The Autocapture function detects the evoked response signal (ERS) to verify beat-to-beat capture, and optimizes the output of ventricular pulse amplitude automatically. We had experience concerning the instability of the Autocapture recommendation in some patients. Evoked response is subject to variation as it is a biological event. However, the present knowledge about the Autocapture function lability is very limited. The purpose of this study was to evaluate whether mental stress, body positions or exercise influence the ERS and PS in children.