 1, 3
• Altered mental status 1, 3
• Signs of shock 1, 3
• Chest pain 1, 3
• Acute heart failure 1, 3

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Treatment for HEMODYNAMICALLY UNSTABLE Patients

1. Immediate synchronized cardioversion 1, 2, 3
   • Perform after adequate sedation/anesthesia when possible 1
   • Initial biphasic energy: 50-100 J for SVT 4
   • Increase dose stepwise if initial shock fails 4
   • Do NOT attempt vagal maneuvers or medications first 1

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Treatment for HEMODYNAMICALLY STABLE Patients

Step 1: Vagal Maneuvers (First-Line)

• Modified Valsalva maneuver (most effective technique) 1, 3
  • Patient supine, bearing down against closed glottis for 10-30 seconds at 30-40 mmHg pressure 3
  • Immediately lie flat with legs elevated after strain 1
  • Success rate: approximately 43% 3
  • Overall vagal maneuver success: 27.7% 2
• Alternative: Carotid sinus massage 4

Step 2: Adenosine (If Vagal Maneuvers Fail)

• 6 mg rapid IV push through large peripheral vein (e.g., antecubital) 4
  • Follow with 20 mL saline flush 4
  • Success rate: 90-95% for AVNRT and orthodromic AVRT 1, 2
• If no conversion in 1-2 minutes: 12 mg rapid IV push 4
• Must have defibrillator immediately available 4, 1

Adenosine Dosing Adjustments:

• Reduce to 3 mg if patient taking dipyridamole, carbamazepine, has transplanted heart, or central venous access 4
• Larger doses may be needed with theophylline, caffeine, or theobromine 4
• Safe in pregnancy 4
• Contraindicated in asthma 4, 5

Step 3: IV Calcium Channel Blockers or Beta-Blockers (If Adenosine Fails)

• IV diltiazem or verapamil 2, 3
  • Success rate: 80-98% 2, 3
  • Diltiazem more effective than esmolol 3
• IV beta-blockers (reasonable alternative) 3

Step 4: Synchronized Cardioversion (If All Pharmacotherapy Fails)

• Perform after adequate sedation in stable patients 1
• Initial energy: 50-100 J biphasic 4

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Critical Safety Warnings

NEVER Use AV Nodal Blockers In:

• Wide-complex tachycardia (can precipitate ventricular fibrillation) 1, 3
• Known accessory pathways or pre-excited atrial fibrillation 1, 2
• Systolic heart failure (verapamil/diltiazem contraindicated) 1

For Pre-Excited Atrial Fibrillation:

• Use IV procainamide or ibutilide instead 2
• Avoid all AV nodal blocking agents 2

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Special Considerations for Automatic Tachycardias

Automatic tachycardias (ectopic atrial tachycardia, multifocal atrial tachycardia, junctional tachycardia) are NOT responsive to cardioversion and require rate control with AV nodal blocking agents. 4

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Long-Term Management Options

Definitive Therapy:

• Catheter ablation (most effective) 2, 3
  • Success rate: 94.3-98.5% 2, 6
  • Recommended as first-line for prevention of recurrence 2

Pharmacological Prevention (If Ablation Declined):

• Oral beta-blockers 2
• Oral diltiazem or verapamil 2, 3
• Flecainide or propafenone (only in patients without structural heart disease) 2

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Common Pitfalls to Avoid

• Never delay cardioversion in unstable patients to attempt vagal maneuvers or medications 1
• Never give calcium channel blockers or beta-blockers if VT or pre-excited AF suspected 3
• Always have resuscitation equipment available when administering adenosine 4, 5
• Do not use adenosine in asthma patients (can cause severe bronchoconstriction) 4, 5
• Recognize automatic tachycardias (gradual onset/offset) as they will not respond to cardioversion 4