These results show a reduced ability to excrete a sodium load and early abnormalities of cardiac and hemodynamic adaptations to salt excess in patients with mild heart failure and no signs or symptoms of congestion.

We conclude that pretreatment with the ACE inhibitor quinapril significantly improves compromised responses to acute isotonic volume overload in patients with dilated cardiomyopathy and mild heart failure. The favorable influence of ACE inhibition on cardiovascular and hormonal responses to volume expansion seems to be related to the cardiac unloading produced by this treatment.

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The effects of endogenous activation of sympathetic nervous system on systemic and regional hemodynamics and on plasma levels of atrial natriuretic factor (ANF) were studied in subjects with essential hypertension. Stimulation of sympathetic nervous system was reflex-induced by a selective deactivation of carotid baroreceptors obtained by increasing external neck-tissue pressure (NTP) by means of a neck chamber. The effects of graded levels ( + 30, + 45, and + 60 mm Hg) and one single and sustained level ( + 45 mm Hg for 15 min) of NTP were studied. As expected, NTP caused reflex increases in blood pressure, heart rate, and forearm vascular resistance, whereas atrial pressures did not change significantly and cardiac output tended to increase. In the studies based on graded levels of NTP, immunoreactive ANF (irANF) progressively fell (from 31.7 + 10 to 13.3 + 4 fmol/ml; p < .05) and the changes in irANF were significantly correlated with those observed in FVR (r = -.671, p < .001). Both hemodynamic and irANF changes were prevented by adrenergic blockade (phentolamine + propranolol). During + 45 mm Hg NTP for 15 min, the levels of irANF fell both in the pulmonary artery and in the inferior vena cava. The irANF arteriovenous difference also fell during this maneuver. These data show that, in hypertensive patients, factors other than atrial wall tension may influence ANF release. They also show that endogenous sympathetic activation may reduce ANF release. Circulation 77, No. 5, 997-1002, 1988 A LARGE body of evidence indicates that the degree of atrial stretch or wall tension is a predominant factor in the regulation or atrial natriuretic factor (ANF) release in isolated heart preparations, 1, 2 intact animals,3 and human subjects.

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