Sabrina Vecchiarino

Low-Dose C-Type Natriuretic Peptide Does Not Affect Cardiac and Renal Function in Humans

In experimental animals, C-type natriuretic peptide (CNP) has vasodilating, hypotensive, and natriuretic activities. The role of circulating CNP in the overall regulation of cardiac and renal function in humans is less defined, in both health and disease. We measured cardiac volumes, diastolic and systolic functions, systemic (Doppler echocardiography) and renal hemodynamics, intrarenal sodium handling (lithium clearance method), plasma and urinary cGMP, plasma renin concentration, and plasma aldosterone level in six healthy volunteers (mean age, 33+/-3 years) receiving CNP (2 and 4 pmol/kg per minute for 1 hour each) in a single-blind, placebo-controlled, random-order, crossover study. During CNP infusion, plasma CNP increased from 1.17+/-0.23 to 41.52+/-4.61 pmol/L (ie, 4- to 10-fold higher levels than those observed in disease states) without affecting plasma and urinary cGMP, cardiac volumes, dynamics of left and right heart filling, cardiac output, arterial pressure, renal hemodynamics, intrarenal sodium handling, sodium excretion, or plasma levels of renin and aldosterone. The finding that increments in plasma CNP within the pathophysiological range have no effects on systemic hemodynamics, renal function, or the renin-angiotensin system do not support the hypothesis that CNP may act as a circulating hormone in humans.

Effects of exercise on natriuretic peptides and cardiac function in man

We evaluated cardiac function and the plasma levels of atrial (ANP) and brain (BNP) natriuretic peptides during bicycle (B) and hand-grip (HG) exercises in eight healthy males. Each test was preceded by a control protocol in resting conditions. Left ventricular (LV) function (echocardiography) was evaluated during both exercises. Atrial function was assessed only during HG. Plasma ANP significantly increased during B (+236%) and HG (+77%), while there was a significant trend towards higher plasma BNP levels during B (+41%) and HG (+30%) than during the corresponding control tests. Plasma ANP correlated with heart rate in both tests, with left atrial volume, pulmonary vein flow systolic fraction and mitral flow E/A ratio in HG; BNP in both test correlated with LV dimensions and function. These data suggest that during exercise the cardiac release of ANP and BNP is differently regulated and related to changes in left atrial and LV function, respectively.

Autonomic Regulation of Heart Rate and QT Interval in Nonalcoholic Cirrhosis with Ascites

BACKGROUND/AIMS Autonomic neuropathy, as indicated by alterations in standard cardiovascular tests, is frequently encountered in cirrhosis. We investigated the autonomic modulation of the heart in nonalcoholic cirrhosis with ascites by evaluating the 24-hour heart rate variability (HRV), a powerful noninvasive tool to assess the sympathovagal balance of the heart. METHODS Low (LF) and high frequency (HF) components and their ratio, and time domain indexes of HRV were evaluated in 24-hour, daytime and nighttime periods in 12 patients and 12 healthy subjects, together with the conventional and dynamic QT interval. RESULTS Cirrhotic patients had values of the mean RR interval and frequency domain indexes in the whole 24-hour period similar to those of healthy subjects, despite higher than normal plasma norepinephrine levels. Patients also showed lower LF and higher HF values than controls during the day, a reduction in time domain indexes, and no circadian rhythm of frequency domain indexes. QT parameters were similar in the 2 groups, but patients had a blunted QT rhythm and a reduced QT variability. CONCLUSIONS Patients with nonalcoholic cirrhosis and ascites have an impaired autonomic regulation of the heart, which involves both the sympathetic and the parasympathetic branches of the autonomic nervous system.

Cardiovascular function in pregnancy: effects of posture

Objective To evaluate the cardiovascular response to active postural changes in pregnancy.