What is the medical management of paroxysmal supraventricular tachycardia (PSVT)?

Medical Management of Paroxysmal Supraventricular Tachycardia (PSVT)

For acute PSVT management, initiate vagal maneuvers immediately, followed by adenosine 6 mg IV rapid push if vagal maneuvers fail, and proceed to synchronized cardioversion for hemodynamically unstable patients. 1, 2

Acute Management Algorithm

Step 1: Initial Assessment and Hemodynamic Stability

• Hemodynamically unstable patients (hypotension, altered mental status, chest pain with ischemia, acute heart failure) require immediate synchronized cardioversion at 50-100 J biphasic, increasing stepwise if initial shock fails 1, 2
• Hemodynamically stable patients proceed with sequential pharmacologic interventions 1

Step 2: First-Line Acute Treatment (Stable Patients)

Vagal Maneuvers (Class I Recommendation):

• Perform Valsalva maneuver with patient supine: bear down against closed glottis for 10-30 seconds (equivalent to 30-40 mm Hg intrathoracic pressure) 1
• Modified Valsalva technique achieves 43% conversion rate 3
• Alternative: carotid sinus massage for 5-10 seconds after confirming absence of carotid bruit (safer in younger patients) 1
• Ice-cold wet towel to face (diving reflex) is another effective option 1
• Overall vagal maneuver success rate is approximately 25-28% 1, 2
• Critical pitfall: Avoid eyeball pressure—this technique is dangerous and abandoned 1

Adenosine (Class I Recommendation):

• Initial dose: 6 mg IV rapid push through large vein, followed immediately by 20 mL saline flush 2, 4
• If no conversion: 12 mg IV rapid push, may repeat 12 mg dose once more 2
• Achieves 90-95% conversion rate 1, 3
• Major contraindications: Second- or third-degree AV block, sick sinus syndrome, severe bronchospastic lung disease (asthma), known hypersensitivity 4
• Critical warnings:
  • May precipitate atrial fibrillation in 1-15% of patients 2
  • In patients with accessory pathways (WPW), adenosine-induced AF can lead to rapid ventricular conduction and ventricular fibrillation—have cardioversion immediately available 1, 4
  • Avoid in severe asthma due to bronchoconstriction risk 2, 4
  • Monitor for premature atrial/ventricular complexes post-conversion that may reinitiate tachycardia 1, 2

Step 3: Second-Line Acute Treatment (If Adenosine Fails or Contraindicated)

Calcium Channel Blockers:

• IV diltiazem or verapamil are highly effective alternatives for hemodynamically stable patients 2, 5
• Verapamil demonstrates 86% conversion rate in adenosine-refractory cases 6
• Absolute contraindication: Wolff-Parkinson-White syndrome with pre-excitation or pre-excited atrial fibrillation—can cause life-threatening rapid ventricular conduction 2, 7
• Major warnings:
  • Avoid in severe left ventricular dysfunction (ejection fraction <30%) or moderate-to-severe heart failure 7
  • Can cause significant hypotension and bradycardia 7, 8
  • Never combine IV calcium channel blockers with IV beta blockers—potentiates severe hypotension and bradycardia 2

Beta Blockers:

• Reasonable alternative for acute treatment in stable patients, though less effective than diltiazem 2
• Same contraindication applies for WPW with pre-excitation 2

Step 4: Refractory Cases

• Synchronized cardioversion for stable patients when pharmacologic therapy fails or is contraindicated 1
• Requires adequate sedation/anesthesia in stable patients 1

Special Population: Wolff-Parkinson-White Syndrome

Pre-excited Atrial Fibrillation (Medical Emergency):

• Hemodynamically unstable: Immediate synchronized cardioversion 1, 2
• Hemodynamically stable: IV procainamide or ibutilide (Class I recommendation) 1, 2
• Absolutely avoid: Adenosine, beta blockers, calcium channel blockers, and digoxin—all can accelerate conduction down accessory pathway, causing ventricular fibrillation 2

Long-Term Management

Definitive Treatment

Catheter Ablation (First-Line for Recurrent Symptomatic PSVT):

• Achieves 94.3-98.5% single-procedure success rate with low complication rates 2, 3
• Recommended as first-line therapy for patients desiring freedom from recurrent episodes and medications 1, 2
• Electrophysiologic study with ablation provides both diagnosis and definitive cure 2

Pharmacologic Prevention (Second-Line)

First-line oral agents (without pre-excitation):

• Oral beta blockers, diltiazem, or verapamil 2
• Use only after confirming absence of WPW/pre-excitation 2

Second-line oral agents (no structural/ischemic heart disease):

• Flecainide or propafenone 2
• Contraindicated in structural heart disease or coronary artery disease 2

Patient Education and Self-Management

• Teach proper vagal maneuver technique for self-termination of episodes 2
• Educate on when to seek emergency care (prolonged episodes, hemodynamic instability, new symptoms) 1

Common Clinical Pitfalls

1. Age-related considerations: Vagal maneuvers carry higher risk in elderly patients (>65 years) with potential cerebrovascular disease—consider proceeding directly to verapamil 6

2. Methylxanthine interference: Caffeine, aminophylline, and theophylline antagonize adenosine effects—may require higher doses or alternative agents 2, 4

3. Dipyridamole potentiation: Nucleoside transport inhibitors significantly increase adenosine activity—reduce adenosine dose 4

4. Post-conversion monitoring: Watch for premature complexes that may trigger recurrence; antiarrhythmic drugs may be needed to prevent immediate reinitiation 1, 2

5. Misdiagnosis risk: Always obtain 12-lead ECG to confirm narrow complex tachycardia—ventricular tachycardia can masquerade as PSVT on single-lead monitoring 9