AVNRT Management
For acute AVNRT termination in hemodynamically stable patients, begin with vagal maneuvers (particularly the modified Valsalva technique) followed immediately by adenosine 6 mg IV rapid push if unsuccessful, achieving a combined success rate exceeding 95%. 1, 2
Acute Treatment Algorithm
Hemodynamically Stable Patients
First-line: Vagal Maneuvers
- Perform modified Valsalva maneuver with patient supine: bear down against closed glottis for 10-30 seconds generating 30-40 mmHg intrathoracic pressure 1, 3
- Modified Valsalva is 2.8-3.8 times more effective than standard technique 2, 3
- Alternative: carotid sinus massage for 5-10 seconds after confirming absence of carotid bruit 1, 3
- Overall vagal maneuver success rate is approximately 27.7%, but switching between techniques improves outcomes 1
Second-line: Adenosine
- Administer 6 mg IV rapid push through large vein followed by saline flush 1, 4
- Terminates AVNRT in approximately 95% of cases 1, 2, 5
- Have cardioversion equipment immediately available due to risk of cardiac arrest, ventricular arrhythmias, and myocardial infarction 4
- Critical warning: Adenosine can cause first-, second-, or third-degree AV block (occurs in ~6% of patients), bronchoconstriction, severe hypotension, and seizures 4
Third-line: IV Calcium Channel Blockers or Beta-Blockers
- IV diltiazem or verapamil achieve 80-98% success rates and are equally effective as adenosine but with fewer adverse effects 1, 2, 6
- Administer over 20 minutes to minimize hypotension risk 6
- Critical warning: Never use verapamil or diltiazem if pre-excited atrial fibrillation or Wolff-Parkinson-White syndrome is suspected, as this can precipitate ventricular fibrillation 7, 8
Hemodynamically Unstable Patients
Immediate synchronized cardioversion is mandatory when vagal maneuvers and adenosine fail or are not feasible 1, 7
Long-Term Management
Definitive Therapy: Catheter Ablation
Slow pathway catheter ablation is the first-line definitive treatment for AVNRT, with success rates of 94.3-98.5% and potential for cure without chronic medication 1, 2, 7
- Class I recommendation from ACC/AHA/HRS guidelines 1, 7
- Eliminates need for lifelong pharmacological therapy 2
- Approach: target right atrial posteroseptum anterior to coronary sinus ostium with 4-mm non-irrigated tip catheter; if unsuccessful, switch to cryoablation targeting mid-septal region 9
Pharmacological Maintenance (for patients declining or not candidates for ablation)
First-line oral agents:
- Verapamil or diltiazem (Class I recommendation): 80-98% success rate for preventing recurrence 1, 2, 7
- Beta-blockers (Class I recommendation): effective alternative with excellent safety profile 1, 2, 7
Second-line oral agents:
- Flecainide or propafenone (Class IIa): reasonable for patients without structural heart disease or ischemic heart disease when first-line agents fail 1
- Sotalol or dofetilide (Class IIb): may be reasonable but lower in treatment hierarchy 1
Minimally symptomatic patients:
- Clinical follow-up without pharmacological therapy or ablation is reasonable (Class IIa recommendation) 1
Critical Safety Considerations
Diagnostic confirmation is essential before treatment:
- Ensure rhythm is truly AVNRT before administering verapamil or diltiazem, as these agents are dangerous in ventricular tachycardia or pre-excited atrial fibrillation 7, 8
- Verapamil should be avoided in patients with severe left ventricular dysfunction (ejection fraction <30%), moderate-to-severe heart failure, or concurrent beta-blocker use due to negative inotropic effects 8
- Beta-blockers and calcium channel blockers should be avoided in patients with severe conduction abnormalities or sinus node dysfunction 1, 7, 8
Post-conversion monitoring: