Typical atrioventricular nodal reentrant tachycardia

The first two complexes are normal sinus beats with a normal P wave followed by a QRS complex. The third complex, an atrial premature beat (APB), has a prolonged PR interval; it initiates a common or typical atrioventricular nodal reentrant tachycardia (AVNRT) in which antegrade conduction to the ventricle is via the slow pathway and retrograde atrial activation is by the fast pathway. Although no distinct P wave is seen, the QRS complex has a small terminal deflection, known as a pseudo r', which is the P wave superimposed upon the terminal portion of the QRS complex.