B-type natriuretic Peptide (BNP) is a cardiac hormone secreted from the cardiac myocytes in response to volume load. Plasma levels of BNP, as measured by immunoassay methods, are elevated in patients with heart diseases. However, the biological effects of BNP are blunted in heart failure and other cardiac conditions. Moreover, the peptide levels are also elevated in non cardiac conditions such as the neonatal period, sepsis and renal failure. Recent investigations suggest alteration of the peptide molecular structure in heart failure. These alterations may explain, at least partially, the reduced biological activities of BNP in heart failure.

Immunoreactive BNP and NT-proBNP have been identified in human urine. It has been suggested that urinary BNP correlates with plasma BNP, and may serve as a non-invasive measure for this cardiac marker. It is unclear what BNP fractions are cleared in the urine in health and disease.

The aim of the proposed studies is to elucidate precisely the molecular form of BNP in various disease and specific physiological states in plasma and urine of infants and children.

Inclusion Criteria:

1. Healthy newborn infants with normal pregnancy and delivery
2. Premature infants
3. Infants and children with heart disease who have NT-proBNP levels taken as part of cardiac evaluation

Exclusion Criteria:

1. Patients with non cardiac disease (renal, hepatic)
2. Patients with acute urinary disease or other acute non-cardiac diseases.

Normal newborn infants and premature babies. Infants and children with significant heart disease.