What is the appropriate acute and long‑term management of recurrent supraventricular tachycardia in an adult without structural heart disease?

Management of Recurrent Supraventricular Tachycardia

Catheter ablation is the recommended first-line therapy for adults with recurrent symptomatic SVT without structural heart disease, offering definitive cure with single-procedure success rates of 94.3% to 98.5% and eliminating the need for lifelong medications. 1, 2

Acute Management Algorithm

Hemodynamic Assessment First

• Immediately perform synchronized cardioversion (after sedation if conscious) in any patient presenting with hypotension, altered mental status, ischemic chest pain, shock, or acute heart failure signs—this restores sinus rhythm in nearly 100% of unstable patients. 1, 3
• Do not attempt vagal maneuvers or pharmacologic therapy when the patient is hemodynamically unstable; proceed directly to cardioversion. 3

For Hemodynamically Stable Patients

Step 1: Vagal Maneuvers (Class I)

• Begin with modified Valsalva maneuver: patient bears down against closed glottis for 10-30 seconds (generating 30-40 mmHg intrathoracic pressure) while supine—this achieves conversion in approximately 43% of attempts. 1, 3
• If unsuccessful, perform carotid sinus massage (after confirming absence of bruit by auscultation): apply steady pressure over right or left carotid sinus for 5-10 seconds—avoid in elderly patients or those with known carotid disease. 1, 3
• Alternative: apply ice-cold wet towel to face (diving reflex). 1, 3
• Rotating between different vagal techniques increases overall success to 27.7%. 1, 3
• Never apply eyeball pressure—this technique is dangerous and has been abandoned. 1, 3

Step 2: Intravenous Adenosine (Class I)

• Administer IV adenosine if vagal maneuvers fail—this terminates SVT in 90-95% of patients. 1, 3, 2
• Transient side effects (flushing, chest discomfort, dyspnea) occur in approximately 30% but resolve within one minute due to adenosine's ultra-short half-life. 3
• Critical safety requirement: defibrillation equipment must be immediately available because adenosine can precipitate rapid atrial fibrillation requiring emergent cardioversion. 3

Step 3: IV Calcium Channel Blockers or Beta-Blockers (Class IIa)

• If adenosine fails or is contraindicated, administer IV diltiazem or verapamil—these convert SVT in 64-98% of hemodynamically stable patients. 1, 3
• Infuse slowly over up to 20 minutes to minimize hypotension risk. 3
• Absolute contraindication: Do not use calcium channel blockers if ventricular tachycardia or pre-excited atrial fibrillation is possible—they can precipitate ventricular fibrillation and hemodynamic collapse. 1, 3
• Avoid in patients with suspected systolic heart failure due to negative inotropic effects. 1, 3
• IV beta-blockers are reasonable alternatives with excellent safety profile but slightly lower efficacy than calcium channel blockers. 1, 3
• Never combine IV calcium channel blockers with IV beta-blockers due to synergistic hypotensive and bradycardic effects. 3

Step 4: Synchronized Cardioversion (Class I)

• When pharmacologic therapy fails or is contraindicated in stable patients, perform synchronized cardioversion with appropriate sedation/anesthesia—this achieves 80-98% success rate. 1, 3

Long-Term Management Strategy

First-Line: Catheter Ablation (Class I)

• Electrophysiology study with catheter ablation should be offered to all patients with symptomatic recurrent SVT as it provides potential for definitive cure without chronic pharmacotherapy. 1
• Single-procedure success rates: 94.3% to 98.5% for AVNRT and AVRT with low complication rates. 1, 2
• This is particularly appropriate for patients who desire freedom from medications and have access to experienced cardiac electrophysiologists. 1

Second-Line: Pharmacologic Prophylaxis

When ablation is declined or not feasible:

Tier 1 Medications (Class I for AVNRT; reasonable for all SVT):

• Oral verapamil (up to 480 mg/day) or diltiazem reduce SVT episode frequency and duration as documented in randomized controlled trials. 1
• Oral beta-blockers are equally effective with excellent safety profile. 1
• These AV nodal blockers are appropriate first-line prophylactic agents. 1

Tier 2 Medications (Class IIa - for patients without structural/ischemic heart disease):

• Flecainide (100-300 mg/day) or propafenone (450-900 mg/day) are reasonable when first-line agents fail. 1
• Randomized trials show 86-93% probability of 12 months of effective treatment (defined as <2 attacks). 1
• Absolute contraindication: These class IC agents carry proarrhythmia risk and are contraindicated in patients with any structural heart disease or ischemic heart disease. 1
• Reserve for patients in whom beta-blockers, diltiazem, or verapamil are ineffective or cannot be prescribed. 1

Tier 3 Medications (Class IIb - reserve for refractory cases):

• Sotalol (80-160 mg twice daily) may be reasonable when first-line agents fail—unlike flecainide/propafenone, it can be used in structural heart disease but requires monitoring for proarrhythmia. 1
• Dofetilide may be considered when beta-blockers, calcium channel blockers, flecainide, and propafenone are all ineffective or contraindicated. 1

Patient Education (Class I)

• All patients must be taught vagal maneuvers (modified Valsalva, carotid massage if appropriate, facial cooling) for self-management of SVT episodes—this may help avoid prolonged episodes and reduce need for emergency care. 1, 3
• Educate patients to perform maneuvers in supine position for maximum effectiveness. 1

Critical Clinical Pitfalls

• Never delay cardioversion in hemodynamically unstable patients to attempt vagal maneuvers or medications. 3
• Never use verapamil or diltiazem if there is any possibility of ventricular tachycardia or pre-excited atrial fibrillation (Wolff-Parkinson-White with AF)—this can cause ventricular fibrillation and death. 1, 3
• Never prescribe flecainide or propafenone to patients with any structural heart disease, ischemic heart disease, or left ventricular dysfunction—proarrhythmia risk is unacceptable in these populations. 1
• Always have resuscitation equipment ready before administering adenosine due to risk of brief asystole or precipitating rapid atrial fibrillation. 3
• Be prepared for immediate SVT recurrence after successful cardioversion or adenosine due to premature atrial/ventricular complexes triggering re-entry. 3
• Do not use digoxin for acute SVT termination—it has no role in acute management. 3

Comparative Effectiveness Context

While pharmacologic prophylaxis with AV nodal blockers shows moderate efficacy (reducing episode frequency in randomized trials), catheter ablation remains superior because it offers potential cure rather than symptom reduction, eliminates medication side effects and costs, and achieves success in >94% of patients with minimal risk. 1, 2 The choice between ablation and chronic pharmacotherapy should be discussed with all patients, but ablation should be strongly recommended as first-line definitive therapy for recurrent symptomatic SVT. 1