Implantable medical device comprising an active mode of resynchronization of the ventricular contractions to the treatment of heart failure

This device comprises a generator (30) connected to a left ventricular electrode (12) and a right ventricular electrode (22). The generator comprises two output terminals (14, 24) connected to the ventricular electrodes (12, 22), and means for providing in conjunction with the electrodes of the respective stimulation pulses with an adjustable inter-ventricular delay (IVD). According to the invention, the generator is a double type pacemaker generator chamber (40) comprising an atrial terminal (60), a ventricular terminal (50), and means for jointly deliver the atrial and ventricular terminals stimulation pulses with a AVD adjustable (DAV). One (14) of the output terminals is the terminal atrial (A) and the other (24) is ventricular terminal (V), the atrioventricular delay (AVD) is adjusted to the value of the interventricular delay (IVD ).