What is the guideline for management of Supraventricular Tachycardia (SVT)?

Management of Supraventricular Tachycardia (SVT)

For acute SVT management, begin with vagal maneuvers immediately, followed by IV adenosine if unsuccessful, and proceed to synchronized cardioversion for hemodynamically unstable patients or refractory cases. 1

Acute Management Algorithm

Step 1: Initial Assessment and Stabilization

• Obtain a 12-lead ECG immediately to differentiate tachycardia mechanisms and determine if the AV node is an obligate component of the circuit 1
• Assess hemodynamic stability: Look for altered consciousness, hypotension, chest pain, acute heart failure, or signs of shock 1
• Critical distinction: If QRS duration >120 ms, distinguish VT from SVT with aberrancy before treatment, as verapamil or diltiazem can cause ventricular fibrillation in VT or pre-excited atrial fibrillation 1

Step 2: Hemodynamically Unstable Patients

Perform immediate synchronized cardioversion if the patient shows signs of hemodynamic instability 1

• This is Class I recommendation with high-quality evidence
• Do not delay for vagal maneuvers or medications in unstable patients
• Cardioversion is highly effective for terminating all forms of SVT 1

Step 3: Hemodynamically Stable Patients - First-Line Therapy

Vagal maneuvers (Class I recommendation) 1

• Modified Valsalva maneuver is most effective (SUCRA: 0.9992,43-55% success rate) 2, 3:

  • Patient in supine position
  • Bear down against closed glottis for 10-30 seconds
  • Generate intrathoracic pressure of 30-40 mm Hg
  • Modified technique superior to standard Valsalva 2

• Carotid sinus massage (less effective than Valsalva):

  • Confirm absence of carotid bruit first
  • Apply steady pressure over right or left carotid sinus for 5-10 seconds
  • Never perform bilateral massage simultaneously 1

• Diving reflex: Apply ice-cold wet towel to face or facial immersion in 10°C water 1

• Success rate: Switching between techniques achieves 27.7% overall conversion 1

Step 4: Pharmacological Management if Vagal Maneuvers Fail

IV Adenosine (Class I recommendation, first-line medication) 1

• Dosing: 6 mg rapid IV bolus; if ineffective, give 12 mg (may repeat once) 1
• Efficacy: 90-95% conversion rate for AVNRT and orthodromic AVRT 1, 3
• Mechanism: Both therapeutic and diagnostic—terminates AV node-dependent SVT and unmasks atrial activity in other arrhythmias 1
• Critical warning: Have cardioversion immediately available, as adenosine may precipitate atrial fibrillation that conducts rapidly down an accessory pathway, potentially causing ventricular fibrillation 1
• Side effects: Brief (<1 min) chest discomfort, flushing, dyspnea in ~30% of patients 1

Step 5: Alternative IV Medications (Class IIa recommendation)

If adenosine fails or is contraindicated 1:

• IV diltiazem or verapamil (calcium channel blockers):

  • Particularly effective for AVNRT conversion
  • 80-98% success rate when combined with adenosine 1
  • Contraindications: VT, pre-excited AF, systolic heart failure, severe conduction abnormalities 1
  • Critical pitfall: Can cause hemodynamic collapse or ventricular fibrillation if given for VT or pre-excited AF 1

• IV beta blockers (metoprolol, esmolol):

  • Excellent safety profile but less effective than calcium channel blockers for acute termination 1
  • Avoid in severe bronchospasm, decompensated heart failure, or severe conduction disease 1

Step 6: Refractory Cases

Synchronized cardioversion (Class I recommendation) 1

• Indicated when pharmacological therapy fails or is contraindicated in stable patients
• Highly effective for terminating all SVT types
• Perform after adequate sedation/anesthesia in stable patients 1

Long-Term Management

Definitive Treatment

Catheter ablation is first-line therapy for recurrent symptomatic SVT (Class I recommendation) 1, 4, 3

• Success rates: 94.3-98.5% for single procedure 3
• Advantages: Curative, eliminates need for chronic medications, low complication rates 1
• Indications: Recurrent symptomatic episodes, patient preference, occupational requirements (pilots, drivers) 1
• Refer all patients with documented SVT to cardiac electrophysiologist for evaluation 1, 5

Pharmacological Suppression (When Ablation Declined or Not Available)

First-line oral medications (Class I recommendation) 1:

• Beta blockers, diltiazem, or verapamil for patients without ventricular pre-excitation
• Effective for reducing episode frequency and duration
• Safe long-term profile

Second-line agents (Class IIa recommendation) 1:

• Flecainide or propafenone (450-900 mg/day propafenone; 100-300 mg/day flecainide):
  • 86-93% probability of 12-month effective treatment
  • Contraindicated: Structural heart disease, ischemic heart disease, ventricular dysfunction (risk of proarrhythmia and sudden death) 1
  • Reserve for patients who fail AV nodal blockers

Third-line (Class IIb recommendation) 1:

• Sotalol: Can be used in structural heart disease (unlike flecainide/propafenone)

Patient Education

Teach patients to perform vagal maneuvers (Class I recommendation) 1

• Enables self-termination of episodes
• Reduces need for emergency department visits
• Valsalva maneuver most practical for self-administration

Special Populations

Pregnancy

• Vagal maneuvers: First-line, Class I 1
• Adenosine: Safe, Class I (short half-life prevents fetal exposure) 1
• Synchronized cardioversion: Safe at all stages of pregnancy when medications fail 1
• Avoid medications in first trimester when possible 1

Pre-excited Atrial Fibrillation (Wolff-Parkinson-White)

Critical management difference 1:

• Hemodynamically unstable: Immediate synchronized cardioversion (Class I)
• Hemodynamically stable: IV ibutilide or procainamide (Class I) 1
• Never use: AV nodal blockers (adenosine, beta blockers, calcium channel blockers, digoxin)—can accelerate ventricular rate and cause ventricular fibrillation 1

Congenital Heart Disease

• Flecainide is contraindicated (Class III harm) in patients with significant ventricular dysfunction or complex congenital heart disease (7 of 8 cardiac arrests occurred in this population) 1

Common Pitfalls to Avoid

1. Never give verapamil/diltiazem for wide-complex tachycardia until VT is excluded—can cause cardiovascular collapse 1
2. Never use AV nodal blockers in pre-excited AF—can precipitate ventricular fibrillation 1
3. Avoid flecainide/propafenone in structural heart disease—high risk of proarrhythmia and sudden death 1
4. Do not perform bilateral carotid massage—risk of cerebral hypoperfusion 1
5. Abandon eyeball pressure technique—potentially dangerous 1
6. Have cardioversion available when giving adenosine—may trigger rapid AF 1