A unit for evaluation and adaptation of an anti-tachycardia therapy, comprising: a) an active medical device adapted to be implanted in a patient, comprising: - means for delivering defibrillation shocks; - means for continuously collecting parameters of current cardiac activity of the patient; and - evaluator means comprising a neural network with at least two layers, characterized in that said neural network comprises: • upstream, three neural subnetworks (28a, 28b, 28c), receiving the parameters distributed into three respective distinct subgroups corresponding to classes of arrhythmogenic factors, with: a first of said subgroups comprising electrophysiologic substrate descriptors, a second of said subgroups comprising pejorative modulator descriptors, and a third of said subgroups comprising trigger factor descriptors; • downstream, an output neural network comprising at least one output neuron coupled to three upstream subnetworks and adapted to deliver a ventricular arrhythmia risk index, and in that the active medical device further comprises: - means adapted to compare the ventricular arrhythmia risk index with a given threshold and to activate or deactivate at least one function of the device in case of threshold crossing. a) an active medical device adapted to be implanted in a patient, comprising: - means for delivering defibrillation shocks; - means for continuously collecting parameters of current cardiac activity of the patient; and - evaluator means comprising a neural network with at least two layers, characterized in that said neural network comprises: • upstream, three neural subnetworks (28a, 28b, 28c), receiving the parameters distributed into three respective distinct subgroups corresponding to classes of arrhythmogenic factors, with: a first of said subgroups comprising electrophysiologic substrate descriptors, a second of said subgroups comprising pejorative modulator descriptors, and a third of said subgroups comprising trigger factor descriptors; • downstream, an output neural network comprising at least one output neuron coupled to three upstream subnetworks and adapted to deliver a ventricular arrhythmia risk index, and in that the active medical device further comprises: - means adapted to compare the ventricular arrhythmia risk index with a given threshold and to activate or deactivate at least one function of the device in case of threshold crossing. - means for delivering defibrillation shocks; - means for continuously collecting parameters of current cardiac activity of the patient; and - evaluator means comprising a neural network with at least two layers, • upstream, three neural subnetworks (28a, 28b, 28c), receiving the parameters distributed into three respective distinct subgroups corresponding to classes of arrhythmogenic factors, with: a first of said subgroups comprising electrophysiologic substrate descriptors, a second of said subgroups comprising pejorative modulator descriptors, and a third of said subgroups comprising trigger factor descriptors; a first of said subgroups comprising electrophysiologic substrate descriptors, a second of said subgroups comprising pejorative modulator descriptors, and a third of said subgroups comprising trigger factor descriptors; • downstream, an output neural network comprising at least one output neuron coupled to three upstream subnetworks and adapted to deliver a ventricular arrhythmia risk index, - means adapted to compare the ventricular arrhythmia risk index with a given threshold and to activate or deactivate at least one function of the device in case of threshold crossing.