What is the recommended acute and chronic management of supraventricular tachycardia, including treatment for stable versus unstable patients, recurrent episodes, and pregnancy?

Management of Supraventricular Tachycardia

For hemodynamically unstable SVT, proceed immediately to synchronized cardioversion after sedation—this restores sinus rhythm in nearly 100% of cases; for stable patients, begin with vagal maneuvers (modified Valsalva first-line), followed by adenosine 6 mg IV push if unsuccessful, then IV diltiazem or verapamil if adenosine fails, and finally synchronized cardioversion if all pharmacologic therapy is ineffective. 1, 2, 3

Immediate Hemodynamic Assessment

Determine stability within the first 60 seconds of patient contact. Unstable features include: 1, 3

• Systolic blood pressure <90 mm Hg or symptomatic hypotension 1
• Altered mental status or loss of consciousness 1
• Signs of shock (cold extremities, delayed capillary refill, oliguria) 1
• Ischemic chest pain suggesting acute coronary syndrome 1
• Acute heart failure or pulmonary edema 1

Management of Hemodynamically Unstable SVT

Synchronized cardioversion is the only appropriate intervention—do not attempt vagal maneuvers or pharmacologic therapy. 1, 3

• Administer procedural sedation (e.g., midazolam, propofol) if the patient is conscious 3
• Deliver synchronized shock starting at 50–100 J 2
• Success rate approaches 100% for terminating SVT 1, 3
• Have defibrillation equipment and resuscitation drugs immediately available 1

Management of Hemodynamically Stable SVT

Step 1: Vagal Maneuvers (First-Line, Class I)

Modified Valsalva maneuver is the most effective vagal technique and should be attempted first. 1, 2, 4

Technique: 1, 2, 4

• Position patient supine 2, 4
• Instruct patient to bear down against a closed glottis for 10–30 seconds, generating ≥30–40 mm Hg intrathoracic pressure 1, 2
• Success rate: 43% for modified Valsalva 3, 4
• Modified technique is 2.8–3.8 times more effective than standard Valsalva 4

Alternative vagal maneuvers if modified Valsalva fails: 1, 2

• Carotid sinus massage: apply steady pressure over one carotid sinus for 5–10 seconds after confirming absence of bruit by auscultation 1, 2, 4
• Avoid in elderly patients or those with known carotid disease 3
• Facial cooling (diving reflex): apply ice-cold wet towel to face 1, 3

Overall success rate when rotating through different vagal maneuvers: 27.7% 1, 3

Critical safety warning: Never apply pressure to the eyeball—this technique has been abandoned due to danger. 1, 3

Step 2: Adenosine (First-Line Pharmacologic, Class I)

Adenosine terminates 90–95% of AVNRT and 78–96% of AVRT cases and is the drug of choice when vagal maneuvers fail. 1, 2, 3

Dosing protocol: 1, 2

• Initial dose: 6 mg rapid IV push (over 1–2 seconds) through the most proximal peripheral vein (antecubital preferred) 2
• Follow immediately with 20 mL saline flush 1, 2
• If no conversion within 1–2 minutes, give 12 mg rapid IV push with flush 1, 2
• May repeat 12 mg once more if needed 1, 2
• Maximum cumulative dose: 30 mg (6 + 12 + 12) 2
• Average time to termination: 30 seconds after effective dose 2

Dose adjustments: 2

• Reduce to 3 mg in patients taking dipyridamole or carbamazepine, cardiac transplant recipients, or when giving via central venous access 2
• Increase dose may be needed in patients with significant theophylline, caffeine, or theobromine levels 2

Absolute contraindications: 2

• Asthma or active bronchospasm (risk of severe bronchospasm) 2
• Second- or third-degree AV block or sick sinus syndrome without pacemaker 2
• Pre-excited atrial fibrillation (Wolff-Parkinson-White with AF) 2

Expected side effects (transient, <60 seconds): 2, 3

• Flushing (most common) 2
• Dyspnea 2
• Chest discomfort 2
• Occur in ~30% of patients 3

Critical safety requirement: Defibrillator must be immediately available because adenosine can precipitate rapid atrial fibrillation. 2, 3

Diagnostic value: Adenosine serves dual therapeutic-diagnostic role—if it fails to convert but reveals underlying atrial flutter or atrial tachycardia through transient AV block, shift management to rate control with longer-acting AV-nodal blocker. 1, 2

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

If adenosine fails or is contraindicated, IV diltiazem is the preferred alternative, achieving 64–98% conversion. 1, 2, 3

Diltiazem dosing: 2

• 15–20 mg (≈0.25 mg/kg) IV over 2 minutes 2
• Slow infusion over up to 20 minutes reduces hypotension risk 3

Verapamil alternative: 2

• 2.5–5 mg IV over 2 minutes 2
• Clinical effect typically within 3–5 minutes 2

IV beta-blockers (alternative when CCBs not tolerated): 1, 2

• Metoprolol: 2.5–5 mg IV every 2–5 minutes, maximum 15 mg over 10–15 minutes 2
• Esmolol: useful for short-term control, especially with concurrent hypertension 1
• Slightly less effective than calcium-channel blockers but excellent safety profile 1, 3

Absolute contraindications for calcium-channel blockers (verapamil/diltiazem): 1, 2, 3

• Ventricular tachycardia cannot be excluded (may cause hemodynamic collapse) 2
• Pre-excited atrial fibrillation (can enhance accessory pathway conduction and trigger ventricular fibrillation) 2, 3
• Suspected systolic heart failure (negative inotropic effects) 1, 2
• Hemodynamic instability 2

Do not combine IV calcium-channel blockers with IV beta-blockers due to synergistic hypotensive and bradycardic effects. 3

Step 4: Synchronized Cardioversion (Rescue for Refractory Stable SVT)

When all pharmacologic therapy fails or is contraindicated, perform elective synchronized cardioversion with appropriate sedation. 1, 3

• Success rate: 80–98% when combined with prior drug therapy 3
• Achieves near-100% termination of AVRT and AVNRT 1, 2
• Start with 50–100 J 2

Post-Conversion Management

Monitor continuously for immediate recurrence—premature atrial or ventricular complexes commonly trigger repeat SVT episodes within seconds to minutes. 2

If immediate recurrence occurs: 2

• Administer a longer-acting AV-nodal blocker (diltiazem or beta-blocker) to prevent reinitiation 2
• Consider prophylactic antiarrhythmic therapy in patients with frequent premature complexes post-conversion 2

Long-Term/Chronic Management

Catheter Ablation (First-Line Definitive Therapy, Class I)

Catheter ablation should be offered to all patients with symptomatic recurrent SVT—it is the most effective, safe, and cost-effective approach. 3, 4

• Single-procedure success rates: 94.3–98.5% 3, 5
• Particularly recommended for AVNRT due to very low risk of AV block 6
• Should be offered as first-line therapy for reentrant and focal arrhythmias 6

Oral Pharmacologic Therapy (For Patients Declining or Unsuitable for Ablation)

First-line oral agents (Class I): 3, 4

• Oral beta-blockers, diltiazem, or verapamil 1, 3, 4
• Preferred for patients without ventricular pre-excitation 4

Second-line oral agents (Class IIa): 3, 4

• Flecainide or propafenone 3, 4
• Only for patients without structural heart disease or ischemic heart disease 4
• Never use in patients with structural heart disease or coronary artery disease 4

Third-line oral agents (Class IIb): 1, 3, 4

• Sotalol or dofetilide 1, 3, 4
• Consider when first-line agents fail 3, 4

Patient Education

Teach all patients how to perform vagal maneuvers (modified Valsalva, carotid massage, facial cooling) for self-termination of future episodes. 3, 4

Consider "pill-in-the-pocket" therapy as a personalized self-directed intervention developed in partnership with the patient. 2

Special Populations

Pregnancy

Vagal maneuvers remain first-line therapy. 4

Adenosine is safe and effective during pregnancy and is the first-line pharmacologic agent. 1, 2, 4

Synchronized cardioversion is safe at all stages of pregnancy when pharmacologic therapy fails: 4

• Apply electrode pads away from the uterus 4
• Perform fetal monitoring if time allows 4

Avoid antiarrhythmic medications, especially in the first trimester. 1, 6

Adult Congenital Heart Disease (ACHD)

Acute antithrombotic therapy is recommended for atrial tachycardia or atrial flutter, following atrial fibrillation guidelines. 1

IV adenosine is appropriate for SVT termination. 1

IV diltiazem or esmolol may be used cautiously, monitoring for hypotension. 1

Flecainide should not be administered in patients with significant ventricular dysfunction. 1

Synchronized cardioversion is recommended for hemodynamically unstable ACHD patients with SVT. 1

Critical Diagnostic Considerations

Obtain a 12-lead ECG during tachycardia whenever possible to: 4

• Differentiate SVT mechanisms 4
• Exclude ventricular tachycardia 2
• Exclude pre-excited atrial fibrillation 2
• Guide long-term management 4

If diagnosis remains uncertain after acute management, refer to cardiology for electrophysiologic study—this provides both diagnosis and definitive treatment option. 4