Effect of Cardiac Tamponade on Plasma Concentrations of Atrial Natriuretic Peptide (ANP) in Calves

Summary

To study the effect of cardiac tamponade on plasma concentrations of atrial natriuretic peptide (ANP) female calves received an infusion of 450 ml of 0.9% saline into the pericardial space. This was accompanied by a parallel rise in both, right atrial pressure (from 4.5 ± 2.6 mm Hg to 14.1 ± 3.8 mm Hg (p < 0.01)) and in intrapericardial pressure (from 0.4 ± 2.0 mm Hg to 12.9 ± 3.9 mm Hg (p < 0.01)) and a fall in cardiac output from 11.4 ±1.9 1/min to 8.5 ± 2.4 1/min (p < 0.01). Plasma concentrations of ANP remained unchanged in 7 of 9 experiments. During these seven experiments plasma concentrations of renin and aldosterone increased from 0.65 ± 0.27 ×10 E-4 GU/ ml to 1.04 ± 0.43× 10E-4 GU/ml (p < 0.01) and from 2.7 ± 0.9ng/dl to 11.4 ± 6.1ng/dl(p < 0.01), respectively. On two occasions, which were characterized by an excessive fall in cardiac output (to less than 40% of initial values) cardiac tamponade was followed by an extensive rise in the plasma concentrations of ANP, renin and aldosterone. These results indicate that an increase in intra-atrial pressure per se is not the decisive factor in the control of ANP secretion. Since atrial transmural pressure does not change during cardiac tamponade ANP concentrations are, as a rule, unaltered by that condition. An increase in plasma ANP is seen only during preshock hemodynamic conditions possibly due to a reduced intra-atrial volume.

Key words

ANP - Cardiac tamponade