Patent ID: 7020522

Claim:
A heart stimulator comprising: a stimulation pulse generator adapted for interaction with an atrium and a ventricle of a heart for generating atrial stimulation pulses and ventricular stimulation pulses having an associated AV-interval; an atrial sensor, adapted for interaction with said atrium, for sensing atrial signals therefrom; an evoked response detector adapted for interaction with said ventricle for receiving ventricular signals, for detecting evoked response signals and including an averaging unit which forms an average amplitude value of respective evoked response signals during a predetermined time window of each cardiac cycle, said average amplitude values exhibiting a variability from cardiac cycle to cardiac cycle, and a comparator which compares said average amplitude value for each cardiac cycle with a predetermined variability limit, to generate a comparison result; a determination unit connected to said evoked response detector and to said atrial sensor, which determines an incipient fusion AV-interval to be present if said comparison result indicates said variability limit was exceeded; and a control unit connected to said determination unit and to said pulse generator for controlling timing of said ventricular pulses to produce a controlled AV-interval which is shorter than said incipient fusion AV-interval to maintain 100% stimulated beating of said heart.