Automaticity in rate adaptive cardiac pacing

The development of future cardiac pacing systems aims at the automated control of parameters for pacing, timing and rate control. For the realization of these goals suitable sensors are required, which can reliably determine the cardiac state. For the purpose of physiological rate control a parameter reflecting autonomic activity can be extracted from myocardial contractile performance via unipolar intracardiac impedance measurement. Clinical investigations were performed which demonstrate that unipolar intracardiac impedance is suited for an automatic adaptation of the pacing rate response with respect to level and timing. The automatic rate response seen in clinical application is due to the fact that the natural closed-loop circulation control is re-established.