Abstract: An atrium-controlled heart pacemaker operates using set parameters including a smallest synchronous interval (SSI) between two stimulation pulses, a minimum atrial-ventricular delay time (AVmin) and a maximum atrial-ventricular delay time (AVmax). A control unit, dependent upon the appearance of an atrial signal, controls operation of the pacemaker such that the pacemaker operates with a variable pulse rate (DDD mode) when the atrial signal appears after a point in time SSI-AVmin, operates the pacemaker with a highest synchronous pulse rate when the atrial signal is between the points in time SSI-AVmin and SSI-AVmax, and causes no stimulation pulses to be emitted when the atrial signal appears before the point in time SSI-AVmax.

Abstract: A cardiac pacer which generates pacing pulses at a predetermined pacing rate includes a device for processing the pacing pulses according to an impedance measurement such that a respiratory signal is obtained. The predetermined pacing rate is then varied dependent on the respiratory signal.

Abstract: A heart pacemaker has circuitry for forming an electrical signal corresponding to the electrode impedance of the pacemaker. The signal is formed by monitoring the stimulation current and the stimulation voltage and dividing those values by each other in a divider. This impedance signal is a measure of the respiration rate of the pacemaker user, and is employed for controlling the pulse rate of the pulse generator of the heart pacemaker in accordance therewith.