HEMODYNAMIC AND HORMONAL RESPONSES TO CARDIAC PACING IN HUMANS - INFLUENCE OF DIFFERENT STIMULATION SEQUENCES AND RATES

1. To examine the effects of rate and pressure on release of vasoactiv e hormones, 10 healthy subjects were examined. 2. A standardized pacin g protocol was used to achieve different haemodynamic responses at two predetermined heart rates, Haemodynamic variables, and plasma concent rations of atrial natriuretic peptide, arginine vasopressin, adrenalin e and noradrenaline were measured. 3. Right atrioventricular pacing at a rate of 150 impulses/min resulted in disparate responses in right a trial pressure (slight decrease) and pulmonary capillary wedge pressur e (increase), Change in arterial plasma concentration of atrial natriu retic peptide correlated to change in pulmonary capillary wedge pressu re, and change in arterial plasma concentration of noradrenaline corre lated to change in total systemic vascular resistance, whereas concent rations of adrenaline and arginine vasopressin did not alter significa ntly during the stimulation periods, A significant influence of rate i n addition to the pressure related influence on plasma concentration o f atrial natriuretic peptide was found, In contrast, an increase in ra te in the absence of an increase in atrial pressures did not raise the plasma concentration of atrial natriuretic peptide, There was no sign ificant relationship between change in atrial natriuretic peptide and noradrenaline. 4. These data support the concept of a rate dependence of atrial natriuretic peptide release in man, Increased atrial pressur e and thus presumed atrial stretch seems to be a prerequisite for incr eased plasma concentration of atrial natriuretic peptide, In addition, these results highlight the importance of monitoring both left and ri ght atrial pressure in clinical investigations assessing modulation of atrial natriuretic peptide release.