AV nodal reentrant tachycardia

Atrioventricular nodal reentrant tachycardia is a supraventricular tachyarrhythmia that originates within the atrioventricular node. The rate is generally between 140 to 220 beats per minute and there is usually a 1:1 atrial-ventricular association; as a result, every QRS complex has an associated P wave. In this case, atrial and ventricular activation are simultaneous; as a result, the P wave is superimposed upon the QRS complex and therefore not obvious on the surface ECG.

The normal P wave in sinus rhythm is slightly notched since activation of the right atrium precedes that of the left atrium. The P wave is upright in a positive direction in leads I and II. A P wave with a uniform morphology precedes each QRS complex. The rate is between 60 and 100 beats per minute and the cycle length is uniform between sequential P waves and QRS complexes. In addition, the P wave morphology and PR intervals are identical from beat to beat.