Cardiac pacemaker with automatic adaptation of pacing rate to cardiac output

A cardiac pacemaker comprising:

• a pulse generator which emits stimulation pulses;
• an electrode system connected to said pulse generator and adapted to deliver respective stimulation pulses to both atria and both ventricles of a heart of a subject, said pulse generator emitting said stimulation pulses with time delays including a VV-delay between consecutive stimulation pulses to the respective ventricles and an AA-delay between consecutive stimulation pulses to the respective atria;
• a sensor adapted for interaction with said subject to measure a parameter associated with cardiac output of said subject and to generate a measurement signal dependent thereon;
• a control unit connected to said pulse generator for controlling emission of stimulation pulses by said pulse generator, said control unit altering at least one of said time delays, as an altered time delay, from a predetermined first value to a second value and back to said first value;
• a windowing unit connected to said sensor and controlled by said control unit to obtain said measurement signal in a first time window during operation of said pulse generator with said at least one altered time delay at said first value, and in a second time window during operation of said pulse generator with said at least one altered time delay at said second value, and in a third time window after returning to operation of said pulse generator with said at least one altered time delay at said first value;
• a calculating unit connected to said windowing unit which calculates respective average values of said measured signal in each of said first, second and third time windows, and generates an output dependent thereon;
• and
• said control unit being supplied with said output from said calculating unit and determining therefrom, as an optimized value, which of said first and second values of said at least one altered time delay produced a higher cardiac output, and thereafter controlling said pulse generator to operate with said at least one altered time delay at said optimized value.