Detection of an evoked post-stimulation potential, in particular atrial potentials, in an active implantable medical device such as a cardiac pacemaker, a defibrillator, a cardioveter, or a multisite device. This device applies a stimulation pulse (40), then shorts-circuit for a discharge period (42, OCD) the output circuit, which includes discharging a connection capacitor, the self-impedance of the probe, and the impedance of the interface heart-electrode. A detection circuit includes an amplifier and a blanking circuit to temporarily uncouple the input terminal from the amplifier. A sequencer control circuit activates during a first time (micro blanking) the blanking circuit throughout the stimulation pulse (40), activates the discharging circuit with a delay after the application of the stimulation pulse, then inhibits the blanking circuit for a listening period (44), defining at least part of this delay, so as to authorize detection by the amplifier, during the listening period, of the evoked post-stimulation potentials, and then activates the blanking circuit a second time (BLANKING) after the listening period throughout the discharge period (42, OCD).