Haemodynamic mechanism of the variety of changes in the right atrial pressure following catecholamines administration

Changes of the right atrial pressure and systemic haemodynamics following action of catecholamines (epinephrine and norepinephrine) were studied in acute experiments on anaesthetised mongrel cats with artificial lung ventilation and opened chest. Maximal changes of the right atrial pressure took place on the 12th-16th second following catecholamine administration. In that case, the atrial pressure could be decreased or increased. At the moment of maximal changes of the right atrial pressure, the venous return and the right ventricular myocardial contractility (the first derivative of the right atrial pressure, dP/dt max) increased more if the right atrial pressure decreased, as compared with the animals whose right atrial pressure augmented. The findings suggest that at the time of the maximal changes of the right atrial pressure following action of catecholamines, there may be a direct connection of the right atrial pressure with interrelation of venous return and the right ventricular contractility. The right atrial pressure, however, is a dependent parameter but it does not determine the venous return.