What is the standard treatment for Paroxysmal Supraventricular Tachycardia (PSVT)?

Standard Treatment for Paroxysmal Supraventricular Tachycardia (PSVT)

Begin with vagal maneuvers immediately in all hemodynamically stable patients, followed by IV adenosine 6 mg rapid push if vagal maneuvers fail, and proceed to synchronized cardioversion for hemodynamically unstable patients or those who fail pharmacologic therapy. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• Hemodynamically unstable patients require immediate synchronized cardioversion at 50-100 J biphasic energy without attempting vagal maneuvers or medications 1, 2
• Unstable signs include hypotension, altered mental status, chest pain suggesting ischemia, or acute heart failure 1

Step 2: Vagal Maneuvers (First-Line for Stable Patients)

• Perform vagal maneuvers as the initial intervention with Class I recommendation 1, 2
• The modified Valsalva maneuver is most effective (43% success rate): patient in supine position bears down against closed glottis for 10-30 seconds, generating 30-40 mmHg intrathoracic pressure 1, 3
• Carotid sinus massage: apply steady pressure over right or left carotid sinus for 5-10 seconds only after confirming absence of carotid bruit by auscultation 1
• Ice-cold wet towel to face (diving reflex) is an alternative vagal maneuver 1
• Switching between vagal maneuver techniques increases overall success to 27.7% 1
• Never apply pressure to the eyeball—this practice is dangerous and abandoned 1

Step 3: Adenosine (Second-Line)

• If vagal maneuvers fail, administer adenosine 6 mg IV rapid push through a large (antecubital) vein followed by 20 mL saline flush (Class I, LOE B) 1
• Adenosine terminates 90-95% of reentrant SVTs including AVNRT and orthodromic AVRT 1, 3
• If no conversion within 1-2 minutes, give 12 mg rapid IV push using same technique 1
• Have defibrillator immediately available due to risk of precipitating atrial fibrillation with rapid ventricular response, especially in patients with WPW 1, 4

Adenosine Dosing Adjustments:

• Reduce initial dose to 3 mg in patients taking dipyridamole or carbamazepine, those with transplanted hearts, or if given by central venous access 1
• Larger doses may be required for patients with significant theophylline, caffeine, or theobromine levels 1, 4
• Do not use in patients with asthma due to risk of bronchoconstriction 1, 4
• Adenosine is safe and effective in pregnancy 1

Common Transient Side Effects:

• Flushing, dyspnea, and chest discomfort are most frequent but transient 1, 4

Step 4: Longer-Acting AV Nodal Blockers (Third-Line)

• If adenosine fails or SVT recurs, use calcium channel blockers or beta-blockers (Class IIa, LOE B) 1
• Intravenous diltiazem or verapamil are particularly effective for converting AVNRT to sinus rhythm 1
• Intravenous beta-blockers are less effective than calcium channel blockers but reasonable alternatives 1
• These agents provide sustained rhythm control and are useful when adenosine unmasks atrial fibrillation or flutter requiring rate control 1, 2

Step 5: Synchronized Cardioversion (Refractory Cases)

• Synchronized cardioversion is recommended for hemodynamically stable patients when pharmacologic therapy fails or is contraindicated (Class I, LOE B-NR) 1, 2
• Initial energy: 50-100 J biphasic for SVT 2

Critical Pitfalls to Avoid

Wide-Complex Tachycardia

• Never administer verapamil or diltiazem for wide-complex tachycardia until VT is definitively excluded—this can cause hemodynamic collapse or ventricular fibrillation 2, 5
• Adenosine is safer in wide-complex tachycardia of uncertain etiology 6

Pre-Excited Atrial Fibrillation (WPW)

• Do not use AV nodal blockers (verapamil, diltiazem, beta-blockers, adenosine) in pre-excited atrial fibrillation—they may accelerate ventricular rate and cause ventricular fibrillation 2, 5
• Use procainamide or ibutilide instead, or proceed directly to cardioversion (Class I recommendation) 2, 5

Contraindications to Calcium Channel Blockers/Beta-Blockers

• Avoid in suspected systolic heart failure 1
• Avoid in patients with severe conduction abnormalities or sinus node dysfunction 1
• Avoid in suspected pre-excitation syndromes 5

Special Considerations

Automatic Tachycardias

• Ectopic atrial tachycardia, multifocal atrial tachycardia, and junctional tachycardia have gradual onset and termination (not abrupt like reentrant SVTs) 1, 2
• These arrhythmias are not responsive to cardioversion 1, 2
• Treat with AV nodal blocking agents for rate control, not rhythm termination 1, 2

Recurrent Episodes

• Treat recurrences with adenosine or longer-acting AV nodal blocking agents (diltiazem or beta-blocker) 1, 2
• Monitor for recurrence after initial conversion 1

Long-Term Management Considerations

• Catheter ablation is first-line definitive therapy with single-procedure success rates of 94.3-98.5% 3
• Oral beta-blockers, diltiazem, or verapamil are reasonable for ongoing management in patients with recurrent symptomatic SVT without ventricular pre-excitation 5
• Educate patients on proper vagal maneuver techniques for self-management of future episodes 5