An active implantable medical device, notably for pacing, resynchronization, defibrillation and/or cardioversion of the heart, or for diagnosis of a patient's condition, able to produce a predictive alert in response to a detected degradation of the patient's clinical status. The device measures and analyses (56) a parameter representative of the patient's metabolic needs, such as minute ventilation (MV), and a physical activity parameter, such as acceleration (G). It further diagnoses heart failure by evaluating an index of the patient's clinical status through applying a set of status criteria (S1, S2). It further measures and analyzes (56) a hemodynamic parameter such as endocardial acceleration (PEA) or intracardiac impedance, representative of the patient's myocardium contractility. An index of cardiac contractility is created and evaluated through applying a set of contractility criteria (S′1, S′2). A cross-analysis is then performed to provide a composite preventive alert signal as a function of the respective values taken by the clinical status and cardiac contractility indices. This signal can have different levels according to whether the sets of criteria have, or not, triggered an alert relating to the clinical status or cardiac contractility.