Atrioventricular Nodal Reentry Tachycardia (AVNRT)

Melvin M. Scheinman, M.D., F.A.C.P.
University of California, San Francisco, School of Medicine

Definition/Key Clinical Features

AVNRT is the most common form of supraventricular tachycardia; it results from conduction through a reentrant circuit comprising fast and slow atrioventricular nodal pathways
Heart rate, 150–250 beats/min
Neck pounding
Palpitations, light-headedness, near-syncope
Narrow QRS complexes on ECG
Abrupt onset and termination of episodes
More common in women than in men
Frequently presents after 20 yr of age

Differential Diagnosis

Best Tests

12-lead ECG
- The P wave is either buried within the QRS complex or inscribed just after the QRS complex
The P wave inscribed by retroconduction over the AV node is negative in the inferior leads and positive in lead V1; PSVT may manifest as small negative deflections in the inferior leads and a small positive deflection in V1 (pseudo r¹ pattern)

Best Therapy

Acute Therapy

Nonpharmacologic

Pharmacologic

Adenosine: for use when carotid massage fails to convert SVT
- Possible adverse effects: headache, wheezing, flushing, which will disappear within 45–60 sec; atrial, ventricular, and junctional premature beats; atrial fibrillation in 3% to 5% of cases, which may result in serious problems for patients with accessory pathways
- An external defibrillator should be readily available when adenosine is administered
- Dose: initial dose: rapid bolus of 6 mg I.V., followed by a saline flush; if necessary, a 12 mg dose and finally an 18 mg dose can be given
Metoprolol (5 mg I.V.) or verapamil (0.1 mg/kg I.V.) for patients who fail to respond to adenosine

Long-term Therapy

Pharmacologic

Beta blockers
Sotalol
- Common side effects: torsade de pointes, heart failure, bradycardia, exacerbation of chronic obstructive or bronchospastic lung disease
- Adjust dose for renal function and QT-interval response during in-hospital initiation phase
- Dose: 240–3 © 2004 WebMD Inc. All rights reserved.