Alteration of baroreflex sensitivity early after cardiac surgery

Impairment of the baroreceptor reflex activity reflects an alteration of the autonomous regulation of the cardiovascular system and has been proven to predict a fatal outcome in patients after acute myocardial infarction. The following pilot study was performed to analyse the baroreceptor sensitivity in patients early after coronary surgery. 18 male patients (mean age 66.5±14.2 years) with coronary heart disease were examined in a prospective study following aortocoronary bypass surgery; normal values were obtained from healthy volunteers. The strength of baroreflex sensitivity (increases of blood pressure causing a synchronous decrease of heart rate) is low 2 hours postoperatively (3,9±1,9 ms/mmHg; normal value:8). The BRS significantly increases during the period of mechanical ventilation (after 4 hours: 8,4±3,7 ms/mmHg, p<0,05; after 6 hours: 8,4±3,0 ms/mmHg, p<0,05 as compared to the initial value). The apparently stabilized vagal regulation is suppressed again after extubation (2,5±1,8 ms/mmHg). The number of delayed tachycardic changes of heart rate in response to pressure decreases, which are caused by sympathetic activation, is only moderately reduced as compared to values obtained from normal healthy volunteers. 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 systems could be a reason for the high incidence of atrial tachycardias in the early period after cardiac surgery