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

Initial Management of Supraventricular Tachycardia (SVT)

The initial management of SVT should follow a stepwise approach with vagal maneuvers as first-line treatment for hemodynamically stable patients, followed by adenosine if unsuccessful, and immediate synchronized cardioversion for hemodynamically unstable patients. 1, 2

Assessment of Hemodynamic Stability

First, rapidly determine if the patient is hemodynamically stable or unstable:

• Unstable signs: Hypotension, altered mental status, signs of shock, severe shortness of breath, chest pain
• Stable signs: Normal blood pressure, alert and oriented, mild symptoms only

Management Algorithm

For Hemodynamically Unstable Patients:

1. Immediate synchronized cardioversion (Class I, Level B-NR)
   • Initial energy: 0.5-1 J/kg
   • Increase to 2 J/kg if unsuccessful
   • Do not delay with vagal maneuvers or medications 1, 2

For Hemodynamically Stable Patients:

1. Vagal maneuvers (Class I, Level B-R)

   • Valsalva maneuver: Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure)
   • Modified Valsalva: Perform standard Valsalva followed by passive leg raise (43% effective)
   • Carotid sinus massage: Apply steady pressure over right or left carotid sinus for 5-10 seconds after confirming absence of carotid bruit
   • Cold stimulus: Apply ice-cold wet towel to face 1, 2

2. If vagal maneuvers fail, administer IV adenosine (Class I, Level B-R)

   • Initial dose: 6 mg rapid IV push followed by saline flush
   • If unsuccessful: 12 mg IV push (can repeat once if needed)
   • Success rate: approximately 95% 1, 2

3. If adenosine fails, administer IV calcium channel blockers or beta blockers (Class IIa, Level B-R)

   • Options include diltiazem, verapamil, or beta blockers
   • Only use in hemodynamically stable patients without heart failure 1, 2

4. If pharmacological therapy fails, perform synchronized cardioversion (Class I, Level B-NR) 1, 2

Important Considerations and Pitfalls

• Avoid calcium channel blockers and beta blockers if:

  • Suspected ventricular tachycardia
  • Pre-excited atrial fibrillation (can cause hemodynamic collapse)
  • Heart failure or hypotension 2

• Avoid verapamil in infants and children <1 year due to risk of cardiovascular collapse 2

• Diagnostic errors: SVT may be mistaken for ventricular tachycardia with aberrancy. When uncertain, treat as ventricular tachycardia 2, 3

• Monitoring: All patients should have continuous cardiac monitoring and frequent vital sign checks during treatment 2

• Eyeball pressure is potentially dangerous and should be avoided 1

• Delayed recognition of unstable SVT is a common error - always assess perfusion and mental status promptly 4

The American College of Cardiology/American Heart Association guidelines emphasize that while vagal maneuvers and adenosine are effective first-line treatments for stable patients, immediate synchronized cardioversion is essential for unstable patients to prevent adverse outcomes 1, 2, 5.