What is the recommended treatment for paroxysmal supraventricular tachycardia?

Treatment of Paroxysmal Supraventricular Tachycardia (PSVT)

For hemodynamically stable PSVT, perform vagal maneuvers first, followed immediately by adenosine 6 mg IV push if unsuccessful; for hemodynamically unstable patients, proceed directly to synchronized cardioversion without attempting vagal maneuvers or medications. 1

Immediate Assessment: Hemodynamic Stability

Determine stability within seconds by assessing for hypotension, altered mental status, shock, chest pain, or acute heart failure. 1, 2

• Unstable patients: Perform synchronized cardioversion (50-100 J) immediately after sedation—this achieves near-100% termination and pharmacologic therapy must not delay definitive treatment. 1, 2
• Stable patients: Proceed with the stepwise algorithm below. 1, 3

Step 1: Vagal Maneuvers (First-Line for Stable Patients)

Attempt vagal maneuvers before any medication—they terminate 27-43% of PSVT episodes and carry minimal risk in younger patients. 1, 2, 4

Technique (Patient Must Be Supine)

• Modified Valsalva maneuver: Patient bears down against a closed glottis for 10-30 seconds, generating ≥30-40 mm Hg intrathoracic pressure—this is the most effective vagal technique. 1, 2
• Carotid sinus massage: Apply steady pressure over one carotid sinus for 5-10 seconds only after confirming absence of bruit by auscultation. 1, 3
• Ice-water facial immersion: Apply an ice-cold wet towel to the face to activate the diving reflex. 1, 3

Critical Safety Warning

Never apply pressure to the eyeball—this practice is dangerous and has been abandoned. 1, 2, 3

Age-Related Consideration

Vagal maneuvers are safest in younger patients; in patients >65 years with higher likelihood of coronary or cerebrovascular disease, consider proceeding directly to adenosine to minimize stroke risk from carotid massage. 5

Step 2: Adenosine (First-Line Pharmacologic Agent)

Adenosine terminates 90-95% of AVNRT and 78-96% of AVRT—it is the most effective first-line drug for stable PSVT. 1, 2, 4, 6

Dosing Protocol

• Initial dose: 6 mg rapid IV push over 1-2 seconds via a large proximal vein (antecubital preferred), followed immediately by 20 mL saline flush. 1, 2
• Second dose: If no conversion within 1-2 minutes, give 12 mg rapid IV push with flush. 1, 2
• Third dose: If still no response, give a final 12 mg dose (maximum cumulative dose 30 mg). 2
• Average time to termination: 30 seconds after an effective dose. 2

Dose Adjustments

• Reduce to 3 mg in patients taking dipyridamole or carbamazepine, cardiac transplant recipients, or when administering via central venous access. 1, 2
• Increase dose in patients with significant theophylline, caffeine, or theobromine levels (competitive adenosine antagonists). 1, 2

Absolute Contraindications to Adenosine

• Asthma or active bronchospasm (risk of severe bronchospasm). 1, 2
• Second- or third-degree AV block or sick sinus syndrome without pacemaker. 2
• Pre-excited atrial fibrillation (e.g., Wolff-Parkinson-White)—adenosine may precipitate rapid ventricular response; have defibrillator immediately available if WPW is suspected. 2

Common Transient Side Effects (<60 Seconds)

Flushing, dyspnea, chest discomfort, and transient AV block are common but self-limited. 2, 6

Special Population: Pregnancy

Adenosine is safe and effective during pregnancy. 1, 2

Step 3: Calcium-Channel Blockers (Second-Line)

If adenosine fails or is contraindicated (e.g., asthma), intravenous diltiazem is the preferred alternative, achieving 64-98% conversion. 1, 2, 7, 4

Diltiazem Dosing

• 15-20 mg (≈0.25 mg/kg) IV over 2 minutes; clinical effect typically within 3-5 minutes. 1, 2, 7
• A slower infusion over up to 20 minutes reduces hypotension risk. 2

Verapamil Alternative

• 2.5-5 mg IV over 2 minutes; effect within 3-5 minutes. 1, 2

Absolute Contraindications to Calcium-Channel Blockers

Do NOT administer diltiazem or verapamil if any of the following are present: 1, 2, 3, 7

1. Ventricular tachycardia cannot be excluded (may cause hemodynamic collapse)
2. Pre-excited atrial fibrillation (e.g., WPW)—may precipitate ventricular fibrillation
3. Suspected systolic heart failure or severe LV dysfunction (negative inotropic effects)
4. Hemodynamic instability

Step 4: Intravenous Beta-Blockers (Third-Line)

Beta-blockers are reasonable alternatives with excellent safety profiles, though slightly less effective than calcium-channel blockers. 1, 2

Metoprolol Dosing

• 2.5-5 mg IV every 2-5 minutes; maximum cumulative dose 15 mg over 10-15 minutes. 1, 2

Esmolol Alternative

Useful for short-term rate control, particularly when concurrent hypertension is present. 1, 2

Caution

Use carefully in severe COPD; never combine IV calcium-channel blockers with IV beta-blockers due to synergistic hypotension and bradycardia. 2

Step 5: Synchronized Cardioversion (Last Resort for Stable Patients)

If all pharmacologic options fail or are contraindicated, synchronized cardioversion achieves 80-100% termination with appropriate sedation. 1, 2, 3

Post-Conversion Management

Immediate Monitoring

Maintain continuous ECG monitoring because premature atrial or ventricular complexes commonly trigger recurrent PSVT within seconds to minutes. 2

Management of Immediate Recurrence

• Administer a longer-acting AV-nodal blocker (oral diltiazem, verapamil, or beta-blocker) to prevent reinitiation. 1, 2
• Consider "pill-in-the-pocket" therapy for patient self-management of future episodes. 2

Long-Term Prevention

Catheter ablation is first-line therapy for preventing recurrent PSVT, with single-procedure success rates of 94.3-98.5% and superior cost-effectiveness compared to chronic pharmacotherapy. 2, 3, 4

• Oral beta-blockers, diltiazem, or verapamil are reasonable alternatives for patients who decline or are not candidates for ablation. 1, 3
• Flecainide or propafenone may be considered in patients without structural heart disease who are not ablation candidates. 3

Patient Education

Teach vagal maneuver techniques (modified Valsalva, ice-water facial immersion) for self-termination of future episodes. 2, 3

Special Scenario: Pre-Excited Atrial Fibrillation (Wolff-Parkinson-White)

If PSVT converts to atrial fibrillation with pre-excitation (wide, irregular QRS): 1, 2, 3

• Avoid adenosine, diltiazem, verapamil, beta-blockers, and digoxin—these enhance accessory-pathway conduction and may precipitate ventricular fibrillation.
• Unstable: Immediate synchronized cardioversion.
• Stable: IV procainamide or ibutilide to slow accessory-pathway conduction.

Critical Pitfalls to Avoid

• Do not delay cardioversion in unstable patients to attempt drug therapy. 1, 2
• Do not give calcium-channel blockers when VT or pre-excited AF cannot be excluded. 1, 2, 3
• Do not use adenosine in asthma due to severe bronchospasm risk. 1, 2
• Do not apply eyeball pressure during vagal maneuvers. 1, 2, 3
• Do not combine IV calcium-channel blockers with IV beta-blockers. 2
• Obtain a 12-lead ECG during tachycardia to exclude VT and identify pre-excitation before administering AV-nodal blockers. 1, 2