An active implantable medical device for stimulation, defibrillation and/or cardiac resynchronization, comprising: - means for controlled stimulation of a patient's heart; - means for detecting ventricular and/or atrial depolarization signals; and - means for a morphological analysis capable of comparing depolarization signals collected on a same channel at distinct moments, characterized in that the means for morphological analysis comprise: - means that are capable of inhibiting the means for controlled stimulation; - means that are capable of concurrently collecting, on respective distinct channels, during a spontaneous rhythm cardiac cycle, at least two EGM signals of an endocavitary electrogram and deriving at least two respective distinct temporal components ( Vbip, Vuni) from them; and - means that are capable of combining the at least two temporal components ( Vbip, Vuni) into at least one parametric 2D characteristic representative of said cardiac cycle, based on the variations of one of the temporal components as a function of the other temporal component; and - means for analyzing the 2D characteristic, capable of deriving, from the 2D characteristic or from an average of 2D characteristics collected over successive cardiac cycles, at least one intrinsic descriptor parameter of the 2D characteristic; - means (126, 134) for historical analysis, capable of periodically evaluating the variation over time of said at least one intrinsic descriptor parameter of a current 2D characteristic with respect to a previous reference 2D characteristic stored by the device; - means (126, 134) for comparison, capable of comparing the variation evaluated by the means for historical analysis to at least one predetermined threshold (SEUIL1, SEUIL2) and selectively triggering an alert signaling a worsening of the patient's cardiac condition as a function of the comparison result. - means for controlled stimulation of a patient's heart; - means for detecting ventricular and/or atrial depolarization signals; and - means for a morphological analysis capable of comparing depolarization signals collected on a same channel at distinct moments, - means that are capable of inhibiting the means for controlled stimulation; - means that are capable of concurrently collecting, on respective distinct channels, during a spontaneous rhythm cardiac cycle, at least two EGM signals of an endocavitary electrogram and deriving at least two respective distinct temporal components ( Vbip, Vuni) from them; and - means that are capable of combining the at least two temporal components ( Vbip, Vuni) into at least one parametric 2D characteristic representative of said cardiac cycle, based on the variations of one of the temporal components as a function of the other temporal component; and - means for analyzing the 2D characteristic, capable of deriving, from the 2D characteristic or from an average of 2D characteristics collected over successive cardiac cycles, at least one intrinsic descriptor parameter of the 2D characteristic; - means (126, 134) for historical analysis, capable of periodically evaluating the variation over time of said at least one intrinsic descriptor parameter of a current 2D characteristic with respect to a previous reference 2D characteristic stored by the device; - means (126, 134) for comparison, capable of comparing the variation evaluated by the means for historical analysis to at least one predetermined threshold (SEUIL1, SEUIL2) and selectively triggering an alert signaling a worsening of the patient's cardiac condition as a function of the comparison result.