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

Management of Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

For acute AVNRT, start with vagal maneuvers in the supine position, followed immediately by adenosine 6 mg IV push if unsuccessful, then proceed to IV diltiazem or verapamil if adenosine fails—this stepwise approach terminates >95% of episodes without cardioversion. 1

Acute Management Algorithm

First-Line: Vagal Maneuvers

• Perform Valsalva maneuver with the patient supine: have the patient bear down against a closed glottis for 10-30 seconds, generating at least 30-40 mmHg of intrathoracic pressure 1, 2
• The modified Valsalva technique (with passive leg raise immediately after strain) is 2.8-3.8 times more effective than standard Valsalva 3
• Alternative: apply ice-cold wet towel to face or perform carotid sinus massage for 5-10 seconds after confirming absence of carotid bruits 1, 3
• Valsalva is more successful than carotid massage, with combined success rate of 27.7% 1

Second-Line: Adenosine

• Administer adenosine 6 mg rapid IV push through large vein, followed immediately by saline flush 1, 3
• Terminates AVNRT in approximately 95% of cases 1
• Can give 12 mg if 6 mg fails 1
• Keep cardioversion equipment ready due to brief side effects (flushing, chest discomfort, dyspnea) 3, 4

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

• IV diltiazem or verapamil are reasonable alternatives with 80-98% success rates in hemodynamically stable patients 1, 3
• IV metoprolol is less effective than diltiazem but has excellent safety profile 1
• Critical safety point: Ensure rhythm is truly AVNRT before giving verapamil/diltiazem—these agents are dangerous in ventricular tachycardia or pre-excited atrial fibrillation and can precipitate ventricular fibrillation 1, 2, 5
• Avoid calcium channel blockers in patients with severe left ventricular dysfunction (ejection fraction <30%), decompensated heart failure, or concurrent beta-blocker use 5

Fourth-Line: Cardioversion

• Immediate synchronized cardioversion (50-100J) is mandatory for hemodynamically unstable patients when vagal maneuvers and adenosine fail or are not feasible 1, 2
• Also indicated for stable patients when pharmacological therapy fails or is contraindicated 1

Rarely Used: IV Amiodarone

• May be considered when other therapies are ineffective or contraindicated in stable patients 1
• Limited evidence base for this indication 1

Long-Term Management Algorithm

First-Line: Catheter Ablation

• Radiofrequency catheter ablation of the slow pathway is the definitive treatment (Class I recommendation) 1, 2, 6, 7
• Success rate >95% with low complication risk 6
• Has become first-choice therapy due to high efficacy and safety profile 6, 7

Pharmacological Alternatives (for patients declining ablation)

Tier 1 Options:

• Oral verapamil or diltiazem (Class I recommendation) 1, 2
• Oral beta-blockers (Class I recommendation) 1, 2
• These are recommended as first-line medical therapy 1

Tier 2 Options (when Tier 1 fails or contraindicated):

• Flecainide or propafenone for patients without structural heart disease or ischemic heart disease (Class IIa recommendation) 1
• These class IC agents are only appropriate after excluding structural heart disease 1

Tier 3 Options:

• Oral sotalol or dofetilide may be reasonable but have lower evidence quality 1

Observation Without Treatment

• Clinical follow-up without pharmacological therapy or ablation is reasonable for minimally symptomatic patients 1, 2

Critical Safety Considerations

Diagnostic Confirmation

• Always confirm the rhythm is AVNRT before treatment—look for absent P waves or discrete P waves immediately after QRS, or rSr' pattern in V1 6
• AVNRT typically presents with heart rate 180-200 bpm (range 110-250 bpm) and sudden onset of palpitations described as "pounding in the neck" 1, 2, 6

Contraindications to Calcium Channel Blockers

• Never use verapamil/diltiazem in:
  • Pre-excited atrial fibrillation (Wolff-Parkinson-White with AF)—can cause ventricular fibrillation 1, 5
  • Ventricular tachycardia—can cause hemodynamic collapse 1, 2
  • Severe left ventricular dysfunction (EF <30%) 5
  • Concurrent beta-blocker therapy 5
  • Severe conduction abnormalities or sinus node dysfunction 1, 2

Monitoring Requirements

• Verapamil can cause first-degree AV block (correlated with plasma levels), bradycardia, and rarely higher-degree AV block 5
• Monitor liver enzymes periodically with chronic verapamil use due to risk of hepatocellular injury 5
• Watch for hypotension (2.5% incidence), though orthostatic hypotension is rare 5

Common Pitfalls

• Giving calcium channel blockers without ECG confirmation: This is the most dangerous error—always verify narrow-complex tachycardia without pre-excitation 1, 2
• Using beta-blockers as first-line acute therapy: They are less effective than adenosine or calcium channel blockers for acute termination 1, 4
• Performing vagal maneuvers with patient upright: Always position supine for maximum efficacy 1, 3
• Not having cardioversion equipment ready when giving adenosine: Brief but dramatic side effects can occur 3
• Avoiding treatment in pregnancy: AVNRT is the most common tachydysrhythmia in pregnancy; vagal maneuvers and adenosine remain first-line and are safe 4