Most Common Supraventricular Tachycardia
Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of supraventricular tachycardia in the general population. 1, 2
Epidemiology and Clinical Characteristics
AVNRT accounts for the majority of paroxysmal SVT cases, particularly affecting middle-aged and older adults with a mean age of symptom onset of 32±18 years. 2
This arrhythmia is more prevalent in females and typically presents with palpitations, dizziness, and characteristic neck pulsations. 1
AVNRT is not usually associated with structural heart disease, distinguishing it from other forms of SVT that may indicate underlying cardiac pathology. 1
Mechanism
The arrhythmia results from reentry within the AV node using dual pathways (fast and slow conduction pathways), though contemporary understanding recognizes that perinodal atrial tissue usually participates in the reentrant circuit. 1, 2
In typical AVNRT (90-95% of cases), the slow pathway serves as the anterograde limb and the fast pathway as the retrograde limb (slow-fast conduction), producing P waves buried in or immediately after the QRS complex (≤70 ms). 1
Atypical AVNRT (5-10% of cases) reverses this pattern with fast-slow conduction, creating a long R-P tachycardia with negative P waves in leads III and aVF inscribed before the QRS. 1
Comparison to Other Common SVTs
AVRT (atrioventricular reentrant tachycardia) is the second most common SVT, requiring an accessory pathway and presenting at a younger mean age of 23±14 years. 2
Atrial tachycardia is less common than both AVNRT and AVRT, arising from a localized atrial focus with discrete P waves and regular organized atrial activity. 2
The incidence of sinus node reentry tachycardia ranges from only 1.8% to 16.9% of patients undergoing electrophysiological study for SVT, making it considerably less common than AVNRT. 1
Clinical Pitfall
Do not confuse AVNRT prevalence with overall SVT presentations in the emergency department, where atrial fibrillation may be more commonly encountered but is technically classified separately from paroxysmal SVT. 1
Heart rates typically range from 140-250 bpm during AVNRT episodes, and the arrhythmia characteristically starts and stops abruptly. 1