Basics
Description
- Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common paroxysmal, regular supraventricular tachycardia, accounting for >1/2 of all cases referred for electrophysiologic study.
- The substrate for the arrhythmia is dual AV nodal pathway physiology.
- Synonym(s): PAT (paroxysmal atrial tachycardia) (this term is now obsolete); Junctional reentrant tachycardia; Junctional reciprocating tachycardia; Junctional tachycardia (this is a misnomer)
Pregnancy not contraindicated, but supraventricular tachycardias may be more frequent during and precipitated by pregnancy.
Epidemiology
AVNRT is common. 70% female predominance. Any age can be affected, but AVNRT usually presents at ages 30-50 yr.
Etiology
- There are at least 2 functionally distinct AV nodal conduction pathways:
- The fast pathway is characterized by fast conduction properties and a long refractory period.
- The slow pathway is characterized by slow conduction properties and a short refractory period.
- AVNRT usually begins with a premature atrial depolarization that blocks in the fast pathway since the latter has a long refractory period.
- The impulse then conducts through the slow pathway, and if the fast pathway recovers from depolarization, the impulse can reenter the fast pathway and conduct retrograde to the atria. This completes the reentry circuit, which can repeat.
- Pathologic studies have shown a variety of changes, including entrapment, distortion, and division of the AV node, fibrosis, and even acute necrosis.
- Pathologic findings usually are described in electrical terms. Dual AV nodal pathway physiology is identified at electrophysiologic study.
Diagnosis
Signs and symptoms:
- Palpitations: Typically described as sudden onset/abrupt onset ("like switching on a light")
- Pounding in the neck
- Dyspnea
- Dizziness
- Syncope
- Fatigue (sometimes related to drug therapy)
- Chest pain
- Diaphoresis
Tests
- EKG during episode is diagnostic:
- Narrow QRS tachycardia either without identifiable P waves, or P waves immediately at the end of the QRS, sometimes seen as pseudo-R wave in lead V1 and/or pseudo-S waves in leads II or III
- An atypical variety of AVNRT that uses the slow pathway in the retrograde direction has P waves in the 2nd half of the ST segment (so-called long RP tachycardia).
- Electrophysiologic study, required if undergoing catheter ablation
Lab
Slow and fast AV nodal pathways are not clearly identifiable except at electrophysiologic study.
Differential Diagnosis
- AV reentrant tachycardia that uses an accessory pathway in the retrograde direction
- Atrial tachycardia
- Atrial flutter with 2:1 AV conduction
- Junctional tachycardia
Treatment
Medication
- Acute management:
- Adenosine IV rapid bolus injection of 6-12 mg IV, results in abrupt supraventricular tachycardia (SVT) termination-premature ventricular contractions (PVCs) and premature atrial contractions (PACs) can be seen frequently; then sinus rhythm resumes.
- Verapamil (IV)
- Esmolol (β-blocker)
- Carotid sinus massage or Valsalva maneuver
- Chronic management:
- Calcium channel blocker (eg, verapamil)
- β-Blocker
- Class IC antiarrhythmic drugs (eg, flecainide and propafenone)
- Digoxin may be helpful in selected patients
- Precautions:
- Watch for atrial fibrillation if adenosine used.
- Class IA drugs (quinidine, procainamide, disopyramide) limited due to adverse drug reactions
Additional Treatment
General Measures
- Recording of 12-lead EKG during tachycardia is extremely important to help with diagnosis.
- Typically cured by catheter ablation; no long-term follow-up requirement.
- Due to the problems of long-term drug administration (adverse drug reactions, problem of multiple daily doses/noncompliance, and failure at some time over years of treatment), catheter ablation has emerged as one of the treatments, if not the treatment of choice, for recurrent AVNRT.
- The procedure can be performed safely with a low risk of AV block, and is likely cost-effective long-term and improves quality of life compared with drug therapy, especially class IA and IC agents.
- For a single episode, a conservative approach may be adopted, including observation without drug therapy.
- If ablation is not performed, general medical follow-up is required. For acute management, cardioversion is almost never required because arrhythmia is very responsive to drugs, carotid sinus massage, or Valsalva maneuver.
Surgery
Open heart surgery has been performed in the past to surgically cure AVNRT, but this has been superseded by catheter ablation for cure.
Ongoing Care
Follow-Up Recommendations
- Patients in general do not need to be admitted for AVNRT.
- If drug therapy is chosen, most antiarrhythmics can be started on an outpatient basis, especially because the risk for proarrhythmia is low in these patients with structurally normal hearts, and because drugs causing torsade de pointes ventricular tachycardia are usually not used for this disorder.
- After being seen by an electrophysiologist, an ablation procedure can be arranged.
Patient Monitoring
Relates to treatment options, especially opportunity for cure with catheter ablation
Diet
Usually no dietary restrictions
Patient Education
- Although AVNRT can sometimes be precipitated by exercise and catecholamine increase, there are no specific recommendations regarding activity.
- Vagal maneuvers often terminate arrhythmia.
Prognosis
Excellent
Additional Reading
1
Ganz LI, Friedman PL. Supraventricular tachycardia. N Engl J Med. 1995;332:162-173.
2
Jackman WM, Beckman KJ, McClelland JH Treatment of supraventricular tachycardia due to atrioventricular nodal reentry by radiofrequency catheter ablation of slow-pathway conduction. N Engl J Med. 1992;327:313-318.
3
Kay GN, Plumb VJ. Selective slow pathway ablation (posterior approach) for treatment for atrioventricular nodal reentrant tachycardia. In: Radiofrequency Catheter Ablation of Cardiac Arrhythmias: Basic Concepts and Clinical Applications. Armonk, NY: Futura, 1994:171-203.
Codes
ICD9
427.89 Other specified cardiac dysrhythmias
SNOMED
419752005 sinoatrial nodal reentrant tachycardia (disorder)