Atrioventricular Reciprocating Tachycardia

Atrioventricular reciprocating tachycardia (AVRT) is a type of supraventricular tachycardia (SVT) that requires specific electrophysiologic and electroanatomic characteristics. AVRT uses a circuit that consists of at least 2 different pathways with different electrical properties, including conduction velocity, refractory periods, and directionality. The anatomical substrate to sustain an AVRT can vary because AVRT may involve different configurations as follows: Two accessory pathways (APs) that enable communication between the atria and the ventricles. A single accessory pathway, in addition to the regular conduction system through the atrioventricular node, completes the circuit. Multiple accessory pathways through which the SVT can be perpetuated. . AVRT commonly starts with an ectopic atrial or ventricular beat that travels through one of the circuit's limbs due to the distinct electrical properties of the tissues involved. These properties allow the initiation and persistence of an SVT at a heart rate ranging from 150 to 250 bpm.  AVRT is the most common type of arrhythmia associated with Wolff-Parkinson-White (WPW) syndrome. In this condition, antegrade conduction at rest occurs through an accessory pathway (or accessory pathways) that manifests on the surface electrocardiogram (ECG). The ECG shows a shortened PR interval followed by a delta wave or slurring of the initial portion of the QRS complex, which results in a widened QRS complex. AVRT can use an antegrade and non-decremental accessory pathway in these patients, and retrograde conduction can occur through the atrioventricular node or another accessory pathway. These patients can also develop accelerated conduction of atrial arrhythmias through the accessory pathway or accessory pathways that bypass the atrioventricular node. These preexcited atrial arrhythmias, especially atrial fibrillation, can be lethal due to rapid conduction into the ventricles. Permanent junctional reciprocating tachycardia is a rare type of AVRT, which uses the atrioventricular node as its antegrade limb and a decrementally conducting accessory pathway as its retrograde limb. This type of tachycardia typically has a slower heart rate, between 130 and 150 bpm, and is commonly refractory to medical management. Other unusual forms of AVRT use atrioventricular or nodoventricular accessory pathways, known as Mahaim pathways. These are decrementally conducting anomalous connections between the right atrium or the atrioventricular node and the right ventricle.