What is the management of Atrioventricular Nodal Reentrant Tachycardia (AVNRT)?

Management of Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

Vagal maneuvers should be performed first in all hemodynamically stable AVNRT patients, followed immediately by adenosine 6 mg IV rapid push if vagal maneuvers fail, achieving termination in approximately 95% of cases. 1, 2

Acute Management Algorithm

First-Line: Vagal Maneuvers (Class I Recommendation)

• Position the patient supine before attempting any vagal maneuver 1, 3
• Modified Valsalva maneuver is the most effective technique, being 2.8-3.8 times more successful than standard Valsalva 4, 3
  • Patient bears down against closed glottis for 10-30 seconds, generating at least 30-40 mmHg intrathoracic pressure 1, 3
  • Overall success rate is approximately 27.7% when switching between techniques 1
• Carotid sinus massage is an alternative but less effective option 3
  • Must confirm absence of carotid bruit by auscultation before performing 1, 3
  • Apply steady pressure over right or left carotid sinus for 5-10 seconds 1
• Ice-cold wet towel applied to face (diving reflex) is another option 1

Second-Line: Adenosine (Class I Recommendation)

• Adenosine 6 mg IV rapid push through large vein, followed immediately by saline flush 3
• Terminates AVNRT in 90-95% of patients 1, 4, 5
• Have cardioversion equipment ready during administration 4
• Can give 9 mg or 12 mg if initial 6 mg dose fails 5
• Common side effects include flushing and chest discomfort, but these are short-lived 6

Third-Line: IV Calcium Channel Blockers or Beta-Blockers (Class IIa Recommendation)

• IV verapamil or diltiazem achieve 80-98% success rates 4, 3
• Verapamil initial dose: 0.075-0.1 mg/kg IV, can give subsequent 5 mg bolus to maximum 15-20 mg 5
• Administer over 20 minutes to minimize hypotension risk 6
• Equally as efficacious as adenosine but with fewer adverse effects 6
• Beta-blockers (esmolol, metoprolol) are less effective than calcium channel blockers but have excellent safety profile 4

Hemodynamically Unstable Patients

• Immediate synchronized cardioversion is recommended 1, 2
• Use 50-100J initial energy for SVT 3
• Perform when vagal maneuvers and adenosine fail or are not feasible 1

Critical Safety Considerations

Before Treatment

• Record 12-lead ECG to confirm narrow-complex tachycardia and exclude ventricular tachycardia or pre-excited atrial fibrillation 1, 2
• Never give verapamil or diltiazem if VT or pre-excited AF is suspected—this can cause hemodynamic collapse or ventricular fibrillation 1, 2, 7
• Verapamil may accelerate ventricular rate in patients with accessory pathways (Wolff-Parkinson-White), potentially causing ventricular fibrillation 7

Contraindications to Calcium Channel Blockers

• Severe left ventricular dysfunction (ejection fraction <30%) 7
• Moderate to severe heart failure symptoms 7
• Patients receiving beta-blockers concurrently 7
• Severe conduction abnormalities or sinus node dysfunction 1, 2
• Accessory bypass tracts with atrial fibrillation 7

Long-Term Management

Definitive Therapy: Catheter Ablation (Class I Recommendation)

• Slow pathway ablation is first-line definitive treatment with 94.3-98.5% success rate 4
• Eliminates need for chronic pharmacological therapy 4
• Minimal risk of AV block compared to fast pathway ablation 8
• Rapidly becoming therapy of first choice for symptomatic AVNRT requiring treatment 9, 8

Pharmacological Maintenance (Class I Recommendation)

• Oral verapamil or diltiazem are first-line pharmacological options for patients not pursuing ablation 2, 4
  • Success rate of 80-98% for preventing recurrences 4
  • Verapamil prolongs AV node effective refractory period and slows AV conduction 7
• Oral beta-blockers are alternative first-line options 2
• Digoxin alone or combined with beta-blockers is effective in approximately 50% of cases 5
• Class Ia, Ic, and III antiarrhythmic agents are additional options 8

Monitoring on Chronic Verapamil

• Periodic liver function monitoring is prudent 7
• Elevations in transaminases, alkaline phosphatase, and bilirubin have been reported 7
• Monitor for PR interval prolongation, which correlates with verapamil plasma levels 7
• Watch for first-degree AV block (0.8% incidence of higher-degree block) 7

Clinical Pearls

• AVNRT typically presents with sudden onset palpitations, often described as "pounding in the neck," with heart rates 180-200 bpm 2
• Syncope is rare 1, 2
• May be triggered by exertion, caffeine, tea, or alcohol 1, 2
• Atrial or ventricular premature complexes may occur immediately after conversion; an antiarrhythmic drug may be required to prevent acute reinitiation 3
• Most patients can be discharged with appropriate follow-up after successful conversion 6