PSVT (Paroxysmal Supraventricular Tachycardia) - Treatment

Treatment Algorithm (Hemodynamically Stable)

Figure 256-6 from Harrison's Principles of Internal Medicine 22E (2025)

Step 1 - Assess Hemodynamic Status

Step 2 - Vagal Maneuvers (Stable patients, first-line)

• Valsalva maneuver - most commonly used; teach patient to self-administer for future episodes
• Carotid sinus massage - reasonable if no carotid bruits and no prior stroke history
• Modified Valsalva (recumbent + leg elevation) - higher conversion rates per recent meta-analysis (PMID: 38235710)
• If effective, record the ECG response - AV block with transient slowing may expose ongoing P waves, revealing AT or atrial flutter as the underlying mechanism

Step 3 - Adenosine (First-line pharmacologic)

• Dose: 6 mg rapid IV bolus through a large-bore IV, followed immediately by NS flush
• If no effect: repeat with 12 mg IV bolus
• Mechanism: transiently blocks AV nodal conduction, terminating the vast majority of PSVT episodes
• Half-life: < 10 seconds (ultra-short acting)

• Transient chest pain, dyspnea, anxiety
• Precipitates AF in up to 15% of patients - use cautiously in WPW (preexcited AF can be hemodynamically catastrophic)
• Contraindicated after cardiac transplantation (hypersensitivity from surgical sympathetic denervation)
• Can theoretically aggravate bronchospasm (use with caution in severe asthma)

Step 4 - Non-DHP CCB or Beta-Blocker (If adenosine fails)

Step 5 - Wide-Complex Tachycardia Special Considerations

• Treat as ventricular tachycardia until proven otherwise
• If regular and patient is stable: a trial of IV adenosine is reasonable
• Very irregular wide-complex tachycardia = likely preexcited AF/flutter - treat with cardioversion, IV procainamide, or ibutilide (NOT adenosine or AV-nodal blockers if WPW)
• If PSVT with aberrancy is unequivocal (prior documented episodes): treat with vagal maneuvers + adenosine

Long-Term / Preventive Management

Pharmacologic Options (for recurrent AVNRT)

• Class Ic agents (flecainide, propafenone) are well-studied and effective but rarely used now given the curative nature of catheter ablation
• Amiodarone/sotalol reserved for patients who are not ablation candidates

Catheter Ablation (Preferred for recurrent PSVT)

• Indications (Class I): Poorly tolerated AVNRT with hemodynamic compromise; recurrent symptomatic AVNRT where patient prefers ablation over drugs
• Success rate: >95% with the posterior (slow-pathway) approach
• Recurrence after ablation: ~3%
• Main complication: AV block (~0.5-1%)
• Cryoablation vs. radiofrequency (RF): Cryo has lower AV block risk but longer procedure times and lower long-term efficacy; RF remains dominant in adults. Cryo preferred by many pediatric electrophysiologists.
• Catheter ablation is considered first-line for recurrent PSVT in most patients given >95% efficacy and low complication rate

Decision Framework for Long-Term Treatment

Key Pearls

1. Monitor ECG continuously throughout acute management - the response to vagal maneuvers or adenosine can establish the mechanism
2. Don't use verapamil/diltiazem in WPW with wide-complex tachycardia - AV-nodal blockade can accelerate conduction via the accessory pathway
3. PSVT is not life-threatening in structurally normal hearts; treatment decisions are quality-of-life driven
4. Patients can be taught self-management (Valsalva or oral "pill-in-pocket" CCB/beta-blocker)
5. Most patients with recurrent episodes are candidates for catheter ablation as definitive cure

Verapamil Dosage for PSVT Prophylaxis

Oral Dosing (Prophylaxis / Long-Term Prevention)

Immediate-Release (IR) Tablets (40, 80, 120 mg)

Sustained/Extended-Release (SR/ER) Formulations (Calan SR, Verelan, Verelan PM)

• Typical starting SR dose: 120-180 mg once daily, titrate up as needed
• Maximum daily dose: 480 mg/day (400 mg/day for Verelan PM)
• SR/ER formulations are preferred for long-term prophylaxis due to better tolerability and once- or twice-daily dosing convenience

Note: Due to significant first-pass hepatic metabolism, oral verapamil prolongs the PR interval less than IV verapamil at equivalent concentrations. Dose-to-effect response must be assessed individually.

IV Dosing (Acute Termination - for reference)

Contraindications

• WPW syndrome / accessory bypass tract with AF or atrial flutter - can accelerate antegrade conduction via accessory pathway, potentially causing VF
• Sick sinus syndrome or 2nd/3rd degree AV block (without pacemaker)
• Severe LV dysfunction / cardiogenic shock (SBP < 90 mmHg)
• Congestive heart failure - use with caution due to negative inotropic effects
• Known hypersensitivity
• Infants and neonates - IV verapamil is avoided due to risk of apnea, bradycardia, and hypotension

Key Clinical Points

1. Oral verapamil for prophylaxis is classified as Class IIa (reasonable) for recurrent symptomatic AVNRT - Fuster & Hurst's The Heart, 15th Ed.
2. It is generally considered second-line to catheter ablation for recurrent, symptomatic PSVT given ablation's >95% cure rate
3. "Pill-in-pocket" strategy: Patients can also take a single oral dose (e.g., 80-120 mg IR) at the onset of a PSVT episode, combined with a Valsalva maneuver, to terminate and prevent early recurrence
4. Drug interactions: Verapamil inhibits CYP3A4 and P-glycoprotein - raises digoxin levels (monitor), interacts with beta-blockers (additive AV block and negative inotropy), statins, cyclosporine, and many others
5. Common side effects: Constipation (most frequent with oral use), hypotension, dizziness, headache, peripheral edema, bradycardia
6. Pretreat with calcium gluconate 1 g IV before IV verapamil in hypotensive patients to reduce hypotension without compromising antiarrhythmic effect