Abstract: A process and device to control a cardiac pacemaker enslaved to at least one physiological parameter. The pacemaker also possesses a mode of desynchronization of the ventricular stimulation when the atrial rhythm is too rapid for synchronous operation. One compares a detected coupling interval (PP) with an escape interval calculated by the enslavement (EI.sub.ASSERV). The calculated enslavement escape interval is preferably decreased by a prematurity factor (x), for example, 0 to 50%, preferably approximately 37.5%, of the calculated escape interval. After the comparison, one counts the number of cardiac cycles for which the coupling interval detected is less than the calculated escape interval, and one triggers the mode of desynchronization (FALLBACK) when the count exceeds a given threshold (y), for example 50 to 75%, preferably approximately 75% of the total number (N) of cardiac cycles analyzed.

Abstract: Control of an anti-tachycardia device such as a defibrillator to apply a preselected programmed therapy in the event of ventricular tachycardia. The control includes comparison of the atrial and ventricular rhythms, and examination of the criteria of stability of the P-R intervals, of the stability of the R-R intervals, and of the acceleration of the ventricular rhythm subsequent to an atrioventricular desynchronization, thereby to ensure control of the antitachycardia device solely in the event of ventricular tachycardia.

Abstract: A cardiac pacemaker having a pacing rate responsive to a control function of a physiological parameter indicative of activity levels. The coefficients of the function are automatically calculated and modified in response to the trend of the measured physiological parameter in order to correspond to the patient real needs. For monitoring the physiological parameter minute ventilation (VE), the basic value VE low and maximum value VE max are calculated in order to vary the slope and intercept of the straight line representative of the control relation of the pacing rate FC by the minute volume VE.

Abstract: Controlling a cardiac pacemaker wherein the cardiac pacing rate is controlled according to a measure of the metabolic demand. The average minute ventilation MV-8-0 is measured over the eight last breathing cycles (first one to eighth one), and it is compared with the average minute ventilation MV-8-1 over the previous eight breathing cycles (ninth one to sixteenth one), and it is determined that an effort phase is present when MV-8-0>MV-8-1, and that a recovery phase is present when MV-8-0<MV-8-1. These determinations are used to determine whether sensed changes in the ventilation correspond to transitions between the effort and recovery or ventilation gaps or artifacts so that the cardiac pacing rate is not decreased during an effort.