Sequential changes in atrial pressures, dimensions, and plasma atrial natriuretic factor concentrations during volume loading in hemodynamically normal human subjects
Moe, G.W.; Canepa-Anson, R.; Howard, R.J.; Armstrong, P.W.
Journal of Laboratory and Clinical Medicine 117(6): 528-534
1991
ISSN/ISBN: 0022-2143 PMID: 1828490 Document Number: 377419
The effects of volume loading on atrial pressures and dimensions, plasma levels of atrial natriuretic factor (ANF), and other neurohormonal variables were studied in 11 patients with normal hemodynamics with the patients in a supine -15 degree left decubitus posture by infusing 750 ml of normal saline solution over 30 minutes. Right and left atrial areas were measured by two-dimensional echocardiography. Plasma ANF level was sampled simultaneously from the pulmonary artery, aorta, and femoral artery and vein. At 30 minutes into the infusion, pulmonary capillary wedge pressure and right atrial pressure increased from 5.6 .+-. 2.8 mm Hg (mean .+-. SD) and 6.4 .+-. 2.2 mm Hg to 10.2 .+-. 3.2 and 9.5 .+-. 2.2 mm Hg, respectively (both p < 0.01). Left atrial area increased from 12.6 .+-. 2.2 cm2 to 15.0 .+-. 2.1 cm2 (p < 0.05), whereas right atrial area did not change. Plasma ANF levels from all sampling sites increased significantly (e.g., 43 .+-. 21 pg/ml to 71 .+-. 62 pg/ml in the femoral artery, p < 0.05). Plasma norepinephrine and renin levels were unchanged, whereas aldosterone level declined significantly. At 30 minutes after termination of the infusion, atrial pressures declined to baseline values in all patients. However, left atrial area remained significantly increased, and a trend for systemic arterial plasma ANF level to remain increased was seen. Plasma aldosterone level remained significantly suppressed. Thus, in some patients, a dichotomy exists in changes in atrial pressures versus atrial dimensions and plasma ANF levels during and after volume loading; this suggests that atrial stretch rather than pressure is the predominant stimulus for ANF secretion, thereby providing a potential explanation for prolonged ANF release after a volume load.