Atrial natriuretic peptide in patent ductus arteriosus

Discriminant Analysis of Main Prognostic Factors Associated with Hemodynamically Significant PDA: Apgar Score, Silverman-Anderson Score, and NT-Pro-BNP Level

Hemodynamically significant patent ductus arteriosus (hsPDA) in premature newborns is associated with a risk of PDA-related morbidities. Classification into risk groups may have a clinical utility in cases of suspected hsPDA to decrease the need for echocardiograms and unnecessary treatment. This prospective observational study included 99 premature newborns with extremely low body weight, who had an echocardiogram performed within the first three days of life. Discriminant analysis was utilized to find the best combination of prognostic factors for evaluation of hsPDA. We used binary logistic regression analysis to predict the relationship between parameters and hsPDA. The cohort's mean and standard deviation gestational age was 27.6 ± 2.55 weeks, the mean birth weight was 1015 ± 274 g. Forty-six (46.4%) infants had a PDA with a mean diameter of 2.78 mm. Median NT-pro-BNP levels were 17,600 pg/mL for infants with a PDA and 2773 pg/mL in the non-hsPDA group. The combination of prognostic factors of hsPDA in newborns of extremely low body weight on the third day of life was determined: NT-pro-BNP, Apgar score, Silverman-Anderson score (Se = 82%, Sp = 88%). A cut-off value of NT-pro-BNP of more than 8500 pg/mL can predict hsPDA (Se = 84%, Sp = 86%).

Defining "Haemodynamic Significance" of the Patent Ductus Arteriosus: Do We Have All the Answers?

Optimum management of the patent ductus arteriosus (PDA) in preterm infants remains one of the most debated topics within the field of neonatology. Despite numerous observational studies and over 60 randomized control trials, consensus on PDA management remains elusive. In order to make meaningful progress on the controversial issue of PDA management, several key factors must be thoroughly addressed; namely (1) accurate identification of infants at greatest risk of long-term morbidities from PDA exposure, (2) acceptance that the PDA is not a dichotomous entity and an individualised approach to its management is required for each neonate, (3) international consensus on what constitutes a haemodynamically significant PDA and (4) the incorporation of multi-organ assessment when evaluating the impact a PDA may pose on overall neonatal physiology. This review assesses the evidence base available supporting various therapeutic strategies for PDA, the deficits in our current knowledge on the definition of haemodynamic significance and future directions to pursue in order to more successfully address this contentious subject.

Novel drug targets for ductus arteriosus manipulation: Looking beyond prostaglandins

Forty years ago, non-steroidal anti-inflammatory drugs were first reported to decrease systemic prostaglandin levels and promote ductus arteriosus (DA) closure. And yet, prolonged patency of the DA (PDA) remains a significant clinical problem, complicated by imperfect therapies and wide variations in treatment strategy. There are few pharmacology-based tools available for treating PDA (indomethacin, ibuprofen, and acetaminophen), or for maintaining DA patency (PGE₁) as is needed to facilitate corrective surgery for ductus-dependent congenital heart defects. Unfortunately, all of these treatments are inefficient and are associated with concerning adverse effects. This review highlights novel potential DA drug targets that may expand our therapeutic repertoire beyond the prostaglandin pathway.

Cardiovascular biomarkers pro-atrial natriuretic peptide and pro-endothelin-1 to monitor ductus arteriosus evolution in very preterm infants

BACKGROUND

The diagnostic and prognostic appraisal of patent ductus arteriosus (PDA) in preterm infants is still debatable.

AIMS

To compare plasma cardiovascular biomarkers with echocardiographic indices alongside ductus arteriosus (DA) evolution in very preterm infants within the first week of life.

METHODS

Mid-regional pro-atrial natriuretic peptide (MR-proANP) and C-terminal pro-endothelin-1 (CT-proET-1) levels were prospectively measured on the second and sixth days of life (DOL) in 52 preterm infants born before 32weeks of gestation. Echocardiographic indices to define DA patency and significance were simultaneously obtained. Logistic regression and receiver operating characteristics (ROC) analyses were used to assess and quantify the biomarkers' diagnostic capacities.

RESULTS

Thirty infants exhibited PDA on DOL 2; in 21 of these infants, DA was characterized as hemodynamically significant. Treatment failure after a first course of indomethacin was noted in 8 infants (DOL 6), whereas 7 participants underwent later surgical ligation. The diagnostic accuracy of cardiovascular biomarkers was moderate on DOL 2 but high on DOL 6. PDA was the only significant predictor of MR-proANP levels on DOL 6, independent of the effect of clinical confounders (regression coefficient 0.426, R(2) 0.60). Infants with MR-proANP ≥850pmol/l on DOL 2 had 3.9-fold higher risk (95% CI 1.01 to 14.5) of being diagnosed with significant DA, whereas infants with MR-proANP ≥700pmol/l on DOL 6 had 7.1-fold higher risk (1.9 to 27.2) for pharmaceutical treatment failure.

CONCLUSION

The cardiovascular plasma biomarker MR-proANP is a promising candidate for monitoring PDA evolution in very preterm infants.

Clinical implication of plasma natriuretic peptides in children with ventricular septal defect

BACKGROUND

There is little information available concerning plasma concentrations of B-type natriuretic peptide (BNP) in children with a ventricular septal defect. The aim of the present study was to determine hemodynamic factors that control plasma concentrations of BNP and the clinical implications of BNP compared with atrial natriuretic peptide (ANP) in children with ventricular septal defect.

METHODS

Fifty-nine patients with ventricular septal defect (28 boys and 31 girls) without pulmonary vascular disease were enrolled. The patients' ages ranged from 3 months to 13 years (mean 3.1 years). Plasma BNP and ANP were determined by immunoradiometric assay. Hemodynamic variables derived from cardiac catheterization were analyzed in terms of correlation with BNP and ANP.

RESULTS

It was found that plasma BNP significantly positively correlated with ANP (ANP = 2.1 x BNP + 25 pg/mL; r = 0.81, P < 0.0001) and BNP never exceeded ANP in the present patient series. Plasma BNP as well as ANP significantly positively correlated with pulmonary to systemic flow ratio (r = 0.65 and r = 0.59, respectively) and mean pulmonary artery pressure (r = 0.72 and r = 0.68, respectively). In addition, plasma BNP of > or =20 pg/mL and ANP of > or =50 pg/mL identified children with mean pulmonary artery pressure of > or =20 mmHg with a sensitivity of 82% and 97%, respectively, and a specificity of 89% and 84%, respectively.

CONCLUSION

Plasma BNP and ANP reflect pressure and volume loads to the pulmonary artery and right ventricle and may help to identify children with ventricular septal defect complicated by pulmonary hypertension that demands early intervention.

Atrial natriuretic factor in amniotic fluid and in maternal venous blood of pregnancies with fetal cardiac malformations and chromosomal abnormalities

OBJECTIVE

We evaluated the levels of atrial natriuretic factor (ANF) in amniotic fluid and in maternal venous blood in pregnancies with fetal cardiac malformations and chromosomal abnormalities.

METHOD

Between the 16th and 18th week of pregnancy, 151 women were divided into three groups. Group A included patients at lowest risk, carrying a fetus with a normally developing heart and normal karyotype (control group). Group B included women with a fetus suffering from cardiac malformations, with or without associated chromosomal abnormalities. Group C included women carrying a fetus affected with chromosomal abnormalities without congenital cardiopathies. ANF was evaluated by radioimmunoassay.

RESULTS

In maternal venous blood, the mean levels of ANF were 42.1, 53.1 and 38.7 pg/ml in groups A, B and C, respectively. In amniotic fluid, the mean levels of ANF were 34.2, 101.8 and 35.8 pg/ml in groups A, B and C, respectively. In group A (control group) there was no statistical difference in ANF levels across the gestational age range of 16-18 weeks, either in amniotic fluid or in maternal venous blood. A significant difference of ANF content in maternal venous blood was revealed in comparing group A with group B (p < 0.01), and group C with group B (p < 0.01). A statistically significant difference in ANF levels was also found in amniotic fluid between group A and group B (p < 0.01), and between group C and group B (p < 0.01). No statistically significant differences were found between group C and group A in comparing ANF levels in maternal venous blood and amniotic fluid.

CONCLUSION

ANF levels in amniotic fluid and in maternal venous blood are increased early in the case of fetuses with cardiac malformations, with or without associated karyotype alteration. Chromosomally abnormal fetuses without heart malformations have normal ANF levels. These results could be useful for elucidating fetal pathophysiology mechanisms.

Peri-operative changes in echocardiographic measurements and plasma atrial and brain natriuretic peptide concentrations in 3 dogs with patent ductus arteriosus

Peri-operative changes in echocardiographic measurements and plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were investigated for 1 month in 3 dogs with patent ductus arteriosus (PDA). Post-operative left ventricular end-diastolic dimention and fractional shortening decreased in all cases. Pre-operatively increased plasma ANP concentrations reduced dramatically after the operation. Peri-operative changes in plasma BNP levels had slightly S-shaped curves in all cases. These observations suggest that post-operative responsiveness of ANP and cardiac function are rapid in comparison with cardiac morphological changes, and BNP has a different pathophysiological significance from ANP in dogs with PDA.

Atrial natriuretic peptide in the preterm infant. Lack of correlation with natriuresis and diuresis

We assessed the relation of atrial natriuretic peptide (ANP) to renal function on postnatal day 2 and day 5 in preterm infants. Plasma ANP concentration was measured by radioimmunoassay in two groups of preterm infants: group 1, gestational age less than 30 weeks, n = 10; and group 2, gestational age 30-34 weeks, n = 11. The identity of the immunoreactivity as ANP-28 was confirmed by HPLC. Plasma ANP was significantly higher in group 1 than in group 2 on day 2 and day 5 (p < 0.01) and ANP concentration decreased by day 5 in both groups (group 1, p < 0.01; group 2, p < 0.02). The results showed no correlation between plasma ANP concentration and urinary sodium excretion or creatinine clearance, which may be due to a blunted renal response to ANP, but other factors may be involved also. We conclude that preterm infants are able to release large amounts of ANP, but a high plasma ANP concentration does not correlate directly with renal regulation of sodium and water balance.

Atrial natriuretic peptide in the diagnosis of patent ductus arteriosus

The aim of this study was to measure plasma atrial natriuretic peptide in preterm infants with a patent ductus arteriosus before and after closure with indomethacin. Atrial natriuretic peptide was measured in 28 preterm infants with clinical and echocardiographic evidence of a patent ductus arteriosus and in eight preterm infants who did not develop clinical evidence of a patent ductus arteriosus. Plasma concentration of atrial natriuretic peptide was measured by radioimmunoassay. In 18 infants the patent ductus arteriosus closed after one course of indomethacin; atrial natriuretic peptide levels decreased from median 1240 pg/ml (range 201-5483 pg/ml) to 266 pg/ml (range 62-1108 pg/ml). In four infants the patent ductus arteriosus closed after two courses of indomethacin and two infants had surgical ligation after indomethacin treatment failed. The patent ductus arteriosus closed spontaneously in four infants (atrial natriuretic peptide median level 152 pg/ml, range 61-495 pg/ml). In the eight infants without patent ductus arteriosus, atrial natriuretic peptide level was median 224 pg/ml (range 38-876 pg/ml). Measurement of plasma atrial natriuretic peptide concentration has a role in predicting when indomethacin treatment is indicated.

Atrial natriuretic peptide and blood volume during red cell transfusion in preterm infants

Because raised plasma concentrations of atrial natriuretic peptide indicate volume expansion, we studied the effect of red cell transfusion on plasma atrial natriuretic peptide concentration, packed cell volume, and intravascular volume in eight preterm infants. Red cell transfusion increased red cell mass, packed cell volume and erythrocyte count, but decreased plasma volume. Total blood volume, plasma atrial natriuretic peptide concentration, urine flow rate, and urinary sodium excretion did not change. We conclude that a slow transfusion of less than 10 ml red cells/kg body weight does not cause volume expansion with subsequent atrial natriuretic peptide release thereby affecting the cardiovascular system.

Atrial natriuretic factor in patients with congenital heart disease: correlation with hemodynamic variables

To investigate the alpha-atrial natriuretic factor in congenital cardiac malformations, three groups of children, aged 7 months to 16 years, with different hemodynamic situations were studied during routine cardiac catheterization. Twenty-one (group I) had tetralogy of Fallot, 24 (group II) had a left to right shunt with pulmonary hypertension and 12 (control group) had a minor cardiac lesion. Alpha-atrial natriuretic factor levels were determined by a radioimmunoassay on blood samples from the inferior vena cava, right atrium, pulmonary artery, left atrium and aorta. To evaluate the effect of an acute volume load, measurements of hormone and pressures were repeated after right ventriculography. Alpha-atrial natriuretic factor levels varied over a wide range in all groups and in all chambers investigated. Nevertheless, children with pulmonary hypertension had significantly higher levels of the hormone (p less than 0.01) and were well separated from the control group, but less well from those with tetralogy of Fallot. A 50% increase of alpha-atrial natriuretic factor from the inferior vena cava to the right atrium occurred in patients with shunt lesions with pulmonary hypertension and in patients with tetralogy of Fallot (p less than 0.001) and a further 30% increase from the right atrium to the pulmonary artery (p less than 0.05). After right ventriculography, a 100% to 200% increase of alpha-atrial natriuretic factor was observed in the total sample (p less than 0.001). A positive correlation was observed between right atrial mean pressure and right atrial alpha-atrial natriuretic factor (r = 0.63) and between pulmonary artery mean pressure and pulmonary artery alpha-atrial natriuretic factor (r = 0.61).(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationship of atrial natriuretic peptide, atrial volume, and renal function in premature infants

Infants experience dramatic changes in fluid balance during the first few days of life, which provides an opportunity to observe the interrelationships of changing atrial size, atrial natriuretic peptide (ANP) secretion, and renal function during a relatively short period. To study these relationships, we examined nine infant boys (mean birth weight 1180 gm and gestational age 30 weeks) at 20 to 28 hours of age and then at four 24-hour intervals. Measurements included plasma ANP concentration, two-dimensional echocardiographic estimations of left and right atrial volumes, Doppler determination of ductus arteriosus patency, creatinine clearance, urine flow rate, urinary sodium excretion, and cyclic guanosine monophosphate (cGMP) excretion. Plasma ANP concentration was found to decrease with age and to correlate with decreasing size of the right atrium, closure of the ductus arteriosus, urinary cGMP excretion, and sodium excretion. We speculate that elevated plasma ANP values in a preterm neonate reflect an expanded volume state. As volume contraction, reflected by decreasing atrial volume and body weight occurs, ANP levels decrease, which may diminish diuresis. These findings are compatible with a significant role for ANP in volume homeostasis of newborn infants.

The physiological and biological significances of human atrial natriuretic peptide in neonates

The purpose of our study was to analyze the physiological and biological significances of the high human atrial natriuretic peptide (hANP) levels during early post-natal period. The absolute values or changes of plasma hANP concentrations did not correlate with the absolute values or changes of body weight, blood pressure, urinary sodium/creatinine and urinary aldosterone/creatinine ratios. Gel permeation chromatography of samples from two neonates revealed the presence of two molecular forms of hANP, alpha and beta, both in the plasma and urine. In the plasma, the beta-hANP was predominant on the 3rd day of life and the alpha-hANP on the 6th day of life. The change from one form to another was independent of the absolute value of hANP. We obtained no evidence suggestive of a physiological role of the high plasma hANP concentration during the early post-natal period. However, because of biological differences between these two fractions, their distribution must be taken into account when attempting to interpret the high hANP values observed in neonates.

Endocrine control of electrolyte balance during development

The endocrine control of electrolyte balance during development is reviewed. It is suggested that the high urinary sodium excretion observed in premature infants may be secondary to the immaturity of the adrenal gland to adequately increase the secretion of aldosterone (Sulyok et al, 1979b), and to the inability of the distal tubule to respond appropriately to a rise in circulating aldosterone levels (Sulyok et al, 1979a). On the other hand, the elevated plasma aldosterone levels observed in term newborn infants may play an important role in the blunted response of the newborn kidney to saline loading (Sulyok et al, 1979a; Spitzer, 1982). The ability of ANP to induce a natriuresis and to contribute to fluid and electrolyte homeostasis during development has been investigated. It has been found that the immature kidney is less responsive to ANP than later in life (Chevalier et al, 1988; Robillard et al, 1988). On the other hand, it has been suggested that a rise in plasma ANP during the first five days of life may contribute to the physiological weight loss associated with the extracellular volume contraction occurring shortly after birth (Tulassay et al, 1987). The role of glucocorticoids, prostaglandins and the kallikrein-kinin system in regulating electrolyte balance during development is also reviewed.

Relationship between plasma atrial natriuretic peptide concentrations and cardio-thoracic ratio during the early neonatal period

Twenty-seven neonates were examined at 2.6 +/- 1.5 hours of age (stage 1) and 21 +/- 4.9 hours of age (stage 2) to clarify the relationship between cardio-thoracic ratio (CTR) on chest roentgenograms and plasma atrial natriuretic peptide (ANP) concentration. Among 22 infants who showed elevated plasma ANP, 14 had gained body weight (group A), while 8 other infants had lost weight (group B) at stage 2. The remaining 5 infants had decreased plasma ANP concentrations combined with weight loss at stage 2 (group C). All infants of group B had a patent ductus arteriosus. The plasma ANP concentration and CTR of groups A and B increased during the study period, while those of group C decreased. A linear relation was found between plasma ANP concentration and CTR in all cases (p less than 0.02). This study indicates that increased plasma levels of ANP are associated with an increased CTR.

Rapid reduction of plasma atrial natriuretic peptide levels during percutaneous transvenous mitral commissurotomy in patients with mitral stenosis

To clarify the direct contribution of the left atrial pressure to secretion of human atrial natriuretic peptide (hANP), we have attempted to study the relations between plasma hANP levels, neurohumoral factors, and hemodynamic changes in 13 patients with mitral stenosis undergoing percutaneous transvenous mitral commissurotomy (PTMC). After PTMC, the left atrial pressure fell from 14.7 +/- 1.9 (mean +/- SEM) to 6.5 +/- 0.7 mm Hg in all patients studied (p less than 0.0005), whereas there were no remarkable changes in either the right atrial pressure, mean arterial pressure, or heart rate. Plasma immunoreactive hANP levels obtained from the pulmonary artery decreased from 278 +/- 51 to 137 +/- 31 pg/ml after PTMC (p less than 0.0005). There was a significant correlation between the decrement of hANP levels and that of left atrial pressure (r = 0.72, p less than 0.005). Neither plasma renin activity nor norepinephrine levels changed. In contrast, plasma aldosterone concentrations significantly increased from 11.3 +/- 1.5 to 16.4 +/- 2.7 pg/ml after PTMC (p less than 0.01), although there was no casual relation between plasma concentrations of aldosterone and hANP. The present result with PTMC-induced rapid fall of the left atrial pressure with a concomitant reduction in hANP secretion strongly suggests the importance of the left atrial pressure on hANP secretion in humans.

Experimental ductus arteriosus: the relationships of atrial pressure, dilatation and flow with ANF secretion

The design of the study was to determine whether an increased blood flow as seen in shunt lesions could serve as a stimulus for the secretion of atrial natriuretic factor (ANF). Since atrial pressure, flow, and dilatation are closely related, an experimental ductus arteriosus model was utilized, in which acute changes of flow are assumed not to dilate the left atrium. In six dogs, a Dacron graft was constructed between the main pulmonary artery and the innominate artery. Constricting and releasing the tape around the graft adjusted the amount of "ductal" shunting. The total pulmonary flow and the shunt flow were measured by electromagnetic-flow transducers around the aortic root and around the graft. Plasma ANF concentration was measured from both cardiac atria. The size of the left atrium was determined from echocardiographic measurements made from a short-axis view. The total pulmonary flow varied between 1.2 and 5.8 1/min. The highest measured ANF was 396 pg/ml, and this was from the left atrium when the pressure was 18 mmHg, the highest left atrial pressure recorded. The highest right atrial pressure (5 mmHg) also correlated with the highest right-atrial level of ANF (366 pg/ml). The right atrial pressure had a significant correlation with plasma ANF concentration (R = 0.43, p less than 0.05). Pulmonary flow and plasma ANF concentration did not correlate; neither did left atrial size and ANF levels in 16 flow states where the size was measured. In the absence of atrial dilatation there was minimal stimulus for ANF secretion. A transient increase of left atrial pressure, without a concomitant significant atrial dilatation, did not serve as a significant stimulus for ANF secretion.

Atrial natriuretic peptide in congestive heart failure

Release of atrial natriuretic peptide (ANP) appears to be a compensatory response in congestive heart failure (CHF) that may counterbalance the adverse effects of stimulated renin-angiotensin and sympathetic nervous systems. We observed increased plasma ANP concentrations in CHF patients in New York Heart Association functional classes II to IV. The fact that such responses already become evident when a patient is in New York Heart Association class II supports the concept that ANP release may counteract the detrimental effects of stimulation of renin and the sympathetic nervous system even in the early phases of heart failure by promoting diuresis and natriuresis, as well as vasodilatation, thus reducing both pre- and afterload. When CHF is severe, however, the counterbalancing effects of ANP may be offset by vasoconstriction and fluid and sodium retention.

Atrial natriuretic peptide and atrial pressures in newborns with transposition of the great arteries

The relation of atrial pressure to atrial plasma concentration of atrial natriuretic peptide (ANP) was studied in four newborns undergoing catheterization because of transposition of the great arteries. In three patients, mean left atrial pressure clearly exceeded right atrial pressure (12 +/- 7 vs. 2 +/- 3 mmHg; mean +/- SD). In one patient mean atrial pressures were identical (4 mmHg). In all patients the ANP concentration in the left atrium exceeded that of the right (833 +/- 464 vs. 415 +/- 366 pg/ml; mean +/- SD). There was a significant (r = 0.97; p less than 0.01) correlation between pressure and ANP concentration in the left atria. In the right atria, no linear correlation existed between pressure and ANP concentration. ANP concentration in the left atrium decreased after a lowering of the left atrial pressure by atrial septostomy. In these patients, the left atrium seems to be the main source of circulating ANP.