The atrioventricular (AV) node is a subendocardial structure located in the inferior-posterior right atrium. In an average adult, an AV node measures approximately 1 x 3 x 5 millimeters and sits within an anatomic region bordered posteriorly by the coronary sinus ostium, superiorly by the tendon of Todaro, and anteriorly by the septal tricuspid valve annulus. This anatomic region is also commonly referred to as the triangle of Koch. The blood supply to the AV node is from the AV nodal branch of the right coronary artery (90%) or the left circumflex artery (10%) depending on the right or left dominant blood supply to the heart. The first septal perforator of the left anterior descending artery also supplies blood to the AV node.

Atrioventricular nodal reentrant tachycardia (AVNRT) is a type of paroxysmal supraventricular tachycardia that results due to the presence of a reentry circuit within or adjacent to the AV node. The diagnosis of AVNRT requires visualization on an electrocardiogram (ECG). In most cases, an ECG will show heart rate between 140 and 280 beats per minute (bpm), and in the absence of aberrant conduction, a QRS complex of fewer than 120 milliseconds. ECG criteria based on the reentrant circuits are as follows:

Slow-Fast AVNRT

1. Pseudo-S wave in leads II, III, and AVF

2. Pseudo-R' in lead V1.

Fast-Slow AVNRT

1. P waves between the QRS and T waves (QRS-P-T complexes)

Slow-Slow AVNRT

1. Late P waves after a QRS - often appears as atrial tachycardia

Disclosure:Yamama Hafeez declares no relevant financial relationships with ineligible companies.

Disclosure:Tyler Armstrong declares no relevant financial relationships with ineligible companies.