How should I manage a patient presenting with supraventricular tachycardia, including acute termination and long‑term therapy?

Management of Supraventricular Tachycardia

For hemodynamically stable SVT, attempt vagal maneuvers first (modified Valsalva maneuver achieves 43% conversion), followed immediately by adenosine 6 mg IV push if unsuccessful (90–95% effective for AVNRT); for hemodynamically unstable patients, proceed directly to synchronized cardioversion without attempting any other intervention. 1

Immediate Assessment: Hemodynamic Stability

Determine stability within seconds of patient contact. Hemodynamic instability is defined by any of the following: 1

• Systolic blood pressure < 90 mmHg
• Altered mental status or loss of consciousness
• Clinical signs of shock (cold extremities, poor perfusion)
• Acute heart failure (pulmonary edema, severe dyspnea)
• Ongoing chest pain suggesting myocardial ischemia

If any of these are present, proceed immediately to synchronized cardioversion—do not attempt vagal maneuvers or pharmacologic therapy. 1

Management of Hemodynamically Unstable SVT

Synchronized cardioversion is the definitive first-line treatment and restores sinus rhythm in virtually 100% of unstable cases. 1

• Deliver synchronized shock immediately after brief sedation if the patient is conscious 1
• Use 50–100 J initial energy for SVT 1
• Do not delay for vagal maneuvers or adenosine administration 1

Management of Hemodynamically Stable SVT

Step 1: Vagal Maneuvers (First-Line)

Attempt vagal maneuvers before any pharmacologic therapy. 1

Modified Valsalva Maneuver (Most Effective)

• Position patient supine 2
• Patient bears down against closed glottis for 10–30 seconds 2
• Generate intrathoracic pressure of 30–40 mmHg 2
• Success rate: 43% for modified technique vs. 17% for standard technique 2
• Modified Valsalva is 2.8–3.8 times more effective than standard technique 2

Alternative Vagal Maneuvers

• Carotid sinus massage: Apply steady pressure over carotid sinus for 5–10 seconds after confirming absence of bruit by auscultation 1
• Ice-water facial immersion: Place ice-cold wet towel on face 1
• Critical safety warning: Never apply pressure to the eyeball 1

Overall success rate of all vagal maneuvers combined: approximately 27–28% 1

Step 2: Adenosine (First-Line Pharmacologic Agent)

If vagal maneuvers fail, adenosine is the preferred drug, achieving 90–95% conversion for AVNRT and 78–96% for AVRT. 1

Standard Dosing Protocol

• Initial dose: 6 mg rapid IV bolus over 1–2 seconds through large proximal vein (antecubital preferred) 1
• Follow immediately with 20 mL saline flush 1
• Second dose: 12 mg if no conversion within 1–2 minutes 1
• Third dose: 12 mg if still no response 1
• Maximum cumulative dose: 30 mg total (6 + 12 + 12) 1

Dose Adjustments for Special Populations

Reduce initial dose to 3 mg in: 1

• Patients taking dipyridamole or carbamazepine
• Cardiac transplant recipients (denervated hearts)
• Administration via central venous access

Increase dose requirements in patients with significant blood levels of: 1

• Theophylline
• Caffeine
• Theobromine

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 (e.g., Wolff-Parkinson-White syndrome) 1

Expected Response and Side Effects

• Average time to termination: 30 seconds after effective dose 1
• Common transient side effects (<60 seconds): flushing, dyspnea, chest discomfort 1
• Have defibrillator available when WPW syndrome is a consideration, due to risk of initiating atrial fibrillation with rapid ventricular rates 1

Diagnostic Value

• Adenosine serves dual therapeutic-diagnostic role: it terminates SVT but can unmask underlying atrial flutter or atrial tachycardia by producing transient AV block 1
• Obtain continuous ECG recording during administration to distinguish drug failure from successful termination with immediate reinitiation 1

Step 3: Alternative Pharmacologic Agents (When Adenosine Fails or Is Contraindicated)

Intravenous Calcium-Channel Blockers (Preferred Alternatives)

Diltiazem is the preferred alternative for patients with asthma or COPD, achieving 64–98% conversion. 1

• Diltiazem dosing: 15–20 mg (≈0.25 mg/kg) IV over 2 minutes 1
• Verapamil dosing: 2.5–5 mg IV over 2 minutes, with clinical effect within 3–5 minutes 1

Absolute contraindications for calcium-channel blockers—do NOT administer if: 1

• Ventricular tachycardia cannot be excluded
• Pre-excited atrial fibrillation (e.g., WPW syndrome) is present—risk of ventricular fibrillation
• Suspected systolic heart failure or severe left-ventricular dysfunction
• Hemodynamic instability

Intravenous Beta-Blockers

• Metoprolol: 2.5–5 mg IV every 2–5 minutes; maximum cumulative dose 15 mg over 10–15 minutes 1
• Esmolol is useful for short-term rate control, particularly when concurrent hypertension is present 1
• Use carefully in severe COPD 1
• Never combine IV calcium-channel blockers with IV beta-blockers due to synergistic hypotensive and bradycardic effects 1

Step 4: Synchronized Cardioversion (Drug-Refractory or Contraindicated Cases)

Elective synchronized cardioversion achieves near-100% termination of SVT when pharmacologic therapy is ineffective or contraindicated in stable patients. 1

• Use 50–100 J initial energy 1
• Provide appropriate sedation before cardioversion 1

Post-Conversion Management

Immediate Monitoring

• Continue continuous ECG monitoring for early recurrence, as premature complexes can trigger repeat SVT episodes 1
• Atrial or ventricular premature complexes commonly occur immediately after conversion 1

Management of Recurrent SVT

• If immediate recurrence occurs, administer a longer-acting AV-nodal blocker (diltiazem or β-blocker) 1
• If adenosine reveals another form of SVT (e.g., atrial flutter or atrial tachycardia), consider treatment with a longer-acting AV-nodal blocking agent 1

Long-Term Management

First-Line: Catheter Ablation

Catheter ablation should be considered as first-line therapy for preventing recurrent SVT, as it is the most effective, safe, and cost-effective approach. 1

• Single-procedure success rates: 94.3–98.5% 3
• More cost-effective than long-term medical therapy 1

Alternative: Long-Term Pharmacologic Therapy

Oral beta-blockers, diltiazem, or verapamil are reasonable options for long-term prevention of AVNRT. 1

Patient Education and Self-Management

• Teach vagal maneuvers (modified Valsalva maneuver, carotid massage, ice-water facial immersion) for self-termination of future episodes 1
• Consider "pill-in-the-pocket" therapy as a personalized, self-directed intervention 1
• Include patient in clinical decision-making, considering preferences, goals, and unique physical, psychological, and social situation 1

Special Populations

Pregnancy

• Vagal maneuvers remain first-line approach 1
• Adenosine is safe and effective during pregnancy 1
• If patient becomes hemodynamically unstable, electrical cardioversion is indicated 1

Adult Congenital Heart Disease

• Intravenous adenosine is appropriate for SVT termination 1
• Intravenous diltiazem or esmolol may be used cautiously, monitoring for hypotension 1
• Flecainide should be avoided in presence of significant ventricular dysfunction 1
• Acute antithrombotic therapy is recommended for atrial tachycardia or atrial flutter, following atrial fibrillation guidelines 1

Critical Diagnostic Considerations

• Obtain 12-lead ECG during tachycardia to differentiate SVT mechanisms and exclude ventricular tachycardia or pre-excited atrial fibrillation 1
• When differential diagnosis between SVT and ventricular tachycardia is uncertain, treat as ventricular tachycardia to avoid the greater risk of undertreatment 1

Common Pitfalls to Avoid

• Do not delay cardioversion in hemodynamically unstable patients to attempt drug therapy 1
• Do not administer calcium-channel blockers when ventricular tachycardia or pre-excited atrial fibrillation cannot be excluded 1
• Do not use adenosine in patients with asthma due to risk of severe bronchospasm 1
• Do not employ eyeball pressure as a vagal maneuver—it is dangerous and no longer recommended 1
• Do not combine IV calcium-channel blockers with IV beta-blockers 1