What is the treatment for Supraventricular Tachycardia (SVT)?

Treatment of Supraventricular Tachycardia (SVT)

Begin with vagal maneuvers immediately in all hemodynamically stable patients, followed by intravenous adenosine if vagal maneuvers fail, and proceed directly to synchronized cardioversion for any hemodynamically unstable patient. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• Hemodynamically unstable patients (hypotension, altered mental status, chest pain, acute heart failure) require immediate synchronized cardioversion without attempting vagal maneuvers or medications 1
• Stable patients proceed to vagal maneuvers 1, 2

Step 2: Vagal Maneuvers (First-Line for Stable Patients)

Perform these maneuvers with the patient in the supine position 1, 2:

• Modified Valsalva maneuver is the most effective vagal technique, with significantly higher success rates than standard techniques 3, 4
• Standard Valsalva: Patient bears down against a closed glottis for 10-30 seconds, generating at least 30-40 mm Hg intrathoracic pressure 1
• Carotid sinus massage: Apply steady pressure over the right or left carotid sinus for 5-10 seconds, only after confirming absence of carotid bruit by auscultation 1, 2
• Ice-cold wet towel to the face (diving reflex) 1
• Switching between techniques increases overall success to approximately 27.7% 1, 2

Critical pitfall: Never apply pressure to the eyeball—this practice is dangerous and abandoned 1, 2

Step 3: Adenosine (First-Line Pharmacotherapy)

• Adenosine terminates AVNRT in 95% of patients and orthodromic AVRT in 90-95% of patients 1, 4
• Adenosine is 91% effective overall and serves both therapeutic and diagnostic purposes 2, 4
• Have electrical cardioversion immediately available when administering adenosine, as it may precipitate atrial fibrillation with rapid ventricular response or even ventricular fibrillation 1
• Minor side effects occur in approximately 30% of patients but last less than 1 minute 1

Step 4: Alternative Pharmacotherapy (If Adenosine Fails or Contraindicated)

For hemodynamically stable patients with regular narrow-complex SVT without pre-excitation 1, 2:

• Intravenous diltiazem or verapamil are highly effective for converting AVNRT to sinus rhythm (Class IIa recommendation) 1, 2
• Intravenous beta-blockers are reasonable but less effective than calcium channel blockers (Class IIa recommendation) 1, 2

Step 5: Synchronized Cardioversion

• Required for hemodynamically unstable patients when vagal maneuvers/adenosine fail or are not feasible 1
• Required for hemodynamically stable patients when pharmacological therapy fails or is contraindicated 1
• Highly effective in terminating all forms of SVT 1

Special Considerations for Pre-Excited Atrial Fibrillation

This is a life-threatening scenario requiring different management 1, 2:

• Hemodynamically unstable: Immediate synchronized cardioversion (Class I) 1, 2
• Hemodynamically stable: Intravenous ibutilide or procainamide (Class I) 1, 2
• Absolutely avoid AV nodal blocking agents (verapamil, diltiazem, beta-blockers, adenosine) in patients with suspected pre-excitation, as these may accelerate ventricular rate and precipitate ventricular fibrillation 2

Critical Diagnostic Pitfall

You must distinguish SVT from ventricular tachycardia before treatment 2. Administering calcium channel blockers or beta-blockers to a patient with ventricular tachycardia can cause hemodynamic collapse 2. When in doubt, treat as ventricular tachycardia or proceed directly to cardioversion.

Long-Term Management

Definitive Treatment

• Catheter ablation is the definitive treatment with 94.3-98.5% single-procedure success rates and should be offered to all patients with recurrent symptomatic SVT 2, 4
• Ablation provides cure without need for chronic pharmacotherapy 2, 4

Pharmacological Prevention (If Ablation Declined or Not Candidate)

For patients without ventricular pre-excitation 2:

• Oral beta-blockers, diltiazem, or verapamil as first-line chronic therapy 2
• Flecainide or propafenone for patients without structural heart disease who are not ablation candidates 2, 5

Critical contraindication: Flecainide should never be used in patients with recent myocardial infarction, structural heart disease, or chronic atrial fibrillation due to proarrhythmic risk (13-26% in high-risk patients) 5

Patient Education

• Teach proper vagal maneuver techniques for self-termination of future episodes 2
• Modified Valsalva maneuver in supine position is most effective for patient self-administration 2, 3