A monitoring system for ablation of cardiac tissue in close proximity to the AV node of the heart, characterized in that it comprises :▪ At least one ablation catheter (12) powered by a power source (16)▪ At least one electrode (13) acquiring an intracardiac electrogram (IEGM), called IEGM electrode ▪ At least one set of electrodes (14) acquiring a surface electrocardiogram (ECG), called ECG electrodes ▪ At least one calculator (15, 16, 17, 18, 19, 25, 27) and a memory for measuring in real time at least one of (i) signals acquired from the IEGM electrode and the ECG electrodes, and (ii) catheter tip location, in order to automatically generate an estimate of the level of risk of heart block, called Risk index (Ri), said risk index (Ri) activating ta sensorial alert.
