Atrioventricular Nodal Reentry Tachycardia (AVNRT)
- Author: Brian Olshansky, MD; Chief Editor: Jeffrey N Rottman, MD more...
Background
Atrioventricular nodal reentry tachycardia (AVNRT) is the most common type of reentrant supraventricular tachycardia (SVT). Because of the abrupt onset and termination of the reentrant SVT, the nonspecific term paroxysmal supraventricular tachycardia (or even the misleading term paroxysmal atrial tachycardia [PAT]) has been used to refer to these tachyarrhythmias. With improved knowledge of the electrophysiology of reentrant SVT, more specific nomenclature based on the mechanism of reentry helps in better classifying these arrhythmias and thus helps in choosing appropriate therapies.
Pathophysiology
The substrate for AVNRT may be functional rather than anatomic. These arrhythmias occur in young, healthy patients and in those with chronic heart disease.
In patients with atrioventricular (AV) nodal reentry, the AV node is functionally divided into 2 longitudinal pathways that form the reentrant circuit. In the majority of patients, during AVNRT, antegrade conduction occurs to the ventricle over the slow (alpha) pathway and retrograde conduction occurs over the fast (beta) pathway (see image below). In most patients with this arrhythmia, the tachycardia is initiated when an atrial premature complex is blocked in the fast pathway with a longer refractory period and conducts in the slow pathway with a shorter refractory period (see image below). While the impulse conducts to the ventricle in the slow pathway (antegrade conduction), the fast pathway recovers so that the impulse can conduct retrograde up the fast pathway to the atrium and the atrial end of the slow pathway (retrograde conduction).
Electrophysiological mechanism of atrioventricular nodal reentry tachycardia. In approximately one third of patients, AVNRT is induced by premature ventricular stimulation. In addition to the typical mechanism of AV nodal reentry described above, atypical AV nodal reentry can occur in the opposite direction, with antegrade conduction in the fast pathway and retrograde conduction in the slow pathway. Less commonly, the reentrant circuit can be over 2 slow pathways, the so-called slow-slow AV nodal reentry.
Atypical atrioventricular nodal reentry tachycardia.
Typical atrioventricular nodal reentry tachycardia. Epidemiology
Frequency
United States
AVNRT occurs in 60% of patients (with a female predominance) presenting with paroxysmal SVT. The prevalence of SVT in the general population is likely several cases per thousand persons.
International
Frequency is similar to that in the United States.
Mortality/Morbidity
AVNRT is usually well tolerated; it often occurs in patients with no structural heart disease. In patients with coronary artery disease, AVNRT may cause angina or myocardial infarction. Prognosis for patients without heart disease is usually good.
Race
No known racial predilection exists.
Sex
More women than men have AVNRT.
Age
AVNRT may occur in persons of any age. It is common in young adults.
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