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Transcatheter ablation of atrial fibrillation has been recently developed and is part now of the armamentarium in the treatment of atrial fibrillation. The ablation of atrial fibrillation started out from the experience of the surgical maze procedure, which showed very encouraging results but at a high price because it required open chest surgery. In the following years the attempt has been made to produce similar results using transcatheter ablation. Different approaches have been used: linear lesions mimicking the surgical maze operation, linear lesions in the right or left atrium using different schemes, or a sequential approach ablating first in the right and then in the left atrium.

Atrial fibrillation is the most frequent supraventricular arrhythmia, and recently it has become clear that it is not a completely benign arrhythmia, since complications such as thromboembolism or ventricular impairment may sometimes occur. Even in absence of associated cardiac disease, when the incidence of these complications is relatively low, the presence of atrial fibrillation generally causes a worsening of quality of life, due to the irregularity of the rhythm or the high ventricular rate, and therefore generally requires life-long therapy.

The atrioventricular (AV) junction is a rather complex structure involved in the genesis of the atrioventricular junctional reentrant tachycardia (AVJRT), which is the most frequent supraventricular arrhythmia. The advent of radiofrequency (RF) catheter ablation, that has been developed in the recent years, has provided a new therapeutic tool for the radical cure of this arrhythmia. In the meantime the more precise and extensive mapping of the septal region has provided new insight in the physiology and anatomy of the AV junction. This has led to questioning of some previously accepted concepts on its electrophysiology, and rekindled the interest of anatomists and experimental and clinical electrophysiologists, particularly in relation to the mechanism of reentry in humans.

Atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is the most frequent form of supraventricular tachycardia. Its electrophysiologic mechanism has been known for many years. In 1913 Mines (1) first performed experiments on the AV connections of the heart and explained the mechanism of this arrhythmia as follows