Intraatrial reentrant tachycardia

An electrocardiogram from a patient with a Fontan repair, demonstrating an intra-atrial reentrant tachycardia. The periods of higher grade AV block allow for easy identification of the P waves. Without these pauses, the atrial rhythm can be difficult to identify, as the P waves are frequently buried within the preceding QRS complex. This is most evident on the paced beats.