What are the clinical treatment guidelines for supraventricular tachycardia (SVT)?

Clinical Treatment Guidelines for Supraventricular Tachycardia (SVT)

Vagal maneuvers and adenosine are the first-line treatments for acute management of hemodynamically stable SVT, while synchronized cardioversion is recommended for hemodynamically unstable patients or when pharmacological therapy fails. 1

Acute Management of SVT

First-Line Approaches

• Vagal maneuvers should be attempted first in hemodynamically stable patients with regular SVT 1
  • Valsalva maneuver: Have patient bear down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) 1
  • Modified Valsalva maneuver has higher success rates (43% vs 17% with standard technique) and should be preferred 2, 3
  • Carotid sinus massage: Apply steady pressure over carotid sinus for 5-10 seconds after confirming absence of bruits 1
  • Facial application of ice-cold wet towel (diving reflex) can also be effective 1

Pharmacological Management

• Adenosine is recommended if vagal maneuvers fail, with approximately 95% efficacy in terminating AVNRT 1, 4

  • Advantages include rapid onset and short half-life (few seconds) 4
  • Common side effects include chest discomfort, dyspnea, and flushing, which are transient 4
  • Caution: May precipitate atrial fibrillation that could conduct rapidly to ventricles 1

• For hemodynamically stable patients when adenosine fails or is contraindicated:

  • Intravenous diltiazem or verapamil are effective (64-98% success rate) 1
  • Intravenous beta blockers are reasonable alternatives 1
  • Caution: Avoid calcium channel blockers in patients with suspected systolic heart failure or pre-excited atrial fibrillation 1

Electrical Cardioversion

• Synchronized cardioversion is indicated for:

  • Hemodynamically unstable patients when vagal maneuvers or adenosine are ineffective or not feasible 1
  • Hemodynamically stable patients when pharmacological therapy is ineffective or contraindicated 1
  • Patients with pre-excited atrial fibrillation 1

• For pre-excited atrial fibrillation in hemodynamically stable patients:

  • Ibutilide or intravenous procainamide are beneficial 1
  • Avoid beta blockers, diltiazem, or verapamil as they may enhance conduction over accessory pathways 1

Long-Term Management of SVT

Pharmacological Options

• Oral beta blockers, diltiazem, or verapamil are first-line for ongoing management in patients without ventricular pre-excitation 1

• For patients not suitable for or preferring not to undergo catheter ablation:

  • Flecainide or propafenone are reasonable in patients without structural heart disease 1, 5, 6
    • Flecainide has shown 79% attack-free rate in PSVT and 31% in PAF 5
    • Propafenone demonstrated 47-53% attack-free rate in PSVT and 38-67% in PAF 6
  • Sotalol may be reasonable 1
  • Dofetilide may be considered when first-line agents are ineffective or contraindicated 1
  • Oral amiodarone may be considered when other options have failed 1
  • Oral digoxin may be reasonable in patients without pre-excitation 1

Definitive Treatment

• Electrophysiological study with catheter ablation is recommended for definitive diagnosis and treatment of SVT 1, 7
  • Curative in majority of patients 7
  • Should be considered based on frequency of symptoms, risk stratification, and patient preference 7

Common Pitfalls and Caveats

• Always record a 12-lead ECG to differentiate tachycardia mechanisms 1
• Avoid eyeball pressure as a vagal maneuver - this technique is potentially dangerous 1
• Ensure tachycardia is not ventricular tachycardia or pre-excited atrial fibrillation before administering calcium channel blockers 1
• Patients may have atrial or ventricular premature complexes immediately after cardioversion that could reinitiate tachycardia 1
• Patient education on performing vagal maneuvers is essential for ongoing management 1
• For pre-excited atrial fibrillation, avoid AV nodal blocking agents (beta blockers, calcium channel blockers, digoxin) as they may accelerate conduction through accessory pathways 1