Ablation of the atrioventricular junction consists in creating a therapeutic AV block to facilitate the treatment of symptoms caused by atrial arrhythmias refractory to drug therapy. The technical performance of ablation has been improved by restricting the indication to atrial fibrillation, by using radiofrequency currents, by choosing a nodal rather than His bundle ablation site, and by improving the function of cardiac pacemakers (rate adapting, back-up). The functional results are excellent but the outcome is punctuated by rare cases of sudden death, the cause of which is not fully understood (dependance, ventricular arrhythmias, ...). To avoid permanent pacing, it has been suggested that atrioventricular conduction should be modulated rather than completely interrupted. Modulation of the fast pathway has been shown to be ineffective; that of the more complex, slow pathway, seems to be more promising. Although this obviates the need for a pacemaker, it does not suppress irregularity of the ventricular rhythm, the main cause of symptoms in paroxysmal atrial fibrillation and of the haemodynamic changes associated with permanent atrial fibrillation.