An active implantable medical device such as a cardiac prosthesis, including ventricular capture testing by analysis of an endocardial acceleration signal. The device isolates in an endocardial acceleration (“EA”) signal an EA component, extracts from it, n representative indicators (PEA_i, LEA_i), and forms a vector EA (X_i) from these indicators. A classifier allows acquiring reference EA signals at a stimulation energy level sufficient to cause a capture, and in spontaneous rhythm in the absence of ventricular pacing and forms a corresponding plurality of first reference EA vectors. The n-dimensional space of the EA vectors is partitioned into two corresponding subspaces. The presence or absence of a capture is discriminated based on the position of the current EA vector (X_i) in one or other of these two sub-spaces. The representative indicators may be: the value of peak to peak amplitude, the width, the moment of occurrence of the peak, the starting time and the ending time of the EA1 and/or EA2 components, the signal to noise ratio (SNR), the contrast value, the entropy value, and the cumulative energy of the EA1 and/or EA2 component, or the value of the peak-to-peak amplitude of the EA 4 component.
