What is the initial assessment and treatment plan for a patient presenting with supraventricular tachycardia (SVT)?

Assessment and Management of Supraventricular Tachycardia (SVT)

The initial assessment and treatment of SVT should follow a structured algorithm based on hemodynamic stability, with vagal maneuvers as first-line for stable patients, adenosine as second-line, and synchronized cardioversion for unstable patients. 1

Initial Assessment

Hemodynamic Evaluation

• Immediately assess for signs of hemodynamic instability:
  • Hypotension
  • Altered mental status
  • Signs of shock
  • Chest pain
  • Acute heart failure symptoms 2

ECG Assessment

• Confirm regular, narrow QRS complex tachycardia
• Look for hidden or inverted P waves
• Rule out ventricular tachycardia with aberrancy (if uncertain, treat as ventricular tachycardia) 1

Treatment Algorithm

For Hemodynamically Unstable Patients

1. Immediate synchronized cardioversion (Class I, Level B-NR)
   • Initial energy: 0.5-1 J/kg 1
   • Ensure proper sedation when possible 2

For Hemodynamically Stable Patients

1. First-line: Vagal Maneuvers (Class I, Level B-R)

   • Modified Valsalva maneuver (most effective)
   • Carotid sinus massage (in appropriate patients)
   • Facial ice application 1
   • Success rate of vagal maneuvers: approximately 27.7% 1

2. Second-line: Adenosine IV (Class I, Level B-R)

   • Initial dose: 6 mg rapid IV bolus
   • If ineffective, up to 2 subsequent doses of 12 mg 1, 3
   • Administer as rapid bolus followed by saline flush
   • Warn patient about transient side effects (flushing, chest discomfort, dyspnea) 3
   • Success rate: approximately 91% 4

3. Third-line: IV Calcium Channel Blockers or Beta Blockers (Class IIa, Level B-R)

   • Diltiazem or verapamil IV (64-98% effective) 2
     • CAUTION: Avoid in suspected heart failure, ventricular tachycardia, or pre-excited AF 2, 1
   • Beta blockers IV (e.g., esmolol) 2
     • Particularly useful for short-term control of both SVT and hypertension 2

4. Fourth-line: Synchronized Cardioversion (Class I, Level B-NR)

   • For patients who fail pharmacological therapy 2
   • Ensure adequate sedation or anesthesia 2

Special Considerations

Common Pitfalls to Avoid

• Misdiagnosis: Mistaking ventricular tachycardia for SVT with aberrancy 1
• Incorrect adenosine administration: Must be given as rapid bolus with immediate saline flush 3
• Inappropriate use of calcium channel blockers: Avoid in patients with suspected ventricular tachycardia, pre-excited atrial fibrillation, or systolic heart failure 2, 1
• Delayed cardioversion in unstable patients: Should be immediate, not delayed for trials of medications 5

Specific SVT Types

• Atrioventricular nodal reentrant tachycardia (AVNRT): Most common type of SVT
• Atrioventricular reentrant tachycardia (AVRT): Assess for accessory pathways (e.g., Wolff-Parkinson-White syndrome)
• Atrial tachycardia: May be more resistant to adenosine 6

Long-term Management

• Catheter ablation: Recommended as first-line therapy for recurrent, symptomatic SVT (Class I, Level B-NR)

  • Success rates: 93-98.5% 1, 4
  • Low complication rates (approximately 3%) 1

• Pharmacological options if ablation not feasible:

  • Beta blockers
  • Calcium channel blockers (non-dihydropyridine)
  • Consider RAAS blockade (ACE inhibitors or ARBs) in patients with LVH 2

The acute management approach to SVT is well-established with strong evidence supporting a stepwise approach based on hemodynamic stability. For recurrent episodes, catheter ablation offers the highest success rate and should be considered early in management.