In AV node reentrant tachycardia, the atrial electrogram is typically encompassed within or at the tail end of the QRS complex. In this chapter, we show an example that demonstrates baseline recordings in a patient who has AV node reentrant tachycardia. In this patient, the AH and HV intervals are normal. Subsequently, during atrial overdrive pacing, AV node reentrant tachycardia is induced (figure 18.3). An atrial electrogram is seen in the high right atrial recording, at the latter part of the QRS complex. In typical AV node reentrant tachycardia, conduction occurs down a slow AV nodal pathway and up a fast AV nodal pathway.
These tachycardias can be terminated easily with the infusion of adenosine (6 mg initially and 12 mg if they fail to respond). The tachycardias also can be terminated with carotid sinus massage. The termination of the tachycardia ending with an atrial electrogram helps to rule out an atrial tachycardia.