Baroreflex sensitivity, heart rate and blood pressure variability have been proven to predict fatal outcome in patients after acute myocardial infarction. This study aims at investigating the time dependent alterations in cardiovascular control to find new predictive parameters for arrhythmic events after surgery. 25 male patients with coronary heart disease following an aortocoronary bypass surgery were examined. The results show significant alterations in sympathetic and vagal mediated regulation. The extubation after 6 hours seems to influence primarily the sympathetic activation. Obviously, there is a vagal suppression 20 h after surgery, while the sympathetic tonus works in a normal range. This unbalanced interaction of the autonomous system seems to be a reason for the high incidence of atrial tachycardias in the early period after cardiac surgery.