What are the management options for Atrioventricular Nodal Reentrant Tachycardia (AVNRT)?

AVNRT Management

For acute AVNRT termination in hemodynamically stable patients, start with vagal maneuvers (particularly the modified Valsalva technique), followed by adenosine 6 mg IV rapid push if vagal maneuvers fail, then IV calcium channel blockers (diltiazem or verapamil) or beta-blockers as third-line, with catheter ablation of the slow pathway as the definitive long-term solution. 1, 2, 3

Acute Management Algorithm

First-Line: Vagal Maneuvers

• Perform vagal maneuvers with the patient in the supine position as the initial intervention 4, 1, 2
• The modified Valsalva maneuver is 2.8-3.8 times more effective than the standard technique 2, 3
• Have the patient bear down against a closed glottis for 10-30 seconds, generating intrathoracic pressure of at least 30-40 mmHg 4, 2
• Carotid sinus massage is an alternative but less effective option; apply steady pressure over the carotid sinus for 5-10 seconds after confirming absence of bruits by auscultation 4, 2
• Overall success rate of vagal maneuvers is approximately 27.7%, with Valsalva being more successful than carotid massage 4

Second-Line: Adenosine

• Administer adenosine 6 mg as a rapid IV push through a large vein, followed immediately by saline flush 2, 3
• Adenosine terminates AVNRT in approximately 90-95% of patients 4, 3
• Have cardioversion equipment ready during administration due to potential for transient arrhythmias 3, 5
• Adenosine works by inhibiting calcium influx through slow channels in the AV node, interrupting the reentrant circuit 4, 5

Critical Safety Point: Ensure the rhythm is truly AVNRT before administering adenosine or calcium channel blockers, as these agents can be dangerous in ventricular tachycardia or pre-excited atrial fibrillation 1, 2

Third-Line: IV Calcium Channel Blockers or Beta-Blockers

• IV diltiazem or verapamil achieve 80-98% success rates in resistant cases 2, 3
• Verapamil works by inhibiting calcium influx through slow channels, slowing AV conduction and prolonging the effective refractory period within the AV node 6
• Administer verapamil 5-10 mg IV, which produces peak therapeutic effects within 3-5 minutes 6
• Beta-blockers (esmolol, metoprolol) are less effective than calcium channel blockers but have an excellent safety profile 3
• Avoid calcium channel blockers in patients with severe conduction abnormalities, sinus node dysfunction, or acute decompensated heart failure 4, 6

Hemodynamically Unstable Patients

• Perform immediate synchronized cardioversion using 50-100J initial energy 1, 2

Long-Term Management Options

Definitive Therapy: Catheter Ablation

• Catheter ablation of the slow pathway is the first-line definitive treatment with a success rate of 94.3-98.5% 1, 3
• Slow pathway ablation is preferred over fast pathway ablation due to lower risk of AV block 3
• Ablation is potentially curative and eliminates the need for chronic pharmacological therapy 3
• Radiofrequency energy is applied at sites showing discrete slow potentials in the perinodal region 7

Pharmacological Prophylaxis (For Patients Not Pursuing Ablation)

• Oral verapamil or diltiazem are first-line pharmacological options 1, 3
• Oral beta-blockers are effective alternatives 1
• Other options include digitalis and class Ia, Ic, and III antiarrhythmic agents 8
• Avoid beta-blockers in patients with severe conduction abnormalities or sinus node dysfunction 1

Important Clinical Considerations

Transition to Maintenance Therapy

• Transition to oral antiarrhythmic agents is generally safe within 3 hours after acute treatment 9
• Options include oral digoxin, calcium channel blockers, beta-blockers, or class I antiarrhythmics 9

Common Pitfalls to Avoid

• Never administer verapamil or diltiazem to patients with pre-excited atrial fibrillation—these patients require immediate cardioversion 2
• Do not use calcium channel blockers in patients with severe heart failure (pulmonary wedge pressure >20 mmHg, ejection fraction <30%) as acute worsening may occur 6
• Avoid applying pressure to the eyeball as a vagal maneuver—this practice is potentially dangerous and has been abandoned 4

Post-Conversion Management

• Atrial or ventricular premature complexes may occur immediately after conversion 2
• An antiarrhythmic drug may be required to prevent acute reinitiation 2