Active implantable medical device for heart resynchronization through biventricular stimulation, including: - means for detecting atrial and ventricular events; - means for stimulating the right and left ventricles, with the application i) of an atrioventricular delay, DAV, between a spontaneous or stimulated atrial event and a stimulation of the right ventricle, and ii) of an interventricular delay, DVV, between the respective times at which the right and left ventricles are stimulated; - means for multidimensionally measuring the interventricular conduction time, counted between a stimulation of the right ventricle and a spontaneous event detected in the left ventricle, or vice versa, or between a stimulation of the right or left ventricle and a spontaneous event detected between right and left ventricles, during one and the same cardiac cycle; and - means for tracking the variation in a state of the patient, which means are configured to store a history of the conduction times measured at successive dates and to derive therefrom a representative index, the means for multidimensionally measuring the interventricular conduction time comprising: - means that are configured to control, for at least one cardiac cycle, the stimulation means and the detection means so as: • to bring about a stimulation of one of the ventricles; and • to receive, concurrently over distinct respective channels, at least two intracardiac electrogram EGM signals from the other ventricle and to derive therefrom at least two respective distinct temporal components (Vbip, Vuni); - means that are configured to combine the at least two temporal components into at least one parametric 2D characteristic that is representative of the cardiac cycle on the basis of the variations in one of the temporal components with respect to the other, and characterized in that the means for multidimensionally measuring the interventricular conduction time also comprise: - analysis means, configured to derive the 2D characteristic, or a mean of 2D characteristics that are received over successive cardiac cycles, a vector of current intrinsic descriptive parameters of the 2D characteristic; and - comparing means, configured to compare said vector of current descriptive parameters with a homologous vector of reference descriptive parameters so as to derive therefrom an index that is representative of the variation in a state of the patient. - means for detecting atrial and ventricular events; - means for stimulating the right and left ventricles, with the application i) of an atrioventricular delay, DAV, between a spontaneous or stimulated atrial event and a stimulation of the right ventricle, and ii) of an interventricular delay, DVV, between the respective times at which the right and left ventricles are stimulated; - means for multidimensionally measuring the interventricular conduction time, counted between a stimulation of the right ventricle and a spontaneous event detected in the left ventricle, or vice versa, or between a stimulation of the right or left ventricle and a spontaneous event detected between right and left ventricles, during one and the same cardiac cycle; and - means for tracking the variation in a state of the patient, which means are configured to store a history of the conduction times measured at successive dates and to derive therefrom a representative index, - means that are configured to control, for at least one cardiac cycle, the stimulation means and the detection means so as: • to bring about a stimulation of one of the ventricles; and • to receive, concurrently over distinct respective channels, at least two intracardiac electrogram EGM signals from the other ventricle and to derive therefrom at least two respective distinct temporal components (Vbip, Vuni); • to bring about a stimulation of one of the ventricles; and • to receive, concurrently over distinct respective channels, at least two intracardiac electrogram EGM signals from the other ventricle and to derive therefrom at least two respective distinct temporal components (Vbip, Vuni); - means that are configured to combine the at least two temporal components into at least one parametric 2D characteristic that is representative of the cardiac cycle on the basis of the variations in one of the temporal components with respect to the other, - analysis means, configured to derive the 2D characteristic, or a mean of 2D characteristics that are received over successive cardiac cycles, a vector of current intrinsic descriptive parameters of the 2D characteristic; and - comparing means, configured to compare said vector of current descriptive parameters with a homologous vector of reference descriptive parameters so as to derive therefrom an index that is representative of the variation in a state of the patient.