What is the initial management for Paroxysmal Supraventricular Tachycardia (PSVT) versus Atrioventricular Nodal Reentrant Tachycardia (AVNRT)?

PSVT vs AVNRT: Initial Management

Key Distinction

AVNRT (Atrioventricular Nodal Reentrant Tachycardia) is actually the most common subtype of PSVT (Paroxysmal Supraventricular Tachycardia), accounting for the majority of cases—the initial management is identical for both because AVNRT represents approximately 60% of all PSVT presentations. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability First

If the patient is hemodynamically unstable (hypotension, altered mental status, signs of shock, chest pain, or acute heart failure), perform immediate synchronized cardioversion at 50-100 J biphasic energy. 3, 2, 4

Step 2: For Hemodynamically Stable Patients

Initiate vagal maneuvers immediately as first-line therapy with the patient in the supine position. 1, 3

• Modified Valsalva maneuver is most effective (43% success rate): Patient bears down against a closed glottis for 10-30 seconds, generating 30-40 mmHg intrathoracic pressure 3, 4
• Carotid sinus massage: Apply steady pressure over right or left carotid sinus for 5-10 seconds after confirming absence of bruit 1, 3
• Diving reflex: Apply ice-cold wet towel to face or facial immersion in 10°C water 1, 3
• Critical warning: Never apply pressure to eyeballs—this is dangerous and abandoned 1, 3
• Overall success rate when alternating vagal techniques is 27.7% 1, 3

Step 3: Adenosine as Second-Line

If vagal maneuvers fail, immediately administer adenosine 6 mg IV rapid push through a large vein, followed by 20 mL saline flush. 3, 4

• Adenosine terminates 90-95% of AVNRT and PSVT cases 1, 3, 5
• If no conversion within 1-2 minutes, give 12 mg IV rapid push 4
• Have defibrillator immediately available—adenosine can precipitate atrial fibrillation with rapid ventricular response 3, 4
• Side effects occur in 30% but are brief (<1 minute) 3
• Important caveat: Adenosine has marginal efficacy in critically ill surgical/trauma patients (only 44% initial success, 34% for relapses) 6

Step 4: Longer-Acting AV Nodal Blockers

If adenosine fails or PSVT/AVNRT recurs, use calcium channel blockers (verapamil 2.5-5 mg IV or diltiazem) or beta-blockers. 3, 4

• Success rates of 80-98% for conversion 3, 2
• Verapamil and diltiazem are equally effective as adenosine (>90% conversion) but without the unpleasant side effects 7
• When given over 20 minutes, risk of hypotension is low 7

Step 5: Synchronized Cardioversion

If pharmacologic therapy fails or is contraindicated, perform synchronized cardioversion. 1, 4

Critical Pitfalls to Avoid

Never administer verapamil or diltiazem for wide-complex tachycardia until ventricular tachycardia is definitively excluded—this can cause hemodynamic collapse or ventricular fibrillation. 2, 4

Never use AV nodal blocking agents in pre-excited atrial fibrillation (Wolff-Parkinson-White with AF)—this may accelerate ventricular rate and precipitate ventricular fibrillation. 1, 2, 4

• In pre-excited AF, use procainamide or proceed directly to cardioversion 4, 8

Long-Term Management

Catheter ablation of the slow pathway is the definitive first-line therapy for preventing recurrent symptomatic PSVT/AVNRT, with success rates of 94.3-98.5% and recurrence rates <5%. 3, 2, 5

• Ablation is potentially curative and eliminates need for chronic pharmacotherapy 3
• Should be considered in all patients with symptomatic episodes 3

For patients declining ablation or unsuitable candidates, oral beta-blockers, diltiazem, or verapamil are first-line pharmacologic options with 80-98% success rates. 3, 2

• Flecainide or propafenone are effective in patients without structural heart disease 2
• Given the high relapse rate (52% in critically ill patients), suppressive therapy during periods of maximal cardiovascular stress is essential 6