The system includes an active medical device with means for delivering defibrillation shocks; means for continuous collection of the patient current cardiac activity parameters; and evaluator means with neuronal analysis comprising a neural network with at least two layers. This neural network comprises upstream three neural sub-networks receiving the respective parameters divided into separate sub-groups corresponding to classes of arrhythmogenic factors; and downstream an output neuron coupled to the three sub-networks and capable of outputting an index of risk of ventricular arrhythmia. The risk index is compared with a given threshold, to enable or disable at least one function of the device in case of crossing of the threshold.