Measuring a trans-septum bio-impedance in an active implantable medical device, in a particular pacemaker, defibrillator and/or cadiovertor and/or multisite device

An active implantable medical device, in particular a pacemaker, defibrillator and/or cardiovertor and/or a multisite device, including a cardiac signal collection circuit, to detect a potential of depolarization, and a stimulation circuit, to apply stimulation pulses, said circuits being connectable to at least two electrodes placed in a plurality of distinct respective sites comprising at least one left ventricular site and one right atrial site, or at least one right ventricular site and one left atrial site, said device further comprising means for measuring an intracardiac measurement of bio-impedance and evaluating a cardiac flow based on said impedance, said device being characterized in that the means for evaluating the cardiac flow further comprises means for measuring a trans-septum bio-impedance between one of the left ventricle and the right atrium, and the right ventricle and the left atrium, respectively, by injection of a current between an atrial site and a ventricular site and collection of a differential potential between an atrial site and a ventricular site.