Management of Supraventricular Tachycardia
Begin with immediate assessment of hemodynamic stability; if the patient shows hypotension, altered mental status, shock, chest pain, or acute heart failure, proceed directly to synchronized cardioversion without attempting vagal maneuvers or medications—this restores sinus rhythm in nearly 100% of unstable SVT cases. 1
Acute Management Algorithm
Step 1: Hemodynamic Assessment (First 30 Seconds)
Unstable patients (any of the following):
Action: Immediate synchronized cardioversion after sedation if conscious 1, 2
Step 2: Hemodynamically Stable Patients – Vagal Maneuvers
Attempt vagal maneuvers first before any medication. 1, 2
Modified Valsalva maneuver (most effective, 43% success rate):
Carotid sinus massage (if no bruit present):
Ice-water facial immersion:
Overall vagal maneuver success: ~27–28% 1, 2
Critical safety warning: Never apply pressure to the eyeball—this technique has been abandoned due to danger. 1, 2
Step 3: First-Line Pharmacologic Therapy – Adenosine
If vagal maneuvers fail, adenosine is the drug of choice, achieving 90–95% conversion for AVNRT and 78–96% for AVRT. 1, 2
Dosing protocol:
- Initial dose: 6 mg rapid IV push over 1–2 seconds via large proximal vein (antecubital preferred), followed immediately by 20 mL saline flush 1
- Second dose: 12 mg IV push if no conversion within 1–2 minutes 1
- Third dose: 12 mg IV push if still no response 1
- Maximum cumulative dose: 30 mg total (6 + 12 + 12 mg) 1
Administration technique is critical:
- Use the most proximal IV access available (distal sites reduce efficacy) 1
- Deliver as rapid bolus over 1–2 seconds—slower push is ineffective due to <10 second half-life 1
- Immediate 20 mL saline flush to propel drug into central circulation 1
Expected response: Conversion occurs within ~30 seconds if effective; if no effect within 1–2 minutes, dose is insufficient 1
Dose adjustments:
- Reduce to 3 mg in patients taking dipyridamole or carbamazepine, cardiac transplant recipients, or when given via central venous access 1
- Increase dose in patients with significant theophylline, caffeine, or theobromine levels (competitive antagonists) 1
Common transient side effects (<60 seconds):
Absolute contraindications to adenosine:
- Asthma or active bronchospasm (risk of severe bronchospasm) 1
- Second- or third-degree AV block or sick sinus syndrome without pacemaker 1
- Pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome) 1
Safety requirement: Have defibrillator immediately available—adenosine can precipitate rapid atrial fibrillation 1, 2
Step 4: Second-Line Pharmacologic Therapy (Adenosine Fails or Contraindicated)
When adenosine is ineffective or contraindicated in stable patients, use a longer-acting AV-nodal blocker. 1
Calcium-channel blockers (preferred alternatives):
Diltiazem: 15–20 mg (0.25 mg/kg) IV over 2 minutes
Verapamil: 2.5–5 mg IV over 2 minutes
Beta-blockers:
- Metoprolol: 2.5–5 mg IV every 2–5 minutes (maximum 15 mg over 10–15 minutes) 1
- Esmolol: Useful for short-term control, especially with concurrent hypertension 1
- Slightly less effective than calcium-channel blockers but excellent safety profile 2
Critical safety contraindications for calcium-channel blockers—do NOT use if:
- Ventricular tachycardia cannot be excluded (risk of cardiovascular collapse) 1, 2
- Pre-excited atrial fibrillation present (risk of ventricular fibrillation) 1, 2
- Suspected systolic heart failure or severe LV dysfunction (negative inotropic effects) 1, 2
- Patient is hemodynamically unstable 1
Avoid concurrent IV calcium-channel blockers and beta-blockers due to synergistic hypotensive and bradycardic effects. 2
Step 5: Synchronized Cardioversion for Refractory Stable SVT
When pharmacologic therapy fails or is contraindicated in stable patients, elective synchronized cardioversion achieves near-100% termination of SVT. 1, 2
- Success rate: 80–98% when combined with prior drug therapy 2
- Provide appropriate sedation/anesthesia if patient conscious 2
Post-Conversion Management
Monitor continuously for immediate recurrence—premature atrial or ventricular complexes commonly trigger repeat SVT episodes within seconds to minutes. 1
If immediate recurrence occurs:
- Administer a longer-acting AV-nodal blocker (diltiazem or beta-blocker) for prophylaxis 1
- Consider antiarrhythmic drug to prevent acute reinitiation 1
If adenosine reveals underlying atrial flutter or atrial tachycardia (by transient AV block):
- Shift management to rate control with longer-acting AV-nodal blocker rather than rhythm conversion 1
Long-Term Management Strategy
Catheter ablation should be considered as first-line therapy for preventing recurrent SVT—it is the most effective, safe, and cost-effective approach. 1, 2
Catheter ablation efficacy:
- Single-procedure success rates: 94.3–98.5% 2, 5
- Particularly recommended for symptomatic recurrent AVNRT due to very low risk of AV block 6
Alternative: Long-term pharmacologic therapy (for patients who decline or are unsuitable for ablation):
Oral beta-blockers, diltiazem, or verapamil are reasonable options for AVNRT prevention 1, 2
Flecainide or propafenone are reasonable in patients without structural heart disease or ischemic heart disease 2
Sotalol may be used when first-line agents fail 2
Dofetilide is an option when beta-blockers, calcium-channel blockers, flecainide, and propafenone are ineffective or contraindicated 2
Patient Education for Self-Management
Teach all patients vagal maneuvers for self-termination of future episodes:
Consider "pill-in-the-pocket" therapy as a personalized, self-directed intervention developed in partnership with the patient. 1
Special Populations
Pregnancy
- Vagal maneuvers remain first-line 1
- Adenosine is safe and effective during pregnancy 1
- If hemodynamically unstable, electrical cardioversion is indicated 1
- Avoid antiarrhythmic medications, especially in first trimester 6
Adult Congenital Heart Disease (ACHD)
- IV adenosine is appropriate for SVT termination 1
- IV diltiazem or esmolol may be used cautiously, monitoring for hypotension 1
- Avoid flecainide in presence of significant ventricular dysfunction 1
- Acute antithrombotic therapy recommended for atrial tachycardia or flutter 1
Diagnostic Considerations
Obtain 12-lead ECG during tachycardia to differentiate SVT mechanisms and exclude ventricular tachycardia or pre-excited atrial fibrillation. 1
Adenosine serves dual therapeutic-diagnostic role:
- Terminates SVT involving AV node
- Can unmask underlying atrial flutter or atrial tachycardia by producing transient AV block 1
If any doubt whether rhythm is VT versus SVT with aberrancy, treat as VT—never give calcium-channel blockers or adenosine to wide-complex tachycardia of uncertain origin. 7
Common Pitfalls to Avoid
- Never apply pressure to the eyeball during vagal maneuvers 1, 2
- Never give calcium-channel blockers without first excluding VT, pre-excited AF, or heart failure 1, 2
- Never give adenosine to asthma patients due to severe bronchospasm risk 1
- Never use slow IV push for adenosine—must be rapid bolus over 1–2 seconds 1
- Never use distal IV access for adenosine—use most proximal vein available 1
- Do not use digoxin acutely for SVT termination—reserve for selected chronic management cases 2
- Have defibrillator ready when giving adenosine—brief asystole or rapid AF may occur 1, 2