Reentrant junctional tachycardias.

Most of the tachycardia arising in the atrioventricular (AV) junction are reentrant in nature. The two most common variety are AV nodal reentry and AV reentry utilizing an accessory pathway of the Kent bundle type. Typically these tachycardias have narrow QRS complex and are regular but an associated right or left bundle branch block could result in a wide QRS complex. Other mechanisms for wide QRS in AV junctional tachycardia include: (a) antidromic reentry; (b) preexcited tachycardia using two accessory pathways; (c) AV nodal reentry with incidental accessory pathway participation; and (d) atriofascicular (nodoventricular)e Mahaim participation. A variety of surface ECG and intracardiac electrophysiological methods are used to delineate the precise mechanisms which is essential for successful nonpharmacological therapy in these patients.