What is the treatment for atrioventricular nodal reentrant tachycardia (AVNRT)?

Treatment for AVNRT

For acute treatment of hemodynamically stable AVNRT, start with vagal maneuvers (particularly the modified Valsalva technique), immediately followed by IV adenosine if unsuccessful, then proceed to IV calcium channel blockers (diltiazem or verapamil) or beta-blockers as third-line agents. 1

Acute Management Algorithm

First-Line: Vagal Maneuvers (Class I Recommendation)

• Perform vagal maneuvers immediately as the initial intervention with the patient in the supine position 1
• The modified Valsalva maneuver is 2.8-3.8 times more effective than standard technique: have the patient bear down against a closed glottis for 10-30 seconds, generating at least 30-40 mmHg of intrathoracic pressure 2, 1
• 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 carotid bruits 1, 2
• Success rate is approximately 28% when switching between different vagal techniques 1

Second-Line: IV Adenosine (Class I Recommendation)

• Adenosine is the definitive pharmacologic agent if vagal maneuvers fail, with a 95% success rate in terminating AVNRT 1
• Standard dosing per FDA labeling: initial dose of 6 mg rapid IV push, followed by 12 mg if needed 3
• Critical safety consideration: Ensure the rhythm is truly AVNRT before administration, as adenosine can be dangerous in ventricular tachycardia or pre-excited atrial fibrillation 4, 3
• Common transient side effects include flushing, chest discomfort, and dyspnea, which resolve within seconds 3, 5

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

• IV diltiazem or verapamil are equally effective as adenosine (>90% conversion rate) but with fewer adverse effects 1, 5
• These agents should only be used in hemodynamically stable patients after confirming absence of VT or pre-excited AF 1, 4
• Avoid in patients with suspected systolic heart failure or severe left ventricular dysfunction (ejection fraction <30%) 6
• IV beta-blockers have an excellent safety profile but are less effective than calcium channel blockers for acute termination 1

Fourth-Line: IV Amiodarone (Class IIb Recommendation)

• Consider only when other therapies are ineffective or contraindicated 1
• Limited evidence base but demonstrated effectiveness in small studies 1

Hemodynamically Unstable Patients

• Immediate synchronized cardioversion is mandatory (Class I recommendation) when the patient is hemodynamically unstable and vagal maneuvers/adenosine fail or are not feasible 1
• Cardioversion is highly effective and safe for terminating AVNRT 1

Long-Term Management

Definitive Treatment: Catheter Ablation (Class I Recommendation)

• Catheter ablation of the slow pathway is the first-line definitive treatment for recurrent symptomatic AVNRT 1, 4
• This has become the preferred therapy due to high success rates and low complication risk 7, 8
• Slow pathway ablation is preferred over fast pathway ablation due to lower risk of AV block 8

Pharmacologic Maintenance Options (for patients declining ablation)

First-line oral agents (Class I recommendations):

• Oral verapamil or diltiazem 1, 4
• Oral beta-blockers 1, 4

Second-line oral agents (Class IIa recommendations):

• Flecainide or propafenone in patients without structural heart disease or ischemic heart disease when first-line agents are ineffective or contraindicated 1

Third-line options (Class IIb recommendations):

• Oral sotalol or dofetilide 1
• Oral digoxin or amiodarone 1
• "Pill-in-the-pocket" approach with oral beta-blockers, diltiazem, or verapamil for infrequent, well-tolerated episodes 1

Critical Safety Considerations

Contraindications and Cautions

• Never use calcium channel blockers or adenosine if ventricular tachycardia or pre-excited atrial fibrillation cannot be excluded, as this can precipitate ventricular fibrillation 4, 6
• Avoid beta-blockers in patients with severe conduction abnormalities or sinus node dysfunction 1, 4
• Adenosine can cause transient AV block (6% incidence), bronchoconstriction, and rarely seizures 3
• Calcium channel blockers carry risk of hypotension and should be avoided in severe left ventricular dysfunction 6

Drug Interactions

• Methylxanthines (caffeine, theophylline, aminophylline) interfere with adenosine activity and may increase seizure risk 3
• Dipyridamole potentiates adenosine effects 3

Clinical Context

• AVNRT is the most common form of SVT, typically occurring in young adults without structural heart disease, with >60% of cases in women 1, 4
• Heart rates typically range from 180-200 bpm but can vary from 110 to >250 bpm 1, 4
• The arrhythmia is rarely life-threatening and often well-tolerated, though patients may experience palpitations, dyspnea, dizziness, and characteristic neck pulsations 1, 4