Identification of normal neurohormonal activity in mild congestive heart failure and stimulating effect of upright posture and diuretics.

To characterize further the pathophysiology of the neurohormonal vasoconstrictor pathways in congestive heart failure (CHF), plasma renin activity, plasma norepinephrine, blood pressure, blood volume and renal hemodynamics were measured in 12 patients with mild to moderate CHF. In addition, the response to the gravitational stress of head-up tilt and the influence of 3 weeks of furosemide treatment as stimuli of neurohormonal activity were assessed. Supine plasma renin activity before diuretics was relatively normal at 1.94 +/- 1.6 ng/ml/hr and was significantly increased to 3.9 +/- 2.7 ng/ml/hr after diuretics. During tilt, there was a significant reflex increase in plasma renin activity both before and after diuretics. Plasma norepinephrine was also relatively normal before diuretics (325 +/- 211 pg/ml), did not increase after diuretics, but showed significant increases during tilt both before and after diuretics. Diuretic administration led to decreases in both systolic and diastolic blood pressures, but there was no change in body weight or total blood volume. In addition, diuretic administration did not result in any significant changes of renal blood flow (546 +/- 119 to 634 +/- 204 ml/min/1.73m2), glomerular filtration rate (81 +/- 22 to 90 +/- 27 ml/min/1.73m2) or filtration fraction (0.26 to 0.25). The present study demonstrates that the renin-angiotensin system and the sympathetic nervous system were not activated in the early symptomatic stages of CHF and that baroreceptor stimulation of these pathways during head-up tilt was relatively preserved. Renin secretion increased during diuretic administration, suggesting that the macula densa signal for renin release was also preserved in patients with relatively mild CHF.