1. An active medical device comprising: a pulse generator coupled to a lead for delivering electrical stimulation pulses of low energy to an electrode implanted in a heart chamber of a patient; a microprocessor comprising circuitry for collecting electrical activity of the heart chamber, and configured for producing at least two distinct temporal components from two, concurrently collected, distinct electrogram intracardiac EGM signals of said heart chamber; wherein the circuitry is further configured for performing a capture test on a stimulated cardiac cycle, the capture test comprising: detecting an occurrence of a depolarization wave induced by the stimulation pulses to the heart chamber during the stimulation cardiac cycle; determining a two-dimensional non-temporal characteristic (VGM) representative of said stimulated cardiac cycle based upon a relative tracing of one of said at least two distinct temporal components relative to the other of said at least two distinct temporal components; and 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 for said stimulated cardiac cycle based on said at least one descriptor parameter.