1. An active medical device, comprising: means for delivering electrical stimulation pulses of low energy to an electrode implanted in a heart chamber of a patient; means for collecting electrical activity of the heart chamber, comprising means for producing at least two distinct temporal components from two distinct electrogram intracardiac EGM signals of said heart chamber, and means for performing a capture test on a stimulated cardiac cycle, comprising: means for detecting an occurrence of a depolarization wave induced by the stimulation pulses to the heart chamber during the stimulation cardiac cycle; means for determining a two-dimensional non-temporal characteristic (VGM) representative of said stimulated cardiac cycle based upon a variation of one of said at least two distinct temporal components relative to the other of said at least two distinct temporal components, and means for performing a bi-dimensional analysis and delivering at least one descriptor parameter of said two-dimensional non-temporal characteristic, and determining a presence or a loss of a capture based on said at least one descriptor parameter.